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SEMI E30.5-0302 © SEMI 2001, 2002 31 Table R1-1 A LIGN-DEF-LIST Align-Name Coordx Coordy Coordsys Align- Attri bute(n) Coarse1 -60000 -200 M20P Fine1 -60020 -205 M20P Coarse 2 60000 200 M20P Fine2 59980 195 M20P R1-4.3 A…

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SEMI E30.5-0302 © SEMI 2001, 2002 30
metrology equipment from the host can be desirable. In
some cases, the amount of information required to
define measurement site locations is less if a
pattern-element-based format is used. MSEM defines a
means to do this in this section, if desired, based on
SEMI standard SEMI M21.
R1-3.1 SEMI standard SEMI M21, “Specification for
assigning addresses to rectangular elements in a
Cartesian array”, is limited (for MSEM purposes) by
the fact that nothing is specified about how the
rectangular elements are located on the wafer. The
SEMI M21 standard details how to assign “addresses”
to elements and how to find the “array center” element.
In this section, MSEM defines how these elements are
located on a wafer, using the data item named
“M21Data”, and how to establish within-element
coordinate systems.
R1-3.2 There are users who want or require much more
layout information than is provided for by SEMI M21,
such as within-element structure details or element
attribute information. This additional layout
information is beyond the scope of MSEM, since it is
considered to be information which only is needed to
aid operator-interactive use of metrology systems.
R1-3.3 MSEM “M21” Layout
The first pattern
element layout issue to be addressed is that of
determining which SEMI M21 elements are to be
included in the MSEM “M21” layout. MSEM defines
the “M21” layout to include all elements which either
wholly or partially are within the circumference of the
wafer. Thus the MSEM “M21” element layout does not
correspond to the pattern layout exactly, since some
“M21” elements may not contain patterns.
R1-3.4 The second layout issue is that of how best to
specify the element locations on the wafer. The MSEM
approach is to specify the “M20P” coordinate for the
lower left corner of the minimum number of elements
needed to define the layout, along with the element
addresses. For a non-tiled layout, the location of a
single element is sufficient to establish the “M21”
layout. For tiled layouts, the location of one element in
each row or column is required. Note that the location
of the lower left corner of an element may be outside
the circumference of the wafer.
R1-3.5 Layout definition is supported only for
host-to-equipment communications. The user is
responsible for ensuring that the element addresses
provided to the equipment agree with the SEMI M21
specification. The equipment need not check this, other
than to ensure that there are not conflicts within the
provided layout, and shall report results with element
addresses as provided by the user.
R1-3.6 M21 layouts are established within the “M20P”
coordinate system, and need not require any additional
alignment site data than is needed to establish the
“M20P” coordinate system. However, as with “M20P”,
additional alignment may be necessary because of
errors in either the pattern layout or the equipment's
ability to locate features. OFFSET shall be used to
report the location corrections that result from any
within-element alignments.
R1-3.7 MSEM provides a means for element-based
coordinate systems, if required. This capability is
provided by the option of specifying “M21” as the
coordinate system for ALIGN-DEF-DATA and
SITEDEFDATA items. For element-based site
locations, MSEM requires that SEMI M21 element
coordinate systems have x and y axes parallel to the
respective M20-based coordinate system axes, with
their origins at the lower left corner of each element.
R1-4 An Example of How an M20P Coordinate System
is Established on a Silicon Wafer
R1-4.1 The following example is fairly basic. For this
example, the equipment does M20P alignment via a
repeated two-step process. The first step is done at a
low resolution, the second at a high resolution, and the
process is done at two positions on the wafer.
R1-4.2 The equipment documentation states that 4
alignment sites are required. These are defined to the
equipment via the table type named ALIGN-DEF-
LIST, as detailed below. The order of the sites in
ALIGN-DEF-LIST is not important. The sites are then
selected via the CPNAME item named
CP-ALIGNLIST, which is included in the PP-SELECT
command. The order of the sites listed in
CP-ALIGNLIST is important, and is as specified in the
equipment's documentation. The first site is the
alignment site for the first low resolution site, the
second item is for the first high resolution site, the third
item is the second low resolution site, and the fourth is
the second high resolution site.
SEMI E30.5-0302 © SEMI 2001, 200231
Table R1-1 ALIGN-DEF-LIST
Align-Name Coordx Coordy Coordsys Align- Attribute(n)
Coarse1 -60000 -200 M20P
Fine1 -60020 -205 M20P
Coarse 2 60000 200 M20P
Fine2 59980 195 M20P
R1-4.3 ALIGN-DEF-LIST
L,4
1. <Coarse1>
2. <Fine1>
3. <Coarse 2>
4. <Fine2>
R1-4.4 Using this information, the equipment will go to the nominal M20 location for Coarse, then “find” where it
actually is. The offset between the nominal M20 location and the actual M20 location is then used to “find” Fine1.
The actual M20 location of Fine1 is saved. The process is then repeated for Coarse 2 and Fine2. The equipment can
now determine the M20 to M20P offset from the nominal and actual coordinates.
First, a summary of the data:
xN1=-60020 yN1=-205 Nominal x and y data for the first fine site
xA1=-59800 yA1=-150 Actual x and y data for the first fine site
xN2= 59980 yN2= 195 Nominal x and y data for the second fine site
xA2= 60060 yA2= 175 Actual x and y data for the second fine site
R1-4.5 The equipment first calculates THETA ( Θ ), using, for example, the formula:
+
−
=Θ
−
MNMA
MNMA
1
tan
1
where MA and MN are, respectively, the slopes of the lines connecting the nominal and actual fine sites, in M20
coordinates, calculated as follows:
MA
yA yA
xA xA
MN
yN yN
xN xN
=
−
−
=
−
−
21
21
21
21
R1-4.6 The equipment then calculates DELTAX and DELTAY, using, for example, the formulas:
DELTAX
CD
=
+
+
sin ( ) cos ( )
(sin ( )) (cos ( ))
ΘΘ
ΘΘ
22
DELTAY
CD
=
−
+
sin ( ) cos ( )
(sin ( )) (cos ( ))
ΘΘ
ΘΘ
22
SEMI E30.5-0302 © SEMI 2001, 2002 32
Where C and D are the adjusted site 1 coordinates in a rotation-adjusted coordinate system calculated, for example,
using the formulas:
C = yA1 - ((xN1 sin Θ) + ((yN1 cos Θ)
D = xA1 - ((xN1 cos Θ) - ((yN1 sin Θ)
R1-4.7 The equipment can also calculate a SCALEFACTOR term to indicate the relative difference between the
length of the vector connecting the nominal alignment sites and the length of the vector connecting the actual
alignment sites. This can be used, for example, to judge whether there is a problem with the alignment process,
since the difference between these two vectors should be small.
SCALEFACTOR
VA
V
N
=
where VA and VN are the length of the vectors connecting the actual and nominal alignment sites, calculated using
the formulas:
()()
VN yN yN xN xN=−+−
21
2
21
2
()()
VA yA yA xA xA=−+−
21
2
21
2