CN106800272A - A kind of MEMS wafer cutting and wafer scale release and method of testing - Google Patents

Abstract

The invention relates to a method for cutting, cleaning and releasing MEMS wafers, comprising the following steps: coating photoresist on the front of the wafer, thinning the back; bonding, bonding the back of the wafer and the front of the glass base with UV glue; cutting, Using step cutting, the two-step cutting is completed continuously; cleaning and drying the wafer; structure release, put the wafer and glass base into the glue removal equipment for structure release; debonding: use UV irradiation machine to reduce the distance between the wafer and the glass base The viscosity of the UV glue between the wafers; expand the wafer; use the chip pick-up equipment to remove the chip from the UV film and put it into the tray; split and expand the film; optical inspection machine packaging test; no need for two alignments, ensuring The accuracy of the two cutting positions enables wafer-level structure release and testing with high efficiency.

Description

A MEMS wafer dicing and wafer-level release and testing method

technical field

The invention designs a MEMS wafer cutting and wafer-level release and testing method, which belongs to micro-electromechanical system microfabrication and wafer cutting methods.

Background technique

Micro-Electro-Mechanical System (MEMS, Micro-Electro-Mechanical System) is a high-tech field based on microelectronic technology and microprocessing technology. MEMS technology can integrate mechanical components, drive components, electronic control systems, digital processing systems, etc. into an integral micro-unit. MEMS devices have many advantages such as tiny, intelligent, executable, integrable, good process compatibility, and low cost. The development of MEMS technology has opened up a new technical field and industry. Micro-sensors, micro-actuators, micro-components, micro-mechanical optical devices, vacuum microelectronic devices, power electronic devices, etc. made by MEMS technology are used in aviation, aerospace, automobiles, Biomedical, environmental monitoring, military, Internet of Things and other fields have very broad application prospects.

In the manufacturing process of MEMS devices, many complex three-dimensional or support structures use the sacrificial layer release process. That is, in the process of forming micromechanical structure cavities or movable microstructures, first deposit structural materials on the dielectric film, and then prepare various special structures required by photolithography and etching processes, and then prepare support layer structures (cavities or microstructure). Since the removed structural material only acts as a separation layer, it is called a sacrificial layer. Commonly used sacrificial layer materials include silicon oxide, polysilicon, polyimide, and the like. A variety of active microstructures can be produced by using the sacrificial layer, such as micro-bridges, cantilever beams, moving parts, and mass blocks. Therefore, after the MEMS device is fabricated, the release of the MEMS structure is a key process in the MEMS device manufacturing process.

MEMS wafers need to be diced after completing various previous manufacturing processes, the wafers are cut into individual chips, and then packaged and tested. Structural release can optionally be performed before or after cleavage. Since the chip in the wafer has a MEMS structure, there is a contradiction between the three in the order of cutting, cleaning and releasing. If the processing is not done properly, the MEMS chip will be damaged or completely scrapped.

To deal with the contradiction between MEMS cutting cleaning and structure release, the existing technical solutions mainly include:

1) Release the structure of the wafer first, and then perform laser cutting, which does not require wet cleaning; using invisible laser cutting, the equipment is expensive and the process is complicated, and the wafer needs to be thinned first. After cutting, it needs to be split by a splitter And expand the film, and the cutting line can not have graphics, especially with metal graphics, which will reflect laser energy. The dicing line is only required to be made of silicon, and the inclusion of silicon nitride or silicon dioxide will also affect light absorption. Stealth laser dicing has special requirements for the layout of the wafer dicing lanes. Designing the graphics of the dicing lanes separately will occupy the chip area and reduce the number of effective chips on the wafer.

2) Release the structure of the wafer first, punch holes and stick film to protect the MEMS structure of the wafer, and then perform back cutting; due to the film protection of the MEMS structure of the wafer, additional processes are required and the process is complicated, and the problem of back cutting is cost High, low operating efficiency, unstable yield rate, not suitable for chips with high proportion of MEMS

3) Protect the front of the wafer with glue first, then perform photolithography, use plasma cutting to cut, and then release; photolithography is required, and thinning is required before release, photolithography equipment, thinning equipment and Plasma cutting equipment is very expensive.

