Method for improving sacrificial layer residue in MEMS (Micro Electro Mechanical System) process with double-layer structure
By using a curing process of double-layer structure and polyimide resin in the MEMS process, combined with oxygen-containing plasma dry etching, the problem of floc residue after PI is solved, and bridge deck, bridge legs and VA are realized Cleaning in the hole improves the performance of MEMS products.
Patent Information
- Application Number
- CN202411291664.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-14
- Publication Date
- 2025-01-03
AI Technical Summary
In the MEMS process, floc residues exist in the bridge deck, bridge legs and VA hole after PI is released, which seriously affects the performance of the non-refrigeration detector.
Using a two-layer structure MEMS process, the bridge deck and bridge are removed by spin coating and curing with polyimide resin solution after both the first sacrificial layer and the second sacrificial layer are released, and the bridge is removed by spin coating and curing with oxygen-containing plasma dry etching. Flocs remain in the legs and VA holes. The specific steps include: spin-coating the first sacrificial layer, forming the bridge legs and the bridge deck, spin-coating the second sacrificial layer, curing and forming an umbrella surface, and then dry etching of oxygen-containing plasma. The curing process involves heating to 350°C and cooling to 50°C to remove floc residue.
Effectively remove floc residues in bridge decks, bridge legs and VA holes, improve product performance and avoid the impact of floc residues on performance.
Smart Images
Figure CN119240598A_ABST
Abstract
Description
Technical Field
[0001] The present disclosure relates to the field of semiconductors, and more particularly to a method for improving sacrificial layer residue in a MEMS process of a double-layer structure. Background Art
[0002] Photosensitive polyimide (PI) is a polymer material with imide groups on the main chain, which can withstand high temperatures of about 400°C and low temperatures of liquid helium (-269°C), and its glass transition temperature is above 140°C. Polyimide has good insulation, large elastic modulus, large linear expansion coefficient, can withstand large strain, and has good mechanical properties in a wide temperature range.
[0003] Microelectromechanical systems (MEMS) are the product of the cross-integration of microelectronics technology with mechanics, optics and other fields. It is an extension and expansion based on IC process technology. Sacrificial layer technology, as one of the key technologies of MEMS, is a micro-machining technology that utilizes the difference in corrosion rates of different materials in the same etching solution or etching gas to selectively etch away the material between the structural pattern and the substrate (i.e., the sacrificial layer material) to release the structure and form a cavity membrane or other suspended structure.
[0004] In the PI release process, the oxygen plasma dry etching process is basically used. This process has a fast etching rate and is easy to control, and can effectively solve the adhesion phenomenon existing in the wet process. However, the MEMS structure is complex. For double-layer uncooled detectors, there are flocs remaining in the bridge surface, bridge legs, and VA holes (i.e., vias) after PI release, which seriously affects the performance of the uncooled detector. Figure 1 is a schematic diagram of a double-layer MEMS process, in which the first sacrificial layer and the second sacrificial layer are not released. Figure 2 yes Figure 1 Schematic diagram of a double-layer MEMS process, wherein the first sacrificial layer and the second sacrificial layer are both released. Figure 3 These are photos of the bridge legs, bridge deck and VA holes (i.e., through-holes, Via) after the first sacrificial layer and the second sacrificial layer were released, showing that there are floccules remaining after the release.
[0005] Therefore, a method is needed to remove the flocculent residues in the bridge deck, bridge legs and VA holes to improve product performance. Summary of the invention
[0006] In view of the problems existing in the background technology, an object of the present disclosure is to provide a method for improving the sacrificial layer residue in the MEMS process of a double-layer structure, which can remove the floc residue in the bridge deck, bridge legs, and VA holes after the first sacrificial layer and the second sacrificial layer of the double-layer MEMS are released, thereby avoiding the influence of the floc residue on product performance.
[0007] Therefore, a method for improving the sacrificial layer residue in a MEMS process of a double-layer structure is provided, and the MEMS process of the double-layer structure comprises the following steps: S1, providing a MEMS process wafer before a first sacrificial layer of a polyimide resin solution is spin-coated, and spin-coating the first sacrificial layer of a polyimide resin solution on the MEMS process wafer; S2, curing the first sacrificial layer; S3, forming bridge legs, a bridge surface, and a VA hole on the cured first sacrificial layer; S4, spin-coating a second sacrificial layer of a polyimide resin solution on the formed bridge legs, the bridge surface, and the VA hole, wherein the second sacrificial layer is connected to the first sacrificial layer at least through the gap between the bridge legs; S 5. The second sacrificial layer is cured; S6. An umbrella cover is formed on the cured second sacrificial layer; S7. The second sacrificial layer and the first sacrificial layer are released by dry etching with oxygen-containing plasma; wherein, in step S2 and step S5, the curing process includes the following sub-steps: Sa. Heating: The MEMS process wafer and the corresponding sacrificial layer are baked by hot air in an oven, and the temperature is increased from room temperature to 350°C at a rate of 5-8°C / min; Sb. The temperature is kept constant for 60 minutes; Sc. Cooling: The MEMS process wafer and the corresponding sacrificial layer are cooled by cold air in the same oven, and the wafer is taken out of the oven after cooling to 50°C.
[0008] The beneficial effects of the present disclosure are as follows: in the method for improving the sacrificial layer residue in the MEMS process of the double-layer structure according to the present disclosure, through the curing process conditions of the polyimide in steps S2 and S5, the floc residues in the bridge deck S, bridge legs A, and VA holes can be removed after the release process in step S6, thereby avoiding the influence of the floc residues on product performance. BRIEF DESCRIPTION OF THE DRAWINGS
[0009] Figure 1 Schematic diagram of a double-layer MEMS process, wherein both the first sacrificial layer and the second sacrificial layer are not released.
