High-cleanliness fixing and separating method for miniature silicon-based MEMS device
By using a combination device of silicon-based MEMS devices, connection devices, thermolysis films and substrate films arranged in array during the fixing and separation of silicon-based MEMS devices, the problems of low cleanliness and complex operation in the prior art are solved, and an efficient device separation and accelerated separation process is achieved.
Patent Information
- Application Number
- CN202410979041.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-07-22
- Publication Date
- 2025-05-30
AI Technical Summary
The prior art has problems such as low cleanliness, complex operation, and difficulty in dealing with non-regular arrangement of devices during the fixing and separation of silicon-based MEMS devices.
A combination device is employed, including an array arranged silicon-based MEMS device, a connecting device, a pyrolysis film and a substrate backsheet. The connection structure is formed into a triangular prism shape by depositing the passivation layer on the silicon wafer, designing the pattern of the device area and the separation area, performing photolithography, removing the passivation layer and photoresist, transferring the silicon wafer to the substrate sheet using a pyrolysis film, and performing deep etching, and the connection structure is then pressed and heated to separate the device.
It realizes the clean fixation and separation of micro silicon-based MEMS devices, omits the complex arrangement and scribing steps of device structure, significantly speeds up the separation speed, and effectively avoids the problem of device shedding.
Smart Images
Figure CN120057842A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of MEMS processes, and specifically, to a high-cleanliness fixing and separating method for micro silicon-based MEMS devices. Background Art
[0002] In the development of micro-nano technology, MEMS has always been an important application direction. The MEMS technology process is complex, and there are various types of heterogeneous structure devices. For various device samples prepared on a silicon-based substrate, how to fix and separate them is also a difficult problem.
[0003] Currently, for such devices, physical methods such as diamond grinding wheels and lasers are mostly used for scribing. The sample pattern arrangement has a great influence on the complexity of the traditional scribing process. Especially for the separation requirements of non-regularly arranged devices, there is often still a large room for improvement. The conventional method of using plasma etching for scribing has certain requirements for the sample structure and device size, and there is pollution for deep-hole type devices. Therefore, it is of great significance to find a simple and highly clean MEMS device separation method. Summary of the Invention
[0004] To overcome the above-mentioned defects and deficiencies in the prior art, the present invention provides a high-cleanliness fixing and separating method for micro silicon-based MEMS devices.
[0005] The first object of the present invention is to provide a combined device.
[0006] The second object of the present invention is to provide a separating method for silicon-based MEMS devices.
[0007] Therefore, the present invention claims the following:
[0008] A combined device, the combined device includes silicon-based MEMS devices arranged in an array, a connecting device, a pyrolysis film and a base sheet. The pyrolysis film is attached to the base sheet, and the silicon-based MEMS devices arranged in an array are attached to the pyrolysis film;
[0009] Among the silicon-based MEMS devices arranged in an array, there are gaps between two adjacent silicon-based MEMS devices, and the diagonal silicon-based MEMS devices are connected by the connecting device;
[0010] The distance of the gap is 18 - 22 μm;
[0011] The length of the connecting device is 15 - 17 μm, the width is 16 - 18 μm, the connecting device is in the shape of a triangular prism, and one edge of the triangular prism is connected to the pyrolysis film, and the surface opposite to this edge is parallel to the pyrolysis film.
[0012] Preferably, the distance between the voids is 20 μm; the length of the connecting device is 16 μm and the width is 17 μm.
