HELIUM BUBBLES IN SILICON - STUDY OF THE RESIDUAL HELIUM CONTENT USING ELASTIC RECOIL DETECTION ANALYSIS

He+ ions were implanted into (100) Si at 40 keV with a fluence of 5 x 10(16) cm(-2). After implantation the samples were subjected to heat t reatment at temperatures ranging from 700 degrees C to 900 degrees C a nd times from 1 to 90 min. Transmission electron microscopy (TEM) anal ysis was performed to characterize microstructural features related to the bubble size and morphology. The TEM observations revealed the for mation of a buried layer containing a dense array of cavities already in the as -implanted samples. The residual content of He in each sampl e was evaluated using Elastic Recoil Detection (ERD). Upon annealing, while the density of bubbles decreases and the mean diameter increases , He is released from these bubbles, permeates through the matrix and evaporates from the surface, The ERD data show that the amount of He s till present in the annealed samples significantly exceeds the current theoretical predictions in the literature. The measured He content is compared to the first order gas release calculations and free paramet ers are fitted to provide an effective activation energy for the He re lease process. (C) 1998 Elsevier Science B.V.