Method of producing semiconductor device
It is intended to produce a semiconductor device with a stable gate length, using an end-point detection process based on monitoring a plasma emission intensity during dry etching for setting a gate length. A semiconductor device production method of the present invention comprises the steps of: forming a first dielectric or gate conductive film to allow a pillar-shaped semiconductor layer to be buried therein; flattening the first dielectric or gate conductive film while detecting an end-point using a stopper formed on top of the pillar-shaped semiconductor layer; forming a second dielectric or gate conductive film; etching the second dielectric or gate conductive film and calculating an etching rate during the etching; and detecting an end-point of etching of the first dielectric or gate conductive film, based on the etching rate of the second dielectric or gate conductive film during etching-back of the second dielectric or gate conductive film, to control an etching amount of the first dielectric or gate conductive film.
1. A method of producing a semiconductor device in which at least one pillar-shaped semiconductor layer is provided on a semiconductor substrate, and a dielectric film is provided on respective surfaces of the semiconductor substrate and the at least one pillar-shaped semiconductor layer, the method comprising:
(a) forming a first gate conductive film to cover respective surfaces of the at least one pillar-shaped semiconductor layer and a hard mask formed on a top of the at least one pillar-shaped semiconductor layer;
(b) after step (a), flattening an upper surface of the first gate conductive film, using the hard mask as a stopper;
(c) after step (b), forming a second gate conductive film on the flattened surface of the first gate conductive film;
(d) after step (c), anisotropically etching the second gate conductive film;
(e) monitoring an intensity of plasma emission emitted from the second gate conductive film during the etching to detect an end-point at which the etching of the second gate conductive film needs to end, based on a change in the plasma emission intensity;
(f) after step (e), anisotropically etching the first gate conductive film; and
(g) determining an end-point at which the etching of the first gate conductive film needs to end, using an etching rate of the first gate conductive film determined with a relative ratio between the etching rate of the first gate conductive film and an etching rate of the second gate conductive film calculated from a film thickness of the second gate conductive film and a time taken from a beginning to an end of the etching of the second gate conductive film.
2. The method as defined in claim 1 , wherein each of the first gate conductive film and the second gate conductive film is made of polysilicon.
3. The method as defined in claim 1 , wherein the first gate conductive film and the second gate conductive film are made of a same metal material.
4. The method as defined in claim 1 , wherein the first gate conductive film and the second gate conductive film are made of different metal materials, respectively.
5. The method as defined in claim 1 , wherein the semiconductor substrate comprises a diffusion area formed at a lower surface of a respective of the at least one pillar-shaped semiconductor layer, and the method further comprises:
after step (f), patterning the first gate conductive film on a sidewall of the at least one pillar-shaped semiconductor layer to form a gate electrode; and
(j) after step (i), forming, on an upper surface of a respective of the at least one pillar-shaped semiconductor layer, a diffusion area having the same conductive type as that of the diffusion area formed at the lower surface of a respective of the at least one pillar-shaped semiconductor layer.
6. A method of producing a semiconductor device in which at least one pillar-shaped semiconductor layer is provided on a semiconductor substrate, the method comprising:
(a) forming a first dielectric film to cover respective surfaces of the at least one pillar-shaped semiconductor layer and a hard mask formed on a top of the at least one pillar-shaped semiconductor layer;
(b) after step (a), flattening an upper surface of the first dielectric film, using the hard mask as a stopper;
after step (b), forming a second dielectric film on the flattened surface of the first dielectric film;
(d) after step (c), anisotropically etching the second dielectric film;
(e) monitoring an intensity of plasma emission emitted from the second dielectric film during the etching to detect an end-point at which the etching of the second dielectric film needs to end, based on a change in the plasma emission intensity;
after step (e), anisotropically etching the first dielectric film;
(g) after step (f), forming a gate electrode extensive over an upper surface of the first dielectric film and a sidewall of the at least one pillar-shaped semiconductor layer; and
(h) determining an end-point at which the etching of the first dielectric film needs to end, using an etching rate of the first dielectric film determined with a relative ratio between the etching rate of the first dielectric film and an etching rate of the second dielectric film calculated from a film thickness of the second dielectric film and a time taken from a beginning to an end of the etching of the second dielectric film.
7. The method as defined in claim 6 , wherein each of the first dielectric film and the second dielectric film is made of a silicon oxide.
8. The method as defined in claim 6 , wherein the semiconductor substrate comprises a diffusion area formed at a lower surface of a respective of the at least one pillar-shaped semiconductor layer, and the method further comprises, after step (g), forming, on an upper surface of a respective of the at least one pillar-shaped semiconductor layer, a diffusion area having the same conductive type as that of the diffusion area formed at the lower surface of a respective of the at least one pillar-shaped semiconductor layer.