Optimizing dual-developed wafer processing

Abstract

The application provides an optimized double-developing wafer processing technology, and particularly relates to the technical field of semiconductor processing, and the optimized double-developing wafer processing technology comprises the following steps: S1. cleaning the wafer surface, and performing HMDS coating after the cleaning; S2. determining the film thickness according to a curve curve of the optimal rotating speed and the film thickness, determining the optimal soft baking temperature and the optimal soft baking time, and performing photoresist coating; S3. confirming the optimal pre-development time, performing pre-development treatment, destroying the molecular structure of the upper layer of the photoresist, and forming a preliminary pattern; S4. testing the optimal exposure condition, and performing exposure treatment on the photoresist after the pre-development treatment; and S5. after the exposure treatment, testing the optimal second developing condition, performing pre-development baking, then performing second developing treatment, and making the pattern into an inverted horn-shaped cross-sectional morphology, so that the working difficulty of the subsequent Lift-off process is reduced, and the product yield is improved.

Description

Technical Field

[0001] This invention relates to the field of semiconductor processing technology, and in particular to an optimized dual-development wafer processing process. Background Technology

[0002] Double-layer photoresist is a commonly used semiconductor process. It can achieve better resolution and is often used in lift-off processes. Lift-off photoresist generally has lower resolution and cannot create finer structures. However, with double-layer photoresist, the upper layer has a smaller opening and the lower layer has a larger opening, which allows for the creation of smaller patterns during deposition.

[0003] However, the double-layer photoresist process requires a non-photosensitive photoresist layer on the bottom, which requires a longer baking time, resulting in lower production efficiency and a relatively higher cost for the non-photosensitive photoresist. In addition, the bottom material may introduce additional thickness or refractive index changes, increasing the error in alignment mark recognition and affecting the coating accuracy. If the non-photosensitive bottom layer reacts chemically with the positive photoresist developer, it may generate insoluble byproducts, leading to residues or microbridge defects after development. Finally, particles or contaminants on the bottom surface will be removed during photoresist coating, increasing the density of photolithographic defects.

[0004] In view of this, the present invention proposes an optimized dual-development wafer processing technology that can replace double-layer adhesive. Summary of the Invention

[0005] To address the aforementioned problems, this invention proposes an optimized dual-development wafer processing technology.

[0006] This invention is achieved through the following technical solution:

[0007] This invention proposes an optimized dual-development wafer fabrication process, comprising the following steps:

[0008] S1. Clean the wafer surface, and then apply HMDS coating after cleaning;

[0009] S2. Determine the film thickness based on the curve of optimal rotation speed and film thickness, and determine the optimal soft baking temperature and optimal soft baking time, and then apply photoresist;

[0010] S3. Confirm the optimal pre-development time, perform pre-development treatment, and destroy the molecular structure of the upper layer of photoresist to form a preliminary pattern;

[0011] S4. Test the optimal exposure conditions and expose the photoresist after pre-development.

[0012] S5. After exposure, test the optimal secondary development conditions and bake before development, then perform secondary development to form an inverted horn-shaped cross-sectional morphology.

[0013] Furthermore, the steps in S2 for determining the optimal soft-bake temperature and optimal soft-bake time include:

[0014] The optimal baking temperature of 90℃ or 100℃ and the heating time of 60s were selected as intermediate values.

[0015] Keep the temperature constant, starting with a heating time of 60 seconds, and gradually increase it in increments of 5 seconds each, up to 180 seconds.

[0016] The optimal softening time is determined based on the degree of impact on CD after time changes and the morphology of FIB or TEM analysis.

[0017] With the control time unchanged, starting from a temperature of 90℃ or 100℃, the temperature is varied in increments of 2℃, increasing to 120℃ and decreasing to 80℃.

[0018] The optimal softening temperature was determined based on the degree of influence of temperature changes on CD and the morphology analyzed by FIB or TEM.

[0019] Furthermore, the confirmation of the optimal pre-development time in step S3 includes:

[0020] Using a pre-development time of 60s as the center value, the gradient changes were set in groups of 5s, increasing to 100s and decreasing to 40s.

[0021] The CDSEM measurement equipment was used to measure the line width changes after the pre-development time was changed to confirm the CD.

[0022] The optimal development time is determined based on FIB analysis or TEM analysis of the morphology.

[0023] Furthermore, the testing of optimal exposure conditions in step S5 includes:

[0024] Determine the optimal baking temperature before secondary development;

[0025] Adjust and determine the optimal baking time before secondary development;

[0026] Determine the optimal development time.

