Method for eliminating non-target pattern scattering defect of mask
By adjusting the size of the exposure beam in the lithography machine, scattering defects of non-target patterns on the mask are eliminated, solving the chip defect problem caused by stray light projection, improving the lithography yield and simplifying the operation process. It is applicable to a variety of lithography machines and light sources.
Patent Information
- Application Number
- CN202512052372.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-31
- Publication Date
- 2026-02-17
AI Technical Summary
In existing projection lithography processes, stray light projection from mask markings causes non-target pattern defects, affecting chip yield. Furthermore, existing methods require re-fabricating the layout or adjusting the lithography machine's light-blocking plate, which is complex and consumes a lot of materials.
By adjusting the exposure beam size of the lithography machine, the beam opening range can be precisely adjusted according to the size deviation between the lithographic pattern and the target pattern, eliminating scattering defects of non-target patterns on the mask. This method is applicable to various wavelength light sources and lithography machine models.
It significantly improves the lithography yield, simplifies the operation process, reduces the demand for consumables, and is suitable for lithography scenarios with single or multiple chips, with strong compatibility.
Smart Images
Figure CN121541418A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of semiconductor manufacturing technology, and in particular to a method for eliminating scattering defects of non-target patterns on a photomask. Background Technology
[0002] In the manufacturing process of semiconductor devices, photolithography is one of the core key processes that determines the chip's integration, performance, and reliability. Its process precision and stability directly affect the wafer yield. As chip sizes continue to shrink, yield losses caused by process defects are becoming increasingly prominent, and have become a key bottleneck restricting the industry's development towards higher precision and higher efficiency.
[0003] Among various lithography defects, the defect where mask markings are projected onto the wafer by stray light to form non-target patterns is a common technical challenge in projection lithography applications. Masks used in projection lithography typically integrate multiple functional markings, including lithography machine identification barcodes, alignment marks, model codes, and target patterns, to ensure the smooth progress of the lithography process. However, during actual exposure, stray light from the lithography machine beam inevitably illuminates these markings. Due to the projection imaging relationship between the mask and the wafer, the markings are incorrectly projected onto the target exposure area of the wafer, forming non-target patterns. Such patterns can damage the structure and function of the chip's normal circuitry, directly leading to chip failure.
[0004] Therefore, how to effectively suppress stray light projection from mask markings to reduce chip failure risk and improve lithography yield has become a technical problem that urgently needs to be solved in this field. Summary of the Invention
[0005] In view of this, the purpose of this application is to provide a method for eliminating non-target pattern scattering defects in a photomask, thereby solving the technical problem of chip defects caused by stray light projected onto a marker in existing projection lithography processes.
[0006] To achieve the above-mentioned technical objectives, this application provides a method for eliminating scattering defects in non-target patterns on a photomask, comprising the following steps:
[0007] Step S1: Coat the silicon wafer with photoresist, place the mask with the target pattern in the photolithography machine, set the initial exposure beam size, and use the exposure beam output by the photolithography machine to expose and develop the silicon wafer coated with photoresist through the mask to obtain a silicon wafer with photolithographic pattern.
[0008] Step S2: Test the dimensions of the photolithographic pattern and calculate the dimensional deviation between the photolithographic pattern and the target pattern;
[0009] Step S3: Based on the dimensional deviation value, reduce the exposure beam size of the lithography machine, and expose and develop the silicon wafer coated with photoresist to obtain a silicon wafer with the target pattern on the surface.
[0010] Furthermore, the value of the reduced exposure beam size of the lithography machine is equal to the measured dimensional deviation between the lithographic pattern and the target pattern.
[0011] Furthermore, the photoresist can be either a positive photoresist or a negative photoresist.
[0012] Furthermore, positive photoresist is a chemically amplified photoresist composed of resin, photoacid generator, solvent, and additives.
[0013] Furthermore, the negative photoresist is a cross-linked photoresist, which is composed of an alkali-soluble resin, a cross-linking agent, a photoinitiator, and a solvent.
