Mohamed Boumerzoug

Electron cyclotron resonance chemical vapor deposition of silicon oxynitrides using tris(dimethylamino)silane

A new compound, tris(dimethylamino)silane was used as an organosilicon source for the deposition of silicon oxynitride thin films. The depositions were carried out at low substrate temperatures (<150 °C) in an electron cyclotron resonance plasma enhanced chemical vapor deposition reactor. Films with compositions varying from Si3N4 to SiO2 were deposited on silicon substrates by varying the N2/O2 flow ratio to the plasma chamber. In situ ellipsometry measurements of the film optical index were well correlated with film composition. Auger electron spectroscopy showed that only low levels of carbon (<3 at. %) were present, while Fourier transform infrared spectroscopy showed low levels of bonded hydrogen. The deposition rate of high quality Si3N4 was as high as 220 A/min.A new compound, tris(dimethylamino)silane was used as an organosilicon source for the deposition of silicon oxynitride thin films. The depositions were carried out at low substrate temperatures (<150 °C) in an electron cyclotron resonance plasma enhanced chemical vapor deposition reactor. Films with compositions varying from Si3N4 to SiO2 were deposited on silicon substrates by varying the N2/O2 flow ratio to the plasma chamber. In situ ellipsometry measurements of the film optical index were well correlated with film composition. Auger electron spectroscopy showed that only low levels of carbon (<3 at. %) were present, while Fourier transform infrared spectroscopy showed low levels of bonded hydrogen. The deposition rate of high quality Si3N4 was as high as 220 A/min.

Room temperature electron cyclotron resonance chemical vapor deposition of high quality TiN

High quality, gold‐colored TiN was deposited at room temperature by decomposing TiCl4 in the downstream of an N2/H2 electron cyclotron resonance (ECR) plasma. The morphology of the as‐deposited films was investigated by scanning electron microscopy, and the resistivity was measured using the four point probe technique. The films were uniform over 2 in. wafers, with resistivities of 100–150 μΩ cm. Auger electron spectroscopy was used for the determination of the Ti/N ratio and for the detection of contaminants, and shows that the as‐deposited films were stoichiometric and chlorine free. The present results represent a major improvement in lowering the deposition temperature of TiN using ECR plasma‐enhanced chemical vapor deposition with TiCl4 as reactant.

LOW-TEMPERATURE ELECTRON CYCLOTRON RESONANCE CHEMICAL VAPOR DEPOSITION OF VERY LOW RESISTIVITY TIN FOR INP METALLIZATION USING METALORGANIC PRECURSORS

Titanium nitride (TiN) thin films were deposited onto Si and InP using the electron cyclotron resonance chemical vapor deposition technique. Tetrakis(dimethylamido)titanium (TDMATi) was used as a precursor. Depositions onto unheated substrates were carried out downstream of a nitrogen plasma. Stoichiometric (Ti:N≊1) and very low resistivity (43 μΩ cm) films were obtained at a deposition rate of 13 A/min. The carbon and oxygen contaminants in the films were below the detectability limits of Rutherford backscattering and Auger electron spectroscopy. The Auger depth profile shows that the TiN/InP structure is stable for rapid thermal annealing up to 800 °C.

In-situ monitoring of electron cyclotron resonance plasma chemical vapour deposition of hydrogenated silicon nitride films

Abstract Hydrogenated silicon nitride (SiN:H) films were deposited by electron cyclotron resonance plasma chemical vapour deposition on Si and InP substrates. A non-corrosive organic compound, liquid at room temperature and stable in air, CONSI™ 4000 (SiH 2 (C 4H 9 ) 2 ), was used as the precursor for the silicon. Depositions were successfully made at relatively low substrate temperatures, below 300°C. The effects of the processing conditions on the plasma characteristics and film properties were investigated. The emission intensities from excited species in the plasma were monitored by optical emission spectroscopy. The corresponding electron temperature and the plasma density were determined by analysing the current-voltage characteristics of a Langmuir probe. The resulting film composition was determined by Auger electron spectroscopy. The combined in-situ methods facilitate optimization of the deposition conditions, eventually leading to stoichiometric films (Si-to-N ratio, about 0.75) with less than 2 at. % of incorporated carbon.

OPTICAL EMISSION SPECTROSCOPY AS A REAL TIME DIAGNOSTIC TOOL FOR PLASMA-ASSISTED DEPOSITION OF TIN

Real-time optical emission spectroscopy (OES) was used to monitor the deposition of TiN both from mixtures of tetrakis(dimethylamino)titanium (TDMATi)-N2 and TiCl4-H2-N2 in an electron cyclotron resonance chemical vapor deposition system. The accurate control of the ratio of the emission intensities of ionized nitrogen at 391.4 nm and molecular nitrogen at 357.7 nm (N2+/N2) led to low temperature deposition of stoichiometric TiN (Ti/N ≈ 1) and very low resistivity in both cases. It was found that high ion density plasmas are crucial for a considerable reduction of the deposition temperature while maintaining good film quality. OES shows that the abundance of certain excited plasma species is not only dependent on the gas mixture and the deposition parameters, such as total pressure and microwave power, but also is strongly affected by the magnetic field configuration. The deposition rate and the film resistivity can be related to the emission intensity ratio, I(N2+)/I(N2). Finally, the two processes are compared in terms of the quality of as-deposited and heat-treated films. The comparison shows that the films obtained with TDMATi exhibit lower resistivity and are thermally more stable than with TiCl4.

