Langasite
La3Ga5SiO14

Crystal properties

 

 

Density

5.74 g/cm3

 

Space Group

32

SAW velocity (Vef)

m/s = 2736

Electromechanical coupling coefficient

K²s = 0,38

Temperature coefficient
first order:
second order


TCD a1 = 0
TCD a2 = -6,8*10^-8 (1/C°)^2

Working face

wafer diameter minus 3 mm

Orientation

Primary flat is perpendicular to X' axis 
with accuracy +/-15 min
Yxlt/48.5°/26.6°

Edge chipping

No chipping inside the working area and on the primary flat. Chipping can be accepted outside the working area if the width is less than 0.5 mm, and the cumulative length is less than 5 mm.

Polishing

No dimples, cracks, unpolished areas, ontaminants in working area under x50 magnification. Scratches visible at x50 magnification are allowed in working area if their quantity is lower than 3 on one wafer and less than 20 in a lot of one hundred wafers.

Backside face

Ra>0.2 microns.

 

 

 

 

 

76,2 mm wafers

100 mm wafers

Diameter

76.2 mm +/- 0.2 mm

100.0 mm +/- 0.15 mm

Thickness

0.50 mm +/- 0.05 mm

0.50 mm +/- 0.05 mm

Primary flat

22 mm +/-2.0 mm

32.5 mm +/-2.5 mm

Flatness (under vacuum)

< 10 mm

< 10 mm

LTV

<2.2 microns 
for the base 20 mm x20mm

<2.2 microns 
or the base 20 mm x20mm

Bow (free wafer)

< 50 mm

< 50 mm

Secondary flat

11 mm +/-2.0 mm

11 mm +/-2.0 mm