X-Ray Measurement of Lattice Strain Induced by Impurity Diffusion

Abstract

The lattice strain induced by the diffusion of phosphorus or boron in the (111) surface of silicon was studied by means of the intensity measurement of X-ray diffraction. In specimens with surface concentrations of phosphorus 6×10¹⁹ to 1.5×10²¹ cm⁻³ or boron 6×10¹⁸ to 1.2×10²⁰ cm⁻³, the diffusion-induced strains were observed to extend in the range of 350∼700μ from the surface. The lattice strain at distance D from the surface can be expressed by ε=ε₀exp(−αD), where ε₀ is the maximum strain induced by the diffusion and depends on the surface impurity concentration and α is a constant of about 100 cm⁻¹ for specimens with large dimension, ≥1 mm in thickness.