Method for configuring parameters of lithography machine illumination system, lithography process and semiconductor structure

Abstract

The application provides a lithography illuminating system parameter configuration method, a lithography process and a semiconductor structure. The configuration method first takes the numerical aperture as a single variable, simulates to obtain exposure characteristic values corresponding to different numerical apertures under the same illumination coherence factor, and obtains a target numerical aperture accordingly; then takes the illumination coherence factor as a single variable, simulates to obtain exposure characteristic values corresponding to different illumination coherence factors under the target numerical aperture, and screens a first target illumination coherence factor corresponding to a better exposure characteristic value. The numerical aperture and the illumination coherence factor are thus configured, which not only enables efficient configuration of the illumination system parameters, but also facilitates improvement of the precision of lithography and effectively alleviates various morphology difference problems in actual processes.

Description

Technical Field

[0001] This invention relates to the field of semiconductor fabrication technology, and in particular to a method for configuring illumination system parameters of a lithography machine, a lithography process, and a semiconductor structure. Background Technology

[0002] In the fabrication of contact image sensors (CIS), to ensure image quality, the photoresist thickness applied to the pixel layer is generally greater than 2.0 micrometers. Therefore, during photolithography, suitable illumination system parameters need to be pre-configured for thicker photoresist layers; otherwise, abnormal lithographic morphology is highly likely to occur. Current parameter configuration typically involves setting parameters such as depth of focus (DoF), mask error enhancement factor (MEEF), normalized image log slope (NILS), numerical aperture (NA), and illumination coherence factor (sigma) based on photolithography simulations.

[0003] However, the lighting system parameters configured in the simulation still show significant differences in actual manufacturing processes. For example... Figure 1 As shown, the film profile formed using photolithography simulation configuration parameters exhibits a bulge anomaly, P1. In current processes, the illumination parameters are adjusted based on system recommendations, but this may still result in issues such as... Figure 2 The photolithography residue P2 issue is shown. Furthermore, to optimize the configuration of the illumination system parameters, current processes can only utilize simulation platforms and manually select these parameters to obtain the desired results. Figure 3 The target morphology M is shown. However, the manual selection method is not only time-consuming and inefficient, but also has limited optimization of the illumination system parameters, affecting the lithography effect.

[0004] Therefore, a new method for configuring lighting system parameters is urgently needed to solve the above-mentioned technical problems. Summary of the Invention

[0005] The purpose of this invention is to provide a method for configuring the illumination system parameters of a lithography machine, a lithography process, and a semiconductor structure, so as to solve the problem of how to efficiently configure the illumination system parameters of a lithography machine.

[0006] To solve the above technical problems, the present invention provides a method for configuring the illumination system parameters of a lithography machine, comprising:

[0007] It offers multiple different numerical apertures and multiple different illumination coherence factors;

[0008] Under the same illumination coherence factor, the exposure characteristic values ​​corresponding to different numerical apertures were simulated and obtained respectively;

[0009] The numerical aperture corresponding to the first exposure characteristic value condition is selected as the target numerical aperture;

[0010] Under the same target numerical aperture, the exposure characteristic values ​​corresponding to different illumination coherence factors were simulated and obtained respectively;

[0011] The illumination coherence factor that meets the second exposure characteristic value condition is selected as the first target illumination coherence factor.

[0012] Optionally, in the method for configuring the illumination system parameters of the lithography machine, the process of selecting the numerical aperture corresponding to the first exposure characteristic value condition as the target numerical aperture includes:

[0013] The different numerical apertures are arranged in ascending order, and the numerical aperture corresponding to the change of the exposure feature value from non-steady state to steady state is obtained as the target numerical aperture; and the steady-state exposure feature value is set as the first exposure feature value.

[0014] Optionally, in the method for configuring the illumination system parameters of the lithography machine, the process of selecting the illumination coherence factor corresponding to the second exposure characteristic value condition as the first target illumination coherence factor includes:

[0015] Determine whether the exposure feature value corresponding to different illumination coherence factors is greater than the first exposure feature value; if so, the illumination coherence factor corresponding to the exposure feature value is taken as the first target illumination coherence factor.

