U.S. patent application number 11/763705 was filed with the patent office on 2008-12-18 for graded topcoat materials for immersion lithography.
Invention is credited to Robert D. Allen, Phillip Brock, Daniel P. Sanders, Linda K. Sundberg.
Application Number | 20080311530 11/763705 |
Document ID | / |
Family ID | 40132660 |
Filed Date | 2008-12-18 |
United States Patent
Application |
20080311530 |
Kind Code |
A1 |
Allen; Robert D. ; et
al. |
December 18, 2008 |
GRADED TOPCOAT MATERIALS FOR IMMERSION LITHOGRAPHY
Abstract
A topcoat material for immersion lithography and a method of
performing immersion lithography using the topcoat material. The
topcoat material includes a mixture of a first polymer and a second
polymer. The first and second polymers of the topcoat material,
when the topcoat material is formed into a topcoat layer between an
immersion fluid and a photoresist layer, disperse non-homogenously
throughout the topcoat layer.
Inventors: |
Allen; Robert D.; (San Jose,
CA) ; Brock; Phillip; (Sunnyvale, CA) ;
Sanders; Daniel P.; (San Jose, CA) ; Sundberg; Linda
K.; (Los Gatos, CA) |
Correspondence
Address: |
SCHMEISER, OLSEN & WATTS
22 CENTURY HILL DRIVE, SUITE 302
LATHAM
NY
12110
US
|
Family ID: |
40132660 |
Appl. No.: |
11/763705 |
Filed: |
June 15, 2007 |
Current U.S.
Class: |
430/327 ;
430/273.1; 430/449 |
Current CPC
Class: |
G03F 7/2041 20130101;
Y10S 438/952 20130101; G03F 7/11 20130101 |
Class at
Publication: |
430/327 ;
430/449 |
International
Class: |
G03C 1/79 20060101
G03C001/79; G03C 5/305 20060101 G03C005/305 |
Claims
1-4. (canceled)
5. A method of forming an image in a photoresist layer, comprising:
(a) forming an anti-reflective coating over a top surface of a
substrate, wherein said photoresist layer is formed (b) forming
said photoresist layer on a top surface of said anti-reflective
coating; (c) forming a topcoat layer on a top surface of said
photoresist layer, said topcoat layer comprising a first polymer
and a second polymer, said second polymer different from said first
polymer, said second polymer miscible with said first polymer, said
first and second polymers of said topcoat layer dispersing
non-homogenously in a vertical direction perpendicular to said top
surface of said photoresist layer; (d) removing a casting solvent
from said topcoat layer by heating said photoresist layer to a
temperature above room temperature; (e) forming a layer of
immersion fluid between said topcoat layer and a final lens element
or window of an immersion lithography system; (f) exposing said
photoresist to radiation through a photomask having opaque and
clear regions, said opaque regions blocking said radiation and said
clear regions being transparent to said radiation, said radiation
changing the chemical composition of regions of said photoresist
layer exposed to said radiation, forming exposed and unexposed
regions in said photoresist layer; (g) heating said photoresist
layer to a temperature above room temperature. (h) removing either
said exposed regions of said photoresist layer or said unexposed
regions of said photoresist layer; (i) heating remaining regions of
said photoresist layer to a temperature above room temperature; (j)
removing said topcoat layer; wherein after step (c) and before step
(f) said first polymer has a first molar concentration at a top
surface of said topcoat layer that is greater than a second molar
concentration of said first polymer at a bottom surface of said
topcoat layer, said bottom surface of said topcoat layer in direct
physical contact with said top surface of said photoresist layer;
wherein after step (c) and before step (f) said second polymer has
a first molar concentration at a top surface of said topcoat layer
that is less than a second molar concentration of said second
polymer at a bottom surface of said topcoat layer, said bottom
surface of said topcoat layer in direct physical contact with said
top surface of said photoresist layer: wherein said immersion fluid
is selected from the group consisting of water, water with soluble
chemical additives, a hydrocarbon fluid, a water based
nano-particle dispersion, and a hydrocarbon based nano-particle
dispersion; wherein a weight percentage of fluorine in said first
polymer is greater than a weight percentage of fluorine in said
second polymer; wherein said first polymer is selected from the
group consisting of: (1) a polymer comprising: ##STR00029## (2) a
polymer comprising Y mer % of ##STR00030## and Z mer % of
##STR00031## wherein Y=any number from 0 to 100 and Z=any number
from 0 to 100 such that Y+Z is greater than or equal to 50 and less
than or equal to 100, (3) a polymer comprising ##STR00032## (4) a
polymer comprising: ##STR00033## (5) a polymer comprising Y mer %
of ##STR00034## and Z mer % of ##STR00035## wherein Y=any number
from 0 to 100 and Z=any number from 0 to 100 such that Y+Z is
greater than or equal to 50 and less than or equal to 100. (6) a
polymer comprising Y mer % of ##STR00036## and Z mer % of
##STR00037## wherein Y=any number from 0 to 100 and Z=any number
from 0 to 100 such that Y+Z is greater than or equal to 50 and less
than or equal to 100. (7) a polymer comprising: ##STR00038## (8) a
polymer comprising Y mer % of ##STR00039## and Z mer % of
##STR00040## wherein Y=any number from 0 to 100 and Z=any number
from 0 to 100 such that Y+Z is greater than or equal to 50 and less
than or equal to 100. (9) a polymer comprising Y mer % of
##STR00041## and Z mer % of ##STR00042## wherein Y=any number from
0 to 100 and Z=any number from 0 to 100 such that Y+Z is greater
than or equal to 50 and less than or equal to 100. (10) a polymer
comprising Y mer % of ##STR00043## and Z mer % of ##STR00044##
wherein Y=any number from 0 to 100 and Z=any number from 0 to 100
such that Y+Z is greater than or equal to 50 and less than or equal
to 100. (11) a polymer comprising Y mer % of ##STR00045## and Z mer
% of ##STR00046## wherein Y=any number from 0 to 100 and Z=any
number from 0 to 100 such that Y+Z is greater than or equal to 50
and less than or equal to 100. (12) a polymer comprising Y mer % of
##STR00047## and Z mer % of ##STR00048## wherein Y=any number from
0 to 99.9 and Z=any number from 0.1 to 100 such that Y+Z is greater
than or equal to 50 and less than or equal to 100, and (13) a
polymer comprising W mer % of ##STR00049## and Y mer % of
##STR00050## and Z mer % of ##STR00051## wherein W=any number from
0 to 99.9, Y=any number from 0.1 to 99.9, Z=any number from 0 to
99.9 such that W+Y+Z is greater than or equal to 50 and less than
or equal to 100; and wherein said second polymer is selected from
the group consisting of: (14) a polymer comprising Y mer % of
##STR00052## and Z mer % of ##STR00053## wherein Y=any number from
0 to 99.9 and Z=any number from 0.1 to 100 such that Y+Z is greater
than or equal to 50 and less than or equal to 100. (15) a polymer
comprising Y mer % of ##STR00054## and Z mer % of ##STR00055##
wherein Y=any number from 0 to 99.9, Z=any number from 0.1 to 100
such that Y+Z is greater than or equal to 50 and less than or equal
to 100. (16) a polymer comprising W mer % of ##STR00056## Y mer %
of ##STR00057## and Z mer % of ##STR00058## wherein W=any number
from 0 to 99.9, Y=any number from 0.1 to 99.9, Z=any number from 0
to 99.9 such that W+Y+Z is greater than or equal to 50 and less
than or equal to 100. (17) a polymer comprising W mer % of
##STR00059## Y mer % of ##STR00060## and Z mer % of ##STR00061##
wherein W=any number from 0 to 99.9, Y=any number from 0.1 to 99.9,
Z=any number from 0 to 99.9 such that W+Y+Z is greater than or
equal to 50 and less than or equal to 100. (18) a polymer
comprising Y mer % of ##STR00062## and Z mer % of ##STR00063##
wherein Y=any number from 0 to 99.9 and Z=any number from 0.1 to
100 such that Y+Z is greater than or equal to 50 and less than or
equal to 100. (19) a polymer comprising W mer % of ##STR00064## Y
mer % of ##STR00065## and Z mer % of ##STR00066## wherein W=any
number from 0 to 99.9, Y=any number from 0.1 to 99.9, Z=any number
from 0 to 99.9 such that W+Y+Z is greater than or equal to 50 and
less than or equal to 100. (20) a polymer comprising W mer % of
##STR00067## Y mer % of ##STR00068## and Z mer % of ##STR00069##
wherein W=any number from 0 to 99.9, Y=any number from 0.1 to 99.9,
Z=any number from 0 to 99.9 such that W+Y+Z is greater than or
equal to 50 and less than or equal to 100. (21) a polymer
comprising W mer % of ##STR00070## Y mer % of ##STR00071## and Z
mer % of ##STR00072## wherein W=any number from 0 to 99.9, Y=any
number from 0.1 to 99.9, Z=any number from 0 to 99.9 such that
W+Y+Z is greater than or equal to 50 and less than or equal to 100.
(22) a polymer comprising W mer % of ##STR00073## Y mer % of
##STR00074## and Z mer % of ##STR00075## wherein W=any number from
0 to 99.9, Y=any number from 0.1 to 99.9, Z=any number from 0 to
99.9 such that W+Y+Z is greater than or equal to 50 and less than
or equal to 100. (23) a polymer comprising W mer % of ##STR00076##
Y mer % of ##STR00077## and Z mer % of ##STR00078## wherein W=any
number from 0 to 99.9, Y=any number from 0.1 to 99.9, Z=any number
from 0 to 99.9 such that W+Y+Z is greater than or equal to 50 and
less than or equal to 100, and (24) a polymer comprising W mer % of
##STR00079## Y mer % of ##STR00080## and Z mer % of ##STR00081##
wherein W=any number from 0 to 99.9, Y=any number from 0.1 to 99.9,
Z=any number from 0 to 99.9 such that W+Y+Z is greater than or
equal to 50 and less than or equal to 100.
6-23. (canceled)
Description
FIELD OF THE INVENTION
[0001] The present invention relates to the field of immersion
photolithography; more specifically, it relates to topcoat
compositions for immersion lithography.
BACKGROUND OF THE INVENTION
[0002] In immersion lithography, an immersion fluid having a
refractive index higher than air is placed between the final lens
element or window of the exposure system and the photoresist layer
to be exposed. This affords higher numerical aperture imaging
systems and increases the depth of focus so smaller features may be
imaged with good process latitude. Immersion fluids can have
adverse effects on the photoresist by extracting key components the
photoresist such as sensitizers and photoacid generators and can
have adverse effects on the exposure system such as clouding the
immersed lens by depositing extracted photoresist materials on the
lens. To overcome these problems, topcoats are used to coat the
photoresist and protect the photoresist from the immersion fluid.
Topcoat materials are further designed to exhibit high receding
contact angles with the immersion fluid (usually water), in order
to enable rapid scanning of the wafer without film pulling (i.e.,
leaving a trail of film or droplets behind the receding meniscus of
the immersion fluid). Since these residual fluid droplets cause
defects in the final lithographically printed features, the
receding contact angle of the immersion fluid with the topcoat
effectively determines maximum wafer scan rate and tool throughput.
However, current topcoat materials interact with both the immersion
fluid at the topcoat/immersion fluid interface and with the
photoresist at the topcoat/photoresist interface. The requirement
to optimize the topcoat interaction at both interfaces has limited
the performance of topcoat materials, particularly in terms of
increasing the receding contact angle (and thereby increasing
maximum wafer scan rates). Accordingly, there exists a need in the
art to overcome the deficiencies and limitations described
hereinabove.
