Damage evolution in helium-hydrogen co-implanted (100) silicon

The modifications induced in single-crystal silicon by helium and hydrogen complantation have been investigated as a function of isochronal heat treatments in the 100-900 degreesC temperature range. 30 keV helium ions were implanted into (100) p-type silicon wafer held at RT with a dose Of 1x10(16) cm(-2); Successively 1x10(16) cm(-2) hydrogen ions were implanted at 24 keV. Various analytical techniques have been used to characterize the in-depth samples: 2 MeV He-4(+) backscattering in channeling conditions (RBS-channeling) to detect damage distribution; elastic recoil detection (ERD) technique with 8 MeV N-15(++) and 2 MeV He-4(+) to measure the helium and hydrogen concentration; cross sectional transmission electron microscopy (XTEM) analysis to characterize the distribution of the defects. Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM) were used to analyze the surface morphology. According to the backscattering-channeling data two kinds of damage are present: one, damage A, located in a narrow region at a depth corresponding to helium and hydrogen mean projected range and another one, damage B, located from 270 nm to the sample surface. Damage A increases up to 400 degreesC and at higher temperatures tends to disappear. Damage B reaches a maximum after 500 degreesC and stays constant at higher temperatures. Above 500 degreesC the sample surface exhibits blistering and exfoliation phenomena. The area fraction covered by the blisters is proportional to the dechanneling signal caused by damage B. Above 700 degreesC helium and hydrogen are completely desorbed. The presence of blisters and of the related dechanneling signal indicate that silicon is plastically deformed.