[0016] Optionally, in the method for configuring the illumination system parameters of the lithography machine, the illumination coherence factor includes an external coherence factor and an internal coherence factor; and the first target illumination coherence factor includes the external coherence factor and the internal coherence factor.

[0017] Optionally, in the method for configuring the lithography machine illumination system parameters, when the first target illumination coherence factor includes multiple sets of external coherence factors and internal coherence factors, after obtaining the first target illumination coherence factor, the method for configuring the lithography machine illumination system parameters further includes:

[0018] Calculate the corresponding index value based on the external coherence factor and the internal coherence factor of each group;

[0019] The set of external coherence factors and internal coherence factors corresponding to the largest index value is selected as the second target illumination coherence factor.

[0020] Optionally, in the method for configuring the illumination system parameters of the lithography machine, the formula for calculating the index value is as follows:

[0021] Y=(Outer sigma - Inner sigma) / (Intensity max - Intensity min );

[0022] Where Y is the index value; Outer sigma is the external coherence factor; Inner sigma is the internal coherence factor; Intensity max The maximum exposure characteristic value corresponding to each group of external coherence factors and internal coherence factors; Intensity min The minimum exposure characteristic value corresponding to each group of external coherence factors and internal coherence factors.

[0023] Optionally, in the method for configuring the illumination system parameters of the lithography machine, during the process of providing multiple different numerical apertures and multiple different illumination coherence factors, the multiple different numerical apertures and multiple different illumination coherence factors are selected according to the preset same development basis conditions.

[0024] Optionally, in the method for configuring the illumination system parameters of the lithography machine, the development basis conditions include simulated film structure, photoresist thickness, and critical dimensions.

[0025] Based on the same inventive concept, the present invention also provides a photolithography process in which the parameters are configured using the aforementioned method for configuring the illumination system parameters of the photolithography machine.

[0026] Based on the same inventive concept, the present invention also provides a semiconductor structure, which is prepared by the aforementioned photolithography process.

[0027] In summary, this invention provides a method for configuring illumination system parameters of a lithography machine, a lithography process, and a semiconductor structure. Compared to existing technologies, this configuration method first uses the numerical aperture as a single variable to simulate and obtain exposure characteristic values ​​corresponding to different numerical apertures under the same illumination coherence factor, and obtains the target numerical aperture accordingly. Then, using the illumination coherence factor as a single variable, it simulates and obtains exposure characteristic values ​​corresponding to different illumination coherence factors under the target numerical aperture, and selects the first target illumination coherence factor with the better exposure characteristic values. By configuring the numerical aperture and the illumination coherence factor in this way, not only can efficient configuration of illumination system parameters be achieved, but it also helps to improve the accuracy of lithography and effectively alleviate various morphological differences that occur in actual processes. Attached Figure Description

[0028] Those skilled in the art will understand that the accompanying drawings are provided to better understand the invention and do not constitute any limitation on the scope of the invention.

[0029] Figure 1 This is a schematic diagram of a protruding structure in the photolithography film layer in existing technology.

[0030] Figure 2 This is a schematic diagram of the structure in which residues appear in the photolithography film layer in the existing technology.

[0031] Figure 3 This is a schematic diagram of the semiconductor structure with the target morphology in the prior art.

[0032] Figure 4 This is a flowchart of the method for configuring the illumination system parameters of a lithography machine in an embodiment of the present invention.

[0033] Figure 5 This is a distribution map of exposure feature values ​​in an embodiment of the present invention.

[0034] And, in the attached image:

[0035] P1 - Protrusion; P2 - Residue; P3 - Target area; M - Target morphology. Detailed Implementation

[0036] To make the objectives, advantages, and features of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that the drawings are all in a very simplified form and are not drawn to scale, and are only used to facilitate and clearly illustrate the objectives of the embodiments of the present invention. Furthermore, the structures shown in the drawings are often part of the actual structures. In particular, different figures may emphasize different aspects and sometimes use different scales. It should also be understood that, unless specifically stated or indicated, the terms "first," "second," "third," etc., in the specification are only used to distinguish the various components, elements, steps, etc., in the specification, and are not used to indicate the logical or sequential relationships between the various components, elements, steps, etc.

