High-speed one-dimensional spatial light modulator for Laser Direct
Imaging and other patterning applications
Jan-Uwe Schmidt1a, Ulrike A. Dauderstaedta, Peter Duerra, Martin Friedrichsa, Thomas Hughesa,
Thomas Ludewiga, Dirk Rudloffa, Tino Schwatena, Daniela Trenklera, Michael Wagnera,
Ingo Wullingera, Andreas Bergstromb, Peter Bjornangenb, Fredrik Jonssonb, Tord Karlinb,
Peter Ronnholmb, Torbjorn Sandstromb
a
Fraunhofer Institute for Photonic Microsystems (IPMS), Maria-Reiche-Str. 2, D-01109 Dresden,
Germany; bMicronic Mydata AB, Nytorpsvagen 9, SE-18303 Taby, Sweden
ABSTRACT
Fraunhofer IPMS has developed a one-dimensional high-speed spatial light modulator in cooperation with Micronic
Mydata AB. This SLM is the core element of the Swedish company’s new LDI 5sp series of Laser-Direct-Imaging
systems optimized for processing of advanced substrates for semiconductor packaging. This paper reports on design,
technology, characterization and application results of the new SLM. With a resolution of 8192 pixels that can be
modulated in the MHz range and the capability to generate intensity gray-levels instantly without time multiplexing, the
SLM is applicable also in many other fields, wherever modulation of ultraviolet light needs to be combined with high
throughput and high precision.
Keywords: Laser Direct Imaging (LDI), Printed Circuit Boards (PCB), Spatial Light Modulator (SLM), Micro Mirror
Array (MMA), gray-scale lithography, semiconductor packaging, semi-additive processing, substrate
1
1.1
INTRODUCTION
Laser direct imaging for advanced substrates in semiconductor packaging
Modern electronics packaging increasingly utilizes high-end forms of printed circuit boards called ‘substrates’ and
‘interposers’. The first provide a mechanical support and an electrical interface between integrated circuits and the
outside world, the latter act as an intermediate layer used for interconnection routing and as a ground/power plane.
Advanced packages require substrates with a high density of interconnects with minimum interconnect line widths and
spaces of about 10 µm, in few years even less. Such high density substrates are processed in form of large panels (e.g.
510 mm x 515 mm). To form the interconnect layers, the ‘semi-additive metallization’ process [1] is used (Figure 1): On
a copper seed layer, a layer of dry film resist (DFR) is laminated (1). Next, the whole panel is exposed by ultraviolet
(UV) light (2), in order to enable patterning of the DFR (3). The spaces in the patterned DFR act as template for the
deposition of copper by electroplating (4). The removal of DFR (5) is followed by a flash etch to remove the Cu seed
layer (6). As feature size decreases, several wiring layers and their vertical connections (vias) have to be aligned within
smaller tolerances to avoid functional errors. Compared to mask-based steppers an exposure by Laser Direct Imaging
(LDI) offers higher flexibility. LDI techniques utilize a programmable micromechanical element, a so-called ‘spatial
light modulator’ (SLM) to print dose-patterns into the resist and have the potential to combine high resolution, high
precision of alignment and high throughput. Small variations in the pitch of existing structures induced by strain in the
substrates can be measured for each panel and compensated by appropriate algorithms, such that new layers perfectly
match the preceding ones. Micronic Mydata AB has developed a novel LDI5sp laser direct imaging system optimized
for this field of application. As a cooperation partner, Fraunhofer IPMS contributed to this system a novel fast onedimensional diffractive spatial light modulator (SLM), which shall be discussed in the present article.
