T. Höchbauer

Influence of interfaces on the storage of ion-implanted He in multilayered metallic composites

We studied ion beam mixing and He accumulation in Cu∕Nb multilayer thin films after 33keV He implantation at room temperature to a dose of 1.5×1017atoms∕cm2. Multilayered thin films consisting of alternating Cu and Nb layers were produced by magnetron sputtering. Two types of samples, one with an individual layer thickness of 4nm and another with 40nm were examined. The Cu∕Nb samples were analyzed in the as-deposited state, after He ion implantation, as well as after post-implantation annealing. The ion beam mixing of the interface structure was monitored by Rutherford backscattering spectrometry and cross-section transmission electron microscopy imaging. Elastic recoil detection analysis was performed to examine the helium concentration depth distribution. Scanning electron microscopy was employed to investigate He blister formation upon annealing. A comparison of the results deduced from the methods listed above reveals a very high morphological stability of the nanolayered structure. The nanolayered st...

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 600 °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 ...

Nucleation and growth of platelets in hydrogen-ion-implanted silicon

H ion implantation into crystalline Si is known to result in the precipitation of planar defects in the form of platelets. Hydrogen-platelet formation is critical to the process that allows controlled cleavage of Si along the plane of the platelets and subsequent transfer and integration of thinly sliced Si with other substrates. Here we show that H-platelet formation is controlled by the depth of the radiation-induced damage and then develop a model that considers the influence of stress to correctly predict platelet orientation and the depth at which platelet nucleation density is a maximum.

Cold ion-cutting of hydrogen implanted Si

Abstract The strength of the H-implanted layer has been measured in 〈1 0 0〉 , 〈1 1 1〉 and 〈1 1 0〉 oriented Si wafers using the crack opening method. The required annealing temperature for mechanical layer transfer increases in the order 〈1 0 0〉 , 〈1 1 1〉 and 〈1 1 0〉 . The damage induced by the implantation has been studied by Rutherford backscattering in the channeling mode (RBS/C). The same methods have been used to investigate the influence of boron and arsenic doping on the mechanical exfoliation. Boron doping reduces the strength of the H-implanted layer thereby enabling mechanical layer transfer at temperatures below 200 °C. We found that the exfoliation takes place closer to the wafer surface in highly boron doped Si as compared to the undoped Si. The RBS damage peak also appears to move closer to the surface when the boron concentration of the H-implanted layer is >1019 cm−3. No lowering of the exfoliation temperature was observed for compensated and arsenic doped Si layers. We suggest that the lowering of the exfoliation temperature with increasing boron doping is related to Si–H bonds associated with the neutralization of shallow acceptors by hydrogen.

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.

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 600 °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...

Investigation of plasma hydrogenation and trapping mechanism for layer transfer

Hydrogen ion implantation is conventionally used to initiate the transfer of Si thin layers onto Si wafers coated with thermal oxide. In this work, we studied the feasibility of using plasma hydrogenation to replace high dose H implantation for layer transfer. Boron ion implantation was used to introduce H-trapping centers into Si wafers to illustrate the idea. Instead of the widely recognized interactions between boron and hydrogen atoms, this study showed that lattice damage, i.e., dangling bonds, traps H atoms and can lead to surface blistering during hydrogenation or upon postannealing at higher temperature. The B implantation and subsequent processes control the uniformity of H trapping and the trap depths. While the trap centers were introduced by B implantation in this study, there are many other means to do the same without implantation. Our results suggest an innovative way to achieve high quality transfer of Si layers without H implantation at high energies and high doses.

Thermal stability of diamondlike carbon buried layer fabricated by plasma immersion ion implantation and deposition in silicon on insulator

Diamondlike carbon (DLC) as a potential low-cost substitute for diamond has been extended to microelectronics and we have demonstrated the fabrication of silicon on diamond (SOD) as a silicon-on-insulator structure using plasma immersion ion implantation and deposition in conjunction with layer transfer and wafer bonding. The thermal stability of our SOD structure was found to be better than that expected for conventional DLC films. In the work reported here, we investigate the mechanism of the enhanced thermal stability. We compare the thermal stability of exposed and buried DLC films using Raman spectroscopy and x-ray photoelectron spectroscopy (XPS). Our Raman analysis indicates that the obvious separation of the D and G peaks indicative of nanocrystalline graphite emerges at 500°C in the exposed DLC film. In contrast, the separation appears in the buried DLC film only at annealing temperatures above 800°C. Analysis of the XPS C1s core-level spectra shows that the (sp3+C–H) carbon content of the unprot...

Hydrogen blister depth in boron and hydrogen coimplanted n-type silicon

We have studied the depths of hydrogen surface blisters in 〈100〉 n-type silicon, which formed after B+H coimplantation and heat treatment. The silicon substrates had three different dopant levels, ranging from 1014 to 1019 cm−3. The Si substrates were first implanted with B+ ions at 147 keV to a dose of 1015 cm−2. Some of the B-implanted samples were left in their as-implanted state; others were electrically activated by a rapid thermal anneal. The samples were then implanted with 40 keV H+ to a dose of 5×1016 cm−2. At the chosen implantation energies, the hydrogen- and boron-implantation distributions overlap. Following H+ implantation, all the samples were vacuum annealed and examined by ion-beam analysis and scanning electron microscopy. In all cases, the blister depth was consistently found to be strongly correlated with the H damage profile rather than the H or B concentration profiles.

Role of strain in the blistering of hydrogen-implanted silicon

The authors investigated the physical mechanisms underlying blistering in hydrogen-implanted silicon by examining the correlation between implantation induced damage, strain distribution, and vacancy diffusion. Using Rutherford backscattering, scanning electron microscopy, and atomic force microscopy, they found that the depth of blisters coincided with that of maximum implantation damage. A model based on experimental results is presented showing the effect of tensile strain on the local diffusion of vacancies toward the depth of maximum damage, which promotes the nucleation and growth of platelets and ultimately blisters.