Methods of selective deposition of fine particles onto selected regions of a substrate
View Patent ↗A method for depositing fine particles from a suspension on selected regions of a substrate is disclosed. The particles are deposited on selected regions of a clean hydrophobic semiconductor surface that are surrounded by a wetting boundary which includes a mesa formed by etching through a silicon-on-insulator (SOI) film and an underlying buried oxide of an SOI substrate. The process is well suited for the growth of semiconductor nanowires that nucleates from fine particle used as a catalyst.
1. A method of depositing fine particles on selected regions of a substrate comprising:
providing a semiconductor substrate having selected regions bounded by a wetting boundary located within said semiconductor substrate;
rendering an upper surface of said semiconductor substrate hydrophobic and removing native oxide from said upper surface of said semiconductor substrate to provide a bare upper surface;
dispensing a suspension containing fine particles directly on said bare upper surface of said semiconductor substrate;
removing said suspension from said upper surface of said semiconductor that is not bounded by said wetting boundary, while retaining said suspension only in said selected regions of said semiconductor substrate that are bounded by said wetting boundary; and
drying said semiconductor substrate, wherein during said drying said fine particles deposit only on said regions of said semiconductor substrate that are bounded by said wetting boundary.
2. The method of claim 1 wherein said wetting boundary is formed by providing an oxide filled trench surrounding said selected regions.
3. The method of claim 1 wherein said semiconductor substrate is a bulk semiconductor material.
4. The method of claim 1 wherein said rendering the upper surface of said semiconductor substrate hydrophobic and removing native oxide from said upper surface of said semiconductor substrate comprises contacting the substrate with dilute HF.
5. The method of claim 1 wherein removing said suspension from said upper surface of said semiconductor that is not bounded by said wetting boundary, while retaining said suspension only in said selected regions of said semiconductor substrate that are bounded by said wetting boundary comprises spinning.
6. The method of claim 1 wherein said drying comprises evaporation.
7. The method of claim 1 further comprising growing nanowires from said deposited fine particles.
8. The method of claim 1 wherein said deposited fine particles are electrically charged.
9. The method of claim 1 wherein said deposited fine particles are metal particles.
10. The method of claim 9 wherein said metal particles comprise Au, Ag, Pt, Fe, Co, Pd or iron oxide.
11. The method of claim 1 wherein said dispensing a suspension containing fine particles is performed in the absence of a mask.
12. The method of claim 1 wherein said suspension is aqueous.
13. The method of claim 1 wherein said bare upper surface of said semiconductor substrate is hydrogen-terminated.