NIR Diode Laser and FTIR Based Process Control for industrial CVD Reactors

摘要

An efficient process control is essential to fully exploit the potential of high yield CVD (chemical vapour deposition) processes which are key technologies in many industrial sectors. Reactor operation is typically open loop and conventional operation is driven by optimisation of process parameters based on characterisation of post processed material properties. The proposed technical approach to overcome this drawback is characterised as: Process control by a multipurpose, knowledge based feedback system. The approach followed is (i) in situ spectroscopic data of the gas phase near the surface of the growing layer as input information, and (ii) correlation of spectroscopic data with layer properties, (iii) construction of a data basis for process control. The new process control approach is currently being verified on different industrialised CVD coaters. The paper will present some results of recent process monitoring studies on deposition of SnO{sub}2 layers on glass, based on the oxidation of (CH{sub}3){sub}2SnCI{sub}2, which is used in high volume production for low-E glazings. Monitoring methods for reactor control have been selected comprising both FTIR in the mid IR and diode lasers in the near infra red (NIR-DLS), Both sensor methods have been successfully implemented into industrial environment. The NIR-DLS technology has some notable potential advantages for production process applications. For example, the technology is robust and simple to operate, interference between species can be reduced. Complementary to this FTIR demonstrate significant potential for development of new processes and for designing CVD equipment.