Lasers cut diamond into more useful wafers

Chiba University has found a way to cut blocks of diamond into thin wafers along a difficult but desirable crystal plane using lasers.

The ‘100’ plain leaves a surface that is relatively easy to planarise and etch for semiconductor use, according to the Chiba researchers, but diamond wants to crack along its 111 plane, so any crack-based separation starting in the 100 plane diverts into the 111 plane. “To the best of our knowledge, slicing diamonds in the 100 plane has not been demonstrated.”

Sawing is the other option, but doing that to the hardest known substance brings its own challenges.

Using lasers to weaken diamond’s 100 plane so that it splits preferentially is not a new idea, but this too has been proving problematic.

Led by Professor Hirofumi Hidai, the Chiba team used a lens to focused short laser pulses through the diamond’s surface and into a narrow cone-like volume within the material.

“Concentrated laser illumination transforms diamond into amorphous carbon, whose density is lower than that of diamond. Hence, regions modified by laser pulses undergo a reduction in density, and crack formation,” said Hidai.

Adjusting laser power and x-y spacing allowed a grid pattern of these amorphous carbon inclusions to be formed whose local cracks joined enough to weaken the 100 plane, so that a sharp tungsten point pushed into the edge of the block could split it.

A 1,064nm Nd:YVO4 laser was used in project, delivering 11.3ps 2μJ pulses at 10Hz.

‘Laser slicing of a diamond at the {100} plane using an irradiation sequence that restricts crack propagation along the {111} plane‘ describes the work in the journal Diamond and Related Materials.

Image credit: Hirofumi Hidai from Chiba University