CN1319139C - Production of local vacuum sealing protective structure of silicon based sensor flexible piece - Google Patents

Abstract

The present invention relates to a manufacturing method for a movable piece local vacuum seal protective structure of a silicon base sensor. A silicon cap and a movable piece of a silicon base sensor chip carry out vacuum seal encapsulation, and the movable piece local vacuum seal protective structure is formed. The method comprises the processing steps: making the silicon cap; making metal masking stencil plates according to designed seal ring figures; leaking and printing seal slurry materials on the surface of a seal ring of the silicon base sensor chip; sealing the silicon cap and the seal slurry materials under vacuum environment. The method is used for making the local vacuum seal protective structure when the sealing surface of the movable piece of the silicon base sensor in microelectron machinery systems (MEMS).

Description

Manufacturing method of partial vacuum sealing protection structure for movable part of silicon-based sensor

(1) Technical field

The invention relates to a method for making a partial vacuum sealing protection structure of a movable part of a silicon-based sensor, which is used for the partial vacuum sealing protection structure when there are interconnection lines on the sealing surface of the movable part of a silicon-based sensor of a microelectronic machine (MEMS). make.

(2) Background technology

As we all know, if the micromechanical silicon-based sensor is to work reliably and stably, the protection of the movable parts becomes a necessary condition for reliable and stable operation. The most effective method for the protection of movable parts is to seal the whole or part of the device, and the protection of movable parts is divided into general protection and vacuum sealing protection. The so-called general protection belongs to the integrated circuit packaging methods, such as spot welding, parallel seam welding, solder welding, cold welding and plastic sealing. The vacuum sealing protection method is to place the sensor device in a vacuum environment and apply special processes such as electrostatic bonding, gold-silicon solder, low-melting glass solder, etc. for packaging. The reason for adopting vacuum sealing protection is that the movable parts of such devices can only move without damping in a vacuum sealing environment, and cannot work normally and stably when there is gas resistance. For example, resonant pressure sensors, gyroscope sensors, etc. all have protection problems for movable parts, and they are vacuum-tight protection.

The current vacuum sealing protection method for movable parts is a single silicon-glass electrostatic bonding and silicon-silicon bonding without interconnection lines on the sealing surface. At present, there is no report on the manufacturing method of the local vacuum sealing protection structure with interconnecting lines on the sealing surface of the movable part. Shown in Fig. 1 is an existing silicon-based sensor chip, which has a movable part 1, interconnection lines 2 are arranged on the movable part 1, and the movable part 1 is made on the silicon wafer 3, and the silicon wafer 3 and the silicon base 4 bonding, the silicon base 4 is bonded to the glass bottom 5. FIG. 2 shows a vacuum-tight protective structure encapsulated by a solder glass 7 and a silicon cap 6 on the movable part 1 of the sensor in FIG. 1 .

(3) Contents of the invention

The technical problem to be solved by the present invention is to invent a method for making a partial vacuum sealing protection structure for the movable part of the silicon-based sensor, so that when there are interconnecting lines on the sealing surface of the movable part of the silicon-based sensor, it can be conveniently made into a partial vacuum seal Protective structure to ensure reliable and stable work of movable parts.

The technical solution of the present invention to solve the above-mentioned technical problems is to vacuum-tightly package the silicon cap and the movable part of the silicon-based sensor chip to form a partial vacuum-sealed protection structure for the movable part. The manufacturing method includes the following steps:

(1) making a silicon cap;

(2) Make a metal mask plate according to the designed sealing ring pattern;

(3) Missing the sealing slurry on the surface of the silicon-based sensor chip sealing ring;

(4) Seal the silicon cap with the sealing slurry in a vacuum environment.

The process steps of making the silicon cap are:

(1) Mask the unpolished silicon wafer according to the silicon cap design pattern;

(2) A silicon cap cavity is formed by chemical etching.

The chemical etching method is to use hydrofluoric acid: ammonium fluoride: water=3ml: 6g: 10ml solution to corrode the silicon dioxide on the surface of the silicon cap cavity; then use nitric acid: hydrofluoric acid=10:1 solution to corrode the silicon dioxide 8-10 minutes to form a 6--10μm deep silicon cap cavity.

