Method of manufacturing a semiconductor device
View Patent ↗Even though photolithography with a diameter of 0.20 μm or less is employed, a contact hole having a tapered shape with a required width including a positioning tolerance can be formed in a narrower gap between the gate electrodes. A method forms a minute contact hole between gate electrodes of a semiconductor device, which has a silicon dioxide film disposed at an upper layer of the semiconductor device and a BPSG film disposed below the silicon dioxide film. The BPSG film has gate electrodes therein, and no silicon nitride film is disposed on top and side surfaces of the gate electrodes, and no silicon nitride film is disposed above the gate electrodes. The silicon dioxide film is etched by a mixed gas of CF 4 , O 2 and Ar at a substrate temperature of at least 40° C. The BPSG film is etched by over-etching of the silicon dioxide film so that a W-like shape is formed in the BPSG film. Subsequently the BPSG film is etched by a mixed gas of C 4 F 8 , CH 2 F 2 and Ar without including CO gas and O 2 gas so that the contact hole between the adjacent gate electrodes has a forward tapered shape with a tapered angle of less than 90 degree.
1. A method of fabricating a semiconductor device having a silicon dioxide film disposed at an upper layer of the semiconductor device and a BPSG film disposed below the silicon dioxide film, the BPSG film having gate electrodes therein, and no silicon nitride film being disposed on top and side surfaces of the gate electrodes and no silicon nitride film being disposed above the gate electrodes, the method including formation of a contact hole between adjacent gate electrodes, the contact hole formation method comprising the steps of:
etching the silicon dioxide film by a mixed gas of CF 4 , O 2 and Ar at a substrate temperature of at least 40° C. using a resist mask layer for forming the contact hole, and etching the BPSG film by over-etching of the silicon dioxide film so that a W-like shape is formed in the BPSG film; and
subsequently etching the BPSG film by a mixed gas of C 4 F 8 , CH 2 F 2 and Ar without including CO gas and O 2 gas so that the contact hole between the adjacent gate electrodes has a forward tapered shape with a tapered angle of less than 90 degree.
2. The method according to claim 1 , wherein the mixed gas of CF 4 , O 2 and Ar has a composition ratio of CF 4 :O 2 :Ar=3:1:8 on a gas volume basis.
3. The method according to claim 1 , wherein a value obtained from a formula of (CF4 gas content+O2 gas content)/(Ar gas content) of the mixed gas of CF 4 , O 2 and Ar on a gas volume basis is in a range of from 6/6 to 2/10.
4. The method according to claim 1 , wherein a value obtained from a formula of (CF4 gas content)/(O2 gas content) of the mixed gas of CF 4 , O 2 and Ar on a gas volume basis is in a range of from 3.5/0.5 to 1/3.
5. The method according to claim 1 , wherein the substrate temperature during the etching of the silicon dioxide film is in a range from 40° C. to 80° C.
6. The method according to claim 1 , wherein the mixed gas of C 4 F 8 , CH 2 F 2 and Ar has a gas composition ratio of C 4 F 8 :CH 2 F 2 :Ar=7:4:500 on a gas volume basis.
7. The method according to claim 1 , wherein a value obtained from a formula of (Ar gas flow rate)/(total gas flow rate)×100 of the mixed gas of C 4 F 8 , CH 2 F 2 and Ar on a gas volume basis is in a range of from 96.7% to 98.0%.
8. The method according to claim 1 , wherein a value obtained from a formula of (C 4 F 8 gas content)/(CH 2 F 2 gas content) of the mixed gas of C 4 F 8 , CH 2 F 2 and Ar on a gas volume basis is greater than 0 and not more than 1, and a value obtained from a formula of (C 4 F 8 gas content+CH 2 F 2 gas content)/(total gas flow rate) of the mixed gas of C 4 F 8 , CH 2 F 2 and Ar on a gas volume basis is not less than 10/512 and not more than 17/512.
