Optimization of laser machining process for the preparation of photomasks, and its application to microsystems fabrication

Low-Power, Multimodal Laser Micromachining of Materials for Applications in sub-5 µm Shadow Masks and sub-10 µm Interdigitated Electrodes (IDEs) Fabrication

“…Fabrication of the shadow masks down to~1.5 µm was successfully demonstrated, as shown in Figure 10. To the best of our knowledge, this is the lowest feature size demonstrated for laser defined shadow masks [3,23]. Previous work with laser micromachining has produced feature sizes down tõ 10 µm.…”

“…Once the program is executed with the laser, substrate material removal can be a result of photochemical, photothermal, or photophysical ablation [40], as shown in Figure 2. Commonly used processes include laser cutting, scribing, drilling, or etching to produce relief structures or holes on a substrate in ambient temperatures [3,8,23,27,[40][41][42]. The power of this technique lies in the ability to construct desired patterns on arbitrarily shaped surfaces, with the only limitation being the degrees of freedom and the resolution of the motion controller.…”

“…In the case of RIE multi-wafer/multi-substrate parallel processing is also possible as with some laser micromachining examples as well for higher throughput micro/nanofabrication. Laser micromachining has occasionally been used for shadow mask fabrication; however, the state of the art in laser micromachining (minimum feature size of 10 µm) [23] (to date) has relied entirely on single-wavelength excimer, CO 2 , and Nd:YAG (neodymium-doped yttrium aluminum garnet) lasers [1,3,12,[23][24][25][26][27][28][29][30][31][32][33][34][35][36]. To the best of our knowledge, multimodal laser micromachining has not been used for shadow mask fabrication.…”

“…The lasers used in the aforementioned research can produce shadow masks for MEMS applications, but they are unable to micromachine highly precise features on the scale of a single micron, unless they operate in the femtosecond regime [3,7,23,24,30,37]. The higher power of these lasers allows for the processing of thicker materials in a more reasonable time scale; however, this capability comes at the price of benchtop machining, high costs, space, high power usage (GW), and absence of multimodality to micromachine several materials with the same tool.…”

“…Shadow masking technology is an integral part of fabricating micro/nanostructures for prototyping in microelectronics, optical, microfluidic, MEMS, packaging, and biomedical lab-on-a-chip applications [11,23]. Typical methods for producing shadow masks, such as photolithography and deep reactive ion etching (DRIE) or ion beam milling, are expensive, require cleanroom-based fabrication, expensive vacuum equipment, ultra-pure air filtration, and advanced know-how [3,50].…”