[0037] Please see Figure 4 This embodiment provides a method for configuring the illumination system parameters of a lithography machine, including:

[0038] Step 1 S10: Provide multiple different numerical apertures and multiple different illumination coherence factors;

[0039] Step 2 S20: Under the same illumination coherence factor, simulate and obtain the exposure characteristic values ​​corresponding to different numerical apertures;

[0040] Step 3 S30: Select the numerical aperture that meets the first exposure characteristic value condition as the target numerical aperture;

[0041] Step 4S40: Under the same target numerical aperture, simulate and obtain the exposure characteristic values ​​corresponding to different illumination coherence factors;

[0042] Step 5 S50: Select the illumination coherence factor that meets the second exposure characteristic value condition as the first target illumination coherence factor.

[0043] Based on this, the method for configuring the illumination system parameters of the lithography machine provided in this embodiment can not only achieve efficient configuration of the illumination system parameters, but also help improve the accuracy of lithography.

[0044] The following is in conjunction with the appendix Figure 4 and Figure 5 This embodiment provides a detailed explanation of the configuration method for the illumination system parameters of the lithography machine.

[0045] Step 1 S10: Provide multiple different numerical apertures and multiple different illumination coherence factors.

[0046] The method for configuring the illumination system parameters of the lithography machine provided in this embodiment is implemented based on a simulation platform. Therefore, in the process of selecting the preset values ​​for numerical aperture and illumination coherence factor, it is necessary to determine them according to the same preset development conditions. These development conditions include, but are not limited to, the simulated film structure, photoresist thickness, and critical dimensions. In other words, in configuring the numerical aperture and illumination coherence factor, all other development conditions are the same to follow the single-variable principle and ensure that the configuration results have better reliability and accuracy.

[0047] For example, the photoresist thickness is 2.6 micrometers, the critical dimension is 0.2 micrometers, and the lithography machine illumination system is ring illumination or four-level illumination, etc. The illumination coherence factor includes the outer coherence factor and the inner coherence factor. Then, multiple different numerical apertures (NA) and multiple different illumination coherence factors are selected as shown in Tables 1 and 2 below.

[0048] Table 1. Several different numerical apertures (NA)

[0049]

[0050] Table 2. Several different external coherence factors and internal coherence factors.

[0051]

[0052] It should be noted that numerical aperture (NA) characterizes the angular range that an optical system can collect light from. In lithography machines, NAV is directly related to the performance of the projection lens and determines the minimum image size that the lithography machine can project clearly, i.e., the resolution of the lithography machine. Illumination coherence factor (ICF), on the other hand, is related to the shape and distribution of the light source and is defined as the ratio of the diameter of the light source image on the entrance pupil of the lens to the diameter of the lens aperture. Furthermore, in a lithography system, NAV and IIF directly affect the lithography resolution and depth of focus. The depth of focus is an important parameter used to measure the exposure process window, indicating the relationship between the imaging quality of the exposure system and the position on the wafer surface. Therefore, the optimized configuration of NAV and IIF in this embodiment is beneficial for improving the lithography process effect.

[0053] Step 2 S20: Under the same illumination coherence factor, simulate and obtain the exposure characteristic values ​​corresponding to different numerical apertures.

[0054] For example, if the external coherence factor is selected as 0.8 and the internal coherence factor as 0.6 according to Table 2 above, and photolithography simulation is performed with the six numerical apertures shown in Table 1, the simulation results shown in Table 3 below can be obtained.

[0055] Table 3. Exposure characteristics (intensity) obtained under multiple different numerical apertures (NA).

