Lithography system, method of heat dissipation and frame
View Patent ↗The present invention relates to a lithography system for projecting an image or an image pattern on to a target such as a wafer. Energy that is accumulated in the target by the projection of the image or image pattern is removed from said target, such that expansion by local and/or overall heating is limited to a relevant pre-defined value, and wherein such heat removal is realised by the use of a phase transition in a heat absorbing material that is brought into thermal contact with said target. As a further elaboration, such material may be applied in combination with a further material having a superior coefficient of heat transport, and may be incorporated in an emulsion comprising a material having a superior coefficient of heat transfer. Said material may e.g. be adhered to a bottom face of the target, and may also be included in a frame.
1. A lithography system for projecting an image or an image pattern onto a target, the system comprising:
a target carrier comprising:
a cavity containing a phase change material and an internal heat-conducting frame, and
a top layer and a bottom layer interconnected by the internal heat-conducting frame, wherein:
the top layer includes a surface having heat-conducting burls that support the target and thermally connect the target with the phase change material,
the bottom layer forms a flat reference plane for the top layer, and
the phase change material and the burls are configured to remove heat from the target in such a manner that expansion caused by local and/or overall heating of said target is limited to a relevant pre-defined value.
2. The system according to claim 1 , wherein the percentage of the surface that is made up of the burls is within the range of around 1% to around 5%.
3. The system according to claim 1 , wherein a contacting surface of the phase change material is substantially larger than a target surface that is to be processed.
4. The system according to claim 1 , wherein the burls comprise silicon.
5. The system according to claim 1 , wherein the phase change material has a phase transition from a solid state to a liquid state at a temperature corresponding to that of the operational temperature of the lithography system.
6. The system according to claim 5 , wherein the operational temperature is within a range of 20 to 25 degrees Celsius.
7. The system according to claim 1 , wherein the burls are integrated with at least part of said top layer.
8. The system according to claim 7 , wherein a phase retaining fluid or paste is provided between said burls for optimizing a clamping force between the target and the target carrier.
9. The system according to claim 1 , wherein the internal heat-conducting frame comprises rectangular structures, the rectangular structures being filled with the phase changed material within the range of 60% to 90% of the surface area of each rectangular structure.
10. The system according to claim 1 , wherein the burls are provided with a thermally conducting layer.
11. A wafer carrier comprising:
a cavity containing a phase change material and an internal heat-conducting frame, and
a first and a second wafer-like element interconnected by the internal heat-conducting frame, wherein:
the first wafer-like element includes a surface that is provided with heat-conducting burls that support a target and thermally connect the target with the phase change material,
the second wafer-like element forms a flat reference plane for the first wafer-like element, and
the phase change material and the burls are configured to remove heat from the target in such a manner that expansion caused by local and/or overall heating of said target is limited to a relevant pre-defined value.
12. The wafer carrier of claim 11 , wherein the burls comprise silicon.
13. The wafer carrier of claim 11 , wherein the percentage of the surface that is made up of the burls is within the range of around 1% to around 5%.
14. The wafer carrier of claim 11 , wherein the surface is configured to receive a fluid or paste between the surface and the target.
15. The wafer carrier of claim 11 , wherein the burls are provided with a thermally conducting layer.
16. The wafer carrier of claim 11 , wherein the phase change material has a phase transition from a solid state to a liquid state at a temperature corresponding to that of the operational temperature of the lithography system.
17. The wafer carrier of claim 16 , wherein the operational temperature is within a range of 20 to 25 degrees Celsius.