Method of fabricating semiconductor device including forming a protective layer and removing after etching a trench
View Patent ↗The method of fabricating a semiconductor device includes subjecting a semiconductor substrate to trench etching by alternately repeating an etching step and a deposition step. The etching step creates a trench structure by dry-etching the exposed surface of the semiconductor substrate. An etching mask is formed on the surface of the semiconductor substrate so that the semiconductor substrate has the exposed portion. The deposition step deposits a protection film for suppressing etching of the trench side walls. The method of fabricating a semiconductor device also includes subjecting the semiconductor substrate that has just undergone the trench etching to a heat treatment at a predetermined temperature. The semiconductor substrate is heat-treated within a temperature range of 300 to 500° C. immediately following the trench etching, for example. Plasma ashing is then performed.
1. A method of fabricating a semiconductor device comprising:
subjecting a semiconductor substrate to trench etching by alternately repeating an etching step of forming a trench structure by dry-etching an exposed portion of a surface of the semiconductor substrate, the exposed portion being not covered with an etching mask that covers a remaining portion of the surface of the semiconductor substrate, and a deposition step of depositing a fluorocarbon protection film for suppressing etching of a trench side wall;
completing the trench etching when the trench structure has a predetermined depth; and
subjecting the semiconductor substrate to a heat treatment at a predetermined temperature following the trench etching further comprising subjecting the heat-treated semiconductor substrate to plasma ashing, thereby removing the protection film from the trench side wall.
2. The method of fabricating a semiconductor device according to claim 1 , wherein the predetermined temperature is between 300° C. and 500° C.
3. The method of fabricating a semiconductor device according to claim 1 , further comprising wetting the heat-treated semiconductor device with an acid solution.
4. The method of fabricating a semiconductor device according to claim 3 , further comprising subjecting the wetted semiconductor substrate to plasma ashing, thereby removing the protection film from the trench side wall.
5. The method of fabricating a semiconductor device according to claim 1 , wherein the semiconductor device is a MEMS device or a MIST device.
6. The method of fabricating a semiconductor device according to claim 1 , wherein the etching step is performed with SF6 gas plasma and the deposition step is performed with C4F8 gas plasma.
7. The method of fabricating a semiconductor device according to claim 1 , wherein the protection film is a fluorocarbon polymer film.
8. The method of fabricating a semiconductor device according to claim 1 , wherein the trench structure obtained by the trench etching is about 80 μm in width and about 500 μm in depth.
9. The method of fabricating a semiconductor device according to claim 1 , wherein the heat treatment is performed by raising a temperature at a rate of 1° C./sec up to the predetermined temperature from room temperature, maintaining the predetermined temperature for a predetermined period and lowering the temperature to the room temperature.
10. The method of fabricating a semiconductor device according to claim 3 , wherein the acid solution includes a mixed solution of acetic acid, ammonium fluoride and ammonium hydrogen fluoride.
11. The method of fabricating a semiconductor device according to claim 1 , wherein the etching mask is a resist mask.
12. The method of fabricating a semiconductor device according to claim 7 , wherein the heat treatment partially decomposes the protection film on the trench side wall.
13. The method of fabricating a semiconductor device according to claim 6 , wherein the heat treatment partially decomposes the protection film on the trench side wall.
14. The method of fabricating a semiconductor device according to claim 1 , wherein the heat treatment partially decomposes the protection film on the trench side wall.
15. A method of fabricating a semiconductor device compromising:
dry-etching an exposed portion of a surface of a semiconductor substrate, the exposed portion being not covered with an etching mask that covers a remaining portion of the surface of the semiconductor substrate, and forming a trench that includes a trench bottom and a trench sidewall, the trench bottom being defined by a bottom portion of the dry-etched surface, the trench sidewall being defined by a sidewall portion of the dry-etched surface;
a trench etching step including sub steps of:
depositing a fluorocarbon protection film on the trench bottom and the trench sidewall, and
dry-etching the protection film deposed on the bottom of the trench so as to expose at least a portion of the semiconductor substrate, and further dry-etching the exposed portion of the semiconductor substrate;
partially decomposing the protection film on the trench sidewall by heating the semiconductor substrate at a predetermined temperature following the trench etching step; and
removing the partially-decomposed protection film from the trench sidewall by performing plasma ashing on the heated semiconductor.