Method of producing insulated gate bipolar tranistor

Claim 1

A method for forming an electrical device comprising a semiconductor substrate of a first conductivity type having disposed thereon a transistor element, said transistor element comprising a layer of a high resistance semiconductor material of a second conductivity type different from said first conductivity type, a base region of said first conductivity type embedded within said layer of high resistance semiconductor material and extending to a first major surface of the transistor element, a high-impurity density region of the first conductivity type embedded within the base region and extending to the first major surface of the transistor element, and a source region of the second conductivity type embedded at the interface between the base region and the high impurity density region and extending to the first major surface of the transistor element, whereby the first major surface of the transistor element has the high impurity density region, surrounded by the source region, surrounded by the base region, surrounded by the high resistance semiconductor material, and the second major surface of the transistor element which is disposed toward the substrate is entirely high resistance semiconductor material, and a gate oxide layer and a polycrystalline semiconductor layer, each disposed over all of the base region and high resistance semiconductor material portions of the first major surface of the transistor element but not over the high impurity density portions of the transistor element, comprising, in sequence, the steps of: (a) sequentially forming a semiconductor layer of the second conductivity type, a gate oxide layer, a polycrystalline semiconductor layer and an insulation layer on a semiconductor substrate of the first conductivity type; (b) removing a part of said insulation layer to form a window through which a portion of said polycrystalline silicon is exposed; (c) selectively removing the exposed portion of the polycrystalline silicon layer to leave a portion of the gate oxide layer exposed, said exposed portion of the gate oxide layer being larger than the window defined by the insulation layer; (d) introducing impurities through the window defined by the insulation layer and the gate oxide layer into the semiconductor layer of the second conductivity type and then treating at high temperature to diffuse the impurities to form a base region within the semiconductor layer of the second type; (e) introducing further impurities suitable for forming the high impurity density region of the first conductivity type through the window defined by the insulating layer and the gate oxide layer to form an undiffused high impurity density region within the base region; (f) removing the insulation layer remaining after stem (b); (g) removing the exposed portion of the gate oxide layer and forming a resist mask over a central part of the undiffused high impurity density region such that a gap exists between the mask and the polycrystalline material; (h) introducing impurities suitable for forming the source region of the second conductivity type through the gap; (i) removing the resist mask; and (j) thermally diffusing the impurities introduced in steps (e) and (h) to form the high impurity density region and the source region.

Claim 2

A method for forming an electrical device comprising a semiconductor substrate of a first conductivity type having disposed thereon a transistor element, said transistor element comprising a layer of a high resistance semiconductor material of a second conductivity type different from said first conductivity type, a base region of said first conductivity type embedded within said layer of high resistance semiconductor material and extending to a first major surface of the transistor element, a high-impurity density region of the first conductivity type embedded within the base region and extending to the first major surface of the transistor element, and a source region of the second conductivity type embedded at the interface between the base region and the high impurity density region and extending to the first major surface of the transistor element, whereby the first major surface of the transistor element has the high impurity density region, surrounded by the source region, surrounded by the base region, surrounded by the high resistance semiconductor material, and the second major surface of the transistor element which is disposed toward the substrate is entirely high resistance semiconductor material, and a gate oxide layer and a polycrystalline semiconductor layer, each disposed over all of the base region and high resistance semiconductor material portions of the first major surface of the transistor element but not over the high impurity density portions of the transistor element, comprising, in sequence, the steps of: (a) sequentially forming a semiconductor layer of the second conductivity type, a gate oxide layer, a polycrystalline semiconductor layer and an insulation layer on a semiconductor substrate of the first conductivity type; (b) removing a part of said insulation layer to form a window through which a portion of said polycrystalline silicon is exposed; (c) selectively removing the exposed portion of the polycrystalline silicon layer to leave a portion of the gate oxide layer exposed, said exposed portion of the gate oxide layer being larger than the window defined by the insulation layer; (d) introducing impurities through the window defined by the insulation layer and the gate oxide layer into the semiconductor layer of the second conductivity type and then treating at high temperature to diffuse the impurities to form a base region within the semiconductor layer of the second type; (e) introducing further impurities suitable for forming the high impurity density region of the first conductivity type through the window defined by the insulating layer and the gate oxide layer to form an undiffused high impurity density region within the base region; (f) removing the insulation layer remaining after stem (b); (g) removing the exposed portion of the gate oxide layer and forming a resist mask over a central part of the undiffused high impurity density region such that a gap exists between the mask and the polycrystalline material; (h) introducing impurities suitable for forming the source region of the second conductivity type through the gap; (i) removing the resist mask; and (j) thermally diffusing the impurities introduced in steps (e) and (h) to form the high impurity density region and the source region.