Compensation method for dodging compound eye of photoetching machine illumination system

Abstract

The invention discloses a compensation method for compound eye dodging of a photoetching machine illumination system in the technical field of photoetching machine illumination dodging. The compensation method comprises the following steps: measuring initial illuminance distribution on a wafer surface of a photoetching machine; according to expected wafer surface illuminance distribution, combining the initial illuminance distribution, and calculating transmittance distribution of each small grid area on the dodging compensating mirror to be manufactured through a pre-compensation model; according to the transmittance distribution, determining corresponding micro-point density distribution in each small grid area; the dodging compensating mirror is manufactured based on the micro-point density distribution, so that each small grid area has corresponding micro-point distribution; and the manufactured dodging compensating mirror is installed on the incident plane of a second fly's-eye lens of the illumination system, and the alignment mark on the dodging compensating mirror is made to be aligned with the boundary of the fly's-eye lens. According to the invention, the dodging compensation mirror is designed and placed on the incident plane of the second fly's-eye lens of the photoetching machine, and the installation process is simplified by using the cross alignment mark, so that efficient and convenient dodging compensation is realized.

Description

Technical Field

[0001] This invention relates to a compensation method for uniform illumination of the compound eye in a lithography machine illumination system, belonging to the field of lithography machine illumination uniform illumination technology. Background Technology

[0002] In lithography machine illumination systems, uniform illumination is a key technology for ensuring consistent linewidth in the fabricated lines. To ensure that the linewidth meets the design specifications of the lithography machine, homogenizing elements such as integrating bars, diffractive optical elements, or lens arrays are often used in the illumination system. The integral uniformity of the illumination light field is a critical indicator because the exposure dose at any point within the silicon wafer is the integrated energy of the illumination light field along the scanning direction. The integral uniformity of the illumination directly affects the feature size uniformity of the lithography machine.

[0003] In existing technologies, when a lithography machine exceeds its service life (i.e., components exceed their lifespan), the transmittance of lenses and films in the illumination system deteriorates with prolonged irradiation, leading to a decrease in the uniformity of the integrated illumination light field. For example, in a lithography machine's illumination system, the laser beam emitted by the laser is expanded and collimated before being homogenized by two compound eye lenses; however, due to the aging of optical components and films, the uniformity of the homogenized light does not meet process requirements, resulting in uneven light intensity across different areas of the exposure pattern. To address this issue, existing compensation methods typically involve placing a custom homogenizing sheet between the lithography machine's illumination system exit and the top of the photomask, using gradient coating technology to achieve customized homogenization. However, existing technologies suffer from the following problems: the homogenizing sheet needs to be precisely positioned between the illumination system exit and the upper surface of the photomask, which is cumbersome, time-consuming, labor-intensive, costly, and has low reliability. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for compensating for uniform illumination in the compound eye of a lithography machine illumination system. By designing a uniform illumination compensation mirror, placing it on the incident surface of the second compound eye lens of the lithography machine, and using cross alignment marks to simplify the installation process, efficient and convenient uniform illumination compensation is achieved.

[0005] To achieve the above objectives, the present invention is implemented using the following technical solution:

[0006] In a first aspect, the present invention provides a method for compensating for uniform illumination in the compound eye of a lithography machine's illumination system, comprising:

[0007] Measure the initial illuminance distribution on the wafer surface of the lithography machine;

[0008] Based on the desired wafer surface illuminance distribution and combined with the initial illuminance distribution, the transmittance distribution of each small square region on the uniform light compensation mirror to be fabricated is calculated using a pre-compensation model.

[0009] Based on the transmittance distribution, determine the corresponding micro-dot density distribution within each small square region;

[0010] The uniform light compensation mirror is fabricated based on the micro-dot density distribution, so that each small square region has a corresponding micro-dot distribution.

[0011] The fabricated uniform light compensation mirror is installed on the incident surface of the second compound eye lens of the illumination system, and the alignment mark on the uniform light compensation mirror is aligned with the boundary line of the compound eye lens to complete the uniform light compensation of the compound eye of the lithography machine illumination system.

[0012] Furthermore, the pre-compensation model is as follows:

[0013]

[0014] In the formula: To compensate for the illuminance distribution on the wafer surface; f1 is the focal length of the first compound eye lens; f F is the focal length of the Fourier lens; n is the number of compound eye lenses; To compensate for the illuminance distribution of a single small square area on the front homogenizing compensation mirror, the formula is used. = We obtain it by reverse reasoning. The initial illuminance distribution on the surface of the lithography machine wafer was measured. This represents the transmittance distribution of a single small square region belonging to the uniform light compensation mirror; Let be the energy transfer function from the image plane of the compound eye system to the wafer plane.

