Method for passivating at least a part of a substrate surface

A method for passivating at least a part of a surface of a semiconductor substrate, wherein at least one layer comprising at least one a-Si:H passivation layer is realized on said part of the substrate surface by: - generating a plasma (P) by means of at least one plasma source (3) mounted on the process chamber (5) at a distance (L) from the substrate surface, at least part of the plasma (P) being injected into the chamber (5) and achieving a supersonic speed; - contacting at least a part of the plasma (P), injected into the chamber (5), with the said part of the substrate surface; and - supplying at least one precursor suitable for passivation layer realization to the said part of the plasma (P) via a plurality of injection nozzles (19) of an injector device (17), such that the density of the precursor at each injection nozzle (19) is lower than 12x1022 particles/m3

Method for passivating at least a part of a substrate surface

A method for passivating at least a part of a surface of a semiconductor substrate, wherein at least one layer comprising at least one a-Si:H passivation layer is realized on said part of the substrate surface by: - generating a plasma (P) by means of at least one plasma source (3) mounted on the process chamber (5) at a distance (L) from the substrate surface, at least part of the plasma (P) being injected into the chamber (5) and achieving a supersonic speed; - contacting at least a part of the plasma (P), injected into the chamber (5), with the said part of the substrate surface; and - supplying at least one precursor suitable for passivation layer realization to the said part of the plasma (P) via a plurality of injection nozzles (19) of an injector device (17), such that the density of the precursor at each injection nozzle (19) is lower than 12x1022 particles/m3

Sign reversal of spin polarization in Co/Ru/Al2O3/Co magnetic tunnel junctions

Utilizing ultrathin Ru interfacial layers in Co/Al2O3/Co tunnel junctions, we demonstrate that not only does the tunnel magnetoresistance decrease strongly as the Ru thickness increases as found for Cu or Cr interlayers, in contrast, even the sign of the apparent tunneling spin polarization may be changed. Further, the magnitude and sign of the apparent polarization is strongly dependent on applied voltage. The results are explained by a strong density-of-states modification at the (interdiffused) Co/Ru interface, consistent with theoretical calculations and experiments on Co/Ru metallic multilayers and Co-Ru alloys

Silicon surface passivation by hot-wire CVD Si thin films studied in situ surface spectroscopy

Silicon thin films can provide an excellent surface passivation of crystalline silicon (c-Si) which is of importance for high efficiency heterojunction solar cells or diffused emitter solar cells with well-passivated rear surfaces. Hot-wire chemical vapor deposition (hotwire CVD) is an attractive method to synthesize Si thin films for these applications as the method is ion-bombardment free yielding good quality films over a wide range of deposition rates. The properties of the interface between Si thin films and H-terminated c-Si substrates have been studied during film growth by three complementary in situ techniques. Spectroscopic ellipsometry has been used to determine the optical properties, film thickness and surface roughness whereas information on the H-bonding modes and H-depth profile has been obtained by attenuated total reflection infrared spectroscopy. Second-harmonic generation (SHG), a nonlinear optical technique sensitive to surface and interface states, has been used to probe two-photon resonances related to modified Si-Si bonds at the interface. The observations have been correlated with ex situ lifetime spectroscopy experiments. On the basis of the results, the growth and surface passivation mechanism of the films will be discussed, including the role of defect states, built-in electric fields, (nanometer-level) epitaxial growth, influence of the substrate temperature, etc

Real-time study of α-Si:H/c-Si heterointerface formation and epitaxial Si growth by spectroscopic ellipsometry, infrared spectroscopy, and second-harmonic generation

The performance of many devices based on Si thin films deposited on crystalline Si (c-Si) is highly governed by interface quality. For many of these applications, only fully epitaxial films or fully amorphous films having an abrupt interface with the substrate are desired. However, the realization of these perfectly sharp interfaces and the mechanisms governing their formation are not fully understood yet. In this study, the interface formation between Si thin films and c-Si has been investigated by simultaneously applying three complementary optical techniques in real time during low temperature Si film growth. The films were deposited in a hot-wire chemical vapor deposition process by using both native oxide covered and H terminated Si(100) substrates. The formation of hydrogenated amorphous Si (a-Si:H), epitaxial Si, and mixed phase Si has been detected with spectroscopic ellipsometry by measuring the optical properties of the growing films. The evolution of the hydrogen content and hydrogen bonding configurations in the films has been monitored by attenuated total reflection infrared spectroscopy. A clear dependence of the hydrogen content on film morphology is observed with the amorphous films containing significantly more hydrogen. The surface and interface sensitive technique of second-harmonic generation (SHG) has been applied both spectroscopically and in real time. The SHG spectra of a-Si:H films on Si(100) obtained in the SHG photon energy range of 2.7–3.5 eV revealed a dominant contribution originating from the film/substrate interface related to E/E1 critical point (CP) transitions of c-Si. The real-time behavior of the SHG response is shown to strongly depend on differences in initial film morphology, which allows for identification of direct a-Si:H/c-Si heterointerface formation, nanometer-level epitaxial growth, and fully epitaxial growth at a very early stage of film growth. On the basis of the results obtained by the three optical techniques, the c-Si surface passivation mechanism by a-Si:H thin films is addressed and it is demonstrated that the combination of the techniques provides a profound method to control processes occurring during Si thin film growt

Optical properties of Y2O3 thin films doped with spatially controlled Er3+ by atomic layer deposition

We report in this work the optical properties of Er3+-doped Y2O3, deposited by radical enhanced atomic layer deposition. Specifically, the 1.53 µm absorption cross section of Er3+ in Y2O3 was measured by cavity ring-down spectroscopy to be (1.9±0.5)×10-20 cm2, about two times that for Er3+ in SiO2. This is consistent with the larger Er3+ effective absorption cross section at 488 nm, determined based on the 1.53 µm photoluminescence yield as a function of the pump power. X-ray photoelectron spectroscopy and Rutherford backscattering spectroscopy were used to determine the film composition, which in turn was used to analyze the extended x-ray absorption fine structure data, showing that Er was locally coordinated to only O in the first shell and its second shell was a mixture of Y and Er. These results demonstrated that the optical properties of Er3+-doped Y2O3 are enhanced, likely due to the fully oxygen coordinated, spatially controlled, and uniformly distributed Er3+ dopants in the host. These findings are likely universal in rare-earth doped oxide materials, making it possible to design materials with improved optical properties for their use in optoelectronic devices

Plasma Focused Ion Beam Tomography for Accurate Characterization of Black Silicon Validated by Full Wave Optical Simulation

Black silicon (BSi) is a branch of silicon material whose surface is specially processed to a micro/nanoscale structure, which can achieve ultra-low reflectance or ultra-high electrochemical reactivity. The diversity and complex surface structures of BSi make it challenging to commercialize BSi devices. Modeling and simulation are commonly used in the semiconductor industry to help in better understanding the material properties, predict the device performance, and provide guidelines for fabrication parameters’ optimization. The biggest challenge for BSi device modeling and simulation is obtaining accurate input surface morphological data. In this work, the 3D models of challenging BSi textures are compared as obtained by atomic force microscopy (AFM) and plasma focused ion beam (PFIB) tomography techniques. In previous work, the PFIB tomography workflow toward the application of surface topography is optimized. In this work, the 3D models obtained from both AFM and PFIB are comprehensively compared, by using the surface models as inputs for finite-difference time-domain-based optical simulation. The results provide strong evidence that PFIB tomography is a better choice for characterizing highly roughened surface such as BSi and provides surface 3D models with better reliability and consistency