| 摘要 |
In the manufacture of a semi-conductor device (see Division H1) a layer of silicon is first epitaxially deposited on a silicon substrate and a glassy silico-phosphate layer is then formed on the resulting silicon body. Prior to deposition the wafer surface is cleaned by heating to at least 1250 DEG C. in an atmosphere of hydrogen. Hydrogen chloride may also be used in the cleaning process. The silicon wafer is then heated to 900-1350 DEG C., and a mixture comprising dry hydrogen, the vapour of a volatile silicon compound and the vapour of a compound of a required dopant, is passed over it. The silicon compound may be silane, silicon tetrachloride or tetrabromide, trichlorosilane, dichlorosilane, tribromosilane or silicon tetraiodide. The dopant compound may be boron hydride or trichloride, or boron tribromide, to produce a P-type epitaxial layer. For an N-type layer the dopant compound may be the hydride of phosphorus, arsenic or antimony, or a volatile halide such as phosphorus or arsenic trichloride. Subsequent to the above deposition a layer of a glassy silico-phosphate is formed on the silicon wafer by causing it to react with phosphorus pentoxide in gaseous form or in solution, under the influence of heat in the temperature range 1000-1300 DEG C. After deposition the wafer is cooled slowly. This layer preferentially absorbs fast-diffusing contaminants from the silicon wafer, and may subsequently be removed. Alternatively it may be left on the wafer, providing a phosphorus-rich zone at the wafer surface. |