COMPLETE SOLVENT FREE STRIPPING OF VIA STRUCTURES USING NF3/H2O/O2 ASHING CHEMISTRY

The objective of this study is to develop a via post-strip cleaning process which would utilize non-hydroxylamine (HDA) based solvent, thereby reducing possibility of corrosion in the via and also reducing the cost of chemicals and waste disposal expenses. The work resulted in the development of a 100% solvent-less process which matches the performance of HDA-based solvents but totally eliminates chemical costs and waste-disposal expenses; removes the hazards of working with hot hazardous solvents; avoids corrosion which is common with HDA-based solvents; and thereby facilitates more efficient utilization of costly clean-room space. The new ash process in combination with a post-ash DI water rinse has been demonstrated to be effective at removing polymer inside vias and achieving via resistances comparable to standard oxygen ash + HDA wet solvent stripping.

Passivation Studies on AlGaAs Surfaces Suitable for High Power Laser Development

We report on the optical characterization of sulphur (S) passivated Al x Ga 1−x As/GaAs surfaces using photoluminescence (PL) and surface photovoltage (SPV) measurements. Both techniques show an enhancement in the near bandgap signal intensity, implying a reduction of the non-radiative recombination rate at the surface. To counter the instability of S-passivation, due to re-oxidation, dielectric layers of silicon nitride were deposited using electron cyclotron resonance plasma enhanced chemical vapour deposition (ECR-PECVD); the deposition of dielectric layers up to lOOnm thick does not appear to cause significant deterioration or stress at the insulator/AlGaAs interface. The dielectric layers are shown to be resistant to oxidation, and effective in maintaining the passivation effect over a period of weeks.

Optical characterization of passivation for high-power AlxGa1-xAs-based lasers

We report on passivation of AlxGa1-xAs/GaAs surfaces using different sulfur and chlorine based treatments: These include ammonium sulfide solution, arsenic sulfide vapor and hydrochloric acid treatments. Enhancements in the intensity of near band-gap photoluminescence (PL) peaks, coupled with peak half-width reduction on treatment were attributed to a reduction in the density of surface states. Pre-etching using sulfuric acid- and ammonium hydroxide-based solutions prior to sulfur passivation was also found to contribute significantly to the overall success of a passivation treatment. The best sulfur-passivation results for all x (0 < x < 0.38) were found when sulfuric acid-peroxide-deionized water (Caros) solution pre-etching was followed by ammonium sulfide solution treatment at 65 degree(s)C for 25 min.

Thermal Stability of Reactively Sputtered TiN on InP as a Diffusion Barrier

The stability of rcactively sputtered TiN films on InP for application as a diffusion barrier has been examined using electrical measurements, Auger profiling and scanning electron microscopy (SEM). The samples were subjected to rapid-thermal-annealing (RTA) in a N 2 atmosphere at temperatures between 400°C and 900°C. The SEM pictures of “as deposited” and RTA stoichiometric films show that the morphology is smooth, fine-grained and stable until 800°C. Auger depth profiling shows little interdiffusion between TiN and InP for RTA below 800°C. Annealing at temperatures of about 700°C reduces the sheet resistance of TiN relative to the “as-deposited” films by about 50%. Annealing at temperatures above 800°C results in a large sheet resistance. This may be associated with the deterioration of the TiN/InP morphology at high anneal temperatures as observed by SEM.

Residue removal after via-hole etching

Using a combined microwave downstream plasma and low damage RIE, we have successfully developed a dry process that removes both the photoresist and the remaining polymer residue after a via etch step. An ion assisted plasma process containing oxygen and fluorine was successfully developed. It was found that the ion-assisted process converted the Ti, Si and their oxide containing residues to water-soluble compounds. Thus, a room temperature DI water rinse after the dry process removed the entire sidewall residue. The process is carried out at room temperature to avoid any undercutting of the TiN layer. SEM micrographs show that the via sidewall is free of any residue. The electrical data shows via resistance equal to or lower than samples cleaned with the standard process using oxygen plasma followed by a solvent clean. This process has been shown to be a reliable and cost-effective alternative to solvent based processing. Failure due to the narrow window of the solvent process is eliminated and equivalent or improved yield and device performance is obtained with the new process.