Method for forming silicon oxynitride film
A silicon oxynitride film is formed on a target substrate by CVD, in a process field configured to be selectively supplied with a first process gas containing a chlorosilane family gas, a second process gas containing an oxidizing gas, and a third process gas containing a nitriding gas. This method alternately includes first to sixth steps. The first, third, and fifth steps perform supply of the first, second, and third process gases, respectively, while stopping supply of the other two process gases. Each of the second, fourth, and sixth steps stops supply of the first to third process gases. The third and fifth steps include an excitation period of supplying the second and third process gases, respectively, to the process field while exciting the respective process gases by an exciting mechanism.
1. A film formation method for a semiconductor process for forming a silicon oxynitride film on a plurality of target substrates set at intervals in a vertical direction by CVD, in a process field configured to be selectively supplied with a first process gas containing a chlorosilane family gas, a second process gas containing an oxidizing gas, and a third process gas containing a nitriding gas, the method alternately comprising, in an order set forth below:
a first step of performing supply of the first process gas to the process field while stopping supply of the second and third process gases to the process field;
a second step of stopping supply of the first, second, and third process gases to the process field;
a third step of performing supply of the second process gas to the process field while stopping supply of the first and third process gases to the process field, the third step comprising an excitation period of supplying the second process gas to the process field while exciting the second process gas by plasma generated by an exciting mechanism common to the second process gas and the third process gas;
a fourth step of stopping supply of the first, second, and third process gases to the process field;
a fifth step of performing supply of the third process gas to the process field while stopping supply of the first and second process gases to the process field, the fifth step comprising an excitation period of supplying the third process gas to the process field while exciting the third process gas by plasma generated by the exciting mechanism;
and a sixth step of stopping supply of the first, second, and third process gases to the process field.
2. The method according to claim 1 , wherein the first to sixth steps are arranged to set the process field to be 400 to 550° C.
3. The method according to claim 1 , wherein the first step is arranged to set the process field at 400 to 1,200 Pa, the third step is arranged to set the process field at 40 to 400 Pa, and the fifth step is arranged to set the process field at 40 to 100 Pa.
4. The method according to claim 1 , wherein the chlorosilane family gas comprises at least one gas selected from the group consisting of dichlorosilane, hexachlorodisilane, trichlorosilane, and tetrachlorosilane.
5. The method according to claim 1 , wherein the oxidizing gas comprises at least one gas selected from the group consisting of oxygen, nitrogen oxide, and dinitrogen oxide.
6. The method according to claim 1 , wherein the nitriding gas comprises ammonia gas.
7. The method according to claim 1 , wherein gas inside the process field is kept exhausted from the first step to the sixth step.
8. The method according to claim 7 , wherein each of the second and sixth steps comprises a period of supplying an inactive gas to the process field.
9. The method according to claim 8 , wherein the fourth step comprises a period of supplying the inactive gas to the process field at a flow rate less than ⅕ of that in the second and sixth steps.
10. The method according to claim 1 , wherein the second and third process gases are supplied from a common supply port.
11. The method according to claim 10 , wherein the exciting mechanism comprises a plasma generation area disposed in a space communicating with the process field and between the target substrates and the common supply port, and each of the second and third process gases is excited while passing through the plasma generation area.
12. The method according to claim 11 , wherein the first process gas is supplied to the process field from a position between the plasma generation area and the target substrates.
13. The method according to claim 11 , wherein the third step is arranged to set the common supply port at 70 to 400 Pa, and the fifth step is arranged to set the common supply port at 70 to 600 Pa.
14. The method according to claim 1 , wherein the target substrates are heated by a heater disposed around the process field.
15. The method according to claim 14 , wherein each of the first, second, and third process gases is supplied from a plurality of gas spouting holes to form gas flows parallel with the target substrates, and the gas spouting holes are arrayed over the target substrates in a vertical direction.