S. Kal

Stress and resistivity analysis of electrodeposited gold films for MEMS application

Electroplated gold films have attracted much attention in recent years because of its desirable properties for microsystems applications such as resistance to oxidation, low electrical resistance, overall chemical inertness and low processing temperature. In order to use gold in microelectromechanical systems designs, systematic tests has to be conducted to characterize the material in terms of its electrical as well as mechanical properties. In this paper, the stress and resistivity behavior of a nanometer-scale gold film with respect to the deposition parameters and annealing condition is reported.

lang1?0?0rang bar corner compensation for CMOS compatible anisotropic TMAH etching

For a long time wet bulk-micromachining has been an easy and cost-effective method for fabricating silicon micro-sensors. Anisotropic wet etching is the key processing step for the fabrication of microstructures. Among different silicon etchants, TMAH based etchants are becoming popular because of their low toxicity and CMOS compatibility. The etch rate of wet anisotropic etching of silicon depends on the crystal plane orientation, type of etchant and their concentrations. In anisotropic etching, convex corners are attacked; therefore, a proper compensating structure design is often required when fabricating microstructures with sharp corners (convex corners). In the present work, two 1 0 0 bar compensation structures have been used for convex corner compensation with 25% wt TMAH–water solution at 90 ± 1 °C temperature. Generalized empirical formulae are also presented for these compensation structures for TMAH–water solution. Both the 1 0 0 bar structures provide perfect convex corners but the 1 0 0 wide bar (structure 2) is more space efficient than the 1 0 0 thin bar (structure 1) and it requires nearly 30% less groove width.

FEM Based Design and Simulation of Bulk Micromachined MEMS Accelerometers with Low Cross Axis Sensitivity

This paper reports the design and simulation of two MEMS piezoresistive accelerometers for single axis low g (plusmn2g) automotive applications. Both the accelerometer structures consist of four beams at the top with eight embedded resistors as sensing elements to form Wheatstone bridge network and interconnected to minimize the cross axis sensitivity. FEM based design and simulation results for both the accelerometers are presented and compared, which are performed using commercially available MEMSCAD tool CoventorWarereg. Fabrication process and technological aspects to realize both the structures are discussed. The sensitivity of the two accelerometers is 6.5 mV/g and 5.85 mV/g respectively. Cross axis sensitivity of the structures is three orders lower than the prime axis sensitivity

Characterization of laser and laser/thermal annealed semiconducting iron silicide thin films

Abstractβ-FeSi2 is an important semiconducting silicide which is being studied extensively. In this paper, we report our results of the effect of laser and laser-thermal annealing on the properties of β-FeSi2. 5N purity Fe was deposited on Si substrate and was subsequently irradiated by CW and pulsed laser separately followed by thermal annealing to reduce the laser induced damage. The samples were then characterized by sheet resistance, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), optical reflectance and absorption studies. Lastly, β-FeSi2/n-Si heterojunctions were fabricated and the effect of laser treatment on the junction ideality factor was investigated. All these characterizations indicated the formation of good quality β-FeSi2, particularly after pulsed laser followed by thermal treatment.

Characterization of phase transformation in titanium polycide films

Silicide formation on polysilicon from deposited titanium films and effects of subsequent thermal annealing at different temperatures (C-C) have been investigated by grazing-angle XRD, AFM, ESCA and sheet resistance measurements. The results indicated formation of a high-resistivity isomorphic phase (C49), polymorphic phases (C49 and C54) and low-resistivity isomorphic C54 films at low, medium and high annealing temperatures from C to C. The complete conversion from C49 to isomorphic C54 phase occurs at about C. The influence of phase formations and polymorphic transformation on the surface morphology is studied by estimating the r.m.s. surface roughness using AFM. Samples annealed at C have the highest surface roughness of 15.47 nm owing to agglomeration of C54 grains in films. XPS studies showed the formation of a thin layer of on the surface of .

SrZn11: a new binary compound with the BaCd11 structure

Single crystals of strontium undecazinc, SrZn(11), were obtained when decomposing SrZn(2) under conditions of high pressure and high temperature. The new binary Sr-Zn compound crystallizes in the space group I4(1)/amd (BaCd(11) structure type) with one Sr position (\overline{4}m2) and three Zn sites (\overline{4}m2, .2/m., 1). The structure is described in terms of all-face-capped Zn(8) tetrahedra as the central building unit, defined by the Zn atoms on .2/m. and 1. The building units are condensed into chains by the central tetrahedra sharing edges, and the chains are interconnected by shared capping atoms. The resulting three-dimensional framework of Zn atoms yields channels that are occupied by Sr and Zn atoms on the high-symmetry \overline{4}m2 positions.

Current-voltage studies on β-FeSi2/Si heterojunction

I-V characteristics of both β-FeSi2/n-Si and β-FeSi2/p-Si were studied at room temperature. The junctions were formed by depositing Fe on Si selectively followed by thermal annealing and some samples were later treated by pulsed laser. Temperature of thermal annealing and diode area were also varied.I-V studies on all these samples were done and ideality factors were computed. Results obtained were interpreted.

Characterization of thin titanium silicide films prepared by PASET and a conventional process

An advanced silicide process featuring pre-amorphization before Ti film deposition and sequential two-step annealing (PASET) has been used to prepare thin titanium silicide films. Pre-amorphization by As implantation produces TiSi2 films with low and uniform sheet resistance. The TiSi2 film properties have been compared with those of a film prepared by a conventional two-step annealing technique. Non-destructive and non-contacting characterization techniques such as spectroscopic ellipsometry, atomic force microscopy and thermal wave analysis have been employed along with traditional tools (XRD, four-point probe, TEM) to characterize the TiSi2 films. Optical properties such as refractive indices (n,k) of the TiSi2 films are presented.

Characterization of titanium polycide films by atomic force microscope

Non-destructive methods are required for in-line process control in VLSI circuits. In this study, mean roughness values as obtained from AFM analysis have been used to follow phase transformation of Ti-polycide films formed by annealing Ti films on polysilicon. The results are supported from XRD analysis of the TiSi2 films.