Comparative document Chinese patent CN 103068318 A discloses a MEMS silicon wafer wafer cutting and structure release method. The obvious problem is that wafer-level operations have not been realized, and manual splitting is required. Individual chips are picked up by a vacuum pen and placed in a tray. However, a silicon wafer contains tens of thousands of chips, and the single pick-up efficiency is low, and the subsequent structure release and test are also single-core release and test, and the efficiency is low; in addition, the two The cutting is at the same position, and the cutting positions are strictly aligned, but after cutting once, cutting again from the beginning requires two alignments, and the two alignment cutting positions cannot be completely overlapped, and the production efficiency is low.

Contents of the invention

The present invention aims at the deficiencies in the above-mentioned prior art, and provides a MEMS wafer cutting, cleaning and releasing method with high cutting efficiency, convenient cleaning and simple release.

The technical solution of the present invention to solve the above-mentioned technical problems is as follows: a MEMS wafer cutting and wafer-level release and testing method, comprising the following steps:

Step 1: Apply photoresist to the front of the MEMS wafer for protection, and use thinning equipment to thin the back. The thickness of the wafer after thinning is 100-300 μm;

Step 2: Apply UV glue on the front of the glass base, the diameter is the same as the MEMS wafer, the MEMS wafer is fixed on the transparent glass base with the front facing up, and the back of the MEMS wafer and the front of the glass base are temporarily bonded by UV glue on the back combine;

Step 3: Apply the first film to the back of the glass base carrying the MEMS wafer. The first film is a blue film, and the wafer and the glass base are integrally fixed on the special stainless steel frame for cutting;

Step 4: Cutting, step cutting is adopted, and the two-step cutting is completed continuously. There are two aligned cutting blades along the cutting direction, and the two cutting blades cut continuously; the front cutting blade cuts the wafer first, and the rear cutting blade cuts the wafer afterward , the front cutting blade cuts through the MEMS wafer, the rear cutting blade cuts into the glass base, and does not cut through the glass base, the cutting feed speed is 3-30mm/s, and the thickness of the front and rear cutting blades is 30-60μm;

Step 5: Clean and dry the wafer;

Step 6: Remove the glass base and the MEMS wafer as a whole from the first film, and use the wet method to remove the photoresist and silicon slag on the surface of the MEMS wafer;

Step 7: Put the MEMS wafer with the glass base into the adhesive removal equipment, and release the wafer-level structure. After the release, take out the wafer, and use the probe station to fix the MEMS wafer temporarily bonded on the glass base. round for wafer-level testing;

Step 8: Debonding, using a UV irradiation machine to irradiate the UV glue between the wafer and the glass base, the irradiation time is controlled at 30-100s, and the energy of the UV lamp is adjusted between 120-360mJ/cm ² , the UV The viscosity of the glue is reduced to 1-10% of the previous level;

Step 9: Apply a second film on the back of the glass base carrying the MEMS wafer, fix the glass base on the stainless steel frame, and remove the air bubbles on the back of the glass base;

Step 10: Use a splitting device to split the glass base along the MEMS wafer cutting line to ensure that all chips are completely separated, and then use a film expander to expand the wafer so that all chips are evenly expanded around;

Step 11: Use wafer-level optical inspection to sort out qualified chips

Step 12: Encapsulation test, using chip pick-up equipment, put the chip into the chip storage box, and conduct encapsulation test.

The beneficial effects of MEMS wafer cutting cleaning and releasing method among the present invention are:

(1) Step dicing is adopted in step 4, and the two-step dicing is completed continuously. The wafer can be diced into several chips in one dicing without re-alignment, the cutting positions are completely overlapped, and the dicing efficiency is high and the quality is good;

(2) In step 8, by controlling the irradiation energy and the irradiation time of the UV irradiation machine, the viscosity of the UV film is reduced to 1 to 10% of the previous value, the viscosity is lower, and the effect is better;

(3) The transparent glass base is coated with UV glue and MEMS wafers for temporary bonding, and the MEMS wafer-level glass base is structurally released and tested to achieve wafer-level release and testing, and the MEMS chip is debonded by UV irradiation Separated from the glass base, the chip is picked up by the chip pick-up equipment, and the chip is put into the storage chip box to enter the subsequent packaging process, which greatly improves the release and test efficiency;

Further, the thickness of the glass base is 200-400 μm.

Further, in step 9, the second sticking film is blue film or UV film.

Further, when pasting the UV film in step 1, pull out the UV film from the rear reel of the film laminating machine, and the length exceeds the stainless steel frame by 2-10 cm.