SUMMARY OF THE INVENTION
[0003] A first aspect of the present invention is a composition of
matter, comprising: a mixture of a first polymer and a second
polymer, the first polymer containing fluorine, the second polymer
miscible with the first polymer, the second polymer different from
the first polymer, a weight percentage of fluorine in the first
polymer greater than a weight percentage of fluorine in the second
polymer; a casting solvent; the first polymer comprising one or
more different monomers selected from the group consisting of:
##STR00001##
wherein each Z.sub.1, Z.sub.2, and Z.sub.3 is independently
selected from the group consisting of linear alkylenes, branched
alkylenes, cyclic alkylenes, polycyclic alkylenes, linear
heteroalkylenes, branched heteroalkylenes, cyclic heteroalkylenes,
polycyclic heteroalkylenes, ester groups, carbonyl groups,
carbonate groups, acetal groups, ketal groups, siloxyl groups,
carboxylic acid groups, carboxylic acid anhydride groups,
carboxylic acid anhydride half-ester groups, ether groups, amide
groups, carbamate groups, thioether groups, fluorinated linear
alkylenes, fluorinated branched alkylenes, fluorinated cyclic
alkylenes, polycyclic alkylenes, fluorinated linear
heteroalkylenes, fluorinated branched heteroalkylenes, fluorinated
cyclic heteroalkylenes, fluorinated polycyclic heteroalkylenes,
fluorinated ester groups, fluorinated carbonyl groups, fluorinated
carbonate groups, fluorinated acetal groups, fluorinated ketal
groups, fluorinated siloxyl groups, fluorinated carboxylic acid
groups, fluorinated carboxylic acid anhydride groups, fluorinated
carboxylic acid anhydride half-ester groups, fluorinated ether
groups, fluorinated amide groups, fluorinated carbamate groups, and
fluorinated thioether groups; wherein R.sub.1 is selected from the
group consisting of a fluoroalcohol group, a fluoroalcohol group
protected with an acid-labile group, a fluoroalcohol group
protected with a base-labile group, a fluoroalcohol group protected
with an acid-labile fluorinated group, a fluoroalcohol group
protected with a base-labile fluorinated group, and an
--X.sub.1--Y.sub.1 group wherein X.sub.1 is selected from the group
consisting of linear alkylenes, branched alkylenes, cyclic
alkylenes, polycyclic alkylenes, linear heteroalkylenes, branched
heteroalkylenes, cyclic heteroalkylenes, polycylic heteroalkylenes,
ester groups, carbonyl groups, amide groups, ether groups,
thioether groups, carbonate groups, carbamate groups, acetal
groups, ketal groups and Y.sub.1 is selected from the group
consisting of a fluoroalcohol group, a fluoroalcohol group
protected with an acid-labile group, a fluoroalcohol group
protected with a base-labile group, a fluoroalcohol group protected
with an acid-labile fluorinated group, and a fluoroalcohol group
protected with a base-labile fluorinated group; wherein R.sub.2 is
selected from the group consisting of hydrogen, fluorine, a
fluoroalcohol group, a sulfonamide group, a phenolic group, a
naphtholic group, a carboxylic acid group and a sulfonic acid group
and an --X.sub.2--Y.sub.2 group wherein X.sub.2 is selected from
the group consisting of linear alkylenes, branched alkylenes,
cyclic alkylenes, polycyclic alkylenes, linear heteroalkylenes,
branched heteroalkylenes, cyclic heteroalkylenes, polycylic
heteroalkylenes, ester groups, carbonyl groups amide groups, ether
groups, thioether groups, carbonate groups, carbamate groups,
acetal groups, ketal groups and Y.sub.2 is selected from the group
consisting of a fluoroalcohol group, a sulfonamide group, a
phenolic group, a naphtholic group, a carboxylic acid group and a
sulfonic acid group; wherein R.sub.3 is selected from the group
consisting of hydrogen, fluorine, an acid-labile group, a
base-labile group, an acid-labile fluorinated group, a base-labile
fluorinated group, linear alkanes, branched alkanes, cyclic
alkanes, polycyclic alkanes, linear heteroalkanes, branched
heteroalkanes, cyclic heteroalkanes, polycylic heteroalkanes,
fluorinated linear alkanes, fluorinated branched alkanes,
fluorinated cyclic alkanes, fluorinated polycyclic alkanes,
fluorinated linear heteroalkanes, fluorinated branched
heteroalkanes, fluorinated cyclic heteroalkanes, fluorinated
polycylic heteroalkanes and an --X.sub.3--Y.sub.3 group wherein
X.sub.3 is selected from the group consisting of linear alkylenes,
branched alkylenes, cyclic alkylenes, polycyclic alkylenes, linear
heteroalkylenes, branched heteroalkylenes, cyclic heteroalkylenes,
polycylic heteroalkylenes, ester groups, carbonyl groups, amide
groups, ether groups, thioether groups, carbonate groups, carbamate
groups, acetal groups, ketal groups and Y.sub.3 is selected from
the group consisting of hydrogen, fluorine, an acid-labile group, a
base-labile group, an acid-labile fluorinated group, a base-labile
fluorinated group, linear alkanes, branched alkanes, cyclic
alkanes, polycyclic alkanes, linear heteroalkanes, branched
heteroalkanes, cyclic heteroalkanes, polycylic heteroalkanes,
fluorinated linear alkanes, fluorinated branched alkanes,
fluorinated cyclic alkanes, fluorinated polycyclic alkanes,
fluorinated linear heteroalkanes, fluorinated branched
heteroalkanes, fluorinated cyclic heteroalkanes, fluorinated
polycylic heteroalkanes; and the second polymer comprising one or
more different monomers selected from the group consisting of:
##STR00002##
wherein each Z.sub.4, Z.sub.5, and Z.sub.6 is independently
selected from the group consisting of linear alkylenes, branched
alkylenes, cyclic alkylenes, polycyclic alkylenes, linear
heteroalkylenes, branched heteroalkylenes, cyclic heteroalkylenes,
polycyclic heteroalkylenes, ester groups, carbonyl groups,
carbonate groups, acetal groups, ketal groups, siloxyl groups,
carboxylic acid groups, carboxylic acid anhydride groups,
carboxylic acid anhydride half-ester groups, ether groups, amide
groups, carbamate groups, thioether groups, fluorinated linear
alkylenes, fluorinated branched alkylenes, fluorinated cyclic
alkylenes, polycyclic alkylenes, fluorinated linear
heteroalkylenes, fluorinated branched heteroalkylenes, fluorinated
cyclic heteroalkylenes, fluorinated polycyclic heteroalkylenes,
fluorinated ester groups, fluorinated carbonyl groups, fluorinated
carbonate groups, fluorinated acetal groups, fluorinated ketal
groups, fluorinated siloxyl groups, fluorinated carboxylic acid
groups, fluorinated carboxylic acid anhydride groups, fluorinated
carboxylic acid anhydride half-ester groups, fluorinated ether
groups, fluorinated amide groups, fluorinated carbamate groups, and
fluorinated thioether groups; wherein R.sub.4 is selected from the
group consisting of a sulfonic acid group, a sulfinic acid group, a
carboxylic acid group and an --X.sub.4--Y.sub.4 group wherein
X.sub.4 is selected from the group consisting of linear alkylenes,
branched alkylenes, cyclic alkylenes, polycyclic alkylenes, linear
heteroalkylenes, branched heteroalkylenes, cyclic heteroalkylenes,
polycylic heteroalkylenes, ester groups, carbonyl groups, amide
groups, ether groups, thioether groups, carbonate groups, carbamate
groups, acetal groups, ketal groups and Y.sub.4 is selected from
the group consisting of a sulfonic acid group, a sulfinic acid
group, and a carboxylic acid group; wherein R.sub.5 is selected
from the group consisting of hydrogen, fluorine, a fluoroalcohol
group, a sulfonamide group, a phenolic group, a naphtholic group, a
carboxylic acid group and a sulfonic acid group and an
--X.sub.5--Y.sub.5 group wherein X.sub.5 is selected from the group
consisting of linear alkylenes, branched alkylenes, cyclic
alkylenes, polycyclic alkylenes, linear heteroalkylenes, branched
heteroalkylenes, cyclic heteroalkylenes, polycylic heteroalkylenes,
ester groups, carbonyl groups, amide groups, ether groups,
thioether groups, carbonate groups, carbamate groups, acetal
groups, ketal groups and Y.sub.5 is selected from the group
consisting of a fluoroalcohol group, a sulfonamide group, a
phenolic group, a naphtholic group, a carboxylic acid group and a
sulfonic acid group; and wherein R.sub.6 is selected from the group
consisting of hydrogen, fluorine, an acid-labile group, a
base-labile group, an acid-labile fluorinated group, a base-labile
fluorinated group, linear alkanes, branched alkanes, cyclic
alkanes, polycyclic alkanes, linear heteroalkanes, branched
heteroalkanes, cyclic heteroalkanes, polycylic heteroalkanes,
fluorinated linear alkanes, fluorinated branched alkanes,
fluorinated cyclic alkanes, fluorinated polycyclic alkanes,
fluorinated linear heteroalkanes, fluorinated branched
heteroalkanes, fluorinated cyclic heteroalkanes, fluorinated
polycylic heteroalkanes and an --X.sub.6--Y.sub.6 group wherein
X.sub.6 is selected from the group consisting of linear alkylenes,
branched alkylenes, cyclic alkylenes, polycyclic alkylenes, linear
heteroalkylenes, branched heteroalkylenes, cyclic heteroalkylenes,
polycylic heteroalkylenes, ester groups, carbonyl groups, amide
groups, ether groups, thioether groups, carbonate groups, carbamate
groups, acetal groups, ketal groups and Y.sub.6 is selected from
the group consisting of hydrogen, fluorine, an acid-labile group, a
base-labile group, an acid-labile fluorinated group, a base-labile
fluorinated group, linear alkanes, branched alkanes, cyclic
alkanes, polycyclic alkanes, linear heteroalkanes, branched
heteroalkanes, cyclic heteroalkanes, polycylic heteroalkanes,
fluorinated linear alkanes, fluorinated branched alkanes,
fluorinated cyclic alkanes, fluorinated polycyclic alkanes,
fluorinated linear heteroalkanes, fluorinated branched
heteroalkanes, fluorinated cyclic heteroalkanes, fluorinated
polycylic heteroalkanes.
[0004] A second aspect of the present invention is a method of
forming an image in a photoresist layer, (a) forming the
photoresist layer over a substrate; (b) forming a topcoat layer on
a top surface of the photoresist layer, the topcoat layer
comprising a first polymer and a second polymer, the second polymer
different from the first polymer, the second polymer miscible with
the first polymer, the first and second polymers of the topcoat
layer dispersing non-homogenously in a vertical direction
perpendicular to the top surface of the photoresist layer; (c)
forming a layer of immersion fluid between the topcoat layer and a
final lens element or window of an immersion lithography system;
(d) exposing the photoresist layer to radiation through a photomask
having opaque and clear regions, the opaque regions blocking the
radiation and the clear regions being transparent to the radiation,
the radiation changing the chemical composition of regions of the
photoresist layer exposed to the radiation, forming exposed and
unexposed regions in the photoresist layer; and (e) removing either
the exposed regions of the photoresist layer or the unexposed
regions of the photoresist layer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] The features of the invention are set forth in the appended
claims. The invention itself, however, will be best understood by
reference to the following detailed description of illustrative
embodiments when read in conjunction with the accompanying
drawings, wherein:
[0006] FIGS. 1A through 1C are partial cross-sectional views
illustrating a semiconductor manufacturing process according to the
present invention;
[0007] FIG. 2 is a diagram of an exemplary immersion
photolithographic system that may be used to process a
semiconductor wafer having a topcoat layer according to the present
invention;
[0008] FIG. 3 is a dissolution plot of exemplary topcoat
mixtures;
[0009] FIG. 4 is a dissolution plot of exemplary topcoat mixtures
on a photoresist layer; and
[0010] FIG. 5 is a contrast plot of exemplary topcoat mixtures on a
photoresist layer.
DETAILED DESCRIPTION OF THE INVENTION
[0011] FIGS. 1A through 1C are partial cross-sectional views
illustrating a semiconductor manufacturing process according to the
present invention. In FIG. 1A, a substrate 30 is provided. In one
example, substrate 30 is a semiconductor substrate. Examples of
semiconductor substrates include but are not limited to bulk
(single crystal) silicon wafers and silicon on insulator (SOI)
wafers. Formed on a top surface 35 of substrate 30 is an optional
antireflective coating (ARC) 40. In one example, ARC 40 is spin
applied and a post ARC apply bake (heated above room temperature to
remove most of the ARC solvent) is performed. If ARC 40 is used,
then formed on a top surface 45 of ARC 40 is a photoresist layer
50. Photoresist layer 50 may be formed over other layers formed
over substrate 30 as well or formed over substrate 30 itself A
photoresist is defined material that will either become soluble in
a developer or insoluble in a developer when exposed to actinic
radiation (e.g. light). In one example, the wavelength of the
actinic radiation is about 250 nm or less. In one example,
photoresist layer 50 is spin applied and a post photoresist apply
bake, also known as a pre-exposure bake or a pre-bake (heated above
room temperature to remove most of the photoresist solvent), is
performed. Next a polymeric topcoat layer 60 comprising two
polymers is formed on a top surface 55 of photoresist layer 50.
Topcoat layer 60 is then baked (heated above room temperature to
remove most of the topcoat casting solvent).
[0012] Prior to application (e.g., in liquid form from the bottle),
the two polymers are homogenously mixed. However, the two polymers
disperse non-homogenously during application of liquid topcoat to
top surface 55 of photoresist layer so the applied topcoat layer
has concentration gradients of the two polymers, one polymer being
attracted to the topcoat/photoresist interface (i.e., the bottom
surface of topcoat layer 60) and the other polymer being attracted
to the air/topcoat interface (i.e., the top surface of topcoat
layer 60). Even after baking, the polymer structure of topcoat
layer 60 will remain graded.
