Method for drying substrates
The invention relates to a method for drying substrates, particularly semiconductor wafers, after a wet treatment carried out in a treatment liquid. According to the invention, a gas mixture, which consists of a carrier gas and of an active constituent and which reduces the surface tension of the treatment liquid, is applied to the treatment liquid. By producing a relative motion between the substrates and the liquid, the substrates are moved out of the liquid. In order to provide a selectable, preferably constant, isopropyl alcohol (IPA) concentration at any time during the drying process, the concentration of the active constituent of the gas mixture is actively controlled or regulated. Alternatively, the gas mixture is formed, at least in part, by introducing a predetermined amount of carrier gas and a predetermined amount of liquid of the active constituent into an evaporator.
1 - 15 . (canceled)
16 . A method of drying substrates after a wet treatment thereof in treatment liquid, including the steps of:
forming a gas mixture that comprises a carrier gas and an active substituent, and that reduces the surface tension of the treatment liquid, by conveying the carrier gas through a liquid of the active substituent;
actively controlling a concentration of the active substituent in the gas mixture in an open or closed loop manner;
actively controlling a temperature of the liquid of the active substituent to a predetermined temperature in an open or closed loop manner;
applying the gas mixture to the treatment liquid; and
moving the substrates out of the treatment liquid by generating a relative movement between the substrates and the treatment liquid.
17 . A method according to claim 16 , wherein the gas mixture is formed by mixing essentially pure carrier gas and a mixture of carrier gas and the active substituent.
18 . A method according to claim 16 , wherein the temperature of the liquid of the active substituent is kept essentially constant.
19 . A method according to claim 16 , wherein the temperature of the liquid of the active substituent is altered in a controlled manner throughout a drying process.
20 . A method according to claim 19 , wherein the concentration of the active substituent in the gas mixture is measured, and wherein the temperature of the liquid of the active substituent is adjusted as a function of the measured concentration.
21 . A method according to claim 16 , wherein a flow rate of the carrier gas is controlled in an open or closed loop manner.
22 . A method according to claim 21 , wherein the flow rate of the carrier gas is altered throughout a drying process.
23 . A method according to claim 21 , wherein the concentration of the active substituent in the gas mixture is measured, and the flow rate of the carrier gas is adjusted as a function of the measured concentration.
24 . A method according to claim 16 , wherein the gas mixture is at least partially formed by introducing a predetermined quantity of the carrier gas and a predetermined quantity of a liquid of the active substituent into an evaporator.
25 . A method according to claim 24 , wherein the concentration of the active substituent in the gas mixture is measured downstream of the evaporator, and wherein a flow rate of at least one of the carrier gas and the liquid of the active substituent is adjusted as a function of the measured concentration in order to obtain a predetermined concentration.
26 . A method according claim 16 , wherein the concentration of the active substituent in the gas mixture is altered as a function of a position of the substrates relative to a surface of the treatment liquid.
27 . A method according to claim 26 , wherein the concentration of the active substituent in the gas mixture is increased as a cross-sectional surface between the substrates and the treatment liquid increases, and is decreased as the cross-sectional surface is decreased.
28 . A method according to claim 16 , wherein the active substituent is isopropyl alcohol (IPA), and wherein the average IPA concentration in the gas mixture is kept below 15% of a lower explosion level (LEL).
29 . A method according to claim 28 , wherein the average IPA concentration in the gas mixture is kept below 10% of the lower explosion level (LEL).
30 . A method according to claim 28 , wherein the average IPA concentration in the gas mixture is kept between 3 and 10% of the lower explosion level (LEL).