Toho Technology FLX 2320-S


  1. Theory 
  2. How to use the system
  3. Calculator

I. Theory

The FLX-2320-S measures the change in the radius of curvature of your wafer or substrate caused by the deposition of a stressed thin film. The following equation is used to calculate the stress : 


is the biaxial elastic modulus of the substrate [Pa]
     h          is the substrate thickness [m]
               is the film thickness [m]
              is the substrate radius of curvature [m]
     σ          is the average film stress [Pa]


After the film has been deposited, the substrate deforms from the initial radius R1 to a new Radius R2. Since the stress is inversely proportional to the radius, the effective radius R is given by : 

The thin film stress is now determined by using the effective radius R in the equation described above. 

From that, it becomes clear that the radius has to be measured before and after the deposition !



II. How to use the system

Please refer to the user manual : 

III. Calculator 

Use this excel sheet to play with the equation above. Useful to calculate the film thickness required to correct the bow of your substrate for instance.