[0056]

[0057] In this embodiment, the exposure intensity refers to a quantity related to the exposure intensity simulated by the simulation system based on process parameters, and it has a positive correlation with the exposure intensity in the actual photolithography process. Furthermore, each numerical aperture can be obtained under system simulation. Figure 5 The table above shows the exposure characteristic value distribution map corresponding to the simulated film structure. For ease of data analysis, the exposure characteristic values ​​shown in Table 3 are those corresponding to the same target region P3 in each distribution map. The target region P3 is preferably the exposure center region. For example, when NA=0.65, the exposure characteristic value of target region P3 in the corresponding exposure characteristic value distribution map is 0.45.

[0058] Step 3 S30: Select the numerical aperture that meets the first exposure characteristic value condition as the target numerical aperture.

[0059] Specifically, the process of selecting the target numerical aperture includes: arranging different numerical apertures in ascending order, and obtaining the numerical aperture corresponding to the exposure feature value when it changes from an unsteady state to a steady state, which is taken as the target numerical aperture; and setting the steady-state exposure feature value as the first exposure feature value.

[0060] For example, as shown in Table 3, with the increase of the numerical aperture, the exposure characteristic value first shows an increasing trend and then tends to a fixed value of 0.45. Based on this, the state in which the exposure characteristic value increases with the increase of the numerical aperture is the non-steady state, while the state in which the exposure characteristic value does not change with the increase of the numerical aperture can be identified as the steady state. Therefore, the numerical aperture corresponding to the transition of the exposure characteristic value from the non-steady state to the steady state is 0.65, which is the target numerical aperture. And when NA=0.65, the exposure characteristic value is 0.45, which is the first exposure characteristic value.

[0061] It is understandable that a larger numerical aperture indicates a wider range of light angles collected by the illumination system, which is beneficial for improving the resolution and depth of focus of the lithography machine. Furthermore, a larger numerical aperture helps improve exposure efficiency. Therefore, when the exposure characteristic value does not change with the numerical aperture (i.e., it becomes steady-state), the corresponding numerical aperture is the optimal configuration value. Thus, in this embodiment, the numerical aperture corresponding to the transition of the exposure characteristic value from an unstable state to a steady state is selected as the target numerical aperture.

[0062] Step 4S40: Under the same target numerical aperture, simulate and obtain the exposure characteristic values ​​corresponding to different illumination coherence factors.

[0063] After obtaining the target numerical aperture, the configuration of the illumination coherence factor needs to be further optimized. Therefore, during multiple lithography simulations using the illumination coherence factor as a single variable, the numerical aperture set each time is the target numerical aperture. For example, with NA=0.65, the exposure characteristic values ​​corresponding to each illumination coherence factor shown in Table 2 are simulated and obtained.

[0064] Step 5 S50: Select the illumination coherence factor that meets the second exposure characteristic value condition as the first target illumination coherence factor.

[0065] It should be noted that, since the illumination coherence factor has a certain impact on lithographic resolution, depth of focus, and exposure efficiency, in order to further optimize the exposure effect, the second exposure feature value condition is that the exposure feature value corresponding to the illumination coherence factor is greater than the first exposure feature value. Based on this, the process of obtaining the first target illumination coherence factor includes: determining whether the exposure feature value corresponding to different illumination coherence factors is greater than the first exposure feature value; if so, the illumination coherence factor corresponding to the exposure feature value is used as the first target illumination coherence factor; if not, the illumination coherence factor corresponding to the exposure feature value is not used as the first target illumination coherence factor. The exposure feature value corresponding to each illumination coherence factor used for numerical comparison with the first exposure feature value is also selected from the exposure feature value at the target region P3 position in the corresponding exposure feature value distribution map (e.g., ...). Figure 5 (As shown).

[0066] For example, when the external coherence factor is 0.89 and the internal coherence factor is 0.7, the corresponding exposure characteristic value is greater than the first exposure characteristic value. Therefore, the external coherence factor of 0.89 and the internal coherence factor of 0.7 constitute the first target illumination coherence factor. If the first target illumination coherence factor selected based on the second exposure characteristic value condition is unique, it can be used as the optimal illumination coherence factor configuration value. However, in actual simulations, the first target illumination coherence factor that meets the condition that the corresponding exposure characteristic value is greater than the first exposure characteristic value is often not unique. Therefore, further optimization of the illumination coherence factor is required.

