Thick photoresist photoetching process for deep silicon etching of micro device

Abstract

The invention relates to the technical field of MEMS product processing and manufacturing, in particular to a thick photoresist photoetching process for deep silicon etching of a micro device, which specifically comprises the following steps of: cleaning the surface of a substrate to remove pollutants; forming a photoresist layer with uniform thickness on the surface of the substrate; sequentially carrying out pre-baking, exposure, post-baking and development on the substrate; the temperature range is 70-95 DEG C, and the lasting time range is 60-90 min; and the substrate is etched and inspected, so that the photoresist layer is not easy to fall off in the deep silicon etching process, and the possibility that the etching quality is greatly influenced is reduced.

Description

Technical Field

[0001] The present application relates to the field of MEMS product processing and manufacturing technology, and in particular to a thick resist photolithography process for deep silicon etching of micro devices. Background Art

[0002] Deep silicon etching refers to the processing of high aspect ratio structures in MEMS products, generally referring to an etching depth greater than 60μm. Thick resist lithography, that is, the thickness of the photoresist to be coated during the lithography process reaches between 12μm and 18μm, allows the photoresist to maintain excellent structural stability during the deep silicon etching process, and is an advantageous technology suitable for deep silicon etching.

[0003] For example, a thick resist photolithography method for smoothing the side walls of a deep mesa structure with publication number CN119270591A sequentially performs the steps of coating, pre-baking, exposure, post-baking, developing, and hard film baking to form a photoresist layer of the desired pattern on the substrate surface for subsequent etching.

[0004] Regarding the above-mentioned related technologies, during the hard film baking process, the baking temperature must reach a minimum of 100°C, which will cause the adhesive surface to dry too quickly, which is not conducive to the volatilization of the solvent in the internal adhesive layer, reduces the adhesion to the substrate, reduces the etching resistance of the photoresist, and the photoresist is easy to fall off in the later stage of the etching process, affecting the etching quality of the substrate. Summary of the invention

[0005] In order to reduce the impact on substrate etching quality, the present application provides a thick resist photolithography process for deep silicon etching of micro devices.

[0006] The present application provides a thick resist photolithography process for deep silicon etching of micro devices using the following technical solution.

[0007] A thick-resist photolithography process for deep silicon etching of micro devices specifically comprises the following steps.

[0008] Step 1: Cleaning the substrate surface to remove contaminants; Step 2, forming a photoresist layer with uniform thickness on the surface of the substrate; Step 3, pre-baking, exposing, post-baking and developing the substrate in sequence; Step 4: performing hard film baking at a temperature range of 70 to 95° C. and a duration range of 60 to 90 minutes; Step 5: Etch and inspect the substrate.

[0009] By adopting the above technical solution, the temperature is controlled within 95°C to prevent the glue surface from drying too quickly and causing the solvent in the internal glue layer to volatilize. At the same time, the temperature is controlled above 70°C to allow the solvent in the photoresist to fully evaporate, reducing the possibility of pattern adhesion and colloid flexibility, which helps to control the quality of etching.

[0010] Optionally, in step 4, the film hardening baking temperature includes 70° C., and the film hardening baking duration is 70 to 90 minutes.

[0011] Optionally, in step 4, the film hardening baking temperature includes 80° C., and the film hardening baking duration is 60 to 80 minutes.

[0012] Optionally, in step 4, the film hardening baking temperature includes 95° C., and the film hardening baking duration is 60 to 70 minutes.

[0013] By adopting the above technical solution, different hardening baking durations are selected according to different hardening baking temperatures, so that the quality of the photoresist layer is not easily affected significantly, thereby reducing the impact on deep silicon etching.

[0014] Optionally, the duration of the hard film baking in step 4 is 70 minutes.

[0015] By adopting the above technical solution, the 70-minute hardening baking duration can take into account as many hardening baking temperatures as possible, so that even if the temperature fluctuates within a certain range during the hardening baking process, the quality of the photoresist layer is not easily greatly affected within the 70-minute hardening baking duration.

