The RF noise in 0.18-m CMOS technology has been measured and modeled. In contrast to some other groups, we find only a moderate enhancement of the drain current noise for shortchannel MOSFETs. The gate current noise on the other hand is more significantly enhanced, which is explained by the effects of the gate resistance. The experimental results are modeled with a nonquasi-static RF model, based on channel segmentation, which is capable of predicting both drain and gate current noise accurately. Experimental evidence is shown for two additional noise mechanisms: 1) avalanche noise associated with the avalanche current from drain to bulk and 2) shot noise in the direct-tunneling gate leakage current. Additionally, we show low-frequency noise measurements, which strongly point toward an explanation of the 1 noise based on carrier trapping, not only in n-channel MOSFETs, but also in p-channel MOSFETs.

We have investigated the process of thin film separation by gas ion implantation and wafer bonding, as well as the more basic phenomenon of blistering, on which the technique is based. We show that when H and He gas implants are combined they produce a synergistic effect which enables thin-film separation at a much lower total implantation dose than that required for either H or He alone. By varying the H and He implantation doses we have been able to isolate the physical and chemical contributions of the gases to the blistering processes. We find that the essential role of H is to interact chemically with the implantation damage and create H-stabilized platelet-like defects, or microvoids. The efficiency of H in this action is linked to its effective lowering of the silicon internal surface energy. The second key component of the process is physical; it consists of diffusion of gas into the microvoids and gas expansion during annealing, which drives growth and the eventual intersection of the microvoids to form two continuous separable surfaces. He is more efficient than H for this process since He does not become chemically trapped at broken bonds and thus segregates into microvoids more readily. In particular, we have demonstrated that a 1×1016 cm−2 He dose in combination with a 7.5×1015 cm−2 H dose are sufficient to shear and transfer a thin silicon film onto a handle wafer after bonding the two wafers together.

Since the first report of the Unibond process,l there has been much interest in reproducing Si exfoliation by H implantation and in understanding the mechanism leading to such a remarkably uniform shearing. We have previously demonstrated that, contrary to the initial speculation? there are in fact three distinct aspects to the process3 i) The generation of damage to the crystalline material by the implantation; ii) The unique surface chemistry of hydrogen and silicon that drives the thermal evolution of this damage region and; iii) The creation of internal pressure that ultimately causes exfoliation of the overlying Si layer. Therefore, a detailed understanding of the exfoliation mechanism involves the study of initial damage, of H-passivation of various internal structures and of the mechanical forces exerted by trapped gases as a function of hydrogen implantation doseldepth and annealing temperature. In this work, we have used different hydrogen implantation conditions (ion energies ranging from 1 V to 1 MeV and substrate crystallographic orientations) as well as co-implantation of a variety of other elemental species, in combination with novel spectroscopic configurations, to further explore these different mechanistic aspects.Infrared spectroscopy has played a key role in elucidating the microscopic details of the process, due to its high sensitivity and selectivity and inherent non-destructiveness. However, the frequency range accessible was limited to above 1500 cm-1 so that only the Si-H stretching vibrations could be observed. Recently, we have developed novel optical configurations that allow probing of the Si-H bending modes (at -600-650 cm-1) and scissor modes (850-910 cm-I), allowing definitive identification of the different defect modes. Using this approach, in combination with a variety of other techniques, we have been able to definitively show that exfoliation consists of the following distinct mechanistic steps: Above the critical dose of 6 x 1016/cm2, the IR spectrum shows evidence for monohydride-terminated, multi-vacancy defects that are typically found in hydrogenated amorphous silicon. The formation of such a "multivancy" defect region is critical to exfoliation, because it allows both formation of agglomerated defects and the evolution of molecular H2. These defects, in turn, develop into (100) and (1 11) internal cracks which act as traps for the H2 leading to the build-up of internal pressure and subsequent shearing. It is the synergetic combination of H-passivation of internal surfaces and H2 pressure within these intemal cracks that leads to the shearing in the presence of the joined wafer, that acts as a mechanical stiffener. Importantly, in the absence of the stiffener, the surface 'blisters'; in the absence of sufficient damage (below the critical dose), the hydrogen diffuses away from the implanted region, preventing exfoliation.Recent experiments4 have isolated the physical and chemical contributions to exfoliation by co-implanting He, Li and Si along with H and demonstrated that...

The recently observed phenomenon of boron uphill diffusion during low-temperature annealing of ultrashallow ion-implanted junctions in silicon has been investigated. It is shown that the effect is enhanced by preamorphization, and that an increase in the depth of the preamorphized layer reduces uphill diffusion in the high-concentration portion of boron profile, while increasing transient enhanced diffusion in the tail. The data demonstrate that the magnitude of the uphill diffusion effect is determined by the proximity of boron and implant damage to the silicon surface.

Infrared spectroscopy and secondary ion mass spectrometry are used to elucidate the mechanism by which co-implantation of He with H facilitates the shearing of crystalline Si. By studying different implant conditions, we can separate the relative contributions of damage, internal pressure generation, and chemical passivation to the enhanced exfoliation process. We find that the He acts physically as a source of internal pressure but also in an indirect chemical sense, leading to the reconversion of molecular H2 to bound Si–H in “VH2-like” defects. We postulate that it is the formation of these hydrogenated defects at the advancing front of the expanding microcavities that enhances the exfoliation process.