Diffusion of B in amorphous Si is known to be four orders of magnitude higher than in crystalline Si. The effect of Ge at low concentrations on B diffusion in the amorphous phase is unknown. 1.5μm thick relaxed layers of varying SiGe alloys (0, 6, 12, and 100at.% Ge) were grown on Si. After growth the layer was amorphized to a depth of 0.8μm using a 500keV, 5×1015ion∕cm2 Si+ implant at 77K. Next a 500eV, 1×1015ions∕cm2 B+ implant was introduced. The amorphous SiGe was recrystallized at temperatures between 300 and 600°C and the B diffusion during solid phase epitaxial regrowth was studied using dynamic secondary ion mass spectrometry. Comparison of B diffusivities for amorphous Si and amorphous Si0.88Ge0.12 revealed similar activation energies (2.7 and 2.8eV, respectively) and preexponential factors (0.8 and 4.8cm2∕s, respectively). The negligible change in B diffusion in amorphous SiGe at low Ge concentrations is similar to reports on B diffusivity for strain-relaxed crystalline SiGe alloys with Ge content. These results suggest that Ge is not an effective trap for B in the amorphous phase.

The impact of different process parameters, namely, the trench etch depth, the total epitaxial SiGe thickness, and the epi elevation, on the leakage current of recessed Si0.8Ge0.2 source/drain junctions has been systematically investigated. Besides the behavior of the forward and the reverse currents, attention is also given to the temperature dependence of the leakage current. It is found that both the bulk and the peripheral leakage current density increase strongly with increasing etch depth. Empirically, an exponential dependence has been observed between the area leakage current density at -1 V and the distance d(j) between the Si0.8Ge0.2-Si interface and the electrical p-n junction, whereby an increase by 1 dec for every 43 nm of reduction in d(j) occurs. This can be understood by the fact that the responsible defects originate mainly at the SiGe-Si interface. The perimeter current density shows for certain process splits an exponential dependence on the total thickness of the epitaxial layer t(SiGe), with an increase by a decade for every 50 nm increase in thickness. Also, the generation and recombination lifetimes have been studied in order to determine an effective energy level of the electrically active defects. (c) 2007 The Electrochemical Society.

The authors present a study on the layout dependence of the silicon-germanium source/drain (Si1-xGex S/D) technology. Experimental results on Si1-xGex S/D transistors with various active-area sizes and polylengths are combined with stress simulations. Two technologically important configurations are investigated: the nested transistor, where a polygate is surrounded by other gates, and isolated transistors, where the active area is completely surrounded by isolation oxide. The channel stress, caused by epitaxial Si1-xGex is reduced substantially when the active area is decreased from a large size towards typical values for advanced CMOS technology nodes. Nested transistors with longer gate lengths are more sensitive towards layout scaling than shorter gates. Increasing recess depth and germanium concentration gives larger channel stress, but does not change layout sensitivity. Increased lateral etching leads to higher stress, as well as to reduced layout sensitivity. In small-size transistors, there exists an optimal recess depth, beyond which the stress in the channel will not increase further. For isolated transistor structures, the interaction between Si1-x Gex and the isolating oxide can even lead to stress reduction when the recess depth is increased. When technology advances, active-area dimensions will be scaled together with gate lengths and widths. For typical sizes of advanced silicon CMOS Si1-xGe x S/D transistors, simulations indicate that the channel stress can be maintained in future technology nodes

In this paper, the impact of several processing parameters, like the etch depth and elevation of the epitaxial Si 0.8 Ge 0.2 layer on the current-voltage (I-V) characteristics of recessed Source/Drain p + -n junctions is studied. It is shown that the area leakage current density is a strong function of the position of the junction with respect to the SiGe/Si interface. The highest area leakage current density is found for the heterojunctions, which can be explained by the presence of extended defects, generating excess carriers in the depletion region in the silicon substrate. The corresponding perimeter leakage current density is also highest for the highest etch depths. In addition, for some splits an empirical exponential dependence on the total epi layer thickness has been observed.

