No abstract

Abstract-This work demonstrates a method for incorporating strain in silicon nanowire gate-all-around (GAA) n-MOSFETs by oxidation-induced bending of the nanowire channel and reports on the resulting improvement in device performance. The variation in strain measured during processing is discussed. The strain profile in silicon nanowires is evaluated by Raman spectroscopy both before device gate stack fabrication (tensile strains of up to 2.5% are measured) and by measurement through the polysilicon gate on completed electrically characterized devices. Drain current boosting in bended n-channels is investigated as a function of the transistor operation regime, and it is shown that the enhancement depends on the effective electrical field. The maximum observed electron mobility enhancement is on the order of 100% for a gate bias near the threshold voltage. Measurements of stress through the full gate stack and experimental device characteristics of the same transistor reveal a stress of 600 MPa and corresponding improvements of the normalized drain current, normalized transconductance, and low-field mobility by 34% (at maximum gate overdrive), 50% (at g max ), and 53%, respectively, compared with a reference nonstrained device at room temperature. Finally, it is found that, at low temperatures, the low-field mobility is much higher in bended devices, compared with nonbended devices.

a b s t r a c tIn this paper, we investigate the effect of different process parameters on oxidation-induced strain (OIS) into a doubly-clamped silicon nanowire FET to control and finally, enhance carrier mobility. Spacer technology together with sacrificial thermal oxidation were used to fabricate %100 nm wide Si NWs. The built-in tensile stress in the Si NWs was measured using micro-Raman spectroscopy and a maximum of 2.6 GPa was found.

Ternary alloys of composition close to Cr 2 AlC have been deposited by ion beam sputtering onto unheated and heated to 380 0 C Si substrates. As-deposited films have very small crystallites at around 7 nm. Annealing of the film in air at 700ºC leads to crystallite growth to 32.3 nm. Crystallisation also can be achieved by annealing in air but there is also partial oxidation of the film surface to the depth of approximately 120 nm, which represents an oxide layer less than 5% of the total film thickness. There is an increase of lattice size along the c-axis during crystallisation in air, which can indicate small incorporation of oxygen.Film structure and crystallisation have also been analysed by Raman spectroscopy. This is the first time that changes in Raman spectra in Cr 2 AlC have been correlated with crystallite size and it was observed that MAX-phase related peaks become sharper for bigger crystallites. It is well known that chromium containing materials have exceptional engineering properties. The materials excel in high temperature oxidation resistance and have been used as protective coatings for decades as can be seen in some early work and references therein [1,2]. A few decades ago Nowotny and co-workers achieved synthesis of a large class of ternary carbides and nitrides with quite unique properties such as lamination of atoms on the nanoscale [3,4]. The resurgence of work on those materials in the last decade is closely linked to Barsoum's early work [5] and the field has been highlighted again in the latest reviews [6][7][8][9]. The general formula of the nanolaminated materials in many cases can be presented as M n+1 AX n , where n=1, 2, or 3; M is a transition metal, A is an A-group element, and X is C or N. The name "MAX phases" for the crystalline arrangements was coined by Barsoum [6]. One significant property which unites all MAX phases is their nanolaminated structure. The majority of bulk MAX phases require high, in excess of 1200 0 C, temperatures for synthesis and synthesis of pure phases is nontrivial due to formation of competing binary compounds. The first synthesis by Physical Vapour Deposition (PVD) onto single-crystal substrates was reported in 2002 by Palmquist et al. [10]. Since then about 70 compounds have now been synthesised. [8,9].Retention of mechanical properties and high oxidation resistance of many MAX phases at high temperatures has made synthesis of thin film MAX phase materials an important research area. A major research challenge is to lower the formation temperature of MAX phases and to determine if the desired material properties can be achieved either as MAX phase or as material with MAX composition only. For the 211 phases Cr 2 AlC, V 2 AlC, Cr 2 GeC, and V 2 GeC it is possible to form fully-developed crystalline structures at around 500-700 0 C [11][12][13][14][15][16][17]. The Ti-containing 211 phases Ti 2 AlC and Ti 2 GeC, however, were grown at temperatures of order 700 °C [18,19] and only recently the Ti 3 SiC 2 was grown at 650 0 C on a non-epitaxial substra...

In this paper we investigate the mobility enhance-