Preparation method and apparatus for phase-shift photomask, and photolithography method

Abstract

A preparation method and apparatus for a phase-shift photomask, and a photolithography method. The preparation method for a phase-shift photomask comprises: performing critical dimension (CD) measurement on a structure obtained after a first etching layer is etched (S501); on the basis of CD measurement analysis, obtaining a measurement result (S502); and on the basis of the measurement result, adjusting process parameters, etching a second etching layer and performing CD measurement, and obtaining a target phase-shift photomask (S503). By means of optimizing processes, CD measurement is added after a first etching layer is etched, such that CD errors can be found in a timely manner, and the CDs of a phase-shift photomask pattern can also be adaptively adjusted by means of dynamically adjusting an etching formula, thus effectively preventing CD errors in the front end of line from being passed backward, and ultimately improving the dimension accuracy of a phase-shift photomask. There is no need to re-update all manufacturing process conditions to make repeated attempts at preparation, application, etc., when the VTT performance of the CDs of the phase-shift photomask pattern is poor as in the prior art.

Description

Phase-shift photomask preparation method, device and photolithography method Technical Field

[0001] The present application relates to the field of semiconductor manufacturing technology, and in particular to a method and device for preparing a phase-shift photomask, and a photolithography method. Background Art

[0002] Photomasks are an essential tool in the chip manufacturing process, primarily assisting in forming the desired chip patterns. Photomasks primarily include binary photomasks and phase-shift photomasks. With the advancement of science and technology, chip precision requirements have increased, and so have the requirements for photomask pattern dimensional accuracy, particularly for phase-shift photomasks used in high-precision chip manufacturing.

[0003] Critical dimension measurement is used to precisely control product line widths, etc. Critical dimensions can be used to determine the instability of key links in the semiconductor manufacturing process. The dimensional accuracy of the critical dimension (CD) of the pattern in the phase-shift photomask will affect the dimensional accuracy of the pattern during the chip manufacturing process, thereby affecting the yield of chip production.

[0004] Therefore, a new solution for preparing and applying a phase-shift photomask is needed.

[0005] Summary of the Invention

[0006] In view of this, embodiments of the present disclosure provide a method and apparatus for preparing a phase-shift photomask and a photolithography method.

[0007] The embodiments of this specification provide the following technical solutions:

[0008] The embodiment of this specification provides a method for preparing a phase-shift photomask, and the method for preparing the phase-shift photomask includes:

[0009] Performing critical dimension measurement on the structure after etching the first etching layer;

[0010] Obtaining measurement results based on the critical dimension measurement analysis;

[0011] According to the measurement results, the process parameters are adjusted, the second etching layer is etched and critical dimension measurement is performed, and a target phase-shift photomask is obtained.

[0012] The embodiment of this specification further provides a phase-shift photomask manufacturing device, the phase-shift photomask manufacturing device comprising:

[0013] A measurement module, used for measuring the key dimensions of the structure after etching the first etching layer;

[0014] An analysis module, configured to obtain measurement results based on the critical dimension measurement analysis;

[0015] The adjustment module is used to adjust the process parameters according to the measurement results, etch the second etching layer and perform critical dimension measurement, and obtain a target phase-shift photomask.

[0016] The embodiments of this specification also provide a photolithography method, which uses the phase-shift photomask described in any of the solutions provided in the embodiments of this specification to perform photolithography on a wafer to obtain a target pattern.

[0017] Compared with the prior art, the at least one technical solution adopted in the embodiments of this specification can achieve the following beneficial effects:

[0018] By optimizing the process and adding CD measurement after etching the first etch layer, the embodiments of this specification not only detect CD errors promptly but also dynamically adjust the etching recipe to adapt the critical dimensions of the phase-shift photomask pattern. This effectively prevents CD errors from propagating to the downstream process, ultimately improving the dimensional accuracy of the phase-shift photomask. This eliminates the need to repeatedly update all manufacturing process conditions and conduct repeated trials to prepare and apply the phase-shift photomask pattern when the VTT performance of the critical dimension of the phase-shift photomask pattern is poor, as in the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0020] FIG1 is a schematic diagram of CD error propagation from the front layer to the back layer in the prior art;

[0021] FIG2 is a schematic diagram of a method A for adjusting a small VTT according to an embodiment of the present invention;

[0022] FIG3 is a schematic diagram of a method B for adjusting a large VTT according to an embodiment of the present invention;

[0023] FIG4 is a schematic diagram showing how different formulation ratios improve VTT performance according to an embodiment of the present invention;

[0024] FIG5 is a flow chart of a method for preparing a phase-shift photomask provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0025] The embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0026] The following describes the embodiments of the present application through specific examples, and those skilled in the art can easily understand other advantages and effects of the present application from the contents disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The present application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that, in the absence of conflict, the features in the following embodiments and embodiments can be combined with each other. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of this application.

