A method for removing SU8 photoresist in high aspect ratio deep trench structures

Abstract

The application relates to a method for removing SU8 photoresist in a high-depth-width-ratio deep groove structure, which comprises the following steps: SU8 photoresist pre-debinding treatment: placing a substrate in an N-methylpyrrolidone solution, performing water bath treatment, and then performing ultrasonic cleaning on the N-methylpyrrolidone solution with the substrate placed therein at room temperature, wherein the cleaning time is 0.5-4 h, and the cleaning power is 80-100 W; placing a rotor in the N-methylpyrrolidone solution, the rotor not being in contact with the substrate, and stirring on a magnetic stirrer for 0.5-4 h to remove the photoresist outside the gap and part of the photoresist in the gap; oxidizing and removing the SU8 photoresist residues in the gap between the electrodes of the substrate; and after the debinding, cleaning the gap between the electrodes of the substrate to remove the residual etching liquid in the gap between the electrodes of the substrate. The application reduces the influence of the SU8 photoresist on subsequent device manufacturing processes.

Description

Technical Field

[0001] This invention relates to a method for removing SU8 photoresist from a high aspect ratio deep trench structure, belonging to the field of optoelectronic device manufacturing technology. Background Technology

[0002] As optoelectronic devices become increasingly complex and diverse, their structures are also becoming more varied. High aspect ratio has become one of the key parameters in device structure. Several new optoelectronic devices already feature high aspect ratio structures, such as the high aspect ratio electrode structure of high-speed electro-optic modulators. Due to the high aspect ratio characteristic of these structures, SU8 photoresist is used for pattern design during fabrication, and subsequent processes require the removal of the SU8 photoresist. SU8 photoresist residue is easily left in high aspect ratio deep trench structures, and it is difficult to completely remove SU8 photoresist residue from the bottom of the trench structure. If the SU8 photoresist is not completely removed, subsequent processes cannot proceed, affecting the next stage of device fabrication and severely impacting device performance.

[0003] SU8 photoresist is corrosion resistant, has good mechanical properties, and is difficult to remove. Most SU8 photoresist processes do not require the removal of the photoresist layer. However, there is no good method for removing SU8 photoresist from deep trenches with high aspect ratios. Summary of the Invention

[0004] The technical problem solved by this invention is to overcome the shortcomings of the prior art and propose a method for removing SU8 photoresist from a high aspect ratio deep trench structure, so as to effectively remove residual SU8 photoresist from the high aspect ratio deep trench structure and reduce the impact of SU8 photoresist on subsequent device fabrication processes.

[0005] The solution of the present invention is:

[0006] A method for removing SU8 photoresist from a high aspect ratio deep trench structure, wherein the substrate has a deep trench structure, comprising:

[0007] SU8 photoresist pre-removal treatment: Place the substrate in an N-methylpyrrolidone solution and perform a water bath treatment. Then, ultrasonically clean the N-methylpyrrolidone solution containing the substrate at room temperature for 0.5–4 hours with a cleaning power of 80–100W. Place a rotor in the N-methylpyrrolidone solution, ensuring the rotor does not contact the substrate, and stir on a magnetic stirrer for 0.5–4 hours to remove the photoresist outside the gaps and some of the photoresist within the gaps.

[0008] Oxidative removal of SU8 adhesive residue from the substrate electrode gap: The substrate, after being stirred on a magnetic stirrer, is placed in an etching solution and subjected to a water bath treatment at a heating temperature of 60℃~75℃ for 0.5~1h; the etching solution containing the substrate is then ultrasonically cleaned at room temperature for 0.5~4h at a cleaning power of 80-100W; a rotor is placed in the etching solution without contacting the substrate, and the mixture is stirred on a magnetic stirrer for 0.5~4h to remove all the adhesive from the gap;

[0009] After removing the adhesive, clean the substrate electrode gap: Place the substrate after removing the adhesive into deionized water and perform water bath treatment at a heating temperature of 60℃~75℃ for 0.5~1h; perform ultrasonic cleaning on the deionized water containing the substrate at room temperature for 0.5~1h with a cleaning power of 80-100W; place a rotor in the deionized water without contacting the substrate and stir on a magnetic stirrer for 0.5~4h to remove residual corrosion liquid from the substrate electrode gap.

[0010] Furthermore, the corrosive solution consists of hydrogen peroxide and concentrated sulfuric acid, with a volume ratio of (100mL~500mL):(500mL~1000mL).