[0013] A method for separating a silicon-based MEMS device, comprising the following steps:
[0014] S1. Wash the silicon wafer, then deposit a passivation layer on the etched surface and the non-etched surface of the silicon wafer, and wash again after deposition to remove moisture;
[0015] S2. Design device regions arranged in an array on the mask plate, and there are patterns of regions to be etched for fabricating silicon-based MEMS devices in the device regions;
[0016] There is a preset distance between two adjacent device regions, and the preset distance is 18 - 22 μm;
[0017] Diagonal device regions are connected by a connecting structure, and the length of the pattern of the connecting structure is 15 - 17 μm and the width is 16 - 18 μm;
[0018] The regions other than the device regions and the connecting structure are separation regions;
[0019] S3. Coat a photoresist on the etched surface of the silicon wafer, and remove the photoresist in the separation region and the photoresist in the regions to be etched in the device regions by exposure and development;
[0020] S4. Etch and remove the passivation layer in the separation region, then remove all the remaining photoresist and clean;
[0021] S5. Paste a pyrolysis film on the substrate, and then attach the silicon wafer to the pyrolysis film;
[0022] S6. Perform deep etching on the regions to be etched in the device regions and the separation regions for 115 - 125 minutes, etch through the separation region, and etch the connecting structure into a triangular prism shape, with one edge of the triangular prism connected to the pyrolysis film and the surface opposite to this edge parallel to the pyrolysis film;
[0023] After the etching is completed, the diagonal device regions are connected by the connecting structure;
[0024] S7. Press the connecting structure and heat it to make the pyrolysis film lose its adhesiveness, separate the device regions, and obtain a silicon-based MEMS device.
[0025] Preferably, in step S1, the thickness of the passivation layer on the etched surface is 1 - 3 μm, and the thickness of the passivation layer on the non-etched surface is 0.2 - 0.9 μm.
[0026] More preferably, the thickness of the passivation layer on the etched surface is 2 μm, and the thickness of the passivation layer on the non-etched surface is 0.3 μm.
[0027] As an implementable manner, the material of the passivation layer is SiO 2 , SiN or Al metal.
[0028] Preferably, the material of the passivation layer is SiO 2 .
[0029] More preferably, the film stress value of the SiO 2 is less than 20 MPa.
[0030] As an implementable manner, the deposition method of the passivation layer is thermal growth, CVD, evaporation and / or sputtering.
[0031] Preferably, the deposition method of the passivation layer is plasma enhanced chemical vapor deposition.
[0032] Preferably, the removal of moisture is to spin-dry the moisture in an environment of 60°C.
[0033] Preferably, in step S2, the length of the pattern of the connection structure is 16 μm and the width is 17 μm.
[0034] Preferably, in step S2, the size of the device area is 2×2 mm to 10×40 mm.
[0035] Preferably, in step S3, the thickness of the photoresist is 2 to 4 μm.
[0036] Preferably, in step S3, the coating method of the photoresist is spin coating, and the rotation speed of the spin coating is 1000 to 5000 rpm.
[0037] Preferably, in step S3, the exposure dose is 300 to 600 mj / mm 2 , and the wavelength of the light is 404 to 406 nm.
[0038] Preferably, in step S5, the thickness of the pyrolysis film is 100 to 200 μm.
[0039] Preferably, in step S5, the removal of the photoresist is to use acetone for degluing.
[0040] Preferably, in step S5, the cleaning is to use isopropyl alcohol to clean the residual acetone, and then use water to clean the isopropyl alcohol.
[0041] Preferably, in step S5, the pyrolysis film is a double-sided adhesive film layer that is sticky at room temperature and loses its stickiness after being heated to 100 to 140°C.
[0042] More preferably, in step S5, the bonding strength of the pyrolysis film is greater than 400 gf / 25 mm.
[0043] Preferably, in step S6, the deep etching is performed by Bosch process etching.
[0044] More preferably, in step S6, the parameters of the Bosch process etching are specifically as follows: etching from top to bottom, cycling with growth-etching 1-etching 2 as a unit, and linearly increasing with the cycle; the power is 3000W, growth: pressure 35-40 mtorr, HF power 30W, time 1.5s; etching 1: pressure 20 mtorr, HF power 65-90W, time 1.2-1.9s; etching 2: pressure 60 mtorr, HF power 45-60W, time 3.4-3.6s;
[0045] The equipment for the Bosch process etching is an ICP deep etching system, with the model number of SPTS LPX-Rapier and the brand of KLA-Tencor Semiconductor.
