Method for compensating glare of optical lens of exposure machine

Abstract

The invention provides a method for compensating glare of an optical lens of an exposure machine, which comprises the following steps of: placing a first wafer coated with photoresist in a first exposure machine for exposure, and ensuring that a lens of the first exposure machine is normal; developing the first wafer; selecting a plurality of first measurement points in the exposure area of the first wafer for CD measurement to obtain a first CD data set; placing the second wafer coated with the photoresist in a second exposure machine for exposure, wherein a lens glare phenomenon exists in a lens of the second exposure machine; developing the second wafer; selecting a plurality of second measurement points in the exposure area of the second wafer for CD measurement to obtain a second CD data set; fitting the difference between the first CD data set and the second CD data set into a light transmission amount; and adjusting exposure parameters of the second exposure machine according to the light transmission amount. According to the invention, the product line width difference caused by the lens glare phenomenon of the exposure machine can be improved, the exposure energy automatic compensation of the exposure machine is realized, the shot inner line width uniformity in the exposure process is ensured, and the product quality is improved.

Description

Technical Field

[0001] The present invention relates to the field of integrated circuit manufacturing, and particularly to a method for compensating for the glare of an optical lens of an exposure machine. Background Art

[0002] Integrated circuit manufacturing is a complex and precise process. Among them, lithography is an important process in integrated circuit manufacturing. Lithography is a graphic transfer technology that transfers the pattern on the mask plate to a silicon wafer coated with photoresist (or called lithography resist), and removes specific parts of the thin film on the surface of the silicon wafer through a series of production steps. Lithography technology is a key semiconductor process technology developed on the basis of borrowing photographic technology and lithography technology. The light emitted by the light source irradiates on the mask plate, and the emitted light already carries the graphic information on the mask plate. The light carrying the graphic information of the mask plate irradiates on the substrate coated with photosensitive material (lithography resist), and this process is called exposure.

[0003] During the lithography process, the organic volatiles generated by the photoresist on the surface of the silicon wafer will crystallize on the optical lens. With the accumulation of time, the increase in the crystallized substances will cause the exposure light to scatter, that is, the lens flare phenomenon. The stray light formed will affect the uniformity of the light source in the normal exposure process, cause unnecessary feature size differences, and reduce the resolution ability of the lithography machine, thereby affecting the exposure line width and the process window. Moreover, due to the existence of the lens flare phenomenon, it is necessary to frequently stop the machine for cleaning, which seriously affects the utilization rate of the machine. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for compensating for the glare of an optical lens of an exposure machine, which can improve the line width difference of the product line caused by the lens flare phenomenon due to lens contamination of the exposure machine, realize the automatic compensation of the exposure energy of the exposure machine, ensure the line width uniformity within the shot (exposure area) during the exposure process, and improve the product quality.

[0005] To achieve the above purpose, the present invention provides a method for compensating for the glare of an optical lens of an exposure machine, which includes:

[0006] Placing the first wafer coated with photoresist in the first exposure machine for exposure, and the lens of the first exposure machine is normal;

[0007] Performing a developing process on the first wafer;

[0008] Selecting a plurality of first measurement points in the exposure area of the first wafer for CD measurement to obtain a first CD data set;

[0009] Place the second wafer coated with photoresist in the second exposure machine for exposure. There is an optical lens glare phenomenon in the lens of the second exposure machine;

[0010] Develop the second wafer;

[0011] Select several second measurement points in the exposed area of the second wafer for CD measurement to obtain a second CD data set;

[0012] Fit the difference between the first CD data set and the second CD data set into the light transmission amount;

[0013] Adjust the exposure parameters of the second exposure machine according to the light transmission amount.

[0014] Optionally, the first measurement points are evenly distributed and span the exposed area of the first wafer, and the second measurement points are evenly distributed and span the exposed area of the second wafer.

[0015] Optionally, the first measurement points span the exposed area of the first wafer in a direction perpendicular to the exposure movement direction, and the second measurement points span the exposed area of the second wafer in a direction perpendicular to the exposure movement direction.

[0016] Optionally, coat the first wafer with photoresist and bake it on a spin coater / developer, and coat the second wafer with photoresist and bake it on a spin coater / developer.

[0017] Optionally, develop the first wafer on a spin coater / developer, and develop the second wafer on a spin coater / developer.

[0018] Optionally, the process conditions for developing the first wafer are the same as those for developing the second wafer.

[0019] Optionally, the positions of the first measurement points and the second measurement points in their respective exposed areas correspond one by one and are the same.