[0027] It should be noted that various aspects of the embodiments within the scope of the appended claims are described below. It should be apparent that the aspects described herein can be embodied in a wide variety of forms, and any specific structure and / or function described herein is merely illustrative. Based on this application, it should be understood by those skilled in the art that an aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number and aspect described herein can be used to implement an apparatus and / or practice a method. In addition, other structures and / or functionalities other than one or more of the aspects described herein can be used to implement this apparatus and / or practice this method.

[0028] It should also be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present application. The illustrations only show components related to the present application and are not drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component can be changed at will, and the component layout type may also be more complicated.

[0029] Additionally, in the following description, specific details are provided to provide a thorough understanding of the examples, however, one skilled in the art will appreciate that the examples can be practiced without these specific details.

[0030] As chip precision requirements increase, the pattern size of the photomask will affect the dimensional accuracy of the pattern during chip manufacturing, thereby affecting the yield of chip production.

[0031] The inventors have discovered that current phase-shift photomasks are manufactured using fixed development and etching process conditions and procedures. If the CD measurement results (VTT) are poor, this cannot be detected promptly, necessitating the re-updating of process conditions for mask preparation and verification. As shown in Figure 1, after etching the first etch layer, the actual CD often differs from the target CD. This causes the CD error after etching the first etch layer to propagate to subsequent etch layers, resulting in poor final VTT performance for the phase-shift photomask. As shown in Figure 1A, the actual CD is smaller than the target CD. As shown in Figure 1B, the actual CD is larger than the target CD.

[0032] Based on this, the embodiments of this specification propose a method for preparing a phase-shift photomask: Research has found that the dimensional progress of a phase-shift photomask is primarily determined by the exposure, development, and etching processes during the preparation process. The exposure and development processes primarily affect the initial CD performance of the pattern, while the development process transmits the initial CD to the subsequent etching process. The embodiments of this specification optimize the process by adding CD measurement after etching the first etch layer to determine the etching effect and adjust the CD direction, preventing CD errors from the previous process from being propagated backwards. Furthermore, a recipe for adjusting the CD direction is configured when etching the next etch layer. This effectively prevents CD errors from being propagated backwards during the previous process, ultimately improving the dimensional accuracy of the phase-shift photomask.

[0033] The preparation method of the phase-shift photomask of the embodiment of this specification can not only detect CD errors in a timely manner, but also adapt and adjust the critical dimensions of the phase-shift photomask pattern by dynamically adjusting the etching recipe. There is no need to re-update all manufacturing process conditions and repeatedly try to prepare and apply the phase-shift photomask when the VTT performance of the critical dimensions of the phase-shift photomask pattern is poor, as in the prior art.

[0034] The following describes the technical solutions provided by various embodiments of the present application in conjunction with the accompanying drawings.

[0035] As shown in Figure 5, the method for preparing a phase-shift photomask according to an embodiment of the present specification includes steps S501 to S503. In S501, critical dimension measurements are performed on the structure after etching the first etch layer. In S502, measurement results are obtained based on the critical dimension measurement analysis. In S503, process parameters are adjusted based on the measurement results, and the second etch layer is etched and critical dimension measurements are performed to obtain the target phase-shift photomask.

[0036] The main process flow for preparing a phase-shift photomask in the prior art is fixed as follows: exposure, development, chromium (chrome, Cr) layer etching, molybdenum silicide (MoSi) layer etching, photoresist strip removal, secondary coating, secondary exposure, secondary development, secondary Cr etching, secondary photoresist removal, and CD measurement.

[0037] Research has found that its dimensional accuracy, or VTT, is primarily determined by the exposure, development, and etching processes during the fabrication process. The exposure and development processes primarily affect the initial CD performance during the graphic process, while the development process transmits this initial CD performance to the subsequent etching process. Therefore, to promptly detect and correct CD performance during etching, CD measurement is added after the first etch layer is etched to determine the etching results. If the VTT performance is good, etching of subsequent layers is continued; if the VTT performance is poor, the subsequent etching recipe is adjusted based on the CD performance. This targeted CD adjustment effectively prevents CD errors from the previous process from being transmitted to subsequent processes, thereby improving the dimensional accuracy of the phase-shift photomask.