[0046] Preferably, in step S6, the time of the deep etching is 120 min.
[0047] Compared with the prior art, the present invention has the following beneficial effects:
[0048] The present invention discloses a high-cleanliness fixing and separating method for a micro silicon-based MEMS device. The present invention first deposits a passivation layer on a silicon wafer, then designs the patterns of a device region, a separation region and a connection structure on a mask plate, and then through photolithography, removing the passivation layer in the separation region, degluing, cleaning, transferring the silicon wafer to a substrate by using a pyrolytic film, and then performing deep etching to etch through the separation region, so that the connection structure forms a triangular prism shape, and pressing the connection structure and heating can separate the independent devices. The present invention can omit the dicing step of the complex device structure arrangement on the silicon wafer, and since the deep etching of the device region and the separation region is carried out simultaneously, the separation speed of the complex device arrangement can be greatly accelerated.
[0049] In addition, the designed combination of the pyrolysis film and the connection structure can effectively solve the problem of the detachment of micro MEMS devices during the process. Due to the extremely small size of the devices themselves, after the scribing channels are etched, the devices are prone to detachment from the bottom adhesion layer. Therefore, the present invention strictly controls the length, width, and etching time of the separation area to ensure that the devices after etching are still adhered to the substrate wafer, and the devices can be completely separated by simply pressing on the connection structure. In addition, due to the "water cup" - shaped structure of the devices, the bottom of the "water cup" is composed of multiple layers of thin films, and the thin films themselves are not resistant to either acids or alkalis; moreover, the cleanliness requirement for the inner film layer at the bottom of the "water cup" is at the nanometer level, and any cleaning method will introduce impurity residues into the cup. Therefore, the formation of the "water cup" structure must be the last step. The present invention uses a passivation layer as a mask and a pyrolysis film as a carrier for pasting, which can avoid the "cleaning" step after the device is formed and prevent the subsequent cleaning from affecting the device film layer and deep - hole structure. Description of the Drawings
[0050] Figure 1 It is a flowchart of a high - cleanliness fixing and separating method for micro - silicon - based MEMS devices.
[0051] Figure 2 It is a schematic diagram of a high - cleanliness fixing and separating method for micro - silicon - based MEMS devices.
[0052] Figure 3 It is a graphical schematic diagram of the separation area and the connection structure in Example 1.
[0053] Figure 4 It is the actual etching effect diagram of the device in Example 1. Detailed Embodiments
[0054] The following specific embodiments are used to further illustrate the present invention, but the embodiments do not impose any form of limitation on the present invention. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in the technical field.
[0055] Unless otherwise specified, the reagents and materials used in the following embodiments are all commercially available.
[0056] Example 1 A high - cleanliness fixing and separating method for micro - silicon - based MEMS devices
[0057] I. Experimental Method
[0058] The high - cleanliness fixing and separating method for micro - silicon - based MEMS devices is shown in Figure 1 and Figure 2 .
[0059] 1. Deposition of the passivation layer
[0060] Select a silicon wafer with a diameter of 6 inches and a thickness of 350 μm. There are multiple layers of piezoelectric thin films on the surface of the silicon wafer (non-etching surface). Use plasma-enhanced chemical vapor deposition to deposit a passivation layer on the surface of the silicon wafer, and deposit 0.3 μm SiO 2 as the passivation layer on the etching surface (corresponding to the non-etching surface), and deposit 2 μm SiO 2 as the passivation layer. Before and after deposition, rinse the surface of the silicon wafer with water and spin-dry the water at 60 °C. The stress value of the SiO 2 film layer is controlled within 20 MPa.
