JP6541308B2 - Exposure method, exposure apparatus and device manufacturing method - Google Patents

Description

  The present invention relates to an exposure method, an exposure apparatus, and a device manufacturing method.

  In Patent Document 1, in order to perform relative alignment between the reticle and the wafer with high accuracy, a sensor is mounted which constantly detects the relative positional relationship between the reticle and the reticle stage and constantly measures the displacement of the reticle. An exposure apparatus is disclosed.

JP 2000-003855 A

  However, the conventional exposure apparatus described in Patent Document 1 needs a sensor that constantly measures the displacement of the reticle relative to the reticle stage. In addition, if the reticle stage is scanned and driven many times in the front and back direction in order to converge the displacement of the reticle with respect to the reticle stage, the processing time becomes longer along with the scan driving. In the present invention, therefore, it is an object of the present invention to correct the displacement of the reticle accompanying the scanning drive of the reticle stage without reducing the throughput.

One aspect of the present invention is an exposure method in which the substrate is exposed while scanning an original plate and the substrate, and a recipe which defines the exposure in advance is used for the first time before the exposure is performed. the pre-drive reciprocating the査driving range run the original stage for holding the original was made by first number, when the recipe is already recipe used was only the rows second number of said previous drive is and pre-driving step Ru Align, during which the previous drive is performed by the first number in the case in the previous drive step is a recipe the recipe is first used, positional displacement amount of the original stage of the original the change is measured, a generation step of generating information indicating a relationship between the number and the positional deviation amount of the scan driver of the original stage on the basis of the result of the measurement, the original when performing the exposure And an exposure step of performing the exposure, wherein the estimation step includes the number of times of the pre-driving performed in the pre-driving step and the exposure. The position is obtained by applying the cumulative number of scan driving of the original stage determined based on the number of scan driving of the original stage performed in the step to the relation indicated by the information generated in the generation step. The amount of displacement is estimated, and the exposure step corrects the scanning of at least one of the original stage and the substrate stage holding the substrate based on the amount of displacement estimated in the estimation step. was carried out, the second number of times, the a smaller number than the first number, based on the relationship indicated by the information generated by the generating step Characterized in that it is determined Te.

  According to the present invention, it is possible to correct the displacement of the reticle accompanying the scanning drive of the reticle stage without reducing the throughput.

FIG. 2 is a view showing the arrangement of an exposure apparatus. FIG. 2 is a diagram showing the configuration of reticle alignment. 5 is a flowchart showing a flow of exposure processing. FIG. 7 is a diagram showing a flow of data regarding correction of misalignment of a reticle. 6 is a graph showing the relationship between the number of times of scan driving and the amount of positional deviation of the reticle. Correction table for misalignment of reticle.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. FIG. 1 shows the arrangement of an exposure apparatus according to the embodiment. The exposure apparatus shown in FIG. 1 includes an exposure apparatus that exposes a substrate without interposing a liquid between the projection optical system 1 and the wafer (substrate) 5, and interposing a liquid between the projection optical system 1 and the wafer 5. It may be any of the liquid immersion exposure apparatus that exposes the substrate after exposure. Hereinafter, an exposure apparatus for transferring a circuit pattern to a wafer 5 will be described using a reticle (original plate) 4 on which a circuit pattern of a semiconductor device is formed.

  The exposure apparatus shown in FIG. 1 comprises a reticle stage 6 and an illumination optical system 2 for illuminating a reticle 4 held by the reticle stage 6, a wafer stage (substrate stage) 7, and a pattern of the reticle 4 on the wafer stage 7. A projection optical system 1 for projecting on the surface 5 is provided. The exposure apparatus also includes a surface position detector 14 of the wafer 5 and a wafer alignment detector 13. The surface position detector 14 includes a light emitting unit 14 a that emits light onto the surface of the wafer 5 and a light receiving unit 19 b that receives the light reflected by the surface of the wafer 5. The exposure apparatus further includes a control unit C that controls the exposure process.

  The laser interferometer 10 measures the position of the reticle stage 6. The controller C controls an actuator that drives the reticle stage 6 to control the position of the reticle stage 6 in the Y direction. In addition to the reticle 4, a reticle reference plate 8 is disposed on the reticle stage 6. The height of the pattern surface of reticle reference plate 8 substantially matches the height of the pattern surface of reticle 4. A bar mirror 11 that reflects a beam emitted from the laser interferometer 10 is fixed to the reticle stage 6, and the position and the movement amount of the reticle stage 6 are sequentially measured by the laser interferometer 10.

