Method for separating sapphire wafer into chips

1. A method for separating a sapphire wafer serving as a substrate, on which semiconductor elements are formed, into unit chips, comprising the steps of:

(a) grinding a rear surface of the sapphire wafer so that the sapphire wafer has a designated thickness;

(b) lapping the rear surface of the ground sapphire wafer so that the sapphire wafer has a designated thickness;

(c) polishing the rear surface of the lapped sapphire wafer so that the sapphire wafer has a designated thickness;

(d) sand-blasting the rear surface of the polished sapphire wafer by uniformly blasting particles at a designated pressure during a designated time onto the rear surface of the polished sapphire wafer; and

(e) scribing the rear surface of the sand-blast ground sapphire wafer.

2. The method as set forth in claim 1 ,

wherein the sapphire wafer in the step (d) is warped such that a central portion of the rear surface of the sapphire wafer is higher than an edge portion of the rear surface of the sapphire wafer by a height of 1.5 mm to 2.5 mm.

3. The method as set forth in claim 1 ,

wherein the particles in the step (d) are made of one material selected from the group consisting of silundum (SiC), boron carbide (B 4 C) and aluminum oxide (Al 2 O 3 ).

4. The method as set forth in claim 1 ,

wherein the particles in the step (d) have a diameter of 5 μm to 50 μm.

5. The method as set forth in claim 1 ,

wherein blast time of the particles in the step (d) is less than 5 minutes.

6. The method as set forth in claim 1 ,

wherein blast pressure of the particles in the step (d) is 3 kg/cm 2 to 5 kg/cm 2 .

7. The method as set forth in claim 1 ,

wherein the thickness of the sapphire wafer in the step (d) is reduced by 2 μm to 14 μm.

8. The method as set forth in claim 1 ,

wherein the rear surface of the ground sapphire wafer in the step (d) is ground so as to have a surface roughness of less than 0.013 μm.