Quartz Crystal Microbalance

Quartz Crystal Microbalance

The UHV Quartz Crystal Microbalance (QCM) is designed to measure the film thickness or deposition rate from sources in the UHV process chamber.  

The in-vacuum QCM is comprised of three main parts: 

a) the UHV bakeable temperature-controlled sensor head (with/without shutter assembly), 

b) the quartz crystal sensor, and 

c) the electronic monitor/controller.  

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More details

The QCM monitor/controller vibrates the crystal sensor at a set frequency, during the deposition the material coats the crystal surface and alters the frequency at which the crystal vibrates. This change in frequency is related to the amount (mass) of material being deposited and so the film thickness can be determined.  

In the idle state the QCM may be retracted to the following positions: 

  1. fixed position (i.e. no linear motion)
  2. behind a tantalum shield  
  3. behind the chamber cryopanel 
  4. behind an isolation gate valve  

The length of the linear motion is therefore dependent on the process chamber diameter and the desired idle position.  

Applications: 

The QCM is ideally suited for rate measurement of most metals in the UHV processes. However, the following exceptions may interfere with the stability and accuracy of the QCM measurements and so should be avoided: 

  • Reactive metals (sodium, potassium) 
  • Alkaline earth metals (calcium, magnesium) 
  • Volatile metals (mercury, gallium, indium) 
  • Metastable metals (titanium, zirconium) 
  • Magnetic metals (iron, cobalt, nickel) 

 

Special Add-on Feature  

To maximise the system up-time and minimize disruption to growth campaigns, the QCM may be isolated vacuum-wise from the process chamber. This allows quick exchange the crystal sensor without venting the main process chamber. Ideal for production systems and busy research labs!  

Specifications

Feature 
Mounting flangeDN40CF or DN63CF
Linear travel (mm)150 – 500 mm or static
Cooling water2x Ø 6mm Swagelok
Bakeout temperature200 °C
Motion InterlockPosition sensor included
Motorized controlOptional
ShutterOptional
Gate valved isolationOptional

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