Fiber Bragg grating sensor for in situ substrate temperature measurement in a magnetron sputtering system

Fiber Bragg grating sensors are used to monitor physical parameters like temperature even in inaccessible, unconventional environments. One such application is monitoring the temperature of a substrate from the back surface like any conventional thermocouple sensor and simultaneously monitoring the temperature on the front surface, which is in contact with ion plasma in a magnetron sputtering system. Since thin film parameters depend on substrate temperature, precise measurement plays an important role and thermocouple-like sensors are erroneous when placed on the front side of a substrate exposed to ion plasma. The lateral variation of temperature on the front side for larger substrates also has been established at four different locations, exploiting the multiplexing capability of FBGs. In this report, we demonstrate and utilise the versatility and capability of fiber Bragg grating sensors for online monitoring of substrate temperatures during thin film deposition, for the first time to the best of our knowledge, on different types of substrates. FBG based approach is expected to significantly aid in better control of thin film devices.