Improvement of the response time for a fast PID closed loop control

From time to time, there exists a critical issue to handle multi-channel OES system for a reactive sputtering process which demands high response time of the reactive gas supply. For example, a 3-channel PEM system shown in the figure below has three spectrometers in the PEM controller. Each spectrometer’s configuration has its own recording interval (=exposure time multiplies average number), which might be different from others due to slight differences in the alignments of collimators and the plasma density are different in each gas supply section. For the individual control of each channel, the recording intervals are different, but the spectra data acquisition from spectrometers to the computer’s host software needs to collect all three channels sequentially at a time. That means, if the recording interval settings for 3 channels are 100ms, 125ms, 150ms individually(for example), then the complete system recording interval for a closed loop control is the sum of three individual settings, i.e. 375ms (=100ms + 125ms + 150ms). This result is too bad for a fast PID closed loop control and such kind of control can not provide the highest quality of the film deposited on the substrate. Therefore, the new developed EMICON xMC series is able to acquire spectra data for each channel individually without waiting the others. In this way, each gas supply section can work properly in their optimized configuration to maintain the best quality of the film deposited. The high speed PID closed loop controlled process is achievable finally.



Of course, this technology can be used for any kind of applications with the demands on different settings for the recording intervals, but the response time is demanded to be very high. Now, only Plasus EMICON MC/HR series can do it.