Several dry and wet surface treatment methods are explored for a selective SiGe epitaxial film used to fabricate embedded SiGe pMOSFETs. Pre-clean conditions for the device wafers used in this study were limited by a realistic CMOS process window with tight thermal and chemical budgets due to dopant diffusion and hardmask erosion concerns. The effectiveness of these pre-clean methods is evaluated by SiGe epitaxial film quality and SIMS profiles of key residual contaminants such as C and O at the SiGe–Si substrate interface. As an effective low-temperature dry surface treatment, chemical bake in HCl/H2 at temperature below 800 °C is found to reduce interface C and O peak concentrations by an order of magnitude. Wet clean in multiple cycles of DIW-O3 (ozonated water), SC1 and diluted HF (DHF) is also presented to prepare epitaxial growth surfaces with accumulated damage and chemical residues from previous process steps. SiGe epitaxial film morphology is also observed to improve by increasing DHF clean time. For further improvement of film quality on the most difficult surfaces, Si seed layer was employed to initiate SiGe film nucleation and yield smooth film growth.

Recessed Si/sub 0.8/Ge/sub 0.2/ source/drain (S/D) and a compressive contact etch-stop layer have been successfully integrated resulting in nearly 200% improvement in hole mobility. This is the largest reported process-induced hole mobility enhancement to the authors' knowledge. This letter demonstrates that a drive-current improvement from recessed Si/sub 0.8/Ge/sub 0.2/ plus the compressive nitride layer are in fact additive. Furthermore, it shows that the mobility enhancement is a superlinear function of stress, leading to larger than additive gains in the drive current when combining several stress sources.

Common symptoms of neuromuscular disease (NMD) include weakness, difficulty walking, contractures, and scoliosis, all of which can contribute to chronic pain. This study was designed to address the gap in our understanding of the occurrence and impact of pain in youths with NMD. A convenience sample of 33 youths from the greater Seattle metropolitan area that have a primary diagnosis of NMD was obtained for this study through mailings from a children’s hospital, public postings, and referrals. The semi-structured interviews took place over-the phone or in person. The participants ranged in age from nine to twenty years (mean 15.0 3.0) and 60% were male. The majority of youths had a diagnosis of Duchenne muscular dystrophy (n=10, 30%), followed by myotonic dystrophy (n=6, 18%) and Charcot-Marie Tooth neuropathy (n=5, 15%). Participants completed several questionnaires that were developed for this study including demographic and disability-specific information, an eleven-point numerical rating scale for pain intensity, questions from the Child Health Questionnaire and a modified Brief Pain Inventory interference scale. Fifty eight percent of the youths reported experiencing chronic pain (average 2.7 on a scale of 0-10) and 67% indicated they experienced pain daily or weekly. Pain in the following body locations were the most frequently reported: back (68%), legs (63%), buttocks/hips (53%), and feet (53%). Pain interfered most with mobility, school, work or chores, and general activity as measured by the modified Brief Pain Inventory. Parents of 68% of the youths have sought treatment for their child’s pain and have tried non-steroidal anti-inflammatories (71%), acetaminophen (58%), and physical/occupational therapy (46%). These findings indicate the need for more specific inquiries into the chronic pain experiences of youths with NMD. Common symptoms of neuromuscular disease (NMD) include weakness, difficulty walking, contractures, and scoliosis, all of which can contribute to chronic pain. This study was designed to address the gap in our understanding of the occurrence and impact of pain in youths with NMD. A convenience sample of 33 youths from the greater Seattle metropolitan area that have a primary diagnosis of NMD was obtained for this study through mailings from a children’s hospital, public postings, and referrals. The semi-structured interviews took place over-the phone or in person. The participants ranged in age from nine to twenty years (mean 15.0 3.0) and 60% were male. The majority of youths had a diagnosis of Duchenne muscular dystrophy (n=10, 30%), followed by myotonic dystrophy (n=6, 18%) and Charcot-Marie Tooth neuropathy (n=5, 15%). Participants completed several questionnaires that were developed for this study including demographic and disability-specific information, an eleven-point numerical rating scale for pain intensity, questions from the Child Health Questionnaire and a modified Brief Pain Inventory interference scale. Fifty eight percent of the youths reported experiencing chronic pain (average 2.7 on a scale of 0-10) and 67% indicated they experienced pain daily or weekly. Pain in the following body locations were the most frequently reported: back (68%), legs (63%), buttocks/hips (53%), and feet (53%). Pain interfered most with mobility, school, work or chores, and general activity as measured by the modified Brief Pain Inventory. Parents of 68% of the youths have sought treatment for their child’s pain and have tried non-steroidal anti-inflammatories (71%), acetaminophen (58%), and physical/occupational therapy (46%). These findings indicate the need for more specific inquiries into the chronic pain experiences of youths with NMD.

