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High-throughput flexible direct imaging for

packaging/MEMS fabrication

By Shota Majima, David Hyde [SCREEN Semiconductor Solutions Co., Ltd.]
T he r e a r e a nu mb e r of production and the complexity in resulting the GLV™ functions as a programmable

direct imaging systems for
has become a financial burden and a
modulation and switching of laser light
advanced packaging and processes. The combination of these factors diffraction grating, enabling attenuation,
microelectromechanical systems (MEMS) design constraint to manufacturers. In fact, with unparalleled resolution, speed, and
applications. Several are discussed in the MEMS manufacturing and some advanced precision. Using this new technology, we
sections below, and this article will propose packaging techniques, like heterogeneous or have developed a flexible direct imaging
using direct imaging for the die-first fan- chiplet integration, are now looking toward system for advanced packaging and MEMS
out packaging of heterogeneous devices maskless systems to resolve these issues. industries with support for resolutions down
that use high-density organic interconnects. Especially in die-first fan-out packaging to 2/2µm. When configured with multiple
This last application will be key for future technology, the flexible compensation exposure heads, this system can process
high-performance computing (HPC). exposure of a maskless system is necessary a wide range of substrate types, from
to achieve production level throughput 200mm/300mm wafers up to 600mm square
Mask-less direct imaging with the high-overlay accuracy needed panels. The ability to control the reflected
lithography to maintain yield. The stepper/aligner light level by changing the electrical bias
The most common patterning method approach of mask-based lithography enjoys at each ribbon allows the use of multiple
of semiconductor microfabrication is to high overlay accuracy, but often does so at exposure dose levels (grayscale exposure)
project a mask pattern onto the surface to the expense of throughput. in the same exposure operation. Figure 1
be exposed. In R&D departments, maskless illustrates the light valve’s structure (Figure
direct imaging systems are more common Direct imaging with spatial light 1a), including grayscale exposure samples.
as the need for a flexible lithography process modulator With grayscale exposure, the resist side
has taken priority over the higher throughput The Grating Light Valve (GLV™) is a wall angles can be controlled to generate
of a mask-based system. However, as the high-performance spatial light modulator the tapered shape needed for Cu sputtering
pattern designs in mass production become composed of thousands of free-standing (Figure 1b) and avoid the reverse taper
smaller, and of increasing complexity, silicon-nitride micro-ribbons anchored on that leads to sputtering defects and plating
the cost of manufacturing the device is the surface of a silicon die. By electronically continuity failures. This technique can
increasing, partially driven by the mask controlling the deflection of the ribbons, also be applied to produce dual-damascene

Figure 1: Illustration of GLV™ a) structure, b) taper shape control, and c) application to dual-damascene lithography.

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