Japan Develops New Laser Slicing Technology For Diamond Semiconductor

Diamond is a promising material for the semiconductor industry, but slicing it into thin wafers can be a real headache and challenge.
In a recent study, a team of researchers at Chiba University developed a new laser-based technique that can cut diamond along the optimal crystal plane. This discovery will help make this material more cost-effective for efficient power conversion in electric vehicles, and high-speed communication technologies.
Previously, although the properties of diamond are attractive to the semiconductor industry, the application of diamond materials has been limited by the lack of technology currently on the market to efficiently cut diamond into thin slices. In the absence of efficient slicing, wafers must be synthesized one by one, making their manufacturing cost prohibitive in most industries.
A Japanese research group led by Professor Hirofumi Hidai of Chiba University's Graduate School of Engineering has recently found a solution to this problem.
In a study recently published in the journal Diamonds and Related Materials, they report a new laser-based slicing technique that can be used to cleanly cut diamonds along the optimal crystal surface to produce smooth wafers.
The properties of most crystals, including diamond, vary along different crystal planes (surfaces that hypothetically contain the atoms that make up the crystal). For example, diamond can be easily cut along the surface of ｛111｝. However, slicing ｛100｝ is challenging because it also produces cracks along the disintegrated surface ｛111｝, which increases notch loss.
To prevent the propagation of these undesirable cracks, the researchers developed a diamond processing technique that focuses short laser pulses on a narrow, tapered volume within the material.
Prof. Hidai explains, "Focused laser irradiation converts diamond into amorphous carbon, which has a lower density than diamond. As a result, the density of the area altered by the laser pulses decreases and cracks may form."
By irradiating these laser pulses onto a sample of transparent diamond in a square grid pattern, the researchers created a grid inside the material that consisted of small regions prone to cracks. If the spacing between the modified regions in the grid and the number of laser pulses used in each region is optimal, all modified regions are connected to each other by small cracks that preferentially propagate along the ｛100｝ plane. Thus, a smooth wafer with a surface of ｛100｝ can be easily separated from the rest of the block by simply pushing a sharp tungsten needle to one side of the sample.
Overall, the above technique is a key step in making diamond a suitable semiconductor material for future technologies. In this regard, Prof. Hidai says: "The ability of diamond slices to produce high-quality wafers at low cost is crucial for the fabrication of diamond semiconductor devices. Thus, this research brings us one step closer to realizing the various applications of diamond semiconductors in society, such as improving the power conversion rate of electric cars and trains."