A novel photosensitive silicone ladder polymer: Synthesis, photochemical, and thermal characteristics

Article abstract of DOI:10.1246/bcsj.74.991

A negative working photosensitive silicone ladder polymer (PVSQ) based on polyphenylsilsesquioxane with vinyl groups as a reactive substituents in the side chain, and 2,6-bis(azidobenzylidene)4-methylcyclohexanone (BA) as a photocrosslinker, has been developed. The monodisperse PVSQ was synthesized by co-polymerization of trichlorophenylsilane and trichloro(vinyl)silane with potassium hydroxide in isobutyl methyl ketone. The PVSQ film showed excellent transparency above 280 nm and high solubility in organic solvents. The photosensitive PVSQ containing 3 wt% of BA showed the sensitivity of 40 mJ cm^-2 when it was exposed to 365 nm light (i-line) followed by development with a mixture solution of anisole and xylene at 25 °C. The photosensitive PVSQ film also showed high thermal stability (decomposition temperature: 520 °C) and low dielectric constant (3.2/1 MHz), demonstrating a high potential for application to LSI production.

Full text of DOI:10.1246/bcsj.74.991

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© 2001 The Chemical Society of Japan
Bull. Chem. Soc. Jpn., 74, 991—996 (2001)
991
Chemical
iety of Ja-
Chemical
iety of Ja-
A Novel Photosensitive Silicone Ladder Polymer: Synthesis,
Photochemical, and Thermal Characteristics
Novel Photosensitive Silicone Ladder Polymer
N. Yasuda et al.
Naoki Yasuda,*, # Shigeyuki Yamamoto, Hiroshi Adachi, Suguru Nagae, Yuji Wada,† and
Shozo Yanagida†
01
Advanced Technology R&D Center, Mitsubishi Electric Corporation, Tsukaguchihonmachi, Amagasaki,
Hyogo 661-8661
SJA8
9-2673
59
†Material and Life Science, Graduate School of Engineering, Osaka University, Suita, Osaka 565-0877
(Received October 12, 2000)
ober
0
0
A negative working photosensitive silicone ladder polymer (PVSQ) based on polyphenylsilsesquioxane with vinyl
groups as a reactive substituents in the side chain, and 2,6-bis(azidobenzylidene)-4-methylcyclohexanone (BA) as a pho-
tocrosslinker, has been developed. The monodisperse PVSQ was synthesized by co-polymerization of trichlorophenylsi-
lane and trichloro(vinyl)silane with potassium hydroxide in isobutyl methyl ketone. The PVSQ film showed excellent
transparency above 280 nm and high solubility in organic solvents. The photosensitive PVSQ containing 3 wt% of BA
showed the sensitivity of 40 mJ cmꢀ2 when it was exposed to 365 nm light (i-line) followed by development with a mix-
ture solution of anisole and xylene at 25 ˚C. The photosensitive PVSQ film also showed high thermal stability (decom-
position temperature: 520 ˚C) and low dielectric constant (3.2/1 MHz), demonstrating a high potential for application to
LSI production.
7
4
Silicone ladder polymer (PPSQ; Polyphenylsilsesquioxane)
is an inorganic polymer with a ladder type structure consisting
of siloxane bonds as a main chain and phenyl groups as a side
chain.1–7 PPSQ has received considerable interest in the mi-
croelectronic industry due to its high thermal and chemical sta-
bility and low dielectric constant. We have developed a simple
and easy synthetic process of PPSQ with high purity, which is
useful in semiconductor manufacturing of insulators and di-
electrics.8–11 PPSQ soluble in solvents can be processed into
films without shrinkage and degasification during curing so
that it has been applied not only as a protection layer but also
as insulation layers in the multilayer writing method.12
On the other hand, polyimides are well-known as protection
layers and insulators in semiconductor manufacturing.13,14 In
particular, photosensitive polyimides are very useful, since the
number of processing steps is reduced by avoiding the use of
classical photoresists.15 However, being insoluble in most
common solvents, polyimides are usually processed in the
form of their precursors, poly(amic acid), which are then ther-
mally converted to the imide structure.16 Since polyimide pre-
cursors suffer from high shrinkage (ꢀ50%), which causes dis-
tortion to a substrate and enough degasification to contaminate
devices during thermal curing for imidization, it is quite diffi-
cult to apply polyimides to insulation layers in the multilayer
writing methods.
electronic fabrication can be reduced by eliminating the
photoresist. Polyimides and non-photosensitive PPSQ need
baking processes over 350 ˚C for making them insoluble in
common solvents. On the other hand, photosensitive PPSQ re-
quires no high thermal curing, so that it is also capable of be-
ing applied to the manufacture of devices sensitive to heat.
