JP4371999B2 - Dry etching method and dry etching apparatus - Google Patents

Description

  The present invention relates to a dry etching method and a dry etching apparatus. Specifically, the present invention relates to a method and apparatus for dry etching a processing object made of a silicon-based material.

In dry etching in which holes such as trenches and via holes are formed in a processing object made of a silicon-based material, SiO ₂ (silicon oxide) -based deposits, which are reaction products during etching, are exposed on the surface to be etched. In some cases, a black silicon phenomenon (hereinafter simply referred to as “black silicon”) that accumulates and becomes an etching residue may occur. Patent Document 1 describes the generation principle of this black silicon. Black silicon causes generation of particles in the subsequent process, contamination in the chamber, stop of dry etching, and the like, and decreases the product yield.

Referring to FIGS. 18A and 18B, black silicon in the case of dry etching a substrate made of a silicon-based material using an SF ₆ / O ₂ / He (sulfur hexafluoride / oxygen / helium) -based etching gas. Outline the generation principle. A resist mask 2 is formed on a substrate 1 made of a silicon-based material (for example, Si).

As shown in FIG. 18A, the F component, F radical, O component, and He component generated by the plasma are incident on a portion of the substrate 1 exposed from the resist mask 2. The substrate 1 is etched by F radical positive ions (S ions, O ions, etc.) that are etching species, He components, and the like. At this time, F radicals react with Si atoms of the substrate 1 to generate volatile reaction products, such as SiF ₄ (silicon tetrafluoride) and SiF ₆ (silicon hexafluoride), which are detached from the etching target layer 2. . Further, the O component reacts with Si atoms of the substrate 1 to generate SiO ₂ (silicon oxide). This SiO ₂ adheres to the side walls of the grooves and holes to form the side wall protective layer 3. However, depending on the process conditions, as shown in FIG. 18B, a SiO ₂ (silicon oxide) -based reaction product is deposited on the surface to be etched, and the deposit 4 generates black silicon.

Japanese Patent Laid-Open No. 10-233387

  An object of the present invention is to monitor the generation and signs of black silicon in dry etching of a substrate made of a silicon-based material, and to prevent the generation of black silicon.

According to a first aspect of the present invention, there is provided a dry etching method for a substrate made of a silicon-based material, wherein an image of a surface to be etched of the substrate being processed is obtained by dry etching, and the image is obtained based on the acquired image. Provided is a dry etching method for calculating a measurement brightness, which is a brightness of a predetermined measurement position on a surface to be etched of a substrate, and monitoring generation of black silicon or an indication thereof based on the measurement brightness .

  Based on the image of the surface to be etched of the substrate during dry etching, it is possible to monitor the occurrence or sign of black silicon in real time and with high accuracy. Here, the surface to be etched is the bottom of a recess such as a trench or a hole processed by dry etching. Examples of the silicon-based material constituting the substrate include Si (single crystal silicon), poly-Si (polysilicon), a-Si (amorphous silicon), WSi (tungsten silicide), MoSi (molybdenum silicide), and TiSi (titanium). Silicide) and the like.

In concrete terms, the comparing and measuring brightness, and reference brightness is the brightness of the measurement points corresponding to the time elapsed from the dry etching start when the black silicon is not generated, black on the basis of the result of the comparison Determine whether silicon is present or any signs of it.

  In particular, when detecting a sign of black silicon generation, it is determined that a sign of black silicon generation has occurred when the measured lightness is equal to or less than a first predetermined ratio with respect to the reference lightness.

  Alternatively, when the measured brightness is equal to or less than a first brightness difference determined in advance from the reference brightness, it is determined that a sign of black silicon is generated.

  Even when detection of a sign of black silicon generation is detected, black silicon generation can be prevented by changing dry etching conditions.

  For example, when an indication of the occurrence of black silicon is detected, the bias voltage applied to the lower electrode on which the substrate is placed is increased.

  Moreover, when the sign of the generation of the black silicon is detected, the pressure in the vacuum vessel in which the substrate is accommodated may be reduced.

Further, when an etching gas containing at least SF ₆ , O 2 and He is used, the content of O _{2 in} the etching gas may be reduced when the sign of the generation of black silicon is detected.

  If a sign of the occurrence of black silicon is detected instead of or together with the change in the dry etching condition, it may be notified.

When detecting black silicon generation rather than a sign of black silicon generation,
When the measured lightness is equal to or less than a second predetermined ratio with respect to the reference lightness, it is determined that black silicon is generated.

  Alternatively, it is determined that black silicon is generated when the measured lightness is equal to or less than a second lightness difference determined in advance from the reference lightness.

  When black silicon is actually generated, the measured brightness is greatly reduced as compared to the case where there is merely a sign of black silicon generation. Accordingly, the second ratio for determining whether black silicon is generated is smaller than the first ratio for determining whether black silicon is generated. Further, the second brightness difference for determining the presence or absence of black silicon generation is larger than the first brightness difference for determining the presence or absence of the black silicon generation sign.

  When black silicon generation is detected, it is preferable to stop dry etching. Further, when black silicon generation is detected, it may be notified.

  As an alternative to detecting the occurrence of black silicon, the measured brightness is compared with the determination brightness, which is the brightness of the measurement location corresponding to the passage of time from the start of dry etching when black silicon is generated. The presence or absence of black silicon generation is determined based on the result.

  Specifically, when the measured brightness is equal to or lower than the determined brightness, it is determined that black silicon is generated.

  Even when the determination brightness is used, it is preferable to stop dry etching when black silicon generation is detected. Further, when black silicon generation is detected, it may be notified.

According to a second aspect of the present invention, a vacuum vessel in which a substrate made of a silicon-based material is disposed, a plasma source that generates plasma in the vacuum vessel, and plasma is generated in the vacuum vessel by the plasma source And an imaging device that acquires an image of the etched surface of the substrate being processed by dry etching, and a monitoring unit that monitors the occurrence of black silicon or its sign based on the image acquired by the imaging device. The monitoring unit includes a lightness detection unit that calculates a measurement lightness that is a lightness of a predetermined measurement location on the etching target surface of the substrate based on an image acquired by the imaging device, and the measurement lightness Based on this, a dry etching apparatus for monitoring the occurrence of black silicon or its signs is provided.

  Based on the image of the surface to be etched of the substrate during dry etching, it is possible to monitor the occurrence or sign of black silicon in real time and with high accuracy.

