Design of a micromachined thermal accelerometer: thermal simulation and experimental results

This paper describes numerical simulation of a micromachined thermal accelerometer and experimental measurements. The sensor principle consists of a heating resistor, which creates a symmetrical temperature profile, and two temperature detectors symmetrically placed on both sides of the heater. When an acceleration is applied, the free convection is modified, the temperature profile becomes asymmetric and the two detectors measure the differential temperature. This temperature profile and sensor sensitivity according to the distance heater-detector have been studied using numerical resolution of fluid dynamics equations with the commercial code CFD2000/STORM: it shows that the optimum distance between the temperature detectors and the heater is about 300 μm. A thermal accelerometer with 3 pairs of detectors placed at 100, 300 and 500 μm from the heater was manufactured using the techniques of micromachining silicon and experimental measurements have shown a good agreement with the numerical simulations: the experimental optimum distance between heater and detectors seems to be close to 400 μm and the differential temperature of detectors is about 3 °C/g for an operating heater power of 54 mW and an heater temperature rise AT of 238 °C. The electrical sensitivity is then 2.5 mV/g.

[1]  Zhixin Li,et al.  An optimized micromachined convective accelerometer with no proof mass , 2001 .

[2]  A. Leung,et al.  Micromachined accelerometer with no proof mass , 1997, International Electron Devices Meeting. IEDM Technical Digest.

[3]  Pierre Temple-Boyer,et al.  Residual stress in low pressure chemical vapor deposition SiNx films deposited from silane and ammonia , 1998 .

[4]  A. Leung,et al.  Micromachined accelerometer based on convection heat transfer , 1998, Proceedings MEMS 98. IEEE. Eleventh Annual International Workshop on Micro Electro Mechanical Systems. An Investigation of Micro Structures, Sensors, Actuators, Machines and Systems (Cat. No.98CH36176.

[5]  Walter Lang,et al.  Micromachined inclinometer with high sensitivity and very good stability , 2002 .

[6]  Chia-Jung Hsu.  Numerical Heat Transfer and Fluid Flow , 1981 .

[7]  Mona E. Zaghloul,et al.  Micromachined convective accelerometers in standard integrated circuits technology , 2000 .

[8]  Frédérick Mailly,et al.  Anemometer with hot platinum thin film , 2001 .

[9]  F. Mailly,et al.  Investigation of Pt/Ti bilayer on SiNx/Si substrates for thermal sensor applications , 2002 .

[10]  Mona E. Zaghloul,et al.  Convection-Based Accelerometer and Tilt Sensor Implemented in Standard CMOS , 1998 .

[11]  P. Temple-Boyer,et al.  Micromachined thermal accelerometer , 2003 .

[12]  A. Gosman,et al.  Solution of the implicitly discretised reacting flow equations by operator-splitting , 1986 .