Wafer photoresist coating method

Abstract

The application provides a wafer photoresist coating method, relates to the field of semiconductor technology manufacturing, and particularly relates to a photoresist coating method. The method comprises the following steps: obtaining a wafer to be coated; preparing a base photoresist according to film thickness requirements, wherein the base photoresist comprises a diluent and a positive photoresist, and the volume ratio of the diluent to the positive photoresist is greater than or equal to 3 and less than or equal to 10; spin-coating the base photoresist on the wafer to be coated, so that a wetting layer is formed on the surface of the wafer to be coated; and spin-coating the positive photoresist on the wetting layer, so that a photoresist film is formed on the surface of the wafer to be coated. The wafer photoresist coating method provided by the application uses the base photoresist formed by the diluent and the positive photoresist to replace the traditional wetting agent, avoids the problem that some substrates cannot be sprayed with the wetting agent, improves the problem of uneven photoresist film thickness and poor flowability of the thick film in the current mainstream thick photoresist mask preparation technology, improves the thickness uniformity of the photoresist film, and is beneficial to improving the yield of production.

Description

Technical Field

[0001] This invention relates to the field of semiconductor manufacturing technology, and in particular to a photoresist coating method. Background Technology

[0002] In the field of MEMS (Micro-Electro-Mechanical System), there are strict requirements for the uniformity of the photoresist film thickness. Existing photolithography technology in the MEMS field is mostly based on thick photoresist. However, the photoresist film thickness obtained based on existing thick photoresist mask preparation technology often has the problem of uneven thickness, which leads to a large distortion rate of the pattern during the photolithography pattern transfer process, which has a serious negative impact on the yield rate of production and is not conducive to further control of production costs. Summary of the Invention

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art or related art.

[0004] Therefore, the present invention provides a method for wafer photoresist coating, the method comprising:

[0005] Obtain the wafer to be coated;

[0006] According to the film thickness requirements, a base photoresist is prepared. The base photoresist includes a diluent and a positive photoresist. The volume ratio of the diluent to the positive photoresist is greater than or equal to 3 and less than or equal to 10.

[0007] The above-mentioned base photoresist is spin-coated onto the wafer to be coated, so as to form a wetting layer on the surface of the wafer to be coated;

[0008] The positive photoresist is spin-coated onto the aforementioned wetting layer to form a photoresist film on the surface of the wafer to be coated.

[0009] In one feasible implementation, the preparation of the substrate photoresist according to the aforementioned film thickness requirement includes:

[0010] Based on the above film thickness requirements, determine the target film thickness;

[0011] Based on the target film thickness, the volume ratio of the diluent to the positive photoresist is determined, and the volume ratio decreases as the target film thickness increases.

[0012] The above-mentioned base photoresist was prepared according to the above volume ratio.

[0013] In one feasible implementation, the method of spin-coating the substrate photoresist onto the wafer to be coated to form a wetting layer on the surface of the wafer includes:

[0014] The base photoresist is spin-coated onto the wafer to be coated according to the first wafer rotation speed and the first rotation duration. The first wafer rotation speed is greater than or equal to 50 rpm and less than or equal to 200 rpm, and the first rotation duration is greater than or equal to 5 s and less than or equal to 10 s.

[0015] Based on the first uniform coating rotation parameters, the wafer to be coated is controlled to perform the first uniform coating rotation.

[0016] The wafer to be coated is baked according to a first baking temperature and a first baking time, wherein the first baking temperature is greater than or equal to 60°C and less than or equal to 120°C, and the first baking time is greater than or equal to 1 min and less than or equal to 5 min.

[0017] The wafer to be coated is cooled according to a first cooling temperature and a first cooling time to form a wetting layer on the surface of the wafer to be coated. The first cooling temperature is greater than or equal to 22°C and less than or equal to 28°C, and the first cooling time is greater than or equal to 30s and less than or equal to 100s.

[0018] In one feasible implementation, controlling the wafer to be coated to rotate according to the first spin coating rotation parameters includes:

[0019] The rotation of the wafer to be coated is controlled according to the second wafer rotation speed and the second rotation duration. The second wafer rotation speed is greater than or equal to 1000 rpm and less than or equal to 2000 rpm, and the second rotation duration is greater than or equal to 2s and less than or equal to 5s.

[0020] Adjust the rotation speed of the wafer to be coated to the third wafer rotation speed, wherein the third wafer rotation speed is greater than or equal to 80 rpm and less than or equal to 200 rpm;

[0021] Based on the third rotation duration, the wafer to be coated is controlled to rotate at an accelerated speed according to the third wafer rotation speed, wherein the third rotation duration is greater than or equal to 15s and less than or equal to 30s.

[0022] The rotation of the wafer to be coated is controlled according to the fourth wafer rotation speed and the fourth rotation duration. The fourth wafer rotation speed is greater than or equal to 1000 rpm and less than or equal to 4000 rpm, and the fourth rotation duration is greater than or equal to 10s and less than or equal to 20s.

[0023] In one feasible implementation, controlling the wafer to be coated to rotate at an accelerated speed according to the third rotation duration includes:

[0024] Based on the third wafer rotation speed and the first rotor duration, the wafer to be coated is controlled to rotate, and the first rotor duration is greater than or equal to 5s and less than or equal to 10s.

[0025] The rotation of the wafer to be coated is controlled according to the rotation speed of the fifth wafer and the duration of the second rotor. The rotation speed of the fifth wafer is greater than 200 rpm and less than or equal to 400 rpm, and the duration of the second rotor is greater than or equal to 5s and less than or equal to 10s.

[0026] The rotation of the wafer to be coated is controlled according to the rotation speed of the sixth wafer and the duration of the third rotor. The rotation speed of the sixth wafer is greater than 400 rpm and less than or equal to 600 rpm, and the duration of the third rotor is greater than or equal to 5s and less than or equal to 10s.