1 Corresponding author: jan-uwe.schmidt@ipms.fraunhofer.de; phone ++49-351-8823-119; fax ++49-351-8823-266;
www.ipms.fraunhofer.de
MOEMS and Miniaturized Systems XIII, edited by Wibool Piyawattanametha,
Yong-Hwa Park, Proc. of SPIE Vol. 8977, 89770O · © 2014 SPIE
CCC code: 0277-786X/14/$18 · doi: 10.1117/12.2036533
Proc. of SPIE Vol. 8977 89770O-1
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Dry Film Re
(DFR)
IND
Cu seed lays
Substrate
2
Laminate 1)1FR
3
Expose /FR (by LDI)
Pattern DFR
al SI
1
4
5
1=.lectruplmc
je DFR
6
Retmove Cu seed lay
Figure 1: Schem
matic of semi-aadditive metalliization process
(SAP) using a negative tone resist.
r
1.2
Fiigure 2: Micronnic Mydata LDII 5sp system
fractive intenssity modulatiion by meanss of programm
mable micro mirror arrayys
Diffr
To motivate the selected SLM design,, the principlee of diffractiv
ve intensity modulation
m
ussing micro-miirror arrays iss
briefly summ
marized. Due to the regular grid of mirrorrs, any micro mirror array (MMA)
(
acts aas an optical grating.
g
Whilee
the location of
o the 0th diffrraction order in
i space is dettermined by th
he angle of inncidence only,, the positionss of the higherr
orders also deepend on pitchh of micro mirrrors, and the optical wavellength [2]. Deetermined by interference, th
he fractions of
intensity reflected into thee different orrders of the grating
g
depend
d on the phasse relationshipp between reflected partiaal
ng a MMA of
waves. They can be moduulated by channging the defleection state of micro mirroors: a light waave approachin
b reflected sppecularly, i.e. all reflected intensity willl be in the 0th order (assum
ming negligiblee
un-deflected mirrors will be
mall piston or tilt deflection
ns of micro miirrors modify the phase of light
l
such, thaat
slits and ideallly flat mirrorrs). Already sm
intensity is paartly redirecteed into the higgher diffractioon orders. Thee intensity in the 0th order approaches zeero for certainn
deflection connditions [3].
Based on thiss effect, MMA
As can be utillized to moduulate the inten
nsity of cohereent monochroomatic or narrrow-band lighht
sources. For this purpose the light refflected by thee MMA is co
ollected by ann imaging syystem, that alllows only thee
intensity in the
t 0th diffracction order (oor another sinngle diffractio
on order) to contribute
c
to tthe image, while
w
the otherr
diffraction orrders are bloccked, e.g. by placing
p
an apperture of suittable dimensions in the Foourier plane of
o the imagingg
system. In ann image geneerated this waay, regions with
w un-deflectted mirrors will
w appear brright, whereass regions withh
deflected mirrrors will appeear gray or eveen black, depeending on the mirror deflecttion.
The illustrateed concept foor diffractive intensity is most
m
frequentlly used with MMA devicees that allow for an analogg
deflection off mirrors (“annalog” MMA)) [4][5][6][7], because a co
ontinuously controlled
c
mirrror deflection
n is convertedd
instantly into gray-scale inntensity levels.. The describeed technique allows
a
to use analog
a
MMAss as high-speeed spatial lighht
modulators for
fo the generaation of monoochrome gray--scale patterns. This motivvated the com
mmercial appliication of twoo
dimensional analog
a
MMAss in semicondductor mask writers
w
[3][7][8
8].
2
SLM DESIGN
The active areea of the one--dimensional (1D)
(
modulatoor is formed by
b an array of electrostaticaally addressed micro mirrorss
capable of annalog tilt deflection.
Figure 3 shoows a top-view
w scanning electron
e
microoscopy (SEM
M) image of mirrors
m
in the optically acttive area. Thee
manually addded colors highhlight rows off identically adddressed and synchronouslyy tilting mirroors. Each of th
he 8192 mirrorr
rows acts as one
o “optical pixel”
p
of the SLM.
S
The SL
LM contains no integrated active
a
driver eelectronics: an
n external dataa
path unit provvides the requuired data andd auxiliary pootentials directtly to the SLM
M. Figure 4 shhows a cross--section of thee
same structurre. The three top structural layers
l
(mirrorr, yoke, interco
onnect 2) can be seen.