[0013] In FIG. 1B, a layer of immersion fluid 70 is formed over a
top surface 75 of topcoat layer 60 in an immersion photolithography
tool (see FIG. 2 and description infra). Examples of immersion
fluids include water, water with soluble chemical additives, a
hydrocarbon fluid, and water or hydrocarbon-based nano-particle
dispersions. Examples of nano-particles include but are not limited
to particles MgO, Al.sub.2O.sub.3, TiO.sub.2, HfO.sub.2 having
maximum dimensions no greater than about 10 nm. Light of a
wavelength to which photoresist layer 50 is sensitive is passed
through a photomask 80. Photomask 80 has clear regions 85 that
transmit the light and opaque regions 90 that block the light.
Exposure of photoresist layer 50 to light through photomask 80
forms unexposed regions 95A of photoresist layer 50 and exposed
regions 95B of photoresist layer 50. Exposed regions 95B are also
known as latent image regions. An optional post exposure bake
(heated above room temperature to drive the photoresist chemistry)
may be performed.
[0014] Although a positive photoresist is shown in FIG. 1B, the
present invention also works well with negative photoresist systems
or dual tone photoresist systems. The present invention is well
suited for use with chemically amplified resists. In negative
photoresist systems, the photoresist will develop away where it is
not exposed to light, so a photomask of polarity opposite to that
illustrated in FIG. 1B is required. Dual tone resists can act
either negatively or positively depending upon the developer system
used.
[0015] In FIG. 1C, substrate 30 is removed from the immersion
photolithography tool and photoresist layer 50 is developed to
remove exposed regions 95B (see FIG. 1B) and leave behind unexposed
regions 95A. In one example the developer comprises an aqueous
solution of a base such as tetramethylammonium hydroxide (TMAH).
Topcoat layer 60 (see FIG. 1B) is also removed by the developer. An
optional post development bake (heated above room temperature to
harden the photoresist images) may be performed.
[0016] FIG. 2 is a diagram of an exemplary immersion
photolithographic system that may be used to process a
semiconductor wafer having a topcoat layer according to the present
invention. In FIG. 2 an immersion lithography system 100 includes a
controlled environment chamber 105 and a controller 110. Contained
within controlled environment chamber 105 is a focusing mirror 115,
a light source 120, a first focusing lens (or set of lenses) 125, a
mask 130, an exposure slit 135, a second focusing lens (or set of
lenses) 140, a final focusing lens 145, an immersion head 150 and a
wafer chuck 155. Immersion head 150 includes a transparent window
160, a central chamber portion 165, a surrounding plate portion
170, an immersion fluid inlet 175A and an immersion fluid outlet
175B. An immersion fluid 180 fills central chamber portion 165 and
contacts a top surface 75 of topcoat layer 60 formed on a top
surface of photoresist layer 50 formed top surface of substrate 30.
Topcoat layer 60 comprises a mixture of two polymers as described
infra. Alternatively, an optional ARC layer may be formed between
substrate 30 and photoresist layer 50. In one example, immersion
fluid 180 includes water. Plate portion 170 is positioned close
enough to topcoat layer 60 to form a meniscus 190 under plate
portion 170. Window 160 must be transparent to the wavelength of
light selected to expose photoresist layer 50.
[0017] Focusing mirror 115, light source 120, first focusing lens
125, a mask 130, exposure slit 135, second focusing lens 140, final
focusing lens 145 and immersion head 150 are all aligned along an
optical axis 200 which also defines a Z direction. An X direction
is defined as a direction orthogonal to the Z direction and in the
plane of the drawing. A Y direction is defined as a direction
orthogonal to both the X and Z directions. Wafer chuck 155 may be
moved in the X and Y directions under the direction of controller
110 to allow formation of regions of exposed and unexposed
photoresist in photoresist layer 50. As an XY-stage moves, new
portions of topcoat layer 60 are brought into contact with
immersion fluid 180 and previously immersed portions of the topcoat
layer are removed from contact with the immersion fluid. Mask 130
and slit 135 may be moved in the Y direction under the control of
controller 110 to scan the image (not shown) on mask 130 onto
photoresist layer 50. In one example, the image on mask 130 is a
1.times. to a 10.times. magnification version of the image to be
printed and includes one or multiple integrated circuit chip
images.
[0018] When exposure is complete, substrate 30 is removed from
controlled environment chamber 105 without spilling immersion fluid
180. To this end, controlled environment chamber 105 also includes
a cover plate 205 that may be moved to first abut with wafer chuck
155 and then moved with the wafer chuck as the wafer chuck is moved
out of position from under immersion head 150, the cover plate
replacing the wafer chuck under immersion head 150.
[0019] An ideal topcoat material would exhibit the following
properties: (1) high contact angle with water (particularly a high
receding contact angle), (2) low or moderate contact angle with
photoresist developers such as aqueous tetramethylammonium
hydroxide (TMAH), (3) fast and uniform dissolution in the
developer, (4) contain functional groups (such as sulfonic acid) to
control photoresist profiles and reduce defects, (5) have a
sufficiently high glass transition temperature to minimize
inter-diffusion with the resist during various post-application and
post-exposure bakes, (6) be soluble in casting solvents that do not
dissolve photoresist materials, and (7) be relatively low cost
(e.g., include inexpensive monomers). Because many of these
requirements rely on optimizing two competing properties
simultaneously, it has been very difficult to develop an ideally
performing topcoat material.
[0020] The present invention is a non-homogenous (e.g., graded)
topcoat system in which a highly fluorinated polymer (class A
polymer) is blended with an acidic polymer (class B polymer). The
non-homogenous topcoat system includes a mixture of at least one
polymer of each of class A and class B, which are miscible with
each other and which can be cast on top of a photoresist layer
prior to immersion lithography. Instead of forming a homogeneous
layer or a micro-phase separated layer morphology, the polymer
mixture is designed such that the two polymers form a vertically
non-homogenous layer during casting. The relative quantity of A
type polymer varies in a vertical direction defined as
perpendicular to a top surface of the photoresist layer and the B
type polymer varies in the vertical direction. Each polymer
segregates to the interface for which it was designed. The lower
surface energy, more highly fluorinated class A polymer is at its
maximum molar concentration in the topcoat layer at the air (later
immersion fluid)/topcoat interface and at its minimum molar
concentration in the topcoat layer at the topcoat/photoresist
interface. The acidic class B polymer is at its minimum molar
concentration in the topcoat layer at the air (later immersion
fluid)/topcoat interface and at its maximum molar concentration in
the topcoat layer at the topcoat/photoresist interface. In one
example, the weight percentage of type A polymer is greater than
the weight percentage of type B polymer at the topcoat to
air/immersion fluid interface. In one example, the weight
percentage of type B polymer is greater than the weight percentage
of type A polymer at the topcoat to photoresist interface.
[0021] The ideal properties of the class A polymer are: (1)
includes a high fluorine content for surface energy control and
high water contact angles, (2) includes an acidic pendent group(s)
capable of being wet and de-protonated by aqueous base developer,
(3) a sufficient dissolution rate in aqueous base developer so as
to be easily removable (e.g., greater than about 5 nm/sec), and (4)
solubility in a solvent for casting solvent that does not dissolve
photoresist (e.g., an alcoholic or ethereal solvent).
[0022] The ideal properties of the class B polymer are: (1)
includes a highly acidic pendent group(s) (such as sulfonic acid)
for profile control, (2) includes an acidic pendent group(s)
capable of being wet and de-protonated by aqueous base developer,
(3) a sufficient dissolution rate in aqueous base developer so as
to be easily removable (e.g., greater than about 5 nm/sec), (4) a
lower fluorine content than the class A polymer, (5) a higher
affinity for photoresist than the class A polymer in order to drive
vertical polymer concentration gradients rather than dispersed
island formation, (6) compatibility with the photoresist layer
(e.g., will not cause resist scumming, t-topping, line collapse and
other defects), and (7) solubility in the same solvent as the class
A solvent. Topcoat compositions according to the embodiments of the
present invention advantageously require a dose of radiation to
form a developable image in a photoresist layer that is about equal
to a dose of radiation required to form a developable image in the
photoresist layer if the photoresist layer were covered by a layer
consisting only of the class B polymer.
[0023] An acidic group is defined as a group having a pK.sub.a less
than that of water. The pK.sub.a of water is slightly greater than
15 (as measured in water) or 31 (as measured in dimethylsulfoxide).
Preferable acidic groups have a pK.sub.a (negative log of the acid
dissociation constant) less than about 13 (as measured in water) or
24 (as measured in dimethylsulfoxide). A strongly acidic group is
defined as a group having a pK.sub.a of less than about 3 (as
measured in water) or 8 (as measured in dimethylsulfoxide). A
highly fluorinated polymer is defined as a polymer containing more
than about 25 percent by weight fluorine. A polymer with low
fluorine content is defined as a polymer containing less than about
15 percent by weight fluorine. A polymer with moderate fluorine
content is defined as a polymer containing between than about 15
percent by weight fluorine and about 25 percent by weight fluorine.
A fluoroalcohol is defined as an organic compound bearing a
hydroxyl group wherein one or more non-hydroxyl group hydrogen
atoms are replaced with fluorine atoms. The fluoroalcohol may be
comprised of a linear, branched, cyclic, polycyclic, or aromatic
structure. Many non-limiting examples of such fluoroalcohols may be
found in H. Ito "Chemical Amplification Resists for
Microlithography," Adv. Polym. Sci. 2005, 172, 37-245.
[0024] Class A polymers may be described as having the
structure:
A.sub.1-A.sub.2-A.sub.3 . . . A.sub.N (I);
[0025] wherein each monomer A.sub.1 through A.sub.N is
independently selected from the group of monomers consisting of
structures II, III and IV described infra. Structure I should not
be interpreted as meaning all polymers in a given sample of a class
A polymer have the same number of monomer units, but rather N can
vary between individual polymers. N could also be thought of as
being the average number of monomer units in a given sample of
class A polymers.
[0026] Class A polymers comprise one or more different monomers
selected from the group consisting of:
##STR00003##
[0027] wherein each Z.sub.1, Z.sub.2, and Z.sub.3 is independently
selected from the group consisting of linear alkylenes, branched
alkylenes, cyclic alkylenes, polycyclic alkylenes, linear
heteroalkylenes, branched heteroalkylenes, cyclic heteroalkylenes,
polycyclic heteroalkylenes, ester groups, carbonyl groups,
carbonate groups, acetal groups, ketal groups, siloxyl groups,
carboxylic acid groups, carboxylic acid anhydride groups,
carboxylic acid anhydride half-ester groups, ether groups, amide
groups, carbamate groups, thioether groups, fluorinated linear
alkylenes, fluorinated branched alkylenes, fluorinated cyclic
alkylenes, polycyclic alkylenes, fluorinated linear
heteroalkylenes, fluorinated branched heteroalkylenes, fluorinated
cyclic heteroalkylenes, fluorinated polycyclic heteroalkylenes,
fluorinated ester groups, fluorinated carbonyl groups, fluorinated
carbonate groups, fluorinated acetal groups, fluorinated ketal
groups, fluorinated siloxyl groups, fluorinated carboxylic acid
groups, fluorinated carboxylic acid anhydride groups, fluorinated
carboxylic acid anhydride half-ester groups, fluorinated ether
groups, fluorinated amide groups, fluorinated carbamate groups, and
fluorinated thioether groups;
[0028] wherein R.sub.1 is selected from the group consisting of a
fluoroalcohol group, a fluoroalcohol group protected with an
acid-labile group, a fluoroalcohol group protected with a
base-labile group, a fluoroalcohol group protected with an
acid-labile fluorinated group, a fluoroalcohol group protected with
a base-labile fluorinated group, and an --X.sub.1--Y.sub.1 group
wherein X.sub.1 is selected from the group consisting of linear
alkylenes, branched alkylenes, cyclic alkylenes, polycyclic
alkylenes, linear heteroalkylenes, branched heteroalkylenes, cyclic
heteroalkylenes, polycylic heteroalkylenes, ester groups, carbonyl
groups, amide groups, ether groups, thioether groups, carbonate
groups, carbamate groups, acetal groups, ketal groups and Y.sub.1
is selected from the group consisting of a fluoroalcohol group, a
fluoroalcohol group protected with an acid-labile group a
fluoroalcohol group protected with a base-labile group, a
fluoroalcohol group protected with an acid-labile fluorinated
group, and a fluoroalcohol group protected with a base-labile
fluorinated group;
[0029] wherein R.sub.2 is selected from the group consisting of
hydrogen, fluorine, a fluoroalcohol group, a sulfonamide group, a
phenolic group, a naphtholic group, a carboxylic acid group and a
sulfonic acid group and an --X.sub.2--Y.sub.2 group wherein X.sub.2
is selected from the group consisting of linear alkylenes, branched
alkylenes, cyclic alkylenes, polycyclic alkylenes, linear
heteroalkylenes, branched heteroalkylenes, cyclic heteroalkylenes,
polycylic heteroalkylenes, ester groups, carbonyl groups amide
groups, ether groups, thioether groups, carbonate groups, carbamate
groups, acetal groups, ketal groups and Y.sub.2 is selected from
the group consisting of a fluoroalcohol group, a sulfonamide group,
a phenolic group, a naphtholic group, a carboxylic acid group and a
sulfonic acid group;
[0030] wherein R.sub.3 is selected from the group consisting of
hydrogen, fluorine, an acid-labile group, a base-labile group, an
acid-labile fluorinated group, a base-labile fluorinated group,
linear alkanes, branched alkanes, cyclic alkanes, polycyclic
alkanes, linear heteroalkanes, branched heteroalkanes, cyclic
heteroalkanes, polycylic heteroalkanes, fluorinated linear alkanes,
fluorinated branched alkanes, fluorinated cyclic alkanes,
fluorinated polycyclic alkanes, fluorinated linear heteroalkanes,
fluorinated branched heteroalkanes, fluorinated cyclic
heteroalkanes, fluorinated polycylic heteroalkanes and an
--X.sub.3--Y.sub.3 group wherein X.sub.3 is selected from the group
consisting of linear alkylenes, branched alkylenes, cyclic
alkylenes, polycyclic alkylenes, linear heteroalkylenes, branched
heteroalkylenes, cyclic heteroalkylenes, polycylic heteroalkylenes,
ester groups, carbonyl groups, amide groups, ether groups,
thioether groups, carbonate groups, carbamate groups, acetal
groups, ketal groups and Y.sub.3 is selected from the group
consisting of hydrogen, fluorine, an acid-labile group, a
base-labile group, an acid-labile fluorinated group, a base-labile
fluorinated group, linear alkanes, branched alkanes, cyclic
alkanes, polycyclic alkanes, linear heteroalkanes, branched
heteroalkanes, cyclic heteroalkanes, polycylic heteroalkanes,
fluorinated linear alkanes, fluorinated branched alkanes,
fluorinated cyclic alkanes, fluorinated polycyclic alkanes,
fluorinated linear heteroalkanes, fluorinated branched
heteroalkanes, fluorinated cyclic heteroalkanes, fluorinated
polycylic heteroalkanes.
