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. © 2005 American Institute of Physics

Study on fatigue and energy-dissipation properties of nanolayered Cu/Nb thin films

Energy dissipation and fatigue properties of nano-layered thin films are less well studied than bulk properties. Existing experimental methods for studying energy dissipation properties, typically using magnetic interaction as a driving force at different frequencies and a laser-based deformation measurement system, are difficult to apply to two-dimensional materials. We propose a novel experimental method to perform dynamic testing on thin-film materials by driving a cantilever specimen at its fixed end with a bimorph piezoelectric actuator and monitoring the displacements of the specimen and the actuator with a fibre-optic system. Upon vibration, the specimen is greatly affected by its inertia, and behaves as a cantilever beam under base excitation in translation. At resonance, this method resembles the vibrating reed method conventionally used in the viscoelasticity community. The loss tangent is obtained from both the width of a resonance peak and a free-decay process. As for fatigue measurement, we implement a control algorithm into LabView to maintain maximum displacement of the specimen during the course of the experiment. The fatigue S-N curves are obtained

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. © 2006 American Institute of Physics

Microwave enhanced ion-cut silicon layer transfer

Microwave heating has been used to decrease the time required for exfoliation of thin single-crystalline silicon layers onto insulator substrates using ion-cut processing. Samples exfoliated in a 2.45 GHz, 1300 W cavity applicator microwave system saw a decrease in incubation times as compared to conventional anneal processes. Rutherford backscattering spectrometry, cross sectional scanning electron microscopy, cross sectional transmission electron microscopy, and selective aperture electron diffraction were used to determine the transferred layer thickness and crystalline quality. The surface quality was determined by atomic force microscopy. Hall measurements were used to determine electrical properties as a function of radiation repair anneal times. Results of physical and electrical characterizations demonstrate that the end products of microwave enhanced ion-cut processing do not appreciably differ from those using more traditional means of exfoliation. © 2007 American Institute of Physics

Plasma immersion ion implantation of complex-shaped objects: an experimental study on the treatment homogeneity

Plasma immersion ion implantation is a technique which is often quoted to treat complex-shaped objects homogeneously. The present study shows that this is not necessarily the case, if the plasma conditions are not chosen in a very narrow predetermined window. It is not only important to know the dose distribution of the implanted ions across a three-dimensional object, but also the intensity of sputter etching depending on the position. Therefore, two different techniques, sensitive to these issues have been applied. The objects investigated are macro-trenches with different aspect ratios. U-shaped stainless steel sample holders with different trench widths have been lined with silicon wafer segments. Additionally a Ta metal strip, coated with a Ta2O5 layer, has been folded into the sample holders. These trenches have been treated in an argon plasma. The implanted Ar ion dose has been determined by Rutherford backscattering spectrometry of the Si pieces. The amount of sputtered material could be evaluated by determining the colour change of the Ta2O5/Ta strips. The colour of the oxide on the metal is very sensitive to the oxide thickness. It is shown that under the conditions applied, the treatment is not homogeneous. A larger amount of Ar is implanted at the trench top side compared to the trench bottom. The trench side walls are hardly affected by ion implantation. The sputter results are different from the implantation ones. It is shown that the trench bottom is most affected by sputtering, considerably more than the top side. The inner side walls of the trenches are for all aspect ratios also hardly affected by sputtering. The results are explained in terms of the sheath dimensions and the expansion of the sheath as well as by the three-dimensional geometry of the sample holders

Plasma hydrogenation of strain-relaxed SiGe/Si heterostructure for layer transfer

The use of plasma hydrogenation for relaxed SiGe layer transfer is demonstrated. It is found that the interface of a strain-relaxed SiGe/Si heterostructure is effective in trapping H during plasma hydrogenation. Long microcracks observed at the interface due to the trapping of indiffused H indicate the distinct possibility of transferring the overlayer using the ion-cutting technique. Our results suggest that interfacial defects induced by the He implantation relaxation process trap the indiffusing H atoms and lead to interfacial cracks during hydrogenation or upon postannealing at higher temperatures. It is further noted that trapping of H at the interface is possible only in strain-relaxed structures. Without strain relaxation, H atoms introduced by plasma hydrogenation get trapped just below the sample surface and form a band of shallow platelets. Without the need for high-dose high-energy ion implantation, our results suggest an effective way for high-quality strain-relaxed SiGe layer transfer. The technique has potential for application in the fabrication of SiGe-on-insulator strained Si epitaxial layer and related structures. (C) 2004 American Institute Of Physics

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. (C) 2005 American Institute of Physics