Surface metal contamination on silicon wafers after hydrogen plasma immersion ion implantation

Hydrogen plasma immersion ion implantation (PIII) in conjunction with ion-c ut has been successfully utilized to fabricate silicon-on-insulator (SOI) w afers. In order for PIII to be accepted by the semiconductor industry as a commercial process, surface metal contamination that can affect device yiel d and properties must be minimized. Total-reflection X-ray fluorescence (TX RF) analysis of hydrogen PIII silicon wafers reveals surface iron contamina tion to be greater than 10(12) atoms/cm(2). Even though ions bombard all su rfaces in a PIII chamber and the sample stage is made of stainless steel, t he small sputtering yield by hydrogen cannot fully account for the surface iron on the wafer. Further studies reveal that the sputtering contribution of ionized atmospheric species in the residual vacuum is significant. To mi nimize metal contamination in hydrogen PIII, the gas lines must be designed and sealed properly as outside air can easily leak into vacuum chamber due to the negative pressure inside the gas line. (C) 1999 Elsevier Science B. V. All rights reserved.