[0020] Optionally, select at least one exposed area on the first wafer. When two or more exposed areas are selected on the first wafer, take the average value of the CD data of the first measurement points at the same positions on all the exposed areas to obtain the first CD data set; similarly, select at least one exposed area on the second wafer. When two or more exposed areas are selected on the second wafer, take the average value of the CD data of the second measurement points at the same positions on all the exposed areas to obtain the second CD data set.

[0021] Optionally, adjust the exposure energy in the exposure parameters of the second exposure machine according to the light transmission amount.

[0022] Optionally, the method includes an inspection step, which includes: after adjusting the exposure parameters of the second exposure machine, placing the third wafer coated with photoresist in the second exposure machine for exposure, developing the third wafer, selecting a plurality of third measurement points in the exposed area of the third wafer for CD measurement to obtain a third CD data set, and comparing the difference between the third CD data set and the first CD data set.

[0023] With the above configuration, a plurality of first measurement points are selected in the exposed area of the first wafer for CD measurement to obtain a first CD data set, a plurality of second measurement points are selected in the exposed area of the second wafer for CD measurement to obtain a second CD data set. The first wafer is exposed using a normal lens, and the second wafer is exposed using a lens with an optical lens glare phenomenon. The present invention compares the first CD data set and the second CD data set to find the difference in the product line width caused by the normal lens and the lens with the optical lens glare phenomenon, fits the difference between the first CD data set and the second CD data set into the light transmittance, and then adjusts the exposure parameters of the second exposure machine according to the light transmittance to achieve automatic compensation of the exposure energy of the exposure machine. The present invention significantly improves the difference in the product line width caused by the lens glare phenomenon (Lens Flare) due to lens contamination of the exposure machine. Through CD data collection and processing, automatic compensation of the exposure energy of the exposure machine is achieved, ensuring the line width uniformity within the shot (exposed area) during the exposure process, improving the product quality, reducing the frequency of exposure machine downtime for cleaning, and increasing the machine utilization rate. Description of the Drawings

[0024] Those of ordinary skill in the art should understand that the provided drawings are used to better understand the present invention and do not constitute any limitation to the scope of the present invention. Among them:

[0025] Figure 1 is a schematic diagram of a method for compensating for optical lens glare of an exposure machine according to an embodiment of the present invention;

[0026] Figure 2 is a schematic diagram of the distribution of the first measurement points according to an embodiment of the present invention. Detailed Embodiments

[0027] In this article, unless otherwise specified, the terms "upper", "lower", "left", "right", "inner", "outer", "front", "rear", "top", "bottom", etc. are used to indicate the orientation or positional relationship based on the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation and operation, and thus should not be construed as a limitation to the present invention.

[0028] The specific embodiments of the present invention will be described in more detail below in conjunction with the schematic diagrams. According to the following description, the advantages and features of the present invention will be clearer. It should be noted that the drawings are all in a very simplified form and use non-precise scales, only for conveniently and clearly assisting in explaining the purpose of the embodiments of the present invention.

[0029] A key parameter characterizing integrated circuit manufacturing technology is the minimum feature size, that is, the critical dimension (CD), which is the minimum line width or pitch of some features in semiconductor devices. As the critical dimension shrinks, even down to the nanometer level, it becomes possible to have millions of devices on each chip. The present invention aims to find the differences in the line widths of the product line caused by a normal lens and a lens with optical lens glare phenomenon through CD measurement, fit the differences into the light transmission amount, and finally compensate the exposure energy of the exposure machine according to the light transmission amount.

[0030] Figure 1 is a schematic diagram of a method for compensating optical lens glare of an exposure machine according to an embodiment of the present invention. Please refer to Figure 1 An embodiment of the present invention provides a method for compensating optical lens glare of an exposure machine, including steps S1, S2, S3, S4, S5, S6, S7, and S8. The following will describe steps S1, S2, S3, S4, S5, S6, S7, and S8 in detail.

[0031] Step S1: Place the first wafer coated with photoresist in the first exposure machine for exposure, and the lens of the first exposure machine is normal. A normal lens means that there is no excessive crystallization on the lens and there is no optical lens glare phenomenon on the lens.

[0032] Furthermore, before exposure, the first wafer needs to be coated with photoresist and baked on a spin coater and developer (track machine). For example, a standard sample photoresist is spin-coated on the first wafer through the track machine and baked at an appropriate temperature.

[0033] Step S2: Develop the first wafer. Exemplarily, the first wafer is developed on a spin coater and developer (track machine).

[0034] Step S3: Select several first measurement points in the exposure area of the first wafer for CD measurement to obtain a first CD data set.

[0035] Exemplarily, reference can be made to Figure 2 , the first measurement points are evenly distributed and span the exposure area of the first wafer. Preferably, the first measurement points span the exposure area of the first wafer along the direction perpendicular to the exposure movement direction to fully reflect the line width distribution in the entire exposure area (shot).

