CN106643598A - Deposition APF equipment shadow shadowring position deviation detecting and solving method - Google Patents

Abstract

The present invention proposes a method for detecting shadow ring position offset in deposited APF equipment, which is characterized in that the center of the silicon wafer after APF deposition is taken as the center, and notch is used as the edge reference point of the silicon wafer, and the method is established after deviating from the notch by a certain angle In the Cartesian coordinate system, select different coordinate points located on the Cartesian coordinate axis in the silicon chip edge circle concentric with the Cartesian coordinate system, measure the film thickness, draw a graph according to the coordinates, and compare the film thickness values. The present invention also proposes a method for solving shadow ring position deviation in deposition APF equipment. Based on the above method for detecting shadow ring position deviation, the shadow ring position deviation is found from the distribution diagram of coordinates and film thickness, and adjustments and corrections are made in time. . This invention is used in daily spot inspection and post-PM spot inspection, and the collected data is drawn as a film thickness curve, which can intuitively see whether the position of the shadow ring has shifted, helping engineers to solve it in time and eliminate the position shift of the shadow ring , to avoid the occurrence of APF particle defects, to achieve the purpose of improving product quality.

Description

A method for detecting shadowring position deviation of deposited APF equipment and its solution

technical field

The invention relates to the technical field of integrated circuits, in particular to a method for detecting the position deviation of a shadow ring in an APF (advanced patterning film) device, and a solution to the position deviation.

Background technique

After the development of integrated circuit manufacturing technology to 90 nanometers and below, the influence of the line width and morphology of the circuit structure on the performance of the device is more important. Therefore, the requirements for its accuracy in the process are more stringent, and many auxiliary films are added to optimize the photolithography. And etching effect, APF-advanced graphics film is one of them.

The main component of APF-advanced graphics film is amorphous carbon, which has a high etching selectivity ratio. During the etching process, it replaces the photoresist to form a pattern and acts as a mask layer to complete the etching; it itself can be oxidized by oxygen and can It is removed by stripping process like photoresist.

The deposition of APF belongs to the CVD process, and its deposition principle is: the gas C2H2 is cracked under the action of Plasma to generate amorphous carbon, covering the entire wafer to form a carbon film. As we all know, a silicon wafer is a round wafer with a certain thickness, and its edges are chamfered to form continuous and smooth sides. The gaseous reactants in the CVD process will flow and infiltrate the side of the silicon wafer, where the deposition reaction occurs to form an amorphous carbon film-APF, and the thickness of the deposited APF at the edge of the silicon wafer is uneven and uncontrolled. Therefore, the range of the deposited film controlled by the general CVD process is from the center of the silicon wafer to a circular area 3mm away from the edge of the silicon wafer.

The APF deposited on the 3 mm ring area on the edge of the silicon wafer and the side may be peeled off during the subsequent photolithography and etching process, falling into the circuit and becoming a particle defect, thereby affecting device performance. In order to prevent APF from depositing on the edge of the wafer, there is another part called shadow ring in the cavity of the APF deposition equipment. After the silicon wafer is loaded-in, the shadow ring moves down from the top of the silicon wafer together with the upper electrode shower head, and the shadow ring covers and presses the edge of the wafer. Therefore, the APF that should have been deposited on the edge of the wafer will be deposited on the shadow ring, and will be taken away with the removal of the shadow ring after the process is completed. It can be seen that the role of the shadow ring is to prevent the deposition of thin films on the edge of the silicon wafer. The APF deposition process using the shadow ring needs to cooperate with the subsequent photolithography process so that the subsequent photoresist coating covers the entire APF deposition area, so as to completely avoid particle defects in the subsequent photolithography and etching processes.