[0016] Optionally, the hard film baking temperature in step 4 is 80°C.

[0017] By adopting the above technical scheme, the hardening baking duration corresponding to the hardening baking temperature of 80°C is 60 to 80 minutes, and the hardening baking duration of 70 minutes, which is the maximum of the hardening baking temperature range, is the median of the hardening baking duration range corresponding to the hardening baking temperature of 80°C. Therefore, even if the hardening baking duration fluctuates within the range of 70±10 min, the quality of the photoresist layer is not easily greatly affected, so as to further improve the effectiveness of protecting the photoresist layer during deep silicon etching.

[0018] Optionally, in the step, after the substrate is cleaned, the substrate is pre-baked at a temperature of at least 100° C.

[0019] By adopting the above technical solution, it is ensured that there is no moisture in the air on the surface of the substrate after cleaning, so as to improve the adhesion between the photoresist and the substrate.

[0020] In summary, the present application includes at least the following beneficial effects.

[0021] The film baking temperature is controlled within 95°C to prevent the glue surface from drying too quickly and causing the solvent in the internal glue layer to volatilize. At the same time, the film baking temperature is controlled above 70°C to allow the solvent in the photoresist to fully evaporate, reducing the possibility of pattern adhesion and colloid flexibility, which helps to control the quality of etching. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a flowchart of the main steps of this application. DETAILED DESCRIPTION

[0023] The present application is further described in detail below in conjunction with the accompanying drawings.

[0024] The present application discloses a thick resist photolithography process for deep silicon etching of micro devices, referring to Figure 1 , specifically including the following steps.

[0025] Step 1: Clean the substrate surface with acetone and isopropanol to remove some organic impurities and particulate matter, and after cleaning, pre-bake the substrate at a temperature of at least 100° C. to remove water vapor in the air adsorbed on the substrate surface.

[0026] Step 2: Use spin coating to form a photoresist layer with uniform thickness on the surface of the substrate.

[0027] Step 3, pre-baking, exposing, post-baking and developing the substrate in sequence; Step 4: performing hard film baking at a temperature range of 70 to 95° C. and a duration range of 60 to 90 minutes; Step 5: Etch and inspect the substrate.

[0028] The thick resist photolithography process for deep silicon etching of micro devices of the present application is described below with specific embodiments and comparative examples.

[0029] Embodiment 1:

[0030] Step 1: Clean the substrate surface with acetone and then with isopropanol in two steps, and then bake the substrate at 120° C. for 1 to 3 minutes.

[0031] Step 2: Drop SU-8 glue onto the center of the substrate and spin coat it to obtain a photoresist layer.

[0032] Step 3: pre-baking at 95°C for 60 minutes.

[0033] Step 4: Expose the photoresist on the substrate with 365nm ultraviolet light.

[0034] Step 5: Post-baking at 90° C. for 10 min.

[0035] Step 6: Use PGMEA developer to develop for 8 minutes.

[0036] Step 7: Perform hardening baking at a temperature of 70° C. and a duration of 70 minutes.

[0037] Step 8: Etching is performed using oxygen plasma for 30 minutes.

[0038] Step 9: Observe under a microscope whether the photoresist on the substrate surface has fallen off.

[0039] Embodiment 2:

[0040] The difference from the first embodiment is that in step seven, the film hardening baking is performed at a temperature of 70° C. and a duration of 80 minutes.

[0041] Embodiment three:

[0042] The difference from the first embodiment is that in step seven, a hardening baking process is performed at a temperature of 70° C. and a duration of 90 minutes.

[0043] Embodiment 4:

[0044] The difference from the first embodiment is that in step seven, the film hardening baking is performed at a temperature of 80° C. and a duration of 60 minutes.

[0045] Embodiment five:

[0046] The difference from the first embodiment is that in step seven, the film hardening baking is performed at a temperature of 80° C. and a duration of 70 minutes.