  A wafer reference plate 9 is disposed on the wafer stage 7. The pattern surface of the wafer reference plate 9 substantially coincides with the height of the upper surface of the wafer 5. The wafer stage 7 can be moved in the Z direction and in the XY plane, and is further controlled by the control unit C so as to be able to finely rotate to θX, θY, θZ. Similar to the reticle stage 6, the bar mirror 11 for reflecting the beam from the laser interferometer 10 is also fixed to the wafer stage 7, and the position and the movement amount of the wafer stage 7 in the XYZ directions are successively determined by the laser interferometer 10. It is measured.

  The XYZ orthogonal coordinate system shown in FIG. 1 will be described. In the XYZ orthogonal coordinate system, the directions are determined such that the plane defined by the X direction and the Y direction is parallel to the plane of the wafer 5 and the Z direction is orthogonal to the plane of the wafer 5. The exposure apparatus shown in FIG. 1 includes a light source 3. As the light source 3, for example, a KrF excimer laser that generates light of a wavelength of 248 nm can be used, but for example, a mercury lamp, ArF excimer laser (193 nm), an EUV light source, or the like can also be adopted. The light beam emitted from the light source 3 is incident on the illumination optical system 2 and shaped into a set shape, interference property, and polarization state, and transmits and illuminates the reticle 4. The light diffracted by the delicate circuit pattern formed on the lower surface of the reticle 4 is imaged by the projection optical system 1 on the wafer 5 disposed on the wafer stage 7.

  A reticle alignment detector 12 is used to measure the misalignment of the reticle. The controller C drives the reticle stage 6 onto the reticle alignment detector 12. The reticle alignment detector 12 detects the alignment mark 16 on the reticle stage 6 and the alignment mark 15 on the reticle 4 and measures their relative positions to determine the amount of positional deviation of the reticle 4 with respect to the reticle stage 6. As shown in FIG. 2, the alignment mark 16 on the reticle stage 6 and the alignment mark 15 on the reticle 4 respectively have a plurality of marks arranged in the X direction, whereby the misalignment of the reticle 4 with respect to the reticle stage 6 in the XY.theta. Can be measured.

  A flow for exposing the wafer 5 using the exposure apparatus shown in FIG. 1 will be described with reference to FIG. At S1, the control unit C mounts the reticle 4 on the reticle stage 6 at S1. In step S2, the control unit C confirms whether the recipe defining the exposure processing is to be processed for the first time. If it is the first processing, the process proceeds to step S3 and the recipe is not to be processed for the first time, that is, If it has been processed before, the process proceeds to S4. For example, if the reticle 4 to be used is one used before, the process proceeds to S4.

  Steps S3 and S4 are steps for causing the reticle stage 6 to perform a plurality of scan driving operations for reciprocating the scanning drive range in the scanning direction (Y direction) in order to converge the occurrence of positional deviation of the reticle 4 with respect to the reticle stage 6. If the recipe is to be processed for the first time, the controller C scans and drives the reticle stage 6 for approximately 100 cycles in S3. On the other hand, if the recipe has been processed previously, the controller C scans and drives the reticle stage 6 for about 20 cycles in S4. The small number of times of scan driving in S4 is due to the fact that the positional deviation of the reticle 4 almost converges with the scan drive of about 20 reciprocations in the previous process. By reducing the number of scan drives when the recipe has been processed previously, the time required for reticle alignment measurement can be reduced.

  In step S5, the control unit C measures the amount of positional deviation of the reticle 4 from the reticle stage 6 using the reticle alignment detector 12. When the reticle stage 6 is stepwise driven to the position of the reticle alignment detector 12 in S5, the control unit C drives the reticle stage 6 with the same acceleration as the scan driving in S2 and S4 and S8 described later. In addition, after the reticle stage 6 is driven to reciprocate in the Y direction, the positional difference of the reticle 4 is measured using the reticle alignment detector 12 to thereby determine the difference in positional deviation of the reticle 4 due to driving in the forward direction and driving in the backward direction. It can also be measured.

