FBMS - Royal Institute of Technology

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Transcript FBMS - Royal Institute of Technology

Fixed Beam Moving Stage
using a stitching free exposure strategy
contents
What is FBMS and how does it work?
How do I create structures for this exposure mode?
How do I expose?
results and applications
FBMS
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What is FBMS and how does it work?
stage travels at constant speed along (curved) paths of any length
and shape with stationary beam
 avoids stitch field boundaries
FBMS
 effective for extended paths
A. Spot Mode = FBMS line
Stage propagating direction
B. Shape Mode = FBMS area
constant
dose
Stage propagating direction
circle
symmetric
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What is FBMS and how does it work?
current value
(measured by
laserinterferometer)
FBMS
ideal value
(starting
point, end
point, speed)
comparison of
current value
and ideal value
no
yes
difference?
correction
signal to
column
continue
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What is FBMS and how does it work?
technical note:
difference between mechanical motion and ideal path
compensated by additional beam deflection
(special motor control unit)
Layout
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What is FBMS and how does it work?
dose is defined as charge per area:
electrons=charge
calculation width
=design width
FBMS
speed
FBMS area dose=
beam current
stage speed * calculation width
FBMS single pixel lines use the following definition:
FBMS line dose=
beam current
stage speed
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How do I create FBMS structures?
GDSII has to contain
special
FBMS
FBMS-elements
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How do I create FBMS structures?
FBMS structure
is defined by
nodes and their
coordinates
FBMS
comparable to
standard GDSIIelements: dose
factors, structure
widths and
layers can be
defined
width definition
determines if
FBMS element
will be exposed
as area or line
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How do I create FBMS structures?
FBMS
standard
GDSII area
layer selection for converted element
FBMS elements can be converted from standard GDSII designs
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How do I create FBMS structures?
Example: Optical Waveguides
FBMS
element
<dose> <layer> <width>
type: start
coordinates
type: line
curvature
type: arc
next
element
 See Software Reference Manual for additional information!
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How do I expose?
 FBMS-Alignment necessary
→ as motorcontrol creates a correction signal in order to correct
stage inaccuracies, the deflection signal has to be calibrated
(comparable to align writefield procedure)
FBMS
 Scan Manager offers special procedures
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How do I expose?
 press „preset“ button to get same values as for align writefield
as starting values
 FBMS-Alignment works the same way as the writefield alignment:
stage moves to corners of the writefield
FBMS
beam is deflected to the same corner to scan an image:
deflection is not adressed by pattern generator but by motor
control
image shift from ideal position is determined
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FBMS
How do I expose?
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How do I expose?
 after FBMS alignment procedure correction values are determined
→ as motorcontrol can only correct zoom and rotation these
correction values are written into Align FBMS window
FBMS
→shift correction is written into Align writefield window as pattern
generator directly applies this shift
 FBMS alignment parameters are not stored in an ini file
shift
zoom & rotation
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FBMS
How do I expose?
FBMS elements have to be selected in
the exposure window (comparable to
selection of SPLs or dots)
only if FBMS elements are selected the
referring tab for the parameter
calculation will be visible
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FBMS
How do I expose?
value
which
has
been
read
infor
clearing
dose
for
the
referring
assumed
structure
width
speed
calculate
necessary
stage
speed
(has to
by „current“
window
structure
(has to be
typed
in)
calculation
in
„details“)
be calculated
by(determined
pressing
button)
(automatically written)
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FBMS
How do I expose?
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How do I expose?
tab for FBMS area exposure
FBMS
→ beam makes circular
deflection to create
designed structure width
effective stepsize for circular
beam deflection
•calculation width necessary for stage speed calculation
perpendicular to stage
→software calculates basic speed
movement
•during exposure calculation width is adapted
design
usertocan
workwidth
with and
speed is recalculated so that dose is kept constant
comparable values as for
standard GDSII areas
calculationwidth=
of maximum
writable
calculation
minimum
designstructure
width: width (only 3400 points
within circular deflection possible)→ restriction
basic speed is maximum possible speed for this pattern
calculation of deflection cycle time
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width should fit to design but
will be adapted anyway
application examples
former results with conventional stitching
stitching error < 20 nm
FBMS
< 8 nm
Line width
Pitch
19
= 30 nm
= 100 nm
application examples
FBMS
new results with FBMS
• no stitching errors!
• no settling time from stitching!
Line width
Pitch
20
= 20 nm
= 50 nm
FBMS applications in general
typical FBMS applications are extended (curved) paths
 with a length several mm or cm
FBMS
 with a fixed width in the range of 20 nm to 20 µm
 where stitching errors are crucial for the
performance of the device
 where a large number of stitching borders would
result in long exposure times
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