[0015] Furthermore, the calculation formula between the micro-dot density distribution and the transmittance distribution is as follows:

[0016]

[0017] In the formula: This represents the transmittance distribution of a single small square region belonging to the uniform light compensation mirror; This represents the density distribution of micro-points.

[0018] Furthermore, the fabrication of the uniform light compensation mirror based on the micro-dot density distribution includes: establishing a point distribution model in simulation software based on the micro-dot density distribution and performing simulation; fine-tuning the point distribution according to the simulation results before fabricating the uniform light compensation mirror.

[0019] Furthermore, the substrate of the uniform light compensation mirror is quartz glass, and the micro-dots are chromium dots with a diameter of 2 micrometers.

[0020] Furthermore, the uniform light compensation mirror is square in shape, with 15×17 small square areas distributed on it. Each small square area is 4.7 mm × 5.3 mm in size, and there are gaps between adjacent small square areas. The alignment mark is a cross mark located in the gap.

[0021] Secondly, the present invention provides a method for preparing a uniform light compensation mirror, comprising:

[0022] The illuminance distribution on the wafer surface is collected by the lithography machine within a set time period;

[0023] Based on the trend of illumination distribution over time, the wafer surface illumination distribution at different stages of the lithography machine's life cycle can be calculated.

[0024] Based on the calculated illuminance distribution at different stages, the transmittance distribution of each small square region of the uniform light compensation mirror at each stage is calculated using the pre-compensation model described in claim 1.

[0025] Based on the calculated pre-compensation transmittance distribution at different stages, a series of standard uniformity compensation lenses corresponding to different uniformity enhancement effects were manufactured.

[0026] Furthermore, the series of effects corresponding to different uniformity improvement include different levels of 3%, 6%, and 9%.

[0027] Thirdly, the present invention provides a uniform light compensation mirror assembly, which is composed of at least two uniform light compensation mirrors manufactured by the method described in claim 7.

[0028] Furthermore, each uniform light compensation mirror in the uniform light compensation mirror group is designed to improve the uniformity of illumination at different levels, and the total uniformity improvement effect after being used together is the sum of the improvement effects of each individual uniform light compensation mirror.

[0029] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0030] This solution designs a uniform illumination compensation mirror, which is placed on the incident surface of the second compound eye lens of the lithography machine. A crosshair alignment mark simplifies the installation process, achieving efficient and convenient uniform illumination compensation, effectively reducing illuminance non-uniformity on the lithography wafer surface. Furthermore, this solution allows for both customized single compensation mirrors for specific illuminance distributions and tiered compensation through the stacking of standard compensation mirrors. Installation is simple and easy for operators to learn. In addition, this solution avoids the complex position adjustments found in existing technologies, reducing time and cost while improving reliability. Attached Figure Description

[0031] The accompanying drawings, which form part of this specification, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0032] Figure 1 This is a schematic diagram of the light-uniformation principle of the light-uniformation compensation mirror in a method for compensating for the light uniformation of the compound eye in a lithography machine illumination system, provided in Embodiment 1 of the present invention.

[0033] Figure 2 A block diagram showing the external dimensions of a light-uniforming compensation mirror for a method of compensating for uniform light distribution in the compound eye of a lithography machine illumination system, provided in Embodiment 1 of the present invention.

[0034] Figure 3 This is a schematic diagram showing the placement of the light-uniforming compensation mirror in a method for compensating for the uniform illumination of the compound eye in a lithography machine illumination system, as provided in Embodiment 1 of the present invention.

[0035] Figure 4 The initial wafer surface illuminance distribution diagram is provided in Embodiment 1 of the present invention for a compensation method for the uniform illumination of the compound eye of a lithography machine illumination system.

[0036] Figure 5 The illuminance distribution diagram after placing a single uniform light compensation mirror is provided for a compensation method for the compound eye uniform light of a lithography machine illumination system according to Embodiment 1 of the present invention.

[0037] Figure 6 The illuminance distribution diagram after placing a 3% uniform light compensation mirror is provided for a compensation method for the uniform light distribution of the compound eye of the illumination system of a lithography machine according to Embodiment 1 of the present invention.