The method of slip printing sealing paste on the sealing ring surface of the silicon-based sensor chip is:

(1) The low-melting glass powder is prepared into a sealing slurry with alcohol;

(2) Coating a photoresist protective layer on the position other than the surface of the silicon-based sensor chip sealing ring of the sealing slurry to be missed;

(3) make the silicon on the surface of the sealing ring of the silicon-based sensor chip rough with a chemical etching method;

(4) using the metal mask plate to print the sealing paste on the surface of the sealing ring;

(5) Pre-baking the silicon-based sensor chip printed with the sealing paste in an oven at 200° C. for 15 minutes.

The chemical etching method is to corrode the silicon on the surface of the sealing ring for 1 minute at room temperature with a solution prepared at a ratio of hydrofluoric acid: 50% dilute nitric acid: glacial acetic acid = 1:3:1.

In a vacuum environment, the method of sealing the silicon cap with the sealing slurry is:

(1) Place the silicon cap on the dried sealing slurry, pressurize it with a briquetting block of 10 grams, and put it in a quartz boat;

(2) Place the above-mentioned quartz boat equipped with silicon-based sensor chips in a vacuum furnace with a vacuum degree of 133×10 ^-3 Pa and a temperature of 460±10°C for 6--10 minutes, then push it into the cooling zone to cool for 10-- Take it out after 20 minutes, and the partial vacuum-tight protection structure of the movable part of the silicon-based sensor is made.

Beneficial effect. Because the present invention adopts the above-mentioned technical scheme, it can conveniently make a partial vacuum-sealed protection structure for the movable part when there is an interconnection wire on the movable part of the silicon-based sensor, ensuring reliable and stable operation of the movable part.

(4) Description of drawings

Fig. 1 is the structural sectional schematic diagram of a kind of existing silicon-based sensor chip of the present invention;

Fig. 2 is a schematic cross-sectional view of a partial vacuum sealing protection structure fabricated on the movable part of the silicon-based sensor chip in Fig. 1 by the method of the present invention.

(5) Specific implementation methods

The specific implementation manner of the present invention is not limited to the following description, and the method of the present invention will be further described below in conjunction with the accompanying drawings. The inventive method comprises the following steps:

1. Make the silicon cap 6 according to the design pattern of the silicon cap. The specific process steps are:

(1) Mask the unpolished silicon wafer according to the design pattern of the silicon cap 6 . The method of masking is to use photoresist (such as KPR glue) to mask the part other than the designed silicon cap cavity, exposing the silicon cap cavity.

(2) Form the silicon cap cavity 8 by chemical etching. The chemical etching method is to use hydrofluoric acid: ammonium fluoride: water=3ml: 6g: 10ml solution to corrode the silicon dioxide (SiO ₂ ) on the surface of the silicon cap cavity; then use nitric acid: hydrofluoric acid=10:1 solution The silicon under the silicon dioxide (SiO ₂ ) is etched for 8-10 minutes to form a silicon cap cavity 8 with a depth of 6-10 μm.

2. Make a metal mask according to the designed sealing ring pattern. That is to use the general method to input the graphic data of the sealing ring into the computer, and use the KLS-126 laser machine to etch the 0.1mm thick stainless steel sheet, and make it into a metal mask according to the program.

3. Print the sealing paste on the surface of the silicon-based sensor chip sealing ring. Its process steps are:

(1) The low-melting glass powder is prepared into a sealing paste with alcohol. The low-melting glass powder adopts the NS series low-melting glass powder produced by the Glass Research Institute of China Building Materials Research Institute, and uses a common method to prepare a sealing slurry with 10-20% alcohol.

(2) Coating a protective layer of photoresist (such as KPR glue) on the parts other than the surface of the silicon-based sensor chip sealing ring where the sealing paste is to be missed printed.

(3) The silicon on the surface of the sealing ring of the silicon-based sensor chip is roughened by chemical etching. The chemical etching method is as follows: use a solution prepared at a ratio of hydrofluoric acid: 50% dilute nitric acid: glacial acetic acid = 1:3:1 to etch the silicon on the surface of the sealing ring for 1 minute at room temperature.

