CN104003350B

CN104003350B - A kind of wafer-grade vacuum encapsulation method of body silicon resonance type pressure transducer

Info

Publication number: CN104003350B
Application number: CN201410205595.4A
Authority: CN
Inventors: 何军; 张大成; 黄贤; 张立; 赵丹淇; 王玮; 杨芳; 田大宇; 刘鹏; 李婷; 罗葵
Original assignee: Peking University
Current assignee: Peking University
Priority date: 2014-05-15
Filing date: 2014-05-15
Publication date: 2016-08-24
Anticipated expiration: 2034-05-15
Also published as: CN104003350A

Abstract

The present invention relates to a kind of wafer-level encapsulation method being applied to body silicon resonance type pressure transducer, its step includes: 1) chooses suitable soi wafer according to the structure of resonance type pressure sensor and carries out the sheet glass of anode linkage；2) device layer to soi wafer carries out step etching, forms device architecture；3) part oxygen buried layer, dispensing device structure are removed；4) SOI sheet and sheet glass are carried out vacuum anode linkage；5) silicon chip is carried out thinning；6) by lithographic definition lead-in wire window, then etch silicon, expose oxygen buried layer；7) oxygen buried layer in lead-in wire window is removed；8) deposit silicon dioxide at silicon chip surface, form electric isolation；9) silicon dioxide of deposit is performed etching, form pad hole；10) deposit metal pad.The present invention uses wafer level packaging, and technological process is simple, it is possible to be substantially reduced the Vacuum Package cost of body silicon resonance type pressure transducer.

Description

A kind of wafer-grade vacuum encapsulation method of body silicon resonance type pressure transducer

Technical field

The invention belongs to microelectromechanical systems (MEMS) manufacture and encapsulation field, relate to a kind of wafer-grade vacuum encapsulation method, Mainly use the techniques such as step etching and anode linkage, be particularly applicable in the envelope of the wafer level to body silicon resonance type pressure transducer Dress field.

Background technology

Since the nineties, microelectromechanical systems (MEMS) technology enters the high speed development stage, is not only due to concept new Grain husk, and be with traditional devices is compared due to MEMS, has miniaturization, the prospect feature that integrated and performance is more excellent. Nowadays MEMS is widely used for the fields such as automobile, Aero-Space, information control, medical science, biology.

Pressure transducer is then one of sensor of being most widely used, is widely used in science and technology, Industry Control, aviation boat My god, the field such as biomedical.According to different principles and form pressure transducer can be divided into pressure resistance type, condenser type, piezoelectric type, Resonant mode, microelectronic vacuum formula etc..Piezoresistive pressure sensor simple in construction, subsequent process circuit is simple, but the temperature of performance Degree drift is big；Capacitance pressure transducer is highly sensitive, but subsequent process circuit is relative complex；Resonance type pressure sensor precision Height, good stability, and it is output as resonant frequency, easily combine with digital circuit.Pressure transducer is during application, past Toward needing to carry out Vacuum Package.The cost of chip-scale Vacuum Package (such as To level Vacuum Package) is bigger, thus adds pressure The cost of sensor, the method for wafer-level vacuum package then can be greatly reduced the cost of Vacuum Package.Occur at present The method of many wafer-level vacuum packages, these methods generally Making programme with device combines.But due to MEMS device The technique Making programme of part also differs, it is impossible to the method for these wafer-level vacuum packages is copied directly to every kind of device up, And different methods also has respective shortcoming.

Summary of the invention

The present invention is directed to the problems referred to above, propose a kind of wafer-level encapsulation method being applied to body silicon resonance type pressure transducer, it is possible to It is greatly reduced the packaging cost of body silicon resonance type pressure transducer.Whole technique manufacturing process (comprises the manufacture of pressure transducer With wafer-level vacuum package) key step include step etching, anode linkage, wafer thinning etc..

