Ion beam analyses

""Three different HF:alcohol solutions are investigated to etch native Si0 2 and passivate Si(100) surfaces with H which can the be desorbed at low temperature (T < 600'C). The resulting passivated Si(100) surfaces are compared using as a reference Si(100) passivated by a standard aqueous HF: solution (1:98 parts of HF: H2 0). After a modified RCA cleaning, Si(100) etched by HF:Methanol, HF:IPA, or HF:Ethanol, is characterized by Ion Beam Analysis (IBA), Tapping Mode Atomic Force Microscope (TMAFM), and Fourier Transform Infrared Spectroscopy (FTIR). The absolute coverage of 0 and C is measured by nuclear reaction analysis (NRA) combined with ion channeling at 3.05 MeV for 0 and 4.265 MeV for C. Hydrogen is measured via the elastic recoil detection (ERD) of 4He2+at 2.8 MeV.
Compared to aqueous HF, HF:alcohol passivates Si(100) leaving a lower 0 residue by an average factor of 0.62 and a similar C residue. H coverage is higher by an average factor of 1.43. Surface coverages are found to be reproducible in average by 1.4 x 1014 atoms/cm2 for C, and by 1.25 x 1014 atoms/cm2 for 0 when measured by IBA on samples identically processed. H coverage is reproducible within 5.5% when measured by ERD.
Selective area analysis by TMAFM shows that an increasing number of particulates is responsible for the apparent increase in root-mean -square (nns) surface roughness when the rms is measured over a whole image. Taking this effect into account, all passivated surfaces exhibit similar roughness when compared to the original Si(100) surface with little difference between
alcohols and with the reference aqueous HF solution. FTIR in the attenuation total reflection (ATR) mode detected SiHx species mostly as a
dihydride. Both IBA and FTIR detected significant levels of oxygen on surfaces passivated HF in alcohol and aqueous HF. This indicates that while Si(100) exhibits more H when passivated with HF in alcohol and can be desorbed at lower temperature than when treated with aqueous HF, H is
not bonded to Si only but likely bonds into a more complex surface termination, such as SiOH.""

Arsenic segregation at Si(lO0) surfaces during annealing (890–970°C) has been studied by medium energy ion scattering (MEIS), Rutherford backscattering spectrometry (RBS), ion scattering spectrometry (ISS), and Auger electron spectroscopy (AES). The unique depth resolution of MEIS revealed that arsenic segregated in a two-dimensional layer at the clean Si surface during annealing. For a surface with a native oxide the arsenic piled up at the Si/oxide interface. This segregation peak was no longer present on the Si surface after conventional contact opening. By metallizing arsenic junctions with Al:Si, 1% it was found that a segregation annealing step inhibited Al/Si interdiffusion. Diodes as shallow as 180 nm could be metallized without spiking.

In our previous work, we investigated the use of ion beam deposition (IBD) to grow epitaxial films at temperatures lower than those used in thermal processing (less than 500°C). Presently, we have applied IBD to the growth of dense (6.4×102 2 atom/cm3) silicon dioxide thin films at 400°C. Through these experiments we have found several clues to the microscopic processes leading to the formation of thin film phases by low energy ions. Using Monte‐Carlo simulations, we have found that low energy collision cascades in silicon have unique features such as a high probability of relocation events that refill vacancies as they are created. Our results show that the combination of a low defect density in low energy collision cascades with the high mobility of interstitials in covalent materials can be used to athermally generate atomic displacements tha can lead to ordering. These displacements can lead to epitaxial ordering at substrate temperatures below the minimum temperature necessary for molecular beam epitaxy (550°C). It can also lead to the formation of high quality silicon dioxide at temperatures well below that of thermal oxidation in silicon (i.e. <850°C). A growth model which we derive from these observations provides a fundamental understanding of how atomic collisions can be used to induce epitaxy or compound formation at low temperatures.

While developing a laboratory-scale micro-exposure tool for extreme ultraviolet (EUV) projection lithography which uses a laser-produced plasma emitting EUV pulsed radiation, we faced the problem of suppressing the various debris (ions, neutrals, particulate, clusters, droplets) emitted by the plasma target. The suppression of debris is a crucial task in the frame of EUV projection lithography, mainly because debris seriously limit both lifetime and performance of the expensive optics and filters put close to the plasma source.
In this paper we present the experimental measurements of main debris characteristics (velocity, size, charge, momentum, spectral energy, spatial distribution).  Then, we present the operating results of a patented debris mitigation system (DMS) specifically designed to suppress debris with the measured characteristics. We achieved reduction factors ∼ 800 for atoms and nm-size clusters, and ∼ 1600 for particles larger than 500 nm.  These results are at the forefront in this field.
The excellent performance of our DMS was a breakthrough to achieve a 90-nm patterning on commercial resists by our micro-exposure tool EUV projection lithography.