[0011] Furthermore, the swelling reaction between the N-methylpyrrolidone solution and the SU8 photoresist is accelerated by heating the solution to a temperature of 60℃~75℃ and bathing it for 3~5 hours.

[0012] Furthermore, the aspect ratio of the high aspect ratio deep trench and deep hole structure on the substrate is 1 to 5.

[0013] Furthermore, the SU8 adhesive filling thickness in the high aspect ratio deep trench and deep hole structure on the substrate is 20 micrometers to 40 micrometers.

[0014] A system for removing SU8 photoresist from a high aspect ratio deep trench structure, comprising:

[0015] SU8 photoresist pre-removal module: The substrate is placed in an N-methylpyrrolidone solution and subjected to a water bath treatment. Then, the N-methylpyrrolidone solution containing the substrate is ultrasonically cleaned at room temperature for 0.5–4 hours with a cleaning power of 80–100W. A rotor is placed in the N-methylpyrrolidone solution without contacting the substrate, and the solution is stirred on a magnetic stirrer for 0.5–4 hours to remove the photoresist outside the gaps and some of the photoresist within the gaps.

[0016] Module for removing SU8 adhesive residue from substrate electrode gaps: Place the substrate, after stirring on a magnetic stirrer, into an etching solution and perform a water bath treatment at a heating temperature of 60℃~75℃ for 0.5~1h; perform ultrasonic cleaning on the etching solution containing the substrate at room temperature for 0.5~4h at a cleaning power of 80-100W; place a rotor in the etching solution, ensuring the rotor does not contact the substrate, and stir on a magnetic stirrer for 0.5~4h to remove all adhesive residue from the gaps;

[0017] Substrate electrode gap cleaning module: The debonded substrate is placed in deionized water for water bath treatment at a temperature of 60℃~75℃ for 0.5~1h; the substrate-containing deionized water is ultrasonically cleaned at room temperature for 0.5~1h at a power of 80-100W; a rotor is placed in the deionized water without contacting the substrate, and the mixture is stirred on a magnetic stirrer for 0.5~4h to remove residual corrosion solution from the substrate electrode gap.

[0018] The advantages of this invention compared to the prior art are:

[0019] (1) The order of ultrasonic cleaning and magnetic stirring in this invention is ultrasonic cleaning followed by magnetic stirring. The purpose of this operation is to first perform ultrasonic cleaning, use the mechanical force of ultrasonic waves during the ultrasonic cleaning process to separate the SU8 adhesive from the substrate or electrode gap, and then use magnetic stirring to improve the fluidity of the solution, so as to immerse the solution into the gap between the SU8 adhesive and the electrode, thus ensuring the reaction of the SU8 adhesive and efficient processing of the SU8 adhesive.

[0020] (2) In the pre-removal treatment of SU8 photoresist, the substrate is placed in an N-methylpyrrolidone solution and heated to accelerate the reaction between SU8 photoresist and solution. Then, ultrasonic cleaning is used to separate the SU8 photoresist in the deep trenches on the substrate from the substrate. Ultrasonic cleaning makes it easier to separate SU8 photoresist from the substrate surface. Finally, magnetic stirring is used to send the solution into the gap between SU8 photoresist and substrate, which further swells the SU8 photoresist and facilitates the subsequent removal of SU8 photoresist residue. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the cross-section of the high aspect ratio deep trench and deep hole structure of the present invention filled with SU8 photoresist;

[0022] Figure 2 This is a schematic diagram of the SU8 photoresist pre-removal process of the present invention;

[0023] Figure 3 This is a schematic diagram of the process steps for oxidative removal of SU8 adhesive residue in the electrode gap according to the present invention.

[0024] Figure 4This is a schematic diagram of the electrode gap cleaning process steps of the present invention;

[0025] Figure 5 This refers to SU8 photoresist residue in the high aspect ratio deep trench structure of this invention;

[0026] Figure 6 This is a schematic diagram showing the complete removal of SU8 photoresist in the high aspect ratio deep trench structure of the present invention. Detailed Implementation

[0027] The present invention will be further described below with reference to the embodiments.

[0028] This embodiment describes a method for removing the resist from a substrate filled with 40-micrometer-thick SU8 adhesive in deep trenches and deep holes. The deep trenches are patterned using SU8 photolithography. Figure 1 As shown.

