ABSTRACT
In this work, we demonstrate a full process for fabricating high aspect ratio diffraction optics for extreme ultraviolet lithography. The transmissive optics consists in nanometer scale tungsten patterns standing on flat, ultrathin (100 nm) and highly transparent (>85% at 13.5 nm) silicon membranes (diameter of 1 mm). These tungsten patterns were achieved using an innovative pseudo-Bosch etching process based on an inductively coupled plasma ignited in a mixture of SF6 and C4F8. Circular ultra-thin Si membranes were fabricated through a state-of-the-art method using direct-bonding with thermal difference. The silicon membranes were sputter-coated with a few hundred nanometers (100-300 nm) of stress-controlled tungsten and a very thin layer of chromium. Nanoscale features were written in a thin resist layer by electron beam lithography and transferred onto tungsten by plasma etching of both the chromium hard mask and the tungsten layer. This etching process results in highly anisotropic tungsten features at room temperature. The homogeneity and the aspect ratio of the advanced pattern transfer on the membranes were characterized with scanning electron microscopy after focus ion beam milling. An aspect ratio of about 6 for 35 nm size pattern is successfully obtained on a 1 mm diameter 100 nm thick Si membrane. The whole fabrication process is fully compatible with standard industrial semiconductor technology.
ABSTRACT
In this work, silicon-rich silicon nitride (SRN) layers were deposited on a silicon wafer by microwave-assisted plasma-enhanced chemical vapor deposition (MW-PECVD) using NH(3) and SiH(4) as precursor gases. The Si excess in the as-deposited layers as determined by the Rutherford backscattering technique was controlled by varying the precursor gas ratio. We were able to produce silicon nanoparticles (Si-nps) in the silicon nitride (SiN(x)) layers upon thermal annealing at high temperature. Energy-filtered TEM (EFTEM), complemented by photoluminescence measurements, were used to identify the experimental parameters in order to reach a high density of well-separated Si-nps (3 nm). Our results show that the MW-PECVD method is a suitable deposition tool for the formation of Si-nps in thin SRN layers.
Subject(s)
Nanoparticles/chemistry , Nanostructures/chemistry , Silicon Compounds/chemistry , Silicon/chemistry , Ammonia/chemistry , NanotechnologyABSTRACT
This work reports on the structural and optical properties of multilayers composed of silicon dioxide (SiO2) and silicon rich silicon nitride (SRN) films. These nanometer scale layers have been alternately deposited by electron cyclotron resonance plasma enhanced chemical vapor deposition (ECR-PECVD) on quartz and silicon (Si) substrates. The samples have then been annealed at high temperature in order to obtain a crystallization of the Si atoms present in excess in the SRN films. The formation of crystalline Si has been witnessed by high resolution transmission electron microscopy (HREM) and micro-Raman measurements. Estimation of the Si-nanocrystal (Si-nc) sizes was possible by correlating the Raman's confinement model, the photoluminescence measurements and HREM imaging. The results clearly show that the band-gap of the Si-ncs formed can be controlled by this multilayer approach.
