Thermally induced phase switch for laser thermal processing

• US 6,479,821 B1
• Filed: 09/11/2000
• Issued: 11/12/2002
• Est. Priority Date: 09/11/2000
• Status: Expired due to Term

• Current Assignee: Veeco Instruments Incorporated
• Original Assignee: Ultratech Stepper, Inc. (Veeco Instruments Incorporated)
• Inventors: Thompson, Michael O., Talwar, Somit, Wang, Yun, Markle, David A., Hawryluk, Andrew M.
• Primary Examiner(s): Lee, John R.
• Assistant Examiner(s): SMITH, JOHNNIE L
• Application Number:
  US09/659,094
• Time in Patent Office: 792 Days
• Field of Search: 250/316.1, 438/530, 438/199, 438/535, 438/533, 438/655
• US Class Current: 250/316.1
• CPC Class Codes: G03G 5/16 Layers for recording by changing the magnetic properties, e.g. for Curie-point-writing
• CPC Class Codes: H01L 21/268 using electromagnetic radiation, e.g. laser radiation

Abstract

A method, apparatus and system for controlling the amount of heat transferred to a process region (30) of a workpiece (W) from exposure with a pulse of radiation (10), which may be in the form of a scanning beam (B), using a thermally induced phase switch layer (60). The apparatus of the invention is a film stack (6) having an absorber layer (50) deposited atop the workpiece, such as a silicon wafer. A portion of the absorber layer covers the process region. The absorber layer absorbs radiation and converts the absorbed radiation into heat. The phase switch layer is deposited above or below the absorber layer. The phase switch layer may comprise one or more thin film layers, and may include a thermal insulator layer and a phase transition layer. Because they are in close proximity, the portion of the phase switch layer covering the process region has a temperature that is close to the temperature of the process region. The phase of the phase switch layer changes from a first phase (e.g., solid) to a second phase (e.g., liquid or vapor) at a phase transition temperature (T_P). During this phase change, the phase switch layer absorbs heat but does not significantly change temperature. This limits the temperature of the absorber layer and the process region since both are close to the phase change layer.

Claims

1. An apparatus for controlling the amount of heat delivered to a process region in a workpiece when the workpiece is exposed to radiation, comprising:

an absorber layer formed atop the workpiece and covering the process region, the absorber layer capable of absorbing radiation and converting the radiation to heat;

a phase switch layer formed adjacent the absorber layer and having a phase change temperature, wherein below the phase change temperature the phase switch allows a substantial amount of the radiation to be absorbed by the absorber layer, and at the phase change temperature the phase switch layer undergoes a phase change that allows the phase switch layer to absorb a substantial amount of the radiation and/or heat without a corresponding increase in temperature.

2. The apparatus of claim 1, wherein the process region has an activation temperature, and wherein the phase change temperature corresponds to the activation temperature.

3. The apparatus of claim 1, wherein the process region has an activation temperature, the workpiece has an allowable temperature, and wherein the phase change temperature is between the activation temperature and the workpiece allowable temperature.

4. The apparatus of claim 3, wherein the workpiece allowable temperature is a temperature at which the workpiece melts.

5. The apparatus of claim 1, wherein the phase change temperature is the same as the activation temperature.

6. The apparatus of claim 1, wherein the phase change temperature is less than the activation temperature.

7. The apparatus of claim 1, wherein the phase change temperature is greater than the activation temperature.

8. The apparatus of claim 1, further including a strippable layer between the absorber layer and the workpiece.

9. The apparatus of claim 1, further including a strippable layer between the phase switch layer and the workpiece.

10. The apparatus of claim 1, wherein the process region includes at least one of a source and drain region.

11. The apparatus of claim 1, wherein the process region comprises doped amorphous silicon.

12. The apparatus of claim 1, wherein the absorber layer includes at least one of titanium, tungsten, tantalum, silicon dioxide, silicon nitride, and titanium nitride.

13. The apparatus of claim 1, wherein the phase switch layer includes polyimide.

14. The apparatus of claim 13, wherein the phase switch layer includes a layer of silicon dioxide adjacent the absorber layer.

15. The apparatus of claim 14, wherein the silicon dioxide layer has a thickness between 10 nanometers and 250 nanometers, and the polyimide layer has a thickness between 10 nanometers and 20 microns.

16. The apparatus of claim 1, wherein the phase switch layer includes aluminum arsenide.

17. The apparatus of claim 16, wherein the phase switch layer includes a layer of silicon dioxide adjacent the absorber layer.