[0047] Embodiment six:

[0048] The difference from the first embodiment is that in step seven, a hardening baking is performed at a temperature of 80° C. and a duration of 80 min.

[0049] Embodiment seven:

[0050] The difference from the first embodiment is that in step seven, a hardening baking process is performed at a temperature of 95° C. and a duration of 60 minutes.

[0051] Embodiment eight:

[0052] The difference from the first embodiment is that in step seven, a hardening baking process is performed at a temperature of 95° C. and a duration of 70 minutes.

[0053] Comparative Example 1: The difference from the first embodiment is that in step seven, the film hardening baking is performed at a temperature of 65° C. and a duration of 40 minutes.

[0054] Comparative Example 2: The difference from the first embodiment is that in step seven, the film hardening baking is performed at a temperature of 65° C. and a duration of 50 minutes.

[0055] Comparative Example 3: The difference from the first embodiment is that in step seven, the film hardening baking is performed at a temperature of 65° C. and a duration of 60 minutes.

[0056] Comparative Example 4: The difference from the first embodiment is that in step seven, the film hardening baking is performed at a temperature of 65° C. and a duration of 70 minutes.

[0057] Comparative Example 5: The difference from the first embodiment is that in step seven, the film hardening baking is performed at a temperature of 65° C. and a duration of 80 minutes.

[0058] Comparative Example 6: The difference from the first embodiment is that in step seven, the film hardening baking is performed at a temperature of 65° C. and a duration of 90 minutes.

[0059] Comparative Example 7: The difference from the first embodiment is that in step seven, a hardening baking is performed at a temperature of 65° C. and a duration of 100 min.

[0060] Comparative Example 8: The difference from the first embodiment is that in step seven, a hardening baking process is performed at a temperature of 70° C. and a duration of 40 minutes.

[0061] Comparative Example 9: The difference from the first embodiment is that in step seven, a hardening baking process is performed at a temperature of 70° C. and a duration of 50 minutes.

[0062] Comparative Example 10: The difference from the first embodiment is that in step seven, a hardening baking process is performed at a temperature of 70° C. and a duration of 60 minutes.

[0063] Comparative Example 11: The difference from the first embodiment is that in step seven, a hardening baking is performed at a temperature of 70° C. and a duration of 100 min.

[0064] Comparative Example 12: The difference from the first embodiment is that in step seven, the film hardening baking is performed at a temperature of 80° C. and a duration of 40 minutes.

[0065] Comparative Example 13: The difference from the first embodiment is that in step seven, a hardening baking process is performed at a temperature of 80° C. and a duration of 50 minutes.

[0066] Comparative Example 14: The difference from the first embodiment is that in step seven, the film hardening baking is performed at a temperature of 80° C. and a duration of 90 minutes.

[0067] Comparative Example 15: The difference from the first embodiment is that in step seven, a hardening baking is performed at a temperature of 80° C. and a duration of 100 min.

[0068] Comparative Example 16: The difference from the first embodiment is that in step seven, a hardening baking process is performed at a temperature of 95° C. and a duration of 40 minutes.

[0069] Comparative Example 17: The difference from the first embodiment is that in step seven, a hardening baking process is performed at a temperature of 95° C. and a duration of 50 minutes.

[0070] Comparative Example 18: The difference from the first embodiment is that in step seven, the film hardening baking is performed at a temperature of 95° C. and a duration of 80 minutes.

[0071] Comparative Example 19: The difference from the first embodiment is that in step seven, a hardening baking process is performed at a temperature of 95° C. and a duration of 90 minutes.

[0072] Comparative Example 20: The difference from the first embodiment is that in step seven, a hardening baking is performed at a temperature of 95° C. and a duration of 100 min.

[0073] Comparative Example 21: The difference from the first embodiment is that in step seven, a hardening baking is performed at a temperature of 100° C. and a duration of 40 minutes.