[0036] Step S4: Place the second wafer coated with photoresist into the second exposure machine for exposure. There is an optical lens glare phenomenon in the lens of the second exposure machine. It can be understood that the first exposure machine and the second exposure machine can be the same exposure machine platform. When the lens of this exposure machine platform is normal, it serves as the first exposure machine, and when there is an optical lens glare phenomenon in the lens of this exposure machine platform, it serves as the second exposure machine; the first exposure machine and the second exposure machine can also be two platforms with the same model configuration.

[0037] Similarly, before exposure, first coat and bake the second wafer on a spin coater and developer platform (track platform). For example, spin coat a standard sample photoresist on the second wafer through the track platform and bake it at an appropriate temperature.

[0038] Step S5: Develop the second wafer. Exemplarily, develop the second wafer on a spin coater and developer platform (track platform). Moreover, the process conditions for developing the first wafer are the same as those for developing the second wafer to reduce variables. The process conditions for development can include, for example, the amount of developer, the concentration and temperature of the developer, humidity, etc.

[0039] Step S6: Select several second measurement points within the exposed area of the second wafer for CD measurement to obtain a second CD data set.

[0040] It can be understood that the positions of the first measurement points and the second measurement points in their respective exposed areas correspond one by one and are the same.

[0041] Exemplarily, the same as Figure 2 the distribution of the first measurement points, the second measurement points are evenly distributed and span the exposed area of the second wafer. Preferably, the second measurement points span the exposed area of the second wafer along a direction perpendicular to the exposure movement direction to fully reflect the line width distribution within the entire exposed area (shot).

[0042] Furthermore, select at least one exposed area on the first wafer. For example, when two or more (including two) exposed areas are selected on the first wafer, take the average value of the CD data of the first measurement points at the same positions on all exposed areas (here referring to the exposed areas on the first wafer) to obtain a first CD data set; similarly, select at least one exposed area on the second wafer. When two or more (including two) exposed areas are selected on the second wafer, take the average value of the CD data of the second measurement points at the same positions on all exposed areas (here referring to the exposed areas on the second wafer) to obtain a second CD data set.

[0043] Step S7: Fit the difference between the first CD data set and the second CD data set into the light transmittance. It can be understood that the process of difference fitting can be completed by computer software.

[0044] Step S8: Adjust the exposure parameters of the second exposure machine according to the light transmittance. Specifically, adjust the exposure energy (dose) in the exposure parameters of the second exposure machine according to the light transmittance.

[0045] Optionally, the method includes an inspection step, and the inspection step includes: after adjusting the exposure parameters of the second exposure machine, placing the third wafer coated with photoresist in the second exposure machine for exposure, developing the third wafer, selecting a plurality of third measurement points in the exposed area of the third wafer for CD measurement to obtain a third CD data set, and comparing the difference between the third CD data set and the first CD data set. It is found through experiments that there is no obvious difference between the third CD data set and the first CD data set. It can be understood that the positions of the first measurement point and the third measurement point in their respective exposed areas correspond one-to-one and are the same.

[0046] With the above configuration, a plurality of first measurement points are selected in the exposed area of the first wafer for CD measurement to obtain a first CD data set, and a plurality of second measurement points are selected in the exposed area of the second wafer for CD measurement to obtain a second CD data set. The first wafer is exposed using a normal lens, and the second wafer is exposed using a lens with an optical lens flare phenomenon. The present invention compares the first CD data set and the second CD data set to find the difference caused by the normal lens and the lens with the optical lens flare phenomenon to the product line width, fits the difference between the first CD data set and the second CD data set into the light transmittance, and then adjusts the exposure parameters of the second exposure machine according to the light transmittance to achieve automatic compensation of the exposure energy of the exposure machine. The present invention significantly improves the product line width difference caused by the lens flare phenomenon (Lens Flare) due to lens contamination of the exposure machine. Through CD data collection and processing, automatic compensation of the exposure energy of the exposure machine is achieved, ensuring the line width uniformity in the shot (exposed area) during the exposure process, improving the product quality, reducing the frequency of exposure machine downtime for cleaning, and increasing the utilization rate of the machine.

[0047] It should be noted that the references to "one embodiment", "embodiment", "specific embodiment", "some embodiments", etc. in the specification only indicate that the described embodiments may include specific features, structures or characteristics. Moreover, such phrases do not necessarily refer to the same embodiment. In addition, when a specific feature, structure or characteristic is described in combination with an embodiment, whether explicitly described or not, implementing such a feature, structure or characteristic in combination with other embodiments is within the knowledge scope of those skilled in the relevant art.

[0048] It should be noted that the various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. For the same or similar parts among the embodiments, reference can be made to each other. For the system disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple. For the relevant parts, reference can be made to the description in the method section.

