Method for forming isolation film for semiconductor devices
View Patent ↗An isolation film for semiconductor devices is formed from a pad oxide film and a pad nitride film on a substrate, etching the pad nitride film, the pad oxide film and the substrate to form a trench in an active region of the substrate; forming a sidewall oxide film on the surface of the trench; removing the pad nitride film; forming a linear nitride film on the sidewall oxide film and the pad oxide film; removing a portion of the pad oxide film on the substrate; removing the exposed pad oxide film to expose the field region of the substrate; oxidizing the exposed field region to form an oxide film; removing the sidewall oxide film to expose the active region of the substrate; and forming a silicon epitaxial layer serving as an active layer on the exposed active region of the substrate to the same height as the oxide film.
1. A method for forming an isolation film for semiconductor devices, the method comprising the steps of:
successively forming a pad oxide film and a pad nitride film on a silicon substrate having an active region and a field region;
etching the pad nitride film, the pad oxide film and the silicon substrate to form a trench in the active region of the substrate;
forming a sidewall oxide film on the surface of the trench;
removing the pad nitride film;
forming a linear nitride film on the sidewall oxide film and the pad oxide film;
subjecting the linear nitride film to CMP such that a portion of the pad oxide film on the field region of the substrate is exposed;
removing the exposed pad oxide film to expose the field region of the substrate;
oxidizing the exposed field region of the substrate to form an oxide film to the same depth as the bottom of the trench;
removing the linear nitride film;
removing the sidewall oxide film to expose the active region of the substrate; and
forming a silicon epitaxial layer serving as an active layer on the exposed active region of the substrate to the same height as the oxide film.
2. The method of claim 1 , wherein the step of etching the pad nitride film is conducted using a CHF 3 /CF 4 /O 2 /Ar mixture plasma.
3. The method of claim 1 , wherein the step of forming the trench is conducted using a Cl 2 /HBr/He—O 2 /Ar mixture plasma.
4. The method of claim 3 , wherein the mixture plasma contains O 2 in a substitute for He—O 2 .
5. The method of claim 3 , wherein the step of forming the trench is conducted using a Cl 2 /O 2 /Ar mixture plasma.
6. The method of claim 3 , wherein the mixture plasma additionally contains N 2 .
7. The method of claim 1 , wherein the forming of removing the pad nitride film is conducted by a down flow method using CF 4 and O 2 gases.
8. The method of claim 7 , wherein the down flow method is conducted at the etching selectivity of the pad nitride film to the pad oxide film of more than 12:1.
9. The method of claim 1 , wherein the step of removing the pad nitride film is conducted by a wet etching method using a H 3 PO 4 solution.
10. The method of claim 1 , wherein the step of removing the sidewall oxide film is conducted by a wet etching manner a BOE- or HF-based solution.
11. The method of claim 1 , wherein the steps of removing the pad oxide film and the sidewall oxide film are conducted by activated plasma.
12. The method of claim 1 , wherein the step of forming the oxide film is conducted in such a manner that the oxide film is formed at a ratio of 60% in the upper direction of the silicon substrate surface to 40% in the lower direction of the silicon substrate surface.
13. The method of claim 1 , wherein the step of removing the linear nitride film is conducted by a down flow method using CF 4 and O 2 gases, or a wet etching method using a H 3 PO 4 solution.