[0010] Figure 2 yes Figure 1 Schematic diagram of a MEMS process of a double-layer structure, wherein both the first sacrificial layer and the second sacrificial layer are released.
[0011] Figure 3 These are photos of the bridge legs, bridge deck and VA holes (i.e., through-holes, Via) after the first sacrificial layer and the second sacrificial layer were released, showing that there are floccules remaining after the release.
[0012] Figure 4 It is a schematic diagram of a MEMS process sheet before the first sacrificial layer is set.
[0013] Figure 5 Schematic diagram of a MEMS process wafer with a first sacrificial layer already set.
[0014] Figures 5 to 13is a schematic diagram of a process of forming a bridge leg, a bridge surface, and a VA hole on the cured first sacrificial layer in step S3;
[0015] Figures 14 to 17 is a schematic diagram of a process of forming an umbrella surface on the cured second sacrificial layer in step S6;
[0016] Fig.18 A double-layer MEMS formed after releasing the second sacrificial layer and the first sacrificial layer in step S7;
[0017] Fig.19 These are photos of the VA holes, bridge legs, and bridge deck at the edge and center of the MEMS device of Example 1.
[0018] Fig. 20 These are photos of the VA holes, bridge legs, and bridge deck at the edge and center of the MEMS device of Example 2.
[0019] Fig.21 These are photos of the VA holes, bridge legs and bridge surface at the edge and center of the MEMS device of Comparative Example 1.
[0020] Fig. 22 These are photos of the VA holes, bridge legs and bridge surface at the edge and center of the MEMS device of Comparative Example 2.
[0021] The reference numerals are described as follows:
[0022] 1 substrate 10 second sacrificial layer
[0023] P connects to tungsten column H opening for support column
[0024] 2Metal reflective layer 11Support layer
[0025] 3 metal protection dielectric layer 12 metal layer
[0026] 4First sacrificial layer 13Covering layer
[0027] 41 Bridge pier openings 14 through holes
[0028] 5 Support layer S bridge deck
[0029] 6Thermosensitive layer S1Thermosensitive part
[0030] 7 Isolation layer S2 electrical connection part
[0031] 71 connection slot A bridge leg
[0032] 8-electrode connection layer U umbrella
[0033] 9Passivation layer C support column DETAILED DESCRIPTION
[0034] It will be understood that the disclosed embodiments are merely examples of the present disclosure, which may be implemented in various forms, and therefore, the specific details disclosed herein should not be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one of ordinary skill in the art to implement the present disclosure in various ways.
[0035] [Method to improve the sacrificial layer residue in the MEMS process of double-layer structure]
[0036] Reference Figures 4 to 18 The present disclosure provides a method for improving the sacrificial layer residue in a double-layer MEMS process. The double-layer MEMS process comprises the following steps:
[0037] S1, providing a MEMS process sheet before the first sacrificial layer 4 of the polyimide resin solution is spin-coated, such as Figure 4 As shown, a first sacrificial layer 4 of a polyimide resin solution is spin-coated on a MEMS process wafer, referring to Figure 5 ;
[0038] S2, the first sacrificial layer 4 is cured, see Figure 5 ;
[0039] S3, forming bridge legs A, bridge surface S, and VA holes on the cured first sacrificial layer 4, such as Figures 6 to 13 As shown;
[0040] S4, spin-coating a second sacrificial layer 10 of polyimide resin solution on the formed bridge leg A, bridge surface S, and VA hole, and the second sacrificial layer 10 is connected to the first sacrificial layer 4 at least through the gap of the bridge leg A, such as Fig.14 As shown;
[0041] S5, the second sacrificial layer 10 is cured, see Fig.14 ;
[0042] S6, forming an umbrella surface U on the cured second sacrificial layer 10, such as Figures 15 to 17 As shown;
[0043] S7, oxygen-containing plasma dry etching releases the second sacrificial layer 10 and the first sacrificial layer 4, such as Fig.18 As shown;
[0044] Wherein, in step S2 and step S5, the curing process includes the following sub-steps:
[0045] Sa, heating, using an oven to bake the MEMS process wafer and the corresponding sacrificial layer with hot air, heating from room temperature to 350°C at 5-8°C / min;
[0046] Sb, constant temperature for 60 min;
[0047] Sc, cooling, using the same oven to cool the MEMS process wafer and the corresponding sacrificial layer with cold air, and taking them out of the oven after cooling to 50°C.
[0048] In the method for improving the sacrificial layer residue in the MEMS process of the double-layer structure according to the present disclosure, through the curing process conditions of the polyimide in steps S2 and S5, the floc residues in the bridge deck S, bridge legs A, and VA holes can be removed after the release process in step S6, thereby avoiding the influence of the floc residues on product performance.
[0049] In one example, in step S1 and step S4, the solvent of the polyimide resin solution is 1-methyl-2-pyrrolidone, which accounts for 85-90% of the total polyimide resin solution by mass. Specifically, the polyimide solution is PI2610, and the viscosity of the polyimide solution is 3000CP.
[0050] In one example, in step S1 and step S4 , the polyimide resin solution is spin-coated by first spin-coating and baking the adhesion promoter solution and then spin-coating the polyimide resin solution.
