Early PTS with buffer for channel doping control
A method of performing an early PTS implant and forming a buffer layer under a bulk or fin channel to control doping in the channel and the resulting bulk or fin device are provided. Embodiments include forming a recess in a substrate; forming a PTS layer below a bottom surface of the recess; forming a buffer layer on the bottom surface and on side surfaces of the recess; forming a channel layer on and adjacent to the buffer layer; and annealing the channel, buffer, and PTS layers.
1. A method comprising:
forming a recess in a substrate;
forming a punch through stopper (PTS) layer directly below and aligned with a bottom surface of the recess;
forming a buffer layer on the bottom surface and directly on side surfaces of the recess, with no material between the buffer layer and the side surfaces of the recess, wherein the portion of the buffer layer formed on the bottom surface of the recess is formed directly above and aligned with the PTS layer;
forming a channel layer on and adjacent to the buffer layer; and
annealing the channel, buffer, and PTS layers.
2. The method according to claim 1 , wherein the substrate comprises silicon (Si), silicon germanium (SiGe), or a strain relaxed buffer (SRB).
3. The method according to claim 1 , comprising forming the recess by:
forming a hard-mask over a portion of the substrate; and
etching a remaining portion of the substrate without the hard-mask to a depth of 5 nanometer (nm) to 60 nm.
4. The method according to claim 1 , comprising forming the PTS layer by:
implanting a dopant into the bottom surface of the recess; and
annealing.
5. The method according to claim 1 , further comprising performing a well implant in the bottom surface of the recess after forming the PTS layer, but before forming the buffer layer.
6. The method according to claim 1 , comprising forming the buffer layer of Si, silicon:carbon (Si:C), SiGe, or silicon germanium:carbon (SiGe:C).
7. The method according to claim 6 , comprising forming the buffer layer by:
epitaxial growth.
8. The method according to claim 7 , comprising growing the buffer layer to a thickness of 1 nm to 20 nm.
9. The method according to claim 1 , comprising forming the channel layer of Si, SiGe, or combined group III and group IV elements (III-V).
10. The method according to claim 9 , comprising forming the channel layer by:
epitaxial growth.
11. The method according to claim 10 , comprising growing the channel layer to a thickness of 1 nm to 100 nm.
12. A device comprising:
a substrate having upper and lower surfaces and a recess;
a punch through stopper (PTS) layer and a well formed directly below and aligned with a bottom surface of the recess;
a buffer layer formed directly on side and bottom surfaces of the recess, with no material between the buffer layer and the side surfaces of the recess, wherein the portions of the buffer layer on the bottom surfaces of the recess is formed directly above and aligned with the PTS layer; and
a channel layer formed on and adjacent to the buffer layer, an upper surface of the channel layer is coplanar with the upper surface of the substrate.
13. The device according to claim 12 , wherein the substrate comprises silicon (Si), silicon germanium (SiGe), or a strain relaxed buffer (SRB).
14. The device according to claim 12 , wherein the recess is formed to a depth of 5 nanometer (nm) to 60 nm below the upper surface of the substrate.
15. The device according to claim 12 , wherein the buffer layer comprises Si, silicon/carbon (Si/C), or SiGe.
16. The device according to claim 12 , wherein the buffer layer is formed to a thickness of 1 nanometer (nm) to 20 nm.
17. The device according to claim 12 , wherein the channel layer comprises Si, SiGe, combined group III and group IV elements (III-V).
18. The device according to claim 12 , wherein the channel layer is formed to a thickness of 1 nm to 100 nm.
19. A method comprising:
forming a hard-mask over a portion an upper surface of a substrate comprising silicon (Si), silicon germanium (SiGe), or a strain relaxed buffer (SRB);
recessing a remaining portion of the upper surface of the substrate without the hard-mask;
performing a punch through stopper (PTS) implant in a bottom surface of the recess to form a PTS layer directly below and aligned with the bottom surface of the recess;
performing a well implant in the bottom surface of the recess;
annealing;
growing a buffer layer directly on the bottom surface and side surfaces of the recess, with no material between the buffer layer and the side surfaces of the recess, wherein the portion of the buffer layer on the bottom surface of the recess is formed directly above and aligned with the PTS layer;
growing a channel layer on and adjacent to the buffer layer; and
annealing the channel, buffer, and PTS layers.
20. The method according to claim 19 , comprising forming the buffer layer of Si, silicon:carbon (Si:C), SiGe, silicon germanium:carbon (SiGe:C) and the channel layer of Si, SiGe, or combined group III and group IV elements (III-V).