Micro-Nano Laser Machining
Typical examples of Micro Hole Drilling in Ceramics, Plastic and Metals.

Excimer Lasers

Excimer lasers operating in the ultra-violet wavelength (193nm, 248nm, 308nm) with average power approaching 100 Watts, are ideal for processing of plastics, glass, ceramics and thin metals with tolerances approaching 1 micron.

Eximer lasers utilize the mask projection technique that is akin to laser lithography, the same leading edge technology that manufactures next generation microcomputer chips. The excimer laser illuminates a mask (that is not in contact with the part) that contains a pattern such as a circle, rectangle or any complex shape. This pattern is imaged by downstream optics to produce an identical yet significantly smaller pattern.

Most often, the mask is fabricated inexpensively by chemically etching stainless steel masks whose pattern is typically 150 microns (0.006") or greater. Since the mask projection technique optically reduces or "demagnifies" the mask pattern by an integral amount (typically 5 to 30 times), simple low cost methods can be used to fabricate the mask. In some specific applications, with dimensional requirements less than 5 microns, glass mask (metal deposited on quartz) are used.

An excimer laser is gas powered laser, automatically filled with a specific gas mix and run for a period of time before the existing gas fill is evacuated and replenished with new gas. The excimer laser achieves the highest average power (up to 100 Watts) in the ultraviolet spectrum, with laser wavelengths ranging from 157nm, 193nm, 248nm, 308nm and 351nm.

Excimer lasers became industrial workhorses when the semiconductor industry gravitated from UV lamp sources to excimer lasers to produce next generation computer chips. Today's lithographic tools, scanner and steppers, deploy excimer lasers. In the case of laser micromachining applications, excimer lasers are utilized as lithographic tools in the range of 1 micron features (or higher).

DPSS and Excimer lasers ablate or vaporize the material, minimizing debris or heat affected zone. This photo chemical ablation process works by the laser breaking the molecular bonds within the material and ablated material is ejected upward and away from the material surface at supersonic speed. DPSS laser have picosecond or femtosecond pulse parameters. These temporal pulse parameters are so short that there isn't time to generate heat, minimizing any thermal effects such as melting. This is especially the case as the wavelength gets shorter, e.g., 532nm, 352nm, 266nm, 193nm.

The DPSS laser source operates at high repetition rates with an etch rate of approximately 0.1 to 0.5 microns per pulse. The laser can drill through or blind holes. By counting the number of pulses, the depth of machining can be accurately controlled. As an example, these lasers are ideal for selective removal of a top coating or layer without damaging the underlying layer removing material precisely, like peeling an onion layer-by-layer.

 

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