[0051] Specifically, the first spin coating and baking of the adhesion promoter solution includes the following steps: Si, directly spraying the adhesion promoter solution on the MEMS process wafer so that the adhesion promoter solution completely covers the MEMS process wafer.
[0052] In one example, step Si includes sub-steps:
[0053] Si1, spraying the viscosity enhancer solution when the MEMS process wafer is in a static state;
[0054] Si2, spraying the viscosity enhancer solution and then letting it stand;
[0055] Si3, after the static thickener solution stops flowing, the MEMS process sheet is rotated slowly so that the thickener solution covers the entire surface;
[0056] Si4, after the sub-step Si3 is completed, the MEMS process sheet is rotated at high speed for spin drying.
[0057] For example, in sub-step Si1, the viscosity enhancer is VM652, the solvent is 1-methoxy-2-propanol, and the 1-methoxy-2-propanol accounts for 60% of the total mass of the viscosity enhancer solution. For example, in sub-step Si1, the viscosity enhancer solution is sprayed at a speed of 0.5-1 mL / s for 2-3 seconds; in sub-step Si2, it is left to stand for 8-25 seconds; in sub-step Si3, the MEMS process sheet is rotated at 500-1300 rpm, and in sub-step Si4, the MEMS process sheet is dried at 1500-2500 rpm.
[0058] Specifically, the post-spin coating of the polyimide resin solution includes the following sub-steps:
[0059] SI, when the MEMS process wafer is in a static state, spray polyimide on the adhesion promoter layer
[0060] Solution;
[0061] SII, spraying polyimide solution and then letting it stand;
[0062] SIII, after the static polyimide solution stops flowing, slowly rotate the MEMS process sheet
[0063] Rotate so that the polyimide solution covers the entire surface of the adhesion promoter layer;
[0064] SIV, after the sub-step SIII is completed, the MEMS process wafer is rotated at high speed to perform spin-spinning.
[0065] For example, in sub-step SI, the speed of spraying the polyimide solution is 0.5-1mL / s, and the amount of the polyimide solution sprayed is 6-8mL; in sub-step SII, stand for 10-15s; in sub-step SIII, the slow rotation speed is 300-1000rpm, and the time is 3-5s; in sub-step SIV, the high-speed rotation speed is 4000-5000rpm, and the time is 45-60s.
[0066] The spraying of the tackifier solution in step S1 and the spraying of the polyimide solution in sub-step S1 can share a coating chamber. For example, the machine of the coating chamber is a coating and developing machine Mark8.
[0067] Reference Figures 4 to 13 In one example, step S3 includes sub-steps:
[0068] S31, providing a MEMS process sheet after the first sacrificial layer 4 of step S2 is cured, such as Figure 5 As shown;
[0069] S32, etching the bridge pier openings 41 at both ends on the first sacrificial layer 4 until the metal reflective layer 2 on the substrate 1 of the MEMS process wafer is exposed, such as Figure 6 As shown;
[0070] S33, depositing a support layer 5 at the first sacrificial layer 4 and the openings 41 for the bridge piers at both ends, such as Figure 7 As shown;
[0071] S34, depositing a heat-sensitive layer 6 on the support layer 5, such as Figure 8 As shown;
[0072] S35, depositing an isolation layer 7 on the heat-sensitive layer 6 and the support layer 5 not covered by the heat-sensitive layer 6, such as Fig. 9 As shown;
[0073] S36, a plurality of connection grooves 71 are formed by etching on the isolation layer 7, the metal reflective layer 2 at the bridge pier openings 41 at both ends are exposed through the corresponding connection grooves 71, and a portion of the bridge pier openings 41 at both ends of the heat-sensitive layer 6 is exposed through the corresponding connection grooves 71, such as Fig.10 As shown;
[0074] S37, depositing and etching an electrode connection layer 8 on the isolation layer 7 and the plurality of connection grooves 71, the thermosensitive layer 6 is electrically connected to the substrate 1 (specifically, the readout circuit (not shown)) (via a plurality of connection tungsten pillars P) via the electrode connection layer 8 in and on the bridge pier openings 41 at both ends and the electrode connection layer 8 in and on the connection grooves 71 at the bridge pier openings 41 at both ends of the thermosensitive layer 6 respectively close to the two ends, as well as the metal reflective layer 2, as shown in FIG. Fig.11 As shown;
[0075] S38, depositing a passivation layer 9 on the outer surface of the electrode connection layer 8 and the isolation layer 7, and forming VA holes at the openings 41 of the bridge piers at both ends, such as Fig.12 As shown;
[0076] S39, the bridge legs A are etched between the openings 41 and the heat-sensitive layer 6 of the bridge piers at both ends, and the bridge deck S includes a heat-sensitive portion S1 and an electrical connection portion S2. The heat-sensitive portion S1 includes a support layer 5, a heat-sensitive layer 6, an isolation layer 7 and a passivation layer 9 from bottom to top, and the electrical connection portion S2 includes a support layer 5, an isolation layer 7, an electrode connection layer 8 and a passivation layer 9 from bottom to top. Fig.13 shown.
[0077] Specifically, in sub-step S32, the etching process of the first sacrificial layer 4 is: using a LAM2300star inductively coupled plasma reaction machine, the pressure of the chamber of the machine is 3.8-4.2mT, the temperature of the electrostatic chuck is 58-62°C, the source power is 950-1050W, the bias power is 285-315W, the He flow rate is 95-105sccm, the CF4 flow rate is 9.5-10.5sccm, the CHF3 flow rate is 66.5-73.5sccm, the O2 flow rate is 19-21sccm, and the etching time is set to 260-300s.
