High aspect ratio diamond nanosecond laser machining

Abstract

Laser processing of diamond has become an important technique for fabricating next generation microelectronic and quantum devices. However, the realization of low taper, high aspect ratio structures in diamond remains a challenge. We demonstrate the effects of pulse energy, pulse number and irradiation profile on the achievable aspect ratio with 532 nm nanosecond laser machining. Strong and gentle ablation regimes were observed using percussion hole drilling of type Ib HPHT diamond. Under percussion hole drilling a maximum aspect ratio of 22:1 was achieved with 10,000 pulses. To reach aspect ratios on average 40:1 and up to 66:1, rotary assisted drilling was employed using > 2 M pulse accumulations. We additionally demonstrate methods of obtaining 0.1° taper angles via ramped pulse energy machining in 10:1 aspect ratio tubes. Finally, effects of laser induced damage are studied using confocal Raman spectroscopy with observation of up to 36% increase in tensile strain following strong laser irradiation. However, we report that upon application of 600 °C heat treatment, induced strain is reduced by up to ~ 50% with considerable homogenization of observed strain.

Research and Application Progress of Laser-Processing Technology in Diamond Micro-Fabrication

“…The double-pulse laser ablation of diamond material on a silica sphere substrate to prepare diamond micropores is shown in Figure 9B, in which funnel-shaped cones are cut across the diamond layer above, with depth-to-width ratios measured at the surface and at a 50% depth of 8:1 and 14.5:1, respectively; however, due to the thinness of the processed diamond film (65 µm), it is not very generalizable for practical processing. Natalie C. Golota [60] used a nanosecond laser (532 nm; 20 ns) to perforate a diamond, and the maximum depth-to-width ratio was 22:1 at 10,000 pulses. The maximum depth-to-width ratio was obtained by further increasing the cumulative number of pulses to above 40:1, as shown in Figure 9C.…”

“…Figure 9. (A)The cutting effect diagram of different focus settings and the relationship between laser power and cutting depth and slit width[57]; (B) radiograph of micropores fabricated in a diamond on silicon sphere substrate by the double-pulse laser ablation method[59]; and (C) the average depth to width ratio obtained in diamond is 40∶1[60].…”