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SEMI P37-1102 © SEMI 2001, 2002 6 Table 4 Flatness, Wedge and Surface Roughness FLATNESS ERROR IN FL ATNESS QUALITY AREA Class Frontside Flatness, within Flatness Quality Area Backside Flatness, within Flatness Quality A…

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SEMI P37-1102 © SEMI 2001, 2002 5
Table 1 Specifications for Edge Length, Squareness, and Thickness for Square Substrates
Edge Length Min.
L
Edge Length Max.
L
Squareness
Minimum Mean
Thickness
T
Maximum Mean
Thickness
T
Units
151.9 152.1 0.01/25.40 6.25 6.45 mm
Table 2 Specifications for Chamfered and Rounded Edge Dimensions
T A A C C D D E E
Nominal Min. Max. Min. Max. Min. Max. Min. Max. Units
6.35 0.20 0.30 0.30 0.70 0.50 1.00 0.25 0.30 mm
Table 3 Substrate Material Characteristics
Property Symbol Characteristic
Temperature range for CTE requirement 19 to 25°C
Coefficient of Thermal Expansion CTE (ppb/°C)
Class A: mean: 0 ± 5 ppb/°C
6 ppb/°C total spatial variation
Class B: mean: 0 ± 10 ppb/°C
10 ppb/°C total spatial variation
Class C: mean: 0 ± 20 ppb/°C
10 ppb/°C total spatial variation
Class D: mean: 0 ± 30 ppb/°C
10 ppb/°C total spatial variation
Specific Stiffness (Young’s elastic modulus
divided by density)
Ε/ρ (m
2
s
-2
)
≥ 3 × 10
7
Note: ppb stands for parts per billion.
5 mm
Flatness
quality
area
Edge Length
Edge Length
5 mm
5 mm5 mm
Figure 3
Front and Back Side Flatness Quality Area
SEMI P37-1102 © SEMI 2001, 2002 6
Table 4 Flatness, Wedge and Surface Roughness
FLATNESS ERROR IN FLATNESS QUALITY AREA
Class Frontside Flatness, within
Flatness Quality Area
Backside Flatness, within
Flatness Quality Area
Low Order Thickness Variation
(LOTV), within Flatness Quality
Area (See Note 2.)
λ
spatial
> (edge length)
Units
A 100 peak-to-valley 100 peak-to-valley 100 nm
B 75 peak-to-valley 75 peak-to-valley 75 nm
C 50 peak-to-valley 50 peak-to-valley 50 nm
D 30 peak-to-valley 30 peak-to-valley 30 nm
NOTE 1: λ
spatial
is the spatial period of the flatness error.
NOTE 2: Evaluated after removing wedge angle.
FLATNESS OVER ENTIRE SURFACE
Frontside Flatness
λ
spatial
≤
(edge length)
Backside Flatness
λ
spatial
≤
(edge length)
Units
1000 peak-to-valley 1000 peak-to-valley nm
NOTE 1: λ
spatial
is the spatial period of the flatness error.
WEDGE
Wedge angle Units
≤ 100
microradians
LOCAL SLOPE OF FRONT SURFACE
Local slope angle
400 nm
≤
λ
spatial
≤
100 mm
Units
≤ 1.0
milliradians
FRONT SIDE SURFACE ROUGHNESS
Surface Roughness in Quality Area (Figure 6),
λ
spatial
≤
10
µ
m
Units
≤ 0.15 rms
nm
BACK SIDE SURFACE ROUGHNESS
Surface Roughness over entire back surface,
50 nm
≤
λ
spatial
≤
10
µ
m
Units
≤ 0.5 rms
nm
NOTE 1: rms is root mean square error. λ
spatial
is the
spatial wavelength of the roughness.
SEMI P37-1102 © SEMI 2001, 2002 7
P
1
Mask substrate surface
Flatness error
Local slope
angle
Figure 4
Definition of Flatness Error and Local Slope Angle
P1 is the plane that minimizes maximum deviation of the surface.
α
Mask substrate
P
1
´
P
2
P
1
P
1
´ || P
1
Figure 5
Definition of Wedge Angle,
α
P
1
and P
2
are the planes that minimize the maximum deviation of the front and back surfaces, respectively.