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/;,
Sena
WD 8.2mm
Figure 3: SEM
M image of tilt mirrors.
m
Colors indicate
i
mirrorss
belonging to saame pixel.
'
MAXI IND
Fiigure 4: SEM crross-sectional im
mage of tilt mirrrors after
removal of sacrifficial layer.
Figure 5 show
ws the fully processed
p
SLM
M to illustratee its layout. Th
he approximaate chip dimennsions are 15 mm
m x 88 mm
m.
Bond pads arre arranged inn 4 rows to booth sides of thhe SLM (1). In
I the electrodde fan out reggion (2) data--electrodes aree
routed to the pixel area (3) comprising 2.2
2 million mirrrors grouped to 8192 “optiical pixels” (44).
The pixel area has approxim
mate dimensioons of 4 mm x 82 mm.
This design was
w preferredd for several reasons:
r
all opptical pixels can
c be updateed in parallel at a modulatiion rate in thee
MHz range liimited only byy the fundameental resonance of the micro
o mirror tilt-m
movement. Thiis enables high
hly productivee
continuous exxposure proceesses and alloows an efficieent utilization
n of quasi-conntinuous, i.e. M
MHz-repetitio
on rate pulsedd
ultra-violet laasers. Since a higher repetittion rate of thhe laser also im
mplies a lower energy per llaser pulse and hence lowerr
mirror temperratures, the deesign also helpps to minimize laser induceed degradationn of mirrors.
Building the “optical pixels” of the 1D
D-SLM from sets
s of small identically
i
adddressed microo mirrors allo
ows to reach a
high fundam
mental resonannce of micro mirrors, but also allows to increase the
t total areaa per optical pixel withouut
sacrificing modulation
m
speeed. This agaiin helps to reeduce power density
d
at thee SLM and thhe temperaturee of the laserexposed micrro mirrors annd contributes to a long SLM
S
lifetimee [10]. The SLM
S
design without integ
grated addresss
electronics reeduces the com
mplexity of SL
LM processinng, SLM cost and processinng time, and inncreases yield
d. Upgrades of
the control electronics
e
haave no impaact on SLM technology and
a
can be implemented
i
whenever more
m
powerfuul
components become
b
availaable at acceptaable cost.
Figure 6 shoows a single actuator electrostatically addressed
a
viaa global voltaage electrodess (1) and (2) and the dataa
electrode (3). The global ellectrodes (1) and
a (2) proceeed in vertical direction
d
and supply the coommon counteer potentials too
all pixels. Thhe electrodes (1),
( (2), and (33) are formed from intercon
nnect layer 2. Within one ooptical pixel, the
t segmentedd
data electrodees (3) of all micro
m
mirrors are connectedd by vias to th
he same data line.
l
The latter proceeds peerpendicular too
the global eleectrodes in thee hidden intercconnect layer 1.
Since actuatoors in even andd odd rows arre offset by haalf the width of
o an actuator,, the positive gglobal electro
ode (1) and thee
negative globbal electrode (2)
( change siddes within thee actuator celll for even andd odd pixels rrespectively. This
T results inn
reversal of tillt directions for
f even and odd
o pixels asssuming the sam
me sign of daata voltage appplied to the data
d electrodess
(3) of the neigghboring pixeels.
The yoke strructure (4) is supported byy two posts reesting on the data electrodde. It is tiltedd depending on
o the voltagee
difference beetween data annd global elecctrodes (arrow
ws in Figure 6). The restorinng force is deefined by the narrow springg
region (5) of the yoke struccture. A post (6)
( resting on the yoke supp
ports the mirroor (7).
Separate structural layers for
f mirror andd springs allow
w optimizing mechanical and
a optical chharacteristics independently
i
y.
By use of a loow-creep hingge material, hyysteresis effeccts are eliminaated and the mirror
m
can be optimized forr the operatingg
wavelength.