[0031] Class B polymers may be described as having the
structure:
B.sub.1-B.sub.2-B.sub.3 . . . B.sub.M (V);
[0032] wherein each monomer B.sub.1 through B.sub.N is
independently selected from the group of monomers consisting of
structures VI, VII and VIII described infra. Structure V should not
be interpreted as meaning all polymers in a given sample of a class
B polymer have the same number of monomer units, but rather M can
vary between individual polymers. M could also be thought of as
being the average number of polymer units in a given sample of
class B polymers.
[0033] Class B polymers comprise one or more different monomers
selected from the group consisting of:
##STR00004##
[0034] wherein each Z.sub.4, Z.sub.5, and Z.sub.6 is independently
selected from the group consisting of linear alkylenes, branched
alkylenes, cyclic alkylenes, polycyclic alkylenes, linear
heteroalkylenes, branched heteroalkylenes, cyclic heteroalkylenes,
polycyclic heteroalkylenes, ester groups, carbonyl groups,
carbonate groups, acetal groups, ketal groups, siloxyl groups,
carboxylic acid groups, carboxylic acid anhydride groups,
carboxylic acid anhydride half-ester groups, ether groups, amide
groups, carbamate groups, thioether groups, fluorinated linear
alkylenes, fluorinated branched alkylenes, fluorinated cyclic
alkylenes, polycyclic alkylenes, fluorinated linear
heteroalkylenes, fluorinated branched heteroalkylenes, fluorinated
cyclic heteroalkylenes, fluorinated polycyclic heteroalkylenes,
fluorinated ester groups, fluorinated carbonyl groups, fluorinated
carbonate groups, fluorinated acetal groups, fluorinated ketal
groups, fluorinated siloxyl groups, fluorinated carboxylic acid
groups, fluorinated carboxylic acid anhydride groups, fluorinated
carboxylic acid anhydride half-ester groups, fluorinated ether
groups, fluorinated amide groups, fluorinated carbamate groups, and
fluorinated thioether groups;
[0035] wherein R.sub.4 is selected from the group consisting of a
sulfonic acid group, a sulfinic acid group, a carboxylic acid group
and an --X.sub.4--Y.sub.4 group wherein X.sub.4 is selected from
the group consisting of linear alkylenes, branched alkylenes,
cyclic alkylenes, polycyclic alkylenes, linear heteroalkylenes,
branched heteroalkylenes, cyclic heteroalkylenes, polycylic
heteroalkylenes, ester groups, carbonyl groups, amide groups, ether
groups, thioether groups, carbonate groups, carbamate groups,
acetal groups, ketal groups and Y.sub.4 is selected from the group
consisting of a sulfonic acid group, a sulfinic acid group, and a
carboxylic acid group;
[0036] wherein R.sub.5 is selected from the group consisting of
hydrogen, fluorine, a fluoroalcohol group, a sulfonamide group, a
phenolic group, a naphtholic group, a carboxylic acid group and a
sulfonic acid group and an --X.sub.5--Y.sub.5 group wherein X.sub.5
is selected from the group consisting of linear alkylenes, branched
alkylenes, cyclic alkylenes, polycyclic alkylenes, linear
heteroalkylenes, branched heteroalkylenes, cyclic heteroalkylenes,
polycylic heteroalkylenes, ester groups, carbonyl groups, amide
groups, ether groups, thioether groups, carbonate groups, carbamate
groups, acetal groups, ketal groups and Y.sub.5 is selected from
the group consisting of a fluoroalcohol group, a sulfonamide group,
a phenolic group, a naphtholic group, a carboxylic acid group and a
sulfonic acid group; and
[0037] wherein R.sub.6 is selected from the group consisting of
hydrogen, fluorine, an acid-labile group, a base-labile group, an
acid-labile fluorinated group, a base-labile fluorinated group,
linear alkanes, branched alkanes, cyclic alkanes, polycyclic
alkanes, linear heteroalkanes, branched heteroalkanes, cyclic
heteroalkanes, polycylic heteroalkanes, fluorinated linear alkanes,
fluorinated branched alkanes, fluorinated cyclic alkanes,
fluorinated polycyclic alkanes, fluorinated linear heteroalkanes,
fluorinated branched heteroalkanes, fluorinated cyclic
heteroalkanes, fluorinated polycylic heteroalkanes and an
--X.sub.6--Y.sub.6 group wherein X.sub.6 is selected from the group
consisting of linear alkylenes, branched alkylenes, cyclic
alkylenes, polycyclic alkylenes, linear heteroalkylenes, branched
heteroalkylenes, cyclic heteroalkylenes, polycylic heteroalkylenes,
ester groups, carbonyl groups, amide groups, ether groups,
thioether groups, carbonate groups, carbamate groups, acetal
groups, ketal groups and Y.sub.6 is selected from the group
consisting of hydrogen, fluorine, an acid-labile group, a
base-labile group, an acid-labile fluorinated group, a base-labile
fluorinated group, linear alkanes, branched alkanes, cyclic
alkanes, polycyclic alkanes, linear heteroalkanes, branched
heteroalkanes, cyclic heteroalkanes, polycylic heteroalkanes,
fluorinated linear alkanes, fluorinated branched alkanes,
fluorinated cyclic alkanes, fluorinated polycyclic alkanes,
fluorinated linear heteroalkanes, fluorinated branched
heteroalkanes, fluorinated cyclic heteroalkanes, fluorinated
polycylic heteroalkanes.
[0038] In one example topcoat mixture, the class A polymer is a
terpolymer where R.sub.1 is selected to provide solubility in an
aqueous base developer and to provide low surface energy, R.sub.2
is selected to tune the solubility in aqueous base developer, and
R.sub.3 is selected to tune the surface energy and the class B
polymer is a terpolymer where R.sub.4 is a strongly acidic group,
R.sub.5 is a weak acidic group and R.sub.6 is selected to tune the
polarity of the class B polymer. As the examples below indicate,
topcoat mixtures according to the present invention may be mixtures
where the class A polymer is independently selected from the group
consisting of homopolymers, copolymers and terpolymers and the
class B polymer is independently selected from the group consisting
of single monomer polymers, copolymers and terpolymers, as two or
more of the properties imparted to the class A polymer by
individual R.sub.1, R.sub.2, R.sub.3 groups may be fulfilled by one
or two R groups and two or more of the properties imparted to the
class B polymer by individual R.sub.4, R.sub.5, R.sub.6 groups may
be fulfilled by one or two R groups.
[0039] In one example, the average molecular weight for class A and
class B polymers is between about 500 and about 200,000. In one
example, the average molecular weight for class A and class B
polymers is between about 1000 and about 20,000.
[0040] Casting mixtures may include, besides class A polymers and
class B polymers, casting solvents, surfactants, photoacid
generators (PAGs) and polymer bound PAGs.
[0041] The examples topcoat mixtures described infra, are intended
to provide those of ordinary skill in the art with a complete
disclosure and description of how to prepare and use the
compositions disclosed and claimed herein. The mixture of A and B
type polymers are dissolved in a solvent to form a casting
solution. The solvent may comprise one solvent or two or more
different volatile solvents. Casting solvents are not included in
total solids calculations. Further, stabilizers, surfactants and
other additives (if any) may be added to the casting solution. In
one example, surfactants comprise less than about 1 percent by
weight of the totals solids content of the casting solution. In one
example, stabilizers and other additives together comprise less
than about 10 percent by weight of the total solids content of the
casting solution. In a first example, type A and type B polymers
together comprise between about 5 percent by weight to about 10
percent by weight of the casting solution. In a second example,
type A and type B polymers together comprise between about 2
percent by weight to about 15 percent by weight of the casting
solution. In a third example, type A and type B polymers together
comprise up to about 30 percent by weight of the casting solution.
Casting solutions may be made by adding dry (e.g., in powder form)
type A and type B polymers to the casting solvent. Solvent
extraction may be used to purify type A and type B polymers and
then the solutions with the polymer (with or without a
concentration procedure) mixed together to form a simple casting
solution. Surfactants, stabilizers and other additives may be added
to the simple casting solution as solids or as solutions of
dissolved solids to form a more complex casting solution. It is
important to note that additives and impurities that will stop
formation of a vertically graded non-homogenous layer of type A and
B polymers are excluded from being included or added to the casting
solution.
[0042] Unless indicated otherwise, parts are parts by weight,
temperature is in .degree. C. and pressure is at or near
atmospheric.
3,5-Bis(1,1,1,3,3,3-hexafluoro-2-hydroxypropan-2-yl)cyclohexyl
methacrylate,
1-cyclohexyl-4,4,4-trifluoro-3-hydroxy-3-(trifluoromethyl)but-1-yl
methacrylate, and
2-(1,1,1,3,3,3-hexafluoro-2-hydroxypropan-2-yl)cyclohexyl
methacrylate were obtained from Central Glass (Japan).
Additionally, all the other starting materials were obtained
commercially or were synthesized using known procedures.
[0043] Where appropriate, the following techniques and equipment
were utilized in the examples: .sup.1H and .sup.13C NMR spectra
were obtained at room temperature on an Avance 400 spectrometer.
Thermo-gravimetric analysis (TGA) was performed at a heating rate
of 5.degree. C./min in N.sub.2 on a TA Instrument Hi-Res TGA 2950
Thermogravimetric Analyzer. Differential scanning calorimetry (DSC)
was performed at a heating rate of 10.degree. C./min on a TA
Instruments DSC 2920 modulated differential scanning calorimeter.
Molecular weights were measured in tetrahydrofuran (THF) on a
Waters Model 150 chromatograph relative to polystyrene standards.
IR spectra were recorded on a Nicolet 510 FT-IR spectrometer on a
film cast on a KBr plate. Film thickness was measured on a Tencor
alpha-step 2000 or Nanospec. A quartz crystal microbalance (QCM)
with a MAXTEC Inc. PLO-10 Phase lock oscillator was used to study
the dissolution kinetics of the resist films in an aqueous 0.26N
tetramethylammonium hydroxide (TMAH) solution (CD-26). Lithographic
evaluation was performed on a 0.6N 193 nm mini-stepper, dry
exposure tool or a 193 nm interferometric exposure tool.
