Method for manufacturing micro structure
View Patent ↗A method for forming a pattern includes the steps of: (a) preparing a lower hard mask layer and an upper hard mask layer stacked on an etching target film; (b) forming a resist pattern above the upper hard mask layer; (c) etching the upper hard mask film by using the resist pattern as an etching mask to form an upper hard mask; (d) after the step (c), removing the resist pattern; (e) after the step (d), thinning the upper hard mask by etching; (f) etching the lower hard mask film by using the thinned upper hard mask as an etching mask to form a lower hard mask; and (g) etching the etching target film by using the upper hard mask and the lower hard mask as an etching mask. The method for forming a pattern can etch a fine pattern with good yield.
1. A method for forming a pattern comprising the steps of:
(a) forming a lower hard mask layer and an upper hard mask layer stacked on an etching object including an etching target film at an uppermost level;
(b) forming a resist pattern above said upper hard mask layer;
(c) etching said upper hard mask layer by using said resist pattern as an etching mask to form an upper hard mask;
(d) after said step (c), removing said resist pattern;
(e) after said step (d), thinning said upper hard mask by etching;
(f) etching said lower hard mask layer by using said thinned upper hard mask as an etching mask to form a lower hard mask; and
(g) etching said etching target film by using both said upper hard mask and said lower hard mask as an etching mask.
2. The method for forming a pattern according to claim 1 , wherein said resist pattern includes an ArF resist film and an underlying antireflection film.
3. The method for forming a pattern according to claim 1 , wherein said step (b) comprises the steps of:
(b-1) exposing and developing said resist pattern; and
(b-2) trimming said resist pattern.
4. The method for forming a pattern according to claim 1 , wherein said step (g) removes said upper hard mask at the same time.
5. The method for forming a pattern according to claim 4 , wherein said etching target film and said upper hard mask layer are both made of poly-silicon, said upper hard mask layer has a thickness equal to or thinner than said etching target film, and said step (g) removes said upper hard mask.
6. The method for forming a pattern according to claim 1 , wherein said etching object has an etch stopper film under said etching target film, said step (g) etches said etching target film by using said etch stopper film as a stopper, and the method for forming a pattern further comprises the step of:
(h) after said step (g), removing said upper hard mask being left by etching.
7. The method for forming a pattern according to claim 1 , wherein the etching object is a micro structure of a semiconductor device, and said etching target film constitutes a gate electrode or a wiring.
8. The method for forming a pattern according to claim 7 , wherein said etching target film and said upper hard mask layer each include a silicon film or a refractory metal film, and said lower hard mask layer is made of inorganic insulator.
9. The method for forming a pattern according to claim 8 , wherein etching in said step (g) is performed by using etching gas which contains one or more of Cl 2 , HBr, Br 2 , HI, HCl and BCl 3 .
10. The method for forming a pattern according to claim 7 , wherein said etching target film includes a silicon film and said upper hard mask layer includes a Si 1-x Ge x (0<x≦1) film.
11. The method for forming a pattern according to claim 10 , wherein said upper hard mask layer is thicker than said etching target film.
12. The method for forming a pattern according to claim 7 , wherein said etching target film constitutes a gate electrode, said etching target film and said upper hard mask layer are poly-silicon films, and said lower hard mask layer is a silicon oxide film or a silicon nitride film.
13. The method for forming a pattern according to claim 12 , further comprises the step of:
(i) after said step (g), depositing a silicon oxide film or a silicon nitride film covering said gate electrode, and reactive-etching said silicon oxide film or said silicon nitride film to form side wall spacers on side walls of said gate electrode, while removing said lower hard mask at the same time.
14. The method for forming a pattern according to claim 7 , wherein said etching target film constitutes a gate electrode, said etching target film includes a TiN film and a W film formed on said TiN film.
15. The method for forming a pattern according to claim 14 , wherein said step (g) includes the step of:
(g-1) etching said W film by using said TiN film as an etch stopper.
16. The method for forming a pattern according to claim 7 , wherein said etching target film constitutes a gate electrode, said etching target film includes a TaN film and a silicon film formed on said TaN film, and said upper hard mask layer is a silicon film.
17. The method for forming a pattern according to claim 16 , wherein said step (g) includes the step of:
(g-1) etching said silicon film by using said TaN film as an etch stopper.
18. The method for forming a pattern according to claim 1 , wherein at least one of said steps (d) and (e) is executed by using etching gas which is a mixture of O 2 -containing gas and fluorine-containing gas of at least one of CF 4 , CH x F y , C x F y , SF 6 and NF 3 .
19. The method for forming a pattern according to claim 18 , wherein a ratio of the O 2 -containing gas to the fluorine-containing gas in the etching gas is larger than 1.
20. The method for forming a pattern according to claim 1 , wherein said step (e) etches said lower hard mask layer at the same time.