[0061] 2. Design of the mask
[0062] The mask is designed with device regions arranged in an array, and there are patterns of regions to be etched in the device regions; there is a preset distance of 20 μm between two adjacent device regions; the diagonal device regions are connected by a connection structure, and the length of the connection structure pattern is 16 μm and the width is 17 μm. The region other than the device region and the connection structure is the separation region.
[0063] The size of the device region is 2 mm × 2 mm to 10 mm × 40 mm.
[0064] 3. Patterning of the silicon wafer
[0065] Use the mask in step 2 to perform photolithography on the silicon wafer obtained in step 1, and pattern the silicon wafer on the etching surface.
[0066] The photolithography process is as follows: Spin-coat the etching surface of the silicon wafer with 3 μm photoresist at a spin-coating speed of 1800 r / min. After heating at 120 °C for 1 min, use 350 mj / mm 2 of 405 nm wavelength light for exposure, then heat at 112 °C for 1 min, and develop to remove the photoresist in the separation region and the photoresist in the regions to be etched in the device regions to form the pattern to be etched.
[0067] 4. Removal of the passivation layer and photoresist
[0068] Use RIE etching to remove the passivation layer in the separation region, and then use acetone to remove the photoresist on the silicon wafer. After removing the photoresist, wash the remaining acetone with isopropyl alcohol, and then wash the remaining isopropyl alcohol with water.
[0069] 5. Transfer of the silicon wafer
[0070] Use a thermal release film that is viscous at room temperature and loses its viscosity after heating to 100 - 140 °C. The film layer thickness is 180 μm, and the bonding strength is greater than 400 gf / 25 mm.
[0071] Peel off the anti - sticking layer on one side of the thermal decomposition film, stick it on the base sheet, then peel off the anti - sticking layer on the other side, and bond the silicon wafer in step 4 onto it. The size of the base sheet is greater than or equal to that of the silicon wafer. The bonding surface can be fully bonded or partially suspended, and the actual bonded area of the bonding surface is not less than the area of the non - passivation layer region of the etching surface.
[0072] 6. Deep etching
[0073] Use the bosch process to deeply etch the areas to be etched and the separation area in the device area, and the etching time is 120 min.
[0074] The bosch process used in this embodiment is as follows: Use an ICP deep etching system (SPTS LPX - Rapier, KLA - Tencor) to etch from top to bottom, and cycle with growth - etch 1 - etch 2 as a unit, and linearly increase with the cycle. The power is 3000 W, growth: pressure 35 - 40 mtorr, HF power 30 W, time 1.5 s; etch 1: pressure 20 mtorr, HF power 65 - 90 W, time 1.2 - 1.9 s; etch 2: pressure 60 mtorr, HF power 45 - 60 W, time 3.4 - 3.6 s.
[0075] After etching is completed, the separation area is etched through, and the connection structure is etched into a triangular prism shape. One edge of the triangular prism is connected to the thermal decomposition film, and the surface opposite to this edge is parallel to the thermal decomposition film. The surface film layer in the separation area is naturally damaged after being etched through, and the etching area on the device just stops at the termination layer, ( Figure 4 ).
[0076] II. Experimental results
[0077] The etching result is normal. The silicon wafer after etching is still adhered to the base sheet and is connected by the connection structure. Pressing the connection structure can break the connection structure and separate the device (the force required to break the connection structure with a needle is about 200 - 1000 N). Heating to remove the sticking effect can completely take out the device.
[0078] Comparative example 1
[0079] I. Experimental method
[0080] 1. Design of the mask
[0081] A square area is preset on the mask. There is a device area in the square area, and there is a device area pattern in the device area. The device area is connected to the square area through a connection structure. The length of the connection structure pattern is 100 μm and the width is 12 μm. The area other than the device area and the connection structure is the separation area.
[0082] The device area is a circle with a diameter of 300 μm.