[0038] Figure 7 The illuminance distribution diagram after placing a 6% uniform light compensation mirror is provided for a compensation method for the compound eye uniform light of a lithography machine illumination system according to Embodiment 1 of the present invention.

[0039] Figure 8 The image shows the illuminance distribution after the 3% and 6% uniform light compensation mirrors are stacked together, which is a compensation method for the compound eye uniform light of the lithography machine illumination system provided in Embodiment 1 of the present invention. Detailed Implementation

[0040] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0041] The following detailed description is exemplary and intended to provide further detailed explanation of the invention. Unless otherwise specified, all technical terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in this invention is for describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention.

[0042] Example 1:

[0043] This embodiment proposes a method for compensating for uniform illumination in the compound eye of a lithography machine's illumination system. The solution primarily utilizes a uniform illumination compensation mirror, the core of which lies in adjusting the transmittance of different regions by controlling the distribution of micro-dot density, thereby compensating for illuminance non-uniformity. The uniform illumination compensation mirror creates shadows on a glass plate (typically made of quartz) using tiny dots (approximately 2µm in diameter chromium (Cr) dots). By controlling the dot density distribution in different regions, it ensures that any region has any transmittance (i.e., areas with high dot density have low transmittance, and areas with low dot density have high transmittance). Therefore, it can serve as a uniform illumination device—the corresponding dot density distribution is designed to correspond to the desired uniform illumination distribution. Figure 1 A schematic diagram of the homogenizing principle of the homogenizing compensation mirror is given. In areas with strong illuminance, the corresponding area of ​​the homogenizing compensation mirror should have lower transmittance, while in areas with weak illuminance, the corresponding area of ​​the homogenizing compensation mirror should have higher transmittance.

[0044] Figure 2 A schematic diagram of the uniform light compensation mirror is provided. The mirror is a solid square glass plate measuring 88mm × 88mm with a thickness of 2.3mm. It has 15 × 17 identical small square grid areas. Each small square area measures 4.7mm × 5.3mm, and there is a 0.1mm gap between each square. A 10µm wide, 1mm crosshair alignment mark is located in the center of each gap.

[0045] Figure 3 A schematic diagram of the placement of the homogenizing compensator is provided. This homogenizing compensator is placed on the incident surface of the second fly eye lens, with the non-chromium (Cr) surface in close contact with the incident surface of the second fly eye lens. The crosshair alignment mark on the homogenizing compensator must be aligned with the boundary line of the fly eye lens.

[0046] When designing this uniform light compensation mirror, it is necessary to first measure the illuminance distribution on the wafer surface of the lithography machine. Based on the desired illuminance distribution on the wafer surface Using the pre-compensation model, the pre-compensation transmittance distribution of a single small square region of the uniform light compensation mirror was calculated. For a compound eye system, the illuminance distribution on the image plane follows the following logical relationship:

[0047]

[0048] In the formula: ( , () represents the illuminance distribution on the image plane of the compound eye system; and These are two-dimensional coordinates with the optical axis of the Fourier lens in the compound eye system as the origin; f1 is the focal length of the first compound eye sub-lens; f F is the focal length of the Fourier lens; n is the number of compound eye lenses; It is the reciprocal of the expansion factor from the aperture of the compound eye sub-unit to the image plane; ( i , i () represents the illuminance distribution of a single sublens in a compound eye; i and i These are two-dimensional coordinates with the optical axis positions of each sub-lens of the compound eye as the origin.

[0049] Therefore, the pre-compensation model can be derived as follows:

[0050]

[0051] In the formula: To compensate for the illuminance distribution on the wafer surface; f1 is the focal length of the first compound eye lens; f F is the focal length of the Fourier lens; n is the number of compound eye lenses; To compensate for the illuminance distribution of a single small square area on the front homogenizing compensation mirror, the formula is used. = We obtain it by reverse reasoning. The initial illuminance distribution on the surface of the lithography machine wafer was measured. This represents the transmittance distribution of a single small square region belonging to the uniform light compensation mirror; Let be the energy transfer function from the image plane of the compound eye system to the wafer plane.

[0052] Based on the currently calculated pre-compensated transmittance distribution A corresponding point distribution model is established in the simulation software for simulation, and the point distribution is fine-tuned based on the simulation results.