[0027] Furthermore, determining the optimal baking temperature before secondary development includes:

[0028] Keep the baking time constant at 60 seconds, with the temperature 110℃ as the center value, and change it in 2℃ increments, increasing to 130℃ and decreasing to 90℃.

[0029] The CDSEM measurement equipment was used to monitor the changes and morphology of CD.

[0030] The optimal baking temperature before secondary development is determined based on the changes and morphology.

[0031] Furthermore, adjusting and determining the optimal baking time before secondary development includes:

[0032] Keep the baking temperature constant at 110℃, starting with a time of 60s, and gradually increase the time to 180s in increments of 5s.

[0033] The CDSEM measurement equipment was used to monitor the changes and morphology of CD.

[0034] The optimal baking time before secondary development is determined based on the changes and morphology.

[0035] Furthermore, determining the optimal time for secondary development includes:

[0036] Keeping the optimal temperature and time for pre-baking constant, a stretching test was conducted on the baking time. With the development time of 60s as the center value, a gradient change was performed every 5s, increasing to 180s and decreasing to 40s.

[0037] The CDSEM measurement equipment was used to collect data on changes in the CD and its morphology.

[0038] The optimal secondary development time is determined based on the changes in condition and morphology.

[0039] The beneficial effects of this invention are:

[0040] The optimized dual-development wafer processing technology proposed in this invention can improve the reaction rate of the upper photoresist through pre-development, making the reaction rates of the upper and lower photoresists inconsistent. This results in an inverted horn shape with a larger top and smaller bottom during the subsequent secondary development, reducing the difficulty of the subsequent lift-off process and improving the product yield. Attached Figure Description

[0041] Figure 1 The relationship between photoresist thickness and rotation speed is shown in one embodiment of the optimized dual-development wafer fabrication process of the present invention.

[0042] Figure 2 The relationship between photoresist thickness and temperature is presented in one embodiment of the optimized dual-development wafer fabrication process of the present invention.

[0043] Figure 3 The relationship between photoresist thickness and rotation speed is shown in another embodiment of the optimized dual-development wafer processing technology of the present invention.

[0044] Figure 4The relationship between photoresist thickness and temperature is another embodiment of the optimized dual-development wafer fabrication process of the present invention;

[0045] Figure 5 This is a pre-developed structural diagram of the optimized dual-development wafer processing technology of the present invention;

[0046] Figure 6 This is a cross-sectional view of the inverted bull's-horn structure after secondary development in the optimized dual-development wafer processing technology of the present invention;

[0047] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0048] To more clearly and completely illustrate the technical solution of the present invention, the present invention will be further described below with reference to the accompanying drawings.

[0049] Please refer to Figures 1-2 This invention proposes an optimized dual-development wafer processing technology comprising the following steps:

[0050] S1. Clean the wafer surface, and then apply HMDS coating after cleaning;

[0051] S2. Determine the film thickness based on the curve of optimal rotation speed and film thickness, and determine the optimal soft baking temperature and optimal soft baking time, and then apply photoresist;

[0052] S3. Confirm the optimal pre-development time, perform pre-development treatment, and destroy the molecular structure of the upper layer of photoresist to form a preliminary pattern;

[0053] S4. Test the optimal exposure conditions and expose the photoresist after pre-development.

[0054] S5. After exposure, test the optimal secondary development conditions and bake before development, then perform secondary development to form an inverted horn-shaped cross-sectional morphology.

[0055] In specific embodiments, the wafer surface can be cleaned using ion washing or OK73 to reduce defects on the wafer surface that could lead to abnormal photoresist coating. HMDS adhesion promoter treatment increases the adhesion between the photoresist and the wafer. Pre-development aims to disrupt the molecular structure of the upper layer of photoresist, slowing down the reaction rate of the surface layer during exposure, while maintaining the reaction rates of the intermediate and bottom layers. Simultaneously, the intermediate layer reacts slowly with the developer, while the bottom layer reacts quickly, resulting in an inverted horn-shaped cross-section of the entire photoresist. Secondary development reveals the latent image after exposure, allowing the microscope to clearly distinguish between exposed and unexposed areas, thus revealing the desired pattern. This invention, through pre-development, improves the reaction rate of the upper photoresist layer, creating an inverted horn-shaped profile with a larger top and smaller bottom during subsequent secondary development. This reduces the difficulty of the subsequent lift-off process and improves product yield.

[0056] In one embodiment, by controlling the thickness of the pre-development, the chemical reaction in the exposure area can be made more concentrated, the contrast of the photo-acid reaction can be improved, and the pattern resolution can be improved. At the same time, the pre-development can weaken the interface reaction between the photoresist layer and the wafer, reducing the risk of photoresist residue during development after exposure.

