The development of multiple e-beam lithography equipment is seen as an alternative for next generation lithography.
However, similarly to EUV lithography, this technology faces important challenges in controlling the contamination of
the optics due to deposition of carbon layer induced by the outgassed chemical species from resist under electron
bombardment. An experimental setup was designed and built at LETI to study the outgassed species and observe the
carbon layer. In this setup, resist coated wafers 100 mm size are exposed under a 5 kV e-beam gun. During exposure, byproducts
from outgassed species are monitored with a Residual Gas Analyzer (RGA). The identification of outgassed
chemical species is done with an ex-situ TD-GC-MS analysis (ThermoDesorption-Gaz Chromatography-Mass
Spectrometry). In a second part of this investigation, we observed the contamination carbon layer growth induced by the
outgassing. Thereby, we fabricated a device which consists of a silicon membrane with micro-machined apertures.
During e-beam exposure, this device simulates the multiple parallel beams of the optic system of a maskless lithography
tool. The deposited contamination layer on device is then observed and thickness measured under SEM. In this paper, we
present the results of outgassing and contamination on 3 chemically amplified resists showing that contamination is not
directly dependent of the overall outgassing rate but on first order of the outgassing from Photo Acid Generator (PAG). It
also reports on the performance in reducing outgassing and contamination of applying a top-coat layer on top of the resist
and shows that reduction is more important for contamination than for outgassing.
The keystone to realize a monolithic integrated source on silicon with germanium is to optimize tensile strain and n-doping. In order to realize an integrated compact source, we demonstrate highly strained n-doped germanium microdisks obtained by two approaches using initially compressed silicon nitride (SiN) deposition. In the first approach, the microdisks are fabricated from relaxed Ge. In a second approach, we use tensile-strained Ge grown on a mismatched buffer layer, thus increasing the global strain in the Ge volume and lowering its gradient. A photoluminescence red-shift up to 450 nm is observed, corresponding to more than 1% biaxial strain.
Silicon is the basic material for the microelectronics industry. The predicted limits for electrical interconnects in electronic circuits favor the development of alternative solutions such as optical interconnects to transfer information. The silicon-based components are an alternative to realise these interconnections, providing that high speed and high efficiency integrated optoelectronic devices can be realized. In this work, we have fabricated two-dimensional photonic crystal (PC) microcavities on silicon-on-insulator (SOI). The samples contain self-assembled Ge/Si islands deposited in the upper silicon layer by chemical vapor deposition. The silicon layer thickness measures 0.3 mm. The photonic crystals consist of triangular lattices of air holes etched in the upper silicon layer of the SOI substrate. The period lattice measures 0.5 μm and the drilled holes had diameters between 0.3 and 0.45 μm. These structures exhibit a forbidden band around 1.3 - 1.5 μm in TE polarisation. Different photonic crystal hexagonal microcavities were processed and the optical properties are probed at room temperature with the Ge/Si island photoluminescence. Quality factors larger than 200 are measured for hexagonal microcavities. On the one hand, the presence of the PC improves the vertical extraction of light, and on the other hand, we show that a significant enhancement of the Ge/Si island photoluminescence (x 100) can be achieved in the 1.3 - 1.55 μm spectral region using the microcavities. These attractive results should allow to realise efficient light emitting-diodes in the near infrared.