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SEMI P43-0304 © SEMI 2004 2 SEMI Compilation of Terms 4.2 ISO Standar ds 2 International Vocabulary o f Basic and Ge neral Terms in Metrol ogy 4.3 Other St andards International Techno logy Roadmap for Semiconductors (IT…

SEMI P43-0304 © SEMI 2004 1

SEMI P43-0304

PHOTOMASK QUALIFICATION TERMINOLOGY

This terminology was technically approved by the Global Micropatterning Committee and is the direct

responsibility of the European Micropatterning Committee. Current edition approved by the European

Regional Standards Committee on January 9, 2004. Initially available at www.semi.org February 2004; to be

published March 2004. This document replaces SEMI PR7-0302 in its entirety.

1 Purpose

1.1 This standard defines a unique language in the field

of specification for, and qualification of, photomasks

for use in optical lithography within the semiconductor

industry.

2 Scope

2.1 At present only the International Technology

Roadmap for Semiconductors (ITRS) serves as a

universally accepted working document on how to

specify photomasks, however the definitions used are

subject to interpretation. Different tool makers, mask

makers and mask users are hindered in the

communication with each other, as they first need to

know and understand each others terminology. The

lack of a common terminology complicates comparison

of tools. A uniformly used, and universally accepted

terminology, with a minimum of ambiguity, is required.

2.2 The definitions listed are for mask qualification,

incorporating 3 possible types of value for a given

qualification parameter:

• <(true) qualification parameter>, which would be

the result of an ideal measurement of the total

population of features of interest

• <measured qualification parameter>, the result of

a given population of measurements. It is hereby

mentioned that a measured value (for example the

mean, the standard deviation, the range) is always

subject to the sample size of the measured

population and the measurement method.

Therefore both the sample size and the

measurement method are mandatory information.

• <qualification parameter spec(ification)>, the

maximum or minimum value that may not be

exceeded for the selected population of

measurements which must be defined as mandatory

information.

2.2.1 The first two types of value for a given

parameter, the true and measured qualification

parameters, will be defined in the present document.

1 See reference document in Section 4.2.

2.2.2 The third parameter type, the parameter

specification, will not be discussed here, since it is

subject to the agreement between the individual parties

of the mask qualification process.

2.3 In order to assist users, the major differences in

recommended default values between this standard and

the ITRS mask table definitions are noted where

applicable.

NOTICE: This standard does not purport to address

safety issues, if any, associated with its use. It is the

responsibility of the users of this standard to establish

appropriate safety and health practices and determine

the applicability of regulatory or other limitations prior

to use.

3 Limitations

3.1 This document is restricted to dimensional

metrology aspects. Other conventional mask

qualification aspects, including those related to

materials, overlay and defectivity, are not considered

within the scope of this version.

3.2 The definitions listed are specific to state-of-the-art

photomasks, with a focus on reduction reticles. They

may therefore overrule any related terminology in other

standards, with a more general scope. Application to

other types of masks, e.g., for next generation

lithography, may be feasible, but is not within the scope

of the present document.

4 Referenced Standards

4.1 SEMI Standards

SEMI P10 — Specification of Data Structures for

Photomask Orders

SEMI P19 — Specification for Metrology Pattern Cells

for Integrated Circuit Manufacture

SEMI P21 — Guidelines for Precision and Accuracy

Expression For Mask Writing Equipment

SEMI P22 — Guideline for Photomask Defect

Classification and Size Definition

SEMI P24 — CD Metrology Procedures

SEMI P35 — Terminology for Microlithography

Metrology

SEMI P43-0304 © SEMI 2004 2

SEMI Compilation of Terms

4.2 ISO Standards

International Vocabulary of Basic and General Terms

in Metrology

4.3 Other Standards

International Technology Roadmap for Semiconductors

(ITRS)

NOTICE: Unless otherwise indicated, all documents

cited shall be the latest published versions.

5 Interpretation of Related General

Terminology

NOTE 1: This paragraph includes general terms, as a basis

for the specific mask related terminology, which is the main

subject of this document.

5.1 feature — as defined in SEMI P35.

5.2 proximity range — distance over which a feature

influences another significantly (criterion to be stated).

This term applies to mask fabrication, mask metrology

and/or printed wafer image, defining 3 types of

proximity range (for example mask fabrication

proximity range). It is mandatory to state which of the

3 types is referred to.

NOTE 2: Within this document proximity range will refer by

DEFAULT to the first type mentioned.

5.3 line — a clear field, dark feature of quasi-infinite

length (>> proximity range) determined by its width. A

line is an example of a 1D feature (see Figure 1).

5.4 space — in analogy to line, but a clear feature in a

dark field (see Figure 1).

