Physical and Electrical Characterization of Doped Amorphous Silicon Resistor

Abstract

Amorphous Silicon (Si) is widely used in CMOS technology, and now applications can be found in MEMs/Sensor products because of its remarkable performance. In this paper, low temperature PECVD amorphous Si process was developed at 200mm CMOS BEOL with low stress at about -30MPa (compressive mode), and there is no peeling or crack problem for the film deposition. Good thickness and sheet resistance uniformity can be achieved of the amorphous Si film. Its thickness uniformity can reach 0.56%, and Rs uniformity can reach 1.22%. Then it was used to fabricate sensing resistor for temperature sensor application, which was defined by thin Ti\TiN metal layer pattern. To achieve good contact performance, Ar plasma etching process was introduced before metal layer deposition, and its etch rate can be well controlled. From the IV curve, it can be seen that good ohmic contact can be achieved. High selectivity thin metal layer etching process was developed with no process damage to amorphous Si, and 49 point resistance uniformity within wafer can be controlled to less than 2%. Thermal coefficient of resistance (TCR) was measured from 25°C to 40°C, and TCR value can reach at about 1.88%. 1/f Noise performance was evaluated for the resistor, and 1/f noise power at 100Hz can be controlled to -148dB. The measured data of doped amorphous Si resistor can well meet requirements of temperature based sensor.