Method for optimizing thickness of photoresist

Abstract

The invention provides a method for optimizing the thickness of photoresist, which comprises the following steps of: forming a first photoresist layer on a semiconductor substrate, enabling the thicknesses of the first photoresist layer positioned in different exposure areas to be different, then forming mask patterns in each exposure area, and then measuring the critical dimension between the same mask patterns in each exposure area, and manufacturing a relation curve of the photoresist thickness and the key size according to the key size and the corresponding photoresist thickness, and adjusting the photoresist thickness according to the relation curve of the photoresist thickness and the key size, so that different photoresist thicknesses and corresponding key sizes are acquired on a single semiconductor substrate to adjust and optimize the photoresist thickness. Compared with the prior art in which 10-20 semiconductor substrates are used, the method has the advantages that the cost can be saved, the process steps are simplified, the time is shortened, and the manpower is saved.

Description

Technical Field

[0001] The invention relates to the technical field of integrated circuit manufacturing, and in particular to a method for optimizing the thickness of a photoresist. Background Art

[0002] In integrated circuit manufacturing technology, photolithography is a key process. With the development of semiconductor technology, the requirements for the critical dimensions of photolithography are getting higher and higher. Therefore, how to control the stability of critical dimensions has become an increasingly important issue in the photolithography process. The thickness of photoresist is crucial to the photolithography process. Different thicknesses of photoresist will result in different reflectivity of photoresist during exposure, which will affect the critical dimensions and edge roughness of the photoresist pattern, and ultimately affect the working performance of semiconductor devices. In the field of photolithography, the relationship curve between the critical dimensions of the photolithography pattern and the thickness of the photoresist is called the critical dimension swing curve, and the thickness of the photoresist is evaluated through this curve to stabilize the critical dimensions.

[0003] The current process technology for obtaining the above critical dimension swing curve usually requires 10 to 20 wafers, each of which is spin-coated with a certain thickness of photoresist, and then these wafers are exposed and developed, and then the critical dimensions corresponding to different wafers are measured to obtain the critical dimension swing curve. However, this process technology requires a large number of wafers and a large amount of photoresist, which increases the testing time and cost. Summary of the invention

[0004] The object of the present invention is to provide a method for optimizing the thickness of a photoresist, so as to solve the problem of long test time and high test cost required for making a critical dimension rocking curve in the prior art.

[0005] In order to solve the above technical problems, the present invention provides a method for optimizing the thickness of photoresist, comprising forming a first photoresist layer on a semiconductor substrate, wherein the thickness of the first photoresist layer in different exposure areas is different; obtaining the thickness value of the first photoresist layer in each of the exposure areas; exposing and developing each of the exposure areas one by one, and transferring the mask pattern on the mask plate to each of the exposure areas, wherein the exposure parameters for exposing each of the exposure areas are the same; and measuring the critical dimensions of the same mask pattern in each of the exposure areas, and preparing a photoresist thickness and critical dimension relationship curve based on the critical dimensions of each of the mask patterns and the corresponding thickness of the first photoresist layer, and adjusting the photoresist thickness based on the photoresist thickness and critical dimension relationship curve.

[0006] Preferably, the method for forming the first photoresist layer in the method for optimizing the photoresist thickness includes: forming a first photoresist film on the semiconductor substrate, and forming a second photoresist film on the first photoresist film; exposing the second photoresist film, wherein the exposure energy for each exposure area is different; developing the second photoresist film to form a second photoresist layer, and the thickness of the second photoresist layer in different exposure areas is different; and performing an etching process on the first photoresist film to transfer the thickness of the second photoresist layer in different exposure areas to the first photoresist film to form the first photoresist layer.

[0007] Preferably, in the method for optimizing the thickness of the photoresist, the exposure energy of each exposure area is adjusted to be different, and the exposure energy of the exposure area is adjusted to be distributed in a step-wise manner along the radial direction of the semiconductor substrate.

[0008] Preferably, in the method for optimizing the thickness of a photoresist, the first photoresist layer and the second photoresist layer are photoresist layers of different types.

[0009] Preferably, in the method for optimizing the photoresist thickness, a first anti-reflection layer is coated between the first photoresist film and the semiconductor substrate, and / or a second anti-reflection layer is coated between the second photoresist film and the first photoresist film.