  Further, the monitoring unit includes a reference lightness storage unit that stores a reference lightness that is the lightness of the measurement location corresponding to the passage of time from the start of dry etching when black silicon is not generated, and the measurement calculated by the lightness detection unit. A first comparison unit that compares the lightness with the reference lightness stored in the reference lightness storage unit, and a first determination unit that determines whether or not there is an indication of black silicon generation based on a comparison result of the first comparison unit And a determination unit.

  For example, when the measured lightness is equal to or lower than a predetermined ratio with respect to the reference lightness, the first determination unit determines that a sign of black silicon is generated. Further, the first determination unit may determine that a sign of black silicon is generated when the measured brightness is equal to or less than a predetermined brightness difference with respect to the reference brightness.

  When the determination unit determines that the sign of the occurrence of black silicon is occurring, the apparatus may further include an apparatus control unit that changes dry etching conditions. By appropriately changing the dry etching conditions by the apparatus control unit, the generation of black silicon can be prevented even when black silicon signs are detected. When the determination unit determines that the sign of the occurrence of black silicon has occurred, the operator may be notified that the sign of the occurrence of black silicon has occurred by turning on a warning light, and display that fact on the display unit. May be.

  Alternatively, the monitoring unit includes a reference lightness storage unit that stores a reference lightness that is the lightness of the measurement location corresponding to the passage of time from the start of dry etching when black silicon is not generated, and the measurement calculated by the lightness detection unit. A first comparison unit that compares the lightness with the reference lightness stored in the reference lightness storage unit, and a second determination unit that determines whether black silicon is generated based on a comparison result of the first comparison unit With.

  In addition, the monitoring unit includes a black silicon determination lightness storage unit that stores a determination lightness that is the lightness of the measurement location corresponding to the passage of time from the start of dry etching when black silicon is generated, and the lightness detection unit A second comparison unit that compares the measured lightness calculated by and a determination lightness stored in the black silicon determination lightness storage unit, and determines whether black silicon is generated based on a comparison result of the second comparison unit And a third determination unit that performs the above operation.

  According to the method and apparatus of the present invention, an image of a surface to be etched of a substrate made of a silicon-based material being processed is obtained by dry etching, and black silicon is generated and its sign in real time and with high accuracy based on the image. Can be monitored. Further, when a sign of black silicon generation is detected, the generation of black silicon can be prevented by appropriately changing the dry etching conditions.

  Next, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

(First embodiment)
1 to 4 show an inductively coupled dry etching apparatus 11 according to a first embodiment of the present invention. The dry etching apparatus 11 includes a chamber or a vacuum container 12. In addition to the bottom wall 13 and the side wall 14, the vacuum container 12 includes a top wall 16 that closes the internal space 15 of the vacuum container 12 so that it can be opened and closed. The substrate 1 which is a processed material is accommodated in the internal space 15 of the vacuum vessel 12. Referring to FIG. 6, a resist mask 2 is formed in a predetermined pattern on the upper surface of the substrate 1. The material of the substrate 1 is a silicon-based material. Silicon-based materials include Si (single crystal silicon), poly-Si (polysilicon), a-Si (amorphous silicon), WSi (tungsten silicide), MoSi (molybdenum silicide), and TiSi (titanium silicide). .

  On the bottom wall 13 side of the internal space 15, a placement stage 21 that supports the substrate 1 so as to be releasable is disposed. The mounting stage 21 includes a lower electrode 22, and the substrate 1 is mounted on the upper surface of the lower electrode 22. The lower electrode 22 is electrically connected to a bias power source 23. The bias power source 23 includes a high-frequency AC power source 23a and a matching circuit 23b for impedance adjustment.

  A gas inlet 24 provided in the vacuum vessel 12 is provided with an MFC (mass flow controller) or the like, and a gas supply unit 25 that supplies an etching gas to the internal space 15 of the vacuum vessel 12 at a desired flow rate is connected. Further, a pressure reducing unit 28 including a valve, a TMP (turbo molecular pump), a vacuum pump (for example, a rotary pump or a dry pump) is connected to the exhaust port 27 provided in the vacuum vessel 12.

  In the present embodiment, the top wall 16 includes a dielectric plate (plate body) 29 made of quartz. The dielectric plate 29 is partially provided with a transparent portion, that is, a transparent portion 30 in the thickness direction. As shown most clearly in FIG. 3, the transparent portion 30 is an upper polishing formed by polishing (lapping) a part of the outer surface 29 a (surface opposite to the inner space 15) of the dielectric plate 29 into a circular shape. And a lower polishing portion 32 formed by similarly polishing a part of the inner surface 29b (surface on the inner space 15 side) of the dielectric plate 29 into a circular shape. The upper polishing portion 31 and the lower polishing portion 32 have substantially the same position and area in plan view. A disk-shaped window plate 34 made of sapphire is fixed to the lower polishing portion 32. The window plate 34 is fixed to the inner surface 29b of the dielectric plate 29 by, for example, a resin bolt (not shown). As will be described in detail later, the sapphire window plate 34 has a function of preventing a decrease in transparency or fogging of the transparent portion 30 caused by plasma generated during dry etching.

  An antenna for generating plasma or a coil 36 is accommodated in a casing 35 having an electromagnetic shielding function provided above the vacuum vessel 12. As shown in FIGS. 2 and 3, the coil 36 is formed by arranging a plurality of (four in this embodiment) strip-shaped conductors 37 in a spiral shape. One end of each conductor 37 is electrically connected to the coil high frequency power supply 38, and the other end is grounded. The coil high-frequency power supply 38 includes a high-frequency AC power supply 38a and a matching circuit 38b for impedance adjustment.

  As shown most clearly in FIG. 2, the four conductors 37 forming the coil 36 are arranged so that a gap is formed between them in a plan view. In particular, four gaps 39A to 39D having a relatively large area are formed near the center of the coil 36 in plan view. The transparent portion 30 of the dielectric plate 29 described above is formed at a position corresponding to one gap 39A among the four gaps 39A to 39D.

  A casing 40 is further disposed on the casing 35 that houses the coil 36. Inside the casing 40, the above-described high-frequency power source for coil 38 is accommodated.