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Figure 5: Photoograph of the diced chip with removed
r
sacrifi
ficial layers. Maarkers indicate bondpad
b
regionn (1), electrode fan-out
f
region
(2), and active pixel area (3). The dotted linee (4) shows the orientation of a single optical pixel.
agonal minor
ó 0 0 ó
tangular /square rt
-
o
I
o
o
xeiauve mten5tty
00
LG
0óóó0
Applying thee variable dataa potential to the
t yoke/mirrror electrode (3)
( reduces thee required datta voltage ran
nge by a factorr
of two comppared to the alternative
a
option of addreessing electrod
de (1) while keeping electtrodes (2) and (3) at fixedd
reference pottential. Reduccing the data voltage rangee lowers the cost of electrronic componnents for the data path andd
allows for a higher
h
speed.
For this specific SLM, a hexagonal
h
mirrror plate has been used to optimize the modulation ccharacteristicss. To illustratee
h
andd
the effect off mirror shappe, Figure 7 shows simullated modulattion characterristics for (iddeally flat) hexagonal
rectangular mirrors
m
at a wavelength
w
of 355 nm. Plottting the inten
nsity in the 0thh order vs. tip deflection off a mirror, thee
side lobe nexxt to the first intensity minnimum is cleaarly less pron
nounced for thhe hexagonal mirror shapee compared too
rectangular or square mirroors with rotation axis paralllel to the sidees. On the othher hand, the ddeflection req
quired to reachh
the first intennsity minimum
m is slightly hiigher for hexaagonal mirrorss (for the chossen design aboout 110 nm att a wavelengthh
of 355 nm).
Due to the faact that the slitts are very naarrow and the mirror post iss completely hidden
h
undernneath the mirrror (Figure 3)),
the optical fiill factor of thhe pixel area is very high,, about 90 %. Scattering loosses are therreby reduced, while opticaal
efficiency andd achievable contrast
c
are inncreased. A suummary of parrameters of the new SLM iss given in Tab
ble 1.
50
100
150
Tip defiedfion of mirror [i
Figure 6: Schem
matic of single tilting mirror.
Fiigure 7: Intensitty modulation ccharacteristics for
f hexagonal
an
nd rectangular/ssquare mirrors.
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3
S
SLM
WAFER
R PROCESSIING AND AS
SSEMBLY
The SLM hass been fabricaated in the ME
EMS pilot fabrrication line of
o Fraunhofer IPMS, based on a technolo
ogy developedd
for the monoolithic integraation of anallog MMAs on
o CMOS in a “MEMS-last” technoloogy-scheme using
u
SiO2 ass
sacrificial layyer. Figure 8 schematically
s
illustrates thee main steps of the process flow
f
using a ccross-section of
o the actuatorr
(Figure 6) parrallel to the spprings and throough the two yoke posts.
Figure 8: Schem
matic processinng sequence of SLM
After growthh of an insulatting SiO2 film
m on the Si suubstrate, the first
f
interconnnect layer is ddeposited and patterned (1)).
The first interconnect layeer is covered with
w SiO2 inteerlayer-dielecttric (ILD) andd planarized. On top of thee ILD, an inerrt
barrier layer (2) is deposiited to protectt the underneeath SiO2 lay
yers against atttack of Hydrrogen Fluorid
de gas used too
finally removve SiO2 sacrificial layers. Vias down too interconnectt 1 are formedd, and intercoonnect layer 2 is depositedd,
patterned andd planarized. The
T first sacriificial SiO2 laayer is deposiited, vias for the
t hinge possts are etched and the hingee
metal is depoosited and pattterned (3). A second
s
sacrifiicial SiO2 lay
yer is depositedd and vias forr the mirror po
ost are etchedd.