[0044] Water contact angles were measured on an OCA video based
contact angle system from FDS Future Digital Scientific
Corporation, using the sessile drop method on polymer mixtures
after baking to drive out the casting solvent. The contact angle
reported is the angle between the solid surface on which the drop
is formed and the tangent to the drop surface at the drop
surface/solid surface interface. The advancing and receding contact
angles were measured using a tilting stage method. Presented static
contact angles are a calculated average of between 5 and 10
measurements of a 2 .mu.L deionized water drop. Static contact
angles are measured un-tilted, i.e., on a horizontal surface
parallel to the ground. Tilting contact angles are measured by
placing a 50 .mu.L drop of deionized water on the substrate. The
substrate is thereafter tilted in an increasingly vertical
direction (relative to the horizontal direction) until the droplet
starts moving. The advancing, receding, and tilt angles are
measured just before the drop starts moving. Presented advancing
and receding water contact angles are calculated from an average of
between 3 and 5 measurements.
[0045] One of the objectives of using a topcoat is to prevent
leaching of extractable components from the photoresist into the
immersion liquid. Extraction of resist components into water was
evaluated using WEXA (Water Extraction Apparatus, see R. D. Allen
et. al., J. Photopolym. Sci. & Tech., 2005, 18 (5), 615-619).
Selected materials in the present invention were set in contact
with water in a controlled reproducible manner (time, speed,
volume, contact area, etc.). The water was thereafter collected and
analyzed for extractable components by Exygen Research using
LC/MS/MS. Reported is the amount of sulfonate extractable
components originating from the PAG (photoacid generator) that is a
component of the resist. For ease of understanding, the amount is
reported as percent extractables measured using a topcoat covered
by the present invention as compared to without using a topcoat. In
all cases, the extractable components were much lower after the
addition of a topcoat to the resist.
[0046] Another objective of a topcoat is to control reflection of
the incident radiation at the immersion fluid/photoresist interface
(i.e., acting as a top anti-reflective coating). Control of the
reflectivity is achieved by tailoring the film thickness and
refractive indices (n and k) to minimize reflectivity (or reduce it
below an acceptable level) across the entire range of incident
angles experienced with that particular imaging system. Multiple
layer film stacks can be used to control reflectivity more
efficiently than a single layer system at larger incident angles;
however, it is difficult to create multi-layer polymer films due to
the need to find orthogonal solvent systems such that the coating
solvent of each layer will not dissolve the underlying previously
cast polymer layer. The graded film structure in the present
invention is ideal for controlling reflectivity as well if the
refractive indices of the Class A and Class B polymers are tailored
appropriately. For example, a Class A polymer with a refractive
index similar to that of the immersion fluid and a Class B polymer
with a refractive index to the photoresist would help minimize
reflection at the immersion fluid/topcoat interface and the
topcoat/photoresist interface, respectively. In addition, the
ratios of the two polymers and the overall film thickness can be
optimized to provide a good immersion topcoat with anti-reflective
properties.
EXAMPLES
[0047] A representative polymerization procedure for the Class A
and Class B polymers is as follows: to a 100 mL round-bottom flask,
monomer (1 equiv.), 2,2'-azobis(2-methylpropionitrile) (AIBN) (0.04
equiv.), 1-dodecanethiol (0.03 equiv.) were added. Anhydrous,
inhibitor-free tetrahydrofuran was added to afford about 25 percent
by weight solids solution. A reflux condenser with a rubber septum
was added and the oxygen was removed from the solution by three
sequential pump-backfill cycles using nitrogen and vigorous
stirring. The reaction was heated to reflux overnight. The reaction
mixture was concentrated under vacuum and a small amount of acetone
was added. The polymer solution was precipitated into a non-solvent
(typically, hexane or methanol). The polymer was isolated and
washed with excess non-solvent using a glass-fritted filter. The
polymer was dried under vacuum overnight between 60.degree. C. to
80.degree. C., after which time, it was allowed to cool to room
temperature under vacuum. In the examples that follow, the full
name, abbreviated name and structure of the polymer is given.
Example Polymer Structures
[0048] Examples 1 through 17 are class A polymers and examples 18
through 48 are class B polymers.
Example 1
Poly(1,1,1-trifluoro-2-(trifluoromethyl)-pentan-2-ol-4-yl
methacrylate) (iPrHFAMA) Comprises Repeat Units Having the
Structure
##STR00005##
[0049] Examples 2 and 3
Poly((1,1,1-trifluoro-2-(trifluoromethyl)-pentan-2-ol-4-yl
methacrylate)-co-(1,1,1,3,3,3-hexafluoropropan-2-yl methacrylate))
(iPrHFAMA/HFIPMA) Comprises Repeat Units Having the Structures
##STR00006##
[0050] Example 2
95 mer % (IX) and 5 mer %, (X)
Example 3
80 mer % (IX) and 20 mer %, (X)
[0051] Other polymers according to the present invention may
include any combination of Y mer % (IX) and Z mer % (X) wherein
Y=any number from 0 to 100 and Z=any number from 0 to 100 such that
Y+Z is greater than or equal to 50 and less than or equal to
100.
[0052] The structure of examples 2 and 3 should be interpreted as
representing a polymer A.sub.1-A.sub.2-A.sub.3 . . . A.sub.N where
A.sub.1 through A.sub.N are independently selected from the group
consisting of iPrHFAMA and HFIPMA repeat units but in the mer
percentages given for each example. A mer is defined as a chemical
repeat unit in the polymer. Mer fraction is defined as the number
of mers of a given repeat unit divided by the number of mers of all
repeat units in a polymer. Mer % is defined as the mer fraction
multiplied by 100. The total amount of all mers is thus 100 mer %.
(In example 1, there is only iPrHFAMA so 100 mer % of all repeat
units are iPrHFAMA.) For example 2, in the iPrHFAMA/HFIPMA
copolymer there are 95 mers of iPrHFAMA for every 5 mers of HFIPMA.
Thus example 2 is 95 mer % iPrHFAMA and 5 mer % HFIPMA. For example
3, in the iPrHFAMA/HFIPMA copolymer there are 80 mer of iPrHFAMA
for every 20 mers of HFIPMA mers. Thus example 3 is 80 mer %
iPrHFAMA and 20 mer % HFIPMA. These definitions are applicable to
all examples described infra with the proviso that for class B
polymers the general formula B.sub.1-B.sub.2-B.sub.3 . . . B.sub.N
should be used. Examples 1 through 17 are class A polymers and
examples 18 through 48 are class B polymers.
Example 4
Poly(1,1,1-trifluoro-2-(trifluoromethyl)-hexan-2-ol-4-yl
methacrylate) (EtiPrHFAMA) Comprises Repeat Units Having the
Structure
##STR00007##
[0053] Example 5
Poly(1,1,1-trifluoro-5-methyl-2-(trifluoromethyl)-hexan-2-ol-4-yl
methacrylate) (iPriPrHFAMA) Comprises Repeat Units Having the
Structure
##STR00008##
[0054] Examples 6 and 7
Poly((1,1,1-trifluoro-5-methyl-2-(trifluoromethyl)-hexan-2-ol-4-yl
methacrylate)-co-(2-(trifluoromethylsulfonamido)ethyl
methacrylate)) (iPriPrHFAMA/STAR) Comprises Repeat Units Having the
Structures
##STR00009##
[0055] Example 6
90 mer % (XII) and 10 mer % (XIII)
Example 7
80 mer % (XII) and 20 mer % (XIII)
[0056] Other polymers according to the present invention may
include any combination of Y mer % (XII) and Z mer % (XIII) wherein
Y=any number from 0 to 100 and Z=any number from 0 to 100 such that
Y+Z is greater than or equal to 50 and less than or equal to
100.
Example 8
Poly((1,1,1-trifluoro-5,5-dimethyl-2-(trifluoromethyl)-hexan-2-ol-4-yl
methacrylate)-co-(2-(trifluoromethylsulfonamido)ethyl
methacrylate)) (tBuiPrHFAMA/STAR) Comprises Repeat Units Having the
Structures
##STR00010##
[0057] Example 8
70 mer % (XIV) and 30 mer % (XII)
[0058] Other polymers according to the present invention may
include any combination of Y mer % (XIV) and Z mer % (XIII) wherein
Y=any number from 0 to 100 and Z=any number from 0 to 100 such that
Y+Z is greater than or equal to 50 and less than or equal to
100.
Example 9
Poly(1,1,1-trifluoro-2-(trifluoromethyl)-4-cyclohexyl-butan-2-ol-4-yl
methacrylate) (CHiPrHFAMA) Comprises Repeat Units Having the
Structure
##STR00011##
[0059] Example 10
Poly((1,1,1-trifluoro-2-(trifluoromethyl)-4-cyclohexyl-butan-2-ol-4-yl
methacrylate)-co-(1,1,1-trifluoro-2-(trifluoromethyl)-pentan-2-ol-4-yl
methacrylate)) (CHiPrHFAMA/iPrHFAMA) Comprises Repeat Units Having
the Structures
##STR00012##
[0060] Example 10
50 mer % (XV) and 50 mer % (IX)
[0061] Other polymers according to the present invention may
include any combination of Y mer % (XV) and Z mer % (IX) wherein
Y=any number from 0 to 100 and Z=any number from 0 to 100 such that
Y+Z is greater than or equal to 50 and less than or equal to
100.
Examples 11 and 12
Poly((1,1,1-trifluoro-2-(trifluoromethyl)-4-cyclohexyl-butan-2-ol-4-yl
methacrylate)-co-(2-(trifluoromethylsulfonamido)ethyl
methacrylate)) (CHiPrHFAMA/STAR) Comprises Repeat Units Having the
Structures
##STR00013##
[0062] Example 11
80 mer % (XV) and 20 mer % (XIII)
Example 12
70 mer % (XV) and 30 mer % (XIII)
[0063] Other polymers according to the present invention may
include any combination of Y mer % (XV) and Z mer % (XIII) wherein
Y=any number from 0 to 100 and Z=any number from 0 to 100 such that
Y+Z is greater than or equal to 50 and less than or equal to
100.
Example 13
Poly((1,1,1-trifluoro-2-(trifluoromethyl)-4-cyclohexyl-butan-2-ol-4-yl
methacrylate)-co-(methacrylic acid)) (CHiPrHFAMA/MAA) Comprises
Repeat Units Having the Structures
##STR00014##
[0064] Example 13
90 mer % (XV) and 10 mer % (XVI)
[0065] Other polymers according to the present invention may
include any combination of Y mer % (XV) and Z mer % (XVI) wherein
Y=any number from 0 to 100 and Z=any number from 0 to 100 such that
Y+Z is greater than or equal to 50 and less than or equal to
100.
Examples 14 and 15
Poly((1,1,1-trifluoro-2-(trifluoromethyl)-4-cyclohexyl-butan-2-ol-4-yl
methacrylate)-co-(3,5-bis(1,1,1,3,3,3-hexafluoroproan-2-ol-2-yl)cyclohex--
1-yl methacrylate)) (CHiPrHFAMA/BisHFACHMA) Comprises Repeat Units
Having the Structures
##STR00015##
[0066] Example 14
80 mer % (XV) and 20 mer % (XVII)
Example 15
70 mer % (XV) and 30 mer % (XVII)
[0067] Other polymers according to the present invention may
include any combination of Y mer % (XV) and Z mer % (XVII) wherein
Y=any number from 0 to 100 and Z=any number from 0 to 100 such that
Y+Z is greater than or equal to 50 and less than or equal to
100.
Example 16
Poly(1,1,1-trifluoro-2-(trifluoromethyl)-hexan-2-ol-4-yl
methacrylate)-co-(2-(methacryloyloxy)ethanesulfonic acid))
(EtiPrHFAMA/SEMA) Comprises Repeat Units Having the Structures
##STR00016##
[0068] Example 16
98 mer % (XI) and 2 mer %, (XIX)
[0069] Other polymers according to the present invention may
include any combination of Y mer % (IX) and Z mer % (XIX) wherein
Y=any number from 0 to 99.9, Z=any number from 0.1 to 100 such that
Y+Z is greater than or equal to 50 and less than or equal to
100.
Example 17
Poly((1,1,1-trifluoro-5-methyl-2-(trifluoromethyl)-hexan-2-ol-4-yl
methacrylate)-co-(2-(methacryloyloxy)ethanesulfonic
acid))-co-(2-(trifluoromethylsulfonamido)ethyl methacrylate))
(iPriPrHFAMA/SEMA/STAR) Comprises Repeat Units Having the
Structures
##STR00017##
[0070] Example 17
80 mer % (XII), 2 mer % (XIX) and 18 mer % (XIII)
[0071] Other polymers according to the present invention may
include any combination of W mer % (IV), Y mer % (XIX) and Z mer %
(XIII) wherein W=any number from 0 to 99.9, Y=any number from 0.1
to 99.9, Z=any number from 0 to 99.9 such that W+Y+Z is greater
than or equal to 50 and less than or equal to 100.
