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/Job opportunities/Creating Sub-18 nm pitch EUV lithography and plasma etch transfer processes for next-generation device technologies

Creating Sub-18 nm pitch EUV lithography and plasma etch transfer processes for next-generation device technologies

PhD - Leuven | More than two weeks ago

Join in the research and development needed to create the resist materials, lithography, and etch processes required to produce quantum-level devices at pitches smaller than 18 nanometers.

Lithography and plasma etch processes lie at the heart of semiconductor manufacturing for information and communications technology (ICT) devices. Until recently, mass production of ICT devices was conducted using deep ultraviolet exposure; however, the push for smaller and faster components and devices has led the ICT industry to pursue extreme ultraviolet (EUV) lithography as a viable means of production. Thinning resists are needed to image these small features that then create challenges for the plasma etch processes that are used to transfer the circuitry into the material layer needed to form the device. We are searching for people to research and develop methods to use interference lithography to study the response of resist materials to these etch processes needed to produce quantum-level devices.
   By moving to EUV exposure, the diffraction limit of the light is reduced thereby decreasing the size of the achievable print features. In the next few years, the industry will need to image features smaller than 9 nanometers separated by 9 nanometers and smaller (sub-18 nanometer pitch). A key requirement in the development of this lithography is to develop photoresist materials that act as a temporary mask for pattern transfer into the underlying substrate that defines a functional level of the semiconductor device. With this need comes challenges that intertwine material science with the chemistry and physics of lithography processes coupled with the plasma physics and chemistry of the etch processes. This arises from the need to use thinner resists that form the temporary mask to prevent creating defects from pattern collapse and to do this without enhancing defects from photon shot noise and formation of unwanted radiolysis products that also form when exposed to the EUV ionizing radiation. The use of thin resists can also lead to pinholes and unwanted nonuniformities that can reduce the fidelity of the pattern transfer. Further, exposure to plasmas may alter the material morphology leading to micro-fissures and other resist mask breakdowns that also reduce device performance and product yield.
Studying the optimization of EUV lithographic and plasma etch transfer processes has proved difficult at the sub-18 nanometer pitch, as EUV sources with sufficient photon flux have, until recently, only been available from building-sized machines (e.g., EUV scanners) or large-scale facilities such as synchrotrons or free-electron lasers are not configured for single imaging steps on the industry-standard 300 mm wafer substrates.  An alternative source of EUV light for lithography is high-order harmonic generation (HHG), in which visible or near-infrared laser pulses supplied by a tabletop laser are converted to UV or EUV light. These tabletop sources can be deployed for interference lithography of photoresist materials, thus enabling a versatile testbench for lithography that we wish to extend to the development of masking materials for etching processes.
   This multifaceted PhD project aims to peer into the imaging processes and resist materials needed for both the EUV lithography and etch processes. The project will use the HHG-based EUV sources within the newly installed imec AttoLab for lithography to develop an imaging process of a representative test environment needed to develop materials for sub-18 nanometer plasma etch processes. The project will build upon established techniques for interference lithography to research and develop new techniques for spatial and temporal coherence beam alignment needed for enhanced interference imaging and for controlling pattern placement of those interference patterns so that we may insert test patterns into active device areas for pattern transfer by imec’s etch R&D team. It is then expected that the student will work with the team to understand how the resist material responds to the etch and based on this learning, research ways to improve resist material and lithography process to better enable a successful pattern transfer.  The diagnostics of the generated patterns will be conducted at imec’s state-of-the-art lithography analytics facilities and will be compared and reconciled with results obtained from our commercial EUV scanners.
   The experimental results will be used to further our understanding of the entwined lithography physics and complex photoresist chemistry and how it relates to the plasma etch. The acquired knowledge will pave the way for the development of new materials for the lithographic and subsequent etch processes needed to make next generation quantum level devices.
   We are seeking an outstanding candidate with enthusiasm for experimental science with a master’s degree in physics, physical chemistry, nanotechnology, or an equivalent international degree. The candidate should be able to work in an international environment and good written and oral communication skills in English are a prerequisite. Experience in experimental ultrafast optics or photolithography and plasma science is advantageous but not necessary.


Required background: Physics, Physical Chemistry, Nanotechnology, Material Science

Type of work: 70% Experimental, 20% Modeling/Simulation, 10% Literature 

Supervisor: Stefan De Gendt

Daily advisor: Esben Witting Larsen

The reference code for this position is 2021-132. Mention this reference code on your application form.