Specifically, the technical solution used in the present invention is as follows:

A kind of wafer-grade vacuum encapsulation method of body silicon resonance type pressure transducer, its step includes:

1) standby sheet: choose suitable SOI (silicon on insulator) silicon chip according to the structure of resonance type pressure sensor With the sheet glass for carrying out anode linkage；

2) step etching (Twi-lithography): the device layer of soi wafer is carried out step etching, and formation device architecture be (etching The degree of depth should match with the size of device design)；

3) release: remove part oxygen buried layer, dispensing device structure；

4) anode linkage: SOI sheet and sheet glass are carried out vacuum anode linkage；

5) wafer thinning: carry out thinning to silicon chip, residual thickness matches with device design size；

6) etch lead window: by photoetching (photoetching for the third time) definition lead-in wire window, then etch silicon, expose oxygen buried layer；

7) oxygen buried layer in lead-in wire window is removed；

8) deposit silicon dioxide at silicon chip surface, form electric isolation；

9) silicon dioxide of deposit is performed etching, form pad hole；

10) deposit metal pad.

Further, step 1) select the heavily doped soi wafer of device layer, device layer thickness and oxygen buried layer thickness according to sensing The range of application of device and select；And select the applicable sheet glass (such as B33 glass etc.) carrying out anode linkage with silicon.

Further, step 3) and step 7) use the method for wet etching or dry etching to remove described oxygen buried layer.Use During wet etching, it is possible to use hydrofluoric acid solution corrodes；When using dry etching, can etch with using plasma, or Person performs etching with gaseous state HF.

Further, step 5) utilize KOH solution, TMAH (Tetramethylammonium hydroxide) to carry out thinning to silicon chip.

Further, step 8) use the method deposit silicon dioxide such as LPCVD method, PECVD.

Further, step 9) first pass through photoetching (four mask) formation pad hole, then silicon dioxide in etched hole.

Further, step 10) utilize stripping technology to form metal pad.

The wafer-grade vacuum encapsulation method being applied to body silicon resonance type pressure transducer of the present invention, with existing vacuum packaging method Comparing, its advantage is: 1) wafer level packaging, greatly reduces Vacuum Package cost；2) whole set process flow process contains humorous The manufacture of formula of shaking pressure transducer and vacuum are from encapsulation, and technological process is simple.

Accompanying drawing explanation

Fig. 1 is standby sheet profile；Wherein 1 attaches most importance to doped monocrystalline silicon, and 2 is oxygen buried layer (silicon oxide), and 3 for being lightly doped monocrystal silicon Substrate, 4 is sheet glass.

Fig. 2 is profile after step etching.

Fig. 3 is profile after release.

Fig. 4 is profile after anode linkage.

Fig. 5 is profile after wafer thinning.

Fig. 6 is profile after etch lead window.

Fig. 7 is that corrosion lead-in wire window buries profile after oxygen.

Fig. 8 is profile after PECVD silicon dioxide, and wherein 5 is the silicon dioxide of PECVD.

Fig. 9 is to form profile behind pad hole.

Figure 10 is profile after deposit metal, and wherein 6 is metal level.

Detailed description of the invention

The present invention proposes a kind of wafer-grade vacuum encapsulation method being applicable to body silicon resonance type pressure transducer.Below in conjunction with enforcement The present invention will be further described for example and accompanying drawing.

The present embodiment manufactures pressure transducer based on tuning fork resonator, and the technological process of the wafer level packaging of employing such as Fig. 1 is extremely Shown in Figure 10:

A) standby sheet

The thickness of the device layer 1 (heavy doping monocrystal silicon) of SOI sheet is 30 μm, and resistivity is 0.01 Ω cm, oxygen buried layer 2 Thickness is 2 μm, and 3 is hydrogen doping monocrystalline substrate, and sheet glass 4 is B33 glass, as shown in Figure 1.

B) step etching (Twi-lithography)

The device layer 1 of soi wafer being carried out step etching, forms tuning fork resonator structure, after etching, pattern is as shown in Figure 2. The etching depth of step is respectively 5 μm and 30 μm.