[0038] Specifically, in the embodiments of this specification, the first etching layer and the second etching layer are used only to distinguish similar objects, and the order of the etching layers need not be described in detail. The first etching layer can represent the current etching layer, and the second etching layer can represent the next etching layer or the next etching layers. The first etching layer can represent the previous etching layer, and the second etching layer can represent the current etching layer or the current etching layers, etc.

[0039] The embodiments of this specification illustrate the preparation of the above-mentioned prior art phase-shift photomask.

[0040] Compared with the fixed etching process flow in the prior art in step S501, the embodiment of this specification adds CD measurement after etching the first etching layer, and adaptively adjusts the etching of subsequent layers by determining the accuracy of the first etching layer.

[0041] In step S502 , a measurement result is obtained based on critical dimension measurement analysis.

[0042] In combination with the above embodiment, after etching the first etch layer, critical dimension measurement and analysis are performed to obtain measurement results, such as accuracy or inaccuracy. If the measurement result is inaccurate, the subsequent etching is adjusted to prevent CD errors from being transmitted to the next etch layer.

[0043] In step S503 , the process parameters are adjusted according to the measurement results, the second etching layer is etched and critical dimension measurement is performed, and a target phase-shift photomask is obtained.

[0044] In combination with the above embodiment, if the CD measurement result of the first etch layer is inaccurate, it is discovered in time and corrected by adjusting the process parameters and etching the second etch layer to prevent the error from being transmitted. Finally, the accuracy of the target phase-shift photomask is determined through the final CD measurement step, as shown in Figure 2 or Figure 3.

[0045] As shown in Figure 2, the measurement result of the first etch layer is inaccurate. For example, if the VTT is too small, in order to prevent the CD error from continuing to propagate, the CD error is corrected in time by adjusting the subsequent etching recipe. For example, if the etching recipe has strong vertical etching ability and weak side etching ability, targeted optimization can be performed to improve the dimensional accuracy of the phase-shift photomask.

[0046] As shown in Figure 3, the measurement result of the first etch layer is inaccurate. For example, if the VTT is too large, in order to prevent the CD error from continuing to propagate, the CD error is corrected in time by adjusting the subsequent etching recipe. For example, if the etching recipe has strong side etching ability and weak vertical etching ability, targeted optimization can be performed to improve the dimensional accuracy of the phase-shift photomask.

[0047] In some embodiments, the process parameters are adjusted according to the measurement results, including: adjusting the process parameters according to the vertical etching conditions and side etching conditions after etching the first etching layer to obtain an etching recipe for the second etching layer; wherein the measurement results include the vertical etching conditions and side etching conditions of the structure after etching the first etching layer.

[0048] The measurement results of the structure after etching the first etch layer include vertical etching conditions and side etching conditions, specifically including accurate vertical etching, inaccurate vertical etching, accurate side etching, and inaccurate side etching. In combination with the above embodiment, in the event of inaccurate CD measurement results after etching the first etch layer, the vertical etching conditions and side etching conditions described above can be obtained. In order to prevent CD errors from being transmitted backward, the process parameters are adjusted to obtain an etching recipe for the second etch layer. This allows for timely adjustment of subsequent etching to adjust the CD of the pattern and optimize VTT.

[0049] In some embodiments, the method for preparing a phase-shift photomask further includes: obtaining the offset trends corresponding to the vertical etching conditions and the side etching conditions respectively, adjusting the process parameters according to the offset trends, and obtaining an etching recipe; wherein the offset trends include a first offset trend and a second offset trend.

[0050] In combination with the above embodiment, the offset trends corresponding to the vertical etching situation and the side etching situation are obtained, wherein the offset trends include a first offset trend such as weak etching and a second offset trend such as strong etching.

[0051] Combining the above measurement results, we can obtain the offset trends corresponding to the vertical etching and side etching, such as strong vertical etching and weak side etching. Based on the offset trends, we can adjust the process parameters to obtain the etching recipe for the subsequent etching layer.

[0052] In some embodiments, the method for preparing a phase-shift photomask further includes: determining priority levels of vertical etching and side etching corresponding to offset trends; and obtaining an etching recipe based on the etching condition corresponding to the offset trend with a higher priority level.