A strategy for the photosensitive PPSQ polymer with nega-
tive tone image at i-line (λ ꢁ 365 nm) is the introduction of re-
active groups into the side chain of PPSQ with the photoreac-
tive crosslinking reagent. We partially substituted phenyl
groups of PPSQ with vinyl groups as a reactive moiety (Fig. 1,
denoted as PVSQ). As PVSQ showed high transmittance in
the range of the wavelength of λ > 280nm, it didn’t have pho-
toreactivity at the i-line alone. We selected 2,6-bis(azidoben-
zylidene)-4-methylcyclohexanone (BA) having azide groups
on both ends as a photocrosslinker in this system. BA has high
absorption in the wavelength of i-line and often has been used
as a photocrosslinker of UV negative working photoresists.17–
18
Figure 2 shows the photocrosslinking reaction expected be-
tween the side chain groups of PVSQ and BA as a photo-
crosslinker. When BA is irradiated with i-line, the azide groups
If PPSQ structure can be supplied with photosensitive char-
acteristics, it will become much more attractive than photosen-
sitive polyimides, as the number of processing steps in micro-
# Material and Life Science, Graduate School of Engineering,
Osaka University.
Fig. 1.
Structure of PVSQ.

992 Bull. Chem. Soc. Jpn., 74, No. 5 (2001)
Novel Photosensitive Silicone Ladder Polymer
ductor Co.) were used for evaluating applicability for pattern fab-
rication. Film thickness was measured by a Dektak 3030 system
(Veeco Instrument Inc.). The patterning profiles were observed by
a JASCO Model JSM-T20 scanning electron microscope (SEM).
Preparation of Photosensitive PVSQ Varnish. The photo-
sensitive PVSQ varnish was prepared by the following procedure.
In a flask equipped with a magnetic stirrer, PVSQ and anisole
were mixed at room temperature. After BA was added into it, the
mixture was stirred for 10 h, and then filtered by a membrane filter
of 0.1 µm. The varnishes used by PVSQ with various vinyl group
contents from 0 mol% to 50 mol% in the side chain were pre-
pared.
Dielectric Measurements. The dielectric measurements of
the PVSQ film were carried out using a HP multifrequency ana-
lyzer. Medium frequency (10 kHz to 4 MHz) capacitance and loss
tangents were measured at room temperature. The specimens for
dielectric measurements were prepared by vacuum deposition of a
gold electrode (3 mm in diameter) on the spin coated PVSQ film
(10 µm thickness) with the back surface of the low resistivity Si
wafer serving as another electrode.
Photoirradiation and Photosensitivity. PVSQ films spin-
coated on a silicon wafer were prebaked at 130 ˚C for 2 min on a
hot plate and exposed to i-line with 500 mJ cmꢀ2 using a filtered
250 W super high pressure mercury lamp with glass filters (Toshi-
ba, UV-35 and UVD40A). Imagingwise exposure through a mask
was carried out in a contact-printing mode with a proximity mask
aligner. Exposed films were developed in a mixture of anisole and
xylene at 25 ˚C and subsequently rinsed with xylene. The charac-
teristic sensitivity curve was expressed by plotting a normalized
film thickness against the logarithmic exposure energy.
Fig. 2.
Photocrosslinking reaction between PVSQ and BA.
are decomposed to form active nitrene intermediate by releas-
ing nitrogen molecules. Nitrene adds to vinyl groups to
crosslink PVSQ, giving films which are insoluble in any kinds
of solvents.19–25
Results and Discussion
In this article, the preparation and characterization of a nov-
el photosensitive silicone ladder polymer system consisting of
PVSQ and BA are reported. Pattern fabrication of the films re-
quired for microelectronic application has been successfully
demonstrated.
Synthesis of PVSQ. PVSQ was prepared in the two steps,
i.e., hydrolysis and condensation of organotrichlorosilane as
shown in Fig. 3.8–11 At first, the starting materials, a mixture of
trichlorophenylsilane and trichloro(vinyl)silane in the desired
mol ratio, were hydrolyzed in MIBK under stirring at 0 ˚C.