  As shown in FIGS. 1 and 3, a circular window hole 41 is formed in the upper wall 35 a of the casing 35 in a plan view. Similarly, a circular window hole 42 is formed in the upper wall 40a of the casing 40 in a plan view. The window holes 41 and 42 are formed at positions corresponding to the gaps 39 </ b> A of the coil 36 in plan view, like the transparent portion 30 of the dielectric plate 29 described above. Further, the window hole 42 is formed at a position that does not overlap with the coil high-frequency power source 38 in the casing 40 in plan view.

  As shown in FIGS. 1 and 2, an XY stage (moving mechanism) 46 on which a camera (imaging device) 45 is mounted is placed on the upper wall 40 a of the casing 40. Specifically, the XY stage 46 includes a Y-axis slider 46a that can move in the Y-axis direction, and a Y-axis drive motor 46b that drives a ball screw mechanism (not shown) that moves the Y-axis slider 46a. The XY stage 46 also has an X-axis slider 46c that can move in the X-axis direction on the Y-axis slider 46a, and an X-axis drive motor 46d that drives a ball screw mechanism (not shown) that moves the X-axis slider 46c. Is provided.

  The camera 45 is mounted on an X-axis slider 46c of the XY stage 46, and can be moved in the horizontal direction (X-axis direction and Y-axis direction) above the coil 36 by the XY stage 46. The camera 45 includes an image sensor such as a CCD type, and its field of view is vertically downward. The camera 45 includes a laser light source 47 for distance measurement. Furthermore, the camera 45 has various functions including adjustment functions such as magnification, focus, and sensitivity. An image captured by the camera 45 is output to the monitoring unit 57 of the control unit 55 described later. As long as images can be taken at sufficiently short time intervals, the camera 45 may be a video camera that can shoot moving images or a camera that can shoot still images.

  With reference to FIG. 3, the positional relationship among the transparent portion 30 of the dielectric plate 29, the coil 36, the window hole 41 of the casing 35, the window hole 42 of the casing 40, and the camera 45 will be described. As described above, the transparent portion 30, the window hole 41, and the window hole 42 are all provided at positions corresponding to the gap 39A of the coil 36 in plan view. Specifically, the transparent portion 30, the window hole 41, and the window hole 42 are positioned on a line L extending in the vertical direction indicated by a two-dot chain line in FIG. Further, the lower end of the vertical line L reaches the surface of the substrate 1 held on the mounting stage 21 as indicated by a point P. Therefore, when the inside of the dry etching apparatus 11 is viewed from the window hole 41 of the casing 35, the surface of the substrate 1 can be seen through the window hole 42 of the casing 40, the gap 39A of the coil 36, and the transparent portion 30 of the dielectric plate 29. . As described above, since the camera 45 can be moved in the horizontal direction by the XY stage 46, the position of the field of view coincides with the vertical line L, that is, the window hole 41, the window hole 42, the gap 39A of the coil 36, and the dielectric. The substrate 1 in the vacuum vessel 12 can be moved to a position where it can be accommodated in the field of view through the transparent portion 30 of the body plate 29.

  As shown in FIGS. 1 and 4, the dry etching apparatus 11 includes a display unit 49 including a liquid crystal display device, a warning lamp 50, and an operation input unit 51 for an operator to operate the apparatus.

  The dry etching apparatus 11 controls the operation of the entire apparatus including the gas supply unit 25, the decompression unit 28, the coil high frequency power supply 38, the bias power supply 23, the XY stage 46, the camera 45, the warning lamp 50, and the display unit 49. A control unit 55 is provided. Referring to FIG. 4, the control unit 55 includes an operation condition storage unit 56, a device control unit 54, and a monitoring unit 57. The operating condition storage unit 56 stores dry etching process conditions executed by the dry etching apparatus 11. The process conditions include various conditions such as a flow rate ratio of gases contained in the etching gas, a bias voltage applied to the lower electrode 22 from the bias power source 23, and a pressure in the vacuum vessel 12. In particular, in the present embodiment, the operation condition storage unit 56 stores a process condition when a sign of occurrence of black silicon is detected in addition to a normal process condition when the dry etching is appropriately progressing. . In accordance with an operator command input from the operation input unit 51 and the process conditions stored in the operation condition storage unit 56, the apparatus control unit 54 is configured to supply the gas supply unit 25, the decompression unit 28, the coil high-frequency power source 38, and the bias. The power source 23 is controlled to perform dry etching. In addition, the device control unit 54 controls the camera 45 and the XY stage 46.

  The monitoring unit 57 monitors the sign of black silicon generation based on the image captured by the camera 45. The monitoring unit 57 includes a brightness detection unit 61, a reference brightness storage unit 62, a comparison unit 63A, and a determination unit 64A.

  The brightness detection unit 61 detects the surface to be etched on the surface of the substrate 1 (the bottom of a recess such as a trench or a hole processed by dry etching) based on the image taken by the camera 45. Referring also to FIG. 6, among regions included in the field of view of the camera 45 on the surface of the substrate 1 conceptually indicated by reference numerals 67A and 67B, specific regions (target regions) 68A and 68B targeted for brightness detection are shown. Is set. The lightness detection unit 61 detects the lightness of the surface of the substrate 1 in the target areas 67A and 67B. The target region 68A includes only a portion on the surface of the substrate 1 where the resist mask 2 does not exist. On the other hand, the target region 68B partially includes the resist mask 2 in a part thereof. Either of the target areas 68A and 68B may be adopted, but in the following description, the target area 68A is used for brightness detection. The brightness detection unit 61 calculates the in-plane average brightness (measured average brightness Bdet) of the target region 68A from the image of the surface of the substrate 1 taken by the camera 45. In the present embodiment, the measured average brightness Bdet is represented by, for example, 256 gradations from 0 (darkest) to 255 (brightest).

The reference lightness storage unit 62 stores a reference lightness Bs (t) used for determining the presence or absence of a sign of black silicon generation in the target area 68A. FIG. 7 shows an example of the reference brightness Bs (t). The reference brightness Bs (t) is a change in the surface average brightness of the target area 68A with respect to the elapsed time (etching time) t from the start of etching when dry etching is completed without generating black silicon. In the example shown in FIG. 7, the reference brightness Bs (t) at the start of dry etching (t = 0) is 250, and the reference brightness Bs (t) at the end of dry etching (t = tmax) is 230. The reference brightness Bs (t) linearly decreases at a constant rate from the etching to the end of etching. The reference brightness Bs (t1) at the etching time t1 is 240, and the reference brightness Bs (tmax) at the etching end time tmax is 230. As shown in FIG. 8A, when there is no sign of black silicon generation, in the etching time t1, the trench 7 is formed to a depth d1 that is in a portion not covered with the resist mask 2 of the substrate 1. At the bottom of the trench 7, no SiO ₂ -based deposit that causes black silicon is deposited. As shown in FIG. 8B, when there is no sign of black silicon generation, at the etching time t2, the trench 7 is deepened to the depth d2, but no SiO ₂ -based deposit is deposited. Thus, if there is no sign of black silicon generation and no deposit is deposited at the bottom of the trench 7, the surface average brightness of the target region 68A is sufficiently bright. In the following description, the reference brightness Bs (t) shown in FIG. 7 is used, but the reference brightness Bs (t) is not limited to this. For example, the reference brightness Bs (t) may be a curve, a polygonal line, a staircase shape, or the like.

