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SEMI D9-0303 © SEMI 1994, 2003 3 orientation corner X Y corner cut (3 places) Figure 2 Orientation Corner and Corner Cut 4.4.10 squareness  dev iation of the outline of the substrate from a true square or rectangle. Usi…

SEMI D9-0303 © SEMI 1994, 2003 2

4.2.3 stain  organic or inorganic material on the

surface.

4.2.4 blur — any erosion of the surface; generally

cloudy in appearance, it sometimes exhibits an apparent

color.

4.3 Surface Defects

4.3.1 scratch



a surface fissure generally caused

during handling.

4.3.2 sleek — a very shallow type of scratch on the

polished surface that is sometimes invisible when the

viewing angle is changed.

4.3.3 latent scratch — a scratch which is usually

invisible but when subjected to an etching action by

dipping into a detergent or a corrosive solution, such as

an acid, the previously invisible scratch becomes visible

due to the minor removal of surface glass.

4.3.4 chip — a region of material missing from the

edge of the glass substrate, which is sometimes caused

by processing or handling.

4.3.5 pit/dig — small indentation on the glass substrate

surface.

4.3.6 bump  a small protuberance on the glass

substrate.

4.3.7 crack — a fissure located at the sheet edge area

or central area.

4.3.8 streak — a defect with a very small undulation

on the glass substrate surface.

4.4 Dimensional Properties

4.4.1 outsize dimension  vertical and horizontal

dimensions of the glass substrate.

4.4.2 thickness



the distance between the front

surface and the back surface of a glass substrate at same

single point.

4.4.3 thickness variation — any differences between

maximum and minimum values within the thickness of

a glass substrate.

4.4.4 warp  defined as the maximum distance from a

reference plane to the guaranteed surface; this includes

twists, partial rises or declines in the glass compared

with the reference plane. Warp expression a condition

of the whole glass (substrate).

4.4.5 waviness  the residual unevenness after the

long wavelength component (warp) and the short

wavelength component (surface roughness) have been

eliminated. This is also called “FPD Waviness” when

referring specifically to FPD substrates, as in SEMI

D15.

4.4.6 surface roughness — the criterion for the

smoothness of the sheet surface. Usually the randomly

selected areas on the sheet surface are measured by a

surface analyzer. Details are defined in SEMI D7.

4.4.7 beveling  grinding out or shaping substrate

edges by lapping or grinding.

chamfered edge

radiused edge

Figure 1

Beveling

4.4.7.1 chamfered edge  a beveled angle of

approximately 45° in respect to the surface and cut edge

surface. One characteristic is that part of the cut edge

surface remains. For this reason, R-beveled edges have

come to be used in conjunction with chamfered edges

in liquid crystal applications. Chamfered edges with

particularly small widths are also referred to as “string

bevels”. (See Figure 1.)

4.4.7.2 R beveled edge — a beveled shape of an arc in

respect to the surface and cut edge surface. One

characteristic is that the complete cut edge surface is

ground with a wheel and processed into a frosted glass

state. Generally, in TFT liquid crystals, R-beveled

edges are used more often. (See Figure 1.)

4.4.8 orientation corner — the corner of a substrate

which identifies the pattern surface and the rotational

orientation. It is defined by the X and Y dimensions in

the following figure. It is also commonly known as

“orientation flat” or “orifra”.

4.4.9 corner cut — removal of the corners of the

substrate by either lapping or grinding. As with the

orientation corner, this is defined by the X and Y

dimensions, but generally, most corner cuts have a X

and Y of the same length.

SEMI D9-0303 © SEMI 1994, 2003 3

orientation

corner

corner cut

(3 places)

Figure 2

Orientation Corner and Corner Cut

4.4.10 squareness  deviation of the outline of the

substrate from a true square or rectangle. Using the

drawing below, it is defined as PS or PL, but must be

recorded with a or b dimensions. Dimensions a and b

can be decided voluntarily, but generally, most

applications use a = S and b = L. (See Figure 3.)

≥

Figure 3

Squareness

4.5 Thermal Properties

4.5.1 coefficient of thermal expansion  expansion is

the change in length per initial length caused by a

thermal change. Concretely, it is shown as ∆L/L0,

where ∆L = L2 – L1 and L0, L1, and L2 are the lengths

of the material at the temperature T0, T1, T2

respectively. Usually, the coefficient of expansion (A),

means the average coefficient of expansion over the

temperature range T1 to T2. This is shown in the

following equation.

