Semiconductor device and method with greater epitaxial growth on 110 crystal plane
A semiconductor processing method is provided which promotes greater growth on <110> crystallographic planes than on other crystallographic planes. Growth rates with the process can be reversed compared to typical epitaxial growth processes such that the highest rate of growth occurs on <110> crystallographic planes and the least amount of growth occurs on <100> crystallographic planes. The process can be applied to form embedded stressor regions in planar field effect transistors, and the process can be used to grow semiconductor layers on exposed wall surfaces of adjacent fins in source-drain regions of finFETs to fill spaces between the fins.
1. A semiconductor processing method, comprising:
epitaxially growing a semiconductor layer on a first surface of a first semiconductor region, the first surface oriented in a 110> crystallographic plane of the first semiconductor region, and the first surface extending in direction away from a second surface oriented in a 100> crystallographic plane of the first semiconductor region, the epitaxially growing performed under conditions which promote higher growth rate on the 110> crystallographic plane than on the 100> crystallographic plane so as to grow the semiconductor layer on the first surface at a location spaced from the second surface to a first thickness in a first direction normal to the first surface and to a second thickness less than the first thickness on the second surface at a location spaced from the first surface, the second thickness being in a second direction normal to the second surface; and
wherein the first surface is an interior sidewall of a trench formed in the first semiconductor region and the second surface is a lower interior surface of the trench.
2. The method of claim 1 , wherein the first thickness of the semiconductor layer is at least five times greater than the second thickness.
3. The method of claim 1 , wherein the step of epitaxially growing the semiconductor layer includes epitaxially growing a semiconductor alloy material onto at least the first surface.
4. The method of claim 1 , wherein the step of epitaxially growing the semiconductor layer includes in situ doping the semiconductor layer with at least one of carbon and boron.
5. The method of claim 1 , wherein the step of epitaxially growing the semiconductor layer forms an undoped semiconductor layer.
6. The method of claim 5 , further comprising epitaxially growing a second semiconductor layer overlying a surface of the undoped semiconductor layer and overlying the first semiconductor region.
7. The method of claim 6 , further comprising annealing to cause dopant to diffuse between the first semiconductor region and the second semiconductor layer to electrically link up the first semiconductor region and second semiconductor layer.
8. The method of claim 1 , wherein the semiconductor layer is a first semiconductor layer, the method further comprising epitaxially growing a second semiconductor layer overlying a surface of the first semiconductor layer, the second semiconductor layer being configured to apply a stress to the first semiconductor region and being more heavily doped than the first semiconductor layer.
9. The method of claim 1 , wherein the first surface is an upwardly extending surface of a fin of the first semiconductor region which extends upwardly away from a surface of a buried oxide (BOX) layer.
10. The method of claim 9 , wherein the fin is a first fin and the first semiconductor region has a plurality of fins including the first fin and a second fin adjacent to the first fin, the second fin having an upwardly extending first surface facing the first surface, wherein the epitaxially growing simultaneously grows the semiconductor layer on the first surface of the second fin.
11. The method of claim 10 , wherein the epitaxially growing is performed so as to fill a space defined by the first surfaces of the first and second fins.
12. The method of claim 11 , wherein the epitaxially growing is performed such that the thickness of the semiconductor layer in the first direction on the first surfaces of the first and second fins is uniform irrespective of distance along each first surface from the second surface.
13. The method of claim 12 , wherein said epitaxially growing is performed in a manner which produces no void larger than 1 nanometer in dimension in any direction.
14. The method of claim 1 , wherein the step of epitaxially growing the semiconductor layer is performed at a pressure greater than 150 torr.
15. The method of claim 14 , wherein the step of epitaxially growing the semiconductor layer is performed at a pressure between 150 and 600 torr.
16. The method of claim 15 , wherein the step of epitaxially growing the semiconductor layer is performed at a pressure between 200 and 400 torr.
17. A method of fabricating a transistor, comprising:
epitaxially growing a semiconductor layer of semiconductor material on an interior sidewall of a trench formed in a first semiconductor region, the interior sidewall oriented in a <110> crystallographic plane of the first semiconductor region, and the interior sidewall extending in an upward direction away from a lower interior surface of the trench oriented in a <100> crystallographic plane of the first semiconductor region, the epitaxially growing performed under conditions which promote higher growth rate on the <110> crystallographic plane than on the <100> crystallographic plane so as to grow the semiconductor layer on the interior sidewall at a location spaced from the lower interior surface to a first thickness in a first direction normal to the interior sidewall and to a second thickness less than the first thickness on the second surface at a location spaced from the first surface, the second thickness being in a second direction normal to the second surface, wherein the step of epitaxially growing the semiconductor layer includes epitaxially growing a semiconductor alloy material overlying at least the interior sidewall of the trench, the semiconductor alloy material including an alloy of a semiconductor material of the first semiconductor region with at least one other semiconductor material; and
epitaxially growing a second semiconductor region on a surface of the semiconductor layer by epitaxially growing a semiconductor alloy material overlying the lower interior surface and the interior sidewall of the trench,
wherein the second semiconductor region is more heavily doped than the semiconductor layer and at least the second semiconductor region is configured to apply a stress to the first semiconductor region, at least one of a source region or a drain region of a transistor is disposed at least partly within the second semiconductor region, and a channel region of the transistor is disposed at least partly within the first semiconductor region.
18. The method of claim 17 , wherein the step of epitaxially growing the semiconductor layer is performed at a pressure greater than 150 torr.
19. The method of claim 17 , wherein the step of epitaxially growing the semiconductor layer is performed at a pressure between 150 and 600 torr.
20. The method of claim 17 , wherein the first thickness of the semiconductor layer is at least five times greater than the second thickness.
21. The method of claim 17 , wherein the step of epitaxially growing the semiconductor layer forms an undoped semiconductor layer, the method further comprising epitaxially growing a second semiconductor layer overlying a surface of the undoped semiconductor layer and overlying the first semiconductor region.
22. The method of claim 21 , further comprising annealing to cause dopant to diffuse between the first semiconductor region and the second semiconductor layer to electrically link up the first semiconductor region and the second semiconductor layer.