  The comparison unit (first comparison unit) 63A compares the measured average lightness Bdet calculated by the lightness detection unit 61 with the reference lightness Bs (t) stored in the reference lightness storage unit 62. Specifically, the comparison unit 63A compares the measured average brightness Bdet of the target area 68A at a certain time t with the reference brightness Bs (t) at the same time t. More specifically, the comparison unit 63A calculates the ratio of the measured average brightness Bdet to the reference brightness Bs (t) at the same time.

  The determination unit (first determination unit) 64A determines the presence or absence of a sign of black silicon generation based on the comparison result of the comparison unit 63A. Specifically, the determination unit 64A determines that a sign of black silicon is generated when the measured average brightness Bdet is equal to or less than a predetermined ratio (brightness ratio threshold) BRthsy with respect to the reference brightness Bs (t). To do. In the present embodiment, the brightness ratio threshold value BRthsy is set to about 0.8 (80%). The condition for the determination unit 64A to determine that a sign of black silicon is occurring is shown in the following equation (1).

  The determination unit 64A may determine that a sign of black silicon is generated when the measured average brightness Bdet is less than or equal to a predetermined brightness difference (brightness difference threshold) ΔBthsy than the reference brightness Bs (t). In this case, a condition for the determination unit 64A to determine that a sign of black silicon generation has occurred is shown in the following formula (2).

  In the following description, it is assumed that the brightness ratio threshold value BRthsy of Expression (1) is used.

Next, a dry etching method using the dry etching apparatus 11 of this embodiment will be described. As described above, the substrate 1 is made of a silicon-based material. As process conditions, the etching gas supplied from the gas supply unit 25 is SF ₆ / O ₂ / He gas, and the flow rates of SF ₆ gas, O ₂ gas, and He gas are 60 sccm, 40 sccm, and 1000 sccm, respectively (SF ₆ / O ₂ / He = 60/40/1000 sccm). The power applied from the coil high frequency power supply 38 to the coil 36 is 1500 W, and the power applied from the bias power supply 23 to the lower electrode 22 is 80 W. Furthermore, the pressure in the internal space 15 of the vacuum vessel 12 is maintained at 30 Pa.

  Referring to FIG. 5, first, in step S5-1, the camera 45 is moved by the XY stage 46. Specifically, as shown in FIG. 3, the substrate in the vacuum chamber 12 through the window hole 42 of the casing 40, the window hole 41 of the casing 35, the gap 39 </ b> A of the coil 36, and the transparent portion 30 of the dielectric plate 29. The camera 45 is moved so that a desired position on one surface (region 67A in FIG. 6) is within the field of view. Subsequently, the focus of the camera 45 is adjusted in step S5-2. A laser beam is emitted from the laser light source 47 onto the surface of the substrate 1 and the reflected line is photographed by the camera 45 and used for focus adjustment. Thereafter, in step S <b> 5-3, application of a high frequency voltage from the coil high frequency power supply 38 to the coil 36 is started, and plasma 70 is generated in the internal space of the vacuum vessel 12. At the time of step S5-3, the application of the bias voltage to the lower electrode 22 has not started, and the etching has not started.

  Next, in step S5-4, the camera 45 takes an image (initial image) of the surface of the substrate 1 in a state where the plasma 70 is generated but the etching is not started. In step S5-5, the brightness detector 61 calculates the in-plane average brightness of the target area 68A in the initial image, that is, the initial measured average brightness Bdet. Subsequently, in step S5-6, based on the initial measured average brightness Bdet, the reference brightness storage unit 62 corrects the reference brightness Bs (t). For example, when the initial measured average brightness Bdet is darker than the stored value of the reference brightness Bs (t) at the etching time t = 0, the reference brightness storage unit 62 conceptually indicates by an arrow A1 in FIG. The reference brightness Bs (t) is shifted to the lower brightness side.

After the above steps S5-1 to S5-6 are completed, in step S5-7, application of a bias voltage from the bias power source 23 to the lower electrode 22 is started, and dry etching of the substrate 1 is started. During dry etching, the portion exposed to the plasma 70 without being covered with the resist mask 2 of the substrate 1 is etched by F radical positive ions (S ions, O ions, etc.), He components, etc., which are etching species. Is done. The O component reacts with the Si atoms of the substrate 1 to form a SiO ₂ sidewall protective film.

  The inner surface 29b of the dielectric plate 29 made of quartz is gradually etched when the state exposed to the plasma 70 continues. However, in the present embodiment, the window plate 34 made of sapphire is fixed to the inner surface 29b of the dielectric plate 29 on the lower polishing portion 32, thereby reducing the transparency or cloudiness of the transparent portion 30 of the dielectric plate 29. It is preventing. Sapphire is a highly transparent material and has high resistance to plasma of gases generally used in plasma processing such as F-based gas, Cl-based gas, and Br-based gas. Therefore, even if the window plate 34 made of sapphire continues to be exposed to the plasma 70, the transparency is not lowered or clouded, and the transparent portion 30 maintains appropriate transparency. Since the transparent part 30 maintains appropriate transparency, the camera 45 can take an image of the substrate 1 in the vacuum vessel 12 through the transparent part 30 with high quality.

  During the etching, steps S5-8 to S5-12 are repeated at a sufficiently short time interval. First, in step S5-8, the camera 45 captures an image of the surface (region 67A) of the substrate 1. Subsequently, in step S5-9, the brightness detection unit 61 calculates the measured average brightness Bdet of the target area 68A from the image taken by the camera 45. Next, in step S5-10, the comparison unit 63A compares the measured average brightness Bdet with the reference brightness Bs (t). Specifically, the comparison unit 63A obtains a quotient (Bdet / Bs (t)) obtained by dividing the measured average brightness Bdet by the reference brightness Bs (t). In step S5-11, the determination unit 64A determines the presence or absence of a sign of black silicon generation from the quotient calculated by the comparison unit 63A obtained in step S5-10 and the brightness ratio threshold value BRthsy.

