Semiconductor die, integrated circuits and driver circuits, and methods of maufacturing the same
A semiconductor die is disclosed comprising a lateral semiconductor device on an upper major surface of a substrate, the integrated circuit comprising a silicon layer over the substrate, a recess in the silicon layer, a layer of LOCOS silicon oxide within the recess and having a grown upper surface which is coplanar with the surface of an un-recessed portion of the silicon layer, wherein the silicon layer beneath the recess has a non-uniform lateral doping profile, and is comprised in a drift region of the lateral semiconductor device. A method of making such a die is also disclosed, as is an integrated circuit and a driver circuit.
1. A semiconductor die comprising a lateral semiconductor device on an upper major surface of a substrate, the semiconductor die further comprising:
a silicon layer over the substrate having a conductivity type,
a recess in the silicon layer,
a layer of LOCOS silicon oxide within the recess and having a grown upper surface which is coplanar with the surface of an un-recessed portion of the silicon layer,
wherein a portion of the silicon layer is beneath the recess and has a non-uniform quadratic lateral doping concentration profile of the conductivity type, and is comprised in a drift region of the lateral semiconductor device; and
wherein a thickness of the layer of LOCOS silicon oxide within the recess is greater than a thickness of the silicon layer beneath the recess.
2. A semiconductor die according to claim 1 , wherein the lateral semiconductor device is a high voltage device having a lateral high voltage extension and wherein the silicon layer beneath the recess comprises the high voltage extension.
3. A semiconductor die according to claim 1 , wherein the recess in the silicon layer has a tapered edge.
4. A semiconductor die according to claim 1 , wherein the LOCOS silicon oxide at the tapered edge has a birds-beak profile.
5. A semiconductor die according to claim 1 ,
further comprising a second LOCOS silicon oxide layer outside of the recess and coupled to the layer of LOCOS silicon oxide within the recess,
wherein the second LOCOS silicon oxide layer has a thickness which is less than that of the LOCOS silicon oxide layer within the recess.
6. A semiconductor die according to claim 5 ,
further comprising a polysilicon field plate extending over the second LOCOS silicon oxide layer outside of the recess,
wherein the polysilicon field plate does not extend over the LOCOS silicon oxide layer within the recess.
7. A semiconductor die according to claim 1 , wherein the silicon layer over the substrate is spaced apart from the substrate by a buried oxide layer.
8. A semiconductor die according to claim 1 , wherein the lateral semiconductor device is a one of the group consisting of: a junction field effect transistor, an insulated gate field effect transistor, an insulated gate bipolar transistor, and a diode.
9. A semiconductor die according to claim 1 , wherein the lateral semiconductor device is a bipolar device, and further comprising one or more CMOS devices.
10. A semiconductor die according to claim 1 , wherein the recess in the silicon layer extends for a part of distance between two main contacts of the lateral semiconductor device.
11. A semiconductor die according to claim 1 , wherein the lateral semiconductor device comprises a channel, the channel having a minimum channel length of no more than 250 nm.
12. An integrated circuit comprising a silicon die as claimed in claim 1 .
13. A driver circuit for at least one of a compact fluorescent lamp or a light emitting diode lamp, comprising at least one semiconductor die according to claim 1 .
14. The semiconductor die of claim 1 ,
wherein the semiconductor die is configured to be fabricated using a Bipolar CMOS DMOS (BCD) process.