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Analysis of Shear Stress Type Piezoresistive Characteristics in Silicon Diaphragm Structure

실리콘 다이아프램 구조에서 전단응력형 압전저항의 특성 분석

  • Choi, Chae-Hyoung (Division. of Electronics & Information Engineering, Yeungnam University College) ;
  • Choi, Deuk-Sung (Division. of Electronics & Information Engineering, Yeungnam University College) ;
  • Ahn, Chang-Hoi (Department of Electronic Engineering, Yeungnam University)
  • Received : 2018.09.11
  • Accepted : 2018.09.27
  • Published : 2018.09.30

Abstract

In this paper, we investigated the characteristics of shear stress type piezoresistor on a diaphragm structure formed by MEMS (Microelectromechanical System) technology of silicon-direct-bonding (SDB) wafers with Si/$SiO_2$/Si-sub. The diaphragm structure formed by etching the backside of the wafer using a TMAH aqueous solution can be used for manufacturing various sensors. In this study, the optimum shape condition of the shear stress type piezoresistor formed on the diaphragm is found through ANSYS simulation, and the diaphragm structure is formed by using the semiconductor microfabrication technique and the shear stress formed by boron implantation. The characteristics of the piezoelectric resistance are compared with the simulation results. The sensing diaphragm was made in the shape of an exact square. It has been experimentally found that the maximum shear stress for the same pressure at the center of the edge of the diaphragm is generated when the structure is in the exact square shape. Thus, the sensing part of the sensor has been designed to be placed at the center of the edge of the diaphragm. The prepared shear stress type piezoresistor was in good agreement with the simulation results, and the sensitivity of the piezoresistor formed on the $2200{\mu}m{\times}2200{\mu}m$ diaphragm was $183.7{\mu}V/kPa$ and the linearity of 1.3 %FS at the pressure range of 0~100 kPa and the symmetry of sensitivity was also excellent.

본 연구에서는 Si/$SiO_2$/Si-sub 구조의 SDB (silicon-direct-bonding) 웨어퍼 상에 형성된 다이아프램(diaphragm)에 제조된 전단응력형 압전저항 특성을 분석하였다. 다이아프램은 MEMS (Microelectromechanical System) 기술을 이용해 형성하였다. TMAH 수용액을 이용해 웨이퍼 후면을 식각하여 형성된 다이아프램 구조는 각종 센서제작에 활용할 수 있다. 본 연구에서는 다이아프램 상에 형성시킨 전단응력형 압전저항의 최적의 형상조건을 ANSYS 시뮬레이션을 통하여 찾고 실제 반도체 미세가공기술을 이용해 다이아프램 구조를 형성시키고 이에 붕소(boron)을 주입하여 형성시킨 전단응력형 압전저항의 특성을 시뮬레이션 결과와 비교 분석하였다. 압력감지 다이아프램은 정방형으로 제조되었다. 다이아프램의 모서리의 중심부에서 동일한 압력에 대한 최대 전단응력은 구조물이 정방형일 때 발생한다는 것을 실험으로 확인할 수 있었다. 따라서 압전저항은 다이아프램의 가장자리 중앙에 위치시켰다. 제조된 전단응력형 압전저항은 시뮬레이션 결과와 잘 일치하였고 $2200{\mu}m{\times}2200{\mu}m$ 크기의 다이아프램에 형성된 압전저항의 감도는 $183.7{\mu}V/kPa$로 나타났으며 0~100 kPa 범위의 압력에서 1.3%FS의 선형성을 가졌으며 감도의 대칭성 또한 우수하게 나타났다.

Keywords

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