Plasma-enhanced Chemical Vapor Deposition Silicon Research Articles

Large-Signal Performance of Deep Submicrometer AlGaN/AlN/GaN HEMTs With a Field-Modulating Plate

This is the first time that the microwave performance of a 0.1-/spl mu/m gate in a silicon nitride window opening, with a field-modulating plate on an AlGaN/AlN/GaN heterojunction structure, is reported. The material structure was grown by organometallic vapor phase epitaxy on SiC substrates with an averaged channel sheet resistance of 313.5 ohms/square. Approximately 80-nm-thick plasma-enhanced chemical vapor deposition silicon nitride is used as the dielectric between gate metal extension and semiconductor surface. Transistors of a total gate width of 250 /spl mu/m and a 0.1 /spl mu/m gate footprint, with a 0.36 /spl mu/m long overhang on top of the silicon nitride, can be operated at a drain bias of 40-V high. Output power density of 9.5 W/mm, with 36% power-added efficiency in class AB regime, was demonstrated at 10 GHz in a continuous wave power measurement.

Determination of mechanical properties of PECVD silicon nitride thin films for tunable MEMS Fabry–Pérot optical filters

This paper reports an investigation on techniques for determining elastic modulus and intrinsic stress gradient in plasma-enhanced chemical vapor deposition (PECVD) silicon nitride thin films. The elastic property of the silicon nitride thin films was determined using the nanoindentation method on silicon nitride/silicon bilayer systems. A simple empirical formula was developed to deconvolute the film elastic modulus. The intrinsic stress gradient in the films was determined by using micrometric cantilever beams, cross-membrane structures and mechanical simulation. The deflections of the silicon nitride thin film cantilever beams and cross-membranes caused by in-thickness stress gradients were measured using optical interference microscopy. Finite-element beam models were built to compute the deflection induced by the stress gradient. Matching the deflection computed under a given gradient with that measured experimentally on fabricated samples allows the stress gradient of the PECVD silicon nitride thin films introduced from the fabrication process to be evaluated.

Degradation of Gate Oxide Reliability due to Plasma-Deposited Silicon Nitride

The effects of plasma-enhanced chemical vapor deposition (PE-CVD) silicon nitride (p-SiN) passivation films on time dependent dielectric breakdown (TDDB) of gate oxide were studied. It was found that degradation of TDDB characteristics with p-SiN films was suppressed by the change in p-SiN deposition conditions. The correlation between trapped electron density and TDDB characteristics varied, depending on the p-SiN films. The degradation of TDDB characteristics was also enhanced with phosphosilicate glass (PSG) under the p-SiN passivation film.

Fabrication of a glass-implemented microcapillary electrophoresis device with integrated contactless conductivity detection.

Glass microdevices for capillary electrophoresis (CE) gained a lot of interest in the development of micrototal analysis systems (microTAS). The fabrication of a microTAS requires integration of sampling, chemical separation and detection systems into a microdevice. The integration of a detection system into a microchannel, however, is hampered by the lack of suitable microfabrication technology. Here, a microfabrication method for integration of insulated microelectrodes inside a leakage-free microchannel in glass is presented. A combination of newly developed technological approaches, such as low-temperature glass-to-glass anodic bonding, channel etching, fabrication of buried metal interconnects, and deposition of thin plasma-enhanced chemical vapour deposition (PECVD) silicon carbide layers, enables the fabrication of a CE microdevice with an integrated contactless conductivity detector. The fabrication method of this CE microdevice with integrated contactless conductivity detector is described in detail. Standard CE separations of three inorganic cations in concentrations down to 5 microM show the viability of the new microCE system.