[0078] Specifically, in sub-step S33, the support layer 5 is silicon nitride, and the deposition process of the support layer 5 is as follows: the silicon nitride layer can be chemically vapor deposited using SiH4 and NH3 at 250°C and 2.2 mT.
[0079] Specifically, in sub-step S34, the thermal sensitive layer 6 is vanadium oxide VOx, and the deposition process of the thermal sensitive layer 6 is physical vapor deposition.
[0080] Specifically, in sub-step S35, the isolation layer 7 is silicon nitride, and the deposition process of the isolation layer 7 is: the isolation layer 7 is chemically vapor deposited by using SiH4 and NH3 at 250° C. and 2.2 mT.
[0081] Specifically, in sub-step S36, the etching process of the isolation layer 7 is: using a DPS metal etching machine, the pressure of the chamber of the machine is 8-15mT, the source power is 400-600W, the bias power is 50-100W, the flow rate of CF4 is 50-80sccm, the flow rate of CHF3 is 30-50sccm, and the etching time is set to 35-40s.
[0082] Specifically, in sub-step S37, the electrode connection layer 8 is titanium, the deposition process of the electrode connection layer 8 is physical vapor deposition, and the etching process of the electrode connection layer 8 is: using LAM2300 The star inductively coupled plasma reaction machine performs two-step etching; in the first step of etching, the pressure of the chamber of the machine is 100-150mT, the source power is 100-150W, the bias power is 50-70W, the flow rate of N2 is 50-60sccm, the flow rate of CF4 is 30-40sccm, the flow rate of O2 is 10-15sccm, and the etching time is set to 6s; in the second step of etching, the pressure of the chamber of the machine is 100-150mT, the source power is 300-350W, the bias power is 100-150W, the flow rate of N2 is 50-60sccm, the flow rate of CF4 is 20-40sccm, the flow rate of O2 is 10-15sccm, and the etching time is set to 50s.
[0083] Specifically, in sub-step S38, the passivation layer 9 is silicon nitride, and the deposition process of the passivation layer 9 is to perform chemical vapor deposition of the passivation layer 9 using SiH4 and NH3 at 250°C and 2.2 mT.
[0084] Specifically, in sub-step S39, the process of etching the bridge leg A is as follows: first, the LAM2300 star inductively coupled plasma reaction machine is used for etching, the pressure of the chamber of the machine is 8-12mT, the source power is 600-750W, the bias power is 200-350W, the flow rate of He is 200-300sccm, the flow rate of CF4 is 50-80sccm, the flow rate of Ar is 100-150sccm, and the etching time is set to 30s; then, the DPS metal etching machine is used for etching, the pressure of the chamber of the machine is 12-20mT, the source power is 500-850W, the bias power is 50-150W, the flow rate of BCl3 is 200-300sccm, and the etching time is set to 30s. The amount is 15-50sccm, the flow rate of Cl2 is 20-60sccm, the flow rate of Ar is 10-45sccm, and the etching time is set to 20s; finally, the LAM2300star inductively coupled plasma reaction machine is used for etching. The chamber pressure of the machine is 10-18mT, the source power is 600-900W, the bias power is 150-350W, the flow rate of He is 200-300sccm, the flow rate of CF4 is 50-90sccm, the flow rate of Ar is 100-180sccm, and the etching time is set to 24s.
[0085] Reference Figures 14 to 17 In one example, step S6 includes sub-steps:
[0086] S61, providing a MEMS process sheet after the second sacrificial layer 10 of step S5 is cured, such as Fig.14 As shown;
[0087] S62, etching the support column opening H in the middle on the second sacrificial layer 10 until the passivation layer 9 on the MEMS process wafer is exposed, such as Fig.15 As shown;
[0088] S63, depositing a support layer 11 at the second sacrificial layer 10 and the opening H for the support column, referring to Fig.16 ;
[0089] S64, depositing a metal layer 12 on the support layer 11, referring to Fig.16 ;
[0090] S65, depositing a capping layer 13 on the deposited metal layer 12, referring to Fig.16 ;
[0091] S66, etching the support layer 11, the metal layer 12 and the cover layer 13 to form a plurality of through holes 14 penetrating the support layer 11, the metal layer 12 and the cover layer 13 to expose the second sacrificial layer 10 on the MEMS process wafer, such as Fig.17 shown.
[0092] Specifically, in sub-step S62, the etching process of the second sacrificial layer 10 is: the etching process of the second sacrificial layer 10 is; using a LAM2300 star inductively coupled plasma reaction machine, the pressure of the chamber of the machine is 3.8-4.2mT, the temperature of the electrostatic chuck is 58-62°C, the source power is 950-1050W, the bias power is 285-315W, the He flow rate is 95-105sccm, the CF4 flow rate is 9.5-10.5sccm, the CHF3 flow rate is 66.5-73.5sccm, the O2 flow rate is 19-21sccm, and the etching time is set to 260-300s.
[0093] Specifically, in sub-step S63, the support layer 11 is silicon nitride, and the deposition process of the support layer 11 is as follows: the silicon nitride layer can be chemically vapor deposited using SiH4 and NH3 at 250°C and 2.2 mT.
[0094] Specifically, in sub-step S64 , the metal layer 12 is titanium, and the deposition process of the metal layer 12 is physical vapor deposition.
