The development of titanium silicide - boron doped polysilicon resistive temperature sensors

Thin films of titanium silicide $(TiSi_2$) formed on heavily boron-doped polycrystalline silicon $(poly-Si/B^+)$ were applied for the first time for resistive temperature sensing. The temperature sensors exhibited a high-temperature coefficient of resistance of 3.8 x 10^{-3}^{\circ}\mathrm{C}^{-1}, a linear dependence of resistance on temperature and an excellent thermal and electrical stability up to 800 $^{\circ}\mathrm{C}$. This work discusses the fabrication method and the morphological and electrical characterization of the $TiSi_2/poly-Si$ thin film resistors throughout the stages of its formation

Electrical characterization of Thin-Film structures with redeposited sidewall

Accurate electrical characterization of test structures and devices requires identification and correction for parasitic current paths in the measurement network. The sidewalls formed during reactive ion etching of thin-film phase-change material layers in argon plasma can result in parasitic current paths in the structures. In this paper, thin-film structures with redeposited sidewalls are realized, and they are experimentally characterized by electrical resistance measurements on van der Pauw test structures. The impact of conducting sidewalls on contact resistance measurements and data extraction from cross-bridge Kelvin resistor structures is discussed. The error introduced in the electrical resistance measurements from these test structures is analytically modeled. The impact on the electrical performance of devices due to the formation of sidewalls is also discussed

Cross-bidge Kelvin resistor (CBKR) structures for measurement of low contact resistances

A convenient test structure for measurement of the specific contact resistance (ρc) of metal-semiconductor junctions is the CBKR structure. During last few decades the parasitic factors which may strongly affect the measurements accuracy for ρc < 10-6 Ω • cm2 have been sufficiently discussed and the minimum of the ρc to be measured using CBKR structures was estimated. We fabricated a set of CBKR structures with different geometries to confirm this limit experimentally. These structures were manufactured for metal-to-metal contacts. It was found that the extracted CBKR values were determined by dimensions of the two-metal stack in the contact area and sheet resistances of the metals used. \ud Index Terms—Contact resistance, cross-bridge Kelvin resistor (CBKR), sheet resistance, test structures, metal, silico

Characterisation of Ta-based barrier films on SiLK for Cu-metalisation

Structures with Ta, TaxN1-x, Ta90C10, Ta95Si5 on SiLK were tested using in-situ 4- point probe resistance measurements during annealing up to 400oC. The change in normalized resistance by a factor of up to 2.58 was attributed to oxygen diffusion out of SiLK layer into the barriers. No direct chemical reaction between hydrocarbons from the SiLK and the barriers was observed. The concentration coefficient of resistivity for O in Ta was calculated to be 6.7μΩ*cm/at % for pure Ta and 2.65 μΩ*cm/at % in TaxN1-x with x=0.90-0.9

Novel test structures for temperature budget determination during wafer processing

Temperature is a crucial parameter in many planar technology processing steps. However, the determination of the actual temperature history at the device side of the substrate is not straightforward. We present a novel method for determining the temperature history of the process side of silicon wafers and chips, which is based on well-known silicide formation reactions of metal-Si systems and is determined via (4 point probe) resistance measurements. In this case we explored the Pd-Si system which has a suitable operating range from 100-200°C. We propose a method based on metal layers patterned in different line configurations (using the width and number of the lines as parameters) and anticipate that silicide developments at these structures is geometrically dependent and hence can provide a way for obtaining a refined temperature information. First experiments on bulk Si wafers show that the proposed method yields predictable and stable results

Electrical properties of plasma-deposited silicon oxide clarified by chemical modeling

Our study is focused on Plasma Enhanced Chemical Vapor Deposition (PECVD) of silicon dioxide films at low temperatures (< 150 oC) using Inductively Coupled (IC) High-Density (HD) plasma source. We recently fabricated Thin Film Transistors (TFTs) with high-quality ICPECVD gate oxides, which exhibited a competitive performance. For better understanding of the influence of deposition parameters on both the deposition kinetics and oxide quality, we have modeled the Ar-SiH4-N2O plasma system with 173 chemical reactions. We simulated concentrations of 43 reactive species (such as e.g. SiHx radicals and SiHx + (x=0-3) ions, polysilanes, SiO, SiN, SiH3O, SiH2O, HSiO, etc., as well as atomic hydrogen, nitrogen and oxygen) in plasma. We further used our simulations to qualitatively explain (in terms of concentrations of the reactive species) the influence of SiH4/N2O gas-flow ratio and total gas pressure on film electrical properties and deposition rate

