Toshio Abe

Thermal Diffusivity of Crystalline and Liquid Silicon and an Anomaly at Melting

The thermal diffusivity of Si was measured by a laser flash method up to 1723 K. SiC and fused quartz cells were prepared for the measurement on the melt. The thermal conductivities of the crystal and the melt at the melting point were determined to be 27.3±0.3 and 56±1 W/mK, respectively. It is suggested that a new (metastable) phase exists in a narrow temperature range just above the melting point. It irreversibly transformed to ordinary liquid metal. The new phase may have very low emissivity, and/or large specific heat.

Non-Destructive Measurement of Surface Concentrations and Junction Depths of Diffused Semiconductor Layers

Infrared reflectivity of the diffused semiconductor with continuously varying impurity concentration is treated strictly, and computed numerically using an electronic computor. It is shown for thin diffused layers in silicon used for the ordinary planar technology that the wavelength of a reflectivity minimum, λmin, depends not only on the surface concentration, but also the diffusion depth. It has been found that the surface concentrations and junction depths of the diffused semiconductor layer can be determined non-destructively using λmin and sheet resistivity, provided the following seven conditions are satisfied. (1) Semiconductor materials (2) type of conductivity (3) bulk concentration (4) function-type of diffused impurity profile, F(x), are given, (5) pn junction is formed by diffusion, (6) F(x) has not unknown parameters except for the diffusion length of diffused impurity, √Dt, and (7) F(x) is a monotonic decreasing function. The figures usable for the above purpose are given for n-type complementary error function layer and n-type Gaussian layer in Si.