The plasma-enhanced chemical vapour deposition (PECVD) of siliconoxynitride from silane, ammonia and nitrous oxide was studied using an ASM vertical parallel plate reactor.Films varying from PECVD oxide (refractive index no1.50) to PECVD nitride (n=2.00) were analyzed using ellipsometry, UV-visible reflection spectroscopy, Fourier-transform infrared transmission spectroscopy (FTIR), nuclear reaction analysis (NRA), Rutherford backscattering (RBS) and electron spectoscopy for chemical analysis (ESCA).Stress measurements were performed using a Fizeau interferometer.

Titanium nitride films were deposited from TiCl4 /NH3 mixtures in a rf glow discharge.The deposition was carried o t at pressures between 0.1 and 0.7 Torr, RF powers of 0.1 to 1.1 watt/cm2, and temperatures between 400°C and 600°C.The films deposited at 600°C had low chlorine content and resistivities in the range of 100 to 200 μΩ-cm.Films deposited at temperatures below 500°C contained large amounts of chlorine (> 15 at %) and showed poor electrical properties.The films were further characterized by Rutherford Backscattering Spectroscopy (RBS), X-ray Photoelectron Spectroscopy (XPS), and Auger Electron Spectroscopy (AES).The effect of plasma parameters on the deposition rate and film properties is discussed.Comparisons to films prepared by reactive sputtering of titanium in a nitrogen atmosphere are presented.

Three series of Ti-N films with varying nitrogen contents from about 8 to 52 at.% N were deposited by triode ion plating at temperatures of 773, 623 and 373 K, respectively.Marked changes in the structures of the films with decreasing temperature were observed by x-ray diffraction.Stoichiometric δ-TiN which showed (220) preferred orientation at 773 K changed to (111) at lower temperatures.At intermediate nitrogen concentrations α-Ti (002) decreased and a new ε-Ti2N (002) developed with decreasing temperature.Very smooth and dense films could be produced at the lower temperatures.

RF reactive sputtering of aluminum in argon-nitrogen mixture has been used to deposit basal oriented aluminum nitride films at temperatures lower than 200°C.X-ray diffraction studies of films deposited in 40–60% nitrogen show very high degree of crystallinity.A characteristic step-like decrease in target induced dc bias and the deposition rate (at a constant rf power level) is observed when the nitrogen content is increased above about 20%.The plot of target bias vs.nitrogen content shows a typical hysteresis loop which decreases in size at higher power levels, thus indicating nitride formation at the target surface.Glow discharge mass spectrometry was used to monitor the ions arriving at the substrate.There is a dramatic decrease in Al+ ion current when the nitrogen percentage in the gas mixture is increased above 20%.

In the present paper structural and chemical changes which can occur in the surface and near-surface properties of the substrate during anisotropic dry etching of SiO2 on Si will be reviewed.Silicon specimens which had been etched in CF4/X%H2 (X≤40) have been characterized by X-ray photoelectron emission spectroscopy, He ion channeling, H profiling and Raman scattering techniques.Key results of our studies are summarized as follows: Plasma exposure of a Si surface leads to the deposition of a thin (≤50Å thick) C,F-film.A Si-carbide containing Si region is formed during RIE which is localized near the fluorocarbon-film/Si interface.The near-surface region (∼30–50Å) of the Si substrate is also heavily disordered as found by ion channeling and Raman scattering.A modified, less damaged Si region has been found in the case of hydrogen-based etching gases, which extends from about 30–50Å from the surface to a depth in extent of 250Å and contains a high concentration (∼ 5 at.%) of H as shown by hydrogen profiling techniques.From the observation of Si-H and Si-H2 vibrational modes by Raman scattering it has been shown that some of the H is bonded to the Si lattice.

The damage of reactive ion etching to shallow junctions is an important consideration in advanced technology.In this paper, the damage incurred during contact etch is studied, with emphasis on those defects responsible for junction leakage of shallow junctions.Shallow p+/n and n+/p junctions have been prepared with depths of 160 nm.Junction leakage measurements have been made for various amounts of silicon loss up to within 20 nm of the junctions by using a CHF3 + CO2 plasma.The degree of chemical and structural damage has been characterized by using photoluminescence, SIMS, and spreading carrier profiling.

The leakage current density was found to depend strongly on contact area and increase rapidly with junction etch depth after the etched surface has extended to within 80 nm of the junction boundary.The concentration and depth of damage increases with increasing plasma exposure until saturation.Etching induced defects are observed in photoluminescence, and one such defect is identified as a carbon interstitialcy.Enhanced diffusion effects were observed for both chemical contamination from the etch gas and the junction dopants.The spatial distribution of the chemical and structural damage has been found to correlate with the junction leakages.The annealing behavior of damage has also been investigated.

A method is presented to nondestructively monitor damage in silicon caused by reactive-ion or plasma etching on actual product wafers or test wafers immediately following the etch step.Data is taken on product wafers by scanning the 1-micron laser probe spot across and along the bottom of RIE-etched trenches.The onset of silicon damage brings a marked increase to the thermal wave (TW) signal: as the RIE bias voltage was increased from -60 volts to -250 volts, the TW signal increased monotonically by 1230%.The effects of other RIE process parameters on the damage level were also measured.This study allowed the RIE process variables to be adjusted to minimize damage to the silicon surface.

