Microstructural properties of helium implanted void layers in silicon as related to front-side gettering
- Sandia National Labs., Albuquerque, NM (United States)
A new gettering concept employs helium (He) ion implantation and low temperature annealing to form a void layer below the surface of the silicon. The surface of the void walls contains many dangling bonds that are highly reactive. Once formed many of the voids grow and facet indicating a low energy configuration. The threshold He dose for void stability is observed at 1 {times} 10{sup 16} He/cm{sup 2}, while dislocation stability and retention within the void layer is not observed until 3 {times} 10{sup 16} He/cm{sup 2}. The gas ambient used during low temperature anneals as well as wet vs. dry oxidation processes have a strong influence on the dislocations associated with the voids. similarly the use of an in situ H{sub 2}-HCl etch during epitaxial silicon growth is destructive, while the H{sub 2} bake at the same temperature shows no detrimental effects on the dislocations. Voids and dislocations are stable at temperatures as high as 1,453 K that are used in epitaxial processing, and also are compatible with standard oxidation processes. Evidence suggests that hydrogen diffuses into the voids and passivates them during wet oxidation. This can be reversed by a dry oxidation at 1,073 K. Interstitial oxygen is observed to diffuse and partially passivate voids during the initial oxidation steps. Higher He doses {le} 3 {times} 10{sup 16} He/cm{sup 2} show good void and dislocation stability with all dislocations confined to the void layer. heavily doped n{sup +} silicon shows greater variations in microstructure than p{sup +} or lightly doped silicon. This study evaluates the high temperature stability of the void microstructure formed during wet and dry oxidation processes together with silicon epitaxial growth at different temperatures. Dislocation behavior pertinent to the use of voids for gettering is also discussed. A preliminary discussion of void electrical charging by available dangling bonds is presented for lightly doped and heavily doped n-type silicon.
- Research Organization:
- Sandia National Laboratories (SNL), Albuquerque, NM, and Livermore, CA (United States)
- DOE Contract Number:
- AC04-94AL85000
- OSTI ID:
- 212171
- Journal Information:
- Journal of the Electrochemical Society, Vol. 143, Issue 2; Other Information: PBD: Feb 1996
- Country of Publication:
- United States
- Language:
- English
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