  If the above-described equation (1) is not satisfied in step S5-11, that is, if the determination unit 64A determines that there is no sign of black silicon generation, it is determined in step S5-12 whether or not it is the etching end point. The etching end point can be determined by photographing the laser irradiated to the substrate 1 from the laser light source 47 with the camera 45 and measuring the etching depth. Further, the end point of etching can be determined by the etching time. If the etching end point is detected in step S5-12, the etching ends in step S5-13. On the other hand, if the etching end point is not detected in step S5-12, the processes in steps S5-8 to 5-11 are repeated.

  When the formula (1) is established in the above-described step S5-11, that is, when the determination unit 64A determines that there is a sign of black silicon generation, in step S5-4, the device control unit 54 prevents black silicon generation. Change the process condition to a condition that has priority over the selection ratio. On the other hand, if it is determined that there is an indication of the occurrence of black silicon, in step S5-15, the warning lamp 50 is turned on or a predetermined message or the like is displayed on the display unit 49, so that the operator is informed of the occurrence of black silicon. Informs that this has occurred.

When the measured average brightness Bdet changes as shown in FIG. 7 and the measured average brightness Bdet decreases to 180 at the time of the etching time t1, Bdet / Bs (t) calculated in step S5-10 is 0.8 (lightness). Since it is below the ratio threshold value BRthsy), it is determined in step S5-11 that there is an indication of the occurrence of black silicon. In this case, as shown in FIG. 9A, a certain amount of SiO ₂ -based deposit 4 is deposited at the bottom of the trench 7 at the time of etching time t1, and this deposit 4 reduces the measured average brightness Bdet. Yes. In other words, the monitoring unit 57 determines the presence or absence of a sign of black silicon generation based on a decrease in brightness of the surface of the substrate 1 due to the deposit 4 being deposited on the bottom of the trench 7.

  The process condition change (step S5-14) when it is determined that there is a sign of black silicon generation will be described in detail.

First, the generation of black silicon can be suppressed by increasing the bias voltage applied from the bias power source 23 to the lower electrode 22. In this embodiment, the initial value of the power of the bias voltage is 50 W, but the generation of black silicon can be suppressed by increasing the power to 80 W, for example. If the bias voltage is increased, the speed of ions colliding with the bottom of the trench 7 is increased. In other words, the energy of ion collision increases by increasing the bias voltage. As a result, the SiO ₂ deposit 4 can be scattered from the bottom of the trench 7 by sputtering. On the other hand, when the bias voltage is high, the resist mask 2 is easily scraped by ions, and the selection ratio is lowered. Accordingly, if no sign of black silicon generation is detected, the bias voltage is set low (50 W in this embodiment) with an emphasis on the selection ratio, and the bias voltage is increased only when the sign of black silicon generation is detected ( In this embodiment, 80 W), it is possible to achieve both a suitable selection ratio and prevention of black silicon generation.

Secondly, the generation of black silicon can be suppressed by reducing the pressure of the internal space 15 in the vacuum vessel 12. In this embodiment, the initial value of the pressure is 30 Pa, but the generation of black silicon can be suppressed by reducing the pressure to, for example, 25 Pa. When the pressure in the vacuum vessel 12 is reduced, the time during which the etching gas stays in the vacuum vessel 12 is shortened. Therefore, before the SiO ₂ -based excess deposit 4 is formed at the bottom of the trench 7, etching is performed. The gas is exhausted to the outside of the vacuum vessel 12. On the other hand, when the pressure in the vacuum vessel 12 is low, the speed of ions is increased, so that the resist mask 2 is easily scraped and the selectivity is lowered. Therefore, if no sign of black silicon generation is detected, the pressure is set high with an emphasis on the selection ratio (30 Pa in the present embodiment), and the pressure is set low only when a sign of black silicon generation is detected (present) In the embodiment, 25 Pa) makes it possible to achieve both a favorable selection ratio and prevention of black silicon generation.

Third, the generation of black silicon can be suppressed by reducing the ratio of O ₂ gas in the etching gas. In this embodiment, the initial value of the supply flow rate of O ₂ gas is 40 scmm, but the generation of black silicon can be suppressed by reducing the supply flow rate to 20 scmm, for example. Since black silicon is caused by the SiO ₂ -based deposit 4, if the flow rate of O ₂ gas supplied to the vacuum vessel 12 is reduced and the amount of O component in the vacuum vessel 12 is reduced, the deposit 4 is less likely to be generated. . On the other hand, if the supply flow rate of the O ₂ gas to the vacuum vessel 12 is reduced, a side wall protective layer made of SiO ₂ becomes difficult to form, so that the side walls of the trench 7 are difficult to maintain in a vertical shape. Therefore, if no sign of black silicon is detected, the O ₂ gas supply flow rate is set to a large value (40 sccm in the present embodiment) with emphasis on the formation of the sidewall protective layer, and the sign of black silicon is detected. Only by reducing the supply flow rate of O ₂ gas (20 sccm in this embodiment), it is possible to achieve both the shape of the trench 7 and the prevention of black silicon generation.

By changing the process conditions as described above, deposition of the deposit 4 on the bottom of the trench 7 is suppressed, and generation of black silicon is prevented. The increase in the bias voltage, the decrease in the pressure in the vacuum vessel 12, and the decrease in the supply flow rate of the O ₂ gas may be performed independently, or two or more of these may be performed in combination.

  When the process condition change in step S5-14 is not executed, the amount of the deposit 4 at the bottom of the trench 7 increases. Therefore, as shown by the solid line in FIG. 7, the measured average brightness Bdet further increases after the etching time t1. It continues to decline. However, if the process conditions in step S5-14 are changed to suppress the deposit 4 from being deposited on the bottom of the trench 7, the measured average brightness Bdet after the etching time t1 is relatively large as shown by, for example, a two-dot chain line. Decrease gradually.

  10 to 13 show alternatives to the top wall 16 of the vacuum vessel 12.