[0057] In one embodiment, if only pre-development is performed without secondary development, the pattern will only leave a latent image on the photoresist and cannot be observed under a microscope. If only secondary development is performed without pre-development, the morphology of the photoresist cannot form an inverted horn shape, that is, a normal trapezoidal morphology instead of an inverted horn structure. Therefore, pre-development and secondary development are required.

[0058] In one embodiment, AZ5206 photoresist is used: the photolithography FEM matrix CD data is shown in the table below:

[0059] F(um) / E(mesc) 370 390 410 430 450 470 490 -0.6 915.6 819.91 953.45 964.71 1002.72 1034.69 1057.33 -0.4 916.37 953.52 948.45 992.51 1015.67 1038.91 1066.96 -0.2 929.03 961.02 979.22 999.33 1016.56 1047.21 1069.06 0 949.64 969.76 980.76 999.82 1029.43 1043.14 1080.35 0.2 950.78 967.24 986.43 1004.31 1031.44 1046.84 1076.41 0.4 951.89 955.51 973.66 998.89 1021.66 1046.61 1070.35 0.6 943.29 949.92 976.6 993.03 1022.19 1046.9 1068.75

[0060] In one embodiment, the photoresist used is AR80 photoresist: photolithography FEM matrix CD data.

[0061] F(um) / E(mesc) 290 310 330 350 370 390 410 -0.6 229.5 238.91 372.45 383.71 421.72 453.69 463.12 -0.4 335.37 372.52 367.45 411.51 434.67 457.91 485.96 -0.2 348.03 380.02 398.22 418.33 435.56 466.21 488.06 0 368.64 388.76 399.76 418.82 448.43 462.14 499.35 0.2 369.78 386.24 405.43 423.31 450.44 465.84 495.41 0.4 370.89 374.51 392.66 417.89 440.66 465.61 489.35 0.6 365.12 368.92 395.6 412.03 441.19 465.9 479.63

[0062] Furthermore, the steps in S2 for determining the optimal soft-bake temperature and optimal soft-bake time include:

[0063] The optimal baking temperature of 90℃ or 100℃ and the heating time of 60s were selected as intermediate values.

[0064] Keep the temperature constant, starting with a heating time of 60 seconds, and gradually increase it in increments of 5 seconds each, up to 180 seconds.

[0065] The optimal softening time is determined based on the degree of impact on CD after time changes and the morphology of FIB or TEM analysis.

[0066] With the control time unchanged, starting from a temperature of 90℃ or 100℃, the temperature is varied in increments of 2℃, increasing to 120℃ and decreasing to 80℃.

[0067] The optimal softening temperature was determined based on the degree of influence of temperature changes on CD and the morphology analyzed by FIB or TEM.

[0068] In a specific implementation, the optimal baking temperature of the photoresist can be determined through soft-bake testing, making the pre-development effect more obvious.

[0069] Furthermore, the confirmation of the optimal pre-development time in step S3 includes:

[0070] Using a pre-development time of 60s as the center value, the gradient changes were set in groups of 5s, increasing to 100s and decreasing to 40s.

[0071] The CDSEM measurement equipment was used to measure the line width changes after the pre-development time was changed to confirm the CD.

[0072] The optimal development time is determined based on FIB analysis or TEM analysis of the morphology.

[0073] In specific implementations, if the pre-development time is insufficient, the molecular structure of the photoresist surface layer will not be thoroughly affected, directly affecting the subsequent photoresist morphology and preventing the formation of an inverted horn shape, which directly affects the subsequent lift-off process. If the pre-development time is too long, it will directly lead to the difficulty in revealing the photolithographic open area during the subsequent secondary development, and some photoresist will remain, seriously affecting the pattern morphology of the photoresist and severely impacting the performance of the product.

[0074] Furthermore, the testing of optimal exposure conditions in step S5 includes:

[0075] Determine the optimal baking temperature before secondary development;

[0076] Adjust and determine the optimal baking time before secondary development;

[0077] Determine the optimal development time.

[0078] Furthermore, determining the optimal baking temperature before secondary development includes:

[0079] Keep the baking time constant at 60 seconds, with the temperature 110℃ as the center value, and change it in 2℃ increments, increasing to 130℃ and decreasing to 90℃.

[0080] The CDSEM measurement equipment was used to monitor the changes and morphology of CD.

[0081] The optimal baking temperature before secondary development is determined based on the changes and morphology.

[0082] Furthermore, adjusting and determining the optimal baking time before secondary development includes:

[0083] Keep the baking temperature constant at 110℃, starting with a time of 60s, and gradually increase the time to 180s in increments of 5s.