The shadow ring used in the prior art is a circular ceramic ring, which is fixed together with the upper electrode shower head in the cavity of the CVD equipment. During the process of loading the silicon wafer, the silicon wafer is mechanically moved upwards, so that the shadowring covers the ring area of 3-5 mm at the outermost edge of the silicon wafer. The best position for covering the silicon wafer is the distance between A concentric circle with an edge of 3 to 5 mm and the center coincides with the center of the silicon wafer. In fact, during regular maintenance, if the shadow ring is not properly installed, its position will shift, so its position covering the edge of the silicon wafer will also shift, forming an eccentric circle. If the deviation distance eventually exceeds the coverage of the subsequent photoresist coating, part of the APF in the edge region of the silicon wafer in the opposite direction to the deviation direction will be exposed in the plasma during etching because there is no photoresist coverage. After etching, substrate pits will be formed in this area; if the further offset distance is greater than 3 to 5 mm, the edge of the silicon wafer and the side of the silicon wafer in the opposite direction of the deviation may not be covered by the shadow ring at all, so that the abnormal thickness of the edge The remaining APF may still remain after etching, and may be peeled off at any time in many subsequent processes, becoming particle defects.

Therefore, it is necessary to develop a method for detecting the position shift of the shadow ring in the deposition APF equipment, which can detect its position shift in time, and adjust its position to correct and eliminate the shift, thereby solving the problem of the shadow ring position shift and avoiding silicon chip Particle defects are generated to achieve the ultimate goal of improving product quality.

Contents of the invention

The technical problem to be solved by the present invention is to detect the position of the shadow ring in the deposition APF equipment, to detect and solve the problem of shadow ring position deviation in time, to avoid particle defects in silicon wafers, and to achieve the ultimate goal of improving product quality.

In order to solve the above-mentioned technical problems, the present invention proposes a method for detecting the offset of the shadow ring position in the deposition APF equipment, which is characterized in that the center of the silicon wafer after the APF deposition is the center, and notch is the edge reference point of the silicon wafer, After deviating from the notch by a certain angle, establish a rectangular coordinate system, select different coordinate points located on the rectangular coordinate axis in the silicon chip edge ring concentric with the rectangular coordinate system, measure its film thickness value, and make the film thickness according to the coordinates Distribution map, compare the film thickness values at the same coordinates;

Optionally, the angle at which the Cartesian coordinate system centered on the center of the silicon wafer deviates from the notch position on the edge of the silicon wafer is 0° to 90°;

Optionally, the ring on the edge of the silicon wafer concentric with the Cartesian coordinate system extends from the edge of the silicon wafer to the inside of the silicon wafer, and the radius of the ring is not less than 3.5 mm;

Preferably, a series of coordinate points at the same intervals with a distance equal to the edge of the silicon wafer on different coordinates are selected to measure the film thickness;

Preferably, the distance between the measurement points of the film thickness value is not greater than 0.5 mm;

Optionally, the drawing method is to use the horizontal axis of the coordinates of the film thickness test point and the measured film thickness value on the vertical axis to make a distribution diagram of coordinates and film thickness;

Preferably, the horizontal coordinates of the distribution graph take the absolute values of the coordinates of the film thickness test points.

The present invention also proposes a method for solving the position deviation of the shadow ring in the deposition APF equipment,

The specific steps are:

Step S01: Select a silicon wafer to complete APF deposition;

Step S02: Taking the center of the silicon wafer as the center and notch as the edge reference point of the silicon wafer, a rectangular coordinate system is established after deviating from the notch by a certain angle, and a silicon wafer edge ring concentric with the rectangular coordinate system is selected to be located at the right angle Measure the film thickness at different coordinate points on the coordinate axis, and make a distribution map of the film thickness according to the coordinates;

Step S03: The direction of the coordinate axis where the distance and the film thickness curve in the film thickness distribution diagram do not coincide is the offset direction of the shadow ring;

Step S04: Adjust the position of the shadow ring to eliminate the offset;

Optionally, the abscissa of the distribution graph is the absolute value of the coordinate, and the ordinate is the film thickness value of the corresponding coordinate.

