Plasma temperatures and spray particle velocities were measured in a low pressure plasma spray system. Plasma temperatures of 6,540–9,050 K were calculated from argon atomic emission spectra by the Boltzmann slope method. Peak particle velocities up to 365 m/s were measured with a laser velocimeter for 44 pm Al2O3, spray powder. Measured particle velocity distributions show a strong dependence on process chamber pressure over the range of 50–600 Torr.

In this paper, external electrical measurements and a circuit model are used to obtain indirectly the plasma potential, electron density, ion current density, and sheath thickness. In a revised and extended circuit model, each element describes a current-transport mechanism. Each mechanism is described by an analytical expression in terms of previously specified plasma parameters. The model is applicable in capacitive discharges with equal-area electrodes, and it can be expanded to consider other systems. To verify its applicability, electrical measurements of voltage, current and phase angle in an SF6 : O2 discharge are used to calculate the plasma impedance. Electrical plasma measurements yield time-averaged values for the impedance; the values obtained for each device reflect this dependency. After the calculation of each electrical device, SPICE 3.7a simulations separated the individual contribution of current transport by each mechanisms and validated the assumptions. The plasma parameters obtained by this technique agree well with a Langmuir-probe measurement, solutions of the Boltzmann transport equation, and data published in the literature.

An apparatus is described which can acquire, in less than a second, a spectrally-resolved, spatial profile of the light emitted from a parallel plate, rf glow discharge. This is achieved by imaging the discharge emission onto the entrance slit of a monochromator with its spatial integrity preserved. Then a spatially-resolved image is detected by an optical multichannel detector which is oriented parallel to the entrance slit. Spatial profiles from nonreactive gas discharges demonstrate that the symmetry of an rf discharge can be dramatically affected by the nature of the gas.

Magnetron plasmas are of great current interest for semiconductor manufacturing applications because of their high ion density and low operating pressure. We have studied the properties of a magnetron ion etching system using CF4, CF4/O2, and CF4/H2 with respect to the plasma chemistry and the interaction of the plasma with the etched substrate. The higher dissociation and ionization rates lead to significant changes in the species present in the plasma as compared to a conventional reactive ion etching (RIE) plasma. The F atom concentration in a CF4 magnetron plasma is much higher than in a RIE plasma. The addition of O2 leads to only a small further enhancement and produces a decrease in the Si etch rate. Addition of H2 suppresses the F atom concentration slightly, produces very little C-F polymer, and does not lead to highly selective etching of SiO2 over Si. The highly dissociated species in the magnetron plasma produce less C-F polymer, both on the wafer and on the chamber walls, relative to RIE.

A large area (2.8 cm2) electron beam source has been developed, characterized, and applied to anisotropic etching of SiO2 masked with photoresist. This beam operates at high pressures (up to 100 mTorr), in reactive gases, and at more than 10 mA/cm2. Beam current can be controlled in several ways independently from beam energy. The 100 – 900 eV low energy beam propagates with collimation through several cm of reactive gas, and is believed to minimize space charge defocusing by collisionally ionizing the working gas.

We have utilized an ultrahigh vacuum surface analysis system interfaced via a load-lock to a flexible diode dry etching apparatus to study vacuum transferred CF4/H2 reactive ion etched silicon surfaces by X-ray photoemission spectroscopy (XPS). From the observation and analysis of silicon-fluorine bonding underneath the fluorocarbon film and the dependence of the abundance of fluorosilyl species on the thickness of the fluorocarbon overlayer, the role of the fluorocarbon film in the slow-down of the Si etch rate has been elucidated: The role of the fluorocarbon film is to “protect” the Si surface from attack of fluorine, rather than prevent the escape of SiF4 etch product.

Epitaxial GaAs films have been deposited using a Plasma-Enhanced Metal Organic Chemical Vapor Deposition (PE-MOCVD) technique. This technique uses an RF discharge to dissociate arsine and hydrogen upstream from the substrate. The plasma increases the partial pressure of arsenic above the substrate and improves the growth and quality of GaAs films grown at low teyperature and with low arsine flow rates. We have used photoluminescence, Hall measurements, dislocation etches, and transmission electron microscopy (TEM) to study the properties of films grown with and without plasma. enhancement under a variety of reactor conditions. Specular epitaxial layers of n-GaAs were grown with and without plastua at, very low pressures (2 – 3 Torr) on semiinsulating GaAs substrates. Layers grown both with and without the plasma showed good mobility and photoluminescence at deposition temperatures of 650°C. At lower deposition temperatures the films deposited with the plasma were better than those deposited without the plasma. A KOH-NaOH eutectic etch revealed a better structural quality in films deposited with plasma at low arsine partial pressure.

