| 摘要 |
1501245 Semi-conductor device manufacture INTERNATIONAL BUSINESS MACHINES CORP 23 Sept 1975 [9 Dec 1974] 38901/75 Heading H1K The fast diffusing metal contaminants Au, Cu, Fe and Ni are gettered from a monocrystalline silicon body by anodically treating the body in an aqueous solution to form a region of porous silicon on at least one surface and then annealing in a non-oxidizing atmosphere to drive the contaminants to the porous region. Preferably the anodic treatment is in a 25% aqueous HF solution and produces a layer of 56% porosity 8 Á thick and the annealing effected by heating in nitrogen, argon, or helium, e.g. at 1000‹ C. for 1 hour. The gettering effect can be enhanced by introducing a dopant into the body via the porous layer to a concentration exceeding the solid solubility limit prior to annealing. After annealing the porous silicon is either covered with a layer of pyrolytic silica or removed by an HF etch containing a chelating agent. In one method the anodic treatment is restricted by oxide masking so that the porous silicon forms a pattern of closed figures. A silicon layer formed over the patterned surface after annealing and oxidation of the porous silicon thus has polycrystalline regions, in register with the porous regions, which are oxidized to mutually isolate devices formed in the remaining monocrystalline parts of the layers and to carry interconnecting layers of metallization.
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