[0029] First, a substrate 100 is provided, and a titanium layer 110 with a thickness of 50 nm is grown on the substrate by magnetron sputtering. A gold layer 120 with a thickness of 50 nm is then grown on the titanium layer.

[0030] Secondly, a high aspect ratio deep trench pattern is fabricated on the aforementioned substrate using SU8 photolithography. The pattern layer is 130 μm thick, the resist thickness is 40 μm, and the pattern is a deep trench structure with an aspect ratio of 4. SU8 photolithography includes processes such as SU8 resist spin coating, baking, exposure, and development to transfer the pattern from the photomask to the film layer to be patterned. SU8 photolithography is common knowledge in the field and will not be described in detail here.

[0031] Next, a gold layer 140 with a thickness of 35 to 40 micrometers is grown within the SU8 adhesive pattern by electroplating.

[0032] In this embodiment, firstly, a titanium layer 110 and a gold layer 120 are grown by magnetron sputtering; then, a pattern is formed using SU8 photoresist photolithography; next, a gold layer 140 with a thickness of 35 micrometers to 40 micrometers is grown within the SU8 photoresist pattern by electroplating; then, the SU8 photoresist filling the middle of the gold layer is removed.

[0033] Step 1: Pre-removal treatment of SU8 photoresist;

[0034] like Figure 2 As shown, a substrate filled with SU8 photoresist in a high aspect ratio deep trench structure is provided. The SU8 photoresist pre-removal process includes a high-temperature water bath with a remover solution, ultrasonic cleaning, and a stirring process with the remover solution. The specific process requirements are as follows:

[0035] The pre-removal process for SU8 adhesive uses N-methylpyrrolidone (NMP) as the adhesive remover solution, and the soaking time in the adhesive remover solution is 4 hours. In the above adhesive removal process, a water bath treatment is performed, with a heating temperature of 75 degrees Celsius and a water bath time of 5 hours.

[0036] The substrate was placed in a beaker of NMP solution and then placed in an ultrasonic cleaner for ultrasonic cleaning. The cleaning time was 4 hours and the cleaning power was 80W.

[0037] Place the substrate in a beaker of NMP solution, place a rotor in the beaker, ensuring the rotor does not touch the substrate, and place the beaker containing the rotor and the substrate on a magnetic stirrer and stir for 4 hours.

[0038] Step 2: Cleaning SU8 adhesive residue from the substrate electrode gap;

[0039] like Figure 3 As shown, the following are the steps for removing SU8 residue from the substrate with a high aspect ratio structure filled with SU8 adhesive after step one:

[0040] The substrate was placed in a specific etching solution for 1 hour.

[0041] In the above-mentioned SU8 residue corrosion process, a water bath treatment is performed, and the heating temperature is 75 degrees Celsius.

[0042] The ratio (by volume) of the corrosive solution is hydrogen peroxide: concentrated sulfuric acid = 100 mL: 500 mL;

[0043] Optionally, the substrate and etching solution are placed in an ultrasonic cleaner for ultrasonic cleaning for 1 hour.

[0044] Optionally, the substrate is placed in a beaker of etching solution, a rotor is placed inside the beaker, the rotor must not touch the substrate, and the substrate with the rotor and the beaker of solution are placed on a magnetic stirrer and stirred for 1 hour.

[0045] Step 3: Substrate Electrode Gap Cleaning Process

[0046] like Figure 4 As shown, the above substrate was rinsed with deionized water and then placed in a deionized water bath for 1 hour.

[0047] The substrate after the above treatment was placed in a deionized water beaker and then placed in an ultrasonic machine for ultrasonic treatment for 1 hour at a power of 80W.

[0048] Place the substrate into a dehydrated beaker, place a rotor inside the beaker (the rotor must not touch the substrate), and place the substrate with the rotor and the beaker of solution into a magnetic stirrer and stir for 4 hours.

