NOVELTY - Method for forming barrier coating on thin film device(s) disposed in deposition chamber involves: delivering reactant material into deposition chamber (102); and forming plasma from the material by applying high frequency radio frequency (RF) power to an electrode assembly (104) in chamber to deposit barrier coating on the device(s), such that a temperature at which the barrier coating is deposited is less than 150 degrees C, the high frequency RF power is 27-81 MHz, and the pressure within the deposition chamber is maintained at 10-1000 mTorr.    USE - For forming a barrier coating on large area thin film device(s) (claimed), such as solar panels and similar devices.    ADVANTAGE - The method provides an improved plasma enhanced chemical vapor deposition (PECVD) process to produce barrier coatings (such as nitrides, oxides, carbides) for large area thin film devices, which is carried out at a low temperature of (less than 150, preferably less than 100) degrees C, and avoids degradation (at the p-i interface) of the semiconductor films already deposited on the substrate. The process provides a uniform deposition of barrier coating(s) at a high deposition rate (5 nm/second) on large thin film silicon based devices (at least 1 m x 0.5 m) at low temperature, at a high frequency 27-81 MHz, with less particulate formation over conventional PECVD processes performed at low temperatures. A stable plasma maintained over a large area substrate at high frequencies allows high ionization density resulting in high reaction rates at lower temperature, and hence effective silane utilization. The distance between adjacent rod electrodes and between the rod electrodes and thin film device(s) is within a diffusion length. The travel distance from electrodes delivering silane to the electrodes evacuating exhaust is closely spaced, which substantially minimizes silane dwell time within the deposition chamber, and minimizes formation of high order silanes and/or silicon particles. This increases percentage of plasma generated silicon nitride that is deposited onto substrates and decreases amount that is deposited onto chamber walls, as compared to conventional deposition chambers; achieves efficient consumption of reactant materials; facilitates rapid diffusion and achieves a uniform concentration; and reduces the downtime and expense associated with deposition chamber cleaning and maintenance. As the exhaust gas flow rate is higher than input gas flow rate to maintain constant pressure in the chamber, a high percentage of silane is used, as compared to conventional PECVD systems that convert only 5-10% of silane; reduces percentage of silane deposits onto the walls with overall utilization efficiency of greater than or equal to 50%, as compared to 5% with conventional PECVD systems; and further facilitates much lower gas flow rates than conventional PECVD systems, and hence requires lower capacity exhaust device. The high intensity plasma regions in the central plane of deposition chamber generate abundant atomic nitrogen, which easily diffuses to substrates without flowing through a tube or other apparatus, and encourages formation of silicon nitride with good barrier properties; generate intense UV photons that can easily flow to the substrates without passing from outside the deposition chamber through a window or other apparatus. The creation of low intensity plasma regions near the substrates reduces the electron/ion bombardment of the substrates and potential damage to the deposited silicon nitride by electrons and/or ions. The closely spaced rod electrodes allow higher RF frequencies of 27-81 MHz to be used to excite the plasma in the present PECVD system and provides higher deposition rates, as compared to the frequencies that can be used in conventional PECVD systems and show non-uniform deposition rates; and better material quality than the conventional excitation frequency of 13.5 MHz. The electrodes assembly produces well controlled standing waves and minor variations in plasma intensity when excited to frequency of 80 MHz over large substrates. The process thus allows the PECVD system to perform continuous deposition processes at a stable, steady state with stable temperature, gas flow, gas concentrations, and deposition rates; allows the manufacture of the system to be much less precise in mechanical tolerances, and less uniform in gas flow; and allows system manufacture much less expensively than conventional batch mode systems.    DETAILED DESCRIPTION - Method for forming a barrier coating on at least one thin film device disposed in a deposition chamber (102) involves: delivering a reactant material into the deposition chamber; and forming a plasma from the reactant material by applying high frequency radio frequency (RF) power to an electrode assembly (104) in the deposition chamber to deposit the barrier coating on the at least one thin film device, such that a temperature at which the barrier coating is deposited is less than 150 degrees C, the high frequency RF power is 27-81 MHz, and the pressure within the deposition chamber is maintained at 10-1000 mTorr. The reactant material comprises a reactant gas comprising silane and at least one of ammonia, nitrogen, argon, oxygen, methane and acetylene (preferably silane and ammonia). The application of high frequency RF power creates low intensity plasma regions near the at least one thin film device, and high intensity plasma regions along the central plane of the deposition chamber which generates atomic nitrogen and hydrogen; atomic nitrogen; atomic oxygen; or carbon radicals and atomic hydrogen (preferably atomic nitrogen), for ammonia, nitrogen, oxygen, methane and acetylene, respectively, that diffuses within the deposition chamber to the at least one thin film device. The electrode assembly comprises several rod electrodes that deliver the silane and one of ammonia, nitrogen, oxygen, methane and acetylene into the low intensity plasma regions, into the low intensity plasma regions. The distance between adjacent rod electrodes and between the rod electrodes and the at least one silicon based thin film device is within a diffusion length. The silane input rate is greater than the deposition rate. The at least one rod electrode further evacuates exhaust from the deposition chamber, and the travel distance from the at least one rod electrode delivering silane to the at least one rod electrode evacuating exhaust is closely spaced to substantially minimize silane dwell time within the deposition chamber. The exhaust flow rate from the deposition chamber equals or exceeds the input gas flow rate. The delivery of silane and the application of high frequency RF power are controlled to set a deposition rate.    DESCRIPTION OF DRAWING(S) - The figure shows a perspective, cutaway view of the deposition chamber.    Deposition chamber (102)    Electrode assembly (104)    Spaced rod electrodes (126)    Inlets. (122a, 122b)