[0027] In one feasible implementation, the above-mentioned spin coating of the positive photoresist onto the wetting layer to form a photoresist film on the surface of the wafer to be coated includes:

[0028] The rotation of the wafer to be coated is controlled according to the seventh wafer rotation speed and the fifth rotation duration. The seventh wafer rotation speed is greater than 200 rpm and less than or equal to 600 rpm, and the fifth rotation duration is greater than or equal to 5s and less than or equal to 10s.

[0029] The positive photoresist is spin-coated onto the wafer to be coated according to the eighth wafer rotation speed and the sixth rotation duration. The eighth wafer rotation speed is greater than or equal to 20 rpm and less than or equal to 50 rpm, and the sixth rotation duration is greater than or equal to 10 s and less than or equal to 50 s.

[0030] Based on the second spin coating rotation parameters, control the above-mentioned wafer to be coated to perform the second spin coating rotation.

[0031] Clean the wafer to be coated;

[0032] The wafer to be coated is baked according to the second baking temperature and the second baking time to form a photoresist film on the surface of the wafer to be coated. The second baking temperature is greater than or equal to 60°C and less than or equal to 120°C, and the second baking time is greater than or equal to 5 min and less than or equal to 30 min.

[0033] In one feasible implementation, controlling the wafer to be coated to rotate in a second spin coating process according to the second spin coating rotation parameters includes:

[0034] Adjust the rotation speed of the wafer to be coated to the ninth wafer rotation speed, wherein the ninth wafer rotation speed is greater than or equal to 60 rpm and less than or equal to 100 rpm;

[0035] Based on the seventh rotation duration, the above-mentioned wafer to be coated is controlled to rotate at an accelerated speed from the above-mentioned ninth wafer rotation speed, and the above-mentioned seventh rotation duration is greater than or equal to 30s and less than or equal to 150s.

[0036] The rotation of the wafer to be coated is controlled according to the tenth wafer rotation speed and the eighth rotation duration. The tenth wafer rotation speed is greater than or equal to 800 rpm and less than or equal to 3500 rpm, and the eighth rotation duration is greater than or equal to 10 s and less than or equal to 20 s.

[0037] In one feasible implementation, controlling the wafer to be coated to rotate at an accelerated speed from the ninth wafer rotation speed according to the seventh rotation duration includes:

[0038] Based on the above-mentioned ninth wafer rotation speed and fourth rotor duration, the above-mentioned wafer to be coated is controlled to rotate, and the above-mentioned fourth rotor duration is greater than or equal to 10s and less than or equal to 50s.

[0039] The rotation of the eleventh wafer is controlled according to the rotation speed of the eleventh wafer and the duration of the fifth rotor. The rotation speed of the eleventh wafer is greater than 100 rpm and less than or equal to 200 rpm, and the duration of the fifth rotor is greater than or equal to 10 s and less than or equal to 50 s.

[0040] The rotation of the wafer to be coated is controlled according to the rotation speed of the twelfth wafer and the duration of the sixth rotor. The rotation speed of the twelfth wafer is greater than 200 rpm and less than or equal to 400 rpm, and the duration of the sixth rotor is greater than or equal to 10 s and less than or equal to 50 s.

[0041] In one feasible implementation, the diluent is EBR7030;

[0042] The positive photoresist mentioned above is AZ40 or AZP4680.

[0043] In one feasible implementation, the wafer photoresist coating method further includes:

[0044] Obtain the wafer body;

[0045] At a third preset temperature, an adhesive is applied to the wafer body to obtain a pre-prepared wafer;

[0046] The prepared wafer is kept at the third preset temperature for a first preset time to obtain the wafer to be coated.

[0047] Compared with the prior art, the present invention has at least the following beneficial effects: The embodiments of this application provide a wafer photoresist coating method, the method comprising: obtaining a wafer to be coated; preparing a base photoresist according to the film thickness requirements; the base photoresist comprising a diluent and a positive photoresist, wherein the volume ratio of the diluent to the positive photoresist is greater than or equal to 3 and less than or equal to 10; spin-coating the base photoresist onto the wafer to be coated to form a wetting layer on the surface of the wafer to be coated; and spin-coating the positive photoresist onto the formed wetting layer to form a photoresist film on the surface of the wafer to be coated. The wafer photoresist coating method provided in this application adjusts the volume ratio of diluent to positive photoresist based on the desired photoresist film thickness to prepare a base photoresist. The base photoresist is then spin-coated onto the desired wafer surface to form a wetting layer. Since the base photoresist contains positive photoresist, there is good miscibility between the base photoresist and the positive photoresist. Therefore, during the coating of the positive photoresist, the wetting layer can improve the flowability of the positive photoresist, allowing the positive photoresist to be more readily absorbed during the spin-coating process. The photoresist spreads more evenly to form a photoresist film with a more uniform thickness. Furthermore, the wetting layer formed based on the aforementioned base photoresist has good adhesion, reducing the requirements of the wetting layer on the substrate and making it easier to adhere to the wafer. This ensures the wetting effect during the coating of positive photoresist and facilitates the uniform spread of positive photoresist during spin coating to form a photoresist film with a more uniform thickness. This, in turn, helps to reduce the distortion rate of the pattern during the photolithography pattern transfer process, improves the production yield, and reduces production costs. Attached Figure Description

[0048] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of exemplary embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0049] Figure 1 This is a schematic flowchart illustrating a wafer photoresist coating method according to one embodiment of this application. Detailed Implementation

[0050] Exemplary embodiments of the present application will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present application are shown in the drawings, it should be understood that the present application may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this application will be thorough and complete, and will fully convey the scope of the present application to those skilled in the art.

[0051] This application provides a method for wafer photoresist coating, such as... Figure 1As shown, the method may include:

[0052] Step S110: Obtain the wafer to be coated;

[0053] Understandably, a wafer is a silicon chip used to make silicon semiconductor circuits. Its raw material is silicon, and it is called a wafer because of its circular shape.

