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  • Pulsed Laser Deposition at Wafer Level is a game changer

    Global SMT Canvas-2 (6)

    Source: EE Times

    For a technology to have a broad impact, it should do more than solve a short-term challenge; it should also go beyond the advancement of existing technologies to open the doors to future innovations. That’s how we describe the world’s first pulsed laser deposition (PLD) technique for semiconductor mass production, which was unveiled by Lam Research earlier this year.

    Marking an evolutionary shift in the way thin films can be deposited on a wafer, Lam’s Pulsus PLD expands the range of complex multi-compound materials that can be deposited, enabling thin-film layers in a way that wasn’t possible through conventional technologies, such as reactive sputtering.

    In the short term, that’s an important development because it helps address the growing demands for next-generation MEMS-based microphones, as well as the radio frequency (RF) filter enhancements needed to advance the evolution of 5G and Wi-Fi technologies.

    Beyond that, it creates new opportunities for specialty technology chipmakers to accelerate their product roadmaps and explore longer-range capabilities.

    Pulsed laser deposition: from lab-scale to fab-scale

    The use of lasers in semiconductor production processes isn’t new. In fact, pulsed laser deposition has been available for several decades at laboratory scale. PLD is a physical vapor deposition method that uses a pulsed laser shot to energize material, creating a deposition vapor that can be condensed on different substrates. Its limitations, however, allowed it to produce only a few wafers per day at most.

    Until recently, the need for such an advanced deposition technique for volume manufacturing hadn’t been prevalent. But growing consumer demand across several product segments, as well as the extensive work by Lam Research to overcome technical issues that previously prevented high-volume manufacturing, led to a wafer-level fab tool designed for full automation production. Some of those technical issues included the uniformity of films, particle filtering in the system and the maturity of the tool itself.

    Now integrated on a production platform, fab-scale PLD can produce cassettes of wafers with stable thin-film performance while ensuring exceptional film uniformity and quality at a fraction of the cost per wafer compared with conventional deposition methods. Such enhancements can help chipmakers lower costs while boosting their manufacturing yields.

    The scandium factor

    Rather than using a more conventional sputtering-type technique, pulsed laser deposition generates deposition by shooting a high-power laser pulse onto a source material, which is vaporized and transformed into a very high-energy plasma that moves quickly to the wafer, where it then condenses to a thin film. In other words, when a ceramic target of the desired composition and properties is hit by the laser pulse, it enables a thin film with the same composition and properties to be deposited on a wafer.

    PLD diagram.

    One of the main benefits of this technique is the ability to deposit a wide range of complex multi-compound materials, including high concentrations of scandium, into an aluminum scandium nitride film. A greater concentration of scandium in these films can have an immediate impact on real-world applications.

    The proliferation of wireless technologies, for example, continues to create a demand for higher data transfer rates, something that’s achieved by either turning to higher frequencies or using different bands of frequencies to increase the total bandwidth. Higher frequencies and higher density of adjacent bandwidths require not only more of the RF filters but also filters that have higher coupling constants and high-frequency selectivity.

    Achieving higher scandium concentrations in aluminum nitride films can help increase RF filter performance. Pulsed laser deposition can take the scandium concentration in the film to at least 40%, up from the previous 30% limit, while keeping the film properties at a high quality.

    Specialty technologies, such as piezoMEMS-based microphones, also see improved performance when films have higher concentrations of scandium, primarily through an enhanced signal-to-noise ratio, as well as a form factor that is important in the consumer and automotive sectors.

    Some mobile phones, for example, are equipped with multiple microphones that strive to improve voice quality as well as listening capabilities.

    PiezoMEMS, the microscopic devices that utilize piezoelectricity to generate motion and perform specific tasks, enable precise control, sensing and energy conversion in compact and efficient devices. As such, piezoMEMS microphones allow for the low-/no-power “always listening” state to be realized.

    Looking beyond today

    Any new technology’s true potential can never be realized in the earliest days.

    Consider that demand for the manufacturing equipment used to make MEMS devices grew to more than $940 million in 2023 and could keep growing as chipmakers discover new ways to enhance device performance. Likewise, as 5G and Wi-Fi bands continue to expand, so, too, will the need for more sensitive, selective filters.

    There’s also a growing list of industries that could benefit from these technological advancements, from automotive and healthcare to retail, manufacturing and industrial automation.

    And then there’s the unknown.

    In end markets, the technology landscape continues to build not only on current drivers like artificial intelligence and the internet of things but also advances in augmented and virtual reality (AR/VR) that are expected to lay the groundwork for the metaverse in the coming decade.

    What’s most exciting about this breakthrough is that, in addition to higher concentrations of scandium in aluminum nitride films, Pulsus PLD can deposit a wide range of other complex, multi-element materials that cannot be applied by other methods. Already, new materials are being explored to meet the demands of the specialty technologies market for applications such as AR/VR and quantum computing.

    What remains unknown is where this shift will take us next, beyond the new standards that are being set in semiconductor fabrication.

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