[0049] The key steps in removing SU8 photoresist from the high aspect ratio deep trench and deep hole structure in this embodiment are as follows: First, the large area of ​​SU8 photoresist on the surface is partially dissolved using the chemical solvent NMP. The heating temperature is selected as 75 degrees Celsius, slightly lower than the boiling point of NMP solution (81 degrees Celsius), which can accelerate the swelling reaction between SU8 photoresist and NMP solution. Then, ultrasonic treatment and magnetic stirring are used to allow NMP solution to enter the gap between SU8 photoresist and substrate, so that SU8 photoresist can be fully swollen and removed. An ultrasonic power of 80W is selected to ensure that the gap between SU8 photoresist and substrate is filled with NMP solution, while ensuring that ultrasonic treatment will not damage the electrode structure. Next, hydrogen peroxide and concentrated sulfuric acid are used to etch the SU8 photoresist residue. The treated substrate is placed in the etching solution, and then the substrate and etching solution are heated by a water bath. The heating temperature is set to 75 degrees Celsius to accelerate the etching of SU8 photoresist in the deep trench, while preventing the etching solution from being diluted by water vapor due to excessive temperature.

[0050] Finally, the substrate treated as described above was placed in deionized water, and then ultrasonic cleaning and magnetic stirring were performed sequentially to remove the remaining oxidized SU8 photoresist residue. A comparison was made before and after the removal process. Figure 5 , 6 As shown.

[0051] Step one of this invention utilizes the principle of swelling between NMP solution and SU8 photoresist to remove a large area of ​​surface SU8 photoresist. Simultaneously, heating is used to accelerate the reaction between the SU8 photoresist and the NMP solution. Then, ultrasonic cleaning is used to separate the SU8 photoresist within the deep trenches on the substrate from the substrate surface, making the separation easier. Finally, magnetic stirring is used to introduce NMP solution into the gap between the SU8 photoresist and the substrate, further swelling the SU8 photoresist and facilitating subsequent removal of SU8 photoresist residue.

[0052] Step 2: Building upon Step 1, the strong oxidizing properties of the etching solution are used to oxidize and remove the SU8 photoresist within the high aspect ratio structure. Heating can accelerate the oxidation rate of the SU8 photoresist. Simultaneously, the use of an ultrasonic cleaner and a magnetic stirrer ensures that the etching solution completely penetrates the gaps between the high aspect ratio electrode and the SU8 photoresist, guaranteeing the complete removal of the SU8 photoresist from the high aspect ratio electrode gaps.

[0053] Step 3, building upon Step 2, employs an ultrasonic cleaner and a magnetic stirrer to accelerate the removal of SU8 adhesive residue, thoroughly cleaning the oxidized SU8 adhesive residue and etching solution from the high aspect ratio electrode gaps. In the above steps, the order of ultrasonic cleaning followed by magnetic stirring is ultrasonic cleaning first, using the mechanical force of the ultrasound waves to separate the SU8 adhesive from the substrate or electrode gap. Then, magnetic stirring increases the fluidity of the solution, allowing it to permeate the gap between the SU8 adhesive and the electrode, ensuring the SU8 adhesive reacts and is processed efficiently. If the order of ultrasonic cleaning and magnetic stirring is reversed, this effect is not achieved.

[0054] It should be noted that the method for removing SU8 photoresist filling a deep trench structure with a high aspect ratio provided in this embodiment is based on an example of SU8 photoresist removal in a deep trench structure with an SU8 photoresist thickness of 40 micrometers and an aspect ratio of 4. However, the present invention is not limited to this. In addition to the above embodiment, the present invention can also be applied to the removal of SU8 photoresist of other thicknesses and in deep trenches and holes of other aspect ratio structures. Those skilled in the art can adjust the process parameters such as the NMP water bath and the water bath time and temperature of hydrogen peroxide and concentrated sulfuric acid etching solution according to the aspect ratio and SU8 photoresist thickness of the relevant structure to optimize the photoresist removal effect.

[0055] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solutions of the present invention by utilizing the methods and techniques disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the protection scope of the technical solutions of the present invention.

Claims

1. A method for removing SU8 photoresist from a high aspect ratio deep trench structure, wherein the substrate has a deep trench structure, characterized in that, include: SU8 photoresist pre-removal treatment: Place the substrate in an N-methylpyrrolidone solution and perform a water bath treatment. Then, ultrasonically clean the N-methylpyrrolidone solution containing the substrate at room temperature for 0.5–4 hours with a cleaning power of 80–100W. Place a rotor in the N-methylpyrrolidone solution, ensuring the rotor does not contact the substrate, and stir on a magnetic stirrer for 0.5–4 hours to remove the photoresist outside the gaps and some of the photoresist within the gaps. Oxidative removal of SU8 adhesive residue from the substrate electrode gap: The substrate, after being stirred on a magnetic stirrer, is placed in an etching solution and subjected to a water bath treatment at a heating temperature of 60℃~75℃ for 0.5~1h; the etching solution containing the substrate is then ultrasonically cleaned at room temperature for 0.5~4h at a cleaning power of 80-100W; a rotor is placed in the etching solution without contacting the substrate, and the mixture is stirred on a magnetic stirrer for 0.5~4h to remove all the adhesive from the gap; After removing the adhesive, clean the substrate electrode gap: Place the substrate after removing the adhesive into deionized water and perform water bath treatment at a heating temperature of 60℃~75℃ for 0.5~1h; perform ultrasonic cleaning on the deionized water containing the substrate at room temperature for 0.5~1h with a cleaning power of 80-100W; place a rotor in the deionized water without contacting the substrate and stir on a magnetic stirrer for 0.5~4h to remove residual corrosion liquid from the substrate electrode gap.

