Integrated circuit with different channel materials for P and N channel transistors and method therefor
A substrate includes a first region and a second region. The first region comprises a III-nitride layer, and the second region comprises a first semiconductor layer. A first transistor (such as an n-type transistor) is formed in and on the III-nitride layer, and a second transistor (such as a p-type transistor) is formed in and on the first semiconductor layer. The III-nitride layer may be indium nitride. In the first region, the substrate may include a second semiconductor layer, a graded transition layer over the second semiconductor layer, and a buffer layer over the transition layer, where the III-nitride layer is over the buffer layer. In the second region, the substrate may include the second semiconductor layer and an insulating layer over the second semiconductor layer, where the first semiconductor layer is over the insulating layer.
1. A method for forming a semiconductor structure, comprising:
providing a substrate having a first semiconductor layer, an insulating layer over the first semiconductor layer, and a second semiconductor layer over the insulating layer, the substrate having a first region and a second region, wherein the first semiconductor layer has a first crystal surface orientation and the second semiconductor layer has a second crystal surface orientation different from the first surface crystal orientation;
forming an opening in the first region extending through the insulating layer and into the first semiconductor layer;
epitaxially growing a transition layer in the opening so that the transition layer has the first crystal surface orientation;
epitaxially growing a buffer layer over the transition layer in the opening so that the transition layer has the first crystal surface orientation;
epitaxially growing a III-nitride layer over the buffer layer so that the transition layer has the first crystal surface orientation;
forming a first transistor in and on the III-nitride layer in the first region; and
forming a second transistor in and on the second semiconductor layer in the second region.
2. The method of claim 1 , wherein the first semiconductor layer comprises silicon, the transition layer comprises graded silicon germanium, and the buffer layer comprises germanium.
3. The method of claim 1 , wherein the second semiconductor layer has higher carrier mobility for p-type transistors than n-type transistors and the III-nitride layer has higher carrier mobility for n-type transistors than p-type transistors.
4. The method of claim 1 , wherein a lattice constant of the buffer layer is within approximately one percent of a lattice constant of the III-nitride layer.
5. The method of claim 1 , further comprising forming a sidewall spacer in the opening before the step of epitaxially growing the transition layer.
6. The method of claim 2 , wherein the transition layer has approximately 0% germanium nearest the first semiconductor layer and approximately 100% germanium nearest the buffer layer.
7. The method of claim 2 , wherein the III-nitride layer comprises indium and nitride.
8. The method of claim 7 , wherein the first transistor is a p-type transistor and the second transistor is an n-type transistor.
9. The method of claim 8 , wherein the first semiconductor layer has higher carrier mobility for p-type transistors than n-type transistors and the III-nitride layer has higher carrier mobility for n-type transistors than p-type transistors.