[0054] Step S120: Prepare a base photoresist according to the film thickness requirement. The base photoresist includes a diluent and a positive photoresist. The volume ratio of the diluent to the positive photoresist is greater than or equal to 3 and less than or equal to 10.

[0055] It is understood that the aforementioned film thickness requirement reflects the desired film thickness of the photoresist film to be formed on the wafer to be coated. The photoresist comprises a diluent and a positive photoresist, which can be obtained by diluting the positive photoresist with the addition of a diluent. The volume ratio of the diluent to the positive photoresist can be greater than or equal to 3 and less than or equal to 10. In practical applications, the aforementioned volume ratio can be determined in conjunction with the aforementioned film thickness requirement. It is easy to understand that the viscosity of the base photoresist decreases as the aforementioned volume ratio increases, and correspondingly, the wetting performance of the wetting layer increases as the aforementioned volume ratio increases.

[0056] Furthermore, by limiting the volume ratio to be greater than or equal to 3 and less than or equal to 10, it is possible to avoid the viscosity of the base photoresist being too high or too low. This can prevent poor wetting performance of the wetting layer, which is beneficial to ensuring the wetting effect of the wetting layer on the positive photoresist during spin coating. On the other hand, it can prevent the base photoresist from detaching from the wafer surface, ensuring the adhesion of the wetting layer, so as to wet the subsequent spin-coated positive photoresist and provide further assurance for the formation of a photoresist film with uniform thickness.

[0057] It should be noted that the aforementioned diluent can be a photoresist diluent used to dilute positive photoresist.

[0058] Step S130: Spin-coat the above-mentioned base photoresist onto the wafer to be coated, so as to form a wetting layer on the surface of the wafer to be coated;

[0059] It should be noted that in the photolithography technology of the MEMS field, the required film thickness is generally between tens and hundreds of micrometers. Therefore, the photoresist film is generally quite thick, with poor fluidity and uneven thickness distribution. Existing technologies improve this problem by spraying wetting agents between photoresist coatings. However, since wetting agents are difficult to adapt to all substrates, some substrates cannot be sprayed with wetting agents, resulting in poor wetting effect during photoresist coating, which in turn leads to weak fluidity of the photoresist and low thickness uniformity after film formation. The wafer photoresist coating method provided in this application can form a wetting layer on the wafer surface by coating the above-mentioned base photoresist on the wafer. The base photoresist includes a positive photoresist. This means the positive photoresist in the base photoresist is the same as the positive photoresist subsequently spin-coated. The base photoresist and the positive photoresist can undergo isotropic dissolution. Therefore, on the one hand, the base photoresist and the subsequently spin-coated positive photoresist have good miscibility, improving the wettability of the substrate surface. This allows the wetting layer to improve the flowability of the positive photoresist during coating. On the other hand, the base photoresist has good adhesion, reducing the substrate requirements of the wetting layer and making it easier to adhere to the wafer, thus ensuring the wetting effect of the positive photoresist during subsequent coating.

[0060] Step S140: Spin-coat the positive photoresist onto the above wetting layer to form a photoresist film on the surface of the wafer to be coated.

[0061] It should be noted that, by spin-coating the surface of the wetting layer formed in step S130, positive photoresist is applied to the wafer to be coated, so that a photoresist film meeting the above-mentioned film thickness requirements is formed on the surface of the wafer to be coated.

[0062] In this scheme, based on the required photoresist film thickness, the volume ratio of diluent to positive photoresist is adjusted to prepare a base photoresist. The base photoresist is then spin-coated onto the desired wafer surface to form a wetting layer. Since the base photoresist contains positive photoresist, there is good miscibility between the base photoresist and the positive photoresist, which improves the wettability of the substrate surface. Consequently, when coating the positive photoresist, the wetting layer can be used to improve the flowability of the positive photoresist, allowing it to spread more evenly during the spin-coating process, thus forming a photoresist film with a more uniform thickness. This helps to reduce the distortion rate of the pattern during photolithography pattern transfer, improve the production yield, and reduce production costs.

[0063] In one feasible embodiment, the above-described wafer photoresist coating method, according to the film thickness requirements, prepares a first photoresist, including:

[0064] Based on the above film thickness requirements, determine the target film thickness;

[0065] Based on the target film thickness, the volume ratio of the diluent to the positive photoresist is determined, and the volume ratio decreases as the target film thickness increases.

[0066] The above-mentioned base photoresist was prepared according to the above volume ratio.

[0067] In this technical solution, the target film thickness is the desired thickness of the photoresist film to be formed on the surface of the wafer to be coated. It can be understood that, in the embodiments of this application, the target film thickness includes the thickness of the wetting layer and the thickness of the positive photoresist layer formed on the wetting layer based on spin-coated positive photoresist.

[0068] Furthermore, the volume ratio of the diluent to the positive photoresist in the base photoresist can be determined based on the target film thickness. This volume ratio decreases as the required film thickness increases, and the volume ratio of the diluent to the positive photoresist in the base photoresist can be 3 to 10. The specific value of the volume ratio can be selected based on the target film thickness. It should be noted that the larger the target film thickness, the lower the required fluidity of the positive photoresist during spin coating, and correspondingly, the lower the requirement for the wetting performance of the wetting layer. As a result, the volume occupied by the positive photoresist in the base photoresist is larger, which is reflected in the smaller volume ratio. Conversely, the smaller the target film thickness, the higher the required fluidity of the positive photoresist during spin coating, and correspondingly, the higher the requirement for the wetting performance of the wetting layer. As a result, the volume occupied by the positive photoresist in the base photoresist is smaller, which is reflected in the larger volume ratio.

[0069] Understandably, given the above volume ratio, the base photoresist can be prepared according to the above volume ratio, that is, the positive photoresist can be diluted with a diluent according to the above volume ratio.

