System and method of cleaning substrates using a subambient process solution
A system and method of cleaning a substrate utilizing sonic energy and a film of subambient gasified process solution that assists in reducing damage to the substrate. In one aspect, the invention is a method comprising: a) supporting a substrate in a substantially horizontal orientation; b) applying a solution comprising a liquid and a dissolved gas to a surface of the substrate so as to form a film of the solution on the surface of the substrate, the solution being at a subambient temperature; c) coupling a transmitter to the film of the solution, the transmitter acoustically coupled to a transducer for generating sonic energy; and d) applying sonic energy through the film of the solution and to the surface of the substrate via the transmitter. The method is especially useful in minimizing damage when cleaning substrates with a surface comprising a topography having technology nodes with a width less than 100 nanometers. The solution is most preferred to be at a temperature that results in the solution being at or near the solution's minimum specific volume, which for aqueous solution is at or near 4° C. In another aspect, the invention is system for cleaning a substrates that, through the use of at least two specially located temperature sensors, maintains the cleaning solution near its maximum density temperature when applied to the substrate(s) while ensuring that the solution does not freeze in the supply line.
1 . A method of cleaning a substrate comprising:
a) supporting a substrate in a substantially horizontal orientation;
b) applying a solution comprising a liquid and a dissolved gas to a surface of the substrate so as to form a film of the solution on the surface of the substrate, the solution being at a subambient temperature;
c) coupling a transmitter to the film of the solution, the transmitter acoustically coupled to a transducer for generating sonic energy; and
d) applying sonic energy through the film of the solution and to the surface of the substrate via the transmitter.
2 . The method of claim 1 wherein step b) further comprises:
dissolving the gas into the liquid to form the solution, the liquid being at a first temperature;
chilling the solution from the first temperature to the subambient temperature; and
applying the chilled solution to the surface of the substrate.
3 . The method of claim 1 wherein the subambient temperature is at or near a temperature that results in the solution being within 3 kg/m 3 of the solution's maximum density.
4 . The method of claim 1 wherein the subambient temperature is at or near a temperature that results in the solution being at or near the solution's minimum specific volume.
5 . The method of claim 4 wherein the solution is an aqueous solution and the subambient temperature is between 2° C. and 10° C.
6 . The method of claim 5 wherein the subambient temperature is about 4° C.
7 . The method of claim 4 wherein the solution is maintained at the subambient temperature during the performance of step d).
8 . The method of claim 1 wherein the solution is maintained at the subambient temperature during the performance of step d).
9 . The method of claim 1 wherein the sonic energy is megasonic energy having a frequency between 800 and 1100 kHz.
10 . The method of claim 1 wherein the subambient temperature is a temperature that corresponds to the solution being within 20° C. of the solution's freezing point.
11 . The method of claim 1 wherein the surface of the substrate comprises semiconductor devices having having a width that is less than 100 nanometers.
12 . The method of claim 1 wherein the surface of the substrate comprises a topography having nodes with a width that is less than 100 nanometers.
13 . The method of claim 12 wherein the nodes are selected from a group consisting of oxide trenches, metal lines and gates.
14 . The method of claim 1 wherein the gas is air or nitrogen and the liquid is deionized water.
15 . The method of claim 1 wherein the surface of the substrate is substantially free of photoresist and organic residues.
16 . The method of claim 1 wherein the surface of the substrate comprises a topography having nodes with a width that is less than 100 nanometers, the surface of the substrate is substantially free of photoresist and organic residues, and the performance of step d) loosens particles from the surface of the substrate without damaging the topography.
17 . The method of claim 1 wherein step b) comprises chilling the solution from a first temperature to a chilled temperature at or below the subambient temperature with a chiller prior to the solution being applied to the surface of the substrate via a dispenser, the method further comprising:
measuring the temperature of the solution at an exit of the chiller with a first temperature sensor;
measuring the temperature of the solution at the dispenser with a second temperature sensor;
upon the temperature measured by the first temperature sensor being above the subambient temperature, increasing the chilling of the solution in the chiller; and
upon the temperature measured by the second temperature sensor being within a predetermined range of the freezing point of the solution, decreasing the chilling of the solution by the chiller.
18 . A method of cleaning a semiconductor wafer having a device side comprising:
a) supporting a substrate in a substantially horizontal orientation within a gaseous atmosphere, the substrate having a device side comprising a topography having nodes with a width that is less than 100 nanometers;
b) rotating the substrate;
c) applying a solution comprising a liquid and a dissolved gas to the device side of the substrate via a dispenser so as to form a film of the solution on the surface of the substrate, the solution being at a subambient temperature that results in the solution being within 3 kg/m 3 of the solution's maximum density;
d) coupling a transmitter to the film of the solution, the transmitter acoustically coupled to a transducer for generating sonic energy; and
e) applying sonic energy through the film of the solution and to the device side of the substrate via the transmitter.
