Abstract
ABSTRACT
The thesis entitled “Design and Synthesis of Novel Organic Photo Imaging
Compounds and Their Lithographic Applications” has been divided into three parts and
five chapters. Part I contains Chapter 1, part II contains Chapter 2, Chapter 3 and Chapter 4
part III contains Chapter 5. Chapter 1 explains the various aspects of Introduction to
Photolithography:
An
overview.
Chapter
2
reveals
about
the
synthesis
of
diazonaphthoquinonesulfonic acid derivatives and their photochemical studies. Chapter 3
deals with synthesis of bisphenols and diazonaphthoquinonesulfonic acid bisphenol
derivatives and their lithographic evaluations. Chapter 4 explains about the synthesis of
photoacid generators and their use in negative photoresist formulations. Chapter 5 deals with
preparation of photoactive compounds for making positive photoresists and estimation of
photoactive compounds by HPLC method.
PART-I
Chapter-1: Introduction to photolithography: An overview
Photoresists are widely used in electronic industry for the past several decades. The
trend in usage of photoresists is still increasing. The basic fundamental principle involved in
the photoresists is the photochemical generation of reactive intermediate in a polymer
environment and its subsequent chemical reaction or physical change leading to resist
Processing.
There are two types of photoresists: positive and negative. For positive resists, the
resist is exposed with UV light wherever the underlying material is to be removed. In these
resists, exposure to the UV light changes the chemical structure of the resist so that it becomes
more soluble in the developer. The exposed resist is then washed away by the developer
i
Abstract
solution, leaving windows of the bare underlying material. In other words, "whatever shows,
goes." The mask, therefore, contains an exact copy of the pattern, which is to remain on the
wafer.
Negative resists behave in just the opposite manner. Exposure to the UV light causes
the negative resist to become polymerized, and more difficult to dissolve. Therefore, the
negative resist remains on the surface wherever it is exposed, and the developer solution
removes only the unexposed portions. Masks used for negative photoresists, therefore, contain
the inverse (or photographic "negative") of the pattern to be transferred. The figure below
shows the pattern differences generated from the use of positive and negative resist.
Photoresists are used in microelectronic industry and essential for a country like India.
Presently these photoresists are imported and there is no production activity exists in India.
These photoresists have become "Strategic" materials. Positive Photoresists are made up of
essentially four components.

Photo Activating Compounds (PAC)

Novolac resin

Solvent and

Additives
Primary goal was to prepare photo activating compounds required for making
Photoresists. Photoresists with various formulations were prepared to study their suitability.
The photochemical behavior of photo activating compounds prepared were studied.
ii
Abstract
PART-II
Chapter 2: Synthesis of diazonaphthoquinonesulfonic acid derivatives and their
photochemical studies
The compounds diazonaphthoquinonesulfonic acid derivatives (1-9) are synthesized to
study
photochemical
behavior.
Diazonaphthoquinone
derivates
have
important
photolithographic applications. Synthesis of these compounds were started from 4-amino-1naphthalenesulfonic acid sodium salt treated with sodium hydroxide, sodium bisulfate is
added then refluxed for 24 h and finally treated with sodium chloride to get 4-hydroxy-1naphthalenesulfonic acid sodium salt. These 4-hydroxy-1-naphthalenesulfonic acid sodium
salts were treated with sodium nitrite, conc. hydrochloric acid, sodium hydroxide solution,
sodium dithionite and finally with conc. hydrochloric acid to obtain 3-amino-4-hydroxy-1naphthalenesulfonic
acid
hydrochloride.
Diazotization
of
3-amino-4-hydroxy-1-
naphthalenesulfonic acid hydrochloride, using cupric chloride and sodium nitrite treated with
sodium chloride gave 3-diazo-4-oxo-3,4-dihydro-1-naphthalenesulfonic acid sodium salt.
