Method for manufacturing semiconductor device
According to one embodiment, a method for manufacturing a semiconductor device includes forming a silicon film on an upper surface side, a lower surface side, and a side surface side of an air gap, while leaving part of the air gap between the silicon film formed on the upper surface side and the silicon film formed on the lower surface side. The method includes forming a metal film on a side surface of the slit. The method includes forming a plurality of metal silicide layers between the second layers by causing reaction between the metal film and the silicon film. The method includes removing unreacted part of the metal film formed on the side surface of the slit.
1. A method for manufacturing a semiconductor device, comprising:
forming a stacked body above a substrate, the stacked body including a plurality of first layers and a plurality of second layers, the first and second layers including a first layer and a second layer alternately stacked;
forming a slit extending in a stacking direction in the stacked body;
removing the first layers which are alternately stacked and exposed to the slit by etching through the slit to form an air gap between the second layers, the air gap communicating with the slit;
forming a silicon film on an upper surface side of the air gap, a lower surface side of the air gap, and a side surface side of the air gap, the side surface side being different from the slit side, while leaving part of the air gap between the silicon film formed on the upper surface side of the air gap and the silicon film formed on the lower surface side of the air gap;
after the forming the silicon film, forming a metal film on a side surface of the slit;
forming a plurality of metal silicide layers between the second layers by causing reaction between the metal film and the silicon film; and
removing unreacted part of the metal film formed on the side surface of the slit.
2. The method according to claim 1 , wherein the metal film is formed also in the part of the air gap.
3. The method according to claim 1 , wherein the silicon film is not interposed between a side surface on the slit side of the second layer and the metal film.
4. The method according to claim 3 , wherein
the silicon film is formed conformally along the side surface of the second layer, the upper surface side of the air gap, the lower surface side of the air gap, and the side surface side of the air gap, and
before the forming the metal film, the silicon film formed on the side surface of the second layer is removed.
5. The method according to claim 4 , wherein the silicon film formed on the side surface of the second layer is removed after occluding an opening on the slit side of the part of the air gap with a cover silicon film.
6. The method according to claim 4 , wherein the silicon film covering a corner of the side surface of the second layer and the upper surface side of the air gap, and the silicon film covering a corner of the side surface of the second layer and the lower surface side of the air gap occlude an opening on the slit side of the part of the air gap.
7. The method according to claim 3 , wherein
the silicon film is formed conformally along the side surface of the second layer, the upper surface side of the air gap, the lower surface side of the air gap, and the side surface side of the air gap, and
before the forming the metal film, the silicon film exposed in the slit and formed along the side surface of the slit is oxidized.
8. The method according to claim 7 , wherein the metal film covers the side surface of the second layer via an oxidized portion of the silicon film.
9. The method according to claim 7 , wherein the silicon film is oxidized by introducing oxygen ions into the slit.
10. The method according to claim 7 , wherein a portion on the slit side of the metal silicide layer is thinner than another portion of the metal silicide layer.
11. The method according to claim 1 , wherein the metal film is a nickel film, and the metal silicide layer is a nickel silicide layer.
12. The method according to claim 11 , wherein the nickel silicide layer primarily contains NiSi.
13. The method according to claim 12 , wherein a height of the part of the air gap is 17% or more of a height of the air gap.
14. The method according to claim 11 , wherein the nickel silicide layer primarily contains Ni 2 Si.
15. The method according to claim 14 , wherein a height of the part of the air gap is 38% or more of a height of the air gap.
16. The method according to claim 1 , further comprising:
forming a columnar part in the stacked body, the columnar part including a semiconductor body extending in the stacking direction and a charge storage part provided between the semiconductor body and the first layer.
17. The method according to claim 1 , wherein the first layer is a silicon nitride layer, and the silicon nitride layer is removed with an etchant containing phosphoric acid.
18. The method according to claim 1 , further comprising:
after the removing the unreacted part of the metal film, removing the second layers by etching through the slit to form an air gap between the metal silicide layers.
19. The method according to claim 18 , wherein the second layer is a silicon oxide layer, and the silicon oxide layer is removed with an etchant containing hydrofluoric acid.
20. The method according to claim 16 , further comprising:
after the removing the unreacted part of the metal film, forming an insulating film on the side surface of the slit; and
forming an interconnect part via the insulating film in the slit.