Method and system for etch depth control in III-V semiconductor devices
A method of manufacturing a vertical FET device includes providing a semiconductor substrate structure including a marker layer; forming a hardmask layer coupled to the semiconductor substrate structure, wherein the hardmask layer comprises a set of openings operable to expose an upper surface portion of the semiconductor substrate structure; etching the upper surface portion of the semiconductor substrate structure to form a plurality of fins; etching at least a portion of the marker layer; detecting the etching of the at least a portion of the marker layer; epitaxially growing a semiconductor layer in recess regions disposed between adjacent fins of the plurality of fins; forming a source metal layer on each of the plurality of fins; and forming a gate metal layer coupled to the semiconductor layer.
1. A field-effect transistor (FET) device, comprising:
a semiconductor substrate;
a first semiconductor layer coupled to the semiconductor substrate, wherein the first semiconductor layer is characterized by a first conductivity type and a first dopant concentration;
a second semiconductor layer coupled to the first semiconductor layer, wherein the second semiconductor layer is characterized by the first conductivity type;
a marker layer coupled to the second semiconductor layer;
a third semiconductor layer coupled to the marker layer, wherein the third semiconductor layer is characterized by the first conductivity type;
a plurality of fins coupled to the third semiconductor layer, wherein each of the plurality of fins is separated by one of a plurality of recess regions extending to the second semiconductor layer, wherein the each of the plurality of fins is characterized by the first conductivity type and a second dopant concentration;
a fifth semiconductor layer epitaxially grown within the plurality of recess regions, wherein the fifth semiconductor layer is characterized by a second conductivity type opposite to the first conductivity type;
a source metal layer coupled to each of the plurality of fins; and
a gate metal layer coupled to the fifth semiconductor layer.
2. The FET device of claim 1 wherein the second semiconductor layer is characterized by a first graded dopant concentration that is a gradient linearly increased from the first dopant concentration to a third dopant concentration, wherein the third dopant concentration is greater than the first dopant concentration and less than the second dopant concentration.
3. The FET device of claim 1 wherein the third semiconductor layer is characterized by a second graded dopant concentration that is a gradient linearly increased from a third dopant concentration to the second dopant concentration, wherein the third dopant concentration is greater than the first dopant concentration and less than the second dopant concentration.
4. The FET device of claim 1 wherein the second dopant concentration is greater than the first dopant concentration.
5. The FET device of claim 1 wherein the marker layer comprises silicon or AlGaN.
6. The FET device of claim 1 wherein the marker layer has a thickness in a range of 5-10 nm.
7. The FET device of claim 1 wherein the semiconductor substrate comprises III-nitride compounds.
8. The FET device of claim 1 wherein a dopant concentration of semiconductor substrate ranges from about 5×10 17 atoms/cm 3 to about 1×10 19 atoms/cm 3 .
9. The FET device of claim 1 wherein the third semiconductor layer is characterized by a uniform dopant concentration greater than the first dopant concentration and less than the second dopant concentration.
10. The FET device of claim 1 wherein each of the plurality of fins has a thickness of about 0.8 μm and a width of about 0.2 μm.
11. The FET device of claim 1 wherein the source metal layer comprises a refractory metal, a refractory metal compound, or a refractory metal alloy.
12. The FET device of claim 1 wherein the gate metal layer comprises nickel, gold, molybdenum, platinum, palladium, silver, or combinations thereof.
13. The FET device of claim 1 wherein the first semiconductor layer is characterized by a thickness between 5 μm and 12 μm.
14. The FET device of claim 1 , wherein the marker layer is disposed between the second semiconductor layer and the third semiconductor layer.
15. The FET device of claim 1 , wherein:
the source metal layer is formed on one end of each of the plurality of fins; and
the marker layer is disposed opposite the source metal layer.
16. The FET device of claim 15 , wherein the source metal layer and the marker layer are separated by the third semiconductor layer and the plurality of fins.
17. The FET device of claim 1 , wherein the third semiconductor layer and the second semiconductor layer are separated by the marker layer.
18. The FET device of claim 1 , wherein portions of the marker layer disposed beneath the plurality of fins are segmented by the plurality of recess regions.