Examples 18 and 19
Poly((1,1,1-trifluoro-2-(trifluoromethyl)-pentan-2-ol-4-yl
methacrylate)-co-(2-acrylamido-2-methylpropane-1-sulfonic acid))
(iPrHFAMA/MVP) Comprises Repeat Units Having the Structures
##STR00018##
[0072] Example 18
97.5 mer % (IX) and 2.5 mer % (XVIII)
Example 19
95 mer % (IX) and 5 mer % (XVIII)
[0073] Other polymers according to the present invention may
include any combination of Y mer % (IX) and Z mer % (XVIII) wherein
Y=any number from 0 to 99.9 and Z=any number from 0.1 to 100 such
that Y+Z is greater than or equal to 50 and less than or equal to
100.
Examples 20-23
Poly((1,1,1-trifluoro-2-(trifluoromethyl)-pentan-2-ol-4-yl
methacrylate)-co-(2-(methacryloyloxy)ethanesulfonic acid))
(iPrHFAMA/SEMA) Comprises Repeat Units Having the Structures
##STR00019##
[0074] Example 20
99 mer % (IX) and 1 mer %, (XIX)
Example 21
97.5 mer % (IX) and 2.5 mer %, (XIX)
Example 22
95 mer % (IX) and 5 mer %, (XIX)
Example 23
92.5 mer % (IX) and 7.5 mer %, (XIX)
[0075] Other polymers according to the present invention may
include any combination of Y mer % (IX) and Z mer % (XIX) wherein
Y=any number from 0 to 99.9, Z=any number from 0.1 to 100 such that
Y+Z is greater than or equal to 50 and less than or equal to
100.
Examples 24-27
Poly((1,1,1-trifluoro-2-(trifluoromethyl)-pentan-2-ol-4-yl
methacrylate)-co-(2-(methacryloyloxy)ethanesulfonic
acid)-co-(methyl methacrylate)) (iPrHFAMA/SEMA/MMA) Comprises
Repeat Units Having the Structures
##STR00020##
[0076] Example 24
85 mer % (IX), 5 mer % (XIX) and 10 mer % (XX)
Example 25
75 mer % (IX), 5 mer % (XIX) and 20 mer % (XX)
Example 26
65 mer % (IX), 5 mer % (XIX) and 30 mer % (XX)
Example 27
55 mer % (IX), 5 mer % (XIX) and 40 mer % (XX)
[0077] Other polymers according to the present invention may
include any combination of W mer % (IX), Y mer % (XIX) and Z mer %
(XX) wherein W=any number from 0 to 99.9, Y=any number from 0.1 to
99.9, Z=any number from 0 to 99.9 such that W+Y+Z is greater than
or equal to 50 and less than or equal to 100.
Examples 28 and 29
Poly((1,1,1-trifluoro-2-(trifluoromethyl)-pentan-2-ol-4-yl
methacrylate)-co-(2-(methacryloyloxy)ethanesulfonic
acid)-co-(isobornyl methacrylate)) (iPrHFAMA/SEMA/IBOMA) Comprises
Repeat Units Having the Structures
##STR00021##
[0078] Example 28
75 mer % (IX), 5 mer % (XIX) and 20 mer % (XXI)
Example 29
55 mer % (IX), 5 mer % (XIX) and 40 mer % (XXI)
[0079] Other polymers according to the present invention may
include any combination of W mer % (IX), Y mer % (XIX) and Z mer %
(XXI) wherein W=any number from 0 to 99.9, Y=any number from 0.1 to
99.9, Z=any number from 0 to 99.9 such that W+Y+Z is greater than
or equal to 50 and less than or equal to 100.
Example 30
Poly((2-(trifluoromethylsulfonamido)ethyl
methacrylate)-co-(2-(methacryloyloxy)ethanesulfonic acid))
(STAR/SEMA) Comprises Repeat Units Having the Structures
##STR00022##
[0080] Example 28
95 mer % (XIII) and 5 mer % (XIX)
[0081] Other polymers according to the present invention may
include any combination of Y mer % (XIII) and Z mer % (XIX) wherein
Y=any number from 0 to 99.9 and Z=any number from 0.1 to 100 such
that Y+Z is greater than or equal to 50 and less than or equal to
100.
Examples 31-34
Poly((2-(trifluoromethylsulfonamido)ethyl
methacrylate)-co-(2-(methacryloyloxy)ethanesulfonic
acid)-co-(isobornyl methacrylate)) (STAR/SEMA/IBOMA) Comprises
Repeat Units Having the Structures
##STR00023##
[0082] Example 31
75 mer % (XIII), 5 mer % (XIX) and 20 mer % (XXI)
Example 32
55 mer % (XIII), 5 mer % (XIX) and 40 mer % (XXI)
Example 33
67.5 mer % (XIII), 2.5 mer % (XIX) and 30 mer % (XXI)
Example 34
57.5 mer % (XIII), 2.5 mer % (XIX) and 40 mer % (XXI)
[0083] Other polymers according to the present invention may
include any combination of W mer % (XIII), Y mer % (XIX) and Z mer
% (XXI) wherein W=any number from 0 to 99.9, Y=any number from 0.1
to 99.9, Z=any number from 0 to 99.9 such that W+Y+Z is greater
than or equal to 50 and less than or equal to 100.
Examples 35-36
Poly((2-(trifluoromethylsulfonamido)ethyl methacrylate)-co-(vinyl
sulfonic acid)-co-(isobornyl methacrylate)) (STAR/VSA/IBOMA)
Comprises Repeat Units Having the Structures
##STR00024##
[0084] Example 35
67.5 mer % (XIII), 2.5 mer % (XXII) and 30 mer % (XXII)
Example 36
57.5 mer % (XIII), 2.5 mer % (XXII) and 40 mer % (XXII).
[0085] Other polymers according to the present invention may
include any combination of W mer % (XII), Y mer % (XXII) and Z mer
% (XXI) wherein W=any number from 0 to 99.9, Y=any number from 0.1
to 99.9, Z=any number from 0 to 99.9 such that W+Y+Z is greater
than or equal to 50 and less than or equal to 100.
Examples 37-38
Poly((2-(trifluoromethylsulfonamido)ethyl methacrylate)-co-(vinyl
sulfonic acid)-co-(isobornyl methacrylate)) (STAR/VSA/IBOMA)
Comprises Repeat Units Having the Structures
##STR00025##
[0086] Example 37
67.5 mer % (XIII), 2.5 mer % (XXII) and 30 mer % (XXIII).
Example 38
57.5 mer % (XIII), 2.5 mer % (XXII) and 40 mer % (XXIII).
[0087] Other polymers according to the present invention may
include any combination of W mer % (XIII), Y mer % (XXII) and Z mer
% (XXIII) wherein W=any number from 0 to 99.9, Y=any number from
0.1 to 99.9, Z=any number from 0 to 99.9 such that W+Y+Z is greater
than or equal to 50 and less than or equal to 100.
Examples 39-40
Poly((methacrylic acid)-co-(2-(methacryloyloxy)ethanesulfonic
acid)-co-(isobornyl methacrylate)) (MAA/SEMA/IBOMA) Comprises
Repeat Units Having the Structures
##STR00026##
[0088] Example 39
60 mer % (XVI), 2.5 mer % (XIX) and 37.5 mer % (XXI)
Example 40
50 mer % (XVI), 2.5 mer % (XIX) and 47.5 mer % (XXI)
Example 41
40 mer % (XVI), 2.5 mer % (XIX) and 57.5 mer % (XXI)
Example 42
30 mer % (XVI), 2.5 mer % (XIX) and 67.5 mer % (XXI)
[0089] Other polymers according to the present invention may
include any combination of W mer % (XVI), Y mer % (XIX) and Z mer %
(XXI) wherein W=any number from 0 to 99.9, Y=any number from 0.1 to
99.9, Z=any number from 0 to 99.9 such that W+Y+Z is greater than
or equal to 50 and less than or equal to 100.
Examples 43-46
Poly((methacrylic acid)-co-(2-(methacryloyloxy)ethanesulfonic
acid)-co-(methyl methacrylate)) (MAA/SEMA/MMA) Comprises Repeat
Units Having the Structures
##STR00027##
[0090] Example 43
50 mer % (XVI), 2.5 mer % (XIX) and 47.5 mer % (XXIV)
Example 44
40 mer % (XVI), 2.5 mer % (XIX) and 57.5 mer % (XXIV)
Example 45
30 mer % (XVI), 2.5 mer % (XIX) and 67.5 mer % (XXIV)
Example 46
20 mer % (XVI), 2.5 mer % (XIX) and 77.5 mer % (XXIV)
[0091] Other polymers according to the present invention may
include any combination of W mer % (XVI), Y mer % (XIX) and Z mer %
(XXIV) wherein W=any number from 0 to 99.9, Y=any number from 0.1
to 99.9, Z=any number from 0 to 99.9 such that W+Y+Z is greater
than or equal to 50 and less than or equal to 100.
Examples 47-48
Poly((methacrylic acid)-co-(2-vinyl sulfonic acid)-co-(methyl
methacrylate)) (MAA/VSAA/MMA) Comprises Repeat Units Having the
Structures
##STR00028##
[0092] Example 47
30 mer % (XVI), 2.5 mer % (XXII) and 67.5 mer % (XXIV)
Example 48
20 mer % (XVI), 2.5 mer % (XXII) and 77.5 mer % (XXIV)
[0093] Other polymers according to the present invention may
include any combination of W mer % (XVI), Y mer % (XXII) and Z mer
% (XXIV) wherein W=any number from 0 to 99.9, Y=any number from 0.1
to 99.9, Z=any number from 0 to 99.9 such that W+Y+Z is greater
than or equal to 50 and less than or equal to 100.
[0094] TABLE I lists the properties of the exemplary Class A and
Class B polymers described supra.
TABLE-US-00001 TABLE I Dissolution .theta..sub.static
.theta..sub.advancing .theta..sub.receding .theta..sub.tilt Rate
Polymer Polymer Composition M.sub.n PDI [.degree.] [.degree.]