[0053] The above addresses the issue of irregular illumination distribution on the wafer surface of a lithography machine. For lithography machine wafer surface illumination distribution that is regular, a standard uniform light compensation mirror can be established. Details are as follows:

[0054] (1) Collect the illuminance distribution on the wafer surface of the lithography machine within a certain time period. ;

[0055] (2) Based on the trend of the illuminance distribution on the wafer surface over time, the illuminance distribution on the wafer surface at different stages of the lithography machine's life cycle is estimated. ;

[0056] (3) Based on the calculated illuminance distribution on the wafer surface Using the pre-compensation model formula Calculate the pre-compensation transmittance of a single small square area of ​​the homogenization compensation mirror at different stages of the lithography machine's lifecycle. distributed;

[0057] (4) Based on the pre-compensation transmittance of multiple stages Distribute and manufacture a series of standard homogenization compensation lenses that can improve uniformity to varying degrees. For example, improving uniformity by 3%, 6%, 9%, etc.

[0058] It should be noted that during the long-term operation of a lithography machine, the optical components of the illumination system gradually degrade in performance due to factors such as material aging, contamination accumulation, and thermal stress. This solution innovatively establishes an illuminance distribution prediction model based on the physical mechanism of optical component aging. Through quantitative analysis of key factors such as light source attenuation, lens contamination, and mirror performance degradation, it achieves accurate prediction of the illuminance distribution throughout the entire lifecycle of the lithography machine. The formula for the illuminance distribution prediction model based on the physical mechanism of optical component aging is:

[0059]

[0060] In the formula: M(t,x,y) is the predicted illuminance value at position (x,y) at time t; M0(x,y) is the reference illuminance distribution under the initial state of the equipment; λ k f is the aging rate constant of the k-th optical element; t is the cumulative operating time of the equipment; k (E,T) is an environmental factor function characterizing the effects of energy density E and temperature T on aging; K is the total number of critical optical components; ΔM s (t,x,y) represents the illuminance fluctuation term caused by random factors.

[0061] The above-mentioned uniformity compensation mirrors can be used individually or stacked. When stacked, the effect of improving uniformity is the same as the effect of stacking. For example, if two uniformity compensation mirrors that improve uniformity by 3% and 6% are stacked, the uniformity of the illuminance distribution on the wafer surface can be improved by about 9%.

[0062] Please see Figure 4When a single uniformity compensation lens is used, the initial wafer surface illuminance non-uniformity is 22.8%. Using a uniformity compensation lens reduces this to below 3%. The specific steps are as follows:

[0063] (1) Using the above pre-compensation model formula The transmittance distribution of a single small square region of the uniform light compensation mirror was calculated. ;

[0064] (2) Establish a model in the software. Based on the calculated transmittance distribution... Input micro-point density distribution And set the dot gap to be greater than 1µm. The formula for transmittance and dot density is: ;

[0065] (3) Derive the point coordinates based on the point density distribution obtained from the simulation. Based on the point coordinates, chromium points with a diameter of 2 μm are distributed in the small square area on the quartz glass plate. The coordinates of the chromium points in all small square areas are the same.

[0066] (4) Install the prepared homogenizing compensator onto the incident surface of the second compound eye lens, ensuring that the non-chromium surface of the compensator is in close contact with the second compound eye lens. During installation, ensure that the cross markings on the surface of the homogenizing compensator are aligned with the boundary line of the compound eye lens under a microscope.

[0067] Please see Figure 5 After using a uniform light compensation lens to compensate for the illuminance distribution, it can be seen that the illuminance is basically uniform and the non-uniformity has been reduced to below 3%.

[0068] When uniform light compensation mirrors are used in combination, the initial wafer surface illuminance non-uniformity is 22.8%.

[0069] (1) Based on the above method for using a single uniformity compensation mirror, uniformity compensation mirrors that can be made by 3% and 6% respectively.

[0070] (2) For the illumination distribution of a single uniformity compensation mirror that improves uniformity by 3%, please refer to [the original text]. Figure 6 ;

[0071] (3) For the illumination distribution of a single uniformity compensation mirror that improves uniformity by 6%, please refer to [the original text]. Figure 7 ;

[0072] Place the two homogenizing compensation lenses on top of each other, aligning their crosshair markings with the boundary line of the compound eye lens. For the illuminance distribution of simultaneously placing homogenizing compensation lenses that improve homogenization by 3% and 6% respectively, please refer to [reference needed]. Figure 8 As can be seen, when the two are used together, the uniformity is improved by 9%, which is the sum of the two.