[0070] In one feasible embodiment, the base photoresist is spin-coated onto the wafer to be coated to form a wetting layer on the surface of the wafer, including:

[0071] The base photoresist is spin-coated onto the wafer to be coated according to the first wafer rotation speed and the first rotation duration. The first wafer rotation speed is greater than or equal to 50 rpm and less than or equal to 200 rpm, and the base rotation duration is greater than or equal to 5 s and less than or equal to 10 s.

[0072] Based on the first uniform coating rotation parameters, the wafer to be coated is controlled to perform the first uniform coating rotation.

[0073] The wafer to be coated is baked according to a first baking temperature and a first baking time, wherein the first baking temperature is greater than or equal to 60°C and less than or equal to 120°C, and the first baking time is greater than or equal to 1 min and less than or equal to 5 min.

[0074] The wafer to be coated is cooled according to a first cooling temperature and a first cooling time to form a wetting layer on the surface of the wafer to be coated. The first cooling temperature is greater than or equal to 22°C and less than or equal to 28°C, and the first cooling time is greater than or equal to 30s and less than or equal to 100s.

[0075] In this technical solution, when coating the wafer with base photoresist, the wafer is rotated at a speed of 50 to 200 rpm, with a first rotation duration of 5 to 10 seconds. During this first rotation duration, the photoresist nozzles continuously spray the base photoresist onto the wafer. Based on this action, the base photoresist can quickly cover the surface of the wafer, and by controlling the wafer to rotate at a lower speed, the loss of the base photoresist can be avoided. It is understood that the first wafer rotation speed and the first rotation duration can be selected in conjunction with the aforementioned volume ratio of the base photoresist. If the volume ratio is higher, the viscosity of the base photoresist is lower, and the first wafer rotation speed and the first rotation duration can be correspondingly lower, preventing the base photoresist from detaching from the wafer due to excessive centrifugal force during coating.

[0076] After applying the base photoresist to the wafer to be coated, this method controls the wafer to be coated to undergo a first spin-coating rotation based on the first spin-coating rotation parameters. The first spin-coating rotation refers to the process of uniformly spreading the base photoresist coated on the wafer. It is understood that the aforementioned first spin-coating rotation parameters include, but are not limited to, the wafer rotation speed and rotation duration during the first spin-coating rotation process.

[0077] After performing a photoresist rotation on the wafer to be coated, this method bakes the wafer coated with the base photoresist and then performs a cooling operation to dry the base photoresist coated on the surface of the wafer. During the baking process, the first baking temperature is controlled to be greater than or equal to 60°C and less than or equal to 120°C, and the first baking time is controlled to be greater than or equal to 1 min and less than or equal to 5 min. The first baking temperature and the first baking time can be selected in combination with the amount of base photoresist coated on the wafer. After baking the wafer, the wafer can be cooled according to the first cooling temperature and the first cooling time to form a wetting layer on the surface of the wafer. During the cooling process, the first cooling temperature can be controlled to be greater than or equal to 22°C and less than or equal to 28°C, and the first cooling time can be controlled to be greater than or equal to 30 s and less than or equal to 100 s. It is understandable that the baking and cooling operations in this technical solution can dry the base photoresist, enhance the adhesion between the base photoresist and the surface of the wafer to be coated, and form a more solid wetting layer on the surface of the wafer to be coated. This is beneficial for improving the flowability of the positive photoresist during the subsequent spin coating of positive photoresist, and facilitates the formation of a photoresist layer with a more uniform thickness on the surface of the wafer to be coated.

[0078] For example, the aforementioned first cooling temperature can be 25°C.

[0079] In one feasible embodiment, controlling the wafer to be coated to perform a first spin coating rotation according to the first spin coating rotation parameters includes:

[0080] The rotation of the wafer to be coated is controlled according to the second wafer rotation speed and the second rotation duration. The second wafer rotation speed is greater than or equal to 1000 rpm and less than or equal to 2000 rpm, and the second rotation duration is greater than or equal to 2s and less than or equal to 5s.

[0081] Adjust the rotation speed of the wafer to be coated to the third wafer rotation speed, wherein the third wafer rotation speed is greater than or equal to 80 rpm and less than or equal to 200 rpm;

[0082] Based on the third rotation duration, the wafer to be coated is controlled to rotate at an accelerated speed according to the third wafer rotation speed, wherein the third rotation duration is greater than or equal to 15s and less than or equal to 30s.

[0083] The rotation of the wafer to be coated is controlled according to the fourth wafer rotation speed and the fourth rotation duration. The fourth wafer rotation speed is greater than or equal to 1000 rpm and less than or equal to 4000 rpm, and the fourth rotation duration is greater than or equal to 10s and less than or equal to 20s.

[0084] In this technical solution, during the process of controlling the first spin coating rotation of the wafer to be coated according to the first spin coating rotation parameters, the wafer to be coated can be controlled to rotate with the second wafer speed and the second rotation duration. The second wafer speed is between 1000 rpm and 2000 rpm, and the second rotation duration is between 2 s and 5 s. This operation utilizes a shorter rotation duration and a higher wafer speed to subject the base photoresist to a relatively large centrifugal force, so that the base photoresist on the wafer to be coated changes from a relatively concentrated distribution state to a relatively dispersed distribution state, which facilitates the uniform spread of the base photoresist on the surface of the wafer to be coated.

[0085] It is understandable that the faster the rotation speed of the second wafer, the greater the centrifugal force on the base photoresist, which is more conducive to the dispersion of the base photoresist. Therefore, the rotation speed and the second rotation time of the second wafer can be specifically selected in combination with the volume ratio of the base photoresist. On the one hand, this avoids a large amount of base photoresist detaching from the wafer to be coated during rotation, and on the other hand, it avoids low dispersion of the base photoresist, ensuring that the base photoresist is evenly distributed on the surface of the wafer to be coated.