Further, the thickness of the UV film is 80-120mm.

Further, in step 4, the cutting depth of the rear cutting blade into the glass base is 30%-70% of the thickness of the glass base.

The beneficial effect of adopting the above-mentioned further technical scheme is: no matter how uniform the UV film is, there will be deviations in thickness. When the back-cutting blade cuts the wafer, the blade cuts to the glass base, and the depth of cutting into the glass base is 30% of the thickness of the glass base. % to 70%, so as to ensure that the wafer is fully scratched.

Further, in step 10, diffused chips are obtained, and the distance between each chip is controlled at 50-200 μm.

Further, the thickness of the front cutting blade is greater than the thickness of the rear cutting blade.

Description of drawings

Fig. 1 is the schematic diagram of the wafer after the front side is coated with photoresist in the present invention;

Fig. 2 is the glass base schematic diagram after the front is coated with UV glue in the present invention;

Fig. 3 is the schematic diagram that wafer and glass base are placed on the stainless steel frame as a whole in the present invention;

Figure 4 is a schematic diagram of the cut wafer and the glass base placed on the stainless steel frame as a whole;

The overall schematic diagram of the cleaned wafer and glass base in Figure 5;

Figure 6 The overall schematic diagram of the wafer and glass base after film expansion;

In the accompanying drawings, the names of the parts indicated by the labels are as follows: 1. wafer, 2. photoresist, 3. glass base, 4. UV glue, 5. wafer and glass base as a whole, 6. the first time Film, 7. Stainless steel frame, 8. Second film application, 9. Crystal expansion ring.

detailed description

The principles and features of the present invention are described below in conjunction with the accompanying drawings, and the examples given are only used to explain the present invention, and are not intended to limit the scope of the present invention.

As shown in Figures 1 to 6, a MEMS wafer cutting, cleaning and releasing method comprises the following steps:

Step 1: Coating the photoresist 2 on the front side of the MEMS wafer 1 for protection, and thinning the back side by thinning equipment, and the thickness of the wafer 1 after thinning is 100-300 μm.

Step 2: Apply UV glue 4 on the front of the glass base 3, the diameter of which is the same as that of the MEMS wafer 1. The MEMS wafer 1 is fixed on the transparent glass base 3 with the front facing up, and the back of the MEMS wafer 1 is covered by UV glue 4 on the back. Temporarily bond with the glass base 3 front.

Step 3: Protect the back of the glass base 3 carrying the MEMS wafer 1 with a film 6 for the first time. The first film is a blue film, and then fix the wafer and the glass base 5 on a special stainless steel frame for cutting 7 on.

Step 4: Cutting, step cutting is adopted, and the two-step cutting is completed continuously. There are two aligned cutting blades along the cutting direction, and the two cutting blades cut continuously; the front cutting blade cuts wafer 1 first, and the rear cutting blade cuts the crystal Round 1, the front cutting blade cuts through the MEMS wafer 1, and the rear cutting blade cuts into the glass base without piercing the glass base. X-direction and Y-direction) and other cutting parameters, perform alignment operation on wafer 1, adjust the θ-axis direction on Ch1, move the worktable left and right and adjust the cutting reference line, and then cut Ch2 after confirming the parameters After confirming the parameters, start scribing; the thickness of the front and rear cutting blades is 30-60 μm. After two cuts, the wafer 1 is completely cut through and separated into individual chips, as shown in Figure 4.

Step 5: Cleaning and drying the wafer 1 , the wafer 1 after cleaning is shown in FIG. 5 .

Step 6: Remove the glass base and the MEMS wafer 5 from the first film 6, and remove the photoresist 2 and silicon slag on the surface of the MEMS wafer 1 by wet stripping.

Step 7: Put the MEMS wafer 1 with the glass base into the glue removal equipment to release the wafer-level structure. After the release, take out the wafer 1 and temporarily bond it to the glass base 3 by using the probe station The MEMS wafer 1 was tested at the wafer level.

Step 8: Debonding, using a UV irradiation machine to irradiate the UV glue 4 between the wafer 1 and the glass base 3, the irradiation time is controlled at 30-100s, and the energy of the UV lamp is adjusted between 120-360mJ/cm ² , The viscosity of UV glue can be reduced to 1-10% of the previous level.