After removal of the acid layer of the hydrolysate product, the
MIBK solution was washed with pure water to be neutralized,
and then the prepolymer was obtained. The average molecular
weight (Mw) was about 2,000. The prepolymer solution was
heated under refluxing in the presence of potassium hydroxide
as a catalyst, resulting in further polymerization by dehydra-
tion condensation reaction. The reaction mixture was purified
by pouring into a methanol aqueous solution to give a white
precipitate of PVSQ. The PVSQ was dried in vacuo. The
yield of the resulting PVSQ was 70%. This process gave the
molecular weight over 104. We synthesized PVSQ of the mo-
lecular weight of about 3ꢂ104 with various vinyl group con-
tents from 0 mol% to 50 mol% and PVSQ of the molecular
weight of about 1.54ꢂ105 with 5 mol% vinyl groups by the
above-mentioned synthetic method.
Experimental
Chemicals. The raw materials of PVSQ, trichlorophenylsi-
lane and trichloro(vinyl)silane, were purchased from Shin-Etsu
Chemical Industry Ltd., and were purified by distillation before
use. Isobutyl methyl ketone (MIBK), anisole, and xylene were
purchased from Kanto Chemical Industry Ltd.. Tetrahydrofuran
was purchased from Tokyo Chemical Industry Ltd.. 2,6-bis(azi-
dobenzylidene)-4-methylcyclohexanone as a photocrosslinker was
obtained from Aldrich Co., and used without further purification.
Apparatus. The apparatus for identification and character-
ization of synthesized PVSQ is as described below. Fourier trans-
form infrared (FT-IR) spectra were measured on a JASCO Model
FT/IR-230 spectrometer. 1H and 29Si NMR data were obtained
with a Bullker Model MSL-300 (230 MHz) instrument in CDCl3,
with tetramethylsilane (TMS) as an internal standard. Determina-
tion of molecular weight of PVSQ was obtained with a JASCO
Model TRI ROTER-IV gel permeation chromatograph (GPC).
UV-vis absorption spectra were obtained with a Shimadzu MPS-
2000. Thermogravimetric analyses (TGA) were performed with a
heating rate of 5 ˚C/min in air by a Du Pont Model 951 thermo-
gravimetric analyzer. O2-RIE (Reaction ion etching) resistance
was estimated on an ANELVA Model DEM-452T. A mask aligner
of a Mikasa Model MA-10, and a spin developer (Kyoei Semicon-
FT-IR and NMR were measured for confirming the structure
of PVSQ random copolymers of Mw ꢁ 3.1ꢂ104 with 50 mol%
vinyl group content and Mw ꢁ 1.54ꢂ105 with 5 mol% vinyl
group content.26 In the FT-IR spectra of both PVSQ, the IR
bands of 1130 cmꢀ1 and 1038 cmꢀ1 attributed to Si–O–Si
asymmetrical stretching vibration indicated the presence of the
cis-syndiotactic double-chain structure of PVSQ.4 In the 29Si
NMR spectra of both PVSQ, only one sharp single peak as-

N. Yasuda et al.
Bull. Chem. Soc. Jpn., 74, No. 5 (2001) 993
Fig. 4.
Dependence of photocrosslinking behavior of the
PVSQ films on the BA content. After i-line exposure at
500 mJ cmꢀ2, PVSQ film (ꢁ: Mw ꢁ 30,000, Ph/Vinyl ꢁ
50/50) and PVSQ film (ꢀ: Mw ꢁ 154,000, Ph/Vinyl ꢁ 95/
5) were developed with anisole or a mixture of anisole/xy-
lene ꢁ 1/2, respectively.
Fig. 3.
Synthesis of PVSQ.
signed to trifunctional siloxane: RSi(–O–)3 at δ ꢀ78 (s) was
observed while the peaks assigned to monofunctional siloxane:
RSi(–O–)(OH)2 and difunctional siloxane: RSi(–O–)2(OH)
were not observed, also indicating the presence of the cis-syn-
diotactic double-chain structure of PVSQ.27,28
Photochemical Characteristics of Photosensitive PVSQ.
The PVSQ varnish of the molecular weight of about 3ꢂ104
with 50 mol% vinyl groups was spin-coated onto Si wafers and
prebaked at 120 ˚C for 2 min on a hot plate to produce films of
about 2 µm thickness. After photocrosslinking by i-line expo-
sure at 500 mJ cmꢀ2, the samples were dip-developed in ani-
sole for 30 s and rinsed in xylene for 30 s. Figure 4 shows the
dependence of the normalized remaining film thickness on the
BA content. The remaining thickness increased gradually with
increasing of BA content, and reached 78% at 5 wt%.
