Systems and methods for harvesting and integrating nanowires
View Patent ↗The present invention is directed to methods to harvest, integrate and exploit nanomaterials, and particularly elongated nanowire materials. The invention provides methods for harvesting nanowires that include selectively etching a sacrificial layer placed on a nanowire growth substrate to remove nanowires. The invention also provides methods for integrating nanowires into electronic devices that include placing an outer surface of a cylinder in contact with a fluid suspension of nanowires and rolling the nanowire coated cylinder to deposit nanowires onto a surface. Methods are also provided to deposit nanowires using an ink-jet printer or an aperture to align nanowires. Additional aspects of the invention provide methods for preventing gate shorts in nanowire based transistors. Additional methods for harvesting and integrating nanowires are provided.
1. A method of harvesting nanowires, comprising:
providing a population of upstanding core nanowires attached to a surface of a growth substrate;
depositing a first inner shell layer on the population of nanowire cores and overlying the surface of the growth substrate;
depositing a second outer shell layer on the first inner shell layer, wherein the second shell layer is differentially etchable from the first shell layer;
selectively etching at least portions of the second outer shell layer overlying the substrate surface;
selectively etching at least exposed portions of the inner shell layer overlying the substrate surface to expose end portions of the core nanowires in the nanowire population; and
releasing the end portions of the core nanowires to release the nanowires from the growth substrate.
2. The method of claim 1 , wherein the first inner shell layer comprises a dielectric material layer.
3. The method of claim 2 , wherein the dielectric material layer comprises silicon oxide or silicon nitride.
4. The method of claim 3 , wherein the dielectric material layer comprises silicon oxide.
5. The method of claim 2 , wherein the dielectric material layer comprises silicon nitride, Ta2O5, TiO2, ZrO2, HfO2, or Al2O3.
6. The method of claim 4 , wherein the second outer shell layer comprises a conductive material layer.
7. The method of claim 6 , wherein the conductive material layer comprises WN.
8. The method of claim 6 , wherein the conductive material layer comprises W, Pt, or highly doped silicon.
9. The method of claim 6 , wherein the second outer shell layer is deposited by atomic layer deposition on the inner shell layer.
10. The method of claim 6 , wherein selectively etching at least portions of the second outer shell layer overlying the substrate surface comprises using a directional etch step.
11. The method of claim 10 , wherein selectively etching at least exposed portions of the inner shell layer overlying the substrate surface comprises exposing the substrate to a buffered oxide etch vapor or wet solution to remove the exposed oxide layer from the substrate surface and from the exposed end portions on the nanowires.
12. The method of claim 1 , wherein releasing the end portions of the nanowires comprising etching the end portions.