5.5 contact — a clear feature in a dark field with

length:width ratio ranging from 0.5 (1 is default) to 2

maximum (see Figure 1). The width of such feature

may be measured as if it were a 1D feature, but for

enhanced relevance it requires 2D assessment such as

an area measurement. A large contact can be called a

window.

5.6 dot — in analogy to contact, but a dark feature in a

clear field (see Figure 1). A large dot can be called a

pad.

5.7 isolated feature — feature that has no neighbors

that are within a distance smaller than the proximity

range to any edge of the feature.

2 International Organization for Standardization 1, rue de Varembé

Case Postale 56 CH-1211 Genève 20 Switzerland

3 International Technology Roadmap for Semiconductors, organized

by International SEMATECH, 2706 Montopolis Drive, Austin, Texas

78741, see itrs.org

line space dots contacts

Figure 1

Nomenclature for Feature Types (as Designed)

Default contact (dot) is square.

5.8 dense features — features that influence each other

(i.e., features that are not isolated). Clarification is

required to describe the proximity, either by detailing

the feature pitch and number of lines, for regular arrays

(pitch = design values of line width and space width

added), or by describing the surrounding area (see

Section 7). In absence of such clarification dense is

regarded by default as equal lines and spaces in a semi-

infinite array size, insofar that the feature width does

not exceed the proximity range.

5.9 nominal feature — feature as it is

intended. This

usually corresponds to the data used for mask making,

including any pre-compensation to overcome process

biases of the wafer process (e.g., subresolution features

such as hammerheads and serifs), but excluding any

pre-compensation that is purely done to deal with mask

process limitations (e.g., chrome etch bias). In the

simplest case it corresponds to the original design itself.

5.10 actual feature — feature as it is on the mask. In

practical cases this will include deviations in feature

widths, lengths, shape and position from the nominal

feature.

NOTE 3: A feature, whether actual or nominal, may contain

holes, as shown in Figure 2.

Figure 2

Example of Features Containing Holes

(left: nominal; right: actual)

5.11 pattern — subset of a layout containing one or

more features.

NOTE 4: It is possible that some features are only included in

part, see clipped feature.

5.12 region of interest (ROI) — circumscribed section

of a pattern that contains (parts of) the features

considered for measurement.

NOTE 5: It is recommended to make the ROI as small as

possible without affecting the obtained result.

5.13 clipped (nominal/actual) feature — the part of the

(nominal/actual) feature lying within the region of

interest (Figure 7).

5.14 feature (or Pattern) alignment — positioning of

nominal and actual feature (or pattern) relative to each-

other (see Section 8.4).

6 Coordinate System

6.1 The coordinate system XYZ for this document is

defined in Figure 3. It is defined with patterned mask

side upwards and mask orientation as it was patterned.

XY determines the mask plane. Z is the direction

perpendicular to it. z = 0 at the absorber–substrate

interface and z < 0 to the substrate side. Absorber is for

example chrome or embedded material. (x,y) = (0,0) is

tool or application specific.

Figure 3

Mask Coordinate System

6.2 Features are called vertical when their length is

along Y. Feature width is then measured in X. This

corresponds to Figure 2 of SEMI P35. Horizontal

features have their length along X. Feature width is

then measured in Y. See Figure 4.

vertical

horizontal

other angle

Figure 4

Orientation of Mask Features

7 1D Mask Qualification Terminology

7.1 feature width — width of a cross section of a mask

feature at a certain height defined by an appropriate

bounding box model as described in SEMI P35 (see

Figure 5). The bounding box model must be stated as

mandatory information, as well as the z height of the

measurement. DEFAULT is at z = 0.

width

height

Figure 5

Cross Section of a Mask Feature

7.2 measured feature width — width determined from

the measured signal obtained on the mask feature. For

example, the width may be determined at a certain level

of the measured signal. To be stated as mandatory

information:

• region of interest. For 1D features this corresponds

to the specified line segment (SEMI P35),

• measurement method used (SEM, optical

reflection, optical transmission, AFM, etc.),

• calibration and/or correlation used,

• precision (SEMI P24),

and as optional information:

• measurement tool (vendor, model or any tool

specific options), and

• measurement algorithm used.

NOTE 6: The bounding box could be infinitely short as in the

special situation of a measurement of a feature using a cross-

section.

7.3 feature width deviation (from target) — difference

between actual and nominal feature width.

7.4 measured feature width deviation (from target) —

difference between measured and nominal feature

width.

7.5 feature edge — position of the material boundary

of a mask feature at a certain height of the physical

cross section (see Figure 2 of SEMI P35), to be stated

as mandatory information. DEFAULT is

feature/substrate interface.