Carrier mobility enhancement versus channel direction in highly-doped Si

Carrier mobilities (μ) versus Si channel directions have been studied for boron-, arsenic-, and phosphorus-implanted highly-doped Si (100) which is equivalent to a source and drain (SD) region of MOSFET by using a continuous anodic oxidation technique/differential Hall effect (CAOT/DHE) technique. The results for B-doped Si show that the hole drift mobility along the Si < 100 > channel direction can be enhanced relative to the Si < 110 > channel direction by an average of 12%, and nearly 115% near the surface. For As-doped Si the electron drift mobility along the Si < 100 > channel direction has little to no enhancement compared to the Si < 110 > channel direction. For P-doped Si, the electron drift mobility along the Si < 100 > channel direction can be enhanced relative to the Si < 110 > channel direction by an average of 10%, and as much as 18% near the surface. This study shows for the first time that electron mobility in P-doped Si is enhanced in the Si < 100 > channel direction, although the enhancement is not as significant as in B-doped Si. The results are qualitatively and semi-quantitatively consistent with the implant species-dependent effective mobility (μeff) behaviors of CMOS device I–V characteristics.