The reactive ion etching of polycide films (TiSi2 over polysilicon) is discussed. Experimental conditions which lead to anisotropy and the identification of certain contamination problems as well as their solution are presented.

A pulsed electromagnetic inductive discharge is used to prepare amorphous thin films. The pulsed plasma is generated by supplying pulsed current (maximum peak 70 kA, period 13 μs ) to a one-turn coil wound round a Pyrex glass tube. Amorphous silicon(a-Si) and amorphous carbon (a-C) films were deposited in mixture gas (20% SiH4, 80% Ar) and pure methane, respectively. The films formed on the subltrates set normal to the tube axis at a pressure of 10–200mTorr and a gas flow rate of 10–20 sccm. Deposition rate was about 1 nm per a single discharge shot. The deposited films of a few hundred nanometer thickness adhered well to room-temperature substrates. The a-Si films had optical gap of ˜ 1.7 eV. The a-C films were transparent in the IR range and had optical gap of 1.0 ˜ 2.0 eV. Relative spectral intensity measurement of the Balmer emission from hydrogen atoms showed that the electron temperature at the high electromagnetic compression phase is 1˜ 2 eV in silane discharges and 2˜5 eV in methane discharges.

We have established a correlation between contact resistance, measured on VLSI MOS integrated circuits at final electrical test, with thermal wave modulated reflectance signal measured just after the metal contact hole etch process. This correlation exists because etching past the time that a particular contact hole is cleared of oxide (i.e., overetching) causes (a) a thinning of the underlying shallow ion-implanted low-resistivity silicon layer with a resulting increase in the contact resistance, and (b) damage to the silicon. Damape was measured on the actual product wafers with the thermal wave modulated reflectance method employing low-power laser beams in a noncontact, nondestructive manner. Hence, the thermal wave measurements of damage make it possible to monitor the etch processing on the product wafers.

Our results show monotonic increases in both the damage (mod. reflec. from 30 to 260 units) and contact resistance (from 40 to 180 ohms/contact) with overetch time up to 1.5 min., at which point polymer deposition alters the dependence by screening the silicon surface. We show results obtained for three categories of VLSI devices (SRAM, PROM, FIFO), and report on the advantages and limitations of this new method for realtime plasma etch inspection.

Photoresist removal from silicon substrates has been achieved by a dry processing method using a plasma remote from the substrate to produce active species. Although the principal gas used is oxygen, the addition of small amounts of other gases (N2O, HCI, HBr, H2, Cl2, CF4, and CHF3) has been shown to significantly enhance resist removal. The measured temperature dependences indicate that the effect of these additives may be a combination of oxygen atom production enhancement by neutral and ionic mechanisms as well as independent reaction with the resist.

Amorphous carbon films exhibit a wide range of optical, electrical and mechanical properties which make them candidates for a number of applications such as protective coatings and insulators in electronic devices. We describe the effects of a magnetic field applied at the powered electrode in a capacitively coupled rf discharge on the optical and electrical properties of amorphous carbon films deposited on substrates mounted on both electrodes. In the case of substrates placed on the powered electrode, the film properties appear to be very sensitive to the magnetic field strength. At the highest magnetic field, the deposition rates are very much higher than those obtained in the absence of a magnetic field. The optical gap varies from 1.1 eV to 2.7 eV depending on the deposition conditions. The electrical conductivities of the films are very low and show a complex dependence on the applied electric field.

We have studied the influence of different GaAs surface treatments on the chemical composition and electrical behavior of the Si 3 N4 -GaAs interface, where Si 3 N4 was plasma enhanced chemical vapor deposited (PECVD) onto the treated GaAs(100) substrate. The chemistry of the resulting interface has been studied by X-ray photoelectron spectroscopy (XPS). It has been demonstrated that the chemical composition of the Si 3 N4-GaAs interface is drastically dependent on GaAs surface pretreatment and r.f. plasma excitation frequency. Output-input powers characteristics have been measured on chemically treated planar MESFET after Si3N4. passivation.

We have deposited a range of silicon oxides by the Remote Plasma Enhanced CVD method. By varying gas mixtures and/or substrate temperature, it is possible to deposit films that are essentially stoichiometric SiO_, Si-deficient oxides which have OH groups but no SiH and Si-rich oxides which have SiH groups and no OH. This paper addresses three issues : (1) the nature of the infrared vibrations associated with the SiH and SiOH groups; (2) the use of D for H substitutions to study the vibrations in (1); and (3) the chemical origin of the SiOH group in the Si-deficient films.

