The process of creating a pattern on a wafer is known as lithography. Typically, light is shone through a mask onto a photoresist that coats the wafer. After exposure, the photoresist is “developed,” which removes the exposed part of the resist (or the unexposed resist if it is negative resist). A photoresist coat/bake/develop system — often called a “track system” is typically connected directly to the wafer exposure tool or wafer “stepper.”

The exposed wafer is then etched, where the photoresist acts as a barrier to the etching chemicals or reaction ions. The photoresist is then removed by stripping or “ashing.” In complex integrated circuits, a modern CMOS wafer will go through the photolithographic cycle up to 50 times, making lithography one most critical process step.

Increasingly smaller wavelengths of light have been used to create smaller dimensions. Complex mask designs have also evolved, such as optical proximity correction (OPC), to correct for optical effects. Mask-source optimization techniques have also been developed to correct for variations in the source and on the wafer.

A push to extreme ultra-violet (EUV) lithography has been under way for a decade or more, led by ASML Lithography. Alternatives have also been research and developed, including nano-imprint lithography (NIL), which uses stencils and multi e-beam (MEB) lithography, which uses a large bank of individually controlled electron beams to expose the wafer directly (no mask required). More recently, an interesting approach called directed self-assembly (DSA) has been studied, which enables very small dimensions. DSA uses a guide structure on the wafer and polymer-based chemicals to create regular lines with very small dimensions.

Check out our Lithography Topic Center for regular updates.

Additional Reading:

Feed-forward overlay control in lithography processes using CGS

Advanced lithography and electroplating approach to form high-aspect ratio copper pillars

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ARTICLES



EUVL: Taking it down to 5nm

05/17/2016  The semiconductor industry is nothing if not persistent — it’s been working away at developing extreme ultraviolet lithography (EUVL) for many years.

Neon shortage coming

02/18/2016  Semiconductor lithographic use of Neon is increasing more rapidly than expected for several reasons including the delay of EUVL while demand for finer line width patterning is increasing.

WIKA Group adopts HERCULES lithography track system from EV Group

02/17/2016  EV Group (EVG) today announced that WIKA Group has placed an EVG HERCULES lithography track system into production for manufacturing pressure sensor devices.

Ultratech and Qoniac jointly develop 3D lithography APC solution

01/28/2016  Ultratech, Inc. and Qoniac GmbH announced that the companies are jointly developing a 3D lithography advanced process control (APC) solution for advanced 3D CMOS manufacturing.

Lithography

01/06/2016  Lithography is used to create a pattern on the wafer.

EUV, multiple patterning, integrated circuits among topics for SPIE Advanced Lithography 2016

01/06/2016  EUV lithography is on the threshold of becoming a mainstream patterning technology for sub-10nm chips, featured speaker Anthony Yen of Taiwan Semiconductor Manufacturing Co. (TSMC) will tell fellow attendees at SPIE Advanced Lithography 2016.

Feed-forward overlay control in lithography processes using CGS

12/09/2015  Feed-forward can be applied for controlling overlay error by using Coherent Gradient Sensing (CGS) data to reveal correlations between displacement variation and overlay variation.

Advanced lithography and electroplating approach to form high-aspect ratio copper pillars

12/08/2015  It is possible to fabricate copper pillars more than 100μm in height, with aspect ratios up to 6:1, using advanced packaging stepper lithography in conjunction with electroplating.

Vistec Electron Beam established US show room facility with Variable Shaped Beam Lithography system

11/24/2015  Vistec Electron Beam GmbH, a supplier of electron-beam lithography systems, announced that it has established a show room facility in Schaumburg, IL to promote and demonstrate their Variable Shaped Beam systems specifically for the US and North America market.

Lithography alternatives: Why are they essential?

11/13/2015  The availability of patterning alternatives in the lithography landscape represents a big opportunity to properly address the coming needs generated by the IoT.

eBeam Initiative survey shows rising optimism in EUV lithography, multi-beam technology for photomask production

09/29/2015  The eBeam Initiative announced the completion of its fourth annual eBeam Initiative members' perceptions survey.

EV Group ramps nanoimprint lithography into high-volume manufacturing with HERCULES NIL Track System

07/07/2015  EV Group (EVG), a supplier of wafer bonding and lithography equipment for the MEMS, nanotechnology and semiconductor markets, today unveiled the HERCULES NIL—a fully integrated track system that combines cleaning, resist coating and baking pre-processing steps with EVG's SmartNIL large-area nanoimprint lithography (NIL) process in a single platform.