Change of Surface and Electrical Characteristics of Silicon Wafer by Wet Etching(1) - Surface Morphology Changes as a Function of HF Concentration -

Abstract

The electrical properties and surface morphology changes of a silicon wafer as a function of the HF concentration as the wafer is etched were studied. The HF concentrations were 28, 30, 32, 34, and 36 wt%. The surface morphology changes of the silicon wafer were measured by an SEM (<TEX>$80^{\circ}$</TEX> tilted at <TEX>${\times}200$</TEX>) and the resistivity was measured by assessing the surface resistance using a four-point probe method. The etching rate increased as the HF concentration increased. The maximum etching rate 27.31 <TEX>${\mu}m/min$</TEX> was achieved at an HF concentration of 36 wt%. A concave wave formed on the wafer after the wet etching process. The size of the wave was largest and the resistivity reached 7.54 <TEX>$ohm{\cdot}cm$</TEX> at an 30 wt% of HF concentration. At an HF concentration of 30 wt%, therefore, a silicon wafer should have good joining strength with a metal backing as well as good electrical properties.