After the integrated circuit enters the technology node of 90 nanometers and below, when the etching is faced with the process challenge of narrow line width and deep trench, the traditional photolithography process has the situation that the photoresist cannot resist the etching, which affects the realization of the graphics. This is because the etching selection ratio of photoresist is generally 1:6, that is, to etch a substrate with a depth of 600A, 100A of photoresist needs to be consumed. In fact, the required photoresist is much larger than the theoretical consumption value. In actual operation, the smaller the line width, the thinner the film thickness of the photoresist used to improve the lithography capability will be, which directly leads to the insufficient etching resistance of the photoresist, and there is a contradiction between the two. In the prior art, advanced pattern film (APF) combined with nitrogen-free anti-reflective layer (N-free DRAC) was introduced to solve this problem, which further improved the existing lithography capability and further reduced the process line width. As shown in Figure 1 Shown: a) APF 4 and nitrogen-free anti-reflection layer (N-free DRAC) 3 are deposited on the polysilicon 1, and then photoresist 2 is applied and developed. According to the photolithography ability, only a pattern with a line width of A can be formed; b) Etching the photoresist, making the photoresist thinner, and reducing the line width of the photoresist pattern from A to B; c) continuing to etch the APF 4 with the remaining photoresist 2 as the mask layer, and the photoresist is consumed. At the same time, the APF slims down, and the line width is further reduced from B to C; d) Use APF 4 as the mask layer to continue etching polysilicon 1. Because APF has a high etching selectivity, it resists narrow line width and deep trenches. Etching for a long time to form a polysilicon 1 pattern with a line width of C; e) removing the remaining APF 4 by removing the glue, and finally completing the polysilicon etching with the line width reduced from A to C.

Fig. 2 is a comparison diagram of the etching topography of the traditional photolithography process using only photoresist as the mask layer (left picture) and the prior art using APF as the mask layer (right picture).

The main component of APF-advanced graphics film is amorphous carbon, which has a high etching selectivity ratio. During the etching process, it replaces the photoresist to form a pattern and acts as a mask layer to complete the etching; it itself can be oxidized by oxygen and can It is removed by stripping process like photoresist.

The deposition of APF belongs to the CVD process, and its deposition principle is: the gas C2H2 is cracked under the action of Plasma to generate amorphous carbon, covering the entire wafer to form a carbon film. As we all know, a silicon wafer is a round wafer with a certain thickness, and its edges are chamfered to form continuous and smooth sides. The gaseous reactants in the CVD process will flow and infiltrate the side of the silicon wafer, where the deposition reaction occurs to form an amorphous carbon film-APF, and the thickness of the deposited APF at the edge of the silicon wafer is uneven and uncontrolled. Therefore, the range of the deposited film controlled by the general CVD process is within 3 mm from the edge of the silicon wafer.

The ring-shaped area deposited within 3 mm of the edge of the silicon wafer and the APF on the side may be peeled off in the subsequent photolithography and etching processes, and once it falls into the circuit, it will become a particle defect and affect the performance of the device. In order to prevent APF from depositing on the edge of the wafer, there is another component called shadow ring in the chamber of the APF deposition equipment, which is fixed in the chamber together with the upper electrode shower head. During the process, after the silicon wafer is loaded-in, it moves upward mechanically so that the shadow ring covers and presses the edge of the wafer. Therefore, the APF that should have been deposited on the edge of the wafer will be deposited on the shadow ring, and will be taken away with the removal of the shadow ring after the process is completed. It can be seen that the role of the shadow ring is to prevent the deposition of thin films on the edge of the silicon wafer. The deposition of APF using the shadow ring needs to cooperate with the subsequent photolithography process to achieve the subsequent photolithography coating to cover the APF deposition area, so as to completely avoid particle defects in the subsequent photolithography and etching processes.