[0010] Preferably, in the method for optimizing the thickness of the photoresist, the etching process includes an oxygen plasma etching process.

[0011] Preferably, in the method for optimizing the thickness of the photoresist, the mask plate includes a plurality of the mask patterns, and the plurality of the mask patterns are arranged in sequence in rows or columns on the mask plate.

[0012] Preferably, in the method for optimizing the thickness of the photoresist, the mask pattern includes isolated lines, isolated grooves, dense lines, dense grooves or holes.

[0013] Preferably, in the method for optimizing the photoresist thickness, a film thickness meter is used to measure the thickness value of the first photoresist layer in each of the exposure areas; and a line width scanning test electron microscope is used to measure the critical dimensions of the same mask pattern in each of the exposure areas.

[0014] Preferably, in the method for optimizing the photoresist thickness, the photoresist thickness value corresponding to the highest point or the photoresist thickness value corresponding to the lowest point in the photoresist thickness and critical dimension relationship curve is used as the preferred value of the photoresist thickness.

[0015] In summary, the present invention forms a first photoresist layer on a semiconductor substrate, and makes the thickness of the first photoresist layer in different exposure areas different, then forms a mask pattern in each exposure area, and then measures the critical dimensions between the same mask patterns in each exposure area, prepares a photoresist thickness and critical dimension relationship curve according to the critical dimension and the corresponding photoresist thickness, and adjusts the photoresist thickness according to the photoresist thickness and critical dimension relationship curve, thereby achieving the acquisition of different photoresist thicknesses and their corresponding critical dimensions through a single semiconductor substrate to adjust the photoresist thickness. Compared with the prior art of using 10 to 20 semiconductor substrates, this method can save costs, simplify process steps and time, and save manpower. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a flow chart of a method for optimizing photoresist thickness according to an embodiment of the present invention;

[0017] Figure 2 is a schematic diagram of a device structure corresponding to step S11 of the method for optimizing the thickness of the photoresist according to an embodiment of the present invention;

[0018] Figure 3-4 They are respectively a cross-sectional view and a top view of a device structure corresponding to step S12 of the method for optimizing the photoresist thickness according to an embodiment of the present invention;

[0019] Figure 5 is a schematic diagram of a device structure corresponding to step S13 of the method for optimizing the thickness of the photoresist according to an embodiment of the present invention;

[0020] Figure 6 is a schematic diagram of forming a mask pattern in step S3 of the method for optimizing the thickness of the photoresist according to an embodiment of the present invention;

[0021] Figure 7 is a schematic diagram of a relationship curve between photoresist thickness and critical dimensions produced by a method for optimizing photoresist thickness according to an embodiment of the present invention;

[0022] Wherein, each figure is marked as:

[0023] 10- semiconductor substrate;

[0024] 11-Exposure area;

[0025] 20-a first photoresist film;

[0026] 21-a first photoresist layer;

[0027] 30-a second photoresist film;

[0028] 31- a second photoresist layer;

[0029] 40-mask pattern;

[0030] 210- first anti-reflection layer;

[0031] 310 - Second anti-reflection layer. DETAILED DESCRIPTION

[0032] The following is a further detailed description of a method for optimizing the thickness of the photoresist proposed by the present invention in conjunction with the accompanying drawings and specific embodiments. It should be noted that the accompanying drawings are all in a very simplified form and use an inaccurate scale, which is only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention. In addition, the structure shown in the accompanying drawings is often a part of the actual structure. In particular, the emphasis of each accompanying drawing is different, and sometimes different scales are used.

[0033] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0034] See also Figure 1 , an embodiment of the present invention provides a method for optimizing the thickness of a photoresist, comprising:

[0035] S1, forming a first photoresist layer on the surface of a semiconductor substrate, wherein the thickness of the first photoresist layer in different exposure areas is different;

[0036] S2, obtaining a thickness value of the first photoresist layer in each of the exposure areas;

[0037] S3, exposing and developing each of the exposure areas one by one, and transferring the mask pattern on the mask plate to each of the exposure areas, wherein the exposure parameters for exposing each of the exposure areas are the same; and

[0038] S4, measuring the critical dimension of the same mask pattern in each exposure area, and making a photoresist thickness and critical dimension relationship curve according to the critical dimension of each mask pattern and the corresponding thickness of the first photoresist layer, and adjusting the photoresist thickness according to the photoresist thickness and critical dimension relationship curve.

