For 26 years, Gigaphoton’s business has been building the excimer lasers that sit next to DUV scanners in fabs around the world. The 4-ton KrF and ArF lightsources, each packed with more than 8,000 parts, are located in the subfab beneath the exposure tools and supply the light that patterns most of the layers in a modern chip. The company, a wholly owned subsidiary of Japanese construction-equipment giant Komatsu, has shipped more than 2,500 lightsources since it was established in 2000 and now employs about 1,400 people. That core business is doing well. But in a briefing at SEMICON West in October, President and CEO Tatsuo Enami and his team made the case that Gigaphoton’s light has many more uses in the fab than lithography alone. “Because the wavelength is shorter, it can be utilized everywhere,” Enami said. The company is now pursuing four areas outside its traditional scanner business: excimer laser processing for advanced packaging, a compact EUV lightsource, EUV light for actinic mask inspection and metrology, and gas recycling to protect fabs from the next neon supply shock. A fifth effort, pulsed laser deposition for superconducting wire, targets fusion energy. Advanced packaging: drilling vias with a lithography laser AI and HPC are pushing chipmakers toward heterogeneous integration, where performance depends as much on how densely chiplets can be wired together on a substrate as on transistor scaling. Those chip-to-chip connections need short, high-density interconnects, and that means very small vias. Gigaphoton says chiplet packaging calls for vias of 5 µm to 10 µm in diameter at the die edge, while vias for power delivery and PCB connections remain in the 80 µm to 100 µm range, often on the same panel. Today’s tools struggle with that combination. “If you use a CO₂ laser, you can drill down to 30 µm only,” said Takehiko Tomonaga, general manager of the corporate planning department in Gigaphoton’s business strategy division. A UV laser at 355 nm can get down to about 10 µm. “But the requirement for chip-to-chip interconnect in the future is smaller than 10 µm in diameter.” Lithography-based via formation can go smaller, but it adds photoresist, develop and etch steps, and cost. Gigaphoton’s answer is the G300K, a 248 nm KrF excimer laser developed from its lithography lightsources and designed for ultra-fine ablation of package substrates ( FIGURE 1 ). It delivers 300 W at repetition rates up to 4 kHz. Rather than drilling holes one at a time, the laser illuminates a mask, and projection optics image the pattern directly onto the organic dielectric. Gigaphoton developed both the lightsource and the mask projection optics. Figure 1. The G300K KrF excimer laser for ultra-fine ablation in advanced packaging. (Source: Gigaphoton) The physics is the key difference. At 248 nm, photons are strongly absorbed by organic materials such as Ajinomoto build-up film (ABF), polyimide and solder resist, and they break molecular bonds directly. Material is removed photochemically rather than thermally, so there is almost no heat-affected zone and little melt or debris ( FIGURE 2 ). The result, according to Gigaphoton, is near-vertical sidewalls with precise control of depth and diameter (a taper angle of 87.6° at a 3 µm via) and no damage to the underlying copper. The process also works on glass. Figure 2. Minimum via diameter by laser type: about 30 µm for CO₂ lasers, about 10 µm for 355 nm UV lasers and about 3 µm for 248 nm excimer lasers, which remove material photochemically rather than thermally. (Source: Gigaphoton) Because the via pattern comes from a mask, every via in the field is formed at once, whatever its size. “If you use a CO₂ laser, you can drill one diameter at a time. You need to switch the laser to drill another size of hole,” Tomonaga said. Gigaphoton showed a single exposure forming eight different via diameters, from 10 µm down to 3 µm, in ABF. Recent results show ABF vias from 6.5 µm down to 3.5 µm that