[.degree.] [.degree.] [nm/s] Class A 1 iPrHFAMA 4220 1.56 82.9 87.2
65.6 20.5 125 2 iPrHFAMA/HFIPMA 95:5 5790 1.44 85.4 87.6 67.6 18.0
45 3 iPrHFAMA/HFIPMA 80:20 5340 1.44 87.9 89.1 69.4 17.8 5.5 4
EtiPrHFAMA 5260 1.68 88.2 90.1 71.9 16.0 6.6 5 iPriPrHFAMA 6720
1.34 93.2 93.3 79.6 12.4 <0.1 6 iPriPrHFAMA/STAR 90:10 3990 1.61
90.7 92.2 74.7 15.5 0.9 7 iPriPrHFAMA/STAR 80:20 4430 1.67 89.6
92.1 72.9 18.0 10.4 8 tBuiPrHFAMA/STAR 70:30 2870 1.46 87.0 94.3
65.6 23.6 25 9 CHiPrHFAMA 5900 1.33 95.9 92.7 78.7 14.4 <0.01 10
CHiPrHFAMA/iPrHFAMA 50:50 6530 1.36 89.1 89.3 74.2 13.8 <0.1 11
CHiPrHFAMA/STAR 80:20 5630 1.29 91.8 91.2 73.5 15.4 <0.1 12
CHiPrHFAMA/STAR 70:30 6150 1.32 90.3 90.7 71.3 17.6 2.5 13
CHiPrHFAMA/MAA 90:10 4200 1.61 71.6 93.0 75.3 15.5 <0.1 14
CHiPrHFAMA/BisHFACHMA 80:20 6700 1.31 87.3 88.8 72.8 14.4 <0.1
15 CHiPrHFAMA/BisHFACHMA 70:30 6920 1.32 83.3 86.9 70.6 14.9 0.3 16
EtiPrHFAMA/SEMA 98:2 3851 1.59 83.2 89.5 66.9 22.6 14.0 17
iPriPrHFAMA/SEMA/STAR 80:2:18 3932 1.50 84.8 91.5 66.8 24.6 14.0
Class B 18 iPrHFAMA/MVP 97.5:2.5 24600 1.54 78.8 86.1 61.5 24.8 70
19 iPrHFAMA/MVP 95:5 15400 2.02 76.2 86.2 55.4 29.9 165 20
iPrHFAMA/SEMA 99:1 5260 1.41 79.9 90.1 65.7 20.9 -- 21
iPrHFAMA/SEMA 97.5:2.5 4940 1.35 78.2 89.9 61.9 23.2 -- 22
iPrHFAMA/SEMA 95:5/5 3480 1.28 75.9 89.9 55.6 30.9 -- 23
iPrHFAMA/SEMA 92:5/7.5 4260 1.28 76.6 83.7 55.6 26.3 280 24
iPrHFAMA/SEMA/MMA 85:5:10 3670 1.39 75.7 85.6 53.8 29.4 220 25
iPrHFAMA/SEMA/MMA 75:5:20 2540 1.42 75.2 85.5 53.0 30.4 150 26
iPrHFAMA/SEMA/MMA 65:5:30 2160 1.61 74.4 84.7 50.7 31.3 80 27
iPrHFAMA/SEMA/MMA 55:5:40 2800 1.38 73.5 84.7 49.9 32.7 50 28
iPrHFAMA/SEMA/IBOMA 75:5:20 5140 1.21 76.7 86.4 54.0 30.1 44 29
iPrHFAMA/SEMA/IBOMA 55:5:40 4386 1.37 78.2 88.6 54.0 32.1 0 30
STAR/SEMA 95:5 3382 1.37 72.8 83.1 38.1 41.8 3500 31
STAR/SEMA/IBOMA 75:5:20 3811 1.27 69.2 82.9 34.3 44.2 2220 32
STAR/SEMA/IBOMA 55:5:40 3867 1.30 67.7 81.6 29.3 47.9 525 33
STAR/SEMA/IBOMA 67.5:2.5:30 3550 1.67 73.0 83.4 42.1 37.9 570 34
STAR/SEMA/IBOMA 57.5:2.5:40 3600 1.68 73.9 83.6 44.0 36.2 170 35
STAR/VSA/IBOMA 67.5:2.5:30 5241 1.59 74.9 84.3 48.5 34.7 900 36
STAR/VSA/IBOMA 57.5:2.5:40 7495 1.29 73.3 82.9 42.5 38.4 780 37
STAR/VSA/HAdMA 67.5:2.5:30 5252 1.55 66.6 78.3 39.9 36.2 1600 38
STAR/VSA/HAdMA 57.5:2.5:40 5566 1.67 64.5 76.7 37.2 37.2 1400 39
MAA/SEMA/IBOMA 60:2.5:37.5 3820 1.53 -- -- -- -- 4850 40
MAA/SEMA/IBOMA 50:2.5:47.5 4200 1.56 -- -- -- -- swells 41
MAA/SEMA/IBOMA 40:2.5:57.5 3490 1.63 67.2 83.6 29.9 51.1 insol. 42
MAA/SEMA/IBOMA 30:2.5:67.5 3150 1.71 71.3 86.4 38.7 43.7 insol. 43
MAA/SEMA/MMA 50:2.5:47.5 2920 1.46 -- -- -- -- 5100 44 MAA/SEMA/MMA
40:2.5:57.5 3023 1.45 50.9 68.1 12.4 45.9 5000 45 MAA/SEMA/MMA
30:2.5:67.5 2540 1.35 -- -- -- -- 3775 46 MAA/SEMA/MMA 20:2.5:77.5
2650 1.37 54.1 72.2 20.7 45.4 860 47 MAA/VSA/MMA 30:2.5:67.5 6404
1.76 55.7 67.1 22.4 39.7 3760 48 MAA/VSA/MMA 20:2.5:77.5 5462 1.76
56.2 68.6 31.6 33.7 540
[0095] In Table I, the composition is in mer %, M.sub.n is the
number average molecular weight, PDI is the polydispersity index,
.theta..sub.advancing is measured from the front end of the drop
(i.e., the edge of the meniscus on the lower end of the tilted
stage where the drop will cover previously uncovered surface when
it starts sliding), .theta..sub.receding is measured from the rear
of the drop (i.e., the edge of the meniscus on the elevated side of
the tilted stage where the drop will uncover previously covered
surface when it starts sliding), .theta..sub.tilt is the maximum
stage angle before the drop moves, and dissolution rate is in 0.26N
tetramethylammonium hydroxide solution.
[0096] Blending conventional base-soluble fluorinated topcoat
polymers does not successfully create a graded topcoat film. All
examples 49 and higher are blended mixtures of class A and class B
polymers. In Table II, iPrHFAMA (Example 1) is used as a base
material with varying amounts of a highly fluorinated co-monomer
added to create high contact angle of class A polymers or a
sulfonic acid-containing co-monomer to create an acidic class B
polymer. The mixtures 49 through 55 were made by blending dry class
A and class B polymers together and then dissolving the dry mixture
in a casting solvent. The ratio (A:B) in the following tables is
the weight of polymer A to the weight of polymer B in the
mixture.
[0097] To quantify the extent of increased polymer concentration
gradients, the difference (.DELTA..theta..sub.receding) between the
experimentally determined receding contact angle and that
calculated from a theoretical homogeneous film formed from the same
two materials was calculated. The calculation was based on the
receding contact angles of the individual polymers and weighted by
their weight fractions per the equation (1):
.DELTA..theta..sub.receding=.theta.r.sup.expt-.theta.r.sup.homogeneousbl-
end=.theta.r.sup.expt-[w.sup.A.theta.r.sup.A+w.sup.B.theta.r.sup.B]
(1)
[0098] where .DELTA..theta..sub.receding is the difference between
the measured contact angle and that calculated for a homogeneous
film of class A and class B polymers;
[0099] .theta.r.sup.expt is the measured contact angle of the class
A and B polymer mixture;
[0100] w.sup.A is the weight fraction of class A polymer;
[0101] .theta.r.sup.A is the receding contact angle of class A
polymer.
[0102] w.sup.B is the weight fraction of class B polymer; and
[0103] .theta.r.sup.B is the receding contact angle of class B
polymer.
[0104] In terms of immersion lithography, it is desirable to have
significantly more class A polymer than class B polymer at the
immersion fluid/topcoat interface and to have less class A polymer
and more class B polymer at the topcoat/photoresist interface. The
more negative the value of .DELTA..theta..sub.receding, the more
class B than class A polymer is at the air (later immersion
fluid)/topcoat interface (the opposite of the desired condition), a
value of 0 for .DELTA..theta..sub.receding indicates no
preferential segregation of the class A polymer to the air (later
immersion fluid)/topcoat interface, while a positive value for
.DELTA..theta..sub.receding indicates preferential segregation of
the class A polymer to the air (later immersion fluid)/topcoat
interface (the desired condition).
[0105] The resulting topcoats in Table II exhibit receding contact
angles that are insignificantly different from that of homogeneous
materials as evidenced by the near zero values of
.DELTA..theta..sub.receding shown in Table II. High positive values
of .DELTA..theta..sub.receding indicate increased polymer
concentration gradients have occurred. The near zero values of
.DELTA..theta..sub.receding are because the similarly high levels
of fluorination (and similar surface energies) in the blend
polymers produce an insufficient driving force for one of the
polymers to preferentially enrich the surface of the drop. Although
contact angles in the topcoat are higher than that of the sulfonic
acid-containing polymer only, this approach will only afford
averaged contact angles in the topcoats with no possibility for
contact angles as high as the class A polymers. In addition, the
local concentration of acidic groups near the photoresist is
greatly diluted in a homogeneous film compared to a graded
film.
TABLE-US-00002 TABLE II Dissolution Ratio .theta..sub.static
.theta..sub.advancing .theta..sub.receding .theta..sub.tilt
.DELTA..theta..sub.receding Rate Example Class A Class B (A:B)
[.degree.] [.degree.] [.degree.] [.degree.] [.degree.] [nm/s] 1
iPrHFAMA -- -- 82.9 87.2 65.6 20.5 -- 125 2 iPrHFAMA:HFIPMA -- --
85.4 87.6 67.6 18.0 -- 45 (95:5) 3 iPrHFAMA:HFIPMA -- -- 87.9 89.1
69.4 17.8 -- 5.5 (80:20) 19 -- iPrHFAMA:MVP -- 76.2 86.2 55.4 29.9
-- 165 (95:5) 49 iPrHFAMA iPrHFAMA:MVP 1:1 78.6 85.8 61.5 21.0 +1.0
-- (95:5) 50 iPrHFAMA iPrHFAMA:MVP 7:3 80.5 87.3 60.7 24.5 -1.8 --
(95:5) 51 iPrHFAMA iPrHFAMA:MVP 9:1 81.2 87.3 65.3 20.5 +0.7 --
(95:5) 52 iPrHFAMA:HFIPMA iPrHFAMA:MVP 1:1 79.7 86.1 61.3 23.8 -0.2
-- (95:5) (95:5) 53 iPrHFAMA:HFIPMA iPrHFAMA:MVP 1:1 83.8 88.7 64.0
23.2 +1.6 -- (80:20) (95:5) 54 iPrHFAMA:HFIPMA iPrHFAMA:MVP 5:1
82.4 87.0 65.7 19.8 +0.1 -- (95:5) (95:5) 55 iPrHFAMA:HFIPMA
iPrHFAMA:MVP 5:1 87.1 89.2 68.0 19.1 +0.9 -- (80:20) (95:5)
Examples 49 through 55 measured on SiO.sub.2.
[0106] A greater mismatch in the degree of fluorination (and
surface energy) between the two polymers is required to provide
sufficient driving force for preferential segregation of the lower
surface energy component to the surface during film formation. The
effect of reducing fluorine content in class B polymers is shown in
Examples 56-58 of Table III. As the level of fluorine in the class
B polymer is decreased (by replacing some fluoroalcohol monomer
with methyl methacrylate), the values of
.DELTA..theta..sub.receding change from negative to positive. The
+2.3 value of .DELTA..theta..sub.receding for sample 58 indicates
that the class A polymer is slightly enriching the surface of the
drop, although this value is close to the error limit of the
contact angle measurements.
TABLE-US-00003 TABLE III Ratio .theta..sub.static
.theta..sub.advancing .theta..sub.receding .theta..sub.tilt
.DELTA..theta..sub.receding Example Class A Class B (A:B)
[.degree.] [.degree.] [.degree.] [.degree.] [.degree.] 10
CHiPrHFAMA/iPrHFAMA -- -- 89.1 89.3 74.2 13.8 -- (50:50) 23 --
iPrHFAMA/SEMA -- 76.6 83.7 55.6 26.3 -- (95:5) 25 --
iPrHFAMA/SEMA/MMA -- 75.2 85.5 53.0 30.4 -- (75:5:20) 27 --
iPrHFAMA/SEMA/MMA -- 73.5 84.7 49.9 32.7 -- (55:5:40) 56
CHiPrHFAMA/iPrHFAMA iPrHFAMA/SEMA 50:50 77.8 85.7 59.3 24.1 -5.6
(50:50) (95:5) 57 CHiPrHFAMA/iPrHFAMA iPrHFAMA/SEMA/MMA 50:50 79.4
87.0 61.1 23.5 -2.5 (50:50) (75:5:20) 58 CHiPrHFAMA/iPrHFAMA
iPrHFAMA/SEMA/MMA 50:50 81.9 88.1 64.3 22.0 +2.3 (50:50) (55:5:40)
Examples 56 through 58 measured on SiO.sub.2.
[0107] To further increase increased polymer concentration
gradients, a further reduction of the fluorine content in the class
B polymer is required; however, any further replacement of the
fluoroalcohol monomer with methyl methacrylate will result in a
material insoluble in aqueous TMAH developer. Table IV gives
examples of blends using lower fluorine content class B polymers.
Table IV gives examples of blends using lower fluorine content
class B polymers using a trifluoromethyl sulfonamide-containing
monomer (i.e., STAR), which has a more rapid dissolution rate in
developer and a lower fluorine content (and higher surface energy).
The high contact angle of CHiPrHFAMA (example 9) and
CHiPrHFAMA/iPrHFAMA (example 10) helps increase the overall contact
angle of the film; however, the low solubility of these polymers in
developer prevents them from being an ideal solution. Even if these
materials are blended with a high dissolution rate polymer such
that the blend dissolves (examples 59 and 64), these materials
might re-precipitate and redeposit elsewhere on the wafer causing
imaging defects. Dissolution rates of the individual polymer
components greater than about 5 nm/s are preferred to help prevent
these classes of defects. To ensure higher dissolution rates for
the class A polymers, CHiPrHFAMA was copolymerized with lower
contact angle but higher dissolution rate monomers such as STAR
(examples 11-12) or BisHFACHMA (examples 14-15). The results for
these blended topcoat films are shown in TABLE IV. While moderate
levels of surface enrichment of the class A polymer are achieved,
example 58 features an extremely large .DELTA..theta..sub.receding.
Of the four class A polymers in Table IV, CHiPrHFAMA/BisHFACHMA
(70:30) copolymer of example 58 has the highest level of
fluorination. Increasing the levels of fluorination in the class A
polymer is expected to further increase surface enrichment.
[0108] Examples 64-67 use only a small amount of the more expensive
(due to the more exotic fluorinated monomers) class A material in
the mixture. This offers the benefit of a lower overall material
cost for the topcoat system. However, the surface enrichment of the
class A materials is not sufficient to overcome the overwhelming
class B polymer content in the film and only modest enhancement of
contact angle is seen in the best case (example 65).