[0039] The embodiment of the present invention can collect key dimensions of different photoresist thicknesses and their corresponding mask patterns on a single semiconductor substrate. Compared with the prior art that uses 10 to 20 semiconductor substrates, it can save costs, simplify process steps and time, and save manpower.

[0040] The following combination Figure 2 to Figure 7 Steps S1 to S4 are described in further detail.

[0041] First, execute step S1, see Figure 2 to Figure 5 , a first photoresist layer 21 is formed on the semiconductor substrate 10, and the thickness of the first photoresist layer 21 located in different exposure areas 11 is different.

[0042] In this embodiment, subsequent steps are performed on the semiconductor substrate 10 to produce a photoresist thickness and critical dimension relationship curve to adjust and optimize the photoresist thickness. The semiconductor substrate 10 may be in different process stages. For example, the semiconductor substrate 10 may be a semiconductor substrate 10 that has previously undergone a deposition process and has a plurality of film layers formed on the surface. In some other application scenarios, a wafer may also be provided, the wafer including the semiconductor substrate 10. Optionally, the wafer may be a product wafer or a test wafer. Without departing from the spirit of the present invention, replacements made to the semiconductor substrate 10 are all within the scope of protection of the embodiments of the present invention.

[0043] Specifically, in this embodiment, step S1 includes the following sub-steps S11 to S13:

[0044] First, execute sub-step S11, such as Figure 2 As shown, a first photoresist film 20 is formed on a semiconductor substrate 10, and a second photoresist film 30 is formed on the first photoresist film 20. The first photoresist film 20 in each region on the semiconductor substrate 10 has the same thickness, and the second photoresist film 30 in each region has the same thickness. Optionally, the first photoresist film 20 and the second photoresist film 30 are coated by spin coating.

[0045] Optionally, the thickness of the first photoresist film 20 is The thickness of the second photoresist film 30 is

[0046] Next, execute sub-step S12, such as Figure 3 and Figure 4 , the second photoresist film 30 is exposed. Preferably, the exposure is performed without a mask, so that no photolithography pattern is formed on the second photoresist film 30, and it is ensured that only the thickness of the second photoresist film 30 changes after development, thereby providing a change in the independent variable for the subsequent photoresist thickness and key dimension relationship curve.

[0047] In this embodiment, the second photoresist film 30 is exposed by an exposure machine and a plurality of exposure regions 11 are formed on the second photoresist film 30. It should be understood that the formation position of the exposure region 11 is related to the parameters of the exposure machine and has nothing to do with the carrier for forming the exposure region 11. Before exposing the second photoresist film 30, the exposure energy for forming each exposure region 11 is adjusted to be different. After the exposure, the second photoresist film 30 is developed so that the second photoresist film 30 located in different exposure regions 11 has different thicknesses after development, so as to form a Figure 3 A second photoresist layer 31 is shown.

[0048] It can be understood that the "exposure area 11" in this embodiment is used to provide a formation area for the subsequent formation of the mask pattern 40. Therefore, this embodiment does not limit the size and number of the exposure area 11. All exposure areas 11 that can provide a formation area for the subsequent formation of the mask pattern 40 are within the protection scope of this embodiment.

[0049] In this embodiment, the photoresists contained in the first photoresist film 20 and the second photoresist film 30 are both positive photoresists. Since the photoactive components excited by the same photoresist layer are different under different exposure energies, the photoresist layers containing different photoactive components have different solubility in the developer, that is, the same photoresist layer under different exposure energies has different solubility in the developer. Therefore, on the one hand, in this embodiment, by adjusting the exposure energy of each exposure area 11 to be different, the thickness of the second photoresist layer 31 located in different exposure areas 11 can be different; on the other hand, since the exposure energy of the same exposure area 11 is consistent, the thickness of the second photoresist layer 31 located in the same exposure area 11 can also be guaranteed to be the same and uniform. In some other embodiments, the first photoresist and the second photoresist can also be negative photoresists. On this basis, the energy of each exposure unit 11 is adjusted to be different, which can also achieve the above two effects.

