I just returned from Dublin, Ireland, courtesy of Xsil Ltd., after attending the company's "Open Days." The event was interesting, filled with technical presentations and a plant tour to look at their latest Xise laser-based tools in action. And, since it was very well attended by existing and potential customers, as well as being open to the trade press, I received some perceptive insights as to what users plan to do with these production laser tools. Some laser tools targeting IC packaging applications have been around for a while, but acceptance has been somewhat limited. Xsil, however, bought over 50 Coherent lasers in 2002 and expects to need about 150 more this next year, according to Peter Conlon, CEO. These numbers are impressive, since the first machines were launched in 2002. Cutting Thin and Narrow One serious issue confronting users producing thinned wafers is dicing without breakage. Next-generation wafers will be even thinner, so dicing will become that much more critical. If the customers I spoke with are correct, saw singulation breakage is already a costly problem, especially with higher-value chips.
Dicing saws have served the industry well for many years, despite their drawbacks. Saw blades need relatively wide kerf streets, for example, which is reason enough to look at laser dicing. Would you believe an order of magnitude reduction in street real estate? Lasers can do it. Math 101 Laser dicing is cost effective compared to a dicing saw. Dep-ending on chip value, sparing any thinned wafer ICs from damage during the dicing process becomes an ROI cost equalizer. Xsil's laser technique seems appropriate for silicon. The considerably narrower kerfs allow many more devices per wafer, a powerful incentive to perform a cost-benefit analysis. For example, with a 200mm diameter, 50µm-thick wafer with 200µm streets, a saw typically dices over 8K 2 x 2mm die per hour, while the Xise 200 laser singulates 74K+ in the same time with just a 30µm kerf.
Then there is laser scribing with a variety of materials. Depending on the materials used in the wafer, polymers on metal or silicon, stacked layers or low-k structures are no problem. Via holes, blind or through-hole, seem easy to create at a rapid pace. This technology handles substrates too. It Slices, Dices and ... No, it's not a Vegematic on steroids! These versatile Xsil machines really are very flexible regarding applications. Now those who know me are aware that MEMS and optoelectronics are topics that I enjoy since they are enabling technologies. Building and packaging micro machines and photonic devices is not as easy as some might think, but it might be easier now. The Xsil tools are powered by lasers from Coherent Inc., a pioneer in practical, serious industrial lasers. So if you need to do a bit of micromachining (fabricating a MEMS sensor or carving a straight or curved trench), the machines do it quickly. Lasers ablate (vaporize material). Ablation does result in some debris settling on the wafer surface. No problem. A simple water rinse will remove it, or you can use the defocused laser beam to clean and smooth the surface.
Those of us visiting Dublin for the first time found it a fascinating city with friendly people, great restaurants and even a place or two offering well-known liquid refreshments. [xsil.com] The Challenge to Edge Emitters Optical components supplier Photodigm Inc. (Richardson, Texas) is trying to challenge the entrenched edge-emitting lasers. The company has announced a breakthrough 1310nm Grating-outcoupled Surface-Emitting (GSE) laser technology. The single-mode devices output up to 6mW, essentially providing the performance of a DFB (distributed feedback) laser with the advantages of a vertical cavity surface-emitting laser (VCSEL). Until now, 1310nm lasers have been available only as edge-emitting lasers. The industry has devoted considerable resources for surface-emitting 1310nm VCSELs with mixed results. The GSE laser uses a proven edge-emitting epitaxial material structure (AlInGaAs/InP) and relies on first and second order gratings for the DBR reflectors and the outcoupler. Narrow-Beam Divergence GSE devices exhibit single mode operation with output powers up to 6mW, threshold currents below 20mA, slope efficiencies of 0.1mW/mA, 5° x 7° beam divergence and modulation speeds of 2.5Gbps. The narrow beam divergence provides fiber-coupling capability. Since it's a surface-emitting device, it offers significant efficiencies in testing and packaging.[photodigm.com]
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