18. The apparatus of claim 17, wherein the silicon dioxide layer has a thickness between 10 nanometers and 250 nanometers, and the aluminum arsenide layer has a thickness between 10 nanometers and 20 microns.

19. The apparatus of claim 1, wherein below the phase change temperature the phase switch layer is solid, and at the phase change temperature the phase switch layer starts to melt.

20. The apparatus of claim 1, wherein below the phase change temperature the phase switch layer is solid, and at the phase change temperature the phase switch layer starts to vaporize.

21. The apparatus of claim 1, wherein the phase switch layer is formed above the absorber layer.

22. The apparatus of claim 1, wherein the phase switch layer is formed below the absorber layer.

23. A system comprising:

a workpiece support member adapted to support a workpiece;

a radiation source arranged adjacent the workpiece support member and capable of providing a pulsed beam of radiation to the workpiece; and

the apparatus of claim 1 formed on the workpiece.

24. The system of claim 23, wherein the radiation source is capable of scanning the pulsed beam of radiation across at least a portion of the workpiece.

25. The system of claim 23, wherein the pulsed beam of radiation is focused to a line.

26. The system of claim 23, wherein the pulsed beam of radiation is focused to a point.

27. The system of claim 23, wherein the radiation source includes a laser capable of providing the pulsed beam of radiation at a wavelength between 300 nanometers and 1100 nanometers.

28. A method of controlling the amount of heat transferred to a process region of a workpiece, comprising:

forming an absorber layer over the process region;

forming a phase switch layer adjacent the absorber layer, wherein below a phase change temperature the phase switch layer allows a substantial amount of the radiation to be absorbed by the absorber layer, and at the phase change temperature the phase switch layer undergoes a phase change that allows the phase switch layer to absorb a substantial amount of the radiation and/or heat without a corresponding increase in temperature;

irradiating the absorber layer, thereby heating the process region and the phase switch layer; and

terminating the heating of the process region by the phase switch layer changing phase at the phase change temperature.

29. The method of claim 28, wherein the process region has an activation temperature, and including terminating the heating of the process region when the process region reaches the activation temperature.

30. The method of claim 28, wherein the phase change temperature is greater than the activation temperature.

31. The method of claim 28, wherein the workpiece has a melting temperature, and including terminating the heating of the process region at a temperature below the workpiece melting temperature.

32. The method of claim 28, wherein irradiating the absorber layer is performed using pulsed radiation.

33. The method of claim 28, wherein irradiating the absorber layer is performed by scanning a line of radiation across the absorber layer.

34. The method of claim 28, including forming the phase switch layer to include at least one of polyimide and aluminum arsenide.

35. The method of claim 34, including forming the phase switch layer to include a thermal insulating layer.

36. The method of claim 35, including forming the thermal insulating layer to include at least one of silicon dioxide and silicon nitride.

37. The method of claim 35, wherein the thermal insulating layer has a thickness, and including adjusting the thickness so that the phase switch layer reaches the phase change temperature when the process region reaches a select temperature.

38. The method of claim 35, wherein the select temperature is an activation temperature of the process region.

39. The method of claim 28, including forming an antireflection coating atop the absorber layer.

40. The method of claim 28, including forming the absorber layer from at least one of titanium, tungsten, tantalum, silicon dioxide, silicon nitride, and titanium nitride.

41. The method of claim 28, including forming the phase switch layer atop the absorber layer.

42. The method of claim 28, including forming the phase switch layer beneath the absorber layer.

43. A method, comprising:

forming a process region in a semiconductor wafer, the process region comprising amorphous doped silicon and having an activation temperature;

forming an absorber layer adjacent the semiconductor wafer and over the process region;

forming a phase switch layer adjacent the absorber layer, wherein below a phase change temperature the phase switch layer allows a substantial amount of the radiation to be absorbed by the absorber layer, and at the phase change temperature the phase switch layer undergoes a phase change that allows the phase switch layer to absorb a substantial amount of the radiation and/or heat without a corresponding increase in temperature;

irradiating the absorber layer, thereby heating the process region and the phase switch layer;

terminating the heating of the process region by the phase switch layer changing phase at the phase change temperature; and

removing the absorber layer and phase switch layer.

44. The method of claim 43, including forming the phase switch layer to include a thermal insulating layer and a phase transition layer.

45. The method of claim 44, including forming the thermal insulating layer from two or more layers.

46. The method of claim 44, including forming the phase transition layer from at least one of polyimide and aluminum arsenide.

47. The method of claim 43, including forming the phase switch layer atop the absorber layer.

48. The method of claim 43, including forming the phase switch layer beneath the absorber layer.