The post material is deposiited such that it completelyy fills the post via (4). The post
p material iis removed an
nywhere, aparrt
from the region next to thee post (5). Thee wafer surface is planarized
d and the finaal thickness off the second saacrificial SiO22
ween mirror and
a stoppers (not shown in Figure 8) is defined.
d
At thhe same time the
t protrudingg
layer, i.e. thee distance betw
mirror post annd the sacrificcial layer are leveled.
l
Next,, the mirror is deposited andd patterned. T
The wafers aree then diced too
chips. The saacrificial SiO22 layers are reemoved by a Hydrogen
H
Flu
uoride gas-phaase etch, in orrder to releasee the actuatorss
(6). Figure 9 shows an im
mage of a com
mpleted product wafer just before dicingg. Figure 10 iss a differentiaal interferencee
contrast (DIC
C) microscopyy image of thhe boundary of
o the pixel area.
a
Individuaal pixels are just resolved,, to maximizee
sensitivity off DIC to pre-ddeflection of mirrors.
m
The im
mage illustrattes the extrem
mely uniform ddeflection of non-addressed
n
d
mirrors.
After the releease etch, the SLM chip is glued to a higghly planar ceeramic carrier,, which is thenn mounted to a metal platee.
A metal holder for a quartzz glass is mouunted to the ceeramic carrier. The quartz glass
g
window is fitted into the
t aperture of
the metal holdder to protect the SLM agaiinst particle-ccontamination during furtheer assembly annd use.
Next, metal carrier
c
plates for
f two multi-layer printedd circuit board
ds are mounted. These “Fann-In-Adapter”” boards (FIA))
are then mounnted to the carrrier plates, suuch that bond pads on SLM
M and FIAs aree aligned and leveled to eacch other. Bondd
pads on SLM
M and FIA boaards are connected by 4 layeers of fine-pitcched wire bonnds. Each FIA
A board holds connectors
c
forr
4096 data chhannels, the gllobal voltagess and test pottentials. Durin
ng a later use,, flexible ribbbon cables plu
ugged into thee
FIA connectoors establish thhe link to the digital-analog
d
g converter (D
DAC) boards of
o the data pathh unit controllling the SLM..
Figure 12 shoows the wire bonded
b
SLM--unit. The wirre bond protecction cap has been removedd to enable an
n unobstructedd
view on the SLM.
S
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Figure 9: Image of completed product wafer
Figure 10: DIC microscopy image of pixel area after
sacrificial layer etch. Minimal and homogeneous tilt of idle
mirrors.
Figure 11: Close-up onto the wire bonds on one side of the
SLM.
Figure 12: Close-up image of the assembled SLM unit
showing the wire bonds connecting SLM and FIA boards.
4
4.1
SLM CHARACTERIZATION
Fundamental resonance of mirror tilt movement
For a current spring design the resonance frequency has been measured at ambient pressure using a MSV-300
Microscope Scanning Vibrometer (Polytec) by modulating the data-voltage with a rectangular voltage function. The
resonance frequency has been determined to be higher than 1.3 MHz.
4.2
Planarity of chip within pixel area
An imperfect planarity of the SLM within the pixel area will lead to errors of the generated SLM image. The imaging
system and software of an LDI system may compensate or correct for certain errors of SLM shape: e.g. a cylindrical bow
of the MMA can be compensated by the imaging optics. Planarity specifications therefore have to be considered with
respect to the specific imaging system. The planarity within the large pixel area is measured using a Wyko® NT9800
optical profiler. Single measurements covering an area of 1.2 mm x 1.6 mm sampled with 4.7 µm resolution are stitched
together to cover the whole pixel area. Figure 13 shows a typical height map of the pixel area after subtraction of bow.
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i
Figure 13: Plannarity measurem
ment of pixel arrea.
