Semiconductor device separation using a patterned laser projection
View Patent ↗A method for separating a semiconductor wafer into several thousand devices or dies by laser ablation. Semiconductor wafers are initially pre-processed to create multiple devices, such as blue LEDs, on the wafers. The wafers are then mounted with tape coated with a generally high level adhesive. The mounted wafer is then placed on a vacuum chuck (which is itself positioned on a computer controlled positioning table) to hold it in place during the cutting process. The cutting surface is then covered with a protective layer to prevent contamination from the effluent resulting from the actual cutting process. A laser beam is generated and passed through optical elements and masks to create a pattern, such as a line or multiple lines. The patterned laser projection is directed at the wafer at a substantially normal angle and applied to the wafer until at least a partial cut is achieved through it. A mechanical separation process completes the separation when only a partial cut is achieved by the patterned laser projection. The dies are then transferred to a grip ring for further processing.
1. A method for scribing a semiconductor wafer, said method comprising the steps of:
directing a patterned laser projection at a surface of said semiconductor wafer, said semiconductor wafer comprising a sapphire substrate and a device layer; and
applying said patterned laser projection with a given set of parameters until at least a partial cut in said semiconductor wafer is obtained.
2. The method of claim 1 , wherein said device layer comprises a nitride device layer.
3. The method of claim 1 , wherein said sapphire substrate has a bandgap value greater than an energy value for the patterned laser projection.
4. The method of claim 1 , wherein said sapphire substrate has a C-plane orientation.
5. The method of claim 1 , wherein said patterned laser projection is one selected from the group consisting of long lines, multiple lines, multiple parallel lines and grids.
6. The method of claim 1 , wherein said surface is a back/substrate surface of said semiconductor wafer.
7. The method of claim 1 , wherein said surface is a front/epitaxial surface of said semiconductor wafer.
8. The method of claim 1 , wherein a kerf width is less than 10 micrometers for minimizing wastage of said semiconductor wafer.
9. The method of claim 1 , wherein a kerf width is less than 20 micrometers for minimizing wastage of said semiconductor wafer.
10. The method of claim 1 , wherein a kerf width is less than 100 micrometers for minimizing wastage of said semiconductor wafer.
11. The method of claim 1 , wherein a kerf width is less than 20 micrometers and no more than 28 micrometers for minimizing wastage of the semiconductor wafer.
12. The method of claim 1 , wherein said partial cut is less than 3.5 mils in depth.
13. The method of claim 1 , wherein said step of directing includes the step of generating laser light emissions capable of cutting the sapphire substrate via laser ablation.
14. The method of claim 1 , wherein said device layer comprises gallium nitride.
15. The method of claim 1 , wherein said device layer comprises gallium arsenide.
16. The method of claim 1 , wherein said device layer comprises aluminum nitride.
17. The method of claim 1 , wherein said device layer comprises indium nitride.
18. The method of claim 1 , wherein said device layer comprises silicon.
19. The method of claim 1 , wherein said device layer comprises III-V material.
20. A method for scribing a semiconductor wafer, said method comprising the steps of:
directing a patterned laser projection at a surface of said semiconductor wafer, said semiconductor wafer comprising a sapphire substrate and a device layer; and
applying said patterned laser projection with a given set of parameters until at least a partial cut in said semiconductor wafer is obtained,
wherein said patterned laser projection is incident substantially normal with said surface.
21. The method of claim 20 , wherein said device layer comprises a nitride device layer.
22. The method of claim 20 , wherein said sapphire substrate has a bandgap value greater than an energy value for the laser projection.
23. The method of claim 20 , wherein said sapphire substrate has a C-plane orientation.
24. The method of claim 20 , wherein said patterned laser projection is one selected from the group consisting of long lines, multiple lines, multiple parallel lines and grids.
25. The method of claim 20 , wherein said step of applying further includes the step of positioning a positioning table with respect to said laser projection to permit cutting along different axes and different sections of said semiconductor wafer.
26. The method of claim 20 , wherein a magnitude of an incidence angle between said laser projection and said surface is less than 4°.
27. The method of claim 20 , wherein said semiconductor wafer has a substrate selected from the group consisting of sapphire, III-V materials, and refractory ceramics.