Heated single wafer megasonic processing plate

Abstract

A method and apparatus for heating a megasonic wafer processing plate to approximate the temperature of the processing liquid, whereby the chemical processing of the wafer is optimized. Heater blankets may be secured to the back side of the megasonic plate, or internal heating elements or passages may be disposed within the plate.

Description

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a plan view of a wafer disposed to undergo megasonic processing in conjunction with a megasonic resonator process plate.

FIG. 2 is a cross-sectional elevation taken along line 2-2 of FIG. 1, showing one embodiment of the heated single wafer megasonic processing assembly of the present invention.

FIG. 3 is a bottom plan view of the megasonic processing assembly depicted in FIG. 2.

FIG. 4 is a cross-sectional elevation similar to FIG. 2, depicting a further embodiment of the heated single wafer megasonic processing assembly of the present invention.

FIG. 5 is a bottom plan view of the megasonic processing assembly depicted in FIG. 4.

FIG. 6 is a cross-sectional elevation similar to FIG. 4, depicting a further embodiment of the heated single wafer megasonic processing assembly of the present invention.

FIG. 7 is a bottom plan view of the megasonic processing assembly depicted in FIG. 6.

FIG. 8 is a cross-sectional elevation similar to FIG. 6, depicting a further embodiment of the heated single wafer megasonic processing assembly of the present invention.

FIG. 9 is a bottom plan view of the megasonic processing assembly depicted in FIG. 8.

FIG. 10 is a cross-sectional elevation similar to FIG. 8, depicting a further embodiment of the heated single wafer megasonic processing assembly of the present invention.

FIG. 11 is a bottom plan view of the megasonic processing assembly depicted in FIG. 10.

FIG. 12 is a cross-sectional elevation depicting a typical manner of supporting a single wafer in conjunction with any of the embodiments of the heated megasonic processing assembly of the present invention.

FIG. 13 is a graph depicting process liquid temperature versus location on a megasonic transducer plate, comparing the temperature gradient of a typical prior art plate and the present invention.

FIG. 14 is a graph depicting temperature differences at specific plate locations versus time for a megasonic transducer plate, comparing a typical prior art plate and the present invention.

FIG. 15 is a graph depicting temperature versus time in a typical prior art megasonic process using an unheated megasonic transducer plate.

FIG. 16 is a graph depicting temperature versus time of a megasonic process using the heated megasonic transducer plate of the invention.

Claims

1. A megasonic transducer processing plate assembly for wafer processing, said plate assembly having a front surface in close proximity to a wafer undergoing processing, and an back surface, and a central opening for delivering process liquid to said wafer;heating means for heating said processing plate to approximate the elevated temperature of the process liquid,said heating means including at least one heater blanket secured to said back surface of said processing plate.

2. The megasonic transducer processing plate assembly of claim 1, wherein said heating means includes a plurality of said heater blankets disposed in a patch-like array on said back surface of said processing plate.

3. The megasonic transducer processing plate assembly of claim 1, wherein said heating means includes a pair of heater blankets, each forming a portion of an annular shape and disposed in combination to define an annular heating assembly.

4. The megasonic transducer processing plate assembly of claim 1, wherein said heating means includes a pair of heater blankets, each forming a portion of a disk-like shape and disposed in combination to extend over a substantial portion of said back surface.

5. The megasonic transducer processing plate assembly of claim 1, wherein said heater blanket includes an etched-foil resistive pad.

6. The megasonic transducer processing plate assembly of claim 5, further including an alumina silica insulation pad joined to an outer surface of said resistive pad.

7. The megasonic transducer processing plate assembly of claim 6, further including a PVDF panel secured to an outer surface of said insulation pad.

8. The megasonic transducer processing plate assembly of claim 1, further including a plurality of said heater blankets arranged on said back surface to distribute thermal energy to said processing plate in an optimally uniform manner.

9. A megasonic transducer processing plate assembly for wafer processing in a liquid bath, said plate assembly having a front surface in close proximity to a wafer undergoing processing, and an back surface, and a central opening for delivering process liquid to said wafer;heating means for heating said processing plate to approximate the elevated process temperature of the liquid,said heating means being embedded within said processing plate.

10. The megasonic transducer processing plate assembly of claim 9, wherein said heating means includes at least one resistance heating rod embedded in said processing plate.

11. The megasonic transducer processing plate assembly of claim 10, further including a plurality of said resistance heating rods arrayed in said processing plate to distribute thermal energy to said processing plate in an optimally uniform manner.

12. The megasonic transducer processing plate assembly of claim 9, wherein said heating means includes at least one flow passage embedded in said processing plate and arranged to be connected to a source of heated fluid.

13. The megasonic transducer processing plate assembly of claim 12, further including a plurality of said flow passages embedded in said processing plate and connected to define a continuous flow path therethrough, said flow passages arrayed in said processing plate to distribute thermal energy to said processing plate in an optimally uniform manner.

14. A method for megasonic processing of wafers in a liquid bath, including the steps of: providing a megasonic processing plate in close proximity to one surface of a wafer;heating said processing plate to a temperature approximating the process temperature of said liquid;pumping processing liquid through an opening in said processing plate toward said one surface of said wafer.

15. The method for megasonic processing of claim 14, wherein said heating step includes securing at least one heater blanket to said megasonic plate to distribute thermal energy to said processing plate in an optimally uniform manner.

16. The method for megasonic processing of claim 14, wherein said heating step including providing an embedded heater in said processing plate to distribute thermal energy to said processing plate in an optimally uniform manner.

17. The method for megasonic processing of claim 16, wherein said embedded heater includes at least one resistance heating rod secured within said megasonic processing plate.

18. The method for megasonic processing of claim 16, wherein said embedded heater includes at least one flow passage within said megasonic processing plate and connected to a source of heated fluid.