Pulsed line beam device processing systems using laser diodes
View Patent ↗Pulsed laser beams provided by laser diodes or arrays of laser diodes are applied to substrates such as amorphous silicon. The optical beam is based on a plurality of beams from respective laser diodes and is shaped, homogenized, and directed to a substrate. Duty cycles of the laser diodes are selected to be less than about 0.2. Exposures are applied to Aft an amorphous silicon layer on a rigid or flexible substrate to produce a polysilicon layer with a mobility of at least 50 cm 2 /Vs.
1. A method, comprising:
selecting a substrate having an amorphous silicon layer;
shaping a pulsed optical beam to form an optical line beam by combining constituent pulsed optical beams from a plurality of laser diodes, wherein wavelengths associated with the laser diodes are between 780 nm and 980 nm and at least two of the plurality of laser diodes have emission wavelengths that differ by at least 25 nm; and
processing the amorphous silicon layer of the substrate by exposing the amorphous silicon layer to the optical line beam so as to produce a polysilicon layer, wherein an exposure area corresponds to the optical line beam cross-sectional area.
2. The method of claim 1 , wherein the pulsed optical beam has a pulse duration T that is between 1 ms and 1 μs and a pulse repetition frequency f that is between 1 kHz and 1 MHz.
3. The method of claim 1 , wherein fT is less than 0.5.
4. The method of claim 1 , wherein fT is less than 0.1.
5. The method of claim 1 , wherein a peak pulse power is at least 10/fT Watts.
6. The method of claim 5 , wherein the peak pulse power is at least 100/fT Watts.
7. The method of claim 6 , wherein the peak pulse power is at least 1000/fT Watts.
8. The method of claim 1 , wherein at least one the plurality of laser diodes is configured to emit a continuous optical beam.
9. The method of claim 1 , further comprising scanning at least one of the optical line beam and the substrate so as to process the substrate.
10. The method of claim 1 , wherein the scanning is configured so that the substrate area receives at least ten sequential optical pulses.
11. The method of claim 1 , wherein the amorphous silicon layer is processed to have a mobility of at least 10 cm 2 /Vs.
12. The method of claim 1 , wherein the amorphous silicon layer is processed to have a mobility of at least 50 cm 2 /Vs.
13. The method of claim 1 , further comprising directing the pulsed optical beam to a light guide configured to homogenize the pulsed optical beam, wherein the homogenized pulsed optical beam is shaped to form the optical line beam.
14. The method of claim 1 , wherein the substrate includes a region that includes a dopant, wherein the optical line beam is applied so as to diffuse the dopant from the doped region.
15. The method of claim 14 , wherein the substrates includes a layer having doped region and the optical line beam is applied so as to diffuse the dopant in the layer.
16. The method of claim 15 , wherein the layer is a doped silicon layer.
17. The method of claim 1 , wherein the substrate is exposed to the optical line beam in the exposure area so as to maintain a temperature of at least 500° C. for between at least 100 ms and 2 s.
18. The method of claim 1 , wherein the substrate is exposed to the optical line beam in the exposure area so as to maintain a temperature of at least 1000° C. for between at least 100 ms and 2 s.
19. The method of claim 1 , wherein the substrate includes a region that includes a dopant, wherein the optical line beam is applied so as to activate the dopant in the doped region.
20. The method of claim 19 , wherein the substrates includes a layer having doped region and the optical line beam is applied so as to activate the dopant in the layer.
21. The method of claim 20 , wherein the layer is a doped silicon layer.
22. The method of claim 1 , further comprising a beam shaping optical system that combines and shapes the constituent pulsed optical beams to form the pulsed optical beam, wherein a duty cycle of the constituent pulsed optical beams is less than about 0.5.
23. The method of claim 22 , wherein the beam shaping optical system includes a beam homogenizer that receives the constituent pulsed optical beams and produces the pulsed optical beam as a homogenized beam.
24. The method of claim 23 , wherein each of the constituent pulsed optical beams is coupled to a corresponding optical fiber that directs the constituent pulsed optical beam to the beam homogenizer.