Although the shadow ring has been used in the prior art to prevent the deposition of the APF film on the edge of the silicon wafer, the monitoring method for the position shift of the shadow ring is still blank. At present, only when APF is deposited and undergoes photolithography and etching, and APF particle defects are found in the subsequent particle detection, will it be retrospectively found that the shadow ring of the APF deposition equipment has shifted. This time delay not only brings about an increase in the number of affected silicon wafers, but may even cause a more serious impact on product quality as the degree of offset worsens.

The present invention proposes a method that can timely detect the position deviation of the shadow ring in the deposition APF equipment, which can detect the position deviation in time, avoid silicon chip particle defects, and achieve the ultimate goal of improving product quality. The present invention takes the circle center of the silicon chip after APF deposition as the center, takes notch as the reference point of the edge of the silicon chip, and establishes a rectangular coordinate system after deviating from the notch at a certain angle, and selects the edge circle of the silicon chip concentric with the rectangular coordinate system to be located at the edge of the silicon chip. Measure the film thickness of different coordinate points on the rectangular coordinate axis, draw a graph according to the coordinates, and compare the film thickness.

Specifically, the present invention takes the center of the silicon wafer as the center, establishes a rectangular coordinate system, and measures the edge of the silicon wafer from the positive and negative directions of the X/Y axis in four directions, which are the same as the inner distance edge of the concentric circle of the silicon wafer. Film thickness at distance points and compare. The establishment of the coordinates needs to avoid the notch position used for the orientation of the silicon wafer. Correlate the film thickness value with the position of the measuring point, where the position of the measuring point is the horizontal axis, and the film thickness value is the vertical axis. A total of 4 curves are generated, which respectively show: the film thickness in the positive and negative directions of the X-axis varies with the distance from the edge of the silicon wafer and the change of the film thickness in the positive and negative directions of the Y axis with the distance from the edge of the silicon wafer. If the shadow ring does not shift, and the pattern generated by APF deposition on the silicon wafer is a concentric circle with a distance of 3 to 5 mm from the edge of the silicon wafer and the center coincides with the center of the silicon wafer, then the above four curves should coincide; if the above four curves are found Separation occurs, which means that the position of the shadow ring has shifted. Since the deposition of APF using shadow ring needs to cooperate with the subsequent photolithography process, so that the subsequent photolithography glue can completely cover the deposition area of APF to avoid particle defects in the subsequent photolithography and etching process, so if the offset has been Beyond the intersection of the subsequent photoresist and the shadow ring covering the edge of the silicon wafer, position adjustment and correction are required to eliminate the offset.

A further optimization scheme is that, according to the CVD process in the prior art, the range of the deposited film generally controlled is 3 millimeters from the edge of the silicon wafer, and the present invention determines that the radius of the ring at the edge of the silicon wafer for measuring the film thickness is 3.5 millimeters, and at the same time, in order to balance the detection In terms of efficiency and measurement time, the present invention sets a film thickness measurement every 0.5 mm within 3.5 mm, that is, a total of 8 points are measured within a distance of 0-3.5 mm. In this way, it is possible to fully measure whether there is APF deposition in the ring area covered by the shadow ring on the edge of the silicon wafer, and it also meets the practical requirements of production and manufacturing. At the same time, it can also provide enough data to determine whether the shadow ring has shifted, along which The direction to move and the approximate distance to move.

The present invention also provides a method for solving the offset of the shadow ring position in the deposition APF equipment. By using the above detection method for the offset of the shadow ring position, the offset direction and approximate distance can be found in time, and adjustments can be made to correct and eliminate the offset. Minimize impact on wafer quality.

In summary, the method for detecting the offset of the shadow ring position in the deposition APF equipment proposed by the present invention and the method for adjusting the position of the shadow ring in time based on the detection and eliminating the offset, establish a rectangular coordinate system centered on the center of the silicon wafer, respectively Along the X/Y axis of the coordinate system, measure the film thickness at the same distance from the edge of the silicon wafer edge and the center of the silicon wafer circle in the four directions of positive and anti-communication, and compare the graphs, so that the position of the shadow ring can be found in time. , and make adjustments, correct and eliminate offsets, avoid silicon wafer particle defects, and achieve the ultimate goal of improving product quality.