The content of vinyl groups in the side chain of PVSQ also
affected the photosensitivity, as did the BA content. We syn-
thesized PVSQ of the molecular weight of about 3ꢂ104 with
various vinyl group contents from 0 mol% to 50 mol%. Figure
5 shows the relationship between the vinyl content and the nor-
malized remaining film thickness. The BA content was held
constant at 5 wt% of the PVSQ weight therein. The higher vi-
nyl content of PVSQ showed the higher remaining thickness.
The starting point of weight loss on a TGA curve in air was
adopted as a measure of the thermal decomposition tempera-
ture. The thermal decomposition temperature of PVSQ con-
taining vinyl content less than 5 mol% stayed at 475 ˚C (Fig.
5), but decreased suddenly with increase of the vinyl content.
Optimization of the vinyl content is the most important step in
realizing practically favorable PVSQ characteristics. Judging
from the ability of PPSQ to maintain the heat resistance, we
chose the 5 mol% vinyl polymer for further evaluation of this
material.
When we employed PVSQ polymer (vinyl content: 5 mol%,
molecular weight: 1.54ꢂ105) and a mixture of anisole and xy-
lene as a developer, the thickness of the film remaining after
development was high. The plots (ꢀ) in Fig. 4 show depen-
dence of the normalized remaining thickness on the BA con-
tent for PVSQ (Mw ꢁ 1.54ꢂ105) by dip-development in ani-
sole/xylene ꢁ 1/2. The film of the initial thickness, 4.2 µm,
made of PVSQ was employed for the evaluation. The normal-
ized remaining thickness increased with increasing of the BA
content and reached 92% above the BA content of 3 wt%. The
decrease of the solubility in anisole due to the enormous mo-
lecular weight of PVSQ and the change of the developer com-
position brought both the higher normalized remaining thick-
ness, over 90%, and the high decomposition temperature of
480 ˚C (Fig. 5). Consequently, for the following evaluations
we used the varnishes consisting of PVSQ (Mw ꢁ 1.54ꢂ105, 5
mol% vinyl content) as a base polymer and BA content of 3
wt% as a photocrosslinker, and a mixture of anisole/xylene ꢁ
1/2 as a developer.
Figure 6 shows the photosensitivity curve of PVSQ. The
PVSQ varnish was spin-coated onto Si wafers and prebaked at
130 ˚C for 120 s on a hot plate to produce a film of 4.2 µm.
Exposures were carried out with a mask aligner for i-line. The
samples were developed in an anisole/xylene ꢁ 1/2 mixture
for 30 s and rinsed in xylene for 30 s with a spin developer.
The sensitivity to i-line was 40 mJ cmꢀ2 at the expose dose of
50% normalized remaining film thickness after development

994 Bull. Chem. Soc. Jpn., 74, No. 5 (2001)
Novel Photosensitive Silicone Ladder Polymer
The thermal stability of PVSQ photocrosslinked with 3 wt%
BA by being exposed to i-line and baked at 350 ˚C was deter-
mined by TGA in comparison with PVSQ without photo-
crosslinking. The TGA curves (Fig. 7) showed that the ther-
mal decomposition of the photocrosslinked PVSQ started at
520 ˚C, showing much higher stability than that without photo-
crosslinking (480 ˚C). The photocrosslinking reaction of
PVSQ molecules by BA should improve its thermal resistance.
The inset of Fig. 7 shows FT-IR spectra of PVSQ films after
being baked at 350 ˚C and 600 ˚C for 60 min under air. In the
spectrum of PVSQ film baked at 350 ˚C, the IR bands near
1050 and 1140 cmꢀ1 attributed to Si–O–Si asymmetrical
streching vibration indicated the presence of the cis-syndiotac-
tic double-chain structure of PVSQ and the IR band of 1430
cmꢀ1 assigned to Si–Ph streching vibration was observed. The
IR band of 1405 cmꢀ1 assigned to Si–CHꢁCH2 was below the
noise level because of the very low content of vinyl groups. In
the spectra of PVSQ films baked at 600 ˚C, the IR bands as-
signed to Si–Ph disappeared. Furthermore, the double peak as-
signed to Si–O–Si changed to a single peak at 1080 cmꢀ1 and
the Si–O streching vibration of SiO2 appeared at about 800
cmꢀ1. These changes in IR spectra demonstrated that the bak-
ing at higher temperature than the decomposition temperature
of PVSQ causes the phenyl groups to dissociate, and the cis-
syndiotactic double-chain structure of PVSQ to change to the
three dimensional network structure of SiO2.
