Patent ID: 6399998
Filing Date: 2002-06-04
Classification: H01L

Abstract:
An insulated-gate bipolar switch, comprising:a P layer; a first electrode which contacts said P layer and provides a collector connection for said switch; an Nâˆ’ drift layer on said P layer opposite said collector; a plurality of gates recessed into said Nâˆ’ drift layer, each of said gates arranged in a trench configuration and comprising: a layer of oxide forming the sidewalls and bottom of said trench, and a conductive material within said trench which connects a voltage applied to the top of said trench to said layer of oxide; a second electrode which contacts the conductive material in each of said trenches to provide a gate connection for said switch; a plurality of floating mesas sandwiched between respective pairs of said trench gates, each of said floating mesas having a layer of oxide across its top surface; at least one IGBT structure, each of said at least one IGBT structures comprising: a P base region on said Nâˆ’ drift layer, a P+ region on said P base region which provides an ohmic contact to said P base region, and an N+ region which contacts a portion of said P base region, said P base, P+ and N+ regions sandwiched between a pair of said trench gates and forming a conductive mesa, said P base and N+ regions arranged such that at least one of said trench gates adjacent said conductive mesa contacts said N+ and P base regions; and a third electrode which contacts the P+ ohmic contact and N+ regions of each of said at least one IGBT structures and provides an emitter connection for said switch; each of said conductive mesas having a width defined by the distance between the trench gates adjacent said conductive mesa, the widths of each of said floating mesas being different from the widths of said conductive mesas; said switch structure arranged such that the application of a voltage to said gate connection which is positive with respect to said emitter connection forms inversion channels across said P base regions and accumulation channels in said Nâˆ’ drift layer adjacent to said trench gate bottoms, said inversion channels providing conductive paths between said N+ regions and said Nâˆ’ drift layer that enable electrons to be injected from said N+ regions into said Nâˆ’ drift layer and said switch to be turned on when the voltage across said collector and emitter is sufficiently high and thereby allowing current to flow between said collector and said emitter connections via said IGBT structure, a zero or negative gate voltage eliminating said inversion channels and terminating conduction through the switch.