  At S6, the control unit C mounts the wafer 5 on the wafer stage 7. At S7, the control unit C measures the surface position of the wafer 5 by the surface position detector 14. If the wafer 5 is a patterned wafer, the control unit C may measure the wafer 5 in the X and Y directions using the wafer alignment detector 13 in S7 to carry out wafer alignment.

  In step S8, the control unit C corrects positional errors of the reticle 4, the reticle stage 6, the wafer stage 7, and the projection optical system 1 based on the results of the reticle alignment measurement of S5 or immediately before the wafer S9 and the wafer alignment measurement of S7. Calculate The control unit C calculates an accurate exposure shot position from the calculation result, drives the reticle stage 6 and the wafer stage 7 step-and-scan, and corrects the imaging characteristics of the projection optical system 1. Exposure processing is sequentially performed. S8 is an exposure step of performing scanning exposure on each shot of the wafer 5.

  In step S9, the control unit C measures the positional deviation of the reticle 4 from the reticle stage 6 using the reticle alignment detector 12 as in step S5. When the reticle stage 6 is stepwise driven to the position of the reticle alignment detector 12 in S9, the control unit C drives the reticle stage 6 with the same acceleration as the scan driving in S3, S4, and S8. In the present embodiment, in addition to the reticle alignment measurement of S5, reticle alignment measurement is performed also in S9 after scan exposure on each wafer 5. S9 is a re-measurement step of re-measuring the displacement amount of the reticle 4 after the exposure step. However, the reticle alignment measurement of S9 may be omitted.

  In step S10, the control unit C unloads the wafer 5 from the wafer stage 7, and ends the series of processes for one wafer 5. In step S11, the control unit C confirms whether the exposure process for all the wafers 5 to be processed is completed. If not completed, the process returns to step S6, and the subsequent processes are repeated. End the flow

  The flow for correcting the positional deviation of the reticle 4 in the flow of the exposure processing of the wafer 5 shown in FIG. 3 will be described with reference to FIG. At S41 (S1 in FIG. 3), the control unit C mounts the reticle 4 on the reticle stage 6. At that time, the control unit C initializes the number of times of scanning drive 46 of the reticle stage 6. At S42 (S3 and S4 in FIG. 3), the controller C scans and drives the reticle stage 6 in the Y direction. The control unit C updates the number of times of scan driving 46 by the number of times of scan driving in S42. At S43 (S5 and S9 in FIG. 3), the control unit C measures the positional deviation amount 44 of the reticle 4 from the reticle stage 6 using the reticle alignment detector 12.

  In step S45, the control unit C calculates and registers the correction coefficient 47 of the positional deviation of the reticle 4 from the measurement result 44 of the positional deviation of the reticle obtained in step S43 and the number of times of scanning drive 46 of the reticle stage 6. The method of calculating the correction coefficient 47 will be described with reference to FIG. FIG. 5 is a graph showing the relationship between the number of times of scanning drive 46 of the reticle stage 6 and the displacement amount 44 of the reticle 4. When the reticle stage 6 is step-driven and scan-driven at an acceleration higher than a predetermined level, the reticle 4 is displaced in the X and Y directions. In particular, the position of the reticle 4 in the Y direction is susceptible to the scanning drive. Immediately after the reticle 4 is mounted on the reticle stage 6, the displacement amount 44 of the reticle 4 is large, and as the number of times of scanning drive 46 of the reticle stage 6 increases, the displacement amount 44 of the reticle 4 converges. The positional displacement amount 44 of the reticle 4 can be approximated by, for example, a first-order lag model equation as shown in FIG. In this case, the correction coefficient 47 is a coefficient specifying a function (curve) indicating the relationship between the reticle positional deviation amount 44 and the number of times of scanning drive 46 of the reticle stage 6 shown in FIG.

  Therefore, when the recipe is to be processed for the first time in S45 in FIG. 4, the control unit C calculates and calculates the correction coefficient 47 from the number of times of scanning drive 46 of the reticle stage 6 and the positional displacement amount 44 of the reticle 4. The correction coefficient 47 is stored in the storage unit S. In the present embodiment, the storage unit S is configured in the exposure apparatus. However, the storage unit S may be configured outside the exposure apparatus. If the recipe has been processed before, the control unit C causes the number of times of the scanning drive 46 of the reticle stage 6 and the positional deviation of the reticle 4 to occur. The correction coefficient 47 is calculated from the amount 44, and the correction coefficient 47 is updated with the calculated correction coefficient 47. The correction coefficient 47 is updated only when the difference between the correction coefficient 47 currently stored and the correction coefficient 47 calculated from the number of times of scanning drive 46 of the reticle stage 6 and the displacement amount 44 of the reticle 4 exceeds the allowable range. You may implement. S42, S43 and S46 constitute a generation step of scanning drive of the reticle stage 6 a plurality of times, measuring the amount of displacement of the reticle 4 and generating information correlating the amount of displacement with the number of times of scan driving.