[0095] Specifically, in sub-step S65, the cover layer 13 is silicon nitride, and the deposition process of the cover layer 13 is as follows: the silicon nitride layer can be chemically vapor deposited by using SiH4 and NH3 at 250°C and 2.2 mT.
[0096] Specifically, in sub-step S66, the process of etching the support layer 11, the metal layer 12 and the cover layer 13 to form a plurality of through holes 14 is as follows: using LAM2300 The star inductively coupled plasma reaction machine performs two-step etching; in the first step of etching, the pressure of the chamber of the machine is 150-200mT, the source power is 150-200W, the bias power is 50-100W, the flow rate of N2 is 50-80sccm, the flow rate of CF4 is 40-75sccm, the flow rate of O2 is 10-15sccm, and the etching time is set to 4s; in the second step of etching, the pressure of the chamber of the machine is 100-180mT, the source power is 350-450W, the bias power is 150-200W, the flow rate of N2 is 50-80sccm, the flow rate of CF4 is 40-80sccm, the flow rate of O2 is 10-15sccm, and the etching time is set to 25s.
[0097] In step S7 , the polyimide layer may be released using a Gasonics device.
[0098] In one example, in step 7, the process parameters used for releasing the polyimide layer are: power of 800-1000W, flow rate of O2 of 800-1600sccm, flow rate of 4% H2 / N2 of 10-30sccm, pressure of 800-1200mT, temperature of 160-220°C, and time of 30-45min. Specifically, in step 7, the process parameters used for releasing the polyimide layer are: power of 800W, flow rate of O2 of 1000sccm, flow rate of 4% H2 / N2 of 20sccm, pressure of 1000mT, temperature of 200°C, and time of 35min.
[0099] [test]
[0100] Example 1
[0101] The MEMS process of the double-layer structure of Example 1 adopts the following steps:
[0102] S1, providing a MEMS process wafer before a first sacrificial layer 4 of a polyimide resin solution is spin-coated, and spin-coating a first sacrificial layer 4 of a polyimide resin solution on the MEMS process wafer;
[0103] S2, the first sacrificial layer 4 is cured;
[0104] S3, forming a bridge leg A, a bridge surface S, and a VA hole on the solidified first sacrificial layer 4;
[0105] S4, spin-coating a second sacrificial layer 10 of a polyimide resin solution on the formed bridge leg A, bridge surface S, and VA hole, wherein the second sacrificial layer 10 is connected to the first sacrificial layer 4 at least through the gap of the bridge leg A;
[0106] S5, the second sacrificial layer 10 is cured;
[0107] S6, forming an umbrella surface U on the solidified second sacrificial layer 10;
[0108] S7, oxygen-containing plasma dry etching to release the second sacrificial layer 10 and the first sacrificial layer 4;
[0109] Among them, in step S2 and step S5, the curing process adopts the following sub-steps:
[0110] Sa, heating, using an oven to bake the MEMS process wafer and the corresponding sacrificial layer with hot air, raising the temperature from room temperature to 350°C at 5°C / min;
[0111] Sb, constant temperature for 60 min;
[0112] Sc, cooling, using the same oven to cool the MEMS process wafer and the corresponding sacrificial layer with cold air, cooling to 50°C and taking it out of the oven;
[0113] Wherein, in step S1 and step S4, the polyimide resin solution is firstly spin-coated and baked with the tackifier solution and then spin-coated with the polyimide resin solution;
[0114] The tackifier solution is first spin-coated and baked using the steps: Si, the tackifier solution is directly sprayed on the MEMS process wafer so that the tackifier solution completely covers the MEMS process wafer;
[0115] Step Si adopts sub-steps: Si1, when the MEMS process chip is in a static state, spraying a tackifier solution, the tackifier is VM652, the solvent is 1-methoxy-2-propanol, based on the total mass of the tackifier solution, 1-methoxy-2-propanol accounts for 60%, and the tackifier solution is sprayed at a speed of 0.8 mL / s for 3 seconds; Si2, after spraying the tackifier solution, let it stand for 20 seconds; Si3, after the static tackifier solution stops flowing, the MEMS process chip is rotated slowly at 1000 rpm to allow the tackifier solution to cover the entire surface; Si4, after the sub-step Si3 is completed, the MEMS process chip is rotated at a high speed of 2000 rpm for spin drying;
[0116] The post-spin coating of the polyimide resin solution adopts the following sub-steps: SI, spraying the polyimide solution on the tackifier layer while the MEMS process wafer is in a stationary state, the speed of spraying the polyimide solution is 0.8 mL / s, and the amount of the polyimide solution sprayed is 7 mL; SII, standing for 15 seconds after spraying the polyimide solution; SIII, after the stationary polyimide solution stops flowing, the MEMS process wafer is rotated at a slow speed of 500 rpm for 4 seconds, so that the polyimide solution covers the entire surface of the tackifier layer; SIV, after the sub-step SIII is completed, the MEMS process wafer is rotated at a high speed of 4500 rpm for spin-spinning;
[0117] In step S1 and step S4, the polyimide solution is PI2610, and the viscosity of the polyimide solution is 3000CP;
[0118] The spraying of the tackifier solution in step Si and the spraying of the polyimide solution in sub-step SI share a coating chamber, and the machine of the coating chamber is a coating and developing machine Mark8;
[0119] Step S3 uses the following sub-steps:
[0120] S31, providing a MEMS process wafer on which the first sacrificial layer 4 of step S2 is cured;
