Deposition Rate Monitor using a Frequency Difference Multiplier
Original Publication Date: 1978-Mar-01
Included in the Prior Art Database: 2005-Feb-20
The measurement and control of small deposition rates using a crystal oscillator rate monitor in a vacuum deposition chamber is limited by the resolution of the frequency counter. This can be increased without limit by operating the counter for a long period of time, but in a feedback controller, the long operation time of the counter making it extremely difficult to stabilize the system. The frequency difference multiplier shown in the figure multiplies the apparent deposition rate by a factor without an increase in the measurement time, thereby permitting either increased resolution, faster system response, or a combination of both.