Effects of patterning induced stress relaxation in strained SOI/SiGe layers and substrate

Abstract

Local stress fields in strained silicon structures important for CMOS technology are essentially related to size effects and properties of involved materials. In the present investigation, Raman spectroscopy was utilized to analyze the stress distribution within strained silicon (sSi) and silicon-germanium (SiGe) island structures. As a result of the structuring of initially unpatterned strained films, a size-dependent relaxation of the intrinsic film stresses was obtained in agreement with model calculations. This changed stress state in the features also results in the appearance of opposing stresses in the substrate underneath the islands. Even for strained island structures on top of silicon-on-insulator (SOI) wafers, corresponding stresses in the silicon substrate underneath the oxide were detected. Within structures, the stress relaxation is more pronounced for islands on SOI substrates as compared to those on bulk silicon substrates

Comparative Study of Far-Field and Near-Field Raman Spectra from Silicon-Based Samples and Biological Nanostructures

“…32À34 Figure 2b shows the Raman spectrum acquired from a sample with a 70 nm thick tensile strained (001)Si layer bonded onto a SiO 2 film on a crystalline Si substrate. 35 The SiÀSi phonon band of the strained Si layer is shifted by about 5.0 cm À1 to lower wavenumbers relative to its strain-free reference position indicated by the Si substrate peak at 520.1 cm À1 . Because of the crystalline lattice structure of the strained layer and substrate, the width of both SiÀSi bands is nearly identical as shown in Figure 2b by fitting the spectrum with two Lorentz functions (red and blue curves in Figure 2b).…”

“…For example, by applying strain to the Si crystal, the distance between neighboring atoms is slightly modified, thus also influencing the local environment within the sample. Depending on the applied strain, the spectral position of the Si–Si band can be shifted by several wavenumbers to lower or higher values for tensile or compressive strain, respectively. − Figure b shows the Raman spectrum acquired from a sample with a 70 nm thick tensile strained (001)Si layer bonded onto a SiO 2 film on a crystalline Si substrate . The Si–Si phonon band of the strained Si layer is shifted by about 5.0 cm –1 to lower wavenumbers relative to its strain-free reference position indicated by the Si substrate peak at 520.1 cm –1 .…”

Characterization of semiconductor materials using synchrotron radiation-based near-field infrared microscopy and nano-FTIR spectroscopy

“…Upon deconvolution the broad peak can be fitted by three symmetric Gaussian bands at 849 cm −1 , 912 cm −1 , and 961 cm −1 , which represent absorption states of the Si-N stretching mode [52][53][54]. Small band shifts in IR and Raman spectra can also be explained by the influence of stress as has been reported for SiC [34,47] and other Si-based [55,56] sample systems. Fig.…”

Room-temperature direct band-gap electroluminescence from germanium (111)-fin light-emitting diodes

“…One possible approach to reduce compressive stress is stress relaxation by applying a three-dimensional (3D) structure because strain tends to relax at the edge part of a strained layer. 28,29) We previously demonstrated 3D Ge fin lightemitting diodes (LEDs) with 50-nm-high Ge fins fabricated by dry etching and Ge condensation of SiGe layers grown on Si(100) fins. 26) Although larger light emission and optical confinement with higher fin height is needed to achieve lasing operation, fabrication of higher fins by the combined processes of dry etching and Ge condensation is difficult because sufficient flatness and uniformity of the SiGe layers and Si fins is difficult to obtain due to the non-uniformity of dry etching and small margin of the Ge condensation process.…”