[0086] After the wafer to be coated is rotated at the second wafer speed and the second rotation duration, this method adjusts the wafer speed to the third wafer speed and controls the wafer to accelerate within the third rotation duration, using the third wafer speed as the starting point. The third wafer speed is between 80 rpm and 200 rpm, and the third rotation duration is between 15 s and 30 s. This operation allows the base photoresist on the wafer to be coated to be evenly spread and cover the surface of the wafer, which is beneficial for subsequent baking and cooling operations. This results in a relatively uniform and evenly distributed wetting layer on the surface of the wafer, providing a reliable wetting effect for the positive photoresist during subsequent spin coating.

[0087] After the wafer to be coated is accelerated and rotated at the third wafer speed and third rotation duration, this method controls the wafer to be coated to rotate at the fourth wafer speed and fourth rotation duration at a higher wafer speed and a longer rotation duration. The fourth wafer speed is between 1000 rpm and 4000 rpm, and the fourth rotation duration is between 10 s and 20 s, so as to further ensure the uniform coating effect of the base photoresist, so as to facilitate the base photoresist to be evenly spread on the wafer surface and form a base photoresist layer of a certain thickness.

[0088] Understandably, based on the aforementioned first spin coating rotation execution method, the uniformity of the distribution of the base photoresist coated on the wafer to be coated can be improved, so as to form a base photoresist layer with a certain thickness and relatively uniform thickness on the surface of the wafer to be coated. This facilitates the formation of a wetting layer on the surface of the wafer to be coated in conjunction with subsequent baking and cooling operations. During the spin coating of positive photoresist, the wetting layer improves the flowability of the positive photoresist at different locations on the wafer to be coated, which is beneficial to improving the thickness uniformity of the photoresist film on the wafer to be coated. This, in turn, helps to reduce the distortion rate of the pattern during the photolithography pattern transfer process, improves the production yield, and reduces production costs.

[0089] In one feasible embodiment, controlling the wafer to be coated to rotate at an accelerated speed according to the third rotation duration includes:

[0090] Based on the third wafer rotation speed and the first rotor duration, the wafer to be coated is controlled to rotate, wherein the first rotor duration is greater than or equal to 5s and less than or equal to 10s.

[0091] The rotation of the wafer to be coated is controlled according to the rotation speed of the fifth wafer and the duration of the second rotor. The rotation speed of the fifth wafer is greater than 200 rpm and less than or equal to 400 rpm, and the duration of the second rotor is greater than or equal to 5s and less than or equal to 10s.

[0092] The rotation of the wafer to be coated is controlled according to the rotation speed of the sixth wafer and the duration of the third rotor. The rotation speed of the sixth wafer is greater than 400 rpm and less than or equal to 600 rpm, and the duration of the third rotor is greater than or equal to 5s and less than or equal to 10s.

[0093] In this technical solution, during the process of controlling the wafer to be coated to accelerate its rotation according to the third wafer rotation speed based on the third rotation duration, this method first controls the wafer to be coated to rotate at the third wafer rotation speed and the first rotation duration, where the first rotation duration is greater than or equal to 5s and less than or equal to 10s. Then, it controls the wafer to be coated to rotate at the fifth wafer rotation speed and the second rotation duration, where the fifth wafer rotation speed is 200rpm to 400rpm and the first rotation duration is greater than or equal to 5s and less than or equal to 10s. Finally, it controls the wafer to be coated to rotate at the sixth wafer rotation speed and the third rotation duration. The rotation speed is 400 rpm to 600 rpm, and the duration of the third rotor is greater than or equal to 5 s and less than or equal to 10 s, thereby controlling the wafer to be coated to rotate in stages. It can be understood that as the base photoresist continues to spread on the surface of the wafer to be coated, the flow resistance of the base photoresist on the surface of the wafer to be coated also increases. Based on the aforementioned control, the base photoresist can be subjected to a staged increase in centrifugal force during rotation, which provides flow power for the base photoresist, making it easier for the base photoresist to spread more evenly on the surface of the wafer to be coated. This is beneficial for subsequent operations to form a wetting layer with a certain thickness and uniform distribution on the surface of the wafer to be coated.

[0094] In one feasible embodiment, the method spin-coats the positive photoresist onto the wetting layer to form a photoresist film on the surface of the wafer to be coated, including:

[0095] The rotation of the wafer to be coated is controlled according to the seventh wafer rotation speed and the fifth rotation duration. The seventh wafer rotation speed is greater than 200 rpm and less than or equal to 600 rpm, and the fifth rotation duration is greater than or equal to 5s and less than or equal to 10s.

[0096] The positive photoresist is spin-coated onto the wafer to be coated according to the eighth wafer rotation speed and the sixth rotation duration. The eighth wafer rotation speed is greater than or equal to 20 rpm and less than or equal to 50 rpm, and the sixth rotation duration is greater than or equal to 10 s and less than or equal to 50 s.

[0097] Based on the second spin coating rotation parameters, control the above-mentioned wafer to be coated to perform the second spin coating rotation.

[0098] Clean the wafer to be coated;

[0099] The wafer to be coated is baked according to the second baking temperature and the second baking time to form a photoresist film on the surface of the wafer to be coated. The second baking temperature is greater than or equal to 60°C and less than or equal to 120°C, and the second baking time is greater than or equal to 5 min and less than or equal to 30 min.

[0100] In this technical solution, when a wetting layer is formed on the surface of the wafer to be coated, the wafer to be coated can be controlled to rotate at the seventh wafer rotation speed and the fifth rotation duration. The seventh wafer rotation speed is 200 rpm to 600 rpm, and the fifth rotation duration is 10 s to 50 s. The centrifugal force generated by the rotation is used to clean the wafer to be coated, especially the adhering substances on the surface of the wetting layer, such as dust, small particles, etc., to improve the cleanliness of the wetting layer surface. This provides favorable conditions for subsequent spin coating of positive photoresist, helps to ensure the wetting effect of the wetting layer on the positive photoresist, and thus improves the thickness uniformity of the photoresist film.

