Device for determining partial pressures of substances in process chamber in coating process to manufacture thin layer, has lock-in amplifier comprising input terminal to which electric signals are supplied corresponding to light sources

摘要

The device (100) has multiple non-coherent light sources (1) i.e. LEDs, exhibiting various wavelengths, and modulatable with various modulation frequencies. A photo detector (8) is sensitive for the wavelengths of the light sources. A lock-in amplifier comprises an input terminal connected with the photo detector, and another input terminal to which electric signals are supplied corresponding to the light sources through input ports of an electronic switching device, where the electric signals comprise the respective modulation frequencies. The photo detector is designed as a semiconductor photodiode such as silicon-, indium gallium arsenide and germanium photodiodes. An independent claim is also included for a method for determining partial pressures of process substances in a process chamber or a flow pipe.