When sodium salt was treated with diphosgene or triphosgene and organic base in presence of
a solvent we got 3-diazo-4-oxo-3,4-dihydro-1-naphthalenesulfonylchloride. Finally this
sulfonylchloride was treated with phenol and organic base to get the desired Phenyl 3-diazo4-oxo-3,4-dihydro-1-naphthalenesulfonate. Similar procedure was adopted to the other
compounds. (Chart 1) (Scheme 1).
iii
Abstract
Chart 1:
O
O
O
N2
N2
N2
O S O
O
O S O
Cl
O S O
ONa
1
3
2
O
O
O
N2
N2
N2
O S O
O
O S O
Cl
O S O
ONa
4
6
5
N2
N2
N2
O
O
O
O S O
O
O S O
Cl
O S O
ONa
7
8
9
Scheme 1:
NH 2
OH
OH
NaOH,
NaHSO3
HCl, NaNO2
NaOH, Na2S2O4
NaCl
SO3Na
NH 2
SO3Na
SO3H
NaCl
NaNO2
NaCl
OH
NaOH, Na2S2O4
NaCl
SO3H
N2
CuCl2
NaNO2
NaCl
SO3Na
4
iv
SO3Na
O
NH 3Cl
HCl, NaNO2
SO3Na
N2
CuCl2
1
OH
NaOH,
NaHSO3
NaCl
SO3Na
O
NH 3Cl
Abstract
NH 3Cl
OH
N2
O
CuCl2, NaNO2
NaCl
SO3Na
An
innovative
process
SO3Na
7
has
been
developed
for
the
preparation
of
diazonaphthoquinonesulfonyl chloride (Scheme2) diazonaphthoquinonesulfonic acid sodium
salt, using diphosgene (DP) or triphosgene (TP), triethylamine (TEA).
Scheme 2:
O
O
N2
N2
TEA, -50 oC
DP/TP
1
SO3Na
2
O
SO2Cl
O
N2
N2
TEA, -50 oC
DP/TP
SO3Na
4
N2
SO2Cl
5
N2
O
O
TEA, -50 oC
DP/TP
7
SO3Na
8
SO2Cl
An innovative process was developed to make corresponding esters in a single step
using diazonaphthoquinonesulfonic acid sodium salt, diphosgene/triphosgene, triethylamine
and phenols (Scheme 3).
v
Abstract
Scheme 3:
O
O
N2
N2
(i) DP/TP/TEA, -40oC
(ii) TEA, PhOH,0oC
1
SO3Na
3
O
SO3Ph
O
N2
o
N2
(i) DP/TP/TEA, -40 C
(ii) TEA, PhOH,0oC
SO3Na
SO3Ph
4
6
N2
N2
O
(i) DP/TP/TEA, -40oC
O
(ii) TEA, PhOH,0oC
SO3Na
9
7
Photochemistry
of
Diazonaphthoquinonesulfonic
acid
SO3Ph
Phenyl
Esters
(Wolff
rearrangement):
After the synthesis of diazonaphthoquinonesulfonyl ester, the photochemical behavior
of the compounds were studied. The diazonaphthoquinonesulfonic acid phenyl ester was
irradiated (365 nm) in the presence of alcohol or a medium, the electronic excited
diazonaphthoquinone loose molecular nitrogen, formation of ketocarbene and rearrange to
ketene undergoes Wolff rearrangement, leading to ring contraction and eventually to the
formation of corresponding indenecarboxylic acid (Scheme 4).