  The top wall 16 of the first alternative shown in FIG. 10 is made of a dielectric plate 29 made of quartz. A circular recess 29c is provided on the inner surface 29b of the dielectric plate 29 as viewed from the bottom, and a disc-shaped window plate 71 made of sapphire is fitted into and fixed to the recess 29c. The window plate 71 fitted into the upper polishing portion 31 and the inner surface 29 b of the outer surface 29 a of the dielectric plate 29 functions as the transparent portion 30.

  The second alternative top wall 16 shown in FIGS. 11A to 11C is also made of a dielectric plate 29 made of quartz. On the inner surface 29b of the dielectric plate 29, a holding hole 29d for detachably holding the window plate 72 made of sapphire is formed. The holding hole 29d is a bottomed hole that is substantially circular in a bottom view, and includes a pair of locking portions 29e and 29f protruding inward at the opening edge. On the other hand, the window plate 72 is substantially disc-shaped but includes a pair of locked portions 72a and 72b protruding outward. As shown in FIG. 11B, when the window plate 72 is in a posture in which the locked portions 72a and 72b do not interfere with the locking portions 29e and 29d of the holding hole 29d, the window plate 72 is attached to and detached from the holding hole 29d. it can. On the other hand, as shown in FIG. 11C, the window plate 72 can be held in the holding hole 29d if the window plate 72 is in a posture in which the locked portions 72a and 72b are placed on the locking portions 29e and 29d. The upper polishing portion 31 and the window plate 72 on the outer surface 29 a of the dielectric plate 29 function as the transparent portion 30.

The top wall 16 of the third alternative shown in FIG. 12 includes a dielectric plate 29 made of quartz having upper and lower polishing portions 31 and 32 on the outer surface 29a and the inner surface 29b, a window plate 73 made of sapphire, ceramic (Al ₂ O ₃ ) thin plate holding plate 74, O-ring 75, and fastening bracket 76. The holding plate 74 is formed with a window hole 74a penetrating in the thickness direction. The window plate 73 is disposed in close contact with the lower polishing portion 32 of the inner surface 29 b of the dielectric plate 29. The holding plate 74 is pressed against the dielectric plate 29 by the tightening member 76 via the O-ring 75 so that the window hole 74 a corresponds to the window plate 73. The window plate 73 is fixed to the inner surface 29 b of the dielectric 29 by being sandwiched between the dielectric plate 29 and the holding plate 74. The upper and lower polishing portions 31 and 32 of the dielectric plate 29, the window plate 73, and the window holes 74 a of the holding plate 74 function as the transparent portion 30.

  A top wall 16 of a fourth alternative shown in FIG. 13 includes a plate body 77 made of ceramic. The plate body 77 is formed with a stepped accommodation hole 77a penetrating in the plate thickness direction. The housing hole 77a has a second portion 77e on the inner surface 77d side that is smaller in diameter than the first portion 77c on the outer surface 77b side of the plate 77, and a support portion 77f that protrudes inward is formed on the inner surface 77d side. A window plate 78 made of sapphire is accommodated in the accommodation hole 77a from the outer surface 77b side. The window plate 78 is supported by a support portion 77f through an O-ring 79.

(Second Embodiment)
In the dry etching apparatus 11 according to the second embodiment of the present invention shown in FIG. 14, the determination unit (second determination unit) 64B is a ratio Bdet of the measured average brightness Bdet calculated by the comparison unit 63A to the reference brightness Bs (t). The generation of black silicon is detected from / Bs (t) and the lightness ratio threshold value BRthg. The brightness ratio threshold value BRthg of the present embodiment is different from the brightness ratio threshold value BRthsy of the first embodiment. When the measured average brightness Bdet becomes smaller than the reference brightness Bs (t), black silicon is generated on the substrate 1. It is a value indicating that Accordingly, the lightness ratio threshold value BRthg is at least smaller than the lightness ratio threshold value BRthsy. In the present embodiment, the lightness ratio threshold value BRthg is set to about 0.2 (20%).

  The condition for the determination unit 64B to determine that a sign of black silicon is occurring is shown in the following equation (3).

  The determination unit 64B may determine that black silicon is generated when the measured average lightness Bdet is equal to or less than a reference lightness difference (lightness difference threshold) ΔBthg than the reference lightness Bs (t). In this case, a condition for the determination unit 64B to determine that black silicon is generated is represented by the following expression (4).

  FIG. 15 shows a dry etching method using the dry etching apparatus 11 of the second embodiment. In FIG. 15, steps S15-1 to S15-10 are the same as those in the first embodiment (steps S5-1 to S5-10 in FIG. 5).

  In step S5-11, the determination unit 64B determines whether black silicon is generated. Specifically, the determination unit 64B determines whether black silicon is generated from the ratio Bdet / Bs (t) of the measured average brightness Bdet to the reference brightness Bs (t) calculated by the comparison unit 63B in step S15-10 and the brightness ratio threshold BRthg. Determine.

  If the above equation (3) is not satisfied in step S5-11, that is, if the determination unit 64B determines that black silicon is not generated, it is determined in step S5-12 whether or not it is the etching end point. If it is an etching end point, the etching ends in step S15-13. On the other hand, if the etching end point is not reached, the processes in steps S15-8 to 15-11 are repeated.

  When Expression (3) is satisfied in Step S15-11 described above, that is, when the determination unit 64B determines that black silicon is generated, the apparatus control unit 54 forcibly ends the etching. At this time, the operator may be notified that black silicon is generated by turning on the warning lamp 50 or displaying a predetermined message or the like on the display unit 49.

When the measurement average brightness Bdet changes as shown in FIG. 7 and the measurement average brightness Bdet decreases to 50 at the time of the etching time t2, Bdet / Bs (t) calculated in step S15-10 is 0.2 (lightness). Therefore, it is determined in step S15-11 that black silicon is generated. In this case, as shown in FIG. 9B, a large amount of SiO ₂ -based deposit 4 is deposited at the bottom of the trench 7 at the etching time t2, and this deposit 4 greatly reduces the measured average brightness Bdet. Yes. In other words, the monitoring unit 57 determines whether black silicon is generated based on a decrease in brightness of the surface of the substrate 1 due to the deposit 4 being deposited on the bottom of the trench 7.

  Other configurations and operations of the second embodiment are the same as those of the first embodiment.

(Third embodiment)
The dry etching apparatus 11 according to the third embodiment of the present invention shown in FIG. 16 is replaced with the reference brightness storage unit 62 (see FIGS. 4 and 14) of the first and second embodiments, and the black silicon determination brightness storage unit 80. (Hereinafter abbreviated as a judgment lightness storage unit).

