Method for forming isolation layer in semiconductor memory device
View Patent ↗Disclosed herein is a method for forming an isolation film of a semiconductor memory device. According to the disclosure, in a pre-treatment cleaning process performed before a tunnel oxide film is formed, a SC-1 cleaning process is performed at a temperature ranging from 60° C. to 70° C. Therefore, oxide films in a cell region and a peripheral region are recessed even in the SC-1 cleaning process as well as a DHF cleaning process. A DHF cleaning time can be thus reduced. Accordingly, the method can minimize loss of a silicon substrate by DHF and can thus control the depth of a moat.
1. A method for forming an isolation film, comprising the steps of:
providing a semiconductor substrate in which a pad oxide film is formed;
depositing a pad nitride film on the pad oxide film;
etching the pad nitride film, the pad oxide film and a portion of the semiconductor substrate to form trenches;
depositing an insulating film to bury the trenches;
polishing the insulating film;
stripping the pad nitride film; and,
performing a cleaning process using a diluted HF (DHF) or Buffered Oxide Etchant (BOE) and a Standard Clean-1 (SC-1) cleaning process to strip the pad oxide film, wherein the SC-1 cleaning process is performed at a temperature where the pad oxide film is recessed.
2. The method of claim 1 , further comprising performing the SC-1 cleaning process at a temperature ranging from 60° C. to 70° C.
3. The method of claim 1 , further comprising performing the DHF cleaning process, wherein the DHF is a HF solution in which H 2 O is diluted in the ratio of 50:1.
4. The method of claim 1 , further comprising performing the DHF cleaning process while the pad oxide film formed in a high voltage region of the semiconductor substrate is recessed ½ to ¾ of the entire etch target of the pre-treatment cleaning process.
5. The method of claim 4 , further comprising performing the DHF cleaning process, wherein DHF is a HF solution in which H 2 O is diluted in the ratio of 50:1.
6. The method of claim 1 , further comprising performing the DHF cleaning process for 30 to 100 seconds.
7. The method of claim 6 , further comprising performing the DHF cleaning process, wherein DHF is a HF solution in which H 2 O is diluted in the ratio of 50:1.
8. The method of claim 1 , further comprising performing the SC-1 cleaning process while the pad oxide film formed in a high voltage region of the semiconductor substrate is recessed ¼ to ½ of the entire etch target of the pre-treatment cleaning process.
9. The method of claim 1 , further comprising performing the SC-1 cleaning process for 1 to 10 minutes.
10. The method of claim 1 , wherein the pad oxide film is formed more thickly in a high voltage region of a peripheral region than in a cell region of the semiconductor substrate.
11. The method of claim 10 , wherein the pad oxide film formed in the high voltage region is recessed to a given thickness by a pre-treatment cleaning process but a given thickness of the pad oxide film remains intact.
12. The method of claim 1 , further comprising the step of performing the DHF cleaning process and the SC-1 cleaning process for the entire polished surface, after polishing the insulating film.
13. The method of claim 1 , further comprising the step of performing the DHF cleaning process and the SC-1 cleaning process for the entire surface from which the pad nitride film is stripped, after stripping the pad nitride film.
14. A method for forming an isolation film, comprising:
forming a pad oxide film over a cell region, a low voltage region and a high voltage region in a semiconductor substrate;
forming a pad nitride film over the pad oxide film;
forming trenches by etching the pad nitride film, the pad oxide film and the semiconductor substrate selectively;
forming an insulating film to bury the trenches;
polishing the insulating film;
removing the pad nitride film; and
performing a first cleaning process using a Diluted HF (DHF) or Buffered Oxide Etchant (BOE) and a second cleaning process using a Standard Clean-1(SC-1) cleaning process to remove the pad oxide film over the cell region and low voltage region and to recess the pad oxide film over the high voltage region.
15. The method of claim 14 , comprising performing the SC-1 cleaning process at a temperature ranging from 60° C. to 70° C.
16. The method of claim 14 , comprising performing the cleaning process using the DHF using a HF solution in which H 2 O is diluted in the ratio of 50:1 for 30 to 100 seconds.
17. The method of claim 14 , comprising performing the cleaning process using the DHF while the pad oxide film formed in the high voltage region is recessed ½ to ¾ of the entire etch target.
18. The method of claim 14 , comprising performing the cleaning process using the DHF.
19. The method of claim 14 , comprising performing the SC-1 cleaning process is while the pad oxide film formed in the high voltage region is recessed ¼ to ½ of the entire etch target.
20. The method of claim 14 , further comprising performing a cleaning process using a DHF and SC-1 to control a thickness of the insulating film after removing the pad nitride film.