vi
Abstract
Scheme 4:
O
O
C
O
N2 hv
SO3Ph
6
365 nm
-N2
O
SO3Ph
O
C OR
OH
SO3Ph
SO3Ph
O
C
N2 hv
3
C
ROH
O
365 nm
SO3Ph -N2
RO
RO
C
SO3Ph
O
C OR
OH
ROH
SO3Ph
SO3Ph
SO3Ph
SO3Ph
Chapter 3: Synthesis of Bisphenols and Diazonaphthoquinonesulfonic Acid Bisphenol
Derivatives and Their Lithographic Evaluations
Synthesized new class of photoactivating compounds to study their photochemical
behavior and photolithographic applications. Bisphenols (10-26) (Chart 2) were synthesized
using phenol and ketone. This reaction is catalyzed by dry hydrochloric acid, hyrdonium ion
(H+). Thus prepared bisphenols were used for the synthesis of new photoactivating
compounds. Bisphenols were reacted with diazonaphthoquinonesulfonic acid or its sodium
salt,
triethylamine,
diphosgene
or
triphosgene
to
get
new
type
of
diazonaphthoquinonesulfonic acid bisphenol esters (27-34) (Chart 3). Esters are light sensitive
compounds so while synthesizing have to maintain yellow room or dark room conditions.
Thus synthesized esters were working as a very good photoactivating compounds. Using these
esters, novolac resin, additive and appropriate solvent prepared photolithographic plates.
vii
Abstract
Chart 2:
OH
OH
OH
OH
OH
CH 3
OH
10
OH
11
OH
OH
12
OH
OH
F
OH
OH
OH
18
17
OH
F
OH
Br
OH
16
OH
OH
OH
Cl
OH
15
OH
14
OH
13
19
OH
OH
Cl
Br
OH
OH
OH
OH
20
21
22
23
OH
HO
OH
OH
HO
Br
OH
24
25
viii
26
Abstract
Preparation of Various Bisphenols:
Variety
of
bisphenols
were
prepared
for
the
preparation
of
new
diazonaphthoquinonesulfonic acid esters. These are the new photoactivating compounds for
preparation of positive photoresist materials. Studied photochemical behavior of the
photoactivating compounds were studied. In this regard bisphenols were prepared as given
below. Phenol and ketone were mixed in the presence of dry hydrochloric acid gas (H+
catalyzed reactions) to get various bisphenols (Scheme 5).
Scheme 5:
OH
O
+
Above
prepared
R
R1
H+
bisphenols
OH
HO
R1
R
were
used
for
the
preparation
of
new
diazonaphthoquinonesulfonic acid bisphenol derivatives. Diazonaphthoquinonesulfonic acid
or sodium salt were treated with triethylamine, diphosgene or triphosgene and bisphenol to
get corresponding diazonaphthoquinonesulfonic acid bisphenol derivatives (Chart 3) (Scheme
6).
ix
Abstract
Chart 3:
O
O
N2
N2
O
O
S O
O
O
S O
O
O
N2
29
O
31
30
O
N2
O
N2
S O
O
O
O
O S O
S O
O
O
O S O
N2
O
O
O
N2
O
O S O
N2
28
O
S O
O
O
O S O
O
27
S O
O
O
N2
O
O
S O
O
N2
O
O S O
N2
N2
O
N2
O
O S O
O
O S O
O
N2
N2
O
S O
O
O
O S O
N2
O
O
O
32
33
34
x
Abstract
Scheme 6:
O
N2
O S O
O
OH
O
(i) CH2Cl2, - 50 0C, TEA, 1 h
N2
+
R
R1
R
R1
(ii) TEA, 0-rt, 1 h
SO3Na
OH
O
O S O
(27) R=Me,R1=Et ;
(28) R=R1=Et ;
(29) R=Me,R1=isoBt ;
(30) R=R1=Cyclopentyl;
N2
O
O
N2
O S O
O
OH
O
N2
+
(i) CH2Cl2, - 50 0C, TEA, 1 h
R
R1
R
R1
(ii) TEA, 0-rt, 1 h
SO3Na
OH
(31) R=Me,R1=Et ;
(32) R=R1=Et ;
(33) R=Me,R1=isoBt ;
(34) R=R1=Cyclopentyl;
O
O S O
N2
O
xi
Abstract
Synthesis of Novolac Resin:
m-Cresol, p-Cresol, 2, 3-xylenol, aqueous solution of formaldehyde and oxalic acid
dihydrate were refluxed and novolac resin was obtained. The weight average molecular
weight of the thus-obtained novolac resin was 2400-5400 in terms of polystyrene (Scheme 7).
