Process conditions affecting hot electron trapping in dc magnetron sputtered MOS devices

Abstract

Process parameters affecting hot electron trapping in MOS capacitors produced by magnetron sputtered aluminum were studied. The electron traps considered are process induced and affected by changes in sputtering parameters. Devices were fabricated under each of the following varying conditions: target presputter time, deposition power, source to substrate distance, process pressure, deposition thickness, anode bias voltage, and annealing temperature. Mobile ion concentration, surface state, and flatband voltage measurements revealed values less than 4×1010 charges/cm2, 3.7×1010 states/cm2 eV, and −1.2 V after a 400°C anneal in 10% H2/90% N2 forming gas mixture. Hot electron injection measurements of the devices after the same anneal resulted in minimum effective electron trapping (4.25×1010 electrons/cm2 trapped for 9×1014 electrons/cm2 injected) when the process conditions were optimized. The optimized parameters reduced the trapping density and improved device performance.