Tempe™ Sensor Head (Single only)
Patented 40—500°C High Vacuum Crystal Sensor System
The Tempe™ system is designed for thin film coating process control when high evaporation or chamber temperatures are present in a thin film coating process. These conditions cause excessive rate noise and lead to significant errors with process control. With the Tempe™ we keep the sensor in the range of 40—500°C, depending on process to minimize these errors.
Quartz crystals can be used upwards of 200°C with only moderate instability. As the temperature increases beyond that, there is a steep change of frequency. That means that a change of as little as 1ºC can cause a frequency shift of 10 or more Hz. The crystal monitor interprets this as coating, leading to a false rate measurement and consequently inaccurate thickness reading.
For temperatures above 200°C we use a new crystalline material called SuperQuartz™. This crystal operates stably up to 500ºC making it ideal for ALD (atomic layer deposition), CVD (chemical vapor deposition), MBE (molecular beam epitaxy), CIGS (copper indium gallium diselenide) solar cell fabrication, and OLED (organic light emitting diode) manufacturing or deposition processes.
Comprised of a 304 stainless steel crystal sensor head (suitable for 0.550″ 5 or 6 MHz quartz crystals, the standard variety), this newly patented design combines a cartridge heater with an air-cooled crystal holder. The action of these two elements allows a set point controller, which receives temperature input from a type K thermocouple embedded in the sensor housing, to add heating as needed to maintain the crystal from a range of 40ºC to 500ºC. If you operate your air-cooling from a refrigerated compressed air line you can hold the sensor to a tolerance of +/-1ºC easily. If you use unregulated compressed air, the fluctuating input temperature and pressure leads to a more realistic +/-3ºC. In either case, you are a quantum leap from the uncontrolled sensor environment that currently exists.
The air cooling is an essential ingredient of this system. With so much radiant heat present in a typical vacuum coating chamber, thermal runaway is always a problem. And since we want to use an environmentally safe coolant, we use air.
For additional information, refer to the following datasheets:
High Temperature (HT™) Crystals Datasheet
Tempe™ Datasheet
Temperature Measurement and Control of Quartz Crystal Microbalances