Scheme 7:
OH
OH
OH
+
+
+
H
NOVOLAC RESIN
OXALIC ACID
O
H
reflux
mw ~ 2400-5400
+
Above
synthesized
diazonaphthoquinonesulfonic
acid
bisphenols
derivatives
(photoactivating compounds) and novolac resin were formulated them in CEERI Pilani.
Result achieved 0.50 micro line width patterns (SEM Picture).
Scanning Electron Micrograph (SEM) PICTURES
xii
Abstract
POSITIVE PHOTORESIST FORMULATIONS: OBSERVATION TABLE
S.No Novolac Photo
Resin
Sensitizer
g
g
EEA
Spin
Thickness Exposure Dev.
mL
Coating
μm
Speed rpm
Time
Time
Sec
Sec
Remarks
1
3g
300mg
10
2000
1.5
15-25
65 Pattern open
2
3g
300mg
10
2500
1.5
15-25
65 Pattern open
3
3g
300mg
10
3000
1.5
15-20
60 Pattern open
4
3g
300mg
10
3500
1.0
15-20
60 Pattern open
5
3g
300mg
10
4000
1.0
15-20
60 Pattern open
Under Lying Layer: oxide; Lab Temp: 25 0C; Lab Humidity: 52%; Resist Amount: 2 mL;
Prebaking Temp: 90 0C; Prebaking Time: 30 min; Mask: XC 1705; Develop: 100 mL of DI
water in 25 mL of developer (MF CD-26 Micro Posit); Post Bake: 120 0C; Post Bake Time:
30 min;
Chapter 4: Synthesis of photoacid generators and their use in negative photoresist
formulations
A negative resist is a type of photoresist in which the portion of the photoresist that is
exposed to light becomes insoluble to the photoresist developer. The unexposed portion of the
photoresist is dissolved by the photoresist developer.
Bromobenzene was converted into PhMgBr (Grignard reaction) then allowed to react
with diphenylsulfoxide, treated with HBr leading to triphenylsulfonium bromide. The
xiii
Abstract
Bromide counter ion can be exchanged with various other counter ions (Scheme 8) leading to
new photoacid generators derived from triphenylsulfonium compounds (Chart 4). Several
compounds were prepared replacing anionic moiety.
Chart 4:
S
S
F
F
S
S
Br
C6F5SO3
C4F9SO3
C4F9SO3
37
38
NO 2
NO 2
NO 2
S
S
S
35
36
F
S
Br
C4F9SO3
C6F5SO3
39
41
40
S
C
O
C
O
C4F9SO3
43
42
S
S
Br
C6F5SO3
C6F5SO3
44
45
Scheme 8:
Br
Mg Br
Mg metal
Ph
Dry ether
O
S
HBr
xiv
Ph
S Br
C
O
Abstract
S Br
RT
+ CF (C F )SO K
3 3 6
3
CF3(C3F6)SO3
S
35
SO3
S Br
SO3
Ba
F
F
F
F
F
RT
+
F
S
F
F
2
F
F
36
Above synthesized photoacid generators were used in the cationic polymerization
using SU-8, LAPOX RESIN etc. Depend on acid strength cationic polymerization easily
taking place. Exposure and developing time also varying. FromTGA/DSC data for these
compounds, it can be concluded that these compounds are thermally stable.
