Supercritical drying method for semiconductor substrate
View Patent ↗In one embodiment, after rinsing a semiconductor substrate having a fine pattern formed thereon with pure water, the pure water staying on the semiconductor substrate is substituted with a water soluble organic solvent, and then, the semiconductor substrate is introduced into a chamber in a state wet with the water soluble organic solvent. Then, the water soluble organic solvent is turned into a supercritical state by increasing a temperature inside of the chamber. Thereafter, the inside of the chamber is reduced in pressure while keeping the inside of the chamber at a temperature enough not to liquefy the pure water (i.e., rinsing pure water mixed into the water soluble organic solvent), and further, the water soluble organic solvent in the supercritical state is changed into a gaseous state, to be discharged from the chamber, so that the semiconductor substrate is dried.
1. A supercritical drying method for a semiconductor substrate, comprising:
cleaning the semiconductor substrate with a chemical solution;
rinsing the semiconductor substrate with pure water to cover a surface of the semiconductor substrate with the pure water after the cleaning;
supplying a water soluble organic solvent onto the semiconductor substrate after the rinsing, to replace the pure water covering the surface of the semiconductor substrate with the water soluble organic solvent;
introducing the semiconductor substrate into a chamber, the surface of the semiconductor substrate being covered with the water soluble organic solvent;
increasing a temperature inside of the chamber up to a critical temperature of the water soluble organic solvent or higher, to turn the water soluble organic solvent into a supercritical state;
after turning the water soluble organic solvent into the supercritical state, increasing a temperature inside of the chamber to turn pure water in the chamber into steam while maintaining the water soluble organic solvent in the supercritical state; and
decreasing a pressure inside of the chamber while keeping a temperature inside of the chamber at a predetermined value at which the steam is not liquefied, to turn the water soluble organic solvent in the supercritical state into a gaseous state, thus discharging the water soluble organic solvent from the chamber.
2. The supercritical drying method for a semiconductor substrate according to claim 1 , wherein the predetermined temperature is a temperature at which a steam pressure of the pure water becomes higher than a critical pressure of the water soluble organic solvent.
3. The supercritical drying method for a semiconductor substrate according to claim 2 , wherein a steam pressure of the water soluble organic solvent is higher than that of the pure water.
4. The supercritical drying method for a semiconductor substrate according to claim 3 , wherein the water soluble organic solvent includes alcohol or ketone.
5. The supercritical drying method according to claim 1 , wherein before increasing the temperature inside of the chamber, the water soluble organic solvent is supplied into the chamber, and a quantity of the supplied water soluble organic solvent is obtained based on the critical temperature of the water soluble organic solvent, a steam pressure of the water soluble organic solvent at the critical temperature, and a volume of the chamber.
6. The supercritical drying method according to claim 5 , wherein, in increasing the temperature inside of the chamber until the water soluble organic solvent is turned into the supercritical state, a gaseous water soluble organic solvent and a liquid water soluble organic solvent coexist inside of the chamber.