4.3
Fiigure 14: Surfacce planarity of rreleased mirrors. RMS value
1.5±0.2nm
Mirrror planarityy
To obtain a sufficiently
s
hiigh contrast (hhere defined as ratio of “w
white” and “black” intensitty), the planarrity of mirrorss
must be kept within a narrrow range (less than about 7 nm surfacee RMS). Afterr removal of sacrificial lay
yers the mirrorr
planarity is measured
m
usingg a Wyko® NT8000
N
opticaal profiler. An
n exemplary teest using a conntrol sample of
o 10 test-sitess
on 3 arbitrariily chosen waffers (in total 2416
2
mirrors) resulted in a mean RMS of
o 1.5±0.2nm, which is well within target
range. Figuree 14 shows a representative height map off mirrors.
4.4
Defllection characcteristic
a0
>
o `111111U111
100
111111111111
e
1
A
5
80
v
';)
co E
co
.c
60
v
¡AI
? 40
9
T
J)
v
o
20
k
O
O
120
1111111111111111111111111111
N
Mirror tip - deflection Inml
01
O
A
o
Ó
o
o
o
Ñ
The deflectioon characteristtic of micro mirrors
m
is meassured using a Wyko® NT9800 optical prrofiler. For th
hat purpose thee
voltages of global electroddes (1 and 2 inn Figure 6) arre set to same absolute valuue but oppositte polarity forr all pixels. Too
deflect the mirrors,
m
the vooltage of the data-line
d
connnected to yok
ke/mirror and stoppers is varied. Figure 15 shows thee
resulting defllection responnse curve for different
d
valuees of global voltage used ass parameter. T
The target defflection for thee
“black state”,, 110 nm (accoording to Figuure 7) is reachhed at a globall voltage of 155.5 V and a daata voltage of about 14.5 V..
Figure 15: Mirrror tip-deflectioon vs. data voltage
12
14
80192
o
O
N
Data Pixels
7168
6144
5120
4096 3072
number
Data p)ixel
2'048
1024
Fiigure 16: Full-m
matrix deflectionn test. The MM
MA is addressedd
wiith a common bias
b for all pixels. Plot of mean
n deflection vs.
pixel number. Insset: Deflection map for all mirrrors (same dataa
seet).
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Table 1: Summary of SLM parameters.
LDI SLM Parameter
Value
Mirror material
Al-alloy
Chip dimensions [mm]
15 x 88
Operating wavelength [nm]
355
Dimensions of pixel area [mm]
4 x 82
Mirror reflectance at 355nm [%]
> 85
Fill grade of active area [%]
> 90
Max. mirror deflection [nm]
> 110
Number of pixels
8192
Pixel resonance frequency [MHz]
> 1.3
Mirrors per pixel
268
Achieved contrast
Mirror shape
4.5
hexagonal
Mirror RMS planarity [nm]
Up to 1000
<7
Deflection test of assembled SLM-unit
The functionality of the completely assembled and wire bonded SLM-units is verified by a deflection test using a
Wyko® NT9800 optical profiler. Herein the SLM unit is addressed through the FIA boards to include FIAs and wire
bonds in the test. All pixels are addressed with the same voltages to check for non-working pixels. The lateral resolution
for the interferometric measurement is chosen such that the deflection amplitude of each individual mirror can be
determined. The pixel area is covered by stitching a set of subsequent measurements.
Figure 16, a plot of mean pixel deflection vs. pixel number, illustrates a typical result. All pixels are functioning. Due to
design-related systematic differences in the routing of data electrodes, the observed deflection values vary slightly with
pixel number in a systematic way. Irregular features, like the one at pixel 3072, are attributed to small variations in hinge
width caused by small tolerances of lithography.
Before the SLM is finally used in a LDI system, the mentioned systematic effects are compensated by a calibration
procedure. After calibration for all individual pixels the voltages required to reach certain deflection values can be
retrieved from look-up tables.
A two-dimensional representation of the same data, i.e. a map of deflection for each individual mirror of the SLM (inset
in Figure 16) can be used to check for possible non-working mirrors and to retrieve their positions.