[0014] Furthermore, in the developing process of steps S1 and S3, a developing solution is used for developing, which is an alkaline developing solution or an organic solvent developing solution.
[0015] Furthermore, the alkaline developer is an aqueous solution of tetramethylammonium hydroxide with a mass percentage of 0.1% to 2.38%.
[0016] Furthermore, the organic solvent developer is prepared by mixing cyclohexanone and butyl acetate in a volume ratio of 1:1 to 3:1.
[0017] Furthermore, the lithography machine is a projection lithography machine.
[0018] Furthermore, the projection lithography machine includes a light source, a light shield, a marked mask, and a projection lens arranged sequentially along the optical path, and the light source, light shield, marked mask, and projection lens are arranged collinearly along the central axis.
[0019] In summary, this application provides a method for eliminating scattering defects caused by non-target patterns on a photomask, comprising the following steps: coating a silicon wafer surface with photoresist; placing a photomask with the target pattern in a photolithography machine; setting the initial exposure beam size; using the exposure beam output by the photolithography machine to expose the photoresist-coated silicon wafer through the photomask; performing development after exposure to obtain a silicon wafer with a photosensitive pattern; testing the size of the photosensitive pattern and calculating the size deviation between the photosensitive pattern and the target pattern; based on the size deviation, reducing the exposure beam size of the photolithography machine, and performing exposure and development on the photoresist-coated silicon wafer to obtain a silicon wafer with the target pattern on its surface. This invention, by precisely adjusting the exposure beam size of the photolithography machine, can effectively weaken the scattered light generated by non-target patterns (markers) on the photomask, thereby eliminating the resulting photolithography defects and significantly improving the yield. Furthermore, the present invention has a wide range of applications, not only applicable to lithography scenarios where a single exposure field corresponds to a single chip, but also suitable for application scenarios where a single exposure field corresponds to multiple chips; and in terms of equipment compatibility, it is not limited by the wavelength of the lithography machine's light source, and can be adapted to multiple wavelength light sources such as I-LINE and DUV, and is applicable to all types of projection lithography machines.
[0020] Compared with existing technologies, the method provided by this invention does not require re-fabricating the layout or adjusting the range of the light-blocking plate of the lithography machine. It can directly and efficiently reduce stray light in the beam by simply adjusting the beam opening range of the lithography machine. The operation is simple and requires no additional consumables. Attached Figure Description
[0021] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0022] Figure 1 This is a path diagram of stray light in existing projection lithography processes;
[0023] Figure 2 This is a schematic diagram of the structure of the mask with the target pattern in Example 1;
[0024] Figure 3 A schematic diagram showing that the actual exposure beam size is larger than the set exposure beam size in Example 1;
[0025] Figure 4 This is a schematic diagram illustrating the dimensional deviation between the photolithographic pattern and the target pattern provided in Example 1.
[0026] Figure 5The circuit test results are for the silicon wafer with the target pattern on its surface in Example 1;
[0027] Figure 6 The circuit test results are for the silicon wafer with surface pattern defects in Comparative Example 1. Detailed Implementation
[0028] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments in this application specification, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection claimed in this application.
[0029] In the description of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating the orientation or positional relationship shown, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.
[0030] Unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.
[0031] The raw materials used in this invention are not particularly restricted in their source; they can be purchased on the market or prepared using conventional methods known to those skilled in the art.
[0032] This application provides a method for eliminating scattering defects in non-target patterns on a photomask, including the following steps:
[0033] Step S1: Coat the silicon wafer with photoresist, place the mask with the target pattern in the photolithography machine, set the initial exposure beam size, and use the exposure beam output by the photolithography machine to expose and develop the silicon wafer coated with photoresist through the mask to obtain a silicon wafer with photolithographic pattern.
[0034] Step S2: Test the dimensions of the photolithographic pattern and calculate the dimensional deviation between the photolithographic pattern and the target pattern;
[0035] Step S3: Based on the dimensional deviation value, reduce the exposure beam size of the lithography machine, and expose and develop the silicon wafer coated with photoresist to obtain a silicon wafer with the target pattern on the surface.