C) release

Utilize the oxygen buried layer below Fluohydric acid. corrosion device structure, dispensing device structure, it should be noted that release reasonable when carrying out technique Time, after release, profile is as shown in Figure 3.

D) anode linkage

SOI sheet and sheet glass are carried out vacuum anode linkage, as shown in Figure 4.

E) wafer thinning

Utilizing KOH solution to carry out thinning to silicon chip, whole SOI sheet residual thickness is 42 μm, as shown in Figure 5.

F) etch lead window

By third time lithographic definition lead-in wire window, size is 200 μ m 200 μm, then etches silicon, exposes oxygen buried layer, as Shown in Fig. 6.

G) corrosion lead-in wire window buries oxygen

Utilize oxygen buried layer inside Fluohydric acid. corrosion lead-in wire window, as shown in Figure 7.

H) PECVD silicon dioxide

PECVD method deposit silicon dioxide 5 being used above at silicon chip, thickness is 1 μm, forms electric isolation, as shown in Figure 8.

I) etching silicon dioxide, forms pad hole

Carrying out four mask, form pad hole, size is 180 μ m 180 μm, and silicon dioxide in etched hole, such as Fig. 9 Shown in.

H) deposit metal pad

Utilizing stripping technology to form metal pad, metal level 6 uses Cr (30nm)/Au (180nm) composite construction, such as Figure 10 Shown in.

Describe an application of the inventive method above by an embodiment, be i.e. applied to tuning fork resonance type pressure sensor Manufacture and wafer-level vacuum package.But it should be recognized that the inventive method is suitable for the circle of the pressure transducer of other resonance structures Chip size package, when carrying out step etching, by adjusting domain structure, can form different types of device architecture, such as sound Fork comb-tooth-type, two-end fixed beam formula, etc..It will be understood by those of skill in the art that in the scope without departing from this patent essence In, structure can be done certain changing and modifications, its its preparation process is also not necessarily limited to the preparation technology in the present embodiment.This Bright protection domain should be as the criterion with described in claim.

Claims

1. a wafer-grade vacuum encapsulation method for body silicon resonance type pressure transducer, comprises manufacture and the vacuum of resonance type pressure sensor From encapsulation, and resonance type pressure sensor is encapsulated in vacuum chamber, and its step includes:

1) soi wafer is chosen and for carrying out the sheet glass of anode linkage according to the structure of body silicon resonance type pressure transducer；

2) device layer to soi wafer carries out step etching, forms device architecture；

3) the part oxygen buried layer of soi wafer, dispensing device structure are removed；

4) device layer and the sheet glass of soi wafer are carried out vacuum anode linkage；

5) carrying out thinning to silicon chip, residual thickness matches with device design size；

6) by lithographic definition lead-in wire window, then the silicon in etching soi wafer substrate layer, exposes oxygen buried layer；

7) oxygen buried layer in lead-in wire window is removed；

8) deposit silicon dioxide at silicon chip surface, form electric isolation；

9) silicon dioxide of deposit is performed etching, form pad hole；

10) deposit metal pad.

2. the method for claim 1, it is characterised in that: step 1) described soi wafer is the heavily doped SOI of device layer Silicon chip.

3. the method for claim 1, it is characterised in that: step 3) and step 7) use wet etching or dry etching Method remove described oxygen buried layer.

4. method as claimed in claim 3, it is characterised in that: use hydrofluoric acid solution to carry out described wet etching, use plasma Body etching or gaseous state HF carry out described dry etching.

5. the method for claim 1, it is characterised in that: step 5) utilize KOH solution or TMAH that silicon chip is carried out Thinning.

6. the method for claim 1, it is characterised in that: step 8) use LPCVD or PECVD method deposit two Silicon oxide.

7. the method for claim 1, it is characterised in that: step 9) first pass through and be lithographically formed pad hole, then etched hole Interior silicon dioxide.

8. the method for claim 1, it is characterised in that: step 10) utilize stripping technology to form metal pad.