Effects of Oxygen, Nitrogen and Fluorine on the Crystallinity of Tungsten by Hot-Wire Assisted ALD

A heated tungsten filament (wire) is well known to generate atomic hydrogen (at-H) by catalytically cracking molecular hydrogen (H2) upon contact. This mechanism is employed in our work on hot-wire (HW) assisted atomic layer deposition (HWALD), a novel energy-enhancement technique. HWALD has been successfully utilized to deposit tungsten (W) films using alternating pulses of WF6 and at-H. Depending on the conditions, either low-resistivity α- or higher-resistivity β-crystalline phases of W can be obtained. This work aims to clarify (i) which factors are decisive for the formed crystal phase and (ii) the role of the residual gases in the film growth mechanism. In this light, the effects of adding impurities (N2O, O2, NH3 and H2O) were investigated. Oxidizing species have a retarding effect on W growth but the process can be re-initiated after stopping their supply. In contrast, nitridizing species have a permanent inhibition effect. Further, the effects of WF6 overdose were studied. The surplus of WF6 appeared to be crucial for the process: in many cases this led to the formation of β-phase W instead of the α-phase, with a memory effect lasting for several deposition runs. Extra fluorine-containing species were thus identified as the likely cause of β-phase formation

Atomic layer deposition of W_1.5N barrier films for Cu Metallization

An atomic layer deposition process to grow tungsten nitride films was established at 350 degrees C with a pulse sequence of WF6/NH3/C2H4/SiH4/NH3. The film composition was determined with Rutherford backscattering as W1.5N, being a mixture of WN and W2N phases. The growth rate was similar to 1 x 10(15) W atom/cm(2) per cycle (monolayer of W2N or WN). The films with a thickness of 16 nm showed root-mean-square roughness as low as 0.43-0.76 nm. The resistivity of the films was stable after 50 cycles at a value of 480 mu Omega cm. Results of four-point probe sheet resistance measurements at elevated temperature demonstrated that our films are nonreactive with Cu at least up to 500 degrees C. Results of I-V measurements of p(+)/n diodes before and after heat-treatment in (N-2 + 5% H-2) ambient at 400 degrees C for 30 min confirmed excellent diffusion barrier properties of the films. (c) 2005 The Electrochemical Society. All rights reserved

Doped SbTe phase change material in memory cells

Phase Change Random Access Memory (PCRAM) is investigated as replacement for Flash. The memory concept is based on switching a chalcogenide from the crystalline (low ohmic) to the amorphous (high ohmic) state and vice versa. Basically two memory cell concepts exist: the Ovonic Unified Memory (OUM) and the line cell. Switching to the high ohmic or low ohmic state is done using Joule heating. A relatively short (~ns) electrical pulse with large amplitude is used to heat the crystalline phase to melt and quench into the amorphous state (RESET). A pulse with smaller amplitude heats the amorphous region above its crystallization temperature (lower than the melting temperature) and the material returns into the crystalline state (SET). In the OUM cell this will be at the electrode-phase change material contact, whereas for the line cell this will be at the position where the current density is the highest

Hot-Wire Assisted ALD: A Study Powered by In Situ Spectroscopic Ellipsometry

Hot-wire assisted atomic layer deposition (HWALD) is a novel energy-enhancement technique. HWALD enables formation of reactive species (radicals) at low substrate temperatures, without the generation of energetic ions and UV photons as by plasma. This approach employs a hot wire (tungsten filament) that is heated up to a temperature in the range of 1300–2000 °C to dissociate precursor molecules. HWALD has the potential to overcome certain limitations of plasma-assisted processes. This work investigates the ability of a heated tungsten filament to catalytically crack molecular hydrogen or ammonia into atomic hydrogen and nitrogen-containing radicals. The generation of these radicals and their successful delivery to the wafer (substrate) surface are experimentally confirmed by dedicated tellurium-etching and silicon-nitridation experiments. It further reports on deposition of low-resistivity oxygen-free tungsten films by using HWALD, as well as on the effect of hot-wire-generated nitrogen radicals and atomic hydrogen in deposition of aluminum nitride and boron nitride films. In parallel, this work provides important illustrative examples of using in situ real-time monitoring of deposition and etching processes, together with extracting a variety of film properties, by spectroscopic ellipsometry technique