On-chip DC-DC power converters with fully integrated GaN power switches, silicon CMOS transistors and magnetic inductors
Fully integrated, on-chip DC-DC power converters are provided. In one aspect, a DC-DC power converter includes: a SOI wafer having a SOI layer separated from a substrate by a buried insulator, wherein the SOI layer and the buried insulator are selectively removed from at least one first portion of the SOI wafer, and wherein the SOI layer and the buried insulator remain present in at least one second portion of the SOI wafer; at least one GaN transistor formed on the substrate in the first portion of the SOI wafer; at least one CMOS transistor formed on the SOI layer in the second portion of the SOI wafer; a dielectric covering the GaN and CMOS transistors; and at least one magnetic inductor formed on the dielectric. A method of forming a fully integrated DC-DC power converter is also provided.
1. A DC-DC power converter, comprising:
a silicon-on-insulator (SOI) wafer having a SOI layer separated from a substrate by a buried insulator, wherein the SOI layer and the buried insulator are selectively removed from at least one first portion of the SOI wafer, and wherein the SOI layer and the buried insulator remain present in at least one second portion of the SOI wafer;
at least one gallium nitride (GaN) transistor formed on the substrate in the at least one first portion of the SOI wafer;
at least one complementary metal-oxide semiconductor (CMOS) transistor, formed on the SOI layer in the at least one second portion of the SOI wafer, connected to a gate of the GaN transistor;
a dielectric covering the GaN and CMOS transistors;
at least one magnetic inductor formed on the dielectric; and
metal wiring in the dielectric directly connecting a drain of the GaN transistor with the magnetic inductor.
2. The DC-DC power converter of claim 1 , wherein the buried insulator is an oxide.
3. The DC-DC power converter of claim 1 , wherein the substrate comprises a material selected from the group consisting of: silicon (111), silicon carbide, sapphire, and combinations thereof.
4. The DC-DC power converter of claim 1 , wherein the magnetic inductor is a closed-yoke magnetic inductor.
5. The DC-DC power converter of claim 1 , wherein the GaN transistor comprises:
a first active material on the substrate; and
a second active material on the first active material, wherein the second active material has a higher band gap than the first active material.
6. The DC-DC power converter of claim 5 , wherein the first active material comprises GaN.
7. The DC-DC power converter of claim 5 , wherein the second active material comprises aluminum-gallium-nitride (AlGaN).
8. The DC-DC power converter of claim 5 , wherein a top surface of the second active material is coplanar with a top surface of the SOI layer.
9. A method of forming a DC-DC power converter, the method comprising:
providing a SOI wafer having a SOI layer separated from a substrate by a buried insulator;
selectively removing the SOI layer and the buried insulator from at least one first portion of the SOI wafer such that the SOI layer and the buried insulator remain present in at least one second portion of the SOI wafer;
forming at least one GaN transistor on the substrate in the at least one first portion of the SOI wafer;
forming at least one CMOS transistor on the SOI layer in the at least one second portion of the SOI wafer connected to a gate of the GaN transistor;
depositing a dielectric that covers the GaN and CMOS transistors;
forming at least one magnetic inductor on the dielectric; and
forming metal wiring in the dielectric that directly connects a drain of the GaN transistor with the magnetic inductor.
10. The method of claim 9 , further comprising:
forming a mask that covers the GaN transistor prior to forming the CMOS transistor.
11. The method of claim 9 , wherein the substrate comprises a material selected from the group consisting of: silicon (111), silicon carbide, sapphire, and combinations thereof.
12. The method of claim 9 , wherein the magnetic inductor is a closed-yoke magnetic inductor.
13. The method of claim 9 , wherein selectively removing the SOI layer and the buried insulator from the at least one first portion of the SOI wafer comprises:
forming a mask that covers only the at least one second portion of the SOI wafer; and
etching the SOI wafer using the mask to selectively remove the SOI layer and the buried insulator from the at least one first portion of the SOI wafer.
14. The method of claim 13 , wherein the etching comprises: i) a first etch to selectively remove the SOI layer from the at least one first portion of the SOI wafer, and ii) a second etch to selectively remove the buried insulator from the at least one first portion of the SOI wafer, and wherein the substrate acts as an etch stop for the second etch.
15. The method of claim 9 , further comprising:
depositing a first active material on the substrate; and
depositing a second active material on the first active material, wherein the second active material has a higher band gap than the first active material.
16. The method of claim 15 , wherein the first active material comprises GaN.
17. The method of claim 15 , wherein the second active material comprises AlGaN.
18. The method of claim 15 , wherein a top surface of the second active material is coplanar with a top surface of the SOI layer.