[0036] It should be noted that in existing projection lithography processes, there is often a problem where stray light can cause chip defects due to projection onto the marking area. The path of the stray light is as follows: Figure 1 As shown, this invention effectively reduces scattered light from non-target patterns (markers) on the photomask by precisely adjusting the size of the exposure beam in the photolithography machine, thereby eliminating lithography defects and significantly improving yield.
[0037] In some embodiments, the reduced size of the lithography exposure beam is equal to the measured dimensional deviation between the lithographic pattern and the target pattern.
[0038] In some embodiments, the photoresist is a positive photoresist or a negative photoresist.
[0039] In some embodiments, the positive photoresist is a chemically amplified photoresist composed of resin, photoacid generator, solvent, and additives, the additives including quenchers for inhibiting acid diffusion. In some specific embodiments, the positive photoresist is MIR701 photoresist.
[0040] In some embodiments, the negative photoresist is a cross-linked photoresist, which is composed of an alkali-soluble resin, a cross-linking agent, a photoinitiator, and a solvent.
[0041] In some embodiments, during the development process in steps S1 and S3, a developing solution is used for the development operation. The developing solution is an alkaline developing solution or an organic solvent developing solution.
[0042] In some embodiments, the alkaline developer is an aqueous solution of tetramethylammonium hydroxide with a mass percentage of 0.1% to 2.38%.
[0043] In some embodiments, the organic solvent developer is prepared by mixing cyclohexanone and butyl acetate in a volume ratio of 1:1 to 3:1.
[0044] In some embodiments, the lithography machine is a projection lithography machine.
[0045] In some embodiments, a projection lithography machine includes a light source, a light shield, a marked mask, and a projection lens arranged sequentially along the optical path, and the light source, light shield, marked mask, and projection lens are arranged collinearly along the central axis.
[0046] The applicant further provides the following specific embodiments to describe the present invention. It should be noted that these embodiments are merely descriptive and do not limit the present invention in any way.
[0047] Example 1
[0048] This embodiment provides a method for eliminating scattering defects in non-target patterns on a photomask, the specific steps of which are as follows:
[0049] Step S1: Take a clean silicon wafer and coat it with a 3.6-micrometer-thick layer of MIR701 photoresist. The photosensitive wavelength of the MIR701 photoresist is matched to that of the photolithography machine. Figure 2 The mask with the target pattern shown is placed in a photolithography machine. The target pattern has a size of 20360 micrometers * 28830 micrometers.
[0050] Step S2: Set the exposure program. In the BLIND parameter field, set the exposure beam size to 10180 μm × 19220 μm. The measured actual exposure size is larger than the set exposure beam size. Figure 3 As shown;
[0051] Step S3: In the BLIND parameter field, reset the exposure beam size to 20360 μm * 28830 μm, the exposure energy to 800 mesc, and the focal length to 0, and perform the exposure process; after the exposure is completed, use a 2.38% tetramethylammonium hydroxide solution as the developer to perform an 80-second development operation on the silicon wafer.
[0052] Step S4, after development is complete, the result is as follows: Figure 4 The photolithographic pattern shown was found to be larger than the target pattern size, and the relative margins of the photolithographic pattern and the target pattern deviated by 150 micrometers.
[0053] Step S5: To address the aforementioned deviation, repeat steps S1 and S3, and adjust the exposure beam size setting in the BLIND parameters. Reduce the relative margins of a set that deviates from the target pattern by 150 micrometers. The adjusted exposure beam size is 20060 micrometers × 28830 micrometers. After exposure and development, a silicon wafer with the target pattern is obtained. Circuit testing is then performed on the silicon wafer with the target pattern. Figure 5 It can be seen that the edges of the chip circuit lines are smooth and the graphic size is accurate, indicating that there is no stray light interference during the exposure process and the development effect is uniform and controllable.
