High-vacuum packaged microgyroscope and method for manufacturing the same

• US 20030132493A1
• Filed: 03/14/2003
• Published: 07/17/2003
• Est. Priority Date: 11/01/1999
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Kang, Seok-Jin, Ko, Youn-Il, Kim, Ho-Suk
• Granted Patent: US 6,767,757 B2
• Time in Patent Office: Days
• US Class Current: 257/420
• CPC Class Codes: B81B 2201/0242 Gyroscopes
• CPC Class Codes: B81C 1/0023 Packaging together an electronic processing unit die and a micromechanical structure die MEMS packages B81B7/0032; MEMS packaging processes B81C1/00261
• CPC Class Codes: B81C 2203/0109 Bonding an individual cap on the substrate
• CPC Class Codes: B81C 2203/019 characterised by the material or arrangement of seals between parts
• CPC Class Codes: G01C 19/56 Turn-sensitive devices using vibrating masses, e.g. vibratory angular rate sensors based on Coriolis forces
• CPC Class Codes: G01P 1/023 for acceleration measuring devices
• CPC Class Codes: G01P 15/0802 Details

Abstract

A high-vacuum packaged microgyroscope for detecting the inertial angular velocity of an object and a method for manufacturing the same. In the high-vacuum packaged microgyroscope, a substrate with an ASIC circuit for signal processing is mounted onto another substrate including a suspension structure of a microgyroscope in the form of a flip chip. Also, the electrodes of the suspension structure and the ASIC circuit can be exposed to the outside through polysilicon interconnection interposed between double passivation layers. The short interconnection between the suspension structure and the ASIC circuit can reduce the device in size and prevents generation of noise, thereby increasing signal detection sensitivity. In addition, by sealing the two substrates at low temperatures, for example, at 363 to 400° C. using co-melting reaction between metal, for example, Au, and Si in a vacuum, the degree of vacuum in the device increases.

Claims

1. A high-vacuum packaged microgyroscope comprising:

a first substrate including a suspension structure suspended over a groove cavity formed at the center of one surface thereof, and inner and outer electrode pads; and

a second substrate including a signal processing circuit for sensing the motion of the suspension structure, an interconnect for extracting electrodes of the signal processing circuit and the suspension structure of the second substrate to the outside, and inner and outer metal/semiconductor composite layers for vacuum sealing the first and second substrates,

wherein the first and second substrates are placed such that the suspension structure and the signal processing circuit thereof face each other, and then sealed by co-melting bond between the outer electrode pads and the outer metal/semiconductor composite layers, and between the inner electrode pads and the inner metal/semiconductor composite layers, to form a vacuum space in the groove cavity which receives the suspension structure, so that the first and second substrates are grounded and the electrodes of the suspension structure and the signal processing circuits are extracted to the top of the second substrate through the interconnect.

2. The high-vacuum packaged microgyroscope of claim 1, wherein the suspension structure is formed of a polysilicon or monosilicon layer

3. The high-vacuum packaged microgyroscope of claim 1, wherein the inner and outer electrode pads of the suspension structures are formed of a polysilicon layer, a polysilicon/gold (Au) composite layer, or polysilicon/aluminum (Al) composite layer.

4. The high-vacuum packaged microgyroscope of claim 1, wherein the first and second substrates are formed of silicon.

5. The high-vacuum packaged microgyroscope of claim 4, wherein each of the first and second substrates further comprises a first passivation layer formed of silicon oxide or nitride to protect the first and second substrates.

6. The high-vacuum packaged microgyroscope of claim 5, wherein the interconnect is formed on both sides and the top and bottom edges of the second substrate surrounded by the first passivation layer, the both sides of the second substrate being formed by presence of through holes, and a second passivation layer is formed on the interconnect for insulation.

7. The high-vacuum packaged microgyroscope of claim 4, wherein the outer metal/semiconductor composite layers are formed on the outer sides of the second passivation layer.

8. The high-vacuum packaged microgyroscope of claim 1, wherein the degree of vacuum of the groove cavity reaches down to 10⁻

6 torr.

9. The high-vacuum packaged microgyroscope of claim 1, wherein the inner and outer metal/semiconductor composite layers are formed of a thin Au/Si or Al/Si composite layer, such that the inner and outer metal/semiconductor composite layers are melted and bonded with the inner and outer electrode pads at a low temperature of 363 to 400°

C. to create a vacuum space without causing the formation of voids at bonding sites.

10. A method for manufacturing a high-vacuum packaged microgyroscope, comprising the steps of:

(a) etching a first substrate to form a groove cavity at the center of the first substrate, where a suspension structure is to be formed, and forming a first passivation layer for protecting the first substrate;

(b) depositing a polysilicon layer on the etched surface of the first substrate and patterning the polysilicon layer into inner and outer electrode pads;

(c) forming a suspension structure by depositing a sacrificial layer over the inner and outer electrode pads, patterning the sacrificial layer to form openings to be anchors for sustaining the suspension structure, depositing polysilicon over the opening and the sacrificial layer and patterning the deposited polysilicon layer;

(d) removing the sacrificial layer by etching to float the suspension structure;

(e) forming an oxide pattern on a second substrate having a signal processing circuit for sensing the motion of the suspension structure;

(f) patterning the second substrate using the oxide pattern as an etching mask to form through holes for interconnection to the outside, removing the oxide pattern, and forming a first passivation layer for protecting the entire surface of the second substrate;

(g) forming an interconnect by depositing a polysilicon layer to cover both sides and the top and bottom edges of the second substrate surrounded by the first passivation layer, and patterning the polysilicon layer;

(h) depositing a second passivation layer to cover the interconnect and the second substrate and patterning the second passivation layer to form openings for interconnection to the outside;

(i) forming inner metal/semiconductor composite layers for connection through the openings to the interconnect, and outer metal/semiconductor composite layer for vacuum packaging on the second passivation layer; and

(j) vacuum sealing the first and second substrates by co-melting bond between the inner electrode pas of the first substrate and the inner metal/semiconductor composite layers, and between the outer electrode pads of the first substrate and the outer metal/semiconductor composite layers of the second substrate, to maintain the cavity of the suspension structure in a vacuum condition.

11. The method of claim 10, wherein in the step (b) the inner and outer electrode pads of the suspension structure are formed of a polysilicon layer, a polysilicon/gold (Au) composite layer, or a polysilicon/aluminum (Al) composite layer.

12. The method of claim 10, wherein in the step (g) the polysilicon is deposited by low pressure chemical vapor deposition (LPCVD).

13. The method of claim 10, wherein in the step (h) the second passivation layer is deposited by plasma enhanced chemical vapor deposition (PECVD).

14. The method of claim 10, wherein in the step (i), the inner and outer metal/semiconductor composite layers are formed of a Au/Si or Al/Si composite layer.

15. The method of claim 10, wherein in the step (j), the melting and bonding are performed at a low temperature of 363 to 400°

C.

16. The method of claim 10, wherein in the step (j) the degree of vacuum in the cavity reaches down to 10⁻

6 torr.