No abstract

A novel and simple process for the exploitation of metal-gate-induced stress in the Si channel region of a FinFET is reported. TaN metal-gate electrode was employed. The use of a silicon nitride capping layer, which covered the metal gate during the source and drain anneal, led to a large stress being developed as a result of the thermal-expansion coefficient mismatch between the gate and the capping layer. The resulting strain was retained and transferred to the Si channel. The stress introduced by the gate stressor was found to enhance the performance of the n-channel FinFETs and is believed to be tensile in the sourceto-drain direction. This approach may be applicable to other metal-gate materials having a mismatch in the thermal-expansion coefficient with surrounding capping materials.

This work investigates the electronic band structures of bulk Ge 1-x Sn x alloys using the empirical pseudopotential method (EPM) for Sn composition x varying from 0 to 0.2. The adjustable form factors of EPM were tuned in order to reproduce the band features that agree well with the reported experimental data. Based on the adjusted pseudopotential form factors, the band structures of Ge 1-x Sn x alloys were calculated along high symmetry lines in the Brillouin zone. The effective masses at the band edges were extracted by using a parabolic line fit. The bowing parameters of hole and electron effective masses were then derived by fitting the effective mass at different Sn compositions by a quadratic polynomial. The hole and electron effective mass were examined for bulk Ge 1-x Sn x alloys along specific directions or orientations on various crystal planes. In addition, employing the effective-mass Hamiltonian for diamond semiconductor, band edge dispersion at the C-point calculated by 8-band k.p. method was fitted to that obtained from EPM approach. The Luttinger-like parameters were also derived for Ge 1-x Sn x alloys. They were obtained by adjusting the effective-mass parameters of k.p method to fit the k.p band structure to that of the EPM. These effective masses and derived Luttinger parameters are useful for the design of optical and electronic devices based on Ge 1-x Sn x alloys. V C 2012 American Institute of Physics.

We report the first realization of fully-released and relaxed Ge1-xSnx structures on Ge substrate. The coefficients of Raman peak shift a and b due to the alloy disorder and strain, respectively, were experimentally obtained for Ge1-xSnx. In addition, to lower the Sn composition needed to achieve direct bandgap Ge1-xSnx alloys and also to realize channel materials with higher electron mobility, uniaxially tensile strained Ge1-xSnx patterns were fabricated. Large tensile strain (>1%) was detected in the patterned Ge1-xSnx lines. Such tensile-strained Ge1-xSnx structures could enable the realization of Group-IV optoelectronic devices and high mobility n-channel transistors.

We explore several technology options for the enhancement of electron and hole mobility in complementary metal-oxide-semiconductor (CMOS) field-effect transistors, focusing on strain engineering using lattice-mismatched source/drain (S/D) materials. Silicon-carbon (Si 1−y C y ) and silicon-germanium (Si 1−x Ge x ) have lattice constants different from that of the Si channel. When Si 1−y C y or Si 1−x Ge x is embedded in the transistor S/D region, lateral tensile or compressive strain is induced in the adjacent Si channel, leading to improvement in the electron or hole mobility, respectively. The origin of the strain effect, process integration, device characteristics and strain enhancement approaches are discussed.