Hello folks,
I am currently a doctoral researcher at Interuniversity Mictroelectronics Center (IMEC) located in Leuven, Belgium. My PhD project is part of a Marie-Curie funded European project with the acronym ELENA (Low energy ELectron driven chemistry for the advantage of emerging NAnofabrication methods). Here is the link to the ELENA website: ELENA-eu.
Under this consortium, a team of 15 Early Stage Researchers (ESRs) have been hired by different European research institutes and universities for their PhD, with the research focus on two important nano-fabrication techniques namely, FEBID and EUV Lithography.
Under this consortium, a team of 15 Early Stage Researchers (ESRs) have been hired by different European research institutes and universities for their PhD, with the research focus on two important nano-fabrication techniques namely, FEBID and EUV Lithography.
I am ESR number 12 and my work will be on EUV Lithography. The topic of my research is "New material chemistry exploration for Extreme Ultraviolet Lithography". I have presented a synopsis of my project work below.
Photolithography has been the
major workhorse responsible for the advancement of the electronics industry
over the past few years. It is a nanofabrication process in which light is passed
through a patterned mask onto a substrate (Silicon wafer) coated with
light-sensitive material called ‘photoresist’. Then using a solvent called
‘developer’, the exposed part of the photoresist is removed and the pattern
(from mask) is replicated onto the substrate. The substrate is further
processed to produce integrated circuits (IC).
Photolithography is controlled by Rayleigh’s formula.
Currently, a deep ultraviolet (DUV) light source (wavelength λ=193 nm) is
used to produce patterns at a maximum resolution of 40 nm. To further push the
resolution down to 10 nm range, the wavelength of the source light needs to be
reduced to as low as 13.5 nm. This is when the process becomes Extreme
Ultraviolet (EUV) lithography.
EUV lithography, which is still in the research phase, is
deemed to be the future of the semiconductor industry. However, as we reduce
the wavelength to 13.5 nm, the energy of the photons becomes so high, that we
move from excitation chemistry (in DUV lithography) to radiation chemistry (in
EUV lithography). This changes the chemical interactions happening between the
photons and the photoresist. The obscure change in the chemistry results in the
underperformance of the currently available state-of-the-art photoresists.
The major problem associated with the current systems of
EUV resist is something known as RLS tradeoff. R stands for the resolution,
which is the smallest feature size that can be printed using that material. L
stands for line-edge-roughness, which is the deviation of line-space feature
from an ideal smooth shape. And S stands for Sensitivity, which is the minimum
exposure dose required to reach the resolution. It is proving to be impossible
to improve two of the parameters without exacerbating the third (hence, a
trade-off). This RLS trade-off is caused due to chemical variability at
nanoscale level. Only through the fundamental understanding of the chemistry of
the process, it will be possible to produce robust photoresist systems that can
work efficiently for EUV lithography. The objective of this research project is
to bridge this understanding.
The approach of this project is a combination of two ways:
1) To enhance our knowledge of fundamental chemistry happening at
the nanoscale level during EUV-patterning (through fundamental experiments such
as solid- and gas-phase reactions) and 2) To use that understanding to
design and characterize novel and robust EUV photoresists systems (through
understanding synthesis of novel EUV systems, EUV patterning using ASML NXE scanner,
CD-SEM analysis and RLS characterization).
Expected results from the project is to
get a better understanding of the fundamental chemistry and correlating that to
the critical parameters of novel EUV resist systems.