The resist is supplied as a liquid consisting of an epoxy resin, a solvent (GBL or
cyclopentanone depending on formulation) and a photo-acid generator. The substrate is
coated using a conventional photoresist spinner, with the film thickness controlled by the spin
speed and the solids content of the epoxy solution. A baking stage removes excess solvent
from the layer. Upon exposure to UV radiation, a strong acid (HSbF6) is generated which
causes the epoxy resin to form a ladder-like structure with a high cross-linking density when
heated above a critical temperature provided in a post-exposure bake. The unexposed material
is then removed with a solvent in the development process.
xv
Abstract
PART III
Chapter 5: Preparation and Estimation of Photoactive Compounds by HPLC for
Making Positive Photoresists
Diazonaphthoquinone compounds are very good photoactivating compounds for
positive photoresists. These photoactive compound, 4-[1-(4-[(6-diazo-5-oxo-5,6-dihydro-1naphthalenyl)sulfonyl]oxyphenyl)-1-methylethyl]phenyl
6-diazo-5-oxo-5,6-dihydro-1-
naphthalenesulfonate (BPA-5-DNQ ESTER) was estimated by HPLC method by the use of 5hydroxy-1-naphthalenesulfonic acid sodium salt as internal standard. Methanol and water
system used as eluting system. The chromatographic conditions optimized by changing the
various parameters, such as mobile phase and different columns.
BPA-5-DNQ ESTER is a useful material for making positive photoresists and an
important intermediate in dye industry. HPLC method was developed for BPA-5-DNQ
ESTER in order to estimate the purity of the prepared compound by using 5-hydroxy-1naphthalenesulfonic acid sodium salt as internal standard. Estimated compound (BPA-5-DNQ
ESTER) purity was about 96.0%.
Sodium salt of 6-diazo-5-oxo-5,6-dihydro-1-naphthalenesulfonate in the presence of
diphosgene (DP) or triphosgene (TP), triethylamine (TEA) and 4-[1-(4-hydroxyphenyl)-1methylethyl]
phenol
give
oxyphenyl)-1-methylethyl]
4-[1-(4-[(6-diazo-5-oxo-5,6-dihydro-1-naphthalenyl)sulfonyl]
phenyl
6-diazo-5-oxo-5,6-dihydro-1-naphthalenesulfonate
(Scheme 9).
xvi
Abstract
Scheme 9:
O
O
N2
+ TRIPHOSGENE
N2
TEA
+ HO
OH
SOLVENT
SO3Na
SO2Cl
TEA
SOLVENT
N2
O
O
S
O
O
O S
O
O
O
46
N2
Estimation of BPA-5-DNQ ESTER by HPLC method:
4-[1-(4-[(6-diazo-5-oxo-5,6-dihydro-1-naphthalenyl)sulfonyl]oxyphenyl)-1methylethyl]
phenyl-6-diazo-5-oxo-5,6-dihydro-1-naphthalenesulfonate
(46)
was
a
photoactivating compound, which is useful intermediate in positive photoresist process.
5-hydroxy-1-naphthalenesulfonic acid sodium salt (47) is used as internal standard for the
estimation
of
4-[1-(4-[(6-diazo-5-oxo-5,6-dihydro-1-naphthalenyl)sulfonyl]oxyphenyl)-1-
methylethyl]phenyl 6-diazo-5-oxo-5,6-dihydro-1-naphthalenesulfonate.
N2
OH
O
O
S
O
O
O S
O
O
O
N2
46
SO3Na
47
Parameters for validation of HPLC method for a substance are Linearity, Limit of
detection (LOD), Limit of quantification (LOQ), Recovery, Precision and Accuracy.
xvii
Abstract
Chromatographic conditions:
The mobile phase consisted of methanol and water. Mobile phase pumped through the
system at flow rate of 1.0 mL/min and the injection volume was 20 L, detection wavelength
was 350 nm and sensitivity setting of 0.2000 AUFS. All the experiments were carried out at
ambient temperature. Retention times of 5-hydroxy–1-naphthalenesulfonic acid sodium salt
and 4-[1-(4-[(6-diazo-5-oxo-5,6-dihydro-1-naphthalenyl)sulfonyl]oxyphenyl)-1-methylethyl]
phenyl 6-diazo-5-oxo-5,6-dihydro-1-naphthalenesulfonate were 2.108 and 5.975 min.
xviii