[0101] In the process of spin-coating the aforementioned positive photoresist onto the wafer to be coated, the wafer is controlled to rotate at an eighth wafer speed of 20 rpm to 50 rpm and a sixth rotation duration of 10 s to 50 s during the spin-coating process. It is understood that during the sixth rotation duration, the photoresist nozzle can be controlled to continuously spray the positive photoresist onto the wafer. Furthermore, since the spin-coated positive photoresist and the wetting layer formed based on the base photoresist can have good isotropic dissolution, the wetting layer can improve the flowability of the positive photoresist, facilitating the formation of a more uniform photoresist film during the subsequent second spin-coating process. This, in turn, helps reduce the distortion rate of the photolithographic pattern during transfer, improves the production yield, and reduces production costs. Understandably, the relatively low rotation speed of the aforementioned eighth wafer can prevent excessive centrifugal force on the positive photoresist, thereby preventing the positive photoresist from being directly thrown off the wafer to be coated during the spraying process, which is conducive to the smooth loading of the positive photoresist.

[0102] Furthermore, the wafer to be coated can be controlled to undergo a second spin coating rotation based on the second spin coating rotation parameters. This second spin coating rotation refers to the process of uniformly spreading the positive photoresist coated on the wetting layer. It is understood that the aforementioned second spin coating rotation parameters include, but are not limited to, the wafer rotation speed and rotation duration during the second spin coating rotation process. Thus, through the second spin coating rotation combined with the wetting effect of the wetting layer, a photoresist film of relatively uniform thickness can be formed on the surface of the wafer to be coated.

[0103] After the second photoresist rotation of the wafer to be coated, this method performs a cleaning operation on the wafer to be coated to remove the photoresist from the edges and back side of the wafer after the photoresist rotation, further reducing the defect rate of the product. It is understood that the cleaning process of the wafer to be coated may include controlling the wafer rotation at a wafer speed greater than or equal to 300 rpm and less than or equal to 500 rpm, and performing EBR (Edge Bead Removal) edge cleaning and BSR (Backside Rinse) cleaning on the wafer to be coated, with a cleaning duration greater than or equal to 2 minutes and less than or equal to 6 minutes.

[0104] After cleaning the wafer to be coated as described above, the wafer is baked according to the second baking temperature and the second baking time to ensure that the positive photoresist is tightly bonded to the wetting layer. The second baking temperature is 60°C to 120°C and the second baking time is 5 min to 30 min. Subsequently, the wafer to be coated can be cooled to form a photoresist film with high uniformity of thickness on the wafer.

[0105] In one feasible embodiment, the method controls the wafer to be coated to perform a second spin coating rotation according to the second spin coating rotation parameters, including:

[0106] Adjust the rotation speed of the wafer to be coated to the ninth wafer rotation speed, wherein the ninth wafer rotation speed is greater than or equal to 60 rpm and less than or equal to 100 rpm;

[0107] Based on the seventh rotation duration, the wafer to be coated is controlled to rotate at an accelerated speed from the ninth wafer rotation speed, wherein the seventh rotation duration is greater than or equal to 30s and less than or equal to 150s.

[0108] The rotation of the wafer to be coated is controlled according to the tenth wafer rotation speed and the eighth rotation duration. The tenth wafer rotation speed is greater than or equal to 800 rpm and less than or equal to 3500 rpm, and the eighth rotation duration is greater than or equal to 10 s and less than or equal to 20 s.

[0109] In this technical solution, based on the aforementioned second spin coating rotation execution method, the uniformity of the distribution of positive photoresist coated on the wetting layer can be improved. This, in conjunction with the aforementioned wetting layer, forms a positive photoresist layer with a certain thickness and relatively uniform thickness on the surface of the wafer to be coated. This facilitates subsequent operations, forming a photoresist film with high thickness uniformity on the surface of the wafer to be coated. Furthermore, based on the wetting effect provided by the aforementioned wetting layer, during the spin coating of positive photoresist, the wetting layer can be used to improve the flowability of positive photoresist at different locations on the wafer to be coated, which is beneficial to improving the thickness uniformity of the photoresist film on the wafer to be coated. This, in turn, helps to reduce the distortion rate of the pattern during the photolithography pattern transfer process, improves the production yield, and reduces production costs.

[0110] In one feasible embodiment, based on the seventh rotation duration, the method controls the wafer to be coated to rotate at an accelerated speed from the ninth wafer rotation speed, including:

[0111] Based on the above-mentioned ninth wafer rotation speed and fourth rotor duration, the above-mentioned wafer to be coated is controlled to rotate, and the above-mentioned fourth rotor duration is greater than or equal to 10s and less than or equal to 50s.

[0112] The rotation of the eleventh wafer is controlled according to the rotation speed of the eleventh wafer and the duration of the fifth rotor. The rotation speed of the eleventh wafer is greater than 100 rpm and less than or equal to 200 rpm, and the duration of the fifth rotor is greater than or equal to 10 s and less than or equal to 50 s.

[0113] The rotation of the wafer to be coated is controlled according to the rotation speed of the twelfth wafer and the duration of the sixth rotor. The rotation speed of the twelfth wafer is greater than 200 rpm and less than or equal to 400 rpm, and the duration of the sixth rotor is greater than or equal to 10 s and less than or equal to 50 s.

[0114] In this technical solution, when the wafer to be coated is accelerated to rotate at the ninth wafer speed and the seventh rotation duration, the method first controls the wafer to be coated to accelerate to rotate at the ninth wafer speed and the fourth rotator duration, where the fourth rotator duration is 10s to 50s. Then, the wafer to be coated is controlled to accelerate to rotate at the eleventh wafer speed and the fifth rotator duration, where the fifth wafer speed is 100rpm to 200rpm and the fifth rotator duration is 10s to 50s. Finally, the wafer to be coated is controlled to accelerate to rotate at the twelfth wafer speed and the sixth rotator duration. The twelfth wafer rotates at a speed of 200 rpm to 400 rpm, and the third rotor's duration is 10 s to 50 s. It is understood that as the positive photoresist continuously spreads along the surface of the wafer to be coated, the flow resistance of the positive photoresist on the wafer surface also increases. Therefore, based on the aforementioned control, the positive photoresist can be subjected to a progressively increasing centrifugal force during rotation, providing flow momentum for the positive photoresist. This facilitates more uniform spreading of the positive photoresist along the surface of the wafer to be coated, which is beneficial for forming a photoresist film of a certain thickness and uniform distribution on the surface of the wafer, in conjunction with the aforementioned wetting layer.