[0083] 2. Deposition of the passivation layer
[0084] Select a SOI wafer (a wafer with a stack of 10 μm silicon - 1 μm silicon oxide - 500 μm silicon). The silicon corresponding to the separation area is pre - removed from the front side (the 10 - μm silicon side). There are multiple layers of piezoelectric thin films on the surface of the SOI wafer (the non - etched side). Use plasma - enhanced chemical vapor deposition to deposit a passivation layer on the surface of the SOI wafer. Deposit 0.3 μm SiO 2 as the passivation layer on the 10 - μm silicon side of the SOI wafer, and deposit 2 μm SiO 2 as the passivation layer on the 500 - μm silicon side. Rinse the surface of the SOI wafer with water before and after deposition, and spin - dry the water at 60 °C. The stress value of the SiO 2 film layer is controlled within 20 MPa.
[0085] Step 3: Patterning of the SOI wafer, Step 4: Removal of the passivation layer and photoresist, and Step 5: Transfer of the SOI wafer are all carried out according to Example 1.
[0086] 6. Deep etching
[0087] Carry out deep etching on the separation area and the device area from the back side (i.e., with the 500 - μm silicon side facing up) according to the bosch process of Example 1. The etching time is 60 min, so that the connection structure is etched into a cuboid shape with a height of 10 μm.
[0088] II. Experimental results
[0089] When the etching reaches the front - side SiO 2 film, the SiO 2 film ruptures. At the same time of the rupture, the connection part breaks, and the sample bounces off.
[0090] Comparative Example 2
[0091] I. Experimental method
[0092] Step 1: Deposition of the passivation layer, Step 3: Patterning of the silicon wafer, Step 4: Removal of the passivation layer and photoresist, and Step 5: Transfer of the silicon wafer are all carried out according to Example 1.
[0093] In the design of the mask plate, there are device areas arranged in an array on the mask plate, and there are device area patterns in the device areas; there is a preset distance between two adjacent device areas, and the preset distance is 85 μm; the diagonal device areas are connected by a connection structure, and the length of the connection structure pattern is 60 μm and the width is 60 μm. The area other than the device area and the connection structure is the separation area.
[0094] The size of the device area is 2 mm × 2 mm to 10 mm × 40 mm.
[0095] In step 6 of deep etching, the separation area and the device area are deeply etched according to the Bosch process of Embodiment 1, and the etching time is 90 minutes, so that the cross-section of the connection structure is etched into a trapezoid, forming a quadrangular prism shape.
[0096] II. Experimental results
[0097] After the etching of the separation area is completed, the area to be etched of the device itself has not been completed yet. Therefore, the etching time is increased. As the deep etching proceeds to about 6 minutes (i.e., the total etching time is about 96 minutes), the smaller samples begin to separate (the connection structure is deformed but not broken), so that heat dissipation cannot be carried out, resulting in the inability to continue etching. After removing the adhesion, the device cannot be lifted up as a whole, and pressing cannot break the connection structure (it can be finally broken apart, but part of the device itself is broken and the connection structure is not broken). Thus, it can be seen that without adhesion, the fixation and easy separation of this shaped device cannot be achieved simultaneously.
[0098] Comparative Example 3
[0099] I. Experimental method
[0100] The deposition of the passivation layer in step 1, the patterning of the silicon wafer in step 3, the removal of the passivation layer and photoresist in step 4, and the transfer of the silicon wafer in step 5 are all carried out according to Embodiment 1.
[0101] In the design of the mask in step 2, an array of device areas is designed on the mask, and there are device area patterns in the device areas; there is a preset distance between two adjacent device areas, and the preset distance is 60 μm; the diagonal device areas are connected by a connection structure, and the length of the connection structure pattern is 42 μm and the width is 8 μm. The area other than the device area and the connection structure is the separation area.
[0102] The size of the device area is 2 mm × 2 mm to 10 mm × 40 mm.