Step 9: Carry out a second film 8 on the back of the glass base 3 carrying the MEMS wafer. The second film 8 is a UV film or a blue film, and the glass base 3 is fixed on the stainless steel frame 7, and the glass base 3 The air bubbles on the backside are removed.

Step 10: Use a splitting device to split the glass base 3 along the cutting line of the MEMS wafer 1 to ensure that all chips are completely separated, and then use a film expander to expand the wafer 1 so that all chips are evenly spread around , the described film expander is provided with a crystal expansion ring 9, and after film expansion, the redundant UV film or blue film outside the crystal expansion ring 9 is crossed out, as shown in Figure 6.

Step 11: Use wafer-level optical inspection to sort qualified chips.

Step 12: Encapsulation test, using chip pick-up equipment, put the chip into the chip storage box, and conduct encapsulation test.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection of the present invention. within range.

Claims (7)

1. A MEMS wafer cutting and wafer level release and testing method, is characterized in that, comprises the following steps: Step 1: Apply photoresist to the front of the MEMS wafer for protection, and use thinning equipment to thin the back. The thickness of the wafer after thinning is 100-300 μm; Step 2: Apply UV glue on the front of the glass base, the diameter is the same as the MEMS wafer, the MEMS wafer is fixed on the transparent glass base with the front facing up, and the back of the MEMS wafer and the front of the glass base are temporarily bonded by UV glue on the back combine; Step 3: Apply the first film to the back of the glass base carrying the MEMS wafer. The first film is a blue film, and the wafer and the glass base are integrally fixed on the special stainless steel frame for cutting; Step 4: Cutting, step cutting is adopted, and the two-step cutting is completed continuously. There are two aligned cutting blades along the cutting direction, and the two cutting blades cut continuously; the front cutting blade cuts the wafer first, and the rear cutting blade cuts the wafer afterward , the front cutting blade cuts through the MEMS wafer, the rear cutting blade cuts into the glass base, and does not cut through the glass base, the cutting feed speed is 3-30mm/s, and the thickness of the front and rear cutting blades is 30-60μm; Step 5: Clean and dry the wafer; Step 6: Remove the glass base and the MEMS wafer as a whole from the first film, and use the wet method to remove the photoresist and silicon slag on the surface of the MEMS wafer; Step 7: Put the MEMS wafer with the glass base into the adhesive removal equipment, and release the wafer-level structure. After the release, take out the wafer, and use the probe station to fix the MEMS wafer temporarily bonded on the glass base. round for wafer-level testing; Step 8: Debonding, using a UV irradiation machine to irradiate the UV glue between the wafer and the glass base, the irradiation time is controlled at 30-100s, and the energy of the UV lamp is adjusted between 120-360mJ/cm ² , the UV The viscosity of the glue is reduced to 1-10% of the previous level; Step 9: Apply a second film on the back of the glass base carrying the MEMS wafer, fix the glass base on the stainless steel frame, and remove the air bubbles on the back of the glass base; Step 10: Use a splitting device to split the glass base along the MEMS wafer cutting line to ensure that all chips are completely separated, and then use a film expander to expand the wafer so that all chips are evenly expanded around; Step 11: Use wafer-level optical inspection to sort out qualified chips Step 12: Encapsulation test, using chip pick-up equipment, put the chip into the chip storage box, and conduct encapsulation test. 2. A MEMS wafer cutting and wafer-level release and testing method according to claim 1, characterized in that the thickness of the glass base is 200-400 μm. 3. A kind of MEMS wafer cutting according to claim 1 and wafer-level release and testing method, it is characterized in that, in step 9, described second sticking film is blue film or UV film. 4. A MEMS wafer cutting and wafer-level release and testing method according to claim 1, characterized in that, the thickness of the first film and the second film is 80-120mm. 5. A kind of MEMS wafer cutting according to claim 1 and release and testing method at wafer level, it is characterized in that, the depth that after-cut blade cuts into glass base in step 4 is 30%～70% of the thickness of described glass base %. 6. A MEMS wafer cutting and wafer-level release and testing method according to claim 1, characterized in that, in step 10, diffused chips are obtained, and the distance between each chip is controlled at 50-200 μm. 7. A kind of MEMS wafer cutting according to claim 1 and wafer level release and testing method, it is characterized in that, in step 4, the thickness of described front cutting blade is greater than the thickness of described rear cutting blade.