Plasma Deposition System Research Articles

Preparation and characterization of wide area, high quality diamond film using magnetoactive plasma chemical vapour deposition

A magnetomicrowave plasma was used for the low pressure deposition of diamond. The important point in the plasma deposition system is to set the electron cyclotron resonance (ECR) condition (875 G in the case of a 2.45 GHz microwave) at the deposition area. The high density plasma (above 1 × 10 11 cm -3) necessary for high quality diamond formation was obtained by effective microwave absorption near the magnetic field, satisfying the ECR condition. The plasma is uniform at the discharge area (160 mm in diameter) and uniform diamond films of a high quality are obtained. From an investigation of diamond formation in the range 10 -2–50 Torr in the same deposition system, it is obvious that the lower pressure reduces the formation temperature of diamond to 500 °C and that the effective species for diamond formation are low energy radicals.

Effects of Excited Plasma Species on Silicon Oxide Films Formed by Microwave Plasma CVD

By using a microwave plasma deposition system, effects of highly excited plasma species on the film formation of silicon oxide have been studied and the roles of excited ion and radical species have been investigated by emission spectra of the excited plasma species. A strong correlation was confirmed between film quality and the amount of highly excited ion species transported to the substrate. Furthermore, high quality films could be formed by increasing the amount of the excited species.

Degradation of High and Low Voltage Amorphous Silicon Thin Film Transistors Due to Air Leak

ABSTRACTAmorphous Silicon TFT performance is shown to be strongly affected by an air leak into a plasma deposition system during film growth. The introduction of a controlled air leak into the system raises the oxygen content of the active layer. For both high and low voltage transistors (HVTFT & LVTFT) the drive current, FET mobility, and threshold voltage are degraded with increasing leak rate. Moreover, the stability of HVTFTs containing a space charge limited region is adversely affected by increasing leak rate.

Surface photovoltage in a-Si:H

The surface photovoltage (SPV) was measured as a function of temperature and light intensity for 2.0 eV and 2.5 eV photons for clean, oxidized and ligth soaked a-Si:H films. The undoped samples were transferred by a vacuum lock from the plasma deposition system to the analysis chamber and investigated by the kelvin technique. The results suggest that the SPV for 2.5 eV photons is mainly determined by the Dember voltage whereas for 2.0 eV photons by band bending reduction due to (weak) minority carrier recombination via surface states.

Persistent photoconductivity in compositional modulated amorphous semiconductors

We have synthesized compositional modulated amorphous semiconductor of a-Si:H/a-SiN x :H multilayer films consisting of 25–90 periods of 20–200 A thick a-Si:H and 60 A a-SiN x :H by alternating the plasma-gas mixture in the plasma deposition system. These new amorphous semiconductor structures exhibit persistent photoconductivity (PPC), that is, a long lived excess conductivity after a brief light exposure at room temperature. The dependence of the PPC on exposure time, light intensity, exposure and measurement temperature has been investigated.

Ellipsometric and Optical Study of Amorphous Hydrogenated Carbon Films

A low‐frequency plasma deposition system was used to prepare amorphous hydrogenated carbon (a‐C:H) films. The growth energy was varied by changing the power and/or pressure of the plasma. Ellipsometry and optical absorption were used to obtain the optical energy gap, the density of states, and the refractive index. Ion sputtering was used in conjunction with ellipsometry and Auger electron spectroscopy to get absolute sputtering rates. The plasma deposited a‐C:H is amorphous with optical energy gap of approximately 2.0–2.4 eV. These a‐C:H films have higher density and/or hardness, higher refractive index, and lower optical energy gaps with increasing energy of the particles in the plasma, while the density of states remains unchanged. These results are in agreement and give a fine‐tuned positive confirmation to an existing conjecture on the nature of a‐C:H films (1).