[0115] Furthermore, based on the aforementioned accelerated rotation control method for the wafer to be coated, combined with the aforementioned wetting layer setting, the fluidity of the positive photoresist can be further improved. Thus, even when the viscosity of the positive photoresist is high, such as above 2000 cp, it can still ensure that the positive photoresist spreads evenly along the surface of the wafer to be coated, which is beneficial to improving the uniformity of the photoresist film thickness of the wafer to be developed.

[0116] In one feasible embodiment, the diluent used in this method is EBR7030, and the positive photoresist is AZ40 or AZP4680.

[0117] In this technical solution, the aforementioned positive photoresist models AZ40 or AZP4680 have relatively good viscosity and flowability, making them suitable for fabricating photoresist films with high thickness requirements. By using EBR7030 as a diluent, the main chemical component of the aforementioned positive photoresist is an o-diazoquinone compound, which is soluble in ethylene glycol monomethyl ether. Since the aforementioned diluent contains ethylene glycol monomethyl ether, selecting EBR7030 as the diluent can improve the miscibility between the aforementioned positive photoresist and the aforementioned diluent, thereby improving the flowability of the aforementioned base photoresist.

[0118] It should be noted that the diluent and positive photoresist used in this embodiment are not unique. Those skilled in the art can use different diluents and positive photoresist models according to their habits and specific conditions, and all of them are within the scope of protection of this invention.

[0119] In one feasible embodiment, this method obtains the wafer to be coated, including:

[0120] Obtain the wafer body;

[0121] At a third preset temperature, an adhesive is applied to the wafer body to obtain a pre-prepared wafer;

[0122] The prepared wafer is kept at the third preset temperature for a first preset time to obtain the wafer to be coated.

[0123] It should be noted that the bonding agent mentioned above in this embodiment can be HMDS (Hexamethyldisilazane). The function of this bonding agent is to increase the adhesion between the base photoresist and the surface of the wafer body, so that the base photoresist is not easy to fall off. At the same time, the bonding agent is not unique, and those skilled in the art can use different bonding agents according to their habits and specific conditions.

[0124] The third preset temperature can be 120°C, and the first preset time can be between 30s and 50s. Allowing the prepared wafer to stand for a period of time in a high-temperature environment can help the adhesive to adhere better to the surface of the wafer body and prevent it from falling off. At the same time, it helps to evaporate the moisture of the prepared wafer and avoid the adhesive from undergoing a hydrolysis reaction.

[0125] In summary, this invention provides a wafer photoresist coating method, comprising: obtaining a wafer to be coated; preparing a base photoresist according to the film thickness requirement, wherein the base photoresist includes a diluent and a positive photoresist, the volume ratio of the diluent to the positive photoresist being greater than or equal to 3 and less than or equal to 10; spin-coating the base photoresist onto the wafer to be coated to form a wetting layer on the surface of the wafer to be coated; and spin-coating the positive photoresist onto the formed wetting layer to form a photoresist film on the surface of the wafer to be coated. The wafer photoresist coating method provided in this application adjusts the volume ratio of diluent to positive photoresist based on the required photoresist film thickness to prepare a base photoresist. The base photoresist is then spin-coated onto the desired wafer surface to form a wetting layer. Since the base photoresist contains positive photoresist, there is good miscibility between the base photoresist and the positive photoresist. Therefore, during the coating of the positive photoresist, the wetting layer can improve the flowability of the positive photoresist, allowing the positive photoresist to be more readily absorbed during the spin-coating process. The photoresist spreads more evenly to form a photoresist film with a more uniform thickness. Furthermore, the wetting layer formed based on the aforementioned base photoresist has good adhesion, reducing the requirements of the wetting layer on the substrate and making it easier to adhere to the wafer. This ensures the wetting effect during the coating of positive photoresist and facilitates the uniform spread of positive photoresist during spin coating to form a photoresist film with a more uniform thickness. This, in turn, helps to reduce the distortion rate of the pattern during the photolithography pattern transfer process, improves the production yield, and reduces production costs.

[0126] In this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. The term "two or more" includes two or more cases.

[0127] Obviously, those skilled in the art can make various modifications and variations to this specification without departing from its spirit and scope. Therefore, if such modifications and variations fall within the scope of the claims and their equivalents, this specification is also intended to include such modifications and variations.

