Method for manufacture of a multi-layer plate device
A method for the joining of ceramic pieces with a hermetically sealed joint comprising brazing a layer of joining material between the two pieces. The wetting and flow of the joining material is controlled by the selection of the joining material, the joining temperature, the joining atmosphere, and other factors. The ceramic pieces may be aluminum nitride and the pieces may be brazed with an aluminum alloy under controlled atmosphere. The joint material is adapted to later withstand both the environments within a process chamber during substrate processing, and the oxygenated atmosphere which may be seen within the shaft of a heater or electrostatic chuck.
1. A method for the manufacture of a ceramic multi-layer plate device used as a plate in an electrostatic chuck, or in a heater, or other wafer support, used in semiconductor wafer processing, said method comprising the steps of:
arranging a plurality of plate components into a stack, wherein said plurality of plate components comprise an upper plate layer, a lower plate layer, and an annular a brazing layer disposed between said upper plate layer and said lower plate layer between the outer periphery of said upper plate layer and said lower plate layer, thereby forming an inner space in said stack between said upper plate layer and said lower plate layer, wherein said upper plate layer comprises ceramic, wherein said lower plate layer comprises ceramic, and wherein said brazing layer comprises at least 89% aluminum by weight;
placing said stack of plate components into a process chamber;
removing oxygen from said process chamber; and
joining said upper plate layer to said lower plate layer, wherein said step of joining said upper plate layer to said lower plate layer comprises the steps of:
applying pressure between said upper plate layer and lower plate layer across said brazing layer; and
heating the stack of plate components to a temperature between 800° C. and 1200° C., thereby joining said upper plate layer to said lower plate layer with a hermetically sealed joint which hermetically seals said inner space from an area exterior to said plate components, wherein the hermetically sealed joint has a vacuum leak rate of <1×10 −9 sccm He/sec.
2. The method of claim 1 wherein the step of removing oxygen from said process chamber the step of applying vacuum to said stack of plate components during the heating of said stack of plate components, wherein said pressure is lower than 1×10E-4 Torr.
3. The method of claim 1 wherein the step of removing oxygen from said process chamber the step of applying vacuum to said stack of plate components during the heating of said stack of plate components, wherein said pressure is lower than 1×10E-5 Torr.
4. The method of claim 1 wherein said upper plate layer comprises aluminum nitride.
5. The method of claim 2 wherein said brazing layer comprises at least 99% aluminum by weight.
6. The method of claim 4 wherein said lower plate layer comprises aluminum nitride.
7. The method of claim 3 wherein said brazing layer comprises at least 99% aluminum by weight.
8. The method of claim 6 wherein said brazing layer comprises at least 99% aluminum by weight.
9. The method of claim 7 further comprising the step of applying vacuum to said stack of plate components prior to the heating of said stack of plate components, wherein said pressure is lower than 1×10E-4 Torr.
10. The method of claim 7 further comprising the step of applying vacuum to said stack of plate components during the heating of said stack of plate components, wherein said pressure is lower than 1×10E-5 Torr.
11. The method of claim 7 further comprising the step of removing oxygen from said process chamber, wherein said step of removing oxygen comprises purging and re-filling the chamber with pure, dehydrated inert gas.
12. The method of claim 7 further comprising the step of removing oxygen from said process chamber, wherein said step of removing oxygen comprises purging and re-filling the chamber with purified hydrogen.
13. The method of claim 2 wherein said step of heating the stack of plate components to said first temperature comprises heating the stack of plate components for a duration of between 10 minutes and 2 hours.
14. The method of claim 7 wherein said step of applying pressure between said top plate layer and said lower plate layer comprises applying between 1 and 500 psi between said upper plate layer and said lower plate layer.
15. The method of claim 7 wherein said step of applying pressure between said upper plate layer and said lower plate layer comprises applying between 2 and 40 psi between said upper plate layer and said lower plate layer.
16. The method of claim 1 further comprising the steps of:
heating the multi-layer plate device to a temperature above the liquidus temperature of the brazing layer after the step of joining said top plate layer to said lower plate layer; and
disjoining the joint between said top plate layer and said lower plate layer.