Description of drawings

Figure 1 is a schematic diagram of using APF to improve photolithography capability.

FIG. 2 is a schematic diagram of etching topography of a traditional photoresist process and an APF process of the prior art.

Figure 3 is a comparison of the normal position and offset position of the shadow ring.

Fig. 4 is a film thickness measurement point of the detection method of the present invention.

Fig. 5 is a graph of film thickness at various distances from the edge of a silicon wafer drawn according to the present invention.

detailed description

In order to make the content of the present invention clearer and easier to understand, the content of the present invention will be further described below in conjunction with the accompanying drawings. Of course, the present invention is not limited to this specific embodiment, and general replacements known to those skilled in the art are also covered within the protection scope of the present invention.

Secondly, the present invention is described in detail by means of schematic diagrams. When describing the examples of the present invention in detail, for the convenience of explanation, the schematic diagrams are not partially enlarged according to the general scale, which should not be used as a limitation of the present invention.

Embodiments of the present invention will be further described below in conjunction with the accompanying drawings.

As shown in FIG. 3 , it is a comparison diagram of the normal position and offset of the shadow ring in the APF deposition equipment where the present invention is located. In Figure 3, a is the shadow ring, and b is the silicon wafer. The left part of the figure is the situation where the shadow ring is in a normal position: at this time, the shadow ring-a evenly covers the edge of the silicon wafer-b, so there is no APF deposition in the area of 3-5 mm from the edge of the silicon wafer; the right part of the figure is the shadow The case where the ring shifts to the upper right: at this time, the upper right area covered by the shadow ring increases, while the lower left edge decreases. Defined area A is located near the lower left edge of wafer b. As shown in the right part of Figure 3, if area A can still be covered by the subsequent photoresist coating area, there are fewer chances of generating APF particles; The lower left edge of the silicon wafer b, then this area will exceed the range covered by the photoresist coating area, then the APF film will be deposited in this area after the CVD process, and the APF film will be affected by the edge morphology of the silicon wafer , the deposition thickness is uneven and uncontrolled. These APF films deposited on the 3 mm ring area on the edge of the silicon wafer and on the side may be peeled off in the subsequent photolithography and etching processes, and once they fall into the circuit and become particle defects, it will affect the performance of the device.

The shadow ring involved in this embodiment is a ring-shaped ceramic ring, and its function is to cover the edge of the wafer when depositing a thin film, so as to effectively prevent APF from being deposited on the edge of the wafer.

In order to detect in time whether the position of the shadow ring of the APF deposition equipment has shifted, this embodiment proposes a measurement method: on a piece of silicon wafer after APF deposition, take the center of the silicon wafer as the center, and counterclockwise from the edge of the silicon wafer to the notch Cartesian coordinates are established at the position deflected by 45°, the positive and negative directions of the X axis correspond to 135° and 315°, and the positive and negative directions of the Y axis correspond to 45° and 225°. Since the shadow ring covers the edge of the silicon wafer by 3 millimeters in the present embodiment, the film thickness in the range of 0 to 3.5 millimeters along the above-mentioned 4 directions of 45 °, 135 °, 225 ° and 315 ° is set at the edge of the test silicon wafer, and each interval is Measure once at 0.5 mm, and measure film thickness values at 4*8=32 points in total, as shown in Figure 4.

Then, take the distance of 0-3.5 mm as the horizontal axis, and the film thickness value as the vertical axis to make a correlation diagram between the distance and the film thickness, as shown in FIG. 5 . Figure 5 shows the film thickness test results when the shadow ring position is accurate. The four directions start to have APF film about 2mm away from the edge of the wafer, and the four lines are coincident. If the position of the shadow ring deviates, the four lines in the test result will definitely not overlap, and you need to adjust and correct the position of the shadow ring in time to make it return to the normal position. This method can effectively detect and solve the problem of shadow ring position deviation in APF deposition equipment.

