Fabrication method of nitride-based semiconductor device

1. A fabrication method of a nitride-based semiconductor device including a structure in which a retention substrate and a stacked structure constituted of a nitride-based semiconductor are united with a bonding metal therebetween, said fabrication method comprising:

forming said stacked structure constituted of said nitride-based semiconductor on a support substrate,

depositing a first bonding metal on said stacked structure, depositing a second bonding metal on said retention substrate, bonding said first bonding metal to said second bonding metal in a state where said first bonding metal and said second bonding metal face each other to unite said retention substrate and said stacked structure, said first bonding metal and said second bonding metal constituting said bonding metal,

separating said support substrate from said stacked structure for removal, and

forming a groove in said stacked structure for chip division after separating said support substrate from said stacked structure,

wherein a continuous surface area, before forming the groove for chip division, of the entire surface of said retention substrate disposed on a side of the second bonding metal is smaller than a continuous surface area, before forming the groove for chip division, of the entire surface of said support substrate disposed on a side of the stacked structure, and

wherein a difference between a span of the support substrate and a span of the retention substrate is greater than a sum of a layer thickness of said first bonding metal and a layer thickness of said second bonding metal.

2. The fabrication method of a nitride-based semiconductor device according to claim 1 , wherein said bonding metal is made to avoid contact with said support substrate.

3. The fabrication method of a nitride-based semiconductor device according to claim 1 , wherein said support substrate has a thickness of not more than 400 μm.

4. The fabrication method of a nitride-based semiconductor device according to claim 1 , wherein said retention substrate is united with said stacked structure over an entire surface area of a side facing said second bonding metal in said bonding.

5. The fabrication method of a nitride-based semiconductor device according to claim 1 , wherein the separating of said support substrate is effected by applying a laser beam from a backside of said support substrate.

6. The fabrication method of a nitride-based semiconductor device according to claim 5 , said method further comprising:

mirror-polishing a face of said support substrate to which said laser beam is to be applied, prior to said separating of the support substrate.

7. The fabrication method of a nitride-based semiconductor device according to claim 5 , wherein said laser beam is applied with said backside of said support substrate located at a lower side.

8. The fabrication method of a nitride-based semiconductor device according to claim 1 , wherein said retention substrate is formed of at least one member selected from the group consisting of P-doped or N-doped Si, Ge, SiC and GaP.

9. The fabrication method of a nitride-based semiconductor device according to claim 8 , wherein said support substrate comprises sapphire.

10. The fabrication method of a nitride-based semiconductor device according to claim 8 , wherein each side surfaces of the stacked structure of the nitride-based semiconductor device are formed along planes orthogonal to a light emitting layer of the stacked structure.