5
5.1
SLM PERFORMANCE IN LDI EXPOSURE SYSTEM
Description of exposure system
Figure 17 is a schematic of the LDI5sp system developed by Micronic Mydata AB. The coherent light source of the
exposure system is a high-power, 355 nm diode-pumped solid state laser. The SLM is illuminated by the rectangular
laser beam. Light reflected into the 0th diffraction order passes the aperture in the Fourier plane of the optical system,
while the higher diffraction orders of the SLM are blocked. Behind the lens system, the beam is reflected via a rotating
prism into one of four imaging arms rotating in synch with the prism before it is imaged onto the substrate.
During exposure the intensity modulated line focus is laterally scanned in an arc across the substrate panel, always
keeping the same orientation similar to a windscreen wiper. After it has passed the panel edge, the laser beam hits the
next facet of the prism and is directed into the next imaging arm to expose the next arc. Since at the same time the panel
is steadily moved, subsequently exposed arcs are seamlessly stitched together until the whole panel has been exposed.
To maximize throughput, the twin table system aligns the next panel already while the preceding panel is being exposed.
After exposure, the aligned panel is briefly flipped upwards to enable the passage and unloading of the already exposed
panel. The tool exposes dry film resist on substrate panels with dimensions up to 510 x 612 mm² at a resolution better
than 10 µm L/S.
The constant-speed operation of both rotor arms and panel stage contribute to a highly precise pattern placement. Feature
edges can be smoothly shifted laterally utilizing the gray-leveling capability of the presented SLM. An adjustment of
exposure dose is possible by tuning the speed of rotation for the imaging arms. Based on the high SLM modulation rate
and high optical efficiency of the SLM, a high write speed and efficient use of laser power are achieved.
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5.2
Exposure results
Examples of patterned substrates are shown to illustrate the successful utilization of the presented SLM in Micronic
Mydata’s LDI5sp Laser Direct Imaging systems. Figure 18 shows a 15 µm high dry film resist on a copper seed layer
patterned with 6 µm minimum line/space dimensions. Figure 19 shows a 25 µm high dry film resist on a copper seed
layer structured with a pattern typical for the routing of interconnects around a pad. The minimum line/space dimensions
in this image are 10 µm. Using the presented new SLM, contrast values (here defined as ratio of maximum and minimum
intensity at the exposed substrate) of up to 1000 have been measured.
LASER
PATTERN
RASTERRE
Real-time data path that enables
advanced pattern alignment
SLM
ALIGNMENT CAMERAS
Analog Spatial Light Modulation
(SLM) with high modulation
frequency
e
ROTOR
Twin -table stage system that
enables concurrent alignment
and exposure
Rotor -based optical system with
high scanning speed and low
overhead time
Figure 17: Schematic of Micronic Mydata’s LDI5sp system
AIN4Mk
Mi-My AB
2013 -06 -18
10:45 F
D14,9 x800
100 um
A
Figure 18: 15 um DFR on Cu seed layer, patterned with a
micro-VIA interconnect test pattern. Minimum line/space
feature size is 6 um.
Figure 19: 25 um DFR on Cu seed layer, patterned with a
structure typically used in the pad region of a substrate.
Minimum line/space feature size is 10 µm.
Proc. of SPIE Vol. 8977 89770O-9
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6
SUMMARY
Fraunhofer IPMS has developed a fast one-dimensional analog spatial light modulator (SLM) in collaboration with
Micronic Mydata AB. The SLM supports a pixel rate of >10 billion grayscale-pixels per second and handles tens of
Watt of laser power at a wavelength of 355 nm.
The SLM has successfully passed all performance tests and is now utilized in Micronic Mydata’s novel LDI5sp series of
Laser Direct Imaging systems optimized for the processing of advanced substrates for semiconductor packaging. A first
Micronic-Mydata LDI5sp tool equipped with the IPMS-SLM has reached acceptance status at a final customer.
7
ACKNOWLEDGEMENTS
The authors wish to acknowledge Per Askebjer and Jarek Luberek for their valuable contributions to this development.
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