Fig. 5.
Dependence of thermal decomposition temperature
and photocrosslinking behavior of PVSQ films on the
–CHꢁCH2 content. The plots (ꢁ) show the thermal de-
composition temperature of PVSQ (Mw ꢁ 30,000) poly-
mers with different vinyl content in the side chain. The
plot (ꢀ) shows the thermal decomposition temperature of
PVSQ polymer (Mw ꢁ 154,000, Ph/Vinyl ꢁ 95/5). After i-
Figure 8 shows the retention of the PVSQ film thickness af-
ter being baked at 350 ˚C for 60 min. The initial thickness of
the films after being exposed to i-line and prebaked at 130 ˚C
for 2 min on a hot plate was 4.2 µm. Little film thickness loss
was observed after being baked at 350 ˚C. Desorption of only
a slight amount of H2O was detected below 350 ˚C, suggesting
that the dehydration condensation of silanol groups occurred at
the end of the chain in the insoluble polymer. On the other
line exposure at 500 mJ cmꢀ2, PVSQ film (ꢂ: Mw
30,000) and PVSQ film (ꢃ: Mw ꢁ 154,000, Ph/Vinyl ꢁ
95/5) were developed with anisole or a mixture of anisole/
xylene ꢁ 1/2, respectively.
ꢁ
Fig. 6.
Sensitivity characteristics of photosensitive PVSQ
(Mw ꢁ 154,000, Ph/Vinyl ꢁ 95/5, BA: 3wt%). The PVSQ
varnish was spin coated onto Si wafers and initial thickness
was 4.2 µm. The wafers were developed with a mixture of
anisole/xylene ꢁ 1/2 and rinsed with xylene.
Fig. 7.
TGA spectra of PVSQ films (Mw ꢁ 154,000, Ph/
(Dn0.5). The suitable exposure dose was determined to be 500
mJ cmꢀ2. In spite of a rigid structure of PVSQ, a photosensi-
tivity value high enough for practical use as protecting films of
LSI was obtained.
Vinyl ꢁ 95/5), (a) PVSQ film with BA after irradiated and
baked at 350 ˚C for 60 min and (b) PVSQ film without BA
after baked at 350 ˚C for 60 min. (C) shows FT IR spectra
of PVSQ films (Mw ꢁ 154,000, Ph/Vinyl ꢁ 95/5) after
baked at 350 ˚C, 600 ˚C for 60 min in air.
Thermal Properties of Photosensitive PVSQ Films.

N. Yasuda et al.
Bull. Chem. Soc. Jpn., 74, No. 5 (2001) 995
Fig. 9.
The residual thickness of (a) PVSQ film (Mw ꢁ
Fig. 8.
The retention of (a) PVSQ film (Mw ꢁ 154,000, Ph/
154,000, Ph/Vinyl ꢁ 95/5, BA: 3 wt%) after irradiated and
baked at 350 ˚C for 60 min and (b) photoresist (OFPR800)
versus the O2 plasma etching time using a parallel plate
rector. The etchings were carried out under the following
condition. Gas: O2, Flow: 200 sccm, Pressure: 25.6 Pa, In-
cident Power: 300 W, Electrode Voltage: 460 V, Plate Cur-
rent: 200 mA.
Vinyl ꢁ 95/5, BA: 3 wt%) after irradiated and baked at 350
˚C for 60 min and (b) polyimide film (PIX) after baked at
350 ˚C for 60 min.
hand, in the commercially available polyimide film (PIX-3500;
Hitachi Chemical Inc. Co.), the baking process induced reduc-
tion of the film thickness by 40% due to degasification. Appli-
cation of Polyimide film to the layer insulating films should be
quite difficult, since degasification contaminates devices.
Therefore PVSQ film is suitable for application to microelec-
tronics as insulating films between layers in the multilayer
writing method to attain the higher integration circuits or
large-scale integrated circuits.
i.e., SiO2 during O2-RIE. This layer was considered to play an
important role as a protective layer for interception of O2 plas-
ma.31
Pattern Fabrication. The pattern formation represented
in Fig. 10 has been attempted. First, PVSQ was spin-coated on
a Si wafer and baked at 130 ˚C for 120 s on a hot plate to yield
a 4.20 µm thick film. After i-line exposure at 500 mJ cmꢀ2
through a photomask with patterns, the film was developed in a
mixture of anisole/xylene ꢁ 1/2 for 30 s and then rinsed in xy-
lene for 30 s with a spin developer. The resolution of the ob-
tained patterns was evaluated by SEM. The film thickness af-
ter the development was 3.90 µm, that is 92% of the initial
thickness. The pattern edge exhibited a taper shape. Figure 10
shows a 18 µm line and 18 µm space pattern and a 18 µm via
hole pattern. It was found that the mask patterns were rather
accurately transferred into the PVSQ dielectric film.