19 . The method of claim 18 wherein the nodes are selected from a group consisting of oxide trenches, metal lines and gates; the gas is air or nitrogen and the liquid is deionized water; and the surface of the substrate is substantially free of photoresist and organic residues.
20 . The method of claim 18 further comprising:
prior to step c), supplying the solution at a first temperature to a chiller, the first temperature being above the subambient temperature and the chiller being fluidly coupled to the dispenser;
chilling the solution to a chilled temperature at or below the subambient temperature with a chiller;
repetitively measuring the temperature of the chilled solution at an exit of the chiller with a first temperature sensor;
repetitively measuring the temperature of the solution at the dispenser with a second temperature sensor;
upon the temperature measured by the first temperature sensor being above the subambient temperature, increasing the chilling of the solution in the chiller; and
upon the temperature measured by the second temperature sensor being within a predetermined range of the freezing point of the solution, decreasing the chilling of the solution by the chiller.
21 . A system for cleaning a substrate comprising:
a rotatable support for supporting a substrate in a substantially horizontal orientation;
a source of a cleaning solution comprising a liquid and a gas;
a nozzle for applying a film of the cleaning solution to a surface of a substrate positioned on the support;
a transmitter adapted to be positioned in contact with the film of the cleaning solution, the transmitter acoustically coupled to one or more transducers;
a supply line fluidly coupling the the source of the cleaning solution to the nozzle;
a chiller operably coupled to the fluid line, the chiller having an inlet and an exit, the chiller adapted to chill the cleaning solution passing therethrough;
a first temperature sensor operably coupled to the fluid line at the nozzle;
a second temperature sensor operably coupled to the fluid line at the exit of the chiller; and
a controller operably coupled to the chiller, the first temperature sensor and the second temperature sensor, the controller programmed to: (1) upon receiving a signal from the first temperature sensor indicative of the cleaning solution being at a temperature above a desired subambient temperature, increasing the chilling of the cleaning solution in the chiller; and (2) upon receiving a signal from the second temperature sensor indicative of the cleaning solution being at a temperature within a predetermined range of the freezing point of the cleaning solution, decreasing the chilling of the solution by the chiller.
22 . The system of claim 21 wherein the subambient temperature is a temperature that results in the cleaning solution being within 3 kg/m 3 of the cleaning solution's maximum density
23 . The system of claim 21 wherein the source of cleaning solution is a gasifier for dissolving the gas into the liquid or a reservoir of the cleaning solution.
24 . The system of claim 21 wherein the predetermined range is 1 ° C. to 10 ° C. above the freezing point of the cleaning solution.
25 . The system of claim 24 wherein the predetermined range is 3° C. to 5° C. above the freezing point of the cleaning solution.
26 . The system of claim 21 wherein the subambient temperature is at or near a temperature that results in the cleaning solution being at or near the cleaning solution's minimum specific volume.
27 . The system of claim 1 wherein the cleaning solution is an aqueous solution and the subambient temperature is between 2° C. to 10° C.
28 . The system of claim 27 wherein the subambient temperature is at or near 4° C.
29 . A system for cleaning a substrate comprising:
a support for supporting at least one substrate in a process chamber;
a source of a cleaning solution comprising a liquid and a gas;
means for introducing the cleaning solution into the process chamber and in contact with a surface of a substrate positioned in the process chamber;
means for supplying sonic energy to a substrate positioned in the process chamber;
a supply line fluidly coupling the the source of the cleaning solution to the introduction means;
a chiller operably coupled to the fluid line, the chiller having an inlet and an exit, the chiller adapted to chill the cleaning solution passing therethrough;
a first temperature sensor operably coupled to the fluid line at the introduction means;
a second temperature sensor operably coupled to the fluid line at the exit of the chiller; and
a controller operably coupled to the chiller, the first temperature sensor and the second temperature sensor, the controller programmed to: (1) upon receiving a signal from the first temperature sensor indicative of the cleaning solution being at a temperature above a desired subambient temperature, increasing the chilling of the cleaning solution in the chiller; and (2) upon receiving a signal from the second temperature sensor indicative of the cleaning solution being at a temperature within a predetermined range of the freezing point of the cleaning solution, decreasing the chilling of the solution by the chiller.