[0050] The first photoresist film 20 and the second photoresist film 30 may be i-line type, KrF type, ArF type, iArF type, EUV type photoresist. Accordingly, the type of the exposure machine for exposing the first photoresist film 20 corresponds to the type of the first photoresist film 20, and the type of the exposure machine for exposing the second photoresist film 30 corresponds to the type of the second photoresist film 30. For example, if the first photoresist film 20 is an ArF type photoresist layer, the corresponding exposure machine is an ArF photolithography machine.

[0051] In this embodiment, the first photoresist film 20 and the second photoresist film 30 are different types of photoresist layers. Since each type of photoresist layer undergoes a chemical reaction only under a light source of a specific wavelength, the first photoresist film 20 and the second photoresist film 30 are of different types, which can effectively avoid affecting the physical and chemical properties of the first photoresist layer 20 when the initial second photoresist 30 is exposed.

[0052] For further information, please see Figure 2 and Figure 3 A first anti-reflection layer 210 is coated between the first photoresist film 20 and the semiconductor substrate 10, and / or a second anti-reflection layer 310 is coated between the second photoresist film 30 and the first photoresist layer 20, which is beneficial to reduce the reflection of light on the surface of the first photoresist film 20 and the second photoresist film 30 during the exposure process. The thickness of the first anti-reflection layer 210 is, for example, The thickness of the second anti-reflection layer 310 is, for example,

[0053] Considering that the thickness of the photoresist and the corresponding critical dimensions need to be collected later, in order to facilitate the preparation of the relationship curve between the photoresist thickness and the critical dimensions, in a preferred solution, the exposure energy of each exposure area 11 is adjusted to be different, and the exposure energy of the exposure area 11 is adjusted to be distributed in a stepped manner along the radial direction of the semiconductor substrate 10. Figure 3 and Figure 4 As shown, Figure 3 and Figure 4 The exposure energy of the exposure area 11 is distributed in a step-by-step manner along the radial direction of the semiconductor substrate 10. In this embodiment, the semiconductor substrate 10 is a wafer, that is, the radial direction of the semiconductor substrate 10 is the diameter direction of the wafer, that is, the thickness of the corresponding second photoresist layer 31 is increased or decreased along the diameter direction of the wafer. Figure 3 In this embodiment, the thickness of the second photoresist layer 31 decreases gradually along the radial direction of the semiconductor substrate 10. Compared with the random correspondence between the second photoresist layer 31 of different thicknesses and the exposure regions 11 at different positions, the regular distribution is more convenient for the subsequent preparation of the relationship curve between the photoresist thickness and the critical dimension.

[0054] Furthermore, the thickness difference between the second photoresist layer 31 and two adjacent exposure areas 11 is As an implementation, see Figure 4 The exposure regions 11a, 11b and 11c are sequentially distributed along the radial direction of the semiconductor substrate 10, and the thickness of the second photoresist layer 31 at the exposure region 11a is The thickness of the second photoresist layer 31 in the exposure area 11b is The thickness of the second photoresist layer 31 in the exposure area 11c is The same goes for this process until the last exposure region 11 distributed along the radial direction of the semiconductor substrate 10 is reached.

[0055] Finally, sub-step S13 is performed to perform an etching process on the first photoresist film 20 to transfer the thickness of the second photoresist layer 30 located in the different exposure areas 11 to the first photoresist film 20, thereby obtaining Figure 5 The first photoresist layer 21 is shown. Then, the first photoresist layer 21 is exposed again, which can ensure that the first photoresist layer 21 and the second photoresist layer 31 are only exposed once, so that when the first photoresist layer 21 is exposed later, its optical performance is in a better state.

[0056] In this embodiment, please continue to refer to Figure 3 After obtaining the second photoresist layer 31, the thickness of the second photoresist layer 31 located in each exposure area 11, the thickness of the second anti-reflection layer 310 and the initial thickness of the first photoresist 20 are measured, and according to the etching rate of the second photoresist layer 31, the etching rate of the second anti-reflection layer 310 and the etching rate of the first photoresist film 20 under the set etching conditions, the etching time is calculated to obtain the first photoresist layer 21, and the thickness of the first photoresist layer 21 located in each exposure area 11 is consistent with the thickness of the second photoresist layer 31 previously located in the corresponding exposure area 11. Among them, the etching rates of the second photoresist layer 31, the second anti-reflection layer 310 and the first photoresist film 20 under the set etching conditions can be obtained according to previous experience.

