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SEMI P28-96 © SEM I 1996 4 Figure 2 Frame-in-Frame Figure 3 Bars-in -Bars NOTICE: These st andards do not purport to addres s safety issues, if any, as sociated with their use. It is the responsibility of the user of the…

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SEMI P28-96 © SEMI 19963
dimension for the inner frame (F
i
), and the width(s) of
the frames (W
o
and/or W
i
). The dimensions should
follow these guidelines:
outer frame: F
o
= 15–30 micrometers (µm)
inner frame: F
i
= F
o
/2
width: W = 1.0–1.5 µm for F
o
≤ 24 µm, or 1.5–2.0
µm for F
o
≥ 24 µm
NOTE: The width of the inner and outer bars may differ.
These specifications define a range of frame sizes and
their interfeature spacing. Users may modify the frame-
in-frame dimensions as dictated by design rules,
process, and/or measurement equipment requirements.
7.2.3
Bars-in-Bars (see Figure 3)
7.2.3.1 The bars-in-bars test pattern is designed to be a
test pattern for overlay measurement on metrology
equipment. Each axis has two designed edges per axis
on each side of each imaging step. The additional
information gained by having two features on each
level, each with a centerline, may reduce the
measurement uncertainty as compared to the box-in-
box design.
7.2.3.2
The overlay test pattern consists of two sets of
bars, the outer set and the inner set. Each set of bars is
arranged to form an overlay measurement frame as
shown in Figure 3. Each bar-in-bar set is normally
defined by a different imaging step; that is, the set of
inner bars corresponds to the substrate geometry and
the set of outer bars corresponds to the overlaying
pattern (5.4), or vice versa. The two sets of bars are
designed to be concentric.
7.2.3.3
The design elements are the pi tch for the outer
set of bars (B
o
), the pitch for the inner set of bars (B
i
),
the length of the outer bars (L
o
), the length of the inner
bars (L
i
), and the width(s) of the bars (W
o
and/or W
i
).
The overlay test pattern dimensions should follow these
guidelines:
outer bar set: B
o
= 15–30 µm
inner bar set: B
i
= B
o
/2
outer bar length: L
o
= 50%–70% B
o
inner bar length: L
I
= 50%–70% B
i
width: W = 1.0–1.5 µm for B
o
≤ 24 µm, or 1.5–2.0
µm for B
o
≥ 24 µm
NOTE: The width of the inner and outer bars may differ.
These specifications define a range of box sizes and
their interfeature spacing. Users may modify the box-
in-box dimensions as dictated by design rules, process,
and/or measurement equipment requirements. The user
should recognize that edges in close proximity may
cause measurement errors.
7.3
User Considerations for Overlay-Metrology
Equipment
7.3.1 Pattern Acquisition — To ensure automatic
acquisition of the desired overlay test pattern by an
image-based automated overlay metrology equipment,
one or more of the following may be required:
1. Separation of each overlay test pattern as required
per metrology equipment specification.
2. Use of only one overlay test pattern in the
measurement field-of-view.
3. Printing unique labels next to each overlay test
pattern using the proximity guideline in Section
6.3.3.
7.3.2
Feature Dimensions — For each overlay test
pattern, only a range of feature dimensions is defined
(e.g., paragraph 7.2.2.3). The user and supplier together
should determine that the dimensions of the overlay test
patterns they select are those that consider design rules,
the user’s process capability, and limitations of the
microlithography and measurement equipment.
7.3.2.1
Width Dimensions (frame-in-frame or bars-in-
bars test patterns) — When all features of the overlay
test pattern are imaged at the same process step, the
widths of the inner and outer features are recommended
to be equal, and of the same polarity, in order to
minimize overlay-measurement errors.
Figure 1
Box-in-Box
SEMI P28-96 © SEMI 1996 4
Figure 2
Frame-in-Frame
Figure 3
Bars-in-Bars
NOTICE: These standards do not purport to address
safety issues, if any, associated with their use. It is the
responsibility of the user of these standards to establish
appropriate safety and health practices and determine
the applicability of regulatory limitations prior to use.
