Contact type micro piezoresistive shear-stress sensor

• US 20020174727A1
• Filed: 10/22/2001
• Published: 11/28/2002
• Est. Priority Date: 11/16/2000
• Status: Active Grant

• Current Assignee: National Science Council
• Original Assignee: National Science Council
• Inventors: Chen, Gin-Shin, Ho, Jyh-Jier, Ting, Shyh-Fann, Yang, Chung-Hsien, Fang, Yean-Kuen, Hsieh, Ming-Chun, Ju, Ming-Shanng
• Granted Patent: US 6,877,385 B2
• Time in Patent Office: Days
• US Class Current: 73/841
• CPC Class Codes: A61B 2562/028 Microscale sensors, e.g. electromechanical sensors [MEMS]
• CPC Class Codes: A61B 2562/12 Manufacturing methods specially adapted for producing sensors for in-vivo measurements
• CPC Class Codes: A61B 5/103 Detecting, measuring or recording devices for testing the shape, pattern, colour, size or movement of the body or parts thereof, for diagnostic purposes A61B5/08 takes precedence; measuring aids for tailors A41H1/00; measuring instruments specially adapted for dentistry A61C19/04
• CPC Class Codes: G01L 1/18 using properties of piezo-resistive materials, i.e. materials of which the ohmic resistance varies according to changes in magnitude or direction of force applied to the material

Abstract

In this invention, a contact type micro piezoresistive shear-stress sensor is fabricated by the micro-electro-mechanical (MEMS) technology, and its main sensing part is a 2-X shaped with a flange structure, for measuring the shear stress distribution between socket of above-knee (AK) prostheses and the soft tissue of amputee'"'"'s stump. Comparing with a conventional shear stress sensor, this invention owns the following characteristics: piezo-resistivity of the monolithic silicon will be utilized to convert shear deformation of the sensor into electrical signal and a micro sensor which can measure the shear force vector acting the sensing flange.

The preparation processes of this invention are described as followings: A 3000×3000×300 μm³ diaphragm is prepared by anisotropic wet etching of bulk silicon in KOH solution and a square flange with 1100×1100×3 μm³ above the sensing diaphragm is formed through surface micromachining of deposited Si0₂ thin film. With ion implantation, two X-shapes were placed at the closely middle points between mid-edge points and center of the diaphragm where less sensitivity to normal pressure and higher sensitivity to shear stress. The sensitivity of 3.6 uv/mA-Kpa for a 70 Kpa full scale (FS) shear-stress range with shear-stress hysteresis errors of less than 8.9% FS has been measured in the developed shear-stress sensor.

Claims

1. The Contact-type Micro Piezoresistive Shear-Stress Sensor comprising Si substrate, Sensing diaphrag, Protective Membrane and Flange, specially includes two X-shape piezoresistors, each with flanges at four ends, as the primary sensing units.

2. A Contact-type Micro Piezoresistive Shear-Stress Sensor according claim 1, these sensing units consist vertically of:

(from bottom to top)

Si substrate;

Sensing diaphragm;

formed into the etched cavities at preset locations on the Si substrate;

Protective Membrane;

formed on the above-said membranes;

Flange;

formed via etching technology at the preset positions on the said Membranes as Shear-Stress sensing components.

3. A Contact-type Micro Piezoresistive Shear-Stress Sensor according claim 1, these material of sensing units consist vertically of:

(from bottom to top)

Si substrate;

made of High Doping semi-conductor piezoresistive material;

Protective Membrane;

made of SiO₂, Si₃N₄ semi-conductor protective material

Flange;

made of the same material as the above-mentioned Protective Membrane.

4. A Contact-type Micro Piezoresistive Shear-Stress Sensor according claim 1, the cavity structure of the Contact-type Micro Piezoresistive Shear-Stress Sensor, the primary sensing component, is formed by chemical etching solutions or physical etching techniques.

5. A Contact-type Micro Piezoresistive Shear-Stress Sensor according claim 1, Formation of the Flange structure includes immersion in BOE at a concentration of HF:

H₂O=1;

10, and semi-conductor preparation process of pattern etching (size and shape).