Physical Properties of Photosensitive PVSQ Films.
The dielectric constant for the PVSQ film after being exposed
to i-line light and baked at 350 ˚C for 60 min was 3.21 (1
MHz), as determined from the dielectric measurements; this
value was substantially lower than those of polyimide films
(3.4ꢀ).29 PVSQ may thus be applicable not only to protection
layers but also to insulation layers of LSI production, thanks to
this value.
When PVSQ was employed as an interdielectric in the mul-
tilayer writing structure, PVSQ must possess very high resis-
tance to O2-RIE used at the ashing process of photoresists on
the fabrication of the upper layers, i.e., metal electric wiring,
and inorganic films.30 So we estimated the O2-RIE resistance
of PVSQ. PVSQ was spin-coated onto Si wafer. After baking
at 130 ˚C for 120 s, PVSQ film on the wafer was exposed to i-
line of 500 mJ cmꢀ2, and then the wafer was baked at 350 ˚C
for 60 min. A parallel plate rector was employed to study the
O2-RIE resistance of PVSQ. The etchings were carried out un-
der O2 (25.6 Pa pressure) and 300 W rf power. The flow rate of
O2 was fixed at 200 sccm. Figure 9 shows the residual thick-
ness of the PVSQ film versus the etching time in comparison
with that of a novolak photoresist, OFPR-800 (Tokyo Ohka
Kogyo Corp). The etching rate of PVSQ was 22.5 Å minꢀ1
and was much lower than 4062.5 Å minꢀ1 of OFPR-800,
showing the much higher resistance of PVSQ to O2 plasma.
On the surface of PVSQ, organic groups in PVSQ contained as
the side chains were dissociated by chemical etching during
O2-RIE. The surface of PVSQ film became an inorganic layer,
Conclusions
A novel photosensitive silicone ladder polymer (PVSQ)
based on polyphenylsilsesquioxane with vinyl groups as a re-
active substituent in the side chains, and 2,6-bis(azidoben-
zylidene)-4-methylcyclohexanone (BA) as a photocrosslinker,
was developed. The monodisperse PVSQ was prepared by co-
polymerization of trichlorophenylsilane and trichloro(vinyl)si-
lane using potassium hydroxide as a catalyst in MIBK. This
PVSQ having vinyl groups was highly soluble in common sol-
vents. PVSQ containing BA was found to work as a negative-
tone photosensitive dielectric with high sensitivity. The PVSQ
containing 3 wt% of BA showed a sensitivity of 40 mJ cmꢀ2
when it was exposed to i-line, followed by development with a
mixture solution of anisole and xylene at 25 ˚C. This exposed
PVSQ film also showed the high thermal decomposition tem-
perature (520 ˚C) and the low dielectric constant (3.21/1
MHz). The photosensitivity and thermal characteristic were

996 Bull. Chem. Soc. Jpn., 74, No. 5 (2001)
Novel Photosensitive Silicone Ladder Polymer
Fig. 10.
SEM photograph of patterning profiles after development and baked of PVSQ film (thickness: 3.9 µm).
Electrochem. Soc., 131, 2402 (1984).
14 R. Rubner, H. Ahne, E. Kuhn, and G. Kolodziej, Photogr.
Sci. Eng., 23, 303 (1979).
15 N. Yoda and H. Hashimoto, J. Macromol. Sci. Chem., A,
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attributed to the fact that the crosslinking reaction was a chain
reaction using the addition reaction between vinyl groups of
PVSQ and nitrenes formed from BA. PVSQ also can be pro-
cessed into films without shrinkage and degasification during
curing. Photosensitive PVSQ requires no thermal curing, due
to being insoluble in most common solvents. Therefore this
PVSQ/BA system can be applied not only to protection layers
but also to insulation layers in the multilayer writing method of
devices sensitive to heat.
19 L. S. Efros and T. A. Yurre, Vysokomol. Soedin. A, 12, 2211
(1970).
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