[0074] Comparative Example 22: The difference from the first embodiment is that in step seven, a hardening baking process is performed at a temperature of 100° C. and a duration of 50 minutes.

[0075] Comparative Example 23: The difference from the first embodiment is that in step seven, a hardening baking process is performed at a temperature of 100° C. and a duration of 60 minutes.

[0076] Comparative Example 24: The difference from the first embodiment is that in step seven, a hardening baking is performed at a temperature of 100° C. and a duration of 70 minutes.

[0077] Comparative Example 25: The difference from the first embodiment is that in step seven, a hardening baking process is performed at a temperature of 100° C. and a duration of 80 minutes.

[0078] Comparative Example 26: The difference from the first embodiment is that in step seven, a hardening baking process is performed at a temperature of 100° C. and a duration of 90 minutes.

[0079] Comparative Example 27: The difference from the first embodiment is that in step seven, a hardening baking is performed at a temperature of 100° C. and a duration of 100 min.

[0080] Whether the photoresist layer of each embodiment and comparative example falls off after etching is shown in the following two tables. Table 1 shows the results of the microscopic image of the photoresist layer under a microscope, and Table 2 shows the results as "NG" and "OK", where "NG" means that the corresponding photoresist layer falls off, and "OK" means that the photoresist layer and the substrate maintain good connectivity.

[0081] Table 1:

[0082] Table 2:

[0083] The implementation principle of a thick-resist photolithography process for deep silicon etching of micro-devices of the present application is as follows: It can be seen from the above embodiments and comparative examples that when different pre-baking temperatures are selected, the pre-baking duration is also different, and the higher the pre-baking temperature, the shorter the pre-baking duration. And the pre-baking temperature should not be too high, otherwise, even when the pre-baking duration is shortened, the surface of the photoresist layer dries too quickly and causes the colloid to crack. The pre-baking temperature should not be too low, otherwise, the pre-baking duration is too long, resulting in reduced adhesion between the photoresist and the substrate. Moreover, under the pre-baking conditions of 80°C and a duration of 70 minutes, even if there are certain fluctuations in the temperature and duration of the pre-baking, the adhesion between the obtained photoresist layer and the substrate is also good, so that the subsequent deep silicon etching is not prone to quality problems due to the detachment of the photoresist layer.

[0084] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A thick resist photolithography process for deep silicon etching of micro devices, characterized in that: The specific steps include: Step 1: Cleaning the substrate surface to remove contaminants; Step 2, forming a photoresist layer with uniform thickness on the surface of the substrate; Step 3, pre-baking, exposing, post-baking and developing the substrate in sequence; Step 4: performing hard film baking at a temperature range of 70 to 95° C. and a duration range of 60 to 90 minutes; Step 5: Etch and inspect the substrate.

2. A thick resist photolithography process for deep silicon etching of micro devices according to claim 1, characterized in that: In the step 4, the film hardening baking temperature includes 70° C., and the film hardening baking duration is 70 to 90 minutes.

3. A thick resist photolithography process for deep silicon etching of micro devices according to claim 1, characterized in that: In the step 4, the film hardening baking temperature includes 80° C., and the film hardening baking duration is 60 to 80 minutes.

4. The thick resist photolithography process for deep silicon etching of micro devices according to claim 1, characterized in that: In the step 4, the film hardening baking temperature includes 95° C., and the film hardening baking duration is 60 to 70 minutes.

5. A thick resist photolithography process for deep silicon etching of micro devices according to any one of claims 2 to 4, characterized in that: The duration of the hard film baking in step 4 is 70 minutes.

6. A thick resist photolithography process for deep silicon etching of micro devices according to claim 5, characterized in that: The baking temperature of the hard film in step 4 is 80°C.

7. A thick resist photolithography process for deep silicon etching of micro devices according to claim 1, characterized in that: In the step, after the substrate is cleaned, the substrate is pre-baked at a temperature of at least 100° C.

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