Method of fabricating silicon capacitive sensor

US6465271B1 · kind B1 · utility

Inventors

• Wen-Hsiung Ko · Taichung, TW
• Qiang Wang · Beijing, CN

Key dates

• Filing date: Jan 5, 2001
• Grant date: Oct 15, 2002
• Expiry date: Jan 5, 2021

Classification

• Technology area (CPC G): Physics
• CPC primary: G01L17/00
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

Manufacturing all-silicon force sensors, such as capacitive pressure sensors (100, 200) that have long term stability and good linear sensitivity, and can be built into of a pneumatic tire. The sensors include buried electrical feedthrough (112b) to provide an electrical connection into a sealed silicon cavity (108). The buried feedthrough consists of a conductor (112b) in a shallow groove (106) in a substrate (102), communicating between the sensing cavity (108) and an external contact area (110). The sensor designs also feature a method for forming a silicon-to-silicon fusion bond (SFB) wherein at least one of the two surfaces (152, 252) to be has a tough silicon surface unsuitable for good SFB joints because it was bonded heavily boron-doped by means of diffusion. The method of this invention includes preparing each doped surface (152, 252) for SFB by polishing the surface with a Chemical-Mechanical Polishing (CMP) process. The sensor designs can also include optional reference capacitors (141, 241) on the same chip (100, 200) as the sensing capacitor (140, 240). The reference capacitors (141, 241) are insensitive to pressure (force), but respond to ambient temperature changes i…