9. The method according to claim 1 , wherein the semiconductor device is an EPROM.
10. A method of fabricating a semiconductor device having a silicon dioxide film disposed at an upper layer of the semiconductor device, a BPSG film disposed below the silicon dioxide film, and a silicon nitride film disposed below the BPSG film but no silicon nitride film being disposed on top and side surfaces of the gate electrodes and no silicon nitride film being disposed above the gate electrodes, the BPSG film having gate electrodes therein, the method including provision of an organic film on the silicon dioxide film and formation of a contact hole between adjacent gate electrodes, the contact hole formation method comprising the steps of:
forming a mask pattern with a maximum opening of 0.20 μm in a resist mask applied on the organic film;
etching the silicon dioxide film and the organic film by a mixed gas of CF 4 , O 2 and Ar at a substrate temperature of at least 40° C., and etching the BPSG film by an over-etching of the silicon dioxide film so that a W-like shape is formed in the BPSG film;
subsequently etching the BPSG film by a mixed gas of C 4 F 8 , CH 2 F 2 and Ar without including CO gas and O 2 gas so that the contact hole between the adjacent gate electrodes has a forward tapered shape with a tapered angle of 85 degree; and
subsequently etching the silicon nitride film by an over-etching of the BPSG film.
11. The method according to claim 10 , wherein the mixed gas of CF 4 , O 2 and Ar has a composition ratio of CF 4 :O 2 :Ar=3:1:8 on a gas volume basis.
12. The method according to claim 10 , wherein a value obtained from a formula of (CF4 gas content+O2 gas content)/(Ar gas content) of the mixed gas of CF 4 , O 2 and Ar on a gas volume basis is in a range of from 6/6 to 2/10.
13. The method according to claim 10 , wherein a value obtained from a formula of (CF4 gas content)/(O2 gas content) of the mixed gas of CF 4 , O 2 and Ar on a gas volume basis is in a range of from 3.5/0.5 to 1/3.
14. The method according to claim 10 , wherein the substrate temperature during the etching of the silicon dioxide film is in a range from 40° C. to 80° C.
15. The method according to claim 10 , wherein the mixed gas of C 4 F 8 , CH 2 F 2 and Ar has a gas composition ratio of C 4 F 8 :CH 2 F 2 :Ar=7:4:500 on a gas volume basis.
16. The method according to claim 10 , wherein a value obtained from a formula of (Ar gas flow rate)/(total gas flow rate)×100 of the mixed gas of C 4 F 8 , CH 2 F 2 and Ar on a gas volume basis is in a range of from 96.7% to 98.0%.
17. The method according to claim 10 , wherein a value obtained from a formula of (C 4 F 8 gas content)/(CH 2 F 2 gas content) of the mixed gas of C 4 F 8 , CH 2 F 2 and Ar on a gas volume basis is greater than 0 and not more than 1, and that a value obtained from a formula of (C 4 F 8 gas content+CH 2 F 2 gas content)/(total gas flow rate) of the mixed gas of C 4 F 8 , CH 2 F 2 and Ar on a gas volume basis is not less than 10/512 and not more than 17/512.
18. The method according to claim 10 , wherein the semiconductor device is an EPROM.
19. The method according to claim 10 , wherein the organic film is a bottom antireflective coating (BARC) film.
20. A method of fabricating a semiconductor device having a silicon dioxide film disposed at an upper layer of the semiconductor device, a BPSG film disposed below the silicon dioxide film, and a silicon nitride film disposed below the BPSG film but no silicon nitride film being disposed on top and side surfaces of the gate electrodes and no silicon nitride film being disposed above the gate electrodes, the BPSG film having gate electrodes therein, the method including formation of a contact hole between adjacent gate electrodes,
the contact hole formation method comprising the step of etching the silicon nitride film through the contact hole by using a mixed gas of C 4 F 8 , CH 2 F 2 and Ar as an etching gas with a gas composition ratio of (C 4 F 8 gas content)/(CH 2 F 2 gas content) being less than 1 on a gas volume basis,
wherein a resist mask has a first opening for the contact hole with a maximum opening of 0.2 μm and a second opening for an alignment mark of photolithography formed on an upper layer or for measurement of the alignment with a minimum opening of 0.25 μm so that etching through the second opening is stopped at the silicon nitride film when the contact hole is opened for connection.