Depending on the laser system setup, the imaged beam can precisely drill or pattern materials with such finesse as to minimize or negate any thermal damage to the surrounding material. Therefore, precise and tailored to the material being processed, field mappers have enabled new opportunities for precision micromanufacturing that could not have been possible 20 years ago.
Laser system setup, the imaged beam can precisely drill
The arrival of integrator technology for laser materials processing was under the radar and developed in earnest when major challenges were encountered with the introduction of excimer lasers into the marketplace. During these early years, integrator development was kept secret until patent filings revealed their implementation. Many of these innovations were championed by laser system developers who were seeking solutions to improve excimer laser beam uniformity for large field size high-precision laser processes. In nearly all applications, excimer laser output uniformity is critical for high-precision applications.
During the early 1980s, to create a uniform irradiance beam profile, engineers were limited to either improving the performance of the laser itself, at a hefty price, or utilizing optical techniques. Modification of the laser meant trade-offs; increased uniformity at the sacrifice of pulse energy or power and that still did not guarantee the best uniformity.
At this time the excimer laser was finding new applications within semiconductor processing such as lithography and gaining ground in the promising field of laser micromachining. These early adopters were exposed to similar integrator designs used within illumination systems for lamp-based exposure tools, such as those produced by Oriel Instruments Corporation (Stratford, CT), which were generally simple lens array integrator designs.
The earliest and relatively successful example of an industrial excimer laser application that would not have been possible without the use of beam integrators, besides the semiconductor lithography market, was laser annealing of silicon. Patented by XMR, Inc. (Houston, TX) in 1986 and issued in 1988 as US Patent 4,733,944, the design is one of a handful of instances of an imaging beam integrator for a high-volume industrial laser process requiring absolute stability and uniformity. What was unique about the design at the time was the fact that the spot size produced could be selectively adjusted in size at the working plane. Adjustability allowed variation of the energy density on target, tailoring it to an optimum setting and process area.
From this point, the design of laser beam integrators began to take the form of specialized optical configurations with further enhancements and refinements to meet the needs of ever-demanding laser micromachining processes. In 1994 the integration of UV excimer lasers for laser micromachining of fluidic structures was being exploited for consumer and medical device products. One such product was the production of nozzle plates and fluidic channels for inkjet printers.
Although personal inkjet printers had entered the marketplace in 1988, it was not until 1991 when inkjet printer manufacturers had begun to seriously consider excimer lasers as a means to reduce the costs of forming precision inkjet nozzle plates, which were upward of $4.00 each to manufacture.
At that time, manufacturing nozzle plates to micron accuracies was not an easy task and they were costly to manufacture using traditional lithography and nickel electroforming techniques. It was clear in the early days of process development that the design of excimer beam delivery optics, physical system configuration, methods of optical beam shaping, and laser material interaction would play significant roles in producing inkjet nozzle plates.
Due to higher demands for quality and the critical nature of providing consumers with exceptionally reliable products, the excimer processes needed to be robust and repeatable to a 3σ or better level.
When looking for the most dominant market segment that has benefited from beam shaping, you simply need to review history. As a rule of thumb, if you want to understand where technology will be 10 years into the future, you need to only look backward 20 years into the past. Within our optical community we tend to think that beam shaping innovations just came out of nowhere, but in reality there were great challenges that spurred development by pioneers in our field.