[0067] Therefore, since current lithography systems typically employ ring illumination or four-level illumination, the illumination coherence factor includes an external coherence factor and an internal coherence factor. Furthermore, when the first target illumination coherence factor includes multiple sets of the external and internal coherence factors, the method for configuring the lithography machine illumination system parameters after obtaining the first target illumination coherence factor further includes:

[0068] Step 6 S60: Calculate the corresponding index value based on the external coherence factor and the internal coherence factor of each group;

[0069] Step 7 S70: Select the set of external coherence factors and internal coherence factors corresponding to the largest index value as the second target illumination coherence factor.

[0070] Specifically, the formula for calculating the value of the aforementioned indicator is as follows:

[0071] Y=(Outer sigma - Inner sigma) / (Intensity max - Intensitymin );

[0072] Where Y is the index value; Outer sigma is the external coherence factor; Inner sigma is the internal coherence factor; Intensity max The maximum exposure characteristic value corresponding to each group of external coherence factors and internal coherence factors; Intensity min This refers to the minimum exposure characteristic value corresponding to each group of external coherence factors and internal coherence factors. In other words, the simulation obtains the corresponding values ​​for each group of external coherence factors and internal coherence factors as follows: Figure 5 The exposure feature value distribution map shown indicates that Intensity max The maximum exposure feature value in the exposure feature value distribution map, Intensity min The smallest exposure feature value in the exposure feature value distribution map.

[0073] For example, the first target illumination coherence factor that conforms to the second exposure characteristic value adjustment includes eight sets of external coherence factors and internal coherence factors, which are (0.85, 0.55), (0.85, 0.6), (0.85, 0.65), (0.85, 0.7), (0.89, 0.55), (0.89, 0.6), (0.89, 0.65), and (0.89, 0.7), respectively. Y1, Y2, Y3, Y4, Y5, Y6, Y7, and Y8 are calculated based on the data related to these eight sets of external and internal coherence factors. Furthermore, by comparing the values ​​of Y1 to Y8, the set of external and internal coherence factors corresponding to the largest index value is obtained as the second target illumination coherence factor. For example, if the largest index value is Y6, then the coherence factor of the second target illumination is (0.89, 0.6), that is, the external coherence factor is 0.89 and the internal and external coherence factors are 0.6.

[0074] It is understandable that the larger the difference between the external coherence factor and the internal coherence factor, i.e., the larger the ring width of the ring illumination, the greater the depth of focus in the lithography system; the two are positively correlated. And, (Intensity) max - Intensity min The larger the value of Y, the worse the illumination uniformity; the two are negatively correlated. Therefore, the larger the value of Y, the better the overall configuration of the depth of focus and illumination uniformity in the lithography system, which is beneficial for obtaining better lithography accuracy and avoiding various morphological differences. In summary, this completes the efficient optimization configuration of the numerical aperture and illumination coherence factor in the lithography machine's illumination system.

[0075] Based on the same concept, this embodiment also provides a photolithography process. The photolithography process configures parameters using the aforementioned method for configuring the illumination system parameters of the photolithography machine.

[0076] Based on the same concept, this embodiment also provides a semiconductor structure. The semiconductor structure is fabricated using the photolithography process described above. The semiconductor structure includes, but is not limited to, a CIS (CMOS Image Sensor).

[0077] In summary, the method for configuring the illumination system parameters of the lithography machine, the lithography process, and the semiconductor structure provided in this embodiment first uses the numerical aperture as a single variable to simulate and obtain the exposure characteristic values ​​corresponding to different numerical apertures under the same illumination coherence factor, and obtains the target numerical aperture accordingly. Then, using the illumination coherence factor as a single variable, it simulates and obtains the exposure characteristic values ​​corresponding to different illumination coherence factors under the target numerical aperture, and selects the first target illumination coherence factor with the better exposure characteristic value. Furthermore, based on the first target illumination coherence factor, an index value can be further calculated, and the illumination coherence factor corresponding to the largest index value is selected as the better second target illumination coherence factor. This configuration of the numerical aperture and the illumination coherence factor not only achieves efficient configuration of the illumination system parameters but also helps improve the accuracy of lithography and effectively alleviates various morphological differences that occur in actual processes.