[0053] In combination with the above embodiments, the priority level of the offset trend is obtained according to the first offset trend or the second offset trend, such as high priority level for weak etching and high priority level for weak vertical etching, and then the etching recipe is obtained according to the etching conditions corresponding to the offset trend with high priority level.

[0054] For example, if the vertical etching is strong and the side etching is weak, or the vertical etching is weak and the side etching is strong, the priority of the weak vertical etching and strong side etching is higher, and the adjusted etching formula is obtained according to the weak vertical etching and strong side etching.

[0055] In some embodiments, process parameters include RF energy, gas ratio, and etching time. The method for preparing a phase-shift photomask further includes adjusting the process parameters based on measurement results to obtain different etching recipes. RF energy includes source power and bias power; the source power ranges from 100-500W, and the bias power ranges from 0-100W. Plasma etching gases include oxygen, hydrogen, argon, and carbon tetrafluoride.

[0056] In combination with the above embodiments, by measuring the CD of the structure after etching the first etch layer, different photolithography recipes, such as recipe A, recipe B,... recipe Y, are obtained by adjusting at least one of the above process parameters based on the measurement results; thereby preventing the CD error etched in the first etch layer from continuing to be transmitted to subsequent etch layers.

[0057] In some embodiments, the method for preparing the phase-shift photomask further includes: adjusting process parameters according to vertical etching conditions to obtain a first etching recipe, and adjusting process parameters according to side etching conditions to obtain a second etching recipe.

[0058] In conjunction with the above embodiments, based on the vertical etching condition, such as weak vertical etching, the process parameters can be adjusted to obtain a first etching recipe with strong vertical etching capability, such as A1; based on the vertical etching condition, such as strong vertical etching, the process parameters can be adjusted to obtain a first etching recipe with weak vertical etching capability, such as A2. Based on the side etching condition, such as weak side etching, the process parameters can be adjusted to obtain a second etching recipe with strong side etching capability, such as B1; based on the side etching condition, such as strong side etching, the process parameters can be adjusted to obtain a second etching recipe with weak side etching capability, such as B2.

[0059] In some embodiments, process parameters are adjusted based on the vertical and side etching conditions to obtain a new etching recipe. Different etching recipes have different etching effects. For example, the first etching recipe A after comprehensive analysis has strong vertical etching ability but weak side etching ability. Another example is the second etching recipe B after comprehensive analysis, which has weak vertical etching ability but strong side etching ability.

[0060] In some embodiments, the method for preparing the phase-shift photomask further includes: adjusting the ratio of the first etching recipe and the second etching recipe to obtain a third etching recipe.

[0061] In combination with the above embodiment, the first etching recipe is such as recipe A, and the second etching recipe is such as recipe B. By adjusting the different ratios of recipe A and recipe B, a third etching recipe is obtained.

[0062] For example, by adjusting the etching time, for example, the etching time of the first etching recipe A is 20S, and the etching time of the second etching recipe B is 10S, a third etching recipe is obtained.

[0063] For another example, by adjusting the etching radio frequency energy, the radio frequency energy in the first etching recipe A and the second etching recipe B is adjusted to obtain a third etching recipe.

[0064] For another example, by adjusting the gas ratio, the ratio of plasma gas in the first etching recipe A and the second etching recipe B is increased, such as increasing the ratio of carbon tetrafluoride in the first etching recipe A and increasing the ratio of argon in the second etching recipe B.

[0065] As shown in Figure 4, the result of the first etch layer measurement is inaccurate. If VTT < 0, in order to avoid the CD error from continuing to propagate, the CD error is corrected in time by adjusting the subsequent etching recipe. Specifically, the first etching recipe A and the second etching recipe B are adjusted to different ratios to obtain the etching recipe A. m +B n or A n +B m , targeted optimization to improve the dimensional accuracy of the phase-shift photomask. Among them, m and n are specifically defined according to the actual etching conditions.

[0066] The embodiments of this specification optimize the process flow and add CD measurement after etching the first etch layer. This not only allows timely detection of CD measurement deviations, but also allows timely adjustment of the etching recipes of subsequent etch layers and adaptive etching to promptly correct CD errors, thereby improving VTT in a targeted manner, enhancing the accuracy of the phase-shift photomask, and thereby improving product yield.

