Excimers still important for microelectronics manufacturing
The article, “‘New’ UV lasers resolve material and cost issues” (June, p. 87) examined the emergence of UV solid-state lasers for materials-processing in microelectronics manufacturing. The motivation for adoption of these lasers was well described, along with beam-shaping techniques that have rendered them more versatile. In some cases, as the article states, UV DPSS lasers have opened up industrial high-volume applications where excimer lasers have not been able to compete well with nonlaser technologies.
There is another side to the story, however. As the article correctly notes, excimers are the uncontested light source of choice in applications in which their unsurpassed average power and pulse energy provide the means of ablating large areas quickly. Because excimers lend themselves well to beam-profile homogenization techniques, they also provide a degree of depth control and lateral uniformity of material ablation that is unparalleled by any other laser technology. And they do so at wavelengths spanning the UV spectrum, from 351 to 157 nm (the article incorrectly identified 355 and 266 nm as excimer wavelengths).
As a result, excimers are the core technology behind a number of key applications in mass-production microelectronics manufacturing. And this will continue for the foreseeable future, because other UV laser light sources will not be able to match their power and energy output, nor their ability to reach into the VUV region below wavelengths of 200 nm.
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