Abstract: A method includes embedding at least part of a transparent crystal within a wall and a liner of a processing chamber, depositing a transparent thin film on a surface of the transparent crystal that is exposed to an interior of the processing chamber and depositing a process film layer on the transparent thin film. The method includes receiving light reflected back from a surface of the transparent thin film and a surface of the process film layer and detecting, by a spectrometer within the received light, a first spectrum that is representative of the process film layer. The method includes calculating, by a processing device coupled to the spectrometer, a process drift of the processing chamber based at least in part on the first spectrum.

Abstract: A system includes a transparent crystal, at least part of which is embedded within a wall and a liner of a processing chamber. The transparent crystal has a proximal end and a distal end, the distal end having a distal surface exposed to an interior of the processing chamber. A transparent thin film is deposited on the distal surface and has chemical properties substantially matching those of the liner. A light coupling device is to: transmit light, from a light source, through the proximal end of the transparent crystal, and focus, into a spectrometer, light received reflected back from a combination of the distal surface, a surface of the transparent thin film, and a surface of a process film layer deposited on the transparent thin film. The spectrometer is to detect a first spectrum within the focused light that is representative of the process film layer.

Abstract: A system includes a transparent crystal, at least part of which is embedded within a wall and a liner of a processing chamber. The transparent crystal has a proximal end and a distal end, the distal end having a distal surface exposed to an interior of the processing chamber. A transparent thin film is deposited on the distal surface and has chemical properties substantially matching those of the liner. A light coupling device is to: transmit light, from a light source, through the proximal end of the transparent crystal, and focus, into a spectrometer, light received reflected back from a combination of the distal surface, a surface of the transparent thin film, and a surface of a process film layer deposited on the transparent thin film. The spectrometer is to detect a first spectrum within the focused light that is representative of the process film layer.