Synchronization between temperature measurement device and radiation sources

A system for measuring temperature of a substrate comprising:

• one or more sources, having response times defined by rise and fall times of less than 100 milliseconds, deployed in association with the substrate, the one or more sources switchable between:
• an active state in which the one or more sources heat at least one portion of the substrate, and an inactive state in which the one or more sources cause substantially no radiation or a negligible amount of radiation to be generated;
• a controller including at least one processor and configured to switch the one or more sources between the active state and the inactive state;
• and
• a temperature measuring device configured to perform a temperature measurement of the at least one portion of the substrate,
• wherein the temperature measuring device and the switching between the active and inactive states are synchronized to each other such that:
• i) the one or more sources are switched to the inactive state from the active state by the controller within the response time and the temperature measurement is started immediately after the one or more sources are switched to the inactive state,
• ii) immediately after completion of the temperature measurement, the one or more sources are switched to the active state from the inactive state by the controller within the response time, and
• iii) the temperature measurement is performed only when the one or more sources are in the inactive state,
• thereby preventing radiation from the one or more sources from obscuring the temperature measurement performed by the temperature measuring device,
• wherein the temperature measuring device is configured to perform the temperature measurement by sensing radiation within a measurement wavelength band, wherein the measurement wavelength band is selected to exclude a peak emission wavelength of the one or more sources.

A method comprising:

• switching one or more radiation sources having response times defined by rise and fall times of less than 100 milliseconds between:
• an active state in which the one or more radiation sources irradiate at a substrate so as to heat the substrate, and
• an inactive state in which the one or more radiation sources emit substantially no radiation or emit a negligible amount of radiation;
• performing by a device:
• a first radiation measurement during the inactive state, the first radiation measurement including radiation corresponding to thermal emission by the substrate, and
• a second radiation measurement during the active state, the second radiation measurement including radiation corresponding to thermal emission by the substrate and radiation reflected by the substrate in response to radiation emitted by the one or more radiation sources,
• wherein the device is synchronized to the switching between the active and inactive states such that:
• i) the one or more sources are switched to the inactive state from the active state within the response times and the first radiation measurement is started immediately after the one or more sources are switched to the inactive state,
• ii) immediately after completion of the temperature measurement, the one or more sources are switched to the active state from the inactive state within the response times, and
• iii) the first radiation measurement is performed only when the one or more sources are in the inactive state,
• thereby preventing radiation from the one or more sources from obscuring the radiation measurement performed by the device,
• wherein performing the first radiation measurement and the second radiation measurement includes sensing radiation within a measurement wavelength band, wherein the measurement wavelength band is selected to exclude a peak emission wavelength of the one or more radiation sources;
• and
• calculating, based on the first and second radiation measurements, at least one of a reflectivity of the substrate or an emissivity of the substrate.