APPLICATION OF A HIGH-DENSITY INDUCTIVELY-COUPLED PLASMA REACTOR TO POLYSILICON ETCHING

An inductively coupled radio-frequency (13.56 MHz) plasma reactor has been applied to polysilicon etching for complementary metal-oxide semiconductor (CMOS) gate fabrication. The system comprises a powered flat coil situated above an upper insulating plate in the reaction chamber. It is found, using Langmuir probe measurements, to be capable of generating a high density plasma (N(i) > 10(11) cm-3) at pressures of approximately 5 mTorr. The intrinsic bias of the system is low and a capacitively coupled substrate bias from an additional 13.56 MHz generator allows independent control of ion energy. The system is capable of etching polysilicon at a high rate ( > 3000 angstrom min-1) in a Cl2 discharge with good selectivity to oxide. Etch results are discussed along with damage studies based on thermal wave, minority carrier lifetime and MOS gate oxide breakdown measurements.