Maskless Exposure Lithography with High Resolution Patterning for High Volume Manufacturing

July 03, 2019 by Scott McMahan

EV Group (EVG) unveiled MLE™ (Maskless Exposure), a next-generation lithography technology developed to address future back-end lithography needs for MEMS, biomedical, advanced packaging, and high-density printed circuit board (PCB) applications.  The company claims that the MLE is the first highly scalable, maskless lithography technology for high-volume manufacturing.

MLE combines high-resolution patterning with high throughput and yield, while eliminating the considerable overhead costs related to photomasks. Such costs include mask management and maintenance infrastructure.

Furthermore, EVG says that MLE provides unsurpassed flexibility to enable extremely short development cycles for new devices.

MLE technology accommodates any wafer size up to panels. It supports all commercially available resists via a tightly integrated clustered write-head configuration and a multi-wavelength high-power UV source. Throughput is independent of resolution and layout complexity, and MLE achieves the same patterning performance regardless of the photoresist.

MLE targets new and emerging use cases where other approaches face scalability, cost-of-ownership and other limitations.

EVG is now offering demonstrations of its MLE technology at the company's headquarters. MLE technology will be incorporated into a new line of EVG systems, which are currently under development and will be released in due course.

"Our new MLE technology excels in back-end lithography applications, where other patterning technologies, such as steppers, have to compromise on performance or cost. No longer will customers need to choose between resolution, speed, flexibility or cost of ownership for their back-end patterning needs," stated Paul Lindner, executive technology director at EV Group. "Early development work with an exclusive range of customers has shown that the applications benefiting from MLE are wide ranging and growing in number. As we ramp up the development of this unique exposure technology into first products, we look forward to partnering with more companies across the industry to support new devices and applications that will benefit from MLE."

Back-end Lithography Faces Challenges

EVG notes that as heterogeneous integration becomes an increasingly significant force in semiconductor development and innovation, back-end lithography requirements are growing. For example, in advanced packaging, the minimum resolution requirements for redistribution layers (RDL) and interposers with their continuously denser lines/spaces (L/S) are becoming increasingly stringent. In some instances, they are nearing or less than two microns.

At the same time, die placement variation and the use of cost-efficient organic substrates require more flexibility in patterning.

The company says that the requirements for improved overlay accuracy as well as high depth of focus in vertical sidewall patterning are also growing. New requirements including minimizing pattern distortion and die shift due to wafer distortion in fan-out wafer level packaging (FoWLP) and supporting thick and thin resists, are just some of the guidelines for existing and future advanced packaging lithography systems.

In MEMS manufacturing, mask/reticle overhead costs have a growing impact on cost of operation, while excellent focus control is crucial for patterning in trenches. In the biomedical and PCB markets, demand is growing for a higher degree of pattern flexibility that can be used with a wide range of both feature sizes and substrate sizes.

MLE Technology Overview

EVG's MLE technology enables high-resolution (<2 microns L/S), stitch-free maskless exposure of the complete substrate surface with high throughput and low cost of ownership. Adding or removing UV exposure heads allows the system to scale according to user needs.

This ease of scaling up facilitates the rapid transition from R&D to HVM mode, for throughput optimization, or to adapt to different substrate sizes and materials.

MLE technology is suitable for processing a range of substrates from small silicon or compound semiconductor wafers up to panel sizes. A flexible and scalable high-power UV laser source, which provides multiple wavelength exposure options, enables MLE technology to  achieve the same patterning performance regardless of photoresist.