Plasma processing is an essential part for the fabrication of GaAs ICs.It was found that the exposure of sulfur doped n-type GaAs layers to a plasma of helium, oxygen, or nitrogen changed their electrical characteristics without introducing crystalline damage, as observed by electron diffraction measurments or etching.Exposure to a plasma depletes the surface carrier concentration but the mobility remains unchanged.Compared to O2 and N2 the helium plasma has the largest effect on the GaAs surface.Exposure of S-doped GaAs layers to a He plasma at 350°C produces two new deep levels at 840-nm and in the region between 863 and 872-nm.These levels were not observed for a He plasma exposure at room temperature or for O2 plasma exposure at 350°C.

Etch rates of Kapton H polyimide film in SF6 - O2 plasmas (0.25 torr) were studied as a function of the input gas mixture, the excitation frequency (25 kHz -450 kHz; 13.56 MHz) and the biasing mode.The treated surface was examined by X P S, SEM and contact angle measurement.

The ion and neutral species of the plasma were sampled and analyzed by mass spectrometry.A proposed kinetic analysis of the etching mechanism is in good agreement with the experimental data.

The etching of polyimide thin films and tungsten thin films has been studied as a function of bias voltage using two quartz crystal microbalances (QCM) installed in a low pressure 13.56 MHz rf plasma system.One of the QCM's is biased (rf bias was used for the polyimide films; de bias was used for the tungsten films) and the other QCM is unbiased.In this way, the influence of energetic positive ion bombardment on etching can be studied.The etching of polyimide is studied in CF4-O2 glow discharges whereas CF4-H2 gas mixtures were used in the etching of tungsten.In the tungsten etching studies, the surfaces were vacuum-transferred to an Auger electron spectrometer for surface analysis.

Reaction of Al0 3Ga0 7As with molecular chlorine was studied with and without simultaneous bombardment by energetic argon ions.The reaction products signals were measured as functions of surface temperature.For the purely thermal reactions, the main products below 600 K were AlCl3, AsCl3 and GaCl3.The etching rates were two orders of magnitude lower than those of pure GaAs.With simultaneous ion bombardment, the reaction product signal of AsCl3 at room temperature increased by almost a factor of four over the corresponding thermal reaction signal.The comparable enhancement factor for pure GaAs was ∼6.

Ion backscattering and channeling techniques have been employed to measure the etching rate of amorphous and single crystal Si by XeF2 under similar conditions.Both (100) Si on sapphire and (111) Si on spinel showed higher etching rates compared to amorphous Si.However, measurements of the etching rate using a Si cell aligned to the axis and along the planes under similar conditions did not show appreciable difference in the etching rate compared to the etching rate with random orientation of the cell.Presence of the analyzing 4He+ beam during etching enhances the etching rate to twice the value when compared to post etching analysis with the same beam.The enhancement of the etching rate due to ion induced decomposition of XeF2 have been considered in the explanation of the experimental results.

The chemical etching of W(100) single crystals and polycrystalline tungsten foils using a XeF2 molecular beam has been studied with and without simultaneous bombardment by energetic inert ions.The surface fluorine concentration, measured under different XeF2 pressures (10−7 to 10−5 torr) and ion current densities, is found to be always less than a monolayer.Depth profiles of the fluorine layer show that in both single crystal and poly samples, the fluorine is surface localized, although slightly deeper in the W(100).A kinetic model is presented to account for the enhanced etching under ion bombardment.The mechanism proposed is mainly a defect driven enhancement of the etch yield.This model is consistent with both the fluorine concentrations measured in this work as well as the etch product yields reported by Winters.

We discuss specific examples of desorption due to electron or photon bombardment of solids, in which the repulsive interactions that result in particle expulsion can be clearly identified.A particularly interesting example is the desorption of positive ions from alkali-halides.Classical trajectory calculations are used to provide a picture of the atomic-scale motion during desorption.The results show that dynamic distortions of the lattice play a crucial role in the desorption process.

In this paper we present experimental results and a theoretical model for the interaction of CF3+ and CH4+ with SiO2 surfaces.A comparision of the sputter rates for CF3+ and CH4+ with a molecular sputtering model shows that there is a chemical enhacment in the etch rate for CF3+ but not for CH4+.By comparing the Si (LVV) AES spectra for these two surfaces we have determined that the enhancement is due to the strong Si-F bond promoting the formation of volatile carbon containing compounds.

The reactions of atomic and molecular fluorine on silicon surfaces have been studied using x-ray photoelectron spectroscopy (XPS) and an ultrahigh vacuum (UHV) compatible microwave discharge effusive beam source of reactive species. The results indicate that molecular fluorine is dissociatively chemisorbed to form SiF2-like species on the surface. This reaction saturates at approximately monolayer surface coverage. Atomic fluorine also reacts initially to form SiF2-like surface species. Once the available surface sites are occupied, however, the fluorine atoms penetrate and react with silicon in the underlying layers. As the fluorine uptake increases, many of the subsurface silicon atoms become fully fluorinated. That is, the reaction product becomes SiF4-like. In contrast, preliminary studies indicate little difference in the behavior of atomic and molecular chlorine. These findings are compared with previous results for XeF2 adsorption, and their implications for plasma etching mechanism definition are discussed.

A molecular beam probe technique has been used to investigate the role of ion bombardment of the film surface during the plasma polymeriz-ation process.Thin films have been deposited in a vacuum chamber from a molecular beam containing all the plasma species and these were compared with similar deposits from a beam with the charged particles deflected away.A comparison was made of deposition rates, vis/UV and IR absorption spectra of the films.It was found that the deposition rate was increased 20% with the elimination of ion bombardment.Ions incident on the film surface during deposition cause a net ablation of the film.The ion bombardment also causes an increased absorption of UV and near UV light by the film resulting in a noticeable yellowing.No change was observed in the IR spectra of the films with ion deflection.