[0121] S32, etching the bridge pier openings 41 at both ends on the first sacrificial layer 4 until the metal reflective layer 2 on the substrate 1 of the MEMS process wafer is exposed, wherein the etching process of the first sacrificial layer 4 is: using a LAM2300 star inductively coupled plasma reaction machine, the chamber pressure of the machine is 3.8mT, the temperature of the electrostatic chuck is 58°C, the source power is 950W, the bias power is 285W, the flow rate of He is 95sccm, the flow rate of CF4 is 9.5sccm, and the flow rate of CHF3 is
[0122] 66.5sccm, the flow rate of O2 is 19sccm, and the etching time is set to 260s;
[0123] S33, depositing a support layer 5 on the first sacrificial layer 4 and the openings 41 for bridge piers at both ends, wherein the support layer 5 is silicon nitride, and the deposition process of the support layer 5 is as follows: the silicon nitride layer can be chemically vapor deposited by using SiH4 and NH3 at 250°C and 2.2mT;
[0124] S34, depositing a thermal sensitive layer 6 on the support layer 5, wherein the thermal sensitive layer 6 is vanadium oxide VOx, and the deposition process of the thermal sensitive layer 6 is physical vapor deposition;
[0125] S35, depositing an isolation layer 7 on the thermosensitive layer 6 and the support layer 5 not covered by the thermosensitive layer 6, wherein the isolation layer 7 is silicon nitride, and the deposition process of the isolation layer 7 is as follows: chemical vapor deposition of the isolation layer 7 is performed using SiH4 and NH3 at 250° C. and 2.2 mT;
[0126] S36, a plurality of connection grooves 71 are formed by etching on the isolation layer 7, the metal reflective layer 2 at the bridge pier openings 41 at both ends are exposed through the corresponding connection grooves 71, and a part of the bridge pier openings 41 at both ends of the thermal layer 6 is exposed through the corresponding connection grooves 71. The etching process of the isolation layer 7 is as follows: using a DPS metal etching machine, the pressure of the chamber of the machine is 10mT, the source power is 500W, the bias power is 70W, the flow rate of CF4 is 60sccm, the flow rate of CHF3 is 40sccm, and the etching time is set to 40s;
[0127] S37, depositing and etching an electrode connection layer 8 on the isolation layer 7 and the plurality of connection grooves 71, the thermosensitive layer 6 is electrically connected to the substrate 1 via the electrode connection layer 8 in and on the bridge pier openings 41 at both ends and the electrode connection layer 8 in and on the connection grooves 71 at the bridge pier openings 41 at both ends of the thermosensitive layer 6 respectively close to the metal reflective layer 2, wherein the electrode connection layer 8 is titanium, the deposition process of the electrode connection layer 8 is physical vapor deposition, and the etching process of the electrode connection layer 8 is; using LAM2300 The star inductively coupled plasma reaction machine performs two-step etching; in the first step of etching, the pressure of the chamber of the machine is 150mT, the source power is 150W, the bias power is 70W, the flow rate of N2 is 60sccm, the flow rate of CF4 is 40sccm, the flow rate of O2 is 15sccm, and the etching time is set to 6s; in the second step of etching, the pressure of the chamber of the machine is 100mT, the source power is 300W, the bias power is 100W, the flow rate of N2 is 50sccm, the flow rate of CF4 is 20sccm, the flow rate of O2 is 10sccm, and the etching time is set to 50s;
[0128] S38, depositing a passivation layer 9 on the outer surface of the electrode connection layer 8 and the isolation layer 7, forming VA holes at the openings 41 of the bridge piers at both ends, wherein the passivation layer 9 is silicon nitride, and the deposition process of the passivation layer 9 is to chemically vapor deposit the passivation layer 9 using SiH4 and NH3 at 250°C and 2.2mT;
[0129] S39, the bridge legs A are etched between the openings 41 and the heat-sensitive layer 6 of the bridge piers at both ends. The bridge deck S includes a heat-sensitive portion S1 and an electrical connection portion S2. The heat-sensitive portion S1 includes a support layer 5, a heat-sensitive layer 6, an isolation layer 7 and a passivation layer 9 from bottom to top. The electrical connection portion S2 includes a support layer 5, an isolation layer 7, an electrode connection layer 8 and a passivation layer 9 from bottom to top. The process of etching the bridge legs A is as follows: first, LAM2300 is used. The etching was performed using a star inductively coupled plasma reaction machine, with a chamber pressure of 8mT, a source power of 750W, a bias power of 200W, a He flow rate of 200sccm, a CF4 flow rate of 50sccm, an Ar flow rate of 100sccm, and an etching time of 30s; the DPS metal etching machine was then used, with a chamber pressure of 20mT, a source power of 850W, a bias power of 150W, a BCl3 flow rate of 50sccm, a Cl2 flow rate of 60sccm, an Ar flow rate of 45sccm, and an etching time of 20s; and finally the LAM2300 was used. The etching is performed using a star inductively coupled plasma reaction machine, the chamber pressure of the machine is 10mT, the source power is 600W, the bias power is 150W, the flow rate of He is 200sccm, the flow rate of CF4 is 50sccm, the flow rate of Ar is 100sccm, and the etching time is set to 24s; step S6 adopts the following sub-steps:
[0130] S61, providing a MEMS process wafer on which the second sacrificial layer 10 of step S5 is cured;