Stable gallium arsenide MIS capacitors and MIS field effect transistors by (NH/sub 4/)/sub 2/S/sub x/ treatment and hydrogenation using plasma deposited silicon nitride gate insulator

The beneficial effects of sulfur passivation of gallium arsenide (GaAs) surface by (NH/sub 4/)/sub 2/S/sub x/ chemical treatment and by hydrogenation of the insulator-GaAs interface using the plasma-enhanced chemical vapor-deposited (PECVD) silicon nitride gate dielectric film as the source of hydrogen are illustrated by fabricating Al/PECVD silicon nitride/n-GaAs MIS capacitors and metal insulator semiconductor field effect transistors (MISFET). Post metallization annealing (PMA) at temperatures in the range 450-550/spl deg/C is shown to be the key process for achieving midgap interface state density below 10/sup 11//cm/sup 2//eV and maximum incremental transconductance, which is about 75% of the theoretical maximum limit. MIS capacitors are fabricated on (NH/sub 4/)/sub 2/S/sub x/ treated GaAs substrate using gate dielectrics such as PECVD SiO/sub 2/ and silicon oxynitride to demonstrate that the PMA is less effective with these dielectrics because of their lower hydrogen content. The small signal AC transconductance, g/sub ms/ measurements on MISFETs fabricated using silicon nitride, have shown that the low-frequency degradation of g/sub ms/ is almost absent in the devices fabricated on (NH/sub 4/)/sub 2/S/sub x/-treated GaAs substrates and subjected to PMA. The drain current stability in these devices is demonstrated to be excellent, with an initial drift of only 2% of the starting value. The dual role of silicon nitride layer, namely, protection against loss of sulfur and an excellent source of hydrogen for additional surface passivation along with sulfur is demonstrated by comparing the transconductance of MISFETs fabricated on GaAs substrates annealed without the nitride cap after the (NH/sub 4/)/sub 2/S/sub x/ treatment.

Combined effect of (NH4)2Sx treatment and post-metallization annealing with plasma-enhanced chemical vapour deposition silicon nitride gate dielectric on the GaAs metal-insulator-semiconductor characteristics and the photoluminescence characteristics of GaAs substrates

In this paper we present a GaAs surface passivation technique using (NH4)2Sx treatment and plasma-enhanced chemical vapour deposition silicon nitride. The passivation effects are demonstrated by the improvement in the capacitance–voltage (C–V) and the photoluminescence (PL) data. Post-metallization annealing (PMA) at 450 °C is required to obtain a good 1 MHz C–V curve and high band-edge PL intensities. Even though higher-temperature PMA shows better values of C–V and lower interface state density (Dit), it reduces the band-edge PL intensities. This is attributed to the hydrogen incorporation into GaAs during higher-temperature annealing cycles.

A comparative study on inductively-coupled plasma high-density plasma, plasma-enhanced, and low pressure chemical vapor deposition silicon nitride films

Silicon nitride films have been deposited using inductively-coupled plasma high-density plasma chemical vapor deposition (HDP CVD), plasma-enhanced chemical vapor deposition (PECVD), and low pressure chemical vapor deposition (LPCVD) methods. Characterization and comparison of the three films were performed using Fourier-transform infrared spectroscopy, secondary-ion mass spectroscopy, Rutherford backscattering spectrometry, and hydrogen forward-scattering spectrometry, in addition to wet-etch rate and stress measurement studies. It was found that silicon nitride films deposited using HDP CVD method have several advantages over the silicon nitride films that were deposited using the LPCVD and PECVD methods. The HDP CVD silicon nitride film can be deposited at much lower temperatures (⩽400 °C) than LPCVD silicon nitride, and has substantially less hydrogen (5.5 at. %) than the PECVD film. In addition, the PECVD film contains some oxygen in the film. The wet-etch rate of HDP CVD silicon nitride film is comparable to that of LPCVD film and is significantly less than that of PECVD film in both hot phosphoric acid and buffered HF solutions. The stress of the HDP CVD film is similarly compressive to the PECVD silicon nitride, and not as highly tensile as that of LPCVD silicon nitride.