  The determination lightness storage unit 80 stores a determination lightness Bdg (t) used to determine whether black silicon is generated in the target area 68A. FIG. 7 shows an example of the determination lightness Bdg (t). The determination brightness Bdg (t) is a change in the surface average brightness of the target area 68A with respect to the etching time t when black silicon is generated.

  The comparison unit (second comparison unit) 63B compares the measured average lightness Bdet calculated by the lightness detection unit 61 with the determination lightness Bdg (t) stored in the determination lightness storage unit 80. Specifically, the comparison unit 63B compares the measured average brightness Bdet of the target area 68A at a certain time t with the determined brightness Bdg (t) at the same time t.

  The determination unit (third determination unit) 64C determines whether black silicon has been generated based on the comparison result of the comparison unit 63B. Specifically, the determination unit 64C determines that black silicon is generated when the measured average lightness Bdet is equal to or less than the determination lightness Bdg (t). The condition that the determination unit 64C determines that black silicon is generated is shown in the following formula (5).

  A dry etching method using the dry etching apparatus 11 of this embodiment will be described with reference to FIG. Steps S17-1 to 17-5 are the same as those in the first embodiment (steps S5-1 to 5-5 in FIG. 5).

  In step S17-6, the determination lightness storage unit 80 corrects the determination lightness Bdg (t) based on the initial measurement average lightness Bdet. For example, when the initial measured average brightness Bdet is darker than the value of the stored determination brightness Bs (t) at the etching time t = 0, the determination brightness storage section 80 conceptually indicates by an arrow A2 in FIG. The determination lightness Bdg (t) is shifted to a lower lightness side.

  After the dry etching is started in step S17-7, the processes in steps S17-8 to S17-12 are repeated at a sufficiently short time interval. First, in step S17-8, the camera 45 captures an image of the area 67A of the substrate 1. Subsequently, in step S17-9, the brightness detection unit 61 calculates the measured average brightness Bdet of the target area 68A from the image captured by the camera 45. Next, in step S17-10, the comparison unit 63B compares the measured average brightness Bdet with the determined brightness Bdg (t). Further, in step S17-11, the determination unit 64C determines whether or not black silicon is generated.

  If the above-described equation (5) is not satisfied in step S17-11, that is, if the determination unit 64C determines that black silicon is not generated, the etching end point is detected and etching is completed (step S17-12). S17-13) and steps S17-8 to 17-11 are repeated.

  If the above-described equation (5) is satisfied in step S17-11, that is, if the determination unit 64C determines that black silicon is generated, the apparatus control unit 54 forcibly ends the etching. At this time, the operator may be notified that black silicon is generated by turning on the warning lamp 50 or displaying a predetermined message or the like on the display unit 49.

  When the measured average brightness Bdet changes as shown in FIG. 7 and the measured average brightness Bdet becomes equal to or less than the determined brightness Bdg (t) at the etching time t2, it is determined in step S17-11 that black silicon is generated. The Similar to the first and second embodiments, the monitoring unit 57 determines whether black silicon has been generated based on a decrease in brightness of the surface of the substrate 1 caused by the deposit 4 being deposited on the bottom of the trench 7.

  Other configurations and operations of the third embodiment are the same as those of the first embodiment.

1 is a schematic cross-sectional view of a dry etching apparatus according to a first embodiment of the present invention. 1 is a schematic plan view of a dry etching apparatus according to a first embodiment of the present invention. 1 is a schematic partial perspective view of a dry etching apparatus according to a first embodiment of the present invention. 1 is a block diagram of a dry etching apparatus according to a first embodiment of the present invention. The flowchart for demonstrating operation | movement of the dry etching apparatus which concerns on 1st Embodiment of this invention. The schematic diagram for demonstrating a target area | region. The diagram which shows an example of the relationship between reference | standard lightness, sign determination lightness, generation | occurrence | production lightness, and measured lightness. The typical perspective view which shows the board | substrate in the middle of the etching of the state in which the sign of black silicon generation | occurrence | production is not recognized. The typical perspective view which shows the board | substrate in the middle of the etching in the state where black silicon has not generate | occur | produced. The typical perspective view of the board | substrate in the middle of the etching in which the sign of black silicon generation | occurrence | production is recognized. The typical perspective view of the board | substrate in the middle of the etching in the state in which the black silicon was generated. Sectional drawing which shows the 1st alternative of the top wall of a vacuum vessel. Sectional drawing which shows the 2nd alternative of the top wall of a vacuum vessel. The bottom view which shows the 2nd alternative (at the time of attachment or detachment of a window plate) of the top wall of a vacuum vessel. The bottom view which shows the 2nd alternative (state with which the window plate was mounted | worn) of the top wall of a vacuum vessel. Sectional drawing which shows the 3rd alternative of the top wall of a vacuum vessel. Sectional drawing which shows the 4th alternative of the top wall of a vacuum vessel. The block diagram of the dry etching apparatus which concerns on 2nd Embodiment of this invention. The flowchart for demonstrating operation | movement of the dry etching apparatus which concerns on 2nd Embodiment of this invention. The block diagram of the dry etching apparatus which concerns on 3rd Embodiment of this invention. The flowchart for demonstrating operation | movement of the dry etching apparatus which concerns on 3rd Embodiment of this invention. The schematic diagram for demonstrating generation | occurrence | production of the black silicon phenomenon in the etching of the board | substrate consisting of a silicon system material. The schematic diagram for demonstrating generation | occurrence | production of the black silicon phenomenon in the etching of the board | substrate consisting of a silicon system material.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Resist mask 7 Trench 8 Deposit 11 Dry etching apparatus 12 Vacuum container 13 Bottom wall 14 Side wall 15 Internal space 16 Top wall 21 Mounting stage 22 Lower electrode 23 Power supply for bias 23a High frequency AC power supply 23b Matching circuit 24 Gas inlet 25 Gas supply unit 27 Exhaust port 28 Decompression unit 29 Dielectric plate 29a Outer surface 29b Inner surface 30 Transparent unit 31 Upper polishing unit 32 Lower polishing unit 34 Window plate 35 Casing 35a Upper wall 36 Coil 37 Conductor 38 High frequency power supply 38a for coil High frequency AC Power supply 38b Matching circuit 39A, 39B, 39C, 39D Gap 40 Casing 41, 42 Window hole 45 Camera 46 XY table 46a Y-axis slider 46b Y-axis drive motor 46c X-axis slider 46d X-axis drive motor 47 Laser light source 4 Display unit 50 Warning light 51 Operation input unit 54 Device control unit 55 Control unit 56 Operating condition storage unit 57 Monitoring unit 61 Lightness detection unit 62 Reference lightness storage unit 63A, 63B Comparison unit 64A, 64B, 64C Determination unit 70 Plasma 80 Determination lightness Storage