SiO2 planarization technology with biasing and electron cyclotron resonance plasma deposition for submicron interconnections

Bias electron cyclotron resonance (ECR) plasma deposition technology is proposed to planarize submicron interconnections with a high aspect ratio (height/space of interconnection) in which rf bias is applied to the substrate of the ECR plasma deposition system. The technology has the following advantages. First, the concave region of the narrow gap between submicron interconnections with a high aspect ratio above 1.0 can be planarized and formed at the same insulator thickness as that of the convex region. This is due to high directionality of ECR plasma particles. Second, both deposition and etching rates can be controlled by adjusting the gas flow rates as well as the rf and microwave power. Third, an rf bias can be applied from the initial stage of the planarization process. This is because of sputter-etching with O2 ions without Ar, thus enabling a shorter planarization time. Using the bias-ECR plasma deposition technology, the 0.5 μm line/space Al (0.5 μm thickness) interconnection surface can be perfectly planarized.

Design of plasma etching and deposition systems

Plasma etching and plasma deposition are widely used processes in the fabrication of microelectronic devices. The design of equipment used to carry out these processes involves vacuum technology as well as numerous considerations involved in the mechanical and electrical design of such machinery. In this paper, the design concepts will be discussed with reference to commercially available machinery as examples of functional designs.

Plasma Organosilicon Polymers: Deposition, Characterization, and Application in Multilayer Resist

Divinyl tetramethyl disiloxane (DVS), hexamethyl disilazane (HMDS), and methyl trimethoxysilane (MTS) polymer films were deposited on p‐type silicon substrates using plasma‐enhanced chemical vapor deposition (PECVD) processing. The deposition process was implemented in a parallel‐plate, capacitively coupled plasma deposition system. Excellent film thickness and refractive index uniformity were obtained. The deposition kinetics were studied as a function of process parameters such as pressure, power, density, and substrate temperature. The polymer film's physical properties were characterized by Fourier transformed infrared (FTIR), electron spectroscopy for chemical analysis (ESCA), Auger spectroscopy, electron spin resonance (ESR), and plasma etching. These polymer films were used as an intermediate oxygen etch resistance layer in trilevel resist lithography to produce submicron image patterns (≃ 0.7 μm lines and spaces) using step and repeat photolithography.

‘‘Diamondlike’’ carbon films: Optical absorption, dielectric properties, and hardness dependence on deposition parameters

An rf plasma deposition system was used to prepare amorphous ‘‘diamondlike’’ carbon films. The source gases for the rf system include methane, ethylene, propane, and propylene, and the parameters varied were power, dc substrate bias, and postdeposition anneal temperature. Films were deposited on various substrates. The main diagnostics were optical absorption in the visible and in the infrared, admittance as a function of frequency, hardness, and Auger and ESCA spectroscopy. Band gap is found to depend strongly on rf power level and band gaps up to 2.7 eV and hardness up to 7 Mohs were found. There appears to be an inverse relationship between hardness and optical band gap.

‘Clean’ a-Si:H prepared in a UHV system

Hydrogenated amorphous Si(a-Si:H) prepared in conventional systems often contains a large amount of impurities, with O, C, and N levels as high as 0.1–1 at.%. In this paper we demonstrate that by addressing three issues related to impurities in the UHV plasma deposition system, which are contaminant impurities, cross contamination, and interfacial impurities, ‘clean’ material with a 2–4 orders-of-magnitude reduction in impurity levels can be obtained. Also sharp interfaces can be fabricated in this single-chamber reactor. The ‘clean’ a-Si:H is found to have very few defects but preliminary results indicate that the Staebler-Wronski effect is still present in the material. The UHV system provides a unique opportunity to assess the influence of impurity and to study properties intrinsic to a-Si:H.

