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Other specifications

Flatness・Light Point Defects / Categories of Off-Orientation

Flatness

Flatness

Definitions of Flatness

TTV Total Thickness Variation:
The difference between the highest and the lowest elevation of the top surface of a clamped wafer.
The back surface referenced.
TIR Total Indicated Reading:
The difference between the highest point above and the lowest point below the front surface referenced focal plane of a clamped wafer. 3 points on the front surface generally used.
LTV Local Thickness Variation:
The difference between the highest point and the lowest point within a site of the top surface of a clamped wafer.
The back surface referenced.
PLTV Percent LTV:
Percentage of sites on a wafer within the specified LTV value.
Warp The difference between the highest point above and the lowest point below the front surface referenced focal plane of an unclamped wafer.
A least square fit on the front surface generally used.

Light Point Defects

Light Point Defects

Clockwise (EJ) / Counter Clockwise (US)

Clockwise (EJ) / Counter Clockwise (US)

Planar Representation of Cubic Form

Planar Representation of Cubic Form

Example of off-orientation

Example of off-orientation

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