Claims (23)

A dry etching method for a substrate (1) made of a silicon-based material,
Acquire an image of the etched surface of the substrate being processed by dry etching,
Based on the acquired image, a measurement brightness (Bdet) that is the brightness of a predetermined measurement location (68A, 68B) of the etched surface of the substrate is calculated,
Based on the measured brightness, monitors the occurrence or indication thereof black silicon dry etching method. The measured brightness is compared with a reference brightness (Bs (t)) that is the brightness of the measurement location corresponding to the passage of time from the start of dry etching when black silicon is not generated,
The dry etching method according to claim 1 , wherein generation of black silicon or presence / absence of a sign thereof is determined based on a result of the comparison. 3. The dry etching method according to claim 2 , wherein when the measured lightness is equal to or lower than a first ratio (BRthsy) predetermined with respect to the reference lightness, it is determined that a sign of black silicon is generated. 3. The dry etching method according to claim 2 , wherein when the measured lightness is equal to or less than a first lightness difference (ΔBRthsy) that is predetermined from the reference lightness, it is determined that a sign of black silicon is generated. When signs of the black silicon occurs are detected, and changing the conditions of the dry etching, a dry etching method according to claim 3 or claim 4. 6. The dry etching method according to claim 5 , wherein when a sign of black silicon generation is detected, a bias voltage applied to a lower electrode on which the substrate is placed is increased. 6. The dry etching method according to claim 5 , wherein when an indication of the generation of black silicon is detected, the pressure in the vacuum container in which the substrate is accommodated is reduced. Using an etching gas containing at least SF ₆ , O 2 and He,
The dry etching method according to claim 5 , wherein when an indication of the generation of black silicon is detected, the content of O _{2 in} the etching gas is reduced. 6. The dry etching method according to claim 5 , wherein when a sign of the occurrence of black silicon is detected, it is notified. 3. The dry etching method according to claim 2 , wherein when the measured brightness is equal to or less than a second ratio (BRthg) that is predetermined with respect to the reference brightness, it is determined that black silicon is generated. 3. The dry etching method according to claim 2 , wherein when the measured brightness is equal to or less than a second brightness difference (ΔBRthsg) determined in advance from the reference brightness, it is determined that black silicon is generated. The dry etching method according to claim 10 or 11 , wherein dry etching is stopped when the generation of black silicon is detected. Wherein the black silicon occurs are detected, the dry etching method according to claim 10 or claim 11, wherein the notifying it. The measured brightness is compared with the determination brightness (Bdg (t)), which is the brightness of the measurement location corresponding to the passage of time from the start of dry etching when black silicon is generated,
Determining the presence or absence of black silicon occurs on the basis of the result of the comparison, a dry etching method according to claim 1. The dry etching method according to claim 14 , wherein when the measured brightness is equal to or less than the determined brightness, it is determined that black silicon is generated. 16. The dry etching method according to claim 14 , wherein dry etching is stopped when the generation of black silicon is detected. 16. The dry etching method according to claim 14, wherein the generation of black silicon is detected when it is detected. A vacuum vessel (12) in which a substrate (1) made of a silicon-based material is disposed;
A plasma source (36) for generating plasma in the vacuum vessel;
An imaging device (45) for acquiring an image of the surface to be etched of the substrate being processed by dry etching by generating plasma in the vacuum vessel by the plasma source;
A monitoring unit (57) for monitoring the occurrence of black silicon or its sign based on the image acquired by the photographing apparatus;
With
The monitoring unit
A brightness detection unit (61) that calculates a measured brightness (Bdet), which is the brightness of a predetermined measurement location (68A, 68B), of the etched surface of the substrate based on an image acquired by the imaging apparatus. , based on the measurement lightness, that monitor the occurrence or indication thereof black silicon, de dry etching apparatus. The monitoring unit
A reference brightness storage unit (62) that stores a reference brightness (Bs (t)) that is the brightness of the measurement location corresponding to the passage of time from the start of dry etching when black silicon is not generated;
A first comparison unit (63A) that compares the measured lightness calculated by the lightness detection unit with the reference lightness stored in the reference lightness storage unit;
19. The dry etching apparatus according to claim 18 , further comprising: a first determination unit (64 </ b> A) that determines presence / absence of a sign of black silicon generation based on a comparison result of the first comparison unit. The dry etching apparatus according to claim 19 , further comprising an apparatus control unit (54) that changes a dry etching condition when the determination unit determines that the sign of the occurrence of black silicon has occurred. The monitoring unit
A reference brightness storage unit (62) that stores a reference brightness (Bs (t)) that is the brightness of the measurement location corresponding to the passage of time from the start of dry etching when black silicon is not generated;
A first comparison unit (63A) that compares the measured lightness calculated by the lightness detection unit with the reference lightness stored in the reference lightness storage unit;
The dry etching apparatus according to claim 18 , further comprising: a second determination unit (64 </ b> B) that determines whether black silicon is generated based on a comparison result of the first comparison unit. The monitoring unit
A black silicon determination brightness storage unit (80) that stores a determination brightness (Bdg (t)) that is the brightness of the measurement location corresponding to the passage of time from the start of dry etching when black silicon is generated;
A second comparison unit (63B) that compares the measured lightness calculated by the lightness detection unit with the determination lightness stored in the black silicon determination lightness storage unit;
19. The dry etching apparatus according to claim 18 , further comprising: a third determination unit (64 </ b> C) that determines whether black silicon is generated based on a comparison result of the second comparison unit. A plasma generating coil (36) including a conductor (37) disposed above the outside of the vacuum vessel and disposed so as to form a gap (39A) in plan view;
The top wall of the vacuum vessel has a transparent portion (30) at a position corresponding to the gap between the conductors of the coil in plan view,
The imaging device is disposed above the coil, and includes at least a part of the etched surface of the substrate in a field of view through a gap between conductors of the coil and a transparent portion of the top wall. The dry etching apparatus according to any one of claims 18 to 22 .

Images