Nanowire semiconductor device structure and method of manufacturing
A nanowire comprises a source region, a drain region and a channel region. The source region is modified to reduce the lifetime of minority carriers within the source region. In an embodiment the modification may be performed by implanting either amorphizing dopants or lifetime reducing dopants. Alternatively, the source may be epitaxially grown with a different materials or process conditions to reduce the lifetime of minority carriers within the source region.
1. A method of manufacturing a semiconductor device, the method comprising:
forming a nanowire over a substrate, wherein the nanowire comprises a channel;
implanting a first dopant into the nanowire to form a source and a drain in the nanowire, the channel disposed between the source and the drain, wherein the source has a first conductivity type and the drain has the first conductivity type;
covering a portion of the drain; and
implanting a first minority carrier lifetime reducing dopant into the source after the covering the portion of the drain, the first minority carrier lifetime reducing dopant different from the first dopant, wherein the first minority carrier lifetime reducing dopant is substantially confined to the source, and wherein the channel is substantially free of the first minority carrier lifetime reducing dopant.
2. The method of claim 1 , wherein the implanting the first minority carrier lifetime reducing dopant further comprises implanting an amorphizing dopant into the source.
3. The method of claim 2 , further comprising annealing the source to recrystallize the source into a polycrystalline material.
4. The method of claim 1 , wherein the implanting the first minority carrier lifetime reducing dopants implants the first minority carrier lifetime reducing dopants at a non-perpendicular angle.
5. The method of claim 1 , wherein the first minority carrier lifetime reducing dopants directly reduce a lifetime of minority carriers within the source.
6. The method of claim 1 , wherein the nanowire has a longitudinal axis parallel with the substrate.
7. The method of claim 1 , wherein the nanowire has a longitudinal axis perpendicular with the substrate.
8. A method of manufacturing a semiconductor device, the method comprising:
forming a source region, a drain region, and a channel region within a nanowire, wherein the source region has a first conductivity type and the drain region has the first conductivity type;
forming a first spacer on the nanowire, the first spacer covering a portion of the source region;
forming a second spacer on the nanowire, the second spacer covering a portion of the drain region; and
modifying the source region and the drain region to reduce a minority carrier lifetime within the source region and the drain region using a first modification process, wherein the source region and the drain region are part of a MOSFET, and wherein parameters of the first modification process are chosen to avoid modifying portions of the channel region adjacent the source region and portions of the drain region under the second spacer.
9. The method of claim 8 , wherein the first modification process comprises implanting dopants into the source region.
10. The method of claim 9 , wherein the dopants are amorphizing dopants.
11. The method of claim 9 , wherein the dopants directly reduce a lifetime of minority carriers.
12. The method of claim 8 , wherein the source region comprises a first semiconductor material and modifying the source region further comprises:
removing a portion of the first semiconductor material; and
growing a second semiconductor material to replace the first semiconductor material.
13. The method of claim 12 , wherein there is a lattice mismatch between the first semiconductor material and the second semiconductor material.
14. The method of claim 12 , wherein the channel region comprises a third semiconductor material and the second semiconductor material has a defect concentration that is larger than the third semiconductor material.
15. A semiconductor device comprising:
a nanowire with a source region, a drain region, and a channel region between the source region and the drain region, wherein the source region has a first conductivity type and the drain region has the first conductivity type, wherein the channel region is part of a MOSFET; and
first dopants within and throughout the source region, wherein the first dopants are minority carrier lifetime reducing dopants and have a different concentration within the source region than within the drain region, wherein the junction between the source region and the channel region is substantially free of the first dopants, wherein the first dopants are one of nickel, cobalt, titanium, tantalum, oxygen, magnesium, or iron.
16. The semiconductor device of claim 15 , wherein the source region comprises a polycrystalline material.
17. The semiconductor device of claim 15 , wherein the first dopants directly reduce a lifetime of minority carriers within the source region.
18. The semiconductor device of claim 15 , wherein the source region has a different lattice constant than the channel region.
19. The semiconductor device of claim 15 , wherein the first dopants are offset from the channel region.
20. The semiconductor device of claim 19 , wherein the offset is less than about 10 nm.