OXYGEN PRECIPITATION CHARACTERIZATION USING THE ELYMAT TECHNIQUE

摘要

In processed wafers the depth of the precipitate-free zone and the density of bulk microdefects are of great importance. In this case the constant diffusion length is no longer valid. A two region model (defect-free/precipitated region) was assumed with two different diffusion lengths L_D in a depth t. Solving the set of differential equations a three-dimensional picture of denuded zone depth and diffusion length in the precipitated bulk of the wafer is obtained. Investigating precipitated wafers using the Electrolytical Metal Tracer technique a correlation between the bulk microdefects and the measured minority carrier diffusion length was found. An empirical expression was determined to estimate Bulk Micro Defect density in the range from 8 × 10~4 to 2 × 10~7 cm~(-2). This means for practical application to receive more information on the oxygen precipitation behavior of the whole wafer using an improved Electrolytical Metal Tracer technique.