Method for laser thermal processing using thermally induced reflectivity switch
First Claim
1. A method for controlling the amount of heat transferred to a process region of a semiconductor workpiece when exposed to laser radiation, comprising the steps of:
- covering one or more process regions of the workpiece with an absorber layer;
forming, atop the absorber layer, a reflectivity switch layer that changes reflectivity at a temperature close to a maximum critical temperature at the workpiece process region;
laser irradiating the reflectivity switch layer; and
stripping the reflectivity switch and absorber layers from the workpiece;
wherein the amount of heat absorbed by the absorber layer from laser radiation incident the absorber layer coming through the reflectivity switch layer, and the heat transferred to the one or more process regions is limited by the reflectivity switch layer changing reflectivity.
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Abstract
Method for controlling heat transferred to a workpiece (W) process region (30) from laser radiation (10) using a thermally induced reflectivity switch layer (60). A film stack (6) is formed having an absorber layer (50) atop the workpiece with a portion covering the process region. The absorber layer absorbs and converts laser radiation into heat. Reflective switch layer (60) is deposited atop the absorber layer. The reflective switch layer comprises one or more layers, e.g. thermal insulator and reflectivity transition layers. The reflective switch layer covering the process region has a temperature related to the temperature of the process region. Reflectivity of the switch layer changes from a low to a high reflectivity state at a critical temperature of the process region, limiting radiation absorbed by the absorber layer by reflecting incident radiation when switched. This limits the amount of heat transferred to the process region from the absorber layer.
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Citations
30 Claims
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1. A method for controlling the amount of heat transferred to a process region of a semiconductor workpiece when exposed to laser radiation, comprising the steps of:
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covering one or more process regions of the workpiece with an absorber layer;
forming, atop the absorber layer, a reflectivity switch layer that changes reflectivity at a temperature close to a maximum critical temperature at the workpiece process region;
laser irradiating the reflectivity switch layer; and
stripping the reflectivity switch and absorber layers from the workpiece;
wherein the amount of heat absorbed by the absorber layer from laser radiation incident the absorber layer coming through the reflectivity switch layer, and the heat transferred to the one or more process regions is limited by the reflectivity switch layer changing reflectivity. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
the one or more process regions have an activation temperature and the workpiece has a melting temperature; and
the critical temperature of the reflectivity switch layer is higher than the activation temperature and less than the melting temperature.
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9. The method of claim 1 wherein at least one of the one or more process regions includes doped amorphous silicon.
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10. The method of claim 1, wherein the step of forming the absorber layer includes the step of depositing one or more of the materials from the group of materials comprising:
- titanium, titanium nitride, tantalum, tungsten nitride, silicon dioxide and silicon nitride, with the thickness of any of titanium, titanium nitride, tantalum, tungsten nitride in the range of 10 nm to 1000 nm, and the thickness of either of silicon dioxide and silicon nitride in the range of 1 nm to 30 nm.
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11. A method for controlling the amount of heat transferred to a process region of a semiconductor workpiece when exposed to laser radiation, comprising the steps of:
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covering one or more process regions of the workpiece with an absorber layer of one or more of the materials titanium, titanium nitride, tantalum and tungsten nitride all in a thickness range of 10 nm to 1000 nm and silicon dioxide and silicon nitride in the thickness range of 1 nm to 30 nm;
forming, atop the absorber layer, a reflectivity switch layer, the reflectivity switch layer changing reflectivity at a melting temperature of silicon;
irradiating the workpiece with laser radiation that is absorbed in the absorber layer; and
stripping the reflectivity switch and absorber layers from the workpiece. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 30)
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26. A method for controlling the amount of heat transferred to a process region of a semiconductor substrate when exposed to laser radiation, comprising the steps of:
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providing a substrate with one or more process regions;
covering the one or more process regions with an absorber layer;
covering the absorber layer with a reflectivity switch layer that changes reflectivity from a low-reflectivity state to a high-reflectivity state when the workpiece process region reaches a critical temperature; and
laser irradiating the reflectivity switch layer to bring the workpiece process region to the critical temperature;
wherein the amount of heat absorbed by the absorber layer is from laser radiation incident the absorber layer coming through the reflectivity switch layer, and the heat transferred to the one or more process regions and the reflectivity switch layer is limited when the reflectivity switch layer changes to the high-reflectivity state. - View Dependent Claims (27, 28, 29)
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Specification