Semiconductor device having rapid removal of majority carriers from an active base region thereof at device turn-off and method of fabricating this device

Claim 1

A semiconductor device having the feature of removal of majority carriers from an active base region thereof during turn-off of the device, characterized by a) a semiconductor substrate (31; 54; 82) comprising at least in part bulk type material; said substrate further comprising first and second regions (34, 35; 57, 58; 75, 77; 83); said first region being doped to one conductivity type and said second region being doped to the opposite conductivity type; at least a major portion of said first region being doped to a first concentration; said first concentration being equal to at least about 5 x 10 17 dopant atoms per cubic centimeter; said second region being doped to a second concentration which is at least as high as said first concentration; said substrate having a first surface comprising in part a surface of said second region and in further part a surface of said first region; b) a first electrode (42; 72; 84) electrically connected to a second surface of said substrate comprising a further surface of said first region; c) an epitaxial layer (32; 55) deposited on said substrate first surface and comprising at least third and fourth regions (36, 40; 60, 61; 78; 81); said third region separating said substrate second region from said epitaxial layer fourth region; said third region being doped to said opposite conductivity type and said fourth region being doped to said one conductivity type; at least a major portion of said third region being doped to a third concentration substantially lower than said first concentration; a major portion of said fourth region being doped to a fourth concentration substantially higher than said third concentration; and d) a second electrode (44; 71; 85) electrically connected to at least a surface of said epitaxial layer fourth region.

Claim 6

The device according to one of the preceding claims 1 to 4, characterized in that a minor portion (81b) of said third region (81) adjoining said substrate first surface and separating a third region major portion (81a) from said substrate (82) is doped to a concentration substantially higher than said third concentration but lower than said first concentration (Fig. 7; Fig. 8).

Claim 7

The device according to one of the preceding claims 1 to 5, characterized by e) a fifth region (62) included in said epitaxial layer (55); said fifth region adjoining said third and fourth regions (60, 61), separated from said substrate (54) by said third region, and having a free surface; a first junction (66) between said third and fifth regions having a portion terminating at an exterior surface of said epitaxial layer; and f) a third electrode (68) separated from said epitaxial layer by an insulative layer (70), said third electrode covering an area on said epitaxial layer including at least part of said fifth region free surface from a location proximate said terminated portion of said first junction and extending towards said second electrode (71); said third electrode, said insulative layer, and said fifth region being so constructed and arranged that said fifth region completes a current path for majority carriers in said third region with current path connects together said third region and said second electrode upon suitable biasing of said third electrode (Fig. 5 to 8).

Claim 10

The device according to one of the preceding claims 6 to 8, characterized by a sixth region (63) doped to said opposite conductivity type, adjoining said fourth and fifth regions (61, 62), separated from said third region (60) by said fourth and fifth regions, and having a sixth doping concentration substantially higher than said fourth concentration; a second junction (67) between said fifth and sixth regions having a portion terminating at an exterior surface of said epitaxial layer (55); and wherein said area on said epitaxial layer covered by said third electrode (68) extends from said location to a location proximate said terminated portion of said second junction, whereby said sixth region is in said current path connecting together said third region and said second electrode (71) (Fig. 5 to 8).

Claim 11

The device according to one of the preceding claims 1 to 5, characterized in that e ) said epitaxial layer (32) comprises a fifth region (41), said fifth region being doped to said opposite conductivity type, adjoining said fourth region (40), being separated from said third region (38) by said fourth region, and having a fifth doping concentration substantially higher than said fourth concentration; and that f) said second electrode (44) is electrically connected to said epitaxial layer fifth region (Fig. 3).

Claim 13

The device according to one of the preceding claims 1 to 11, characterized in that said one conductivity type is P-type and second opposite conductivity type is N-type.

Claim 14

A method of fabricating a semiconductor device having the feature of rapid removal of majority carriers from an active base region thereof, characterized by steps of: a) providing a semiconductor substrate comprising a bulk wafer doped to one conductivity type, and having a first doping concentration equal to at least about 5x10 1 dopant atoms per cubic centimeter; b) introducing through part of a first principal surface of said substrate at least one first region of said opposite conductivity type; said first region having a second doping concentration which is at least as high as said first concentration; and c) epitaxially growing a layer of semiconductor material of said opposite conductivity type upon said substrate principal surface; a major portion of said epitaxial layer having a third doping concentration substantially lower than said first concentration.

Claim 15

A method of fabricating a semiconductor device having the feature of rapid removal of majority carriers from an active base region thereof, characterized by steps of: a) providing a semiconductor substrate comprising a bulk wafer doped to one conductivity type, and having a first doping concentration equal to at least about 5x10 1 dopant atoms per cubic centimeter; b) introducing through part of a first principal surface of said substrate at least one first region of said opposite conductivity type; said first region having a second doping concentration which is at least as high as said first concentration; and c) epitaxially growing a layer of semiconductor material of said opposite conductivity type upon said substrate principal surface; a major portion of said epitaxial layer having a third doping concentration substantially lower than said first concentration.

Claim 20

The method according to one of the preceding claims 15 to 17, characterized in that said step of introducing said second region comprises a diffusion.

Claim 22

The method according to one of the claims 15 to 17, characterized in that said step of introducing said second region comprises multiple doping ion implanation.

Claim 23

The method according to one of the claims 13 to 20, characterized in that said step of introducing said first region comprises a planar diffusion.

Claim 25

The method according to one of the claims 13 to 20, characterized in that said step of introducing said first region comprises multiple doping ion implanation.

Claim 26

The method according to one of the claims 13 to 23, characterized in that said one conductivity type is P-type and said opposite conductivity type is N-type.