= (∆L/∆T)/L

= [(L

–

)/(T

–

)]/L

4.5.2 thermal shrinkage  when the substrate is heat

treated along a specific thermal profile, the relaxation

of thermal stress and the structure change occur in

material, and create the shrinkage of the substrate.

Usually it is described with ∆L/L0, where, ∆L is the

amount of change and shown as ∆L = L0 – L. L0 is the

length of material before heat treatment, and L is after

heat treatment.

4.5.3 strain point  temperature of the glass when its

viscosity is approximately 10

14..5

dPa·s. Strain point is

defined by two methods in ASTM: Test Method C336

(Elongation of Glass Fibers) and Test Method C598

(Bending in Glass Beams). In practice, the strain point

of glass is the maximum temperature at which glass can

be processed without triggering unnecessary strain.

Internal strain can be relieved by keeping (the glass) at

this temperature for 4 hours.

4.5.4 annealing point  temperature of the glass when

its viscosity is approximately 10

dPa·s. The annealing

point is the temperature at which internal strain can be

relieved in 15 minutes.

4.5.5 softening point  temperature of the glass when

its viscosity is approximately 10

7.6

dPa·s. Softening

point is defined in ASTM C338.

4.6 Chemical Properties

4.6.1 chemical durability  a measure of corrosion or

attack of a glass surface when subjected to a specific

reagent, such as acid, base, or water at a specific

concentration for a specific time and temperature.

4.7 Optical Properties

4.7.1 transmittance — percentage of incident light

which permeates the glass. It is defined as I/Io, where

Io is the strength of the incident light, and I is strength

of the permeated light. Transmittance is effected by

material composition, temperature, thickness and light

wavelength.

4.7.2 refractive index — ratio of the speed of light in

the material and in a vacuum at a specific wavelength.

The refractive index of substrate glass is between

approximately 1.50 and 1.53.

4.8 Mechanical Properties

4.8.1 density



mass per unit volume. Decided by the

mass of the material’s atomic composition and the

volume (comparative capacity, mol capacity) which it

occupies.

4.8.2 Young’s modulus



a type of elasticity ratio,

which shows the stretch (or compression) elasticity.

When stretch (or compression) deformation stress σ and

the strain ε resulting from the stress are proportionate,

the proportionate constant E = σ/ ε is called Young’s

modulus, a material characteristic.

4.8.3 shear modulus  a type of elasticity ratio which

shows divergence elasticity. When divergent

deformation stress τ and the strain Φ resulting from the

stress are proportionate, the proportionate constant

G = τ/Φ is called Shear Modulus, a material

characteristic.

4.8.4 Poisson’s ratio  the ratio between Young’s

modulus and shear modulus.

4.8.5 Vickers hardness — a type of pressure test. A

diamond pyramid indentator with a face angle of 136°

is pressed into the glass surface to find the degree of

hardness by measuring trace indentation on the overall

squareness.

4.9 Electrical Properties

4.9.1 dielectric constant  the proportionate dielectric

constant which is the ratio between a vacuum dielectric

constant and the material dielectric constant.

4.9.2 dielectric loss — the phenomenon, or volume, of

(electricity) loss through heat when a dielectric is

introduced to an alternating current.

4.9.3 resistivity — the reciprocal of electric

conductivity.

4.10 pattern surface — the main area where device

patterns can be formed, determined by the orientation

corner, etc.

4.11 quality area — the center area to the substrate

where specified substrate quality criteria (primarily

internal defects, surface contamination, surface defects,

waviness, and surface roughness) are applicable.

5 Referenced Documents

SEAJ(Semiconductor Equipment Association of Japan)

Liquid Crystal Display Manufacturing Equipment

Dictionary

quality area

Figure 4

Quality Area

2 Semiconductor Equipment Association of Japan, 7-10 Shinjuku 1-

chome, Shinjuku-ku, Tokyo, 160-0022 Japan. Tel:+81-3-3353-7589,

fax:+81-3-3353-7970, http://www.seaj.or.jp

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representations as to the suitability of the standards set

forth herein for any particular application. The

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respecting any materials mentioned herein. These

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