The distribution of damage produced by ion implantation of silicon at room temperature

Abstract

Experiments designed to determine the damage distribution produced by energetic heavy ions in Si are described. For low ion doses (10¹¹ to 10¹³ cm⁻²), the location of the damage peak was determined by changes, which were produced by ion damage, in the electrical properties of thin (0.6 μ), uniformly doped Si layers as a function of depth. The ratio of the peak position in the damage distribution to the peak position in the ion distribution was determined to be approximately 0.6 ± 0.1 for Si²⁹ (150 keV), P³¹ (70, 140, 200 keV), B¹¹ (60 keV), and As⁷⁵ (280 keV). A comparison of carrier removal rates and the number of displaced lattice atoms previously reported from back-scattering experiments with He ions indicates that the nature of damage produced by Si²⁹ and B¹¹ are different. In the former case, cluster damage (amorphous disordered regions) appears to be an important form of radiation damage, while in the latter case, isolated defects are the dominant form of radiation damage for room temperature implantations. Isochronal annealing studies of Si²⁹ and B¹¹ ion damage provide further support for the different nature of radiation defects produced by these species. For high doses (10¹⁴ to 10¹⁶ cm⁻²), the growth of a continuous amorphous Si layer was studied with ESR, optical transmission, and visual observation and stripping studies. The ratio of the location of the damage peak to that of the peak ion concentration was determined to be approximately 0.7 for P³¹ (140, 280 keV) and 0.8 for As⁷⁵ (280 keV). From the ESR studies, the number of displaced atoms in amorphous clusters was estimated to be 2800 per 280 keV P³¹ ion.