J. W. Mayer

Band gap shift in the indium-tin-oxide films on polyethylene napthalate after thermal annealing in air

Indium-tin-oxide (ITO) thin films on polyethylene napthalate (PEN) with high carrier concentration (∼1021∕cm3) have been grown by electron-beam deposition without the introduction of oxygen into the chamber. The electrical properties of the ITO films (such as, carrier concentration, electrical mobility, and resistivity) abruptly changed after annealing in the air atmospheres. In addition, optical transmittance and optical band gap values significantly changed after heat treatment. The optical band gap narrowing behavior is observed in the as-deposited sample because of impurity band and heavy carrier concentration. The influence of annealing in air on the electrical and optical properties of ITO∕PEN samples can be explained by the change in the free electron concentration, which is evaluated in terms of the oxygen content. Rutherford backscattering spectrometry and x-ray photoelectron spectroscopy analyses are used to determine the oxygen content in the film. Hall effect measurements are used to determine...

Physical mechanisms behind the ion-cut in hydrogen implanted silicon

Hydrogen implanted silicon has been shown to cleave upon annealing, thus facilitating the transfer of thin silicon slices to other substrates, a process known as “ion-cut.” In our experiments 〈100〉 silicon wafers were implanted with 40 keV protons to a variety of ion doses ranging from 1×1016 to 1×1017 cm−2 and subsequently annealed at 600u2009°C. The samples were studied before and after annealing by a combination of Rutherford backscattering spectroscopy in channeling mode, elastic recoil detection analysis, atomic force microscopy, and electron microscopy. Mechanical stresses in the material, caused by proton irradiation, were determined by measuring changes in curvature of the silicon samples utilizing a laser scanning setup. For H doses of ⩾5×1016 cm−2 ion cutting in the form of “popping off” discrete blisters was obtained. Our analyses of the cleavage mechanisms had shown that the ion-cut location in silicon is largely controlled by the lattice damage that is generated by the H implantation process. At ...

Characterization of the physical and electrical properties of Indium tin oxide on polyethylene napthalate

Indium tin oxide (ITO) thin films, on polyethylene napthalate (PEN) of both good electrical and optical properties were obtained by radio-frequency sputtering. The optoelectronic properties of the ITO films on PEN substrate were evaluated in terms of the oxygen content and the surface morphology. Rutherford backscattering spectrometry analysis was used to determine the oxygen content in the film. Hall-effect measurements were used to evaluate the dependence of electrical properties on oxygen content. The results showed that the resistivity of the ITO film increases with increasing oxygen content. For an oxygen content of 1.6×1018–2.48×1018atoms∕cm2, the resistivity varied from 0.38×10−2to1.86×10−2Ωcm. Typical resistivities were about ∼10−3Ωcm. UV-Vis spectroscopy and atomic force microscopy measurements were used to determine the optical transmittance and surface roughness of ITO films, respectively. Optical transmittances of ∼85% were obtained for the ITO thin films. Our results revealed that substrate r...

Orientation dependence of blistering in H-implanted Si

The orientation effect on blistering phenomenon in H implanted Si was studied for (100), (111), and (110) Si wafers. It was found that substrate orientation has no observable effects on the underlying blistering mechanisms. Furthermore, the implantation damage, Si–H complex formation in as-implanted samples and surface roughness of the transferred layer appeared to be unaffected by the orientation. However, the blistering kinetics are orientation dependent, with (100) Si having the fastest blistering rate, and (110) Si the slowest. This dependence was attributed to the different density of ruptured Si–Si bonds of different orientations. The magnitude of the observed in-plane compressive stress in the H-implanted Si wafers is rationalized in terms of the formation of platelets in the samples.

Dopant activation in ion implanted silicon by microwave annealing

Microwaves are used as a processing alternative for the electrical activation of ion implanted dopants and the repair of ion implant damage within silicon. Rutherford backscattering spectra demonstrate that microwave heating reduces the damage resulting from ion implantation of boron or arsenic into silicon. Cross-section transmission electron microscopy and selective area electron diffraction patterns demonstrate that the silicon lattice regains nearly all of its crystallinity after microwave processing of arsenic implanted silicon. Sheet resistance readings indicate the time required for boron or arsenic electrical activation within implanted silicon. Hall measurements demonstrate the extent of dopant activation after microwave heating of implanted silicon. Physical and electrical characterization determined that the mechanism of recrystallization in arsenic implanted silicon is solid phase epitaxial regrowth. The boron implanted silicon samples did not result in enough lattice damage to amorphize the s...