[0057] Optionally, the second photoresist layer 31 , the second anti-reflection layer 310 and the first photoresist film 20 are etched into carbon dioxide and gaseous water by an oxygen plasma etching process.

[0058] After the etching process is performed, the semiconductor substrate 10 is backwashed to remove impurities and contamination on the back of the first photoresist layer 21 after the etching process. As an embodiment, the semiconductor substrate 10 is wet cleaned, and the cleaning solution of the wet cleaning includes ammonia water, hydrogen peroxide and deionized water.

[0059] After executing step S1, then, step S2 is executed to obtain the thickness value of the first photoresist layer 21 of each exposure area 11. Optionally, the method for obtaining the thickness value of the first photoresist layer 20 may be to directly use the thickness of the second photoresist layer 31 obtained when previously executing sub-step S13 as the thickness of the first photoresist layer 21. In this embodiment, in order to ensure the accuracy of the relationship curve between the thickness of the manufactured photoresist and the critical dimension, the thickness of the first photoresist layer 21 is measured after the etching process is performed, and the measuring tool is a film thickness measuring instrument.

[0060] Next, execute step S3, see Figure 6 , each exposure area 11 is exposed and developed one by one, and the mask pattern 40 on the mask is transferred to each exposure area 11. The exposure parameters for exposing each exposure area 11 are the same.

[0061] The mask plate includes a plurality of mask patterns 40 , each mask pattern 40 corresponds to a critical dimension, and the plurality of mask patterns 40 are sequentially arranged in rows or columns on the mask plate.

[0062] Specifically, the mask pattern 40 includes isolated lines, isolated grooves, dense lines, dense grooves or holes, such as Figure 6 As shown, the mask pattern 40 in this embodiment is an isolated trench.

[0063] It should be noted that in step S3, the parameters of the exposure machine are adjusted so that the size and position of the exposure area 11 formed by this exposure are consistent with the size and position of the exposure area 11 formed by the exposure machine when exposing the second photoresist film 30. On this basis, the mask pattern 40 on the mask plate is transferred to each exposure area 11.

[0064] When executing step S3 , each exposure region 11 is exposed and developed one by one. After exposure and development, a plurality of mask patterns 40 appear in each exposure region 11 , that is, each exposure region 11 appears with all types of mask patterns 40 .

[0065] Furthermore, the exposure parameters of each exposure area 11 are set the same, so that the controlled variable is only the photoresist thickness, which is not affected by the exposure parameters.

[0066] Finally, step S4 is performed to measure the critical dimensions of the same mask pattern 40 in each exposure area 11, such as Figure 6 As shown, the critical dimension CD between the same mask patterns 40 in the plurality of exposure regions 11 is measured, and according to the critical dimension of each mask pattern 40 and the thickness of the corresponding first photoresist layer 20, a method as shown in FIG. Figure 7The relationship curve between photoresist thickness and critical dimension shown in the figure has the horizontal axis representing the photoresist thickness and the vertical axis representing the critical dimension, and the photoresist thickness is adjusted according to the relationship curve between photoresist thickness and critical dimension.

[0067] For details, see Figure 7 The photoresist thickness corresponding to the highest point M or the lowest point N of the photoresist thickness and key dimension relationship curve is taken as the preferred value of the photoresist thickness. Since the slope at the highest point M or the lowest point N of the curve is smaller than the slope at other positions of the curve, even if the photoresist thickness changes, the key dimension can be guaranteed to change in a small range. In this way, large deviations in the photolithography key dimensions caused by photoresist thickness errors caused by factors such as uneven coating can be avoided.

[0068] After step S4, a plurality of mask patterns 40 appear in each exposure area 11. Therefore, when preparing the relationship curve between the photoresist thickness and the critical dimension, it is necessary to consider that the plurality of mask patterns 40 correspond to different critical dimensions. That is, a plurality of sets of relationship curves between the photoresist thickness and the critical dimension can be prepared through the embodiment of the present invention.

