p-Channel MOSFET's in LPCVD PolySilicon

Abstract

p-channel MOSFET's have been fabricated in LPCVD polysilicon. A 5000-Å n ⁺ poly acts as the gate electrode on which a 500-Å thermal oxide is grown to act as the gate insulator. Then a 1500-Å LPCVD polysilicon layer is deposited at 620°C and is subsequently boron doped to form the conductive channel. Devices with channel length as small as 2 µm show well-behaved transistor characteristics. The drive current and leakage current are as suitable for usage as load element in memory applications. At large gate voltages the accumulation hole mobility is 9 cm ² /V.s. The drain-to-source breakdown voltage exceeds -20 V.