[0049] It should also be noted that although the present invention has been disclosed above with preferred embodiments, the above embodiments are not intended to limit the present invention. For any person skilled in the art, without departing from the scope of the technical solution of the present invention, many possible changes and modifications can be made to the technical solution of the present invention by using the technical content disclosed above, or it can be modified into equivalent embodiments with equivalent changes. Therefore, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of protection of the technical solution of the present invention.

[0050] It should also be understood that unless otherwise specified or indicated, the terms "first", "second", "third", etc. in the specification are only used to distinguish each component, element, step, etc. in the specification, rather than to represent the logical relationship or sequential relationship, etc. between each component, element, step.

[0051] In addition, it should also be recognized that the terms described herein are only used to describe specific embodiments and are not used to limit the scope of the present invention. It must be noted that the singular forms "a" and "an" used herein and in the appended claims include plural references unless the context clearly indicates the contrary. For example, the reference to "a step" or "a device" means a reference to one or more steps or devices, and may include secondary steps and secondary devices. All conjunctions used should be understood in the broadest sense. Also, the word "or" should be understood to have the definition of logical "or", rather than the definition of logical "exclusive or", unless the context clearly indicates the contrary. In addition, the implementation of the methods and / or devices in the embodiments of the present invention may include performing the selected tasks manually, automatically, or in combination.

Claims

1. A method for compensating glare of an optical lens of an exposure machine, characterized in that: include: Placing the first wafer coated with photoresist in a first exposure machine for exposure, wherein the lens of the first exposure machine is normal; Performing a development process on the first wafer; Selecting a plurality of first measurement points in the exposure area of ​​the first wafer to perform CD measurement to obtain a first CD data set; Placing the second wafer coated with photoresist in a second exposure machine for exposure, wherein the lens of the second exposure machine has an optical lens glare phenomenon; performing a development process on the second wafer; Selecting a plurality of second measurement points in the exposure area of ​​the second wafer to perform CD measurement to obtain a second CD data set; fitting the difference between the first CD data set and the second CD data set into light transmittance; The exposure parameters of the second exposure device are adjusted according to the light transmittance.

2. The method for compensating glare of an optical lens of an exposure machine as claimed in claim 1, characterized in that: The first measurement points are evenly distributed across the exposure area of ​​the first wafer, and the second measurement points are evenly distributed across the exposure area of ​​the second wafer.

3. The method for compensating glare of an optical lens of an exposure machine as claimed in claim 2, characterized in that: The first measurement point crosses the exposure area of ​​the first wafer along a direction perpendicular to the exposure movement direction, and the second measurement point crosses the exposure area of ​​the second wafer along a direction perpendicular to the exposure movement direction.

4. The method for compensating glare of an optical lens of an exposure machine as claimed in claim 1, characterized in that: The first wafer is coated with photoresist and baked on a coating and developing machine, and the second wafer is coated with photoresist and baked on a coating and developing machine.

5. The method for compensating glare of an optical lens of an exposure machine as claimed in claim 1, characterized in that: The first wafer is subjected to a developing process on a coating and developing machine, and the second wafer is subjected to a developing process on a coating and developing machine.

6. The method for compensating glare of an optical lens of an exposure machine as claimed in claim 1, characterized in that: The process conditions for developing the first wafer are the same as the process conditions for developing the second wafer.

7. The method for compensating glare of an optical lens of an exposure machine as claimed in claim 1, characterized in that: The positions of the first measuring point and the second measuring point in their respective exposure areas correspond one to one and are the same.

8. The method for compensating glare of an optical lens of an exposure machine as claimed in claim 1, characterized in that: Selecting at least one exposure area on the first wafer, and when more than two exposure areas are selected on the first wafer, taking an average value of CD data of first measurement points at the same position on all the exposure areas to obtain the first CD data group; Similarly, at least one exposure area is selected on the second wafer. When more than two exposure areas are selected on the second wafer, the CD data of the second measurement points at the same position on all the exposure areas are averaged to obtain the second CD data group.

9. The method for compensating glare of an optical lens of an exposure machine as claimed in claim 1, characterized in that: The exposure energy in the exposure parameters of the second exposure device is adjusted according to the light transmittance.

10. The method for compensating glare of an optical lens of an exposure machine as claimed in claim 1, characterized in that: The method includes an inspection step, which includes: after adjusting the exposure parameters of the second exposure machine, placing a third wafer coated with photoresist in the second exposure machine for exposure, developing the third wafer, selecting a plurality of third measurement points in the exposure area of ​​the third wafer for CD measurement to obtain a third CD data group, and comparing the third CD data group with the first CD data group.

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