Method of forming an element isolation film of a semiconductor device
View Patent ↗Disclosed herein is a method of forming an element isolation film of a semiconductor device. An aluminum oxide film of a high wet etch rate is used as a pad oxide film, a trench is formed, and top and bottom edges of the trench is made rounded while removing some of the aluminum oxide film by a cleaning process. It is thus possible to make the top and bottom edges of the trench rounded without using polymer. It is also possible to minimize generation of a moat due to a step between a field region and an active region in a cleaning process before a gate oxide film is formed.
1. A method of forming an element isolation film of a semiconductor device, the method comprising:
(a) forming an aluminum oxide film for a pad oxide film on a semiconductor substrate by performing Atomic Layer Deposition (ALD) and forming a pad nitride film on the aluminum oxide film;
(b) etching a predetermined region of the pad nitride film and the pad oxide film and then etching the semiconductor substrate to form a trench;
(c) performing a cleaning process to make top and bottom edges of the trench rounded and to remove a portion of the pad oxide film under the pad nitride film;
(d) forming an oxide film on an entire surface so that the trench is buried; and,
(e) polishing the oxide film and then removing the oxide film, the pad nitride film and the pad oxide film.
2. The method of claim 1 , wherein the pad nitride film is formed by LPCVD through thermal decomposition of SiH 2 Cl 2 and NH 3 .
3. The method of claim 1 , wherein the cleaning process is performed by selectively using NH 4 OH, BOE or HF.
4. The method of claim 1 , further comprising forming a wall oxide film on the trench and then forming a liner insulating film on the entire surface.
5. The method of claim 4 , wherein the liner insulating film is formed using a HTO oxide film, a nitride film, or a multi-layer of the HTO oxide film and the nitride film.
6. The method of claim 1 , wherein the oxide film is formed by HDP or LPCVD.
7. The method of claim 1 , wherein the oxide film and the pad nitride film are removed by a wet etch process.
8. The method of claim 7 , wherein the wet etch process is performed using a HF-containing solution or a H 3 PO 4 -based solution.
9. The method of claim 1 , wherein the pad oxide film is removed by a cleaning process using a NH 4 OH solution or a mixing solution of HF and NH 4 OH.
10. The method of claim 4 , wherein the wall oxide film is formed on the sidewall and bottom of the trench as well as between the pad nitride film and the semiconductor substrate of top corners of the trench.