Liquid dopant for high phosphorus doping of silicon semiconductor - contains ethyl orthosilicate, solvent and aq. phosphoric acid, esp. for spin-on coating

摘要

Liq. dopant for Si semiconductor, consisting of ethyl orthosilicate (I), a solvent (II) and an acid aq. phase (III) for the prodn. of a layer highly doped with P, contains a high concn. (ca. 3 mole/l) of P in the form of H3PO4 and tre amt. of water is about the same as that of (I). The vol. ratio of (I), (II) and (III) is pref. ca. 3:8:3. After application, the coated semiconductor is placed in a doping furnace heated to 900 deg.C and heated at a rate of ca. 4 deg.C/min with pure O2 as carrier gas, which is replaced by N2 contg. 20% O2 on reaching the diffusion temp. (1050 deg.C). The dopant is specified for application by the spin-on process, when there is no turbidity. The high level of P doping is useful for layers with low ohmic surface resistance, e.g. for emitter diffusion of Si transistors.