Applying this invention to daily spot inspection and post-PM spot inspection, and drawing the collected data as a film thickness curve, it is very intuitive to see whether the position of the shadow ring has shifted, so as to help engineers solve it in time and eliminate the shadow ring The position is offset to avoid the occurrence of APF particle defects.

To sum up, the present invention proposes a method for detecting the position shift of the shadow ring in the deposition APF equipment. Combining with the detection method of the present invention, the shift can be found in time, and the shift can be eliminated by adjusting and correcting. Solve the problem of shadow ring position offset, avoid silicon wafer particle defects, and finally achieve the ultimate goal of improving product quality.

The above description is only a description of the embodiments of the present invention, and does not limit the scope of the present invention. Any changes and modifications made by those of ordinary skill in the field of the present invention based on the above disclosures shall fall within the protection scope of the claims.

Claims (9)

1. A method for detecting shadow ring position deviation in deposition APF equipment, characterized in that the center of circle of the silicon wafer after APF deposition is the center, with notch as the edge reference point of the silicon wafer, and a right angle is established after deviating from the notch for a certain angle Coordinate system, select different coordinate points located on the rectangular coordinate axis in the silicon wafer edge ring concentric with the rectangular coordinate system, measure its film thickness value, make a distribution map of film thickness according to coordinates, and compare the film with the same coordinates thick value. 2. a kind of method as claimed in claim 1 detects the position deviation of shadow ring in deposition APF equipment, it is characterized in that, the angle that the Cartesian coordinate system deviates from the edge notch position of silicon wafer is 0 with the silicon wafer circle center as the center °～90°. 3. a kind of method as claimed in claim 1 detects the position deviation of shadow ring in deposition APF equipment, it is characterized in that, the silicon chip edge ring that is concentric with Cartesian coordinate system, its ring range is from silicon chip The edge extends into the silicon wafer, and the radius of the ring is not less than 3.5 mm. 4. a kind of method as claimed in claim 3 detects the position deviation of shadow ring in deposition APF equipment, it is characterized in that, choose a series of coordinate point measurement films of the same interval that distance on different coordinates is equal to the edge distance of silicon wafer thick value. 5. A method for detecting shadow ring position deviation in deposition APF equipment as claimed in claim 4, characterized in that the distance between the film thickness measurement points is not greater than 0.5 mm. 6. a kind of method as claimed in claim 1 detects the shadow ring position deviation in deposition APF equipment, it is characterized in that, described drawing method is, with the coordinate horizontal axis of film thickness test point, with measured The film thickness value is a distribution diagram of coordinates and film thickness on the vertical axis. 7. A method for detecting shadow ring position deviation in deposition APF equipment as claimed in claim 6, characterized in that the horizontal coordinates of the distribution map take the absolute value of the coordinates of the film thickness test points. 8. A method for solving shadow ring position offset in deposition APF equipment, the specific steps are: Step S01: Select a silicon wafer to complete APF deposition; Step S02: Taking the center of the silicon wafer as the center, taking notch as the edge reference point of the silicon wafer, establishing a Cartesian coordinate system after deviating from the notch at a certain angle, selecting the silicon wafer edge ring concentric with the Cartesian coordinate system to be located at the right angle Measure the film thickness at different coordinate points on the coordinate axis, and make a distribution map of the film thickness according to the coordinates; Step S03: The direction of the coordinate axis where the distance and the film thickness curve in the film thickness distribution diagram do not coincide is the offset direction of the shadow ring; Step S04: Adjust the position of the shadow ring to eliminate the offset. 9. A method for detecting shadow ring position deviation in deposition APF equipment as claimed in claim 1, wherein the abscissa of the profile is the absolute value of the coordinate, and the ordinate is the film thickness of the corresponding coordinate value.