(4) Using the metal mask plate to leak-print the sealing paste onto the surface of the sealing ring. The silicon-based sensor chip to be missed is placed in the fixture of the SY-00 manual screen printing machine produced by China Panda Group, sucked by vacuum, aligned with the alignment mark, put on the metal mask plate, and the prepared sealing paste Material leaks onto the sealing ring.

(5) Pre-baking the silicon-based sensor chip printed with the sealing paste in an oven at 200° C. for 15 minutes.

4. Seal the silicon cap 6 with the sealing slurry in a vacuum environment. Its process steps are:

(1) Place the silicon cap 6 on the dried sealing slurry, pressurize it with 10 grams of briquetting, and put it in the quartz boat, and wait for the equipment to operate normally;

(2) Place the quartz boat equipped with silicon-based sensor chips in a vacuum furnace with a vacuum degree of 133×10 ^-3 Pa and a temperature of 460±10°C for 6-10 minutes, and then the sealing paste will be transformed into solder glass 7. Push it into the cooling zone to cool for 10-20 minutes and then take it out to complete the manufacture of the partial vacuum sealing protection structure of the movable part of the silicon-based sensor.

In Fig. 1 and Fig. 2, 1 represents the movable element, 2 represents the interconnection line, 3 represents the silicon wafer, 4 represents the silicon substrate, 5 represents the glass bottom, 6 represents the silicon cap, 7 represents the solder glass, and 8 represents the silicon cap cavity. All chemical reagents used in the method of the present invention are chemically pure.

Claims (5)

1. A method for making a partial vacuum-sealed protective structure for the movable part of a silicon-based sensor, wherein the silicon cap and the movable part of the silicon-based sensor chip are vacuum-tightly packaged to form a partial vacuum-sealed protective structure for the movable part, which is characterized in that : the method includes the following steps: (1) making a silicon cap; (2) Make a metal mask plate according to the designed sealing ring pattern; (3) coat photoresist protective layer on the position other than the silicon-based sensor chip seal ring surface of the sealing slurry to be missed, make the silicon on the silicon-based sensor chip seal ring surface rough with chemical etching, use the described The sealing paste prepared by mixing low-melting glass powder with alcohol is leak-printed on the surface of the sealing ring on the metal mask plate, and the silicon-based sensor chip with the leak-printing sealing paste is pre-baked in an oven at 200 ° C for 15 minutes; (4) Seal the silicon cap with the sealing slurry in a vacuum environment. 2. The method for manufacturing the partial vacuum-sealed protective structure of the movable part of the silicon-based sensor according to claim 1, characterized in that: the process steps of making the silicon cap are: (1) Mask the unpolished silicon wafer according to the silicon cap design pattern; (2) A silicon cap cavity is formed by chemical etching. 3. The manufacturing method of the partial vacuum-sealed protective structure of the movable part of the silicon-based sensor according to claim 2, characterized in that: the chemical etching method is to use hydrofluoric acid: ammonium fluoride: water = 3ml: 6g: Etch the silicon dioxide on the surface of the silicon cap cavity with 10ml solution; then use nitric acid: hydrofluoric acid = 10:1 solution to etch the silicon under the silicon dioxide for 8--10 minutes to form a 6--10 μm deep silicon cap cavity. 4. The manufacturing method of the partial vacuum-sealed protective structure of the movable part of the silicon-based sensor according to claim 1, characterized in that: the chemical etching method is to use hydrofluoric acid: 50% dilute nitric acid: glacial acetic acid = 1:3 The solution prepared at a ratio of :1 etches the silicon on the surface of the sealing ring for 1 minute at room temperature. 5. The manufacturing method of the partial vacuum sealing protection structure of the movable part of the silicon-based sensor according to claim 1, characterized in that: in a vacuum environment, the method of sealing the silicon cap with the sealing slurry is: (1) Place the silicon cap on the dried sealing slurry, pressurize it with a briquetting block of 10 grams, and put it in a quartz boat; (2) Place the quartz boat equipped with silicon-based sensor chips in a vacuum furnace with a vacuum degree of 133×10 ^-3 pa and a temperature of 460±10°C for 6-10 minutes, then push it into the cooling zone to cool for 10- - Remove after 20 minutes.

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