[0073] As is known from common technical knowledge, this invention can be implemented through other embodiments that do not depart from its spirit or essential characteristics. Therefore, the disclosed embodiments described above are merely illustrative and not exhaustive. All modifications within the scope of this invention or its equivalents are included in this invention.

[0074] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention.

Claims

1. A method for compensating for uniform illumination in the compound eye of a lithography machine's illumination system, characterized in that, include: Measure the initial illuminance distribution on the wafer surface of the lithography machine; Based on the desired wafer surface illuminance distribution and combined with the initial illuminance distribution, the transmittance distribution of each small square region on the uniform light compensation mirror to be fabricated is calculated using a pre-compensation model. Based on the transmittance distribution, determine the corresponding micro-dot density distribution within each small square region; The uniform light compensation mirror is fabricated based on the micro-dot density distribution, so that each small square region has a corresponding micro-dot distribution. The fabricated uniform light compensation mirror is installed on the incident surface of the second compound eye lens of the illumination system, and the alignment mark on the uniform light compensation mirror is aligned with the boundary line of the compound eye lens to complete the uniform light compensation of the compound eye of the lithography machine illumination system.

2. The compensation method for uniform illumination of the compound eye in a lithography machine illumination system according to claim 1, characterized in that, The pre-compensation model is as follows: ； In the formula: To compensate for the illuminance distribution on the wafer surface; f1 is the focal length of the first compound eye lens; f F is the focal length of the Fourier lens; n is the number of compound eye lenses; To compensate for the illuminance distribution of a single small square area on the front homogenizing compensation mirror, the formula is used. = We obtain it by reverse reasoning. The initial illuminance distribution on the surface of the lithography machine wafer was measured. This represents the transmittance distribution of a single small square region belonging to the uniform light compensation mirror; Let be the energy transfer function from the image plane of the compound eye system to the wafer plane.

3. The compensation method for uniform illumination of the compound eye in a lithography machine illumination system according to claim 1, characterized in that, The formula for calculating the relationship between the micro-dot density distribution and the transmittance distribution is as follows: ； In the formula: This represents the transmittance distribution of a single small square region belonging to the uniform light compensation mirror; This represents the density distribution of micro-points.

4. The compensation method for uniform illumination of the compound eye in a lithography machine illumination system according to claim 1, characterized in that, Fabricating the uniform light compensation mirror based on the micro-dot density distribution includes: establishing a point distribution model in simulation software based on the micro-dot density distribution and performing simulation; fine-tuning the point distribution according to the simulation results before fabricating the uniform light compensation mirror.

5. The compensation method for uniform illumination of the compound eye in a lithography machine illumination system according to claim 1, characterized in that, The substrate of the uniform light compensation mirror is quartz glass, and the micro-dots are chromium dots with a diameter of 2 micrometers.

6. The compensation method for uniform illumination of the compound eye in a lithography machine illumination system according to claim 1, characterized in that, The uniform light compensation mirror is square in shape, with 15×17 small square areas distributed on it. Each small square area is 4.7 mm × 5.3 mm in size, and there are gaps between adjacent small square areas. The alignment mark is a cross mark located in the gap.

7. A method for preparing a uniform light compensation mirror, characterized in that, include: The illuminance distribution on the wafer surface is collected by the lithography machine within a set time period; Based on the trend of illumination distribution over time, the wafer surface illumination distribution at different stages of the lithography machine's life cycle can be calculated. Based on the calculated illuminance distribution at different stages, the transmittance distribution of each small square region of the uniform light compensation mirror at each stage is calculated using the pre-compensation model described in claim 1. Based on the calculated pre-compensation transmittance distribution at different stages, a series of standard uniformity compensation lenses corresponding to different uniformity enhancement effects were manufactured.

8. The method for preparing the standard homogenizing compensation mirror according to claim 7, characterized in that, The series of effects corresponding to different uniformity improvement include different levels of 3%, 6% and 9%.

9. A uniform light compensation lens assembly, characterized in that, It is composed of at least two uniform light compensation mirrors made by the method described in claim 7, stacked together.

10. The uniform light compensation lens assembly according to claim 9, characterized in that, Each uniform light compensation mirror in the uniform light compensation mirror group is designed to improve the uniformity of illumination at different levels. The total uniformity improvement effect after being used together is the sum of the improvement effects of each individual uniform light compensation mirror.

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