[0067] In combination with the above embodiment, the radio frequency energy in the preparation process of the phase-shift photomask includes source power and bias power, the source power is 100-500W, and the bias power is 0-100W.

[0068] The embodiments of this specification optimize the process flow to appropriately split the fixed development and etching process flow and add AEI (afer etch inspection, referring to the CD after etching) measurement after the Cr layer is etched to accurately determine the CD adjustment direction. The optimized etching recipe (different ratios of A+B) is used to perform targeted CD adjustment, effectively preventing the CD error of the front-end process from being transmitted to the back-end, thereby optimizing VTT and improving the dimensional accuracy of the phase-shift photomask.

[0069] In combination with the above embodiments, an embodiment of this specification provides a phase-shift photomask manufacturing apparatus, the phase-shift photomask manufacturing apparatus comprising:

[0070] A measurement module, used for measuring the key dimensions of the structure after etching the first etching layer;

[0071] Analysis module, used to obtain measurement results based on key dimension measurement analysis;

[0072] The adjustment module is used to adjust the process parameters according to the measurement results, etch the second etching layer and perform critical dimension measurement, and obtain the target phase-shift photomask.

[0073] The embodiments of this specification also provide a photolithography method, which uses the phase-shift photomask in any of the above technical solutions to perform photolithography on a wafer to obtain a target pattern.

[0074] The same and similar parts between the various embodiments in this specification can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the product embodiments described later, since they correspond to the methods, the description is relatively simple, and the relevant parts can be referred to the partial description of the system embodiment. The above is only a specific implementation method of the present application, but the scope of protection of the present application is not limited to this. Any changes or replacements that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed in this application should be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

Claims

1. A method for preparing a phase-shifting photomask, characterized in that The method for preparing the phase shift photomask template includes: Performing critical dimension measurement on the structure after etching the first etching layer; Obtaining a measurement result according to the critical dimension measurement analysis; Adjusting process parameters according to the measurement result, etching the second etching layer and performing critical dimension measurement, and obtaining a target phase shift photomask template.

2. The method for preparing a phase shift photomask according to claim 1, wherein The adjusting process parameters according to the measurement result includes: Adjusting process parameters according to the vertical etching situation and the side etching situation of the structure after etching the first etching layer, and obtaining an etching recipe for the second etching layer; The measurement result includes the vertical etching situation and the side etching situation of the structure after etching the first etching layer.

3. The method for preparing a phase shift photomask according to claim 2, wherein The method for preparing the phase shift photomask template further includes: Respectively obtaining the offset trends corresponding to the vertical etching situation and the side etching situation, and adjusting process parameters according to the offset trends to obtain an etching recipe; wherein, the offset trends include a first offset trend and a second offset trend.

4. The method for preparing a phase-shifting photomask according to claim 3, wherein, The method for preparing the phase shift photomask template further includes: Determining the priority levels of the offset trends corresponding to the vertical etching situation and the side etching situation respectively; Obtaining an etching recipe according to the etching situation corresponding to the offset trend with a higher priority level.

5. The preparation method of the phase-shifting photomask template according to claim 1, characterized in that, The process parameters include: radio frequency energy, gas ratio and etching time; The method for preparing the phase shift photomask template further includes: Adjusting each process parameter according to the measurement result to obtain different etching recipes.

6. The method for preparing a phase-shifting photomask according to claim 2, characterized in that, The method for preparing the phase shift photomask template further includes: Adjusting process parameters according to the vertical etching situation to obtain a first etching recipe; Adjusting process parameters according to the side etching situation to obtain a second etching recipe.

7. The method for preparing a phase shift photomask according to claim 6, characterized in that, The method for preparing the phase shift photomask template further includes: Adjusting the ratio of the first etching recipe and the second etching recipe to obtain a third etching recipe.

8. The method for preparing a phase shift photomask according to claim 5, characterized in that, The source power is 100 - 500W, and the bias power is 0 - 100W.

9. A preparation device for a phase shift photomask, characterized in that, The device for preparing the phase shift photomask template includes: A measurement module for performing critical dimension measurement on the structure after etching the first etching layer; An analysis module for obtaining a measurement result according to the critical dimension measurement analysis; An adjustment module for adjusting process parameters according to the measurement result, etching the second etching layer and performing critical dimension measurement, and obtaining a target phase shift photomask template.

10. A lithography method, characterized in that, Performing photolithography on a wafer using the phase shift photomask template according to any one of claims 1 - 8 to obtain a target pattern.

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