Controlled spalling using a reactive material stack
View Patent ↗A reactive material stack is formed above a surface of a base substrate. The reactive material stack includes metals which when subjected to heat energy or electrical energy can undergo a solid state reaction that provides an intermetallic compound. The intermetallic compound that forms has a smaller unit volume than the initial reactive material stack and, as such, induces a tensile stress within the base substrate which, in turn, initiates crack formation within the base substrate. This represents an initial stage of spalling. The crack formation can be propagated along a fracture plane within the base substrate by continued spalling.
1. A method for removing a material portion of a base substrate, said method comprising:
forming a reactive material stack comprising 2n metal layers above a surface of a base substrate, wherein n is from 1 to 1000; and
removing an upper portion of said base substrate by spalling to provide a spalled material portion, wherein said spalling comprises initiating a solid state reaction of said 2n metal layers of said reactive material stack to provide an intermetallic compound layer of said 2n metal layers of said reactive material stack that induces a tensile stress within said base substrate and causes crack initiation within said base substrate.
2. The method of claim 1 , further comprising forming an edge exclusion material on said surface and at each vertical edge of said base substrate prior to forming said reactive material stack.
3. The method of claim 2 , wherein said edge exclusion material comprises a photoresist material, a polymer, a hydrocarbon material, an ink, a metal, or a paste.
4. The method of claim 1 , further comprising forming a stressor layer above said surface of said base substrate prior to forming said reactive material stack.
5. The method of claim 4 , wherein said stressor layer comprises a metal, a polymer, a spalling inducing tape or any combination thereof.
6. The method of claim 1 , further comprises forming a dielectric layer disposed between said base substrate and said reactive material stack.
7. The method of claim 1 , further comprising forming a handle substrate on an exposed surface of said reactive material stack prior to spalling.
8. The method of claim 7 , wherein said spalling further comprises pulling or peeling said handle substrate.
9. The method of claim 1 , wherein said initiating said solid state reaction of said 2n metal layers of said reactive material stack to provide said intermetallic compound layer comprises applying heat energy from an external heat source to said reactive material stack.
10. The method of claim 1 , wherein said initiating said solid state reaction of said 2n metal layers of said reactive material stack to provide said intermetallic compound layer comprises applying electrical energy from an external electrical energy source to said reactive material stack.
11. The method of claim 1 , wherein said spalling further comprises crack propagation though said base substrate, said crack propagation is performed at room temperature.
12. The method of claim 1 , further comprising removing said intermetallic compound layer from said spalled material portion.
13. The method of claim 1 , further comprising patterning said reactive material stack to provide at least one reactive material stack above said surface of said base substrate prior to spalling.
14. The method of claim 1 , wherein said reactive material stack comprises Ni/Al, Ti/Al, Ni/Si or any multilayered stack thereof.
15. The method of claim 1 , wherein a lower portion of said reactive material stack constituents in part, or entirely, of a metal stressor layer.
16. The method of claim 1 , further comprising bonding an exposed surface of said spalled material portion of said base substrate to a substrate.
17. The method of claim 16 , wherein a material removal process is performed either before bonding or after bonding to expose another surface of spalled material portion of said base substrate.
18. The method of claim 1 , wherein said intermetallic compound layer has a smaller unit volume as compared to the unit volume of said reactive material stack.
19. The method of claim 1 , wherein said intermetallic compound layer comprises a Ni—Al alloy, a Ti—Al alloy, a Ni—Si alloy, a Ni—Ti—Al alloy, a Ni—Ti—Al—Si alloy, a Ni—Al—Si alloy or a Ni—Ti—Si alloy.