  At S48 (S8 in FIG. 3), the control unit C sequentially exposes each shot while driving the reticle stage 6 and the wafer stage 7 step-and-scan. At this time, in step S50, the control unit C acquires the number of times of scanning drive 46 of the reticle stage 6 and the correction coefficient 47, and estimates the positional deviation correction value 49 of the reticle 4. S50 is an estimation step of estimating the positional displacement amount of the reticle. The controller C reflects the calculated positional deviation correction value 49 of the reticle 4 on the position of the reticle stage 6 or the wafer stage 7 at the time of scan exposure. When the positional deviation amount of the reticle 4 changes in accordance with the direction of scanning drive, the correction value to be reflected may be switched. Since the scan drive of the reticle stage 6 is performed when exposing each shot, the control unit C adds the number 46 of scan drive of the reticle stage 6 each time the scan drive is performed.

  If the wafer 5 to be processed remains, the control unit C repeatedly executes S43 and S48, and updates the correction coefficient 47 each time. When it is predicted that the positional deviation of the reticle 4 does not change, the control unit C may thin out S43 and may use the correction coefficient 47 as it is.

  In S3 and S4 of FIG. 3 and S42 of FIG. 4, the number of times of scanning and driving of the reticle stage 6 is switched on a recipe basis, but may be switched on a reticle basis. In addition, S45 of FIG. 4 and the correction coefficient 47 may be updated on a reticle basis. However, the positional deviation amount of the reticle 4 changes in accordance with the acceleration of the reticle stage 6. Therefore, switching of the number of times of scan driving in S3 and S4 of FIG. 3 and S42 of FIG. 4, calculation of the correction coefficient of S45 of FIG. 4 and update of the correction coefficient 47 are also normally performed on a recipe basis.

  In the present embodiment, the correction coefficient 47 is calculated based on the first-order lag model equation. However, correction is performed based on a table of the number of times of scanning drive 46 of the reticle stage 6 and the displacement amount 44 of the reticle 4 shown in FIG. The coefficient 47 may be calculated. Similar to FIG. 5, the correction table of FIG. 6 shows the relationship between the number of times of scanning and driving 46 of the reticle stage 6 and the positional deviation amount 44 of the reticle 4. Further, the method of measuring the positional deviation of the reticle 4 from the reticle stage 6 using the reticle alignment detector 12 is taken as an example. However, it may be a method of measuring the displacement between the alignment mark 15 on the reticle 4 and the mark on the wafer stage on the wafer reference plate 9 through the projection optical system 1. Furthermore, when the positional deviation difference between the reticles is small, the positional deviation of the reticle 4 on the reference reticle is measured to calculate the correction coefficient, and the amount of positional deviation of the other reticle is estimated from the correction coefficient of the reference reticle and corrected. You may Further, a plurality of reticles 4 used for exposure processing are grouped into a plurality of groups, a reference reticle is set corresponding to each group, a correction coefficient 47 is generated for each reference reticle, and the positional deviation amount of the reticle 4 is calculated. It may be estimated from the correction coefficient of the corresponding reference reticle.

[Device manufacturing method]
Next, a method of manufacturing devices (semiconductor devices, liquid crystal display devices, etc.) will be described. A semiconductor device is manufactured through a pre-process of forming an integrated circuit on a wafer and a post-process of completing an integrated circuit chip on the wafer made in the pre-process as a product. The pre-process includes the steps of exposing the wafer coated with the photosensitive agent using the exposure apparatus described above, and developing the wafer. The post process includes an assembly process (dicing, bonding) and a packaging process (encapsulation). A liquid crystal display device is manufactured by passing through the process of forming a transparent electrode. The process of forming a transparent electrode includes a process of applying a photosensitive agent to a glass substrate on which a transparent conductive film is deposited, a process of exposing a glass substrate coated with a photosensitive agent using the above-mentioned scanning exposure apparatus, and glass And developing the substrate. According to the device manufacturing method of the present embodiment, it is possible to manufacture a device of higher quality than the conventional one.