[0054] Comparative Example 1
[0055] This comparative example provides a projection lithography process, the specific steps of which are as follows:
[0056] Step S1: Take a clean silicon wafer and coat it with a 3.6-micrometer-thick layer of MIR701 photoresist. The photosensitive wavelength of the MIR701 photoresist is matched to that of the photolithography machine. Figure 2The mask with continuous patterns shown is placed in a photolithography machine. The pattern size on the mask is 20360 micrometers * 28830 micrometers.
[0057] Step S2: Set the exposure program. In the BLIND parameters, preset the exposure size to 20360 μm * 28830 μm, the exposure energy to 800 mesc, and the focal length to 0, and perform the exposure process. After exposure, use a 2.38% (w / w) tetramethylammonium hydroxide solution as the developer and perform a development operation on the silicon wafer for 80 seconds. After development, a silicon wafer with surface pattern defects is obtained, and the photolithographic pattern size is larger than the target pattern. Circuit testing is then performed on the silicon wafer with surface pattern defects. Figure 6 It can be seen that the edges of the chip circuit are blurred, raised, or expanded, indicating that the size of the photolithographic pattern is larger than the target pattern due to stray light interference during the exposure process.
[0058] The above are merely preferred embodiments of this application and are not intended to limit the present invention. Although this application has been described in detail with reference to examples, those skilled in the art can still modify the technical solutions described in the foregoing examples or make equivalent substitutions for some of the technical features. However, any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.
Claims
1. A method for eliminating scattering defects in non-target patterns on a photomask, characterized in that, Includes the following steps: Step S1: Coat the silicon wafer with photoresist, place the mask with the target pattern in the photolithography machine, set the initial exposure beam size, and use the exposure beam output by the photolithography machine to expose and develop the silicon wafer coated with photoresist through the mask to obtain a silicon wafer with photolithographic pattern. Step S2: Test the dimensions of the photolithographic pattern and calculate the dimensional deviation between the photolithographic pattern and the target pattern; Step S3: Based on the dimensional deviation value, reduce the exposure beam size of the lithography machine, and expose and develop the silicon wafer coated with photoresist to obtain a silicon wafer with the target pattern on the surface.
2. The method for eliminating scattering defects of non-target patterns in a photomask according to claim 1, characterized in that, The value of the reduced exposure beam size of the lithography machine is equal to the measured size deviation between the lithographic pattern and the target pattern.
3. The method for eliminating scattering defects of non-target patterns in a photomask according to claim 1, characterized in that, The photoresist is either a positive photoresist or a negative photoresist.
4. The method for eliminating scattering defects of non-target patterns in a photomask according to claim 3, characterized in that, The positive photoresist is a chemically amplified photoresist, which is composed of resin, photoacid generator, solvent and additives.
5. The method for eliminating scattering defects of non-target patterns in a photomask according to claim 3, characterized in that, The negative photoresist is a cross-linked photoresist, which is composed of an alkali-soluble resin, a cross-linking agent, a photoinitiator, and a solvent.
6. The method for eliminating scattering defects of non-target patterns in a photomask according to claim 2, characterized in that, In the developing process of steps S1 and S3, a developing solution is used for developing, which is an alkaline developing solution or an organic solvent developing solution.
7. The method for eliminating scattering defects of non-target patterns in a mask according to claim 6, characterized in that, The alkaline developing solution is an aqueous solution of tetramethylammonium hydroxide with a mass percentage of 0.1% to 2.38%.
8. The method for eliminating scattering defects of non-target patterns in a mask according to claim 6, characterized in that, The organic solvent developer is prepared by mixing cyclohexanone and butyl acetate in a volume ratio of 1:1 to 3:
1.
9. The method for eliminating scattering defects of non-target patterns in a photomask according to claim 1, characterized in that, The lithography machine is a projection lithography machine.
10. The method for eliminating scattering defects of non-target patterns in a mask according to claim 9, characterized in that, The projection lithography machine includes a light source, a light shield, a marked mask, and a projection lens arranged sequentially along the optical path, and the light source, light shield, marked mask, and projection lens are arranged collinearly along the central axis.