Electron irradiation process of glass passivated semiconductor devices for improved reverse characteristics

Claim 2

A process for manufacturing a semiconductor device having improved reverse characteristics comprising the steps of: (a) preparing a semiconductor assembly comprising a semiconductor body which has at least one p-n junction therein and first and second main surfaces at the both ends thereof, an edge face of the p-n junction being exposed to the body, and first and second electrodes each being in ohmic contact with the corresponding main surfaces, (b) forming a passivating coating of an alkali-free glass layer on the edge face to protect the body from mechanical damage thereto, (c) irradiating the semiconductor body through the coating to radiation rays sufficient to cause lattice defects in the body so as to shorten the life time of the minority carriers down to a predetermined value and to increase the reverse leak current at the p-n junction, and (d) annealing the semiconductor assembly after the irradiation, said annealing being carried out at an elevated temperature for a period of time sufficient to recover the electric characteristics damaged in the step of the irradiation, the annealing being carried out under such a condition that the increased reverse leak current is decreased to a predetermined value smaller than the increased value, while the degree of the shortened life time is substantially maintained during the annealing.

Claim 3

The process as defined in claim 1, wherein the glass layer has a coefficient of linear thermal expansion approximate to that of the semiconductor body.

Claim 4

The process as defined in claim 1, wherein the glass layer has the following composition: ______________________________________ ZnO 50 to 80% by weight B.sub.2 O.sub.3 5 to 30% by weight SiO.sub.2 1 to 10% by weight PbO up to 10% by weight Sb.sub.2 O.sub.3 up to 5% by weight SnO.sub.2 up to 5% by weight Al.sub.2 O.sub.3 up to 5% by weight ______________________________________

Claim 5

The process as defined in claim 1, wherein the annealing is carried out under the condition corresponding to a condition not less than 0.5 hour at 250° C. but not more than 0.5 hour at 350° C.

Claim 6

The process as defined in claim 1, wherein the exposure to radiation is an amount corresponding to 1×10 13 to 1×10 16 electrons/cm 2 .

Claim 7

The process as defined in claim 1, wherein the annealing is carried out under the conditions defined by 250° C. for 0.5 to 50 hours to 350° C. for 0.1 to 0.5 hour.

Claim 8

A semiconductor device with shortened life time characteristics and improved reverse characteristics which comprises (1) a semiconductor body having at least one p-n junction therein exposed to a side face of the body and first and second main surfaces thereof at the opposite ends, (2) first and second electrodes being in ohmic contact with the first and second main surfaces, and (3) a glass coating for mechanically protecting the semiconductor body as well as passivating the edge face, wherein the glass coating in intimate contact with the edge face contains zinc oxide and boron oxide as main components but contain no atoms of alkali metals, the semiconductor body and the glass coating being subjected to irradiation through the coating to radiation rays sufficient to cause lattice defects in the body so as to shorten the life time of the minority carriers down to a predetermined value, and annealing at an elevated temperature for a period of time sufficient to recover the electric characteristics damaged in the step of the irradiation, the improvement that comprises employing as the coating an alkali-free glass layer, whereby a reverse leak current at the p-n junction is increased in the irradiation step, and the annealing is carried out under such condition so that the increased reverse leak current is decreased to a predetermined value smaller than the increased value, while the degree of the shortened life time is substantially maintained in the step of the annealing, whereby the reverse leak current is substantially reduced to a value smaller than that measured after the irradiation.

Claim 9

A semiconductor device with shortened life time characteristics and improved reverse characteristics which comprises (1) a semiconductor body having at least one p-n junction therein exposed to a side face of the body and first and second main surfaces thereof at the opposite ends, (2) first and second electrodes being in ohmic contact with the first and second main surfaces, and (3) a glass coating for mechanically protecting the semiconductor body as well as passivating the edge face, wherein the glass coating in intimate contact with the edge face contains zinc oxide and boron oxide as main components but contain no atoms of alkali metals, the semiconductor body and the glass coating being subjected to irradiation through the coating to radiation rays sufficient to cause lattice defects in the body so as to shorten the life time of the minority carriers down to a predetermined value, and annealing at an elevated temperature for a period of time sufficient to recover the electric characteristics damaged in the step of the irradiation, the improvement that comprises employing as the coating an alkali-free glass layer, whereby a reverse leak current at the p-n junction is increased in the irradiation step, and the annealing is carried out under such condition so that the increased reverse leak current is decreased to a predetermined value smaller than the increased value, while the degree of the shortened life time is substantially maintained in the step of the annealing, whereby the reverse leak current is substantially reduced to a value smaller than that measured after the irradiation.

Claim 10

The semiconductor device as defined in claim 7, wherein the glass coating has the following composition: ______________________________________ ZnO 50 to 80% by weight B.sub.2 O.sub.3 5 to 30% by weight SiO.sub.2 1 to 10% by weight PbO up to 10% by weight Sb.sub.2 O.sub.3 up to 5% by weight SnO.sub.2 up to 5% by weight Al.sub.2 O.sub.3 up to 5% by weight ______________________________________ and has a coefficient of linear thermal expansion approximately equal to that of the semiconductor body.

Claim 11

The semiconductor device as defined in claim 7, wherein the glass coating has a linear thermal expansion of not more than 100×10 -7 /°C.