SEMI makes no warranties or representations as to the
suitability of the standards set forth herein for any
particular application. The determination of the
suitability of the standard is solely the responsibility of
the user. Users are cautioned to refer to manufacturer’s
instructions, product labels, product data sheets, and
other relevant literature respecting any materials
mentioned herein. These standards are subject to
change without notice.
The user’s attention is called to the possibility that
compliance with this standard may require use of
copyrighted material or of an invention covered by
patent rights. By publication of this standard, SEMI
takes no position respecting the validity of any patent
rights or copyrights asserted in connection with any
item mentioned in this standard. Users of this standard
are expressly advised that determination of any such
patent rights or copyrights, and the risk of infringement
of such rights, are entirely their own responsibility.
Copyright by SEMI® (Semiconductor Equipment and Materials
International), 3081 Zanker Road, San Jose, CA 95134. Reproduction
of the contents in whole or in part is forbidden without express written
consent of SEMI.
SEMI P29-0997 © SEMI 19971
SEMI P29-0997
GUIDELINE FOR DESCRIPTION OF CHARACTERISTICS SPECIFIC TO
HALFTONE/ATTENUATED PHASE SHIFT MASKS AND MASK BLANKS
1 Purpose
1.1 This guideline defines the characteristics specific
to halftone/attenuated phase shift masks and mask
blanks.
1.2 This guideline is intended to provide a baseline for
specification of phase shift masks and mask blanks to
be agreed between the supplier and user.
Because the phase shift mask is still under
development, it may be needed to continue the research
activity to standardize a final specification.
2 Scope
2.1 This guideline applies to halftone/attenuated phase
shift masks and mask blanks for g-line, i-line, KrF,
ArF, and/or DUV wavelengths.
2.2 These types of masks can be called either halftone
or attenuated phase shift masks. This guideline uses
“halftone phase shift masks” as the nomenclature.
2.3 Items not described in this guideline shall conform
to SEMI P1.
3 Referenced Documents
NOTE: As listed or revised, all documents cited shall be the
latest publications of adopted standards.
3.1 SEMI Documents
SEMI P1 — Specification for Hard Surface Photomask
Substrates
SEMI P22 — Guideline for Photomask Defect
Classification and Size Definition
4 Terminology
4.1 Terms for General Description
4.1.1 halftone phase shift mask — a photomask
designed to increase resolution through intentional
control of light transmittance and phase against a
transparent part by replacing a conventional opaque
pattern with a thin, partially transmitting film (halftone
shifter film) that controls light phase difference and
transmittance.
4.1.2 phase shift mask — a photomask designed to
increase resolution through intentional control of the
exposure light phase.
4.2 Terms for Structural Description
4.2.1 additional film type opaque ring — an opaque
ring composed of light shield materials other than the
shifter.
4.2.2 embedded shifter type opaque ring — an opaque
ring composed of small rectangles or line/space patterns
in a shifter.
4.2.3 multilayer halftone phase shift mask — a
halftone phase shift mask having multiple thin films of
different material compositions to give a certain phase
difference and transmittance. The layer that adjoins the
substrate should be called the first layer.
4.2.4 opaque ring — an area of a certain width,
adjacent to the periphery of the desired exposure area
on a reticle, located in the non-exposure area of the
reticle to obtain a dark portion required in a wafer
lithography process.
4.2.5 single-layer halftone phase shift mask —
halftone phase shift mask having a thin film of uniform
material composition to give a certain phase difference
and transmittance.
4.3 Terms for Description of Optic al Characteristics
4.3.1 glass side reflectivity — a ratio of intensity of
reflected light to intensity of incident light into the glass
side that is the backside of the shifter film. The
intensity of incident light is usually calculated by the
intensity of reflected light measured using a reference
mirror. (Figure 1 illustrates the glass side reflectivity.)
Figure 1
Glass Side Reflectivity