Generation of recombination centres in semiconductor devices - by electron beam irradiation then stabilisation in medium temp. anneal after metallisation

摘要

Recombination sites are generated in a semiconductor device, pref. one using a Si substrate, by irradiation with high energy electrons. The feature is that long term stability is ensured by an anneal of at least 30 mins. at a temp. from 260-300 deg.C pref. in a vacuum with a pressure of less than 10 power -5 Torr. The device a pref. has a metallisation pattern already formed, and a passivation layer is pref. deposited after irradiation.Thee anneal, pref. 30 mins. long is pref. carried out at the same time as the passivation depsn. Also claimed is irradiation after a passivation layer has been deposited pref. a polyimide layer. The devices formed in the semiconductor substrate are pref. diodes or thyristors. USE/ADVANTAGE - Irradiation allows locallised generation of recombination centres with a density profile which can be set by the irradiation conditions. The use of electrons rather than protons, a current option, allows a deeper penetration.The concn. gradient obtd. is more predictable than when diffusion of a foreign element is used. The anneal is carried out a temp. 150-200 deg.C above normal operating temps. of the devices and at a higher temp. than currently used. This ensures improved stability.