[0131] S62, etching the support column opening H in the middle on the second sacrificial layer 10 until the passivation layer 9 on the MEMS process wafer is exposed, wherein the etching process of the second sacrificial layer 10 is: the etching process of the second sacrificial layer 10 is; using a LAM2300star inductively coupled plasma reaction machine, the pressure of the chamber of the machine is 4.2mT, the temperature of the electrostatic chuck is 62°C, the source power is 1050W, the bias power is 315W, the flow rate of He is 105sccm, the flow rate of CF4 is 10.5sccm, the flow rate of CHF3 is 73.5sccm, the flow rate of O2 is 21sccm, and the etching time is set to 300s;
[0132] S63, depositing a support layer 11 on the second sacrificial layer 10 and the opening H for the support column, wherein the support layer 11 is silicon nitride, and the deposition process of the support layer 11 is as follows: the silicon nitride layer can be chemically vapor deposited by using SiH4 and NH3 at 250° C. and 2.2 mT;
[0133] S64, depositing a metal layer 12 on the support layer 11, wherein the metal layer 12 is titanium and the deposition process of the metal layer 12 is physical vapor deposition;
[0134] S65, depositing a cover layer 13 on the deposited metal layer 12, the cover layer 13 is silicon nitride, and the deposition process of the cover layer 13 is: the silicon nitride layer can be chemically vapor deposited by using SiH4 and NH3 at 250° C. and 2.2 mT;
[0135] S66, etching the support layer 11, the metal layer 12 and the cover layer 13 to form a plurality of through holes 14 penetrating the support layer 11, the metal layer 12 and the cover layer 13 to expose the second sacrificial layer 10 on the MEMS process wafer. The process of etching the support layer 11, the metal layer 12 and the cover layer 13 to form the plurality of through holes 14 is: using a LAM2300 star inductively coupled plasma reaction machine to perform two-step etching;
[0136] In the first step of etching, the pressure of the chamber of the machine is 180mT, the source power is 175W, the bias power is 75W, the flow rate of N2 is 65sccm, the flow rate of CF4 is 60sccm, the flow rate of O2 is 12sccm, and the etching time is set to 4s; in the second step of etching, the pressure of the chamber of the machine is 140mT, the source power is 375W, the bias power is 175W, the flow rate of N2 is 65sccm, the flow rate of CF4 is 60sccm, the flow rate of O2 is 112sccm, and the etching time is set to 25s;
[0137] In step S7, the polyimide layer is released using Gasonics equipment, and the process parameters used for releasing the polyimide layer are: power of 800W, O2 flow rate of 1000sccm, 4% H2 / N2 flow rate of 20sccm, pressure of 1000mT, temperature of 200°C, and time of 35min.
[0138] Example 2
[0139] Except that the heating rate of step Sa in step S2 and step S5 is changed to 8° C. / min, the rest is the same as in Example 1.
[0140] Comparative Example 1
[0141] Except that the heating rate of step Sa in step S2 and step S5 is changed to 9° C. / min, the rest is the same as in Example 1.
[0142] Comparative Example 2
[0143] Except that the heating rate of step Sa in step S2 and step S5 is changed to 15° C. / min, the rest is the same as in Example 1.
[0144] from Fig.19 and Fig. 20 It can be seen that for Example 1-2, no flocs remain in the bridge deck S, bridge legs A, and VA holes after the release process in step S6.
[0145] from Fig.21 It can be seen that in Comparative Example 1, floccules were found to remain in the bridge deck S, bridge legs A, and VA holes after the release process in step S6.
[0146] from Fig. 22 It can be seen that in Comparative Example 2, significant floccules were found to remain in the bridge deck S, bridge legs A, and VA holes after the release process in step S6.
[0147] The above detailed description is used to describe multiple exemplary embodiments, but this document is not intended to be limited to the explicitly disclosed combinations. Therefore, unless otherwise stated, the various features disclosed herein can be combined together to form multiple additional combinations that are not shown for the sake of simplicity.
Claims
1. A method for improving the sacrificial layer residue in a double-layer MEMS process, characterized in that: The double-layer MEMS process includes the following steps: S1, providing a MEMS process wafer before a first sacrificial layer (4) of a polyimide resin solution is spin-coated, and spin-coating the first sacrificial layer (4) of a polyimide resin solution on the MEMS process wafer; S2, curing the first sacrificial layer (4); S3, forming a bridge leg (A), a bridge surface (S), and a VA hole on the cured first sacrificial layer (4); S4, spin coating a second sacrificial layer (10) of a polyimide resin solution on the formed bridge leg (A), bridge surface (S), and VA hole, wherein the second sacrificial layer (10) is connected to the first sacrificial layer (4) at least through the gap of the bridge leg (A); S5, curing the second sacrificial layer (10); S6, forming an umbrella surface (U) on the solidified second sacrificial layer (10); S7, oxygen-containing plasma dry etching to release the second sacrificial layer (10) and the first sacrificial layer (4); Wherein, in step S2 and step S5, the curing process includes the following sub-steps: Sa, heating, using an oven to bake the MEMS process wafer and the corresponding sacrificial layer with hot air, heating from room temperature to 350°C at 5-8°C / min; Sb, constant temperature for 60 min; Sc, cooling, using the same oven to cool the MEMS process wafer and the corresponding sacrificial layer with cold air, and taking them out of the oven after cooling to 50°C.
2. The method for improving the sacrificial layer residue in the MEMS process of the double-layer structure according to claim 1, characterized in that: In step S1 and step S4, the solvent of the polyimide resin solution is 1-methyl-2-pyrrolidone accounting for 85-90% by mass of the total polyimide resin solution.