Evolution towards thermalization, and diffusion, of sputtered particle fluxes: Spatial profiles

Particles sputtered from solid targets in plasma deposition systems, under typical vacuum conditions, slow down in collisions with the gas phase. The spatial profiles of particle fluxes at given instantaneous energy are calculated with a simple model of a particle slowing down along straight-line trajectories, subject to a continuous energy-loss process. In particular, the profiles of flux thermalization are given. Model distributions in energy and direction of sputtered fluxes, with a reasonable physical basis, are used. The accumulation and diffusion of thermalized material in the gas phase is studied also, and the stationary spatial profiles are obtained. Diffusion particle currents back to the source, or towards the substrate, can then be estimated. Scaling laws are obtained that allow the analysis of any specific deposition conditions through the masses of the sputtering and sputtered particles, the binding energy of the target, and the working pressure. Because of the simplifying assumptions of the analytical model, predictions in the particular case of light targets sputtered in a comparatively heavier atmosphere should be only regarded on an orientative basis.

Diamondlike carbon films prepared by charged particles.

The recent progress in diamondlike carbon films prepared by hydrocarbon ion or plasma gas are described. The typical systems reported are classified into three types such as plasma, ion, and neutral deposition systems and each system is discussed. Next, the physical properties and the crystal structures of these films are discussed in comparison with diamond powder. Finally, the growth process of diamond films in the case of ionized deposition is discussed based on the reported data.

Impurities in Bulk A-Si:H, Silicon Nitride, and at the a-Si:H/Silicon Nitride Interface

ABSTRACTMajor impurities in a-Si:H are O, C and N, while those in silicon nitride are H, O, C, F, Cl and excess Si. We show that a large reduction in both contaminant impurities and cross contamination achieved in the UHV plasma deposition system yields high purity a-Si:H. The impurity at the a-Si:H/nitride interface is observed to depend strongly on the order of deposition. There is a large amount of nitrogen carried over into a-Si:H when the a-Si:H is deposited after the nitride, Such a compositional asymmetry is likely to lead to an asymmetry in interface characteristics.

Amorphous Si prepared in a UHV plasma deposition system

Although glow discharge decomposition of SiH 4 has been demonstrated to yield a-Si:H films with potential for large area device applications, the a-Si:H films often have high impurity level (∼ 10 19 t- 10 20/cc). Moreover, cross contamination of dopants at interfaces between differently doped layers is a problem. Since both issues may be the key to improving material quality, a UHV plasma deposition systems has been built to address them. By controlling all sources of contaminants such as chamber walls, gas lines and gas bottles, the impurity levels have been significantly lowered to ∼10 17−10 18/cc. In addition, sharp interfaces between differently doped layers are obtained, which allow the preparation of multilayer structures.

Slowing down and thermalization of sputtered particle fluxes: Energy distributions

Particles sputtered from solid targets in plasma deposition systems, under typical vacuum conditions, slow down in collisions with the gas phase. A simple model of particle slowing down along straight-line trajectories, subject to a continuous energy loss process, allows to calculate the energy distributions of the nonthermalized component of the particle flux as a function of the distance to the source. Physically reasonable angular and energetic distributions of the flux at emission are used in the calculations. The implications on the deposited films are discussed, and previous estimates by Meyer et al. [J. Appl. Phys. 52, 5803 (1981)] are commented upon.

Productivity increase in a planar plasma deposition system: B. Mattson and T. Thompson. Solid-St. Technol. 81 (1979)

Productivity increase in a planar plasma deposition system: B. Mattson and T. Thompson. Solid-St. Technol. 81 (1979)

R.F. plasma deposition of silicon nitride layers

A versatile r.f. plasma deposition system used to deposit high quality Si 3N 4 films at low temperature (200–350°C) is described. By introducing the reactant gases separately and reactively reducing the oxygen content of the system, films which exhibited very little oxygen contamination could be deposited. Rutherford backscaterring studies were used to evaluate the atomic composition of the films. The composition was related to other parameters such as the index of refraction, the etch rate and the deposition rate. The nitride layers described here were used successfully to anneal ion-implanted GaAs with negligible surface degradation.