Decrease in Deposition Rate and Improvement of Step Coverage by CF4 Addition to Plasma-Enhanced Chemical Vapor Deposition of Silicon Oxide Films

The low dielectric constant of F-doped silicon dioxide film makes it suitable for use as an intermetal film to improve the performance of ultra-large scale integrated circuits (ULSIs). One of the properties required by an intermetal film is good gap filling. It is known that fluorine addition to silicon oxide decreases the film deposition rate and improves the step coverage. In order to investigate these phenomena, we study the reaction mechanism of plasma-enhanced chemical vapor deposition (PECVD) silicon oxide film and its change by fluorine addition. Using a two film-forming species model, we explain the dependence of the deposition rate and the step coverage on the residence time for a SiH4/N2O-based PECVD system. The precursor produced by the dissociation of SiH4 has a relatively high sticking probability (≈0.5), while an intermediate species has a low (<10-4) sticking probability. The concentration of each species for deposition is changed by the residence time of the gas, thus the deposition rate and the step coverage show dependence on the residence time. The deposition rate of silicon oxide films is decreased and the step coverage is improved by CF4 addition during SiH4/N2O-based PECVD. From the estimation of the sticking probability, we suggest that the reason for the improvement of the step coverage by fluorine addition is not the etching effect by CF4 addition, but the decrease in sticking probability of the precursor produced by the dissociation of SiH4.

Analysis of silicon oxynitrides with spectroscopic ellipsometry and Auger spectroscopy, compared to analyses by Rutherford backscattering spectrometry and Fourier transform infrared spectroscopy

This work addresses the issues of whether spectroscopic ellipsometry, using the effective medium approximation (SE-EMA), may be used meaningfully to analyze plasma-enhanced chemical vapor deposition silicon nitride films. We use Rutherford backscattering spectrometry and Fourier transform infrared spectroscopy as reference methods and compare the results to the results of SE-EMA analyses and Auger analyses. The results are that Auger analysis, using properly determined sensitivity factors, gives compositions which are within the uncertainty of the reference methods. SE-EMA, on the other hand, always overestimates the oxide contribution and underestimates the nitride contribution. Probable causes are discussed.

Application of development-free vapor photolithography in silicon nitride etching

A new dry etching technique—development-free vapor photolithography—was used to transfer a pattern onto silicon nitride film. Plasma-enhanced chemical vapor deposition silicon nitride film and thin low pressure chemical vapor deposition silicon nitride film can be etched to get a positive pattern. The difference in the etching rate between exposed and unexposed areas was attributed to the difference in the concentration of accelerators that was controlled through a photochemical reaction. The reaction mechanism and other phenomena are discussed.

Strongly buckled square micromachined membranes

The buckling of compressively prestressed square membranes with built-in edges is investigated experimentally and analyzed theoretically. The buckling depends weakly on Poisson's ratio and essentially is a function of the reduced prestrain, /spl epsi/~/sub 0/=/spl epsi//sub 0/a/sup 2//h/sup 2/, where /spl epsi//sub 0/ is the physical prestrain, a is the width, and h is the thickness of the membrane. As /spl epsi/~/sub 0/ becomes increasingly negative, the membrane undergoes two symmetry breaking buckling transitions. Beyond the first transition occurring at /spl epsi/~/sub cr1/, the buckling profile has all the reflection and rotation symmetries of a square. The reflection symmetries are lost through a second instability transition at /spl epsi/~/sub cr2/. The bifurcation points, /spl epsi/~/sub cr1/ and /spl epsi/~/sub cr2/, and buckling profiles were calculated using analytical energy minimization and nonlinear finite-element simulation. Both methods agree. The buckling of micromachined plasma-enhanced chemical vapor deposition silicon nitride membranes on a silicon wafer is interpreted in terms of the theoretical results. Good matching between measured and calculated buckling profiles is found. The extracted strain values are consistent irrespective of the size and buckling mode of the membranes. From the average strain across the wafer /spl epsi//sub 0/=-3.50/spl times/10/sup -4/ and complementary wafer curvature measurements, a Young's modulus of 130 GPa is deduced. Methods for the straightforward extraction of /spl epsi//sub 0/ from experimental center deflections of buckled square membranes are described.