Claims

1. A method for coating photoresist on a wafer, characterized in that, include: Obtain the wafer to be coated; According to the film thickness requirements, a base photoresist is prepared, which includes a diluent and a positive photoresist; The preparation of the substrate photoresist according to the film thickness requirements includes: Determine the target film thickness based on the required film thickness; Based on the target film thickness, the volume ratio of the diluent to the positive photoresist is determined. The volume ratio decreases as the target film thickness increases, and the volume ratio is greater than or equal to 3 and less than or equal to 10. The base photoresist is prepared according to the volume ratio; Spin-coating the substrate photoresist onto the wafer to be coated, so as to form a wetting layer on the surface of the wafer, includes: The base photoresist is spin-coated onto the wafer to be coated according to the first wafer rotation speed and the first rotation duration. The first wafer rotation speed is greater than or equal to 50 rpm and less than or equal to 200 rpm, and the first rotation duration is greater than or equal to 5 s and less than or equal to 10 s. The wafer to be coated is controlled to rotate in the first uniform coating rotation according to the first uniform coating rotation parameters. The wafer to be coated is baked according to a first baking temperature and a first baking time, wherein the first baking temperature is greater than or equal to 60°C and less than or equal to 120°C, and the first baking time is greater than or equal to 1 min and less than or equal to 5 min. The wafer to be coated is cooled according to a first cooling temperature and a first cooling time to form a wetting layer on the surface of the wafer to be coated. The first cooling temperature is greater than or equal to 22°C and less than or equal to 28°C, and the first cooling time is greater than or equal to 30s and less than or equal to 100s. The step of controlling the wafer to be coated to rotate according to the first spin coating rotation parameters includes: The wafer to be coated is controlled to rotate according to the second wafer rotation speed and the second rotation duration. The second wafer rotation speed is greater than or equal to 1000 rpm and less than or equal to 2000 rpm, and the second rotation duration is greater than or equal to 2s and less than or equal to 5s. Adjust the rotation speed of the wafer to be coated to a third wafer rotation speed, wherein the third wafer rotation speed is greater than or equal to 80 rpm and less than or equal to 200 rpm; Based on the third rotation duration, the wafer to be coated is controlled to rotate at an accelerated speed by the third wafer rotation speed, wherein the third rotation duration is greater than or equal to 15s and less than or equal to 30s. The rotation of the wafer to be coated is controlled according to the fourth wafer rotation speed and the fourth rotation duration. The fourth wafer rotation speed is greater than or equal to 1000 rpm and less than or equal to 4000 rpm, and the fourth rotation duration is greater than or equal to 10s and less than or equal to 20s. The positive photoresist is spin-coated onto the wetting layer to form a photoresist film on the surface of the wafer to be coated.

2. The wafer photoresist coating method according to claim 1, characterized in that, The step of controlling the wafer to be coated to rotate at an accelerated speed according to the third rotation duration includes: Based on the third wafer rotation speed and the first rotor duration, the wafer to be coated is controlled to rotate, wherein the first rotor duration is greater than or equal to 5s and less than or equal to 10s. The rotation of the wafer to be coated is controlled according to the fifth wafer rotation speed and the second rotor duration. The fifth wafer rotation speed is greater than 200 rpm and less than or equal to 400 rpm, and the second rotor duration is greater than or equal to 5s and less than or equal to 10s. The rotation of the wafer to be coated is controlled according to the rotation speed of the sixth wafer and the duration of the third rotor. The rotation speed of the sixth wafer is greater than 400 rpm and less than or equal to 600 rpm, and the duration of the third rotor is greater than or equal to 5s and less than or equal to 10s.

3. The wafer photoresist coating method according to claim 1, characterized in that, Spin-coating the positive photoresist onto the wetting layer to form a photoresist film on the surface of the wafer to be coated includes: The rotation of the wafer to be coated is controlled according to the seventh wafer rotation speed and the fifth rotation duration. The seventh wafer rotation speed is greater than 200 rpm and less than or equal to 600 rpm, and the fifth rotation duration is greater than or equal to 5s and less than or equal to 10s. The positive photoresist is spin-coated onto the wafer to be coated according to the eighth wafer rotation speed and the sixth rotation duration. The eighth wafer rotation speed is greater than or equal to 20 rpm and less than or equal to 50 rpm, and the sixth rotation duration is greater than or equal to 10 s and less than or equal to 50 s. The wafer to be coated is controlled to rotate in a second coating process according to the second coating rotation parameters. Clean the wafer to be coated; The wafer to be coated is baked according to a second baking temperature and a second baking time to form a photoresist film on the surface of the wafer to be coated. The second baking temperature is greater than or equal to 60°C and less than or equal to 120°C, and the second baking time is greater than or equal to 5 min and less than or equal to 30 min.

4. The wafer photoresist coating method according to claim 3, characterized in that, The step of controlling the wafer to be coated to rotate in a second coating rotation according to the second coating rotation parameters includes: Adjust the rotation speed of the wafer to be coated to the ninth wafer rotation speed, wherein the ninth wafer rotation speed is greater than or equal to 60 rpm and less than or equal to 100 rpm; Based on the seventh rotation duration, the wafer to be coated is controlled to rotate at an accelerated speed from the ninth wafer rotation speed, wherein the seventh rotation duration is greater than or equal to 30s and less than or equal to 150s. The rotation of the wafer to be coated is controlled according to the tenth wafer rotation speed and the eighth rotation duration. The tenth wafer rotation speed is greater than or equal to 800 rpm and less than or equal to 3500 rpm, and the eighth rotation duration is greater than or equal to 10 s and less than or equal to 20 s.

5. The wafer photoresist coating method according to claim 4, characterized in that, The step of controlling the wafer to be coated to rotate at an accelerated speed from the ninth wafer rotation speed according to the seventh rotation duration includes: The rotation of the wafer to be coated is controlled according to the ninth wafer rotation speed and the fourth rotor duration, wherein the fourth rotor duration is greater than or equal to 10s and less than or equal to 50s. The rotation of the wafer to be coated is controlled according to the eleventh wafer rotation speed and the fifth rotor duration. The eleventh wafer rotation speed is greater than 100 rpm and less than or equal to 200 rpm, and the fifth rotor duration is greater than or equal to 10 s and less than or equal to 50 s. The rotation of the wafer to be coated is controlled according to the rotation speed of the twelfth wafer and the duration of the sixth rotor. The rotation speed of the twelfth wafer is greater than 200 rpm and less than or equal to 400 rpm, and the duration of the sixth rotor is greater than or equal to 10 s and less than or equal to 50 s.

6. The wafer photoresist coating method according to any one of claims 1 to 5, characterized in that, The diluent is EBR7030; The positive photoresist is AZ40 or AZP4680.

7. The wafer photoresist coating method according to any one of claims 1 to 5, characterized in that, The process of obtaining the wafer to be coated includes: Obtain the wafer body; At a third preset temperature, an adhesive is applied to the wafer body to obtain a pre-prepared wafer; The pre-coated wafer is kept at the third preset temperature for a first preset time to obtain the wafer to be coated.

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