[0078] Furthermore, it should be understood that although the present invention has been disclosed above with reference to preferred embodiments, these embodiments are not intended to limit the present invention. For any person skilled in the art, many possible variations and modifications can be made to the technical solutions of the present invention based on the disclosed technical content, or equivalent embodiments can be modified accordingly, without departing from the scope of the present invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the content of the present invention, shall still fall within the scope of protection of the present invention.

Claims

1. A method for configuring illumination system parameters of a lithography machine, characterized in that, include: It offers multiple different numerical apertures and multiple different illumination coherence factors; Under the same illumination coherence factor, the exposure characteristic values ​​corresponding to different numerical apertures were simulated and obtained respectively; The numerical aperture corresponding to the first exposure characteristic value condition is selected as the target numerical aperture; Under the same target numerical aperture, the exposure characteristic values ​​corresponding to different illumination coherence factors were simulated and obtained respectively; The illumination coherence factor corresponding to the second exposure characteristic value condition is selected as the first target illumination coherence factor; wherein, The process of selecting the numerical aperture corresponding to the first exposure characteristic value condition as the target numerical aperture includes: The different numerical apertures are arranged in ascending order, and the numerical aperture corresponding to the transition of the exposure characteristic value from an unstable state to a stable state is obtained as the target numerical aperture; and the stable exposure characteristic value is set as the first exposure characteristic value; and, The process of selecting the illumination coherence factor corresponding to the second exposure characteristic value condition as the first target illumination coherence factor includes: Determine whether the exposure feature value corresponding to different illumination coherence factors is greater than the first exposure feature value; if so, the illumination coherence factor corresponding to the exposure feature value is taken as the first target illumination coherence factor.

2. The method for configuring the illumination system parameters of a lithography machine according to claim 1, characterized in that, The illumination coherence factor includes an external coherence factor and an internal coherence factor; and the first target illumination coherence factor includes the external coherence factor and the internal coherence factor.

3. The method for configuring the illumination system parameters of a lithography machine according to claim 2, characterized in that, When the first target illumination coherence factor includes multiple sets of external coherence factors and internal coherence factors, the method for configuring the lithography machine illumination system parameters after obtaining the first target illumination coherence factor further includes: Calculate the corresponding index value based on the external coherence factor and the internal coherence factor of each group; The set of external coherence factors and internal coherence factors corresponding to the largest index value is selected as the second target illumination coherence factor.

4. The method for configuring the illumination system parameters of a lithography machine according to claim 3, characterized in that, The formula for calculating the value of the aforementioned indicator is as follows: Y=(Outer sigma - Inner sigma) / (Intensity max - Intensity min ); Where Y is the index value; Outer sigma is the external coherence factor; Inner sigma is the internal coherence factor; Intensity max The maximum exposure characteristic value corresponding to each group of external coherence factors and internal coherence factors; Intensity min The minimum exposure characteristic value corresponding to each group of external coherence factors and internal coherence factors.

5. The method for configuring the illumination system parameters of a lithography machine according to claim 1, characterized in that, In providing multiple different numerical apertures and multiple different illumination coherence factors, the multiple different numerical apertures and multiple different illumination coherence factors are selected based on the same preset development basis conditions.

6. The method for configuring the illumination system parameters of a lithography machine according to claim 5, characterized in that, The development prerequisites include simulated film structure, photoresist thickness, and key dimensions.

7. A photolithography process, characterized in that, The parameters are configured using the method described in any one of claims 1 to 6 during the lithography parameter configuration process.

8. A semiconductor structure, characterized in that, It is prepared using the photolithography process described in claim 7.

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