Supercritical CO2 cleaning system and method

Abstract

A supercritical CO2 cleaning system is provided, comprising: a closed high-pressure cleaning trough, which is a funnel-shaped vessel tapered from top to bottom; a bearer platform, located within the closed high-pressure cleaning trough and rotated with respect to an object to be cleaned and used for bearing the object to be cleaned; and a movable nozzle set, disposed within the closed high-pressure cleaning trough and above the bearer platform, wherein the object to be cleaned can be cleaned via the movable nozzle set and impurity pollutants will be easily deposited at the bottom of the closed high-pressure cleaning trough after cleaning. A supercritical CO2 cleaning method is also provided, comprising: providing a wafer or an object to be cleaned within a closed high-pressure cleaning trough; introducing liquid CO2 into the closed high-pressure cleaning trough; adding co-solvents and surfactants into the cleaning trough; activating a movable nozzle set in order to increase the cleaning performance; rotating the wafer or the object to be cleaned to remove the impurity pollutants; and lowering the pressure to discharge the CO2 and the impurity pollutants in order to clean the wafer or the object to be cleaned.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a supercritical CO₂ cleaning system according to the present invention.

FIG. 2 is a flow chart of a supercritical CO₂ cleaning method according to the present invention.

FIG. 3A to 3D are cross-sectional views of a ultrasonic convergent nozzle of the supercritical CO₂ cleaning system according to the present invention.

FIG. 4A to 4D are top views of a movable nozzle set of the supercritical CO₂ cleaning system according to the present invention. FIG. 5 illustrates a diagram for the cleaning principle of a supercritical CO₂ according to the present invention.

Claims

1. A supercritical CO2 cleaning system, comprising: a closed high-pressure cleaning trough, which is a funnel-shaped vessel tapered from top to bottom;a bearer platform, located within said closed high-pressure cleaning trough and rotated with respect to an object to be cleaned and used for bearing said object to be cleaned; anda movable nozzle set, disposed within said closed high-pressure cleaning trough and above said bearer platform,wherein said object to be cleaned can be cleaned via said movable nozzle set and impurity pollutants will be easily deposited at the bottom of said closed high-pressure cleaning trough after cleaning.

2. The supercritical CO2 cleaning system as claimed in claim 1, wherein said bearer platform is titled with respect to the horizontal plane with an angle formed therebetween, during the cleaning, the impurity pollutants can easily and regularly flow away from said object to be cleaned along the angle and reach the bottom of said trough.

3. The supercritical CO2 cleaning system as claimed in claim 1, wherein said movable nozzle set is the combination of at least one movable nozzle and at least one ultrasonic oscillator having the frequency of 0.8 MHz˜3.5 MHz, said ultrasonic oscillator may form a module together with said movable nozzle, or said ultrasonic oscillator is combined with said bearer platform by mounting it above or beneath said bearer platform.

4. The supercritical CO2 cleaning system as claimed in claim 3, wherein said ultrasonic oscillator is convergent or non-convergent, the ultrasonic body of said convergent ultrasonic oscillator may form a concave or an additional horn-shaped nozzle is provided in order to achieve the convergence, such that when the supercritical CO2 flows into said closed high-pressure cleaning trough, it can inject out via said movable nozzle and perform an ultrasonic cleaning.

5. The supercritical CO2 cleaning system as claimed in claim 3, wherein said ultrasonic oscillator is disposed at a suitable angle with respect said object to be cleaned, such that the impurity pollutants on said object to be cleaned can easily and rapidly leave away.

6. The supercritical CO2 cleaning system as claimed in claim 3, wherein the operation conditions are as follows: the operation temperature is between 15° C.˜150° C., the operation pressure is between 50˜250 atm, and the operation frequency range of the ultrasonic set is between 0.8 MHz˜3.5 MHz.

7. The supercritical CO2 cleaning system as claimed in claim 3, wherein within said movable nozzle set, the ultrasonic oscillator pipes, the movable nozzle pipes, and the bearer platform pipes are embedded within a high-pressure tube, such that a second pollution on said object to be cleaned can be avoided.

8. The supercritical CO2 cleaning system as claimed in claim 3, wherein said object to be cleaned is a wafer, low-k material, or MEMS.

9. A supercritical CO2 cleaning method comprising: providing a wafer or an object to be cleaned within a closed high-pressure cleaning trough;introducing liquid CO2 into said closed high-pressure cleaning trough;adding co-solvents and surfactants into said cleaning trough;activating a movable nozzle set in order to increase the cleaning performance;rotating said wafer or said object to be cleaned to remove the impurity pollutants; andlowering the pressure to discharge the CO2 and the impurity pollutants.

10. The supercritical CO2 cleaning method as claimed in claim 9, wherein after the CO2 and the impurity pollutants are discharged, another cleaning can be performed by fresh CO2, and said wafer or said object to be cleaned can be taken out after this another cleaning.

11. The supercritical CO2 cleaning method as claimed in claim 10, wherein said wafer or said object to be cleaned is titled with respect to the horizontal plane with an angle formed therebetween, during the cleaning, the impurity pollutants can be easily and regularly discharged.

12. The supercritical CO2 cleaning method as claimed in claim 10, wherein said movable nozzle set is the combination of at least one movable nozzle and at least one ultrasonic oscillator having the frequency of 0.8 MHz˜3.5 MHz, said ultrasonic oscillator may form a module together with said movable nozzle by mounting it above or additionally underneath said object to be cleaned in order to increase the cleaning performance.

13. The supercritical CO2 cleaning method as claimed in claim 12, wherein said ultrasonic oscillator of said movable nozzle set is disposed at a suitable angle with respect said object to be cleaned, such that the impurity pollutants on said object to be cleaned can easily and rapidly leave away.

14. The supercritical CO2 cleaning method as claimed in claim 3, wherein the operation conditions are as follows: the operation temperature is between 15° C.˜150° C., the operation pressure is between 50˜250 atm, and the operation frequency range of the ultrasonic set is between 0.8 MHz˜3.5 MHz.

15. The supercritical CO2 cleaning method as claimed in claim 12, wherein said object to be cleaned is a wafer, low-k material, or MEMS.

16. The supercritical CO2 cleaning method as claimed in claim 12, wherein the cleaning can be performed in conjunction with the micro-emulsification technology by adding co-solvents, surfactants and chelating agents in order to increase the cleaning performance.

17. The supercritical CO2 cleaning method as claimed in claim 12, wherein the work range of said movable nozzle set covers the whole surface of said object to be cleaned, such that said object to be cleaned can be uniformly cleaned.

18. The supercritical CO2 cleaning method as claimed in claim 12, wherein the respective working ranges of a plurality of ultrasonic waves and a plurality of nozzles in said movable nozzle set overlap with one another, such that any uncleaned areas can be avoided.