Amorphization of silicon by high dose germanium ion implantation with no external cooling mechanism

Si(100) wafers were implanted by using three different methods: single-energy Ge⁺ ion implantation, double-energy Ge⁺ and Ge²⁺ ion implantation, and double-energy Si⁺ and Ge⁺ ion implantation. The single-energy implantations were performed at energies from 50 to 180 keV, over the range of 8.38 × 10¹⁵ to 5.80 × 10¹⁶ ions/cm². By keeping the ion beam power density below 0.09 W/cm², full surface amorphization could be achieved in the single-energy Ge⁺ implanted samples. Also beam heating was suppressed during implantation, although the implanter had no external cooling. In addition, a two-step single-energy implant technique using sequentially high and low power densities was further developed in order to reduce implantation times. In order to locate the amorphous/crystalline (a/c) interfaces far away from the concentration peak positions of the implanted Ge⁺ ions, the double-energy Ge⁺ and Ge²⁺, and Si⁺ and Ge⁺ implantations were carried out. Three Ge⁺ implanted wafers were either pre-implanted with 180 keV Si⁺ ions, or post-implanted with 360 keV Ge²⁺ ions, respectively, in order to locate deeper a/c interfaces. Channelling effect measurements indicate that the double-energy Ge⁺ and Ge²⁺ implantation is a preferable technique for wilfully tailoring the amorphous depth and the Ge peak position.