[0103] In step 6 of deep etching, the separation area and the device area are deeply etched according to the Bosch process of Embodiment 1, and the etching time is 90 minutes, and the connection structure is etched into a triangular prism shape, and one edge of the triangular prism is connected to the pyrolysis film, and the surface opposite to this edge is parallel to the pyrolysis film.
[0104] II. Experimental results
[0105] After the etching is completed, the device itself has not been completed yet. The etching time is increased to about 10 minutes (i.e., the total etching time is about 100 minutes), and the smaller devices begin to separate (the connection structure is deformed but not broken), so that heat dissipation cannot be carried out, resulting in the inability to continue etching.
[0106] The above embodiments are preferred embodiments of the present invention. However, the embodiments of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.
Claims
1. A combined device, characterized in that: The combined device comprises silicon-based MEMS devices arranged in an array, a connecting device, a pyrolysis film and a substrate, wherein the pyrolysis film is attached to the substrate, and the silicon-based MEMS devices arranged in an array are attached to the pyrolysis film; In the silicon-based MEMS devices arranged in the array, there are gaps between any two adjacent silicon-based MEMS devices, and the diagonal silicon-based MEMS devices are connected by the connecting device; The distance of the gap is 18 to 22 μm; The length of the connecting device is 15-17 μm, the width is 16-18 μm, and the connecting device is in the shape of a triangular prism. One edge of the triangular prism is connected to the pyrolysis film, and the opposite surface of the edge is parallel to the pyrolysis film.
2. A method for separating a silicon-based MEMS device, characterized in that: The following steps are involved: S1. Wash the silicon wafer with water, then deposit a passivation layer on the etched surface and the non-etched surface of the silicon wafer, and wash it with water again after deposition to remove moisture; S2. Designing an array arrangement of device regions on a mask plate, wherein the device region has a pattern of a region to be etched for preparing a silicon-based MEMS device; There is a preset distance between two adjacent device regions, and the preset distance is 18 to 22 μm; The diagonal device regions are connected by a connection structure, and the length of the pattern of the connection structure is 15 to 17 μm and the width is 16 to 18 μm; The area other than the device area and the connection structure is the separation area; S3. Coating a photoresist on the etched surface of the silicon wafer, removing the photoresist in the separation region and the photoresist in the device region to be etched by exposure and development; S4. Etching to remove the passivation layer of the separation area, and then removing all the remaining photoresist, cleaning; S5. Paste a pyrolytic film on the substrate, and then attach the silicon wafer to the pyrolytic film; S6. The device region to be etched and the separation region are deeply etched for 115 to 125 minutes, and the separation region is etched through so that the connection structure is etched into a triangular prism shape, wherein one edge of the triangular prism is connected to the pyrolytic film, and the opposite surface of the edge is parallel to the pyrolytic film; After etching is completed, the diagonal device regions are connected by a connecting structure; S7. Pressing the connection structure and heating it to make the pyrolysis film lose its viscosity, separating the device area, and obtaining a silicon-based MEMS device.
3. The separation method according to claim 2, characterized in that In step S1, the thickness of the passivation layer on the etched surface is 1-3 μm, and the thickness of the passivation layer on the non-etched surface is 0.2-0.9 μm.
4. The separation method according to claim 2, characterized in that In step S2, the length of the pattern of the connection structure is 16 μm and the width is 17 μm.
5. The separation method according to claim 2, characterized in that In step S2, the size of the device area is 2×2 mm to 10×40 mm.
6. The separation method according to claim 2, characterized in that In step S3, the thickness of the photoresist is 2-4 μm.
7. The separation method according to claim 2, characterized in that In step S3, the exposure dose is 300-600 mj / mm 2 , the wavelength of the light is 404-406nm.
8. The separation method according to claim 2, characterized in that In step S5, the thickness of the pyrolysis film is 100-200 μm.
9. The separation method according to claim 2, characterized in that: In step S6, the deep etching is performed by Bosch etching.
10. The separation method according to claim 2, characterized in that: In step S6, the deep etching time is 120 minutes.