Deposition Of Amorphous Carbon Films Research Articles

Plasma-deposited amorphous carbon films as planarization layers

A dry planarization process has been developed that utilizes plasma-enhanced chemical vapor deposition of amorphous carbon films. The characteristics of the films depend on deposition conditions such as source gas composition, rf power, degree of ion bombardment, temperature, pressure, and electrode spacing. Planar films were deposited at low temperatures (< 50 °C) with low ion bombardment energy (< 10 V) and high deposition rates (100–300 nm/min). These conditions are desirable for ultra-large-scale integrated circuits fabrication, in which the thermal budget and damage must be minimized while maintaining a high throughput. A high degree of planarization over long distances was obtained. By using 2.5-μm-thick carbon films, the height of 1.5 μm steps was reduced to less than 0.2 μm for 400-μm-wide trenches, providing better than 85% planarization. The planar films have low viscosity and molecular weight, and their molecular structure is similar to that of the source gas. A post-deposition hardening step was utilized to improve the compatibility of the films with subsequent processing steps. Submicrometer features were patterned in bilayer resists consisting of these planarization layers in combination with either wet- or dry-deposited inorganic imaging layers.

Spectroscopic Measurements of the Production and the Transport of CH Radicals in a Methane Plasma Used for the CVD of a-C:H

Spatial and temporal variations of CH radicals in an rf discharge in methane for the deposition of amorphous carbon film were measured by optical emission spectroscopy and laser-induced fluorescence (LIF) spectroscopy. The temporal variation of CH emission from the excited A2Δ state suggested that the electron energy was deeply modulated by the rf field. The spatial distribution of CH in the ground X2Π state showed a broader profile than the time-averaged emission profile of CH(A2Δ), indicating the broader spatial production pattern for the CH(X2Π) and its diffusional transport. The absolute density of CH(X2Π) was also obtained, from which the flux of CH onto the substrate was estimated. The density and the spatial profile of CH were strongly affected by diluent Ar gas. These results were compared with a simulation and discussed in relation to the film deposition.

Diagnostics of high-frequency discharges in CH4/H2 by time- and space-resolved optical emission spectroscopy

The diagnostic technique of the rf glow discharge at 13.56 MHz is developed by using the spatiotemporally resolved optical emission spectroscopy. New experimental evidence that the temporal excitation rate at the sheath peaks in phase with the maximum of the total current is obtained in a parallel-plate geometry at 13.56 MHz in CH4(10%)/H2 under a typical condition of the plasma chemical vapor deposition of amorphous carbon film at room temperature.

マイクロ波放電による有機化合物プラズマとアモルファスカーボン膜析出

マイクロ波放電による有機化合物プラズマとアモルファスカーボン膜析出

Pulsed electromagnetic inductive plasma-enhanced chemical-vapor deposition of amorphous carbon films

A pulsed electromagnetic inductive methane discharge process was developed to form amorphous carbon thin films. In order to estimate the methane plasma state in the pulsed plasma process, the time-resolved excitation temperature was measured by means of relative spectral intensity method. At the high electromagnetic compression phase the pulsed plasma has an excitation temperature of the same order (20 000–50 000 K) as in the conventional rf glow discharges. The deposited thin films are transparent in the IR and adhere well to room-temperature substrates. The optical energy gap and the electrical conductivity of the amorphous carbon films are investigated and compared with the amorphous carbon films prepared with rf glow plasma chemical vapor deposition. The optical gap is observed to decrease from 1.26 to 1.14 eV as the deposition temperature and the charging voltage increase. It is shown that dynamic pulsed plasma flows affect the phase transition from a diamondlike structure to a graphitic structure.

Modification of Surfaces and Surface Layers by Non Equilibrium Processes

Plasmas are examples of non-equilibrium phenomena which are being used increasingly for the synthesis and modification of materials impossible by conventional routes. This paper introduces methods available by describing the construction and characteristics of some equipment used for the production of different types of plasmas and other non-equilibrium phenomena. This includes high energy ion beams. The special features, advantages and disadvantages of the techniques will be described. There are a multitude of potential applications relevant to electronic, metallic, ceramic, and polymeric materials.However, scale-up from the laboratory to production equipment depends on establishing a better understanding of both the physics and chemistry of plasmas as well as plasma-solid interactions. Examples are given of how such an understanding can be gained. The chemical analysis of polymer surfaces undergoing modification by inert gas, hydrogen or oxygen plasmas is shown to give physical information regarding the relative roles of diffusion of active species, and direct and radiative energy transfer from the plasma. Surface modification by plasma depositing a new material onto an existing substrate is discussed with particular reference to the deposition of amorphous carbon films. Applications of the unique properties of these films are outlined together with our current understanding of these properties based on chemical and physical methods of analysis of both the films and the plasmas producing them.Finally, surface modification by ion beams is briefly illustrated using examples from the electronics and metals industries where the modification has had a largely physical rather than chemical effect on the starting material.

Deposition of Amorphous Carbon Films by Laser Induced CVD

ABSTRACTAmorphous carbon (a-C) films were prepared by photodissociation of C2H3Cl or CCl4 gas using a pulsed ArF excimer laser (193nm). An increase in the substrate teiperature decreased the deposition rate. For C2H3Cl4 the maximum deposition rate of 10Å/min was attained at a partial pressure of 0.1 Torr and room temperature. In contrast, for CCl4, the maximum deposition rate of 10Å/Min was obtained at a partial pressure of 3 Torr and room temperature. This difference may be attributed to the different absorption cross sections for the two gases. The structural and mechanical properties were leasured. An Auger analysis showed the chlorine content in the a-C film deposited at room temperature to be 1% for C2H3Cl and 8% for CCl4. The Mohs hardnesses of the a-C filis deposited at room teiperature were 7 and 2 for C2H3Cl and CCl4, respectively. It was concluded that both sp2 and sp3 bonds existed between neighboring C atoms at low temperatures, whereas SP2 bond was predominant at temperatures higher than 300°C.

The Relationship Between Emission Spectroscopy and Optical Properties of Amorphous Carbon Films

ABSTRACTEmission 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.

Effect of H2 Plasma Etching during Glow-Discharge Deposition of Amorphous Carbon Films

Amorphous carbon films were prepared by the glow-discharge decomposition of C2H2, C2H4, and C2F6 at various rf powers and substrate temperatures (Ts). The deposition rate (DR) of a-C:H and a-C:H:F decreases with increase in Ts. These results are discussed in terms of the H-plasma etching of a-C:H films during the deposition. The optical, electrical and structural properties of the a-C:H films are also examined as a function of the rf power.

Diagnostics and modelling of a methane plasma used in the chemical vapour deposition of amorphous carbon films

In an RF-discharge methane plasma, the dissociation rate of CH4 in collisions with electrons has been measured using a laser absorption technique. The measured rate increases as the RF power increases and as the gas pressure decreases. The electron energy distribution function f( epsilon ) and the electron density ne have also been measured by a heated electrical probe. The measured f( epsilon ) is quite different from the Maxwellian distribution and rather close to the Druyvesteynian distribution. The dissociation rate constant deduced from f( epsilon ) and the reported cross-section when multiplied by the measured ne is consistent with the results of the laser absorption method. Based on these measurements a modelling of the plasma has been performed using a set of rate equations for CH4 and the various neutral and ionic species produced in the plasma. The calculated degree of dissociation for CH4 in the plasma agrees well with the measured results. The most abundant neutral radical in the plasma predicted by the model is CH3, while CH5+ is the most abundant ionic species.