Supercritical drying method for semiconductor substrate
According to one embodiment, a supercritical drying method for a semiconductor substrate comprises introducing a semiconductor substrate, a surface of the semiconductor substrate being wet with a water-soluble organic solvent, to the inside of a chamber, hermetically sealing the chamber and increasing a temperature inside the chamber to not lower than a critical temperature of the water-soluble organic solvent, thereby bringing the water-soluble organic solvent into a supercritical state, decreasing a pressure inside the chamber and changing the water-soluble organic solvent in the supercritical state to a gas, thereby discharging the water-soluble organic solvent from the chamber, starting a supply of an inert gas into the chamber as the pressure inside the chamber decreases to atmospheric pressure, and cooling the semiconductor substrate in a state where the inert gas exists inside the chamber.
1. A supercritical drying method for a semiconductor substrate, comprising:
introducing a semiconductor substrate, a surface of the semiconductor substrate being wet with a water-soluble organic solvent, to the inside of a chamber;
hermetically sealing the chamber and increasing a temperature inside the chamber to not lower than a critical temperature of the water-soluble organic solvent, thereby bringing the water-soluble organic solvent into a supercritical state;
decreasing a pressure inside the chamber and changing the water-soluble organic solvent in the supercritical state to a gas, thereby discharging the water-soluble organic solvent from the chamber;
starting a supply of an inert gas into the chamber as the pressure inside the chamber decreases to atmospheric pressure, and
cooling the semiconductor substrate in a state where the inert gas exists inside the chamber.
2. The supercritical drying method for a semiconductor substrate according to claim 1 , wherein the inert gas is kept being discharged from the chamber while the inert gas is kept being supplied into the chamber when cooling the semiconductor substrate.
3. The supercritical drying method for a semiconductor substrate according to claim 1 , wherein the chamber is hermetically sealed when cooling the semiconductor substrate.
4. The supercritical drying method for a semiconductor substrate according to claim 1 , wherein the temperature inside the chamber is kept not lower than the critical temperature of the water-soluble organic solvent during the decrease in pressure inside the chamber.
5. The supercritical drying method for a semiconductor substrate according to claim 1 , wherein the water-soluble organic solvent in an amount corresponding to a volume of the chamber and the critical temperature and critical pressure of the water-soluble organic solvent is supplied into the chamber before the temperature inside the chamber is increased.
6. The supercritical drying method for a semiconductor substrate according to claim 1 , wherein a film containing tungsten, molybdenum, tungsten nitride, molybdenum nitride, titanium nitride or polysilicon is formed on the semiconductor substrate.
7. The supercritical drying method for a semiconductor substrate according to claim 1 , wherein a boiling point of the water-soluble organic solvent is lower than a boiling point of pure water.
8. The supercritical drying method for a semiconductor substrate according to claim 7 , wherein the water-soluble organic solvent is alcohol or ketone.
9. The supercritical drying method for a semiconductor substrate according to claim 8 , wherein the alcohol is isopropyl alcohol.
10. The supercritical drying method for a semiconductor substrate according to claim 1 , wherein the inert gas is nitrogen, carbonic acid or a noble gas.
11. The supercritical drying method for a semiconductor substrate according to claim 1 , wherein the inert gas is supplied into the chamber and an atmosphere is discharged from the chamber after introduction of the semiconductor substrate into the chamber and before hermetical sealing of the chamber.
12. The supercritical drying method for a semiconductor substrate according to claim 1 , wherein a concavo-convex pattern is formed on the semiconductor substrate.
13. The supercritical drying method for a semiconductor substrate according to claim 12 , wherein a film containing tungsten, molybdenum, tungsten nitride, molybdenum nitride, titanium nitride or polysilicon is formed in a convex part of the concavo-convex pattern.