The Fabrication by using Surface MEMS of 3C-SiC Micro-heaters and RTD Sensors and their Resultant Properties

Abstract

The electrical properties and the microstructure of nitrogen-doped poly 3C-SiC films used for micro thermal sensors were studied according to different thicknesses. Poly 3C-SiC films were deposited by LPCVD (low pressure chemical vapor deposition) at 900 o C with a pressure of 4 torr using SiH 2 Cl 2 (100%, 35 sccm) and C 2 H 2 (5% in H 2 , 180 sccm) as the Si and C precursors, and NH 3 (5% in H 2 , 64 sccm) as the dopant source gas. The resistivity of the poly SiC films with a 1,530 Å thickness was 32.7 Ω-cm and decreased to 0.0129 Ω-cm at 16,963 Å. The measurement of the resistance variations at different thicknesses were carried out within the 25 o C to 350 o C temperature range. While the size of the resistance variation decreased when the films thickness increased, the linearity of the resistance variation improved. Micro heaters and RTD sensors were fabricated on a Si 3 N 4 membrane by using poly 3C-SiC with a 1um thickness using a surface MEMS process. The heating temperature of the SiC micro heater, fabricated on 250 ㎛ⅹ250 ㎛ Si 3 N 4 membrane was 410 o C at an 80 mW input power. These 3C-SiC heaters and RTD sensors, fabricated by surface MEMS, have a low power consumption and deliver a good long term stability for the various thermal sensors requiring thermal stability.