Substrate processing method and substrate processing apparatus

1. A substrate processing method, comprising:

preparing a phosphoric acid processing liquid by supplying a precipitation inhibitor configured to inhibit precipitation of silicon oxide by being combined with a silicon oxide film of a substrate into a phosphoric acid aqueous solution;

etching the substrate having the silicon oxide film and a silicon nitride film by immersing the substrate in a processing tub in which the phosphoric acid processing liquid is stored; and

increasing a concentration of the precipitation inhibitor in the phosphoric acid processing liquid by additionally supplying the precipitation inhibitor into the phosphoric acid processing liquid in the processing tub when a number of substrates etched by the phosphoric acid processing liquid has reached a first threshold value or when a silicon concentration in the phosphoric acid processing liquid has reached a second threshold value,

wherein the first threshold value or the second threshold value is determined based on a number of the additional supplies of the precipitation inhibitor, and

wherein the etching of the substrate comprises, after the increasing of the concentration of the precipitation inhibitor, etching a new substrate by immersing the new substrate in the processing tub in which the phosphoric acid processing liquid with the increased concentration of the precipitation inhibitor is stored.

2. The substrate processing method of claim 1 , further comprising:

draining all of the phosphoric acid processing liquid from the processing tub when the number of the substrates etched by the phosphoric acid processing liquid has reached a third threshold value higher than the first threshold value, or when the silicon concentration in the phosphoric acid processing liquid has reached a fourth threshold value higher than the second threshold value.

3. The substrate processing method of claim 2 ,

wherein the increasing of the concentration of the precipitation inhibitor is performed twice or more between an end of the preparing of the phosphoric acid processing liquid and a start of the draining of all of the phosphoric acid processing liquid.

4. The substrate processing method of claim 3 ,

wherein the increasing of the concentration of the precipitation inhibitor comprises:

additionally supplying the precipitation inhibitor into the phosphoric acid processing liquid within the processing tub; and

circulating the precipitation inhibitor together with the phosphoric acid processing liquid through a circulation path provided in the processing tub.

5. The substrate processing method of claim 3 ,

wherein the increasing of the concentration of the precipitation inhibitor is performed between an end of the etching of the substrate being currently performed and a start of the etching of the substrate to be performed next.

6. The substrate processing method of claim 2 ,

wherein the increasing of the concentration of the precipitation inhibitor comprises:

additionally supplying the precipitation inhibitor into the phosphoric acid processing liquid within the processing tub; and

circulating the precipitation inhibitor together with the phosphoric acid processing liquid through a circulation path provided in the processing tub.

7. The substrate processing method of claim 6 ,

wherein the processing tub comprises:

an inner tub, having a top opening, configured to store the phosphoric acid processing liquid therein; and

an outer tub disposed outside the inner tub to receive the phosphoric acid processing liquid flown out from the opening,

wherein the inner tub is provided with a gas discharge unit configured to discharge a gas into the inner tub, and

in the additionally supplying of the precipitation inhibitor, the precipitation inhibitor is supplied into the inner tub.

8. The substrate processing method of claim 7 ,

wherein in the additionally supplying of the precipitation inhibitor, the precipitation inhibitor is dripped onto a liquid surface of the phosphoric acid processing liquid from a position higher than the liquid surface within the inner tub.

9. The substrate processing method of claim 2 ,

wherein the increasing of the concentration of the precipitation inhibitor is performed between an end of the etching of the substrate being currently performed and a start of the etching of the substrate to be performed next.

10. The substrate processing method of claim 1 ,

wherein the increasing of the concentration of the precipitation inhibitor comprises:

additionally supplying the precipitation inhibitor into the phosphoric acid processing liquid within the processing tub; and

circulating the precipitation inhibitor together with the phosphoric acid processing liquid through a circulation path provided in the processing tub.

11. The substrate processing method of claim 10 ,

wherein the processing tub comprises:

an inner tub, having a top opening, configured to store the phosphoric acid processing liquid therein; and

an outer tub disposed outside the inner tub to receive the phosphoric acid processing liquid flown out from the opening,

wherein the inner tub is provided with a gas discharge unit configured to discharge a gas into the inner tub, and

in the additionally supplying of the precipitation inhibitor, the precipitation inhibitor is supplied into the inner tub.

12. The substrate processing method of claim 11 ,

wherein in the additionally supplying of the precipitation inhibitor, the precipitation inhibitor is dripped onto a liquid surface of the phosphoric acid processing liquid from a position higher than the liquid surface within the inner tub.

13. The substrate processing method of claim 1 ,

wherein the increasing of the concentration of the precipitation inhibitor is performed between an end of the etching of the substrate being currently performed and a start of the etching of the substrate to be performed next.