Method for manufacturing a semiconductor device having trenches defined in the substrate surface
View Patent ↗In the method for manufacturing a semiconductor device according to the invention including the step of forming trenches having the depth thereof in perpendicular to the major surface of a semiconductor substrate, the step of forming trenches includes the steps of performing trench etching using an insulator film, formed on the major surface of the semiconductor substrate and shaped with a predetermined pattern, for a mask to form the trenches; etching the inside of the trenches using a halogen containing gas to smoothen the inside of the trenches; and thermally treating in a non-oxidizing and non-nitriding atmosphere. The manufacturing method according to the invention facilitates well removing the etching residues remaining in the trenches and rounding the trench corners properly when the trenches are 2 μm or narrower in width and even when the trenches are 1 μm or narrower in width.
1. A method for manufacturing a semiconductor device including a semiconductor substrate having a major surface in which trenches are defined, the method comprising the steps of:
a. providing an insulator film on the major surface of the semiconductor substrate;
b. shaping the insulator film with a predetermined pattern to provide a mask; and
c. performing trench etching using the mask to form the trenches;
d. thermally treating the device in a non-oxidizing and non-nitriding atmosphere in an initial thermal treatment;
e. etching inside the trenches using a halogen-containing gas to smooth the inside of the trenches; and
f. thermally treating the device in a non-oxidizing and non-nitriding atmosphere in a further thermal treatment.
2. The method according to claim 1 , wherein the trenches have a width which is 2.0 μm or less and a depth which is 0.5 μm or more.
3. The method according to claim 2 , wherein the trenches have a width which is 1.0 μm or less.
4. The method according to claim 1 , wherein etching inside the trenches in step (e) comprises anisotropic dry etching.
5. The method according to claim 1 , wherein the halogen-containing gas comprises one of hydrogen chloride gas or chlorine gas.
6. The method according to claim 5 , wherein etching inside the trenches in step (e) includes using hydrogen for a carrier gas and etching the inside of the trenches in an atmosphere under a pressure ranging between 100×133.3 Pa and 760×133.3 Pa and a temperature ranging between 900° C. and 1050° C.
7. The method according to claim 5 , wherein etching inside the trenches in step (e) is performed so that the sidewalls of the trenches have a taper angle which ranges between 87 degrees and 90 degrees.
8. The method according to claim 1 , further comprising the steps of:
g. forming a sacrificial oxide film on inner walls of each trench after thermally treating in step (f);
h. removing the sacrificial oxide film; and
i. forming a gate oxide film on the inner walls of each trench.
9. The method according to claim 8 , wherein the gate oxide film comprises a silicon oxide film.
10. The method according to claim 9 , wherein the gate oxide film comprises a laminate comprising a silicon nitride film.
11. The method according to claim 1 , further comprises the step of rotating the substrate.
12. The method according to claim 1 , wherein thermally treating in step (d) or in step (f) is performed in a carrier gas atmosphere under a pressure of 760×133.3 Pa or lower and a temperature ranging between 900° C. and 1050° C.
13. The method according to claim 1 , wherein the thermally treating in step (d) and in step (f) are performed in a carrier gas atmosphere under a pressure of 760×133.3 Pa or lower and a temperature ranging between 900° C. and 1050° C.
14. The method according to claim 1 , wherein the non-oxidizing and non-nitriding atmosphere used in thermally treating in step (d) and in step (d) includes a gas selected from the group consisting of hydrogen, argon, and helium.