Method and apparatus for debonding temporarily bonded wafers in wafer-level packaging applications
A method for debonding a wafer from a bonded wafer stack is disclosed. Initially, a light-absorbing layer is placed on a carrier. A wafer is then attached to the light-absorbing layer of the carrier via an adhesive layer to form a bonded wafer stack. After processing the wafer has been processed, a light pulse from a flashlamp is applied to a non-wafer side of the carrier to heat the light-absorbing layer and the adhesive layer in order to loosen the wafer from the bonded wafer stack. Finally, the wafer is removed from the bonded wafer stack.
1 . A method for debonding a wafer from a bonded wafer stack, said method comprising:
placing a light-absorbing layer on a carrier, wherein said light-absorbing layer includes a metal alloy having approximately 90% tungsten and approximately 10% titanium;
attaching a wafer to said light-absorbing layer of said carrier via an adhesive layer to form a bonded wafer stack;
processing said wafer;
applying a light pulse from a flashlamp to a non-wafer side of said carrier to heat said light-absorbing layer and said adhesive layer in order to loosen said wafer from said bonded wafer stack; and
removing said wafer from said bonded wafer stack.
2 . The method of claim 1 , wherein placing the light-absorbing layer comprises placing said light-absorbing layer on said carrier that is transparent.
3 . The method of claim 1 , wherein placing the light-absorbing layer comprises placing said light-absorbing layer on said carrier that is made of glass.
4 . The method of claim 1 , wherein placing the light-absorbing layer comprises placing said light-absorbing layer on said carrier via sputtering, thermal evaporation, atomic layer deposition or vapor deposition.
5 . The method of claim 1 , wherein said processing includes thinning said wafer.
6 . The method of claim 1 , wherein said processing includes building electronic components on said wafer.
7 . The method of claim 1 , wherein a difference in coefficients of thermal expansion between said light-absorbing layer and said carrier is within 1.5×10 −6 /K.
8 . The method of claim 1 , wherein the light-absorbing layer has a thickness between about 100 nm and about 300 nm.
9 . The method of claim 8 , wherein the light-absorbing layer has a thickness between about 150 nm and about 250 nm.
10 . The method of claim 9 , wherein the light-absorbing layer has a thickness of about 200 nm.
11 . The method of claim 1 , wherein the step of removing said wafer comprises applying distributed pressure across said wafer.
12 . The method of claim 1 , comprising applying a second light pulse from the flashlamp to heat said light-absorbing layer and said adhesive layer in order to loosen said wafer from said bonded wafer stack.
13 . The method of claim 12 , further comprising conveying the bonded stack relative to the flashlamp between the first and second light pulses.
14 . The method of claim 12 , further comprising using a switching device and a frequency controller to regulate the pulses of light from the flashlamp.