Hydrogenated amorphous germanium (a-Ge:H) thin films have been grown by DC proximity glow discharge deposition using GeF,/H2 as the source gas mixture. The film growth rate decreases with increasing substrate temperature because of the temperature activation of the competitive “etching” reaction: GeF, + Ge -2GeF 2. At sufficiently high substrate temperature and GeF4, partial pressure, this reaction dominates and film growth is suppressed. The hydrogen fraction in the source gas mixture appears to determine the extent of decomposition of GeF4. The deposition rates of germanium films grown from SiF4/GeF4/H2 and Ar/GeF4,/H2 under similar gas fraction and discharge power conditions are compared. The results suggest that Si species catalyze the deposition of Ge in SiF4/GeF4/H2 glow discharges. a-Ge:H films grown from GeF4/H2 have optical, electronic and structural properties similar to films grown by GeH, glow discharge.

The ability to pattern VLSI wafers by plasma etching through SiO2 without causing structural damage and chemical contamination to the underlying silicon material is today highly desired. Examples are the plasma etching of metal/silicon contact holes and the fabrication of charge injection windows for EEPROM devices. Damage to underlying silicon, which may adversely affect contact resistance, oxide breakdown or charge retention properties, occurs as the oxide is reduced in thickness below a certain penetration depth (Dox). Dox is the effective projected range of damage-producing particles in Si0 2, and is a function of the distributions of energy, mass, etc., of the plasma constituents. In this paper we describe the use of thermal wave modulated reflectance in conjunction with a simple tapered-oxide film structure to measure the depth of penetration of etch-induced damage through SiO 2. Results on the dependence of the penetration depth on RIE self-bias voltage and other observations of etch-induced surface modifications are reported.

The effect of oxygen plasma stripping environments on the electrical properties of thin oxides has been studied. A barrel, parallel plate and downstream stripper are compared. Damage, measured by shifts in flatband voltage (Δ Vfb), increases in the density of interface traps (Dit), and degradation in minority carrier lifetimes, was observed in all plasma processed samples. Plasma treated wafers had 10–100 fold increases in Dit but recovered to nearly control levels after a 450 °C anneal. ΔVfb and lifetimes did not recover in all cases. Mobile ion contamination dominated in the high temperature (≥ 250 °C) downstream stripping tool. The mobile ion concentration was halved by decreasing the process temperature in the downstream etcher. Ion bombardment-induced damage appears to be most important in the parallel plate configuration. Lifetime results were poor for wafers etched in an unshielded barrel reactor and did not recover after anneal. Use of an etch tunnel improved results to control levels. Degradation of minority carrier lifetimes measured using the photoconductivity technique correlated well with changes in Vfb and Dit. This measurement provides a simple method for evaluating plasma-induced damage.

High quality stoichiometric silicon dioxide films have been deposited on silicon substrates at low pressure(1.0Torr) and low temperatures(≤ 350C) downstream and at a right angle to a microwave discharge. The deposition was accomplished by injecting 2% SiH4 in helium downstream of a N20 microwave generated discharge. Infrared spectroscopic analysis has determined that no detectable SiH, SiOH, Si-H2o or SiN chemical complexes were present in any films deposited at temperatures above 250C. Rutherford Backscattering and Forward Scattering Detection Spectroscopy were used to determine the elemental composition and hydrogen concentration in the films, respectively. The thick films were found to be stoichiometric with no detectable elemental impurities. The measured hydrogen concentration in the thin films was comparable to that measured in thermally grown Si0 2 of approximately the same thickness. The quality of the thin oxides(<30nm) has been determined by fabricating MOS devices from the Si-Si0 2 system.

The time evolution of the electron density and the optical emission intensity in response to a square wave modulated RF excitation of helium-silane mixtures has been studied and compared to that for the more conventional CW discharge. In addition, the films deposited from CW and modulated RF glows have-been compared on the basis of absorption coefficients and photoconductivities. Films deposited from modulated glows at substrate temperatures below 200°C have significantly smaller optical bandgaps than those deposited from comparable CW discharges. The bulk electron density in the modulated discharge undergoes a complex temporal variation and its time average value can be significantly larger than that in the CW glow despite the lower average power. A dissociative attachment process involving silane radicals, SiHn (n = 1 to 3), is identified as the most probable cause.

Emission from CH and H radicals was monitored during the deposition of amorphous carbon films in a capacitively coupled rf glow discharge. Both the spectral and spatial distributions of the emission were studied. The relative intensity of the CH and H emission was found to be sensitive to changes in discharge parameters. Preliminary results indicate a correlation between the ratios of the CH to H emission intensities and the optical properties of the deposited films.