Method for making a semiconductor structure using silicon germanium
View Patent ↗Silicon carbon is used as a diffusion barrier to germanium so that a silicon layer can be subsequently formed without being contaminated with germanium. This is useful in separating silicon layers from silicon germanium layers in situations in which both silicon and silicon germanium are desired to be present on the same semiconductor device such as for providing different materials for optimizing carrier mobility between N and P channel transistors and for a raised source/drain of silicon in the case of a silicon germanium body.
1. A method of forming a transistor, the method comprising:
forming a first layer including silicon carbon over a material including silicon germanium;
forming a layer including silicon over the first layer including silicon carbon;
forming a gate over the layer including silicon;
forming a gate dielectric between the gate and the layer including silicon; and
removing the material including silicon germanium below the gate after the forming the gate;
filling a material in a location from which the material including silicon germanium was removed;
forming a second recess in the material in the location; and
epitaxially growing semiconductor material, wherein the epitaxially growing includes growing semiconductor material in the second recess;
wherein the first layer including silicon carbon functions as a barrier to germanium diffusion from the material including silicon germanium to the gate dielectric; and
wherein the transistor includes a source/drain region, wherein at least a portion of the source/drain region is located in the semiconductor material epitaxially grown.
2. The method of claim 1 further comprising:
forming the material including silicon germanium over a second layer including silicon carbon
wherein the first and second layers including silicon carbon function as a barrier to germanium diffusion to prevent dilution of germanium concentration in the material including silicon germanium.
3. The method of claim 1 further comprising:
oxidizing at least a portion of the layer including silicon carbon after the removing.
4. The method of claim 1 wherein:
the transistor includes a channel region;
at least a portion of the channel region is located in the layer including silicon.
5. The method of claim 1 further comprising:
forming a recess in the layer including silicon and forming a recess in the first layer including silicon carbon prior to the removing the material.
6. The method of claim 1 wherein the forming the first layer including silicon carbon further includes:
epitaxially growing the layer including silicon carbon on the material including silicon germanium.
7. The method of claim 1 wherein the first layer including silicon carbon has a thickness in the range of 20 Angstroms to 75 Angstroms.
8. The method of claim 1 wherein the removing includes etching the material including silicon germanium with an etchant that is selective with respect to silicon.