The difficulty to polish CaF2 substrate

Because the transmission of UV grade Fused silica is very low at 157nm , is not suitable for the lithography application. So CaF2 is a very good material with high transmission at 157nm. So, the requirement of CaF2 is huge in manufacturing the PVC.
 
In lithography application, the roughness of the surface should less than 10nm, the flatness requirement and surface quality requirement is also high, it is really very difficult to polish the CaF2 substrate,
 
- CaF2 is soft, affect the flatness and surface quality.
- Residual stress, very easy to be chipped or broken
- Will deform in very little difference of temperature
- The cleavability of crystal will also affect polishing
 
LaserStates has specific polishing method to assure the polishing quality.
 

(Capability of Substrates)

Attribute
Windows
Lenses
Prisms
Diameter
+0/-0.1mm
+0/-0.1mm
(Strong capability in Dia.45-60mm)
-
Length & Width
±0.1mm
±0.1mm
±0.1mm
Thickness
±0.1mm
±0.1mm
±0.1mm
Clear Aperture
>85%
>85%
>80%
Parallelism
<1 arc minute
-
-
Centration
-
<3 arc minutes
-
Angle Tolerance
-
-
<3 arc minutes
Attribute
Windows
Lenses
Prisms
Flatness
Lambda/2-Lambda
Limit Lambda/4 @633nm
Lambda/2-Lambda
Limit Lambda/4 @633nm
Lambda/2-Lambda
Limit Lambda/4 @633nm
Surface Quality
S/D 40-20
S/D 40-20
limit S/D 40-20
 

 

Contact sales@laserstates.com for more information.