Thermally induced phase switch for laser thermal processing
First Claim
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.
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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 (TP). 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.
239 Citations
48 Claims
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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:
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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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27)
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.
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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.
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25. The system of claim 23, wherein the pulsed beam of radiation is focused to a line.
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26. The system of claim 23, wherein the pulsed beam of radiation is focused to a point.
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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.
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28. A method of controlling the amount of heat transferred to a process region of a workpiece, comprising:
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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. - View Dependent Claims (29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42)
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43. A method, comprising:
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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. - View Dependent Claims (44, 45, 46, 47, 48)
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Specification