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SEMI D15-1296 © SEMI 1996, 2003 3 Q ax or Q ay is longer than (L t – 2* λ L ) , L e is recommended to be (L t – 2* λ L ). 6.4.1 If the measurable length of the instru ment is shorter than the recommended length, then the…
SEMI D15-1296 © SEMI 1996, 2003 2
4.1.5 long wavelength cut-off,
λ
L
— wavelength that
the attenuation ratio of its amplitude becomes a
standard value when the traced profile is passed through
the high-pass wavelength filter which eliminates form
element.
4.1.6 minimum zone method straightness — the
smallest distance between two parallel straight lines
between which all of objective profile is included (see
ISO 1101, Section 3.1).
4.1.7 optical interferometric flatness Measuring
instrument — instrument that analyzes the surface
irregularities of a target, from the distribution of light
intensity of laser interferometer between the target
surface and datum flat.
4.1.8 optical stylus method measuring instrument —
instrument that uses the same profile method that a
stylus method instrument uses. This instrument uses the
displacement transducer to apply the spotlight to the
target surface instead of using the stylus to apply the
spotlight.
4.1.9 phase correct filter — a profile filter which does
not cause phase shifts between total profile and filtered
profile.
4.1.9.1 The standard transmission coefficients at cut-
off wavelength are 50%.
4.1.10 pre-travel (and post-travel), L
p
— eliminated
portions from a traced length for avoiding the profile
distortion caused by transient response of the cut-off
filter.
4.1.10.1 Recommended pre-travel with 2CR filter is
double the long wavelength cut-off, λ
L
, at the beginning
of the traced length and no post-travel.
4.1.10.2 Recommended both pre-travel and post-travel
with phase correct filter are the same as long
wavelength cut-off, λ
L
.
4.1.11 real profile — An intersection of a target surface
with a plane perpendicular to the surface (see Figure 2).
4.1.12 sampling length, L
s
— the length of the profile
for calculations of waviness parameters in an evaluation
length (L
e
).
4.1.13 short wavelength cut-off,
λ
c
— wavelength that
the attenuation ratio of its amplitude becomes a
standard value when the traced profile is passed through
the low-pass wavelength filter which eliminates
roughness element.
4.1.14 streak — a defect whose appearance is a
transparent line on the glass substrate surface. It can
either be caused by a micro surface discontinuity or a
cord due to the heterogeneity of glass composition.
4.1.15 stylus method measuring instrument —
instrument that traces on a section of a surface by a
stylus, records irregularity on the surface in an enlarged
form, and indicates its amplitude as parameters (see
ISO 3274).
4.1.16 traced length — total traversing length of stylus
or spotlight.
4.1.17 waviness — components of surface irregularities
with spatial wavelength intermediate between long
wavelength (flatness) and short wavelength (roughness)
(see Figure 2).
4.1.17.1 Discussion — Especially on FPD substrates,
those components cause visual irregularity of the shade
of the panel due to deviations of the cell gap.
4.1.17.2 Waviness includes not only periodic waviness,
but also streaks.
5 Measuring Instrument
5.1 Method — Stylus method measuring instrument,
optical stylus instrument, or optical interferometric
flatness measuring instrument.
5.2 Stylus or Spotlight
5.2.1 Shape — circular cone or sphere
5.2.2 Tip Radius — from 2µm to 0.8 mm (0.03 inch)
5.2.3 Spotlight Diameter of Optical Stylus Method —
0.2 mm (0.0079 inch) or less
5.2.4 Horizontal Resolution of Interferometer — 0.2
mm (0.0079 inch) or less
5.3 Measuring Force for Stylus Method — 4 mN (0.4
gf) or less
5.4 Sampling Interval — 0.2 mm (0.0079 inch) or less
5.5 Profile Filter — 2CR filter or phase correct filter
5.5.1 Discussion — The filtering method should be
specified because the evaluated value of W
fpd
with
phase correct filter will be smaller than that with 2CR
filter.
6 Measurement Conditions
6.1 Target Surface — The pattern surface (see SEMI
D4, Section 5)
6.2 Long Wavelength Cut-Off,
λ
L
— 8 mm (0.3 inch) or
25 mm (1 inch)
6.3 Short Wavelength Cut-Off,
λ
c
— 0.8 mm (0.03
inch)
6.4 Evaluation Length, L
e
— Is recommended to be Q
ax
or Q
ay
, total edge length of quality area of a substrate. If
SEMI D15-1296 © SEMI 1996, 2003 3
Q
ax
or Q
ay
is longer than (L
t
– 2*λ
L
), L
e
is
recommended to be (L
t
– 2*λ
L
).
6.4.1 If the measurable length of the instrument is
shorter than the recommended length, then the
overlapped section, which contains several traced
profiles covering all of the recommended lengths,
should be used to evaluate W
fpd
.
6.5 Sampling Length, L
s
— Is recommended to be 20
mm (0.79 inch) at λ
L
= 8 mm (0.3 inch) or 25 mm (1
inch) at λ
L
= 25 mm (1 inch).
7 Test Specimen
7.1 A clean FPD glass substrate. No strain or oils
should be seen by the naked eye with fluorescent lamps
or incandescent lamps.
8 Measurement Procedure
8.1 Put the specimen on the leveled stage of the
instrument without bend and leave for five minutes or
more to condition the specimen to room temperature.
8.2 Put the stylus on the specimen and measure a real
profile parallel to the edge of substrate by tracing the
surface.
8.3 Apply the bandpass profile filter to the real profile
and get the bandpass-filtered waviness profile.
8.4 Calculate the FPD Waviness — W
fpd
with manual
template method or computer-aided method from the
bandpass-filtered waviness profile.
9 Reporting Results
9.1 Measurement Location and Direction — Describe
the measurement location and direction on the report;
for example, measure along the following two
directions:
a. the center line of the specimen parallel to the long
edge
b. the center line of the specimen parallel to the short
edge
9.2 Interpretation of Results — Show the measurement
results in units of 0.01 µm (micron) and count fractions
of 0.5 and over as a unit and cut away the rest.
Table 1 Example: Measurement Result
Direction L
e
W
lcd
Long Edge **mm 0. **µm
Short Edge **mm 0. **µm
Measuring Condition
Surface — The pattern surface
Instrument — Stylus method (type of instrument)
Long cut-off,
λ
L
— 8 mm
Short cut-off,
λ
c
— 0.08 mm
Sampling length, L
s
— 20 mm
Figure 1
Explanation of L
e
, L
p
, L
s
SEMI D15-1296 © SEMI 1996, 2003 4
Figure 2
Explanation of Surface Profiles