Investigation of the properties of plasma-enhanced chemical vapor deposited silicon nitride and its effect on silicon surface passivation

Silicon nitride films grown by plasma-enhanced chemical vapor deposition (PECVD) are used for a variety of applications in integrated circuit and solar cell industries, such as surface passivation and insulation. The objective of this article is to investigate and understand the impact of the PECVD deposition parameters on the silicon surface passivation and establish the correlation between the properties of the silicon nitride and the ensuing silicon surface recombination velocity. All the films were annealed at 350 °C for 20 min in a rapid thermal annealer after the deposition. It is shown that bonded hydrogen and positive charge in the annealed PECVD silicon nitride films have the opposite effect on the surface passivation. The surface recombination velocity decreases with the increase in the positive charge density and the decrease in the bonded hydrogen content. It is found that the deposition temperature has the most influence on achieving low surface recombination velocity. Higher deposition temperature in the range of 200–300 °C produces lower surface recombination velocity. Optimal silicon nitride deposition conditions resulted in a surface recombination velocity of 119 cm/s on 2 Ω cm p-type silicon.

Optimization and characterization of remote plasma-enhanced chemical vapor deposition silicon nitride for the passivation of p-type crystalline silicon surfaces

In a recent letter [Lauinger et al., Appl. Phys. Lett. 68, 1232 (1996)] we have shown that record low effective surface recombination velocities Seff of 4 cm/s have been obtained at ISFH on low-resistivity (1 Ω cm) p-type crystalline silicon using microwave-excited remote plasma-enhanced chemical vapor deposition (RPECVD) of silicon nitride at low temperature (300–400 °C). As an important application, this technique allows a simple fabrication of rear-passivated high-efficiency silicon solar cells with monofacial or bifacial sensitivity. In this work, we present details of the required optimization of the PECVD parameters and a characterization of the resulting silicon nitride films. All deposition parameters are shown to strongly affect Seff as well as the stability of the films against the ultraviolet (UV) photons of terrestrial sunlight. A clear correlation between Seff and the film stoichiometry is observed, allowing a simple control and even a rough optimization of the surface passivation quality by measurements of the refractive index of the films. An optimum passivation and UV stability is obtained for silicon-rich silicon nitride films with a refractive index greater than 2.3.

Effect of Fluorine Addition to Plasma-Enhanced Chemical Vapor Deposition Silicon Oxide Film

AbstractOne solution to reduce the time constant of ultra large scale integrated circuit (ULSI) is the use of a low dielectric constant intermetal film like fluorinated silicon oxide (SiOF). We could obtain SiOF films with low dielectric constant as low as 2.6 and good step coverage by adding CF4 to SiH4 and N2O in plasma-enhanced chemical vapor deposition (PECVD) process. To investigate the dielectric constants due to each polarization and the reason for the decrease in the dielectric constant, we used capacitance-voltage (C-V) and ellipsometry measurements, and Kramers-Kronig transformation. The decrease in dielectric constant could not be completely explained by the reduction in ionic and electronic polarization. We could detect silanol groups, Si-OH in the films and their decrease with increasing CF4 flow rate. It is suggested that the main polarization component to decrease dielectric constant is such as orientational polarization. The step coverage of film was improved by adding CF4. It is suggested that the reduction in the sticking probability of films forming species due to the change in surface state improved the step coverage.

Structural identification of point defects in amorphous silicon oxynitrides

The nature and the behaviour of point defects in amorphous hydrogenated silicon oxynitrides SiO x N y H z are reviewed and compared to that in plasma-enhanced chemical vapour deposition silicon dioxide and silicon nitrides. These defects are studied by electron spin resonance measurements after the ESR signal amplitude saturation by VUV illumination. The influences of the chemical composition (atomic ratio O O + N in the SiO x N y H z ) and of the hydrogen density on the type and density of defects are investigated. This is achieved by working on usual silicon oxynitrides containing high hydrogen densities (HHD) and on a new family of materials, the low hydrogen densities (LHD) silicon oxynitrides. Two defects are found in LHD silicon oxynitrides, the silicon dangling bond (Si db) and a new type of nitrogen related defect, the N x defect. By contrast, three defects are found in the usual HHD silicon oxynitrides, the Si db, the nitrogen dangling bond (N b) and the N x defect. The N x defect is described by an axially symmetrical paramagnetic centre with g ‖ = 2.0030, g ⊥ = 2.0017, A iso = 18.9 G and A aniso = 9.7 G. Compared to the situation observed in the silicon nitride where the nitrogen defects are only observed after rough treatments, the nitrogen defects are easily detected in the silicon oxynitrides.