2. The method for removing SU8 photoresist from a high aspect ratio deep trench structure according to claim 1, characterized in that, The corrosive solution consists of hydrogen peroxide and concentrated sulfuric acid, with a volume ratio of (100mL~500mL):(500mL~1000mL).

3. The method for removing SU8 photoresist from a high aspect ratio deep trench structure according to claim 1, characterized in that, The swelling reaction between N-methylpyrrolidone solution and SU8 photoresist is accelerated by water bath treatment at a heating temperature of 60℃~75℃ and a water bath time of 3~5h.

4. The method for removing SU8 photoresist from a high aspect ratio deep trench structure according to claim 1, characterized in that, The aspect ratio of the high aspect ratio deep trench and deep hole structure on the substrate is 1 to 5.

5. The method for removing SU8 photoresist from a high aspect ratio deep trench structure according to claim 1, characterized in that, The high aspect ratio deep trench and deep hole structure on the substrate is filled with SU8 adhesive with a thickness of 20 micrometers to 40 micrometers.

6. A system for removing SU8 photoresist from a high aspect ratio deep trench structure, characterized in that, include: SU8 photoresist pre-removal module: The substrate is placed in an N-methylpyrrolidone solution and subjected to a water bath treatment. Then, the N-methylpyrrolidone solution containing the substrate is ultrasonically cleaned at room temperature for 0.5–4 hours with a cleaning power of 80–100W. A rotor is placed in the N-methylpyrrolidone solution without contacting the substrate, and the solution is stirred on a magnetic stirrer for 0.5–4 hours to remove the photoresist outside the gaps and some of the photoresist within the gaps. Module for removing SU8 adhesive residue from substrate electrode gaps: Place the substrate, after stirring on a magnetic stirrer, into an etching solution and perform a water bath treatment at a heating temperature of 60℃~75℃ for 0.5~1h; perform ultrasonic cleaning on the etching solution containing the substrate at room temperature for 0.5~4h at a cleaning power of 80-100W; place a rotor in the etching solution, ensuring the rotor does not contact the substrate, and stir on a magnetic stirrer for 0.5~4h to remove all adhesive residue from the gaps; Substrate electrode gap cleaning module: The debonded substrate is placed in deionized water for water bath treatment at a temperature of 60℃~75℃ for 0.5~1h; the substrate-containing deionized water is ultrasonically cleaned at room temperature for 0.5~1h at a power of 80-100W; a rotor is placed in the deionized water without contacting the substrate, and the mixture is stirred on a magnetic stirrer for 0.5~4h to remove residual corrosion solution from the substrate electrode gap.

7. The system for removing SU8 photoresist from a high aspect ratio deep trench structure according to claim 6, characterized in that, The corrosive solution consists of hydrogen peroxide and concentrated sulfuric acid, with a volume ratio of (100mL~500mL):(500mL~1000mL).

8. The system for removing SU8 photoresist from a high aspect ratio deep trench structure according to claim 7, characterized in that, The swelling reaction between N-methylpyrrolidone solution and SU8 photoresist is accelerated by water bath treatment at a heating temperature of 60℃~75℃ and a water bath time of 3~5h.

9. A system for removing SU8 photoresist from a high aspect ratio deep trench structure according to claim 8, characterized in that, The aspect ratio of the high aspect ratio deep trench and deep hole structure on the substrate is 1 to 5.

10. A system for removing SU8 photoresist from a high aspect ratio deep trench structure according to claim 9, characterized in that, The high aspect ratio deep trench and deep hole structure on the substrate is filled with SU8 adhesive with a thickness of 20 micrometers to 40 micrometers.

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