[0084] The CDSEM measurement equipment was used to monitor the changes and morphology of CD.

[0085] The optimal baking time before secondary development is determined based on the changes and morphology.

[0086] Furthermore, determining the optimal time for secondary development includes:

[0087] Keeping the optimal temperature and time for pre-baking constant, a stretching test was conducted on the baking time. With the development time of 60s as the center value, a gradient change was performed every 5s, increasing to 180s and decreasing to 40s.

[0088] The CDSEM measurement equipment was used to collect data on changes in the CD and its morphology.

[0089] The optimal secondary development time is determined based on the changes in condition and morphology.

[0090] In specific implementations, if the secondary development time is insufficient, the developed area will not be developed, resulting in some photoresist residue, which seriously affects the morphology of the photolithographic pattern and the product performance. If the secondary development time is too long, the developed area will be overdeveloped, and the sidewall morphology of the photoresist will gradually narrow. In severe cases, the morphology of the photoresist may collapse or be crushed during metal evaporation, directly affecting the product performance.

[0091] Of course, the present invention may have many other embodiments. Based on this embodiment, other embodiments obtained by those skilled in the art without any creative effort are all within the scope of protection of the present invention.

Claims

1. An optimized dual-development wafer processing technology, characterized in that, Includes the following steps: S1. Clean the wafer surface, and then apply HMDS coating after cleaning; S2. Determine the film thickness based on the curve of optimal rotation speed and film thickness, and determine the optimal soft baking temperature and optimal soft baking time, and then apply photoresist; S3. Confirm the optimal pre-development time, perform pre-development treatment, and destroy the molecular structure of the upper layer of photoresist to form a preliminary pattern; The optimal pre-development time confirmed in step S3 includes: Using a pre-development time of 60s as the center value, the gradient changes were set in groups of 5s, increasing to 100s and decreasing to 40s. The CDSEM measurement equipment was used to measure the line width changes after the pre-development time was changed to confirm the CD. The optimal development time is determined based on FIB or TEM analysis of the morphology. S4. Test the optimal exposure conditions and expose the photoresist after pre-development. S5. After exposure, test the optimal secondary development conditions and bake before development, then perform secondary development to form an inverted horn-shaped cross-sectional morphology.

2. The optimized dual-development wafer processing technology according to claim 1, characterized in that, The steps in step S2 that determine the optimal soft-bake temperature and optimal soft-bake time include: The optimal baking temperature of 90℃ or 100℃ and the heating time of 60s were selected as intermediate values. Keep the temperature constant, starting with a heating time of 60 seconds, and gradually increase it in increments of 5 seconds each, up to 180 seconds. The optimal softening time is determined based on the degree of impact on CD after time changes and the morphology of FIB or TEM analysis. With the control time unchanged, starting from a temperature of 90℃ or 100℃, the temperature is varied in increments of 2℃, increasing to 120℃ and decreasing to 80℃. The optimal softening temperature was determined based on the degree of influence of temperature changes on CD and the morphology analyzed by FIB or TEM.

3. The optimized dual-development wafer processing technology according to claim 1, characterized in that, The optimal exposure conditions tested in step S5 include: Determine the optimal baking temperature before secondary development; Adjust and determine the optimal baking time before secondary development; Determine the optimal development time.

4. The optimized dual-development wafer processing technology according to claim 3, characterized in that, Determining the optimal baking temperature before secondary development includes: Keep the baking time constant at 60 seconds, with the temperature 110℃ as the center value, and change it in 2℃ increments, increasing to 130℃ and decreasing to 90℃. The CDSEM measurement equipment was used to monitor the changes and morphology of CD. The optimal baking temperature before secondary development is determined based on the changes and morphology.

5. The optimized dual-development wafer processing technology according to claim 3, characterized in that, The process of adjusting and determining the optimal baking time before secondary development includes: Keep the baking temperature constant at 110℃, starting with a time of 60s, and gradually increase the time in increments of 5s to 180s. The CDSEM measurement equipment was used to monitor the changes and morphology of CD. The optimal baking time before secondary development is determined based on the changes and morphology.

6. The optimized dual-development wafer processing technology according to claim 3, characterized in that, Determining the optimal development time includes: Keeping the optimal temperature and time for pre-baking constant, a stretching test was conducted on the baking time. With the development time of 60s as the center value, a gradient change was performed every 5s, increasing to 180s and decreasing to 40s. The CDSEM measurement equipment was used to collect data on changes in the CD and its morphology. The optimal secondary development time is determined based on the changes in condition and morphology.

Images