4: Reticle. 5: Wafer. 6: Reticle stage. 7: Wafer stage. 12: Reticle alignment detector. 13: Wafer alignment detector. 15: Alignment mark on reticle side. 16: Alignment mark on the reticle stage side. C: Control unit. S: Storage unit.

Claims (10)

An exposure method of exposing a substrate while scanning an original and a substrate,
In advance before performing the exposure, if the recipe defining the exposure is a recipe used for the first time to perform the pre-drive reciprocating the査driving range run the original stage for holding the original by a first count, the and pre-driving step of Ru to perform the previous drive by a second number of times when the recipe is already recipe used,
In the case where the recipe is a recipe used for the first time in the pre-driving step, a change in displacement amount of the original with respect to the original stage while the pre-driving is performed the first number of times is measured, A generation step of generating information indicating the relationship between the number of times of scan driving of the original plate stage and the positional displacement amount based on the measurement result;
Estimating an amount of displacement of the original plate relative to the original plate stage when the exposure is performed;
An exposure step of performing the exposure;
Have
The estimation step is an accumulation of scan driving of the original stage determined based on the number of times of the pre-driving performed in the pre-driving step and the number of scan driving of the original stage performed in the exposure step. Estimating the misregistration amount by applying the number of times to the relation indicated by the information generated in the generation step;
The exposure step performs the exposure while correcting the scanning drive of at least one of the original stage and the substrate stage holding the substrate based on the positional displacement amount estimated in the estimation step.
The second number of times is a number smaller than the first number of times, and is determined based on the relationship indicated by the information generated in the generation step.   In the generation step, the information is generated in recipe units that define the exposure, and in the estimation step, the positional deviation amount is estimated based on the information corresponding to a recipe to which the exposure follows. Item 2. An exposure method according to item 1.   2. The method according to claim 1, wherein the generation step generates the information on an original plate unit, and the estimation step estimates the displacement amount based on the information corresponding to the original plate used in the exposure. Exposure method.   The acceleration of the original plate stage in the pre-driving performed in the pre-driving step and the acceleration of the original plate stage in the scanning drive performed in the exposure step are equal to each other. The exposure method according to item 1.   The exposure method according to any one of claims 1 to 4, wherein the information is a coefficient specifying a function indicating the relationship.   The exposure method according to any one of claims 1 to 4, wherein the information is a table indicating the relationship. The method further includes a re-measuring step of re-measuring the displacement amount of the original plate to the original plate stage after performing the exposure step,
In the re-measurement process, when the difference between the re-measured displacement amount and the displacement amount estimated in the estimation step exceeds the allowable range, the information is calculated using the re-measured displacement amount. The exposure method according to any one of claims 1 to 6, wherein when the difference falls within the allowable range, the information is not updated. Exposing the substrate using the exposure method according to any one of claims 1 to 7;
Developing the exposed substrate;
And manufacturing the device using the developed substrate. An exposure apparatus that exposes a substrate while scanning an original and a substrate, and includes an original stage that holds the original, a substrate stage that holds the substrate, and a control unit that controls the exposure.
The control unit
In advance before performing the exposure, when the a recipe recipe is first used to define the exposure to perform the pre-drive reciprocating the査driving range run on the original stage by a first number of times, using the recipe already If it is a recipe that has been made, the pre-driving is performed a second number of times,
When the pre-drive is performed for the first number of times when the recipe is a recipe used for the first time, a change in displacement amount of the original plate with respect to the original plate stage is measured, and based on the measurement result Generating information indicating a relationship between the number of times of scan driving of the original stage and the positional deviation amount;
Cumulative scan drive of the original stage determined based on the number of pre-drives and the number of scan drives performed between the exposure and the displacement amount of the original with respect to the original stage when performing the exposure Estimating the number of times by fitting to the relationship indicated by the generated information;
The exposure is performed while correcting the scanning drive of at least one of the original stage and the substrate stage based on the estimated positional displacement amount.
It said second number of times, the a first fewer than the number of exposure apparatus according to claim Rukoto is determine on the basis of the relation shown by the generated information. And a storage unit for storing the information.
10. The exposure apparatus according to claim 9, wherein the control unit acquires the information from the storage unit.

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