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New Exposure Technology

Maskless Lithography for High Volume Production

29. September 2020, 11:06 Uhr | Heinz Arnold

EV Group's first maskless lithography system for high volume production (HVM) achieves up to five times higher throughput compared to currently available maskless exposure systems.

EVG has introduced the first exposure system based on the newly developed Maskless Exposure Technology (MLE). Now volume production can start.

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The "LITHOSCALE" product platform is suitable for use in advanced packaging, for the production of MEMS, for components used in biotechnology and medical technology, and for IC substrates. LITHOSCALE combines high resolution without restriction of the exposure field, powerful digital processing for real-time data transfer and instant exposure, and a highly scalable design. In addition, the systems are highly flexible and allow the production of many variants. The result is the world's first maskless lithography system for high volume production (HVM) with up to 5 times higher throughput compared to currently available maskless exposure systems. EVG has already received several orders for LITHOSCALE systems and will start delivering the systems to customers before the end of this year.

New challenges for lithography

3D integration and heterogeneous integration are becoming increasingly important to enable continuous improvements in the performance of semiconductor devices. This leads to more complex packages and an increasing number of available packaging variants - requiring greater design flexibility and driving the desire to simultaneously implement die and wafer-level designs in back-end lithography.

MEMS manufacturing also presents new challenges to lithography due to its complex product mix, which drives up the overhead costs for masks and reticles. In the markets for IC substrates and biomedical products, there is a growing demand for a higher degree of patterning flexibility to cover a wide range of feature and substrate sizes. Rapid prototyping is also becoming increasingly important in biotech applications, increasing the need for more flexible, scalable and ready-to-use lithography approaches.

Traditional mask-based lithography systems are impractical for many of these applications, especially when they require rapid prototyping and testing of new product designs and when customized products are required. Here, the cost and time required to manufacture, test and rework a large number of mask sets can quickly add up.

In addition, existing back-end lithography systems in advanced packaging applications have difficulty with higher order nonlinear substrate distortion and die-shift problems. This can be observed especially after die reconstitution on the wafer in fan-out wafer level packaging (FOWLP). At the same time, existing maskless lithography approaches do not provide the combination of speed, resolution and ease of use required for HVM environments.

A further advantage is that the maskless approach eliminates the need for mask-related consumables, while the adjustable solid-state laser exposure source is designed for high redundancy and long lifetime and requires virtually no maintenance and recalibration. Powerful digital processing enables real-time data transfer and instant exposure - eliminating hours of setup time for each digital mask layout, as required by other maskless lithography systems. The system is also capable of processing single dies or chips, with fast full-field positioning and dynamic alignment providing high scalability for a variety of substrate sizes and shapes. The result is an extremely versatile, maskless lithography platform suitable for a variety of microelectronic production applications.

"This opens the door to a new world of possibilities for digital lithography", explains Paul Lindner, Executive Technology Director of EV Group. "LITHOSCALE was designed from the ground up as a highly flexible and scalable platform that enables high-volume manufacturers to finally take advantage of the benefits of digital lithography".

The special features of LITHOSCALE

LITHOSCALE offers high-resolution (<2 µm line/space), seamless maskless exposure of the entire substrate surface without compromising throughput, thanks to a powerful digital infrastructure that allows instant mask layout changes "on the fly", and the multi-exposure head configuration that enables highly parallel processing to maximize throughput. LITHOSCALE's ability to create a rudimentary pattern for interposers that exceeds today's reticle sizes is particularly useful for advanced devices with complex layouts, such as those required for advanced graphics processing, artificial intelligence (AI) and high performance computing (HPC). The high precision of the system is complemented by distortion-free optics and stage placement accuracy, which ensures seamless projection across the entire substrate. LITHOSCALE also uses dynamic alignment techniques and die-level compensation with automatic focus, allowing it to adapt to substrate material and surface variations and achieving good overlay performance. LITHOSCALE is suitable for a wide range of substrate sizes and shapes (such as wafers with a diameter of up to 300 mm and rectangular substrates up to the size of so-called "quarter panels") as well as for various substrate and resist materials.