[0069] Optionally, a line width scanning electron microscope is used to measure the critical dimension of the same mask pattern 40 in each exposure area 11 .

[0070] In summary, an embodiment of the present invention provides a method for optimizing photoresist thickness, by forming a first photoresist layer on a semiconductor substrate, and making the thickness of the first photoresist layer in different exposure areas different, then forming a mask pattern in each exposure area, and then measuring the critical dimensions between the same mask patterns in each exposure area, making a photoresist thickness and critical dimension relationship curve according to the critical dimensions and the corresponding photoresist thickness, and adjusting the photoresist thickness according to the photoresist thickness and critical dimension relationship curve, thereby achieving the acquisition of different photoresist thicknesses and their corresponding critical dimensions through a single semiconductor substrate to adjust the photoresist thickness. Compared with the prior art of using 10 to 20 semiconductor substrates, it can save costs, simplify process steps and time, and save manpower.

[0071] In addition, it should be recognized that although the present invention application has been disclosed as 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, the technical content disclosed above can be used to make many possible changes and modifications to the technical solution of the present invention, or modified into equivalent embodiments of equivalent changes. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the scope of protection of the technical solution of the present invention.

Claims

1. A method for optimizing the thickness of a photoresist, characterized in that: include: Forming a first photoresist layer on a semiconductor substrate, wherein the thickness of the first photoresist layer in different exposure areas is different; Obtaining a thickness value of the first photoresist layer in each of the exposure areas; Exposing and developing each of the exposure areas one by one, and transferring the mask pattern on the mask plate to each of the exposure areas, wherein the exposure parameters for exposing each of the exposure areas are the same; as well as, Measure the critical dimension of the same mask pattern in each exposure area, and produce a photoresist thickness and critical dimension relationship curve based on the critical dimension of each mask pattern and the corresponding thickness of the first photoresist layer, and adjust the photoresist thickness based on the photoresist thickness and critical dimension relationship curve.

2. The method for optimizing the thickness of the photoresist as claimed in claim 1, characterized in that: The method of forming the first photoresist layer includes: forming a first photoresist film on the semiconductor substrate, and forming a second photoresist film on the first photoresist film; exposing the second photoresist film, wherein the exposure energy for each of the exposure areas is different; developing the second photoresist film to form a second photoresist layer, wherein the thickness of the second photoresist layer in different exposure areas is different; and, An etching process is performed on the first photoresist film to transfer the thickness of the second photoresist layer in different exposure areas to the first photoresist film to form the first photoresist layer.

3. The method for optimizing the thickness of the photoresist as claimed in claim 2, characterized in that: The exposure energy of each exposure area is adjusted to be different, and the exposure energy of the exposure area is adjusted to be distributed in a step-wise manner along the radial direction of the semiconductor substrate.

4. The method for optimizing the thickness of the photoresist as claimed in claim 2, characterized in that: The first photoresist layer and the second photoresist layer are photoresist layers of different types.

5. The method for optimizing the thickness of the photoresist as claimed in claim 2, characterized in that: Also includes: A first anti-reflection layer is coated between the first photoresist film and the semiconductor substrate, and / or a second anti-reflection layer is coated between the second photoresist film and the first photoresist film.

6. The method for optimizing the thickness of the photoresist as claimed in claim 2, characterized in that: The etching process includes an oxygen plasma etching process.

7. The method for optimizing the thickness of photoresist according to claim 1, characterized in that: The mask plate includes a plurality of mask patterns, and the plurality of mask patterns are arranged in sequence in rows or columns on the mask plate.

8. The method for optimizing the thickness of the photoresist as claimed in claim 7, characterized in that: The mask pattern includes isolated lines, isolated grooves, dense lines, dense grooves or holes.

9. The method for optimizing photoresist thickness as claimed in claim 1, characterized in that: The thickness of the first photoresist layer in each exposure area is measured by using a film thickness measuring instrument; and the critical dimension of the same mask pattern in each exposure area is measured by using a line width scanning test electron microscope.

10. The method for optimizing photoresist thickness according to claim 1, characterized in that: The photoresist thickness value corresponding to the highest point or the photoresist thickness value corresponding to the lowest point in the photoresist thickness and critical dimension relationship curve is taken as the preferred value of the photoresist thickness.

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