Time Dependent Resistance Increase in Poly-Si Load Resistor due to Hydrogen Diffusion from Plasma-Enhanced Chemical Vapor Deposition Silicon Nitride Film in High Density Static Random Access Memories

A study has been done on hydrogen diffusion into poly-Si load resistors in high density static random access memories (SRAMs) from plasma-enhanced chemical vapor deposition (CVD) silicon nitride film. For the first time, it was found that the resistance of load resistors in 1 Mbit SRAMs increases in proportion to the time during high temperature duration testing, resulting in time dependent retention current decrease. This phenomenon is due to the decrease in trap density at the poly-Si grain boundaries, which in turn is caused by continual hydrogen diffusion from plasma-CVD nitride film. It was also confirmed that hydrogen diffuses through not only upper-side dielectrics but also back-side dielectrics and/or the poly-Si/dielectric interface. Furthermore, from these experimental results, a empirical equation is proposed for the resistance change, and the increase in resistance over 10 years is predicted to be 20% at 125° C.

A quarter-micrometer interconnection technology using a TiN/Al-Si-Cu/TiN/Al-Si-Cu/TiN/Ti multilayer structure

An interconnection structure using a TiN/Al-1% Si-0.5% Cu/TiN/Al-1% Si-0.5% Cu/TiN/Ti multilayer conductor was investigated as a quarter-micrometer interconnection candidate for 256-Mb DRAMs. It was found that intermetallic compounds such as TiAl/sub x/ were formed at both grain boundaries of Al-Si-Cu and interfaces between Al-Si-Cu and TiN of the multilayer, resulting in both increase in Vickers hardness and suppression of stress relaxation. The multilayer conductor strip, which was covered with plasma-enhanced chemical vapor deposition silicon nitride (P-SiN), suppressed stress-induced voiding after heat treatment at 500 degrees C. Electromigration tests for quarter-micrometer wide multilayer strips indicated the improvement in the mean time to failure and the increase of the standard deviation.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Electroplated solder joints for flip-chip applications : Edward K. Yung and Iwona Turklik. IEEE Trans. Compon. Hybrids mfg Technol.14(3), 549 (1991)

Silicon nitride has been widely used in microelectronic device fabrication processes for encapsulation, surface passivation and isolation. In this paper we report new applications of plasma-enhanced chemical vapor deposition (PECVD) silicon nitride films that can be deposited at a temperature lower than the soft bake temperature of normal photoresists. Lift-off of the silicon nitride film was carried out using standard positive photoresist. GaAs MESFETs and InP MISFETs with self-aligned gates were successfully fabricated using this lift-off process of low temperature PECVD silicon nitride.

Optimization of GaAs-on-silicon MESFET structures : G. Halkias, et al. Solid-St. Electron.34(10), 1157 (1991)

Silicon nitride has been widely used in microelectronic device fabrication processes for encapsulation, surface passivation and isolation. In this paper we report new applications of plasma-enhanced chemical vapor deposition (PECVD) silicon nitride films that can be deposited at a temperature lower than the soft bake temperature of normal photoresists. Lift-off of the silicon nitride film was carried out using standard positive photoresist. GaAs MESFETs and InP MISFETs with self-aligned gates were successfully fabricated using this lift-off process of low temperature PECVD silicon nitride.

Exhaust gas detoxifying systems used in microelectronics : N. Proust, C. Fresnais and F. Bourdon. Revue Technique Thomson-CSF23(3), 619 (September 1991)

Silicon nitride has been widely used in microelectronic device fabrication processes for encapsulation, surface passivation and isolation. In this paper we report new applications of plasma-enhanced chemical vapor deposition (PECVD) silicon nitride films that can be deposited at a temperature lower than the soft bake temperature of normal photoresists. Lift-off of the silicon nitride film was carried out using standard positive photoresist. GaAs MESFETs and InP MISFETs with self-aligned gates were successfully fabricated using this lift-off process of low temperature PECVD silicon nitride.