Method of protecting a mounting tape during laser singulation of a wafer
View Patent ↗A method of singulating a semiconductor wafer with laser energy while the semiconductor wafer is supported on a mounting tape during singulation comprises the step of depositing a coating material onto a portion of the mounting tape adjacent to a perimeter of the semiconductor wafer to form a protective layer over the mounting tape. The semiconductor wafer is then cut with a laser beam such that the laser beam at least partially impinges upon the protective layer during cutting of the semiconductor wafer. After singulation of the semiconductor wafer, the protective layer is removed from the mounting tape.
1. A method of singulating a semiconductor wafer with laser energy while the semiconductor wafer is supported on a mounting tape during singulation, the method comprising the steps of:
depositing a coating material directly onto a portion of the mounting tape adjacent to a perimeter of the semiconductor wafer to form a protective layer covering the mounting tape, the protective layer being deposited with a predetermined thickness sufficient to protect the mounting tape from being cut by the laser beam;
cutting the semiconductor wafer with a laser beam such that the laser beam at least partially impinges upon the protective layer covering the mounting tape during cutting of the semiconductor wafer; and thereafter
removing the protective layer from the mounting tape after singulation of the semiconductor wafer.
2. The method as claimed in claim 1 , wherein the coating material is deposited such that the protective layer surrounds a whole perimeter of the semiconductor wafer.
3. The method as claimed in claim 1 , wherein the step of removing the protective layer from the mounting tape comprises the step of washing off the coating material with a liquid.
4. The method as claimed in claim 3 , wherein the liquid is water.
5. The method as claimed in claim 1 , wherein the coating material comprises a material that absorps, reflects and/or scatters the laser beam to reduce a laser intensity that is incident on the mounting tape to a level that is below a damage threshold of the mounting tape.
6. The method as claimed in claim 5 , wherein the coating material is selected from the group consisting of: a poly(vinylalcohol), a poly(vinylacetate), a poly(vinylacrylate), a poly(ethyleneglycol), a wetting agent, a preservative, a surfactant and a colouring agent.
7. The method as claimed in claim 1 , wherein the protective layer has a thickness of at least 10 microns.
8. The method as claimed in claim 1 , wherein the coating material is deposited along the mounting tape for a sufficient distance adjacent to the semiconductor wafer to cover an anticipated run-out area of the laser beam.
9. The method as claimed in claim 1 , wherein the protective layer adjoins the perimeter of the semiconductor wafer.
10. The method as claimed in claim 1 , wherein the step of depositing the coating material on the mounting tape further comprises the step of pumping coating material to a nozzle that is positioned over the mounting tape for controllably dispensing the coating material onto the mounting tape.
11. The method as claimed in claim 10 , further comprising the step of supporting the semiconductor wafer and mounting tape on a supporting chuck, and rotating the supporting chuck, semiconductor wafer and mounting tape relative to the nozzle while dispensing coating material from the nozzle.
12. The method as claimed in claim 1 , further comprising the step of heating the protective layer after dispensation of the coating material so as to accelerate drying of the coating material before cutting the semiconductor wafer.
13. The method as claimed in claim 1 , wherein the laser beam has an ultraviolet wavelength.
14. The method as claimed in claim 1 , wherein the step of cutting the semiconductor wafer further comprises the step of generating additional laser beams for cutting the semiconductor wafer at different points simultaneously.
15. A method of singulating a semiconductor wafer with laser energy while the semiconductor wafer is supported on a mounting tape during singulation, the method comprising the steps of:
depositing a coating material onto a portion of the mounting tape adjacent to a perimeter of the semiconductor wafer to form a protective layer over the mounting tape;
cutting the semiconductor wafer with a laser beam such that the laser beam at least partially impinges upon the protective layer during cutting of the semiconductor wafer; and thereafter
removing the protective layer from the mounting tape after singulation of the semiconductor wafer;
wherein the step of depositing the coating material on the mounting tape further comprises the step of pumping coating material to a nozzle that is positioned over the mounting tape for controllably dispensing the coating material onto the mounting tape; and
further comprising the step of changing a relative distance between the nozzle and the perimeter of the semiconductor wafer so as to deposit the coating material along the mounting tape to cover an anticipated run-out area of the laser beam.
16. The method as claimed in claim 15 , wherein the step of changing the relative distance between the nozzle and the perimeter of the semiconductor wafer comprises the step of moving a pivotable arm on which the nozzle is supported relative to the semiconductor wafer.