Investigation of the cut location in hydrogen implantation induced silicon surface layer exfoliation

The physical mechanisms of hydrogen induced silicon surface layer exfoliation were investigated using the combination of ion beam analysis, secondary ion mass spectroscopy (SIMS), scanning electron microscopy (SEM), and cross section transmission electron microscopy (XTEM). A 〈100〉 oriented silicon wafer was implanted with 175 keV protons to a dose of 5×1016 cm−2. The implanted wafer was bonded to a silicon oxide capped 〈100〉 silicon wafer and then heated to an elevated temperature of 600u200a°C to produce exfoliation. The hydrogen-implanted sample was analyzed in the as-implanted state as well as after the cleavage of the silicon wafer. The depth distribution of the implantation damage was monitored by Rutherford backscattering spectrometry (RBS) in channeling condition and XTEM imaging. Elastic recoil detection analysis and SIMS was performed to examine the hydrogen depth distribution. Cross section SEM and RBS channeling was used to measure the thickness of the exfoliated layer after cleavage. A comparison...

A comparative study of Hillock formation in aluminum films

Abstract Studies were conducted to evaluate the performance of a variety of aluminum alloys with respect to hillock formation. Specifically, the effects of film composition, deposition temperature, and underlayer on hillock formation were investigated. The film compositions included pure Al, Al with 1.5 wt.% Cu (or AlCu), AlCu with 0.2 wt.% W, and AlCu with 0.4 wt.% W. These films were sputter deposited at 300 °C and 450 °C on either oxide- or Ti-W-coated Si substrates. Following deposition, the films were annealed in air for 20 min at 450 °C. For all film compositions, the deposition temperature had the most significant effect on the hillock density. For a given deposition temperature, the addition of Cu to pure Al drastically reduced the hillock density, but the addition of W to AlCu increased the hillock density. The effect of the underlayer on the hillock density was negligible. Cross-sections of the hillocks showed that they were solid from the bottom interface to the top surface, and no voids were found near the hillocks. The grain size did not have a significant effect on the hillock density. However, a correlation between increasing (111) film texture and decreasing hillock density was observed.

Effect of various annealing environments on electrical and optical properties of indium tin oxide on polyethylene napthalate

The effect of different annealing ambients on the electrical and optical properties of indium tin oxide (ITO) on polyethylene napthalate (PEN) has been investigated. ITO layers of different carrier concentrations have been prepared by radio frequency sputtering followed by annealing in either 5% H2∕Ar, oxygen, or air at 150°C for 2h. The carrier concentration of the ITO films increased with heat treatment in the 5% H2∕Ar ambient. However, the carrier concentration of the ITO films decreased with heat treatment in oxygen and air atmospheres, respectively. Different annealing ambients affect the electrical properties of ITO/PEN samples by changing the oxygen vacancy in the ITO layer. Electrical mobilities were found to be affected by the carrier concentration. These experimental mobility values were in good agreement with those obtained from a theoretical ionized impurity scattering mechanism model. Optical transmittances of ∼86% were obtained for the ITO thin films and the optical band gap is about 3.15eV ...

Single crystal Si layers on glass formed by ion cutting

The process of ion cutting was used to integrate single crystalline Si layers on glass for potential active matrix flat panel display and other applications. It was found that p-Si wafers implanted at 100–150 ° C with H with a dose in the order of a few times 10 16 cm −2 could be readily bonded to glass substrates when both of the surfaces were properly treated and activated. The as-implanted Si wafer surface was converted from p type to n type. Upon bonding at room temperature, annealing (300 ° C ) and exfoliation (450 ° C ), the transferred Si layer on glass and the as-exfoliated surface of the implanted Si wafer remained n type. A highly defective region was observed near the top of the Si layer on glass, however the crystalline quality was nearly defect free in the deeper region of the layer. Annealing at sequentially higher temperatures led to the recovery of p type conductivity at ∼600–650 ° C . The type conversion and the subsequent annealing behavior observed on the samples were rationalized in terms of ion enhanced oxygen diffusion and the presence of H-related shallow donors in the Si.

Passivation of Cu via refractory metal nitridation in an ammonia ambient

Cu-(27at.% Ti) and Cu-(26at.% Cr) alloys codeposited on silicon dioxide substrates were isochronally annealed for 30 min at 400–700 °C in a flowing NH3 ambient. In the Cu-Ti alloy, Ti segregates to the free surface to form a TiNx(O) layer and also to the alloy-SiO2 interface to form a Ti5Si3TiOw bilayer structure. Therefore the resulting structure is an almost completely dealloyed Cu layer located between a surface oxygen-rich Ti nitride and Ti-silicide/Ti-oxide bilayer interfacial structure. In the Cu-Cr alloy system, Cr seems to migrate only to the free surface to form a CrNx passivation layer. A 45 nm Al film was deposited after nitridation, whereupon a second anneal was performed to evaluate these nitride layers as diffusion barriers. The Cr-nitride diffusion barrier is stable up to 600 °C compared with Ti nitride that fails at 500 °C. The Cu-Cr nitrided samples also showed an overall lower sheet resistance.