Hydrogen-induced surface blistering of sample chuck materials in hydrogen plasma immersion ion implantation

Abstract

Hydrogen plasma immersion ion implantation (PIII) coupled with ion cut is an economical way to synthesize silicon-on-insulator wafers. In order to avoid premature surface blistering caused by the coalescence of hydrogen microcavities, the implantation temperature must be low (<300 °C), and sample cooling is usually required due to the high ion flux in hydrogen PIII. In addition, the entire sample chuck including the silicon wafer and all the exposed surfaces are bombarded by ions and sputtered impurities from the sample holder can be reimplanted or deposited onto the silicon wafer. Ideally, the problem can be solved if the sample chuck is made of silicon but engineering a silicon sample chuck with sufficient electrical conductivity and a cooling mechanism is very complicated. In addition, the hydrogen ions implanted into the exposed silicon chuck surface can cause surface blistering and exfoliation similar to the silicon wafer. The silicon particles released into the vacuum chamber will reduce the process yield. One practical approach is to engineer the sample chuck with stainless steel and then coat the surface with a material compatible with silicon. If the blistering resistance of the coating is better and the lifetime of the coating is sufficiently long, periodic cleaning can ensure particle and contamination free operation. In this work, we investigate the blistering behavior of three such materials, single-crystal silicon, polycrystalline/amorphous silicon, and silicon dioxide. Our results show that silicon dioxide is the best candidate, followed by polysilicon. However, the insulating nature of silicon dioxide must be considered. Our theoretical simulation results show that an oxide layer several micrometers thick will not affect the surface potential significantly even at a relatively low bias voltage.