This paper studies the sensitivity of stress-enhanced transistor performance to layout variations. Stress simulations and mobility models are calibrated and verified for test structures with SiGe source/drain as a stressor. The role of STI on the stress transfer is explored. The numerical results show that variations of 15% in drive currents and of 44% in hole mobility due to layout induced stress variations can occur in the cases studied. These deviations need to be taken into account in circuit design or to be compensated via layout modification.

Hole mobility is found to more than double in fabricated p-MOSFETs with SiGe source/drain due to longitudinal compressive stress in the channel exceeding 1 GPa. The maximum observed low-field mobility enhancement is 140% at a simulated stress level of 1.45 GPa. The mobility enhancement is approximately linear with stress at moderate levels but becomes super-linear above 1 GPa. An important consequence of this behavior is that for moderate stress levels, an average channel stress can be used to estimate the performance of transistors with a nonuniform stress distribution across the channel width. Two alternative approaches to model stress-enhanced hole mobility are suggested. Analysis of the physical effects behind the experimental observations reveals the relative roles of band repopulation and mass modulation. In addition, previously published wafer bending experiments with compressive stress levels below 400 MPa are used to implicitly verify the accuracy of the stress simulations.

We present a study on the layout dependence of a SiGe S/D PMOSFET technology. While 65% increase in drive current is obtained for 45nm gate length transistors with large active areas, measurements and simulations show that this improvement may be seriously degraded when transistor dimensions, such as the source-drain length (L-s/d) and the device width are further scaled.TDDB and NBTI measurements show that the oxide reliability is not degraded for this technology.

We present the results of a study on the impact of process parameters on the performance of strain enhanced pMOSFETs with recessed SiGe S/D. Recess depth, channel length, layout sensitivity, and their subsequent impact on strain and hole mobility are explored. Micro-Raman Spectroscopy (muRS), process simulations, device simulations, and electrical results are presented. A 30% improvement in drive current is demonstrated.

Little research has examined the nature and scope of pain problems among youth with spinal cord injuries (SCI). A convenience sample of youth with SCI were administered in-person structured interviews that included demographics, the Wong-Baker Faces Pain Rating Scale, a modified Brief Pain Inventory (BPI), the Child Health Questionnaire (CHQ), and additional pain descriptors. Data from 10 youth have been collected. The majority of the participants were female (60%) and with a mean age of 15.4 years (SD=4.0). Fifty percent of the injuries were due to motor vehicle accidents, 20% to sports injuries, 10% to a fall, and 20% to other causes. Forty percent were complete injuries, 40% were incomplete injuries, and 20% were unknown. Sixty percent of the participants sustained cervical injuries, 30% thoracic, and 10% lumbar. All of the youth reported chronic pain with a mean pain intensity of 3.0 (range, 1-4) on an 11-point numerical rating scale. The mean pain duration was 6 hrs 49 min (range, 2 min to constant). The most common pain locations were the back (70%), bottom/hips (60%), and head (50%). Using a modified BPI, the greatest pain interference occurred with mood (mean 2.33, range 0-6), sleep (mean 2.3, range 0-8), and recreation (mean 1.9, range 0-8). Regarding bodily pain or discomfort in the past 4 weeks, 50% noted no pain to mild pain and 50% reported moderate to severe pain on the CHQ. The frequency of bodily pain or discomfort in the past 4 weeks as noted on the CHQ ranged from once or twice (10%) to every day or almost every day (20%) with the majority of participants reporting pain or discomfort fairly often (50%). These data provide preliminary information about the nature and scope of pain in youth with SCI.