3. The method for improving the sacrificial layer residue in the MEMS process of the double-layer structure according to claim 2, characterized in that: The polyimide solution is PI2610, and the viscosity of the polyimide solution is 3000CP.
4. The method for improving the sacrificial layer residue in the MEMS process of a double-layer structure according to claim 1, characterized in that: In step S1 and step S4 , the polyimide resin solution is spin-coated by first spin-coating and baking the tackifier solution and then spin-coating the polyimide resin solution.
5. The method for improving the sacrificial layer residue in the MEMS process of the double-layer structure according to claim 4, characterized in that: The first step of spin coating and baking the adhesion promoter solution includes the following steps: Si, spray the adhesion promoter solution directly on the MEMS process wafer so that the adhesion promoter solution completely covers the MEMS process wafer.
6. The method for improving the sacrificial layer residue in the MEMS process of the double-layer structure according to claim 5, characterized in that: Step S1 includes the sub-steps: Si1, spraying the viscosity enhancer solution when the MEMS process wafer is in a static state; Si2, spraying the viscosity enhancer solution and then letting it stand; Si3, after the static thickener solution stops flowing, the MEMS process sheet is rotated slowly. so that the tackifier solution covers the entire surface; Si4, after the sub-step Si3 is completed, the MEMS process sheet is rotated at high speed for spin drying.
7. The method for improving sacrificial layer residue in a double-layer MEMS process according to claim 6, characterized in that: In sub-step Si1, the viscosity enhancer is VM652, and the solvent is 1-methoxy-2-propanol. Based on the total mass of the viscosity enhancer solution, 1-methoxy-2-propanol accounts for 60%.
8. The method for improving sacrificial layer residue in a double-layer MEMS process according to claim 4, characterized in that: The post-spin coating of the polyimide resin solution comprises the following sub-steps: SI, when the MEMS process wafer is in a static state, a polyimide solution is sprayed on the adhesion promoter layer; SII, spraying polyimide solution and then letting it stand; SIII, after the stationary polyimide solution stops flowing, the MEMS process sheet is rotated slowly so that the polyimide solution covers the entire surface of the adhesion promoter layer; SIV, after the sub-step SIII is completed, the MEMS process wafer is rotated at high speed to perform spin-spinning.
9. The method for improving sacrificial layer residue in a double-layer MEMS process according to claim 1, characterized in that: Step S3 includes sub-steps: S31, providing a MEMS process wafer on which the first sacrificial layer (4) of step S2 is cured; S32, etching the bridge pier openings (41) at both ends on the first sacrificial layer (4) until the metal reflective layer (2) on the substrate (1) of the MEMS process wafer is exposed; S33, depositing a support layer (5) on the first sacrificial layer (4) and the openings (41) for bridge piers at both ends; S34, depositing a thermosensitive layer (6) on the support layer (5); S35, depositing an isolation layer (7) on the heat-sensitive layer (6) and the support layer (5) not covered by the heat-sensitive layer (6); S36, etching to form a plurality of connection grooves (71) on the isolation layer (7), the metal reflective layer (2) at the bridge pier openings (41) at both ends are exposed through the corresponding connection grooves (71), and a portion of the bridge pier openings (41) at both ends of the heat-sensitive layer (6) is exposed through the corresponding connection grooves (71); S37, depositing and etching an electrode connection layer (8) on the isolation layer (7) and at the plurality of connection grooves (71), the thermosensitive layer (6) passing through the electrode connection layer (8) in and on the bridge pier openings (41) at both ends and the bridge pier openings (41) at both ends of the thermosensitive layer (6) respectively close to each other. The electrode connection layer (8) in and on the connection groove (71) and the metal reflection layer (2) are electrically connected to the substrate (1); S38, depositing a passivation layer (9) on the electrode connection layer (8) and the isolation layer (7) on the outer surface, and forming VA holes at the openings (41) of the bridge piers at both ends; S39, the bridge legs (A) are etched between the openings (41) and the heat-sensitive layer (6) at the bridge piers at both ends. The bridge deck (S) includes a heat-sensitive part (S1) and an electrical connection part (S2). The heat-sensitive part S1 includes, from bottom to top, a support layer (5), a heat-sensitive layer (6), an isolation layer (7) and a passivation layer (9). The electrical connection part (S2) includes, from bottom to top, a support layer (5), an isolation layer (7), an electrode connection layer (8) and a passivation layer (9).
10. The method for improving sacrificial layer residue in a double-layer MEMS process according to claim 9, characterized in that: Step S6 includes the sub-steps of: S61, providing a MEMS process wafer on which the second sacrificial layer (10) of step S5 is cured; S62, etching a hole (H) for a support column located in the middle on the second sacrificial layer (10) until the passivation layer (9) on the MEMS process wafer is exposed; S63, depositing a support layer (11) on the second sacrificial layer (10) and the opening (H) for the support column; S64, depositing a metal layer (12) on the support layer (11); S65, depositing a covering layer (13) on the deposited metal layer (12); S66, etching the support layer (11), the metal layer (12) and the cover layer (13) to form a plurality of through holes (14) penetrating the support layer (11), the metal layer (12) and the cover layer (13) to expose the second sacrificial layer (10) on the MEMS process wafer.
11. The method for improving sacrificial layer residue in a double-layer MEMS process according to claim 1, characterized in that: In step 7, the process parameters for releasing the polyimide layer are: power 800-1000W, O2 flow rate 800-1600sccm, 4% H2 / N2 flow rate 10-30sccm, pressure 800-1200mT, temperature 160-220°C, and time 30-45min.