TABLE-US-00004 TABLE IV Ratio .theta..sub.static
.theta..sub.advancing .theta..sub.receding .theta..sub.tilt
.DELTA..theta..sub.receding Example Class A Class B (A:B)
[.degree.] [.degree.] [.degree.] [.degree.] [.degree.] 9 CHiPrHFAMA
-- -- 95.9 92.7 78.7 14.4 11 CHiPrHFAMA/STAR -- -- 91.8 91.2 73.5
15.4 -- (80:20) 12 CHiPrHFAMA/STAR -- -- 90.3 90.7 71.3 17.6 --
(70:30) 15 CHiPrHFAMA/BisHFACHMA -- -- 83.3 86.9 70.6 14.9 --
(70:30) 31 -- STAR/SEMA/IBOMA -- 69.2 82.9 34.3 44.2 -- (75:5:20)
59 CHiPrHFAMA STAR/SEMA/IBOMA 50:50 78.4 87.3 52.2 32.6 -4.3
(75:5:20) 60 CHiPrHFAMA/BisHFACHMA STAR/SEMA/IBOMA 50:50 82.9 86.9
65.6 19.6 +13.2 (70:30) (75:5:20) 61 CHiPrHFAMA/STAR
STAR/SEMA/IBOMA 50:50 83.3 89.2 58.6 28.4 +4.7 (80:20) (75:5:20) 62
CHiPrHFAMA/STAR STAR/SEMA/IBOMA 50:50 83.0 89.1 57.6 28.3 +4.8
(70:30) (75:5:20) 63 CHiPrHFAMA/STAR STAR/SEMA/IBOMA 50:50 81.9
89.6 58.2 28.4 +5.4 (70:30) (75:5:20) 64 CHiPrHFAMA STAR/SEMA/IBOMA
10:90 72.1 84.3 37.7 42.8 -1.0 (75:5:20) 65 CHiPrHFAMA/BisHFACHMA
STAR/SEMA/IBOMA 10:90 74.5 86.9 44.9 39.0 +7.0 (70:30) (75:5:20) 66
CHiPrHFAMA/STAR STAR/SEMA/IBOMA 10:90 71.6 85.1 37.7 43.1 -0.5
(80:20) (75:5:20) 67 CHiPrHFAMA/STAR STAR/SEMA/IBOMA 10:90 73.4
85.5 39.2 43.4 +1.2 (70:30) (75:5:20) Dissolution rates in nm/s for
examples 59, 60, 61, 62, 63, 64, 65, 66 and 67 are respectively,
175, 350, 20, 300, 300, 1675, 1975, 1840 and 2250. Examples 59
through 67 measured on SiO.sub.2 except 63 on photoresist (JSR
AR1682J).
[0109] To achieve greater polymer concentration gradients, the
amount of fluorinated mers in the class B polymer was reduced
further (from 75 mer % to 67.5 mer %) and the amount of sulfonic
acid-containing mer units was reduced (from 5 mer % to 2.5 mer %).
This also slightly reduces the amount of polar, hydrogen bonding
groups capable of slowing increased polymer concentration
gradients. More significantly, it is found that analogs of iPrHFAMA
with substituents with less carbon than cyclohexyl are capable of
similarly high receding contact angles. However, these materials
have significantly greater rates of dissolution in aqueous TMAH
developer. Using monomers with substituents like ethyl, isopropyl,
or t-butyl, less of the dissolution-enhancing (but contact angle
lowering) STAR monomer was required to obtain copolymers with
similar receding contact angles to CHiPrHFAMA/STAR. In fact,
EtiPrHFAMA (example 4) has both higher receding contact angle and
higher dissolution rate than iPrHFAMA/HFIPMA (80:20) (example
3).
[0110] Table V lists topcoat blends with high fluorine content
class A polymers and low fluorine content class B polymers. Table V
lists the properties of class A iPriPrHFAMA/STAR copolymers with
class B STAR/SEMA/IBOMA (67.5:2.5:30) terpolymers. All these
topcoat materials exhibit extremely strong surface enrichment of
the iPriPrHFAMA/STAR as indicated by the large
.DELTA..theta..sub.receding values. Similar results are obtained
when casting on bare silicon (examples 68-69) and on resist (JSR
AR1682J) (examples 72-73). Asymmetric blends (examples 70-71) show
slightly lower receding contact angles, although the small amount
of class A polymer seems even more effective in raising contact
angles in the resulting film (larger .DELTA..theta..sub.receding
values). Examples 74-77 have topcoat thicknesses between about 30
nm and about 120 nm.
TABLE-US-00005 TABLE V Ratio .theta..sub.static
.theta..sub.advancing .theta..sub.receding .theta..sub.tilt Example
Class A Class B (A:B) [.degree.] [.degree.] [.degree.] [.degree.]
.DELTA..theta..sub.receding [.degree.] 6 iPriPrHFAMA/STAR -- --
90.7 92.2 74.7 15.5 -- (90:10) 7 iPriPrHFAMA/STAR -- -- 89.6 92.1
72.9 18.0 -- (80:20) 33 -- STAR/SEMA/IBOMA -- 73.0 83.4 42.1 37.9
-- (67.5:2.5:30) 68 iPriPrHFAMA/STAR STAR/SEMA/IBOMA 50:50 91.6
92.7 72.9 17.8 +14.5 (90:10) (67.5:2.5:30) 69 iPriPrHFAMA/STAR
STAR/SEMA/IBOMA 50:50 90.6 92.2 71.9 18.8 +14.4 (80:20)
(67.5:2.5:30) 70 iPriPrHFAMA/STAR STAR/SEMA/IBOMA 10:90 87.3 91.6
65.7 23.6 +20.3 (90:10) (67.5:2.5:30) 71 iPriPrHFAMA/STAR
STAR/SEMA/IBOMA 10:90 85.0 91.1 63.9 24.4 +18.7 (80:20)
(67.5:2.5:30) 72 iPriPrHFAMA/STAR STAR/SEMA/IBOMA 50:50 91.5 92.5
72.4 18.7 +14.0 (90:10) (67.5:2.5:30) 73 iPriPrHFAMA/STAR
STAR/SEMA/IBOMA 50:50 89.8 91.9 70.2 19.5 +12.7 (80:20)
(67.5:2.5:30) 74* iPriPrHFAMA/STAR STAR/SEMA/IBOMA 50:50 91.5 92.4
72.1 18.1 +13.7 (90:10) (67.5:2.5:30) 75* iPriPrHFAMA/STAR
STAR/SEMA/IBOMA 50:50 90.6 91.8 70.2 19.1 +12.7 (80:20)
(67.5:2.5:30) 76* iPriPrHFAMA/STAR STAR/SEMA/IBOMA 10:90 85.4 91.4
63.0 25.0 +17.6 (90:10) (67.5:2.5:30) 77* iPriPrHFAMA/STAR
STAR/SEMA/IBOMA 10:90 84.9 90.9 62.3 26.1 +17.1 (80:20)
(67.5:2.5:30) Dissolution rates in nm/s for examples 68, 69, 70,
71, 72 and 73 are respectively, 95, 160, 500, 495, 95 and 160.
Examples 68 through 70 measured on SiO.sub.2, examples 71 through
77 measured on photoresist (JSR AR1682J).
[0111] Other examples of graded topcoats using different class A
polymers are listed in Table VI. The iPrHFAMA-based class A
polymers are especially advantageous given the wide commercial
availability of the iPrHFAMA monomer.
TABLE-US-00006 TABLE VI Ratio .theta..sub.static
.theta..sub.advancing .theta..sub.receding .theta..sub.tilt Example
Class A Class B (A:B) [.degree.] [.degree.] [.degree.] [.degree.]
.DELTA..theta..sub.receding [.degree.] 1 iPrHFAMA -- -- 82.9 87.2
65.6 20.5 -- 3 iPrHFAMA:HFIPMA -- -- 87.9 89.1 69.4 17.8 -- (80:20)
4 EtiPrHFAMA -- -- 88.2 90.1 71.9 16.0 -- 33 -- STAR/SEMA/IBOMA --
73.0 83.4 42.1 37.9 -- (67.5:2.5:30) 34 -- STAR/SEMA/IBOMA -- 73.9
83.6 44.0 36.2 -- (57.5:2.5:40) 78 iPrHFAMA STAR/SEMA/IBOMA 50:50
82.1 86.0 64.1 19.6 +10.3 (67.5:2.5:30) 79 iPrHFAMA STAR/SEMA/IBOMA
75:25 82.7 85.2 65.9 17.6 +5.9 (67.5:2.5:30) 80 iPrHFAMA:HFIPMA
STAR/SEMA/IBOMA 50:50 88.1 89.1 67.1 20.2 +11.4 (80:20)
(67.5:2.5:30) 81 EtiPrHFAMA STAR/SEMA/IBOMA 50:50 88.8 90.1 72.3
15.8 +15.3 (67.5:2.5:30) 82 iPrHFAMA STAR/SEMA/IBOMA 50:50 82.1
85.4 64.2 19.7 +9.4 (57.5:2.5:40) Dissolution rates in nm/s for
examples 78, 79, 80, 81 and 82 are respectively, 480, 275, 120, 170
and 200. Examples 79 and 80 measured on SiO.sub.2, examples 78, 81
and 82 measured on photoresist (JSR AR1682J).
[0112] The graded film composition of two topcoats (examples 69 and
78) cast on top of resist (JSR AR1682J) are elucidated by secondary
ion mass spectroscopy (SIMS) and angle-rotated x-ray photoelectron
spectroscopy (XPS). In both systems, a clear enrichment (high
sulfonic acid, low fluorine) layer of the class B polymer at the
resist interface is seen by SIMS. Angle-rotated x-ray photoelectron
spectroscopy was used to probe the surface (top 5 nm) composition
of the same two graded topcoats. XPS shows that both topcoats have
a distinct surface-enrichment layer of the more fluorinated class A
polymer that is several nanometers thick. The extent of enrichment
calculated from the average of the various elemental signatures as
a function of depth for these two materials is shown in Table VII.
Both materials show that the surface composition is roughly 80% of
the class A polymer. This is not far below that suggested by the
water contact angles.
TABLE-US-00007 TABLE VII Example Material Angle [.degree.] CH CF
N.sub.1s O.sub.1s F.sub.1s S.sub.metal S.sub.oxide % Class A 1
iPrHFAMA 10 39.9 8.5 0.0 15.6 36.0 0.0 0.0 100 (2.5 nm) 45 43.8 8.4
0.0 16.0 31.9 0.0 0.0 100 (5.0 nm) 7 iPriPrHFAMA/STAR 10 42.9 7.1
1.1 15.4 32.5 0.1 0.9 100 (80:20) 45 45.0 6.6 1.3 16.3 29.9 0.2 0.9
100 33 STAR/SEMA/IBOMA 10 50.4 3.4 4.7 20.7 16.1 0.1 4.6 --
(67.5:2.5:30) 45 53.1 2.7 4.6 21.7 13.8 0.1 4.0 -- 69
iPriPrHFAMA/STAR & 10 46.1 6.7 1.7 16.1 27.7 0.2 1.7 81.3
STAR/SEMA/IBOMA 45 50.5 5.1 2.6 17.2 22.5 0.2 1.9 67.3 78 iPrHFAMA
& 10 42.4 7.6 1.1 16.0 31.8 0.2 0.9 77.9 STAR/SEMA/IBOMA 45
47.6 6.4 1.7 17.0 25.9 0.1 1.3 59.8 CH, CF, N.sub.1s, O.sub.1s,
F.sub.1s, S.sub.metal and S.sub.oxide are atomic percent. CF are
fluorinated carbons (i.e., CF.sub.3), CH are all other carbons.
[0113] It is advantageous to remove fluorine from the class B
polymer entirely, from both a cost (fluorinated monomers are
generally more expensive) as well as a phase-separation
(fluorinated groups are low surface energy substituents)
perspective. Fluorine-free class B polymers were developed by
replacing trifluoromethyl sulfonamide-containing methacrylate with
methacrylic acid. However, exceeding large amounts of methacrylic
acid are required (>50%) before the MAA/SEMA/IBOMA copolymer
dissolves without swelling (examples 39-42). Replacing the
hydrophobic IBOMA monomer with the more hydrophilic methyl
methacrylate allowed modest incorporation of methyl methacrylate to
afford fluorine-free class B polymers with linear dissolution in
aqueous TMAH developer. Blends with some of non-fluorine containing
class A polymers are shown in TABLE VII. These materials exhibited
higher contact angles when cast on silicon than on photoresist
(examples 83-86). This is likely due to the closer match between
the surface energy of the very hydrophilic class B polymer and bare
silicon than with the more hydrophobic photoresist. These materials
offer slightly lower receding contact angles than those outlined in
Table V and table VI.
TABLE-US-00008 TABLE VIII Ratio .theta..sub.static
.theta..sub.advancing .theta..sub.receding .theta..sub.tilt Example
Class A Class B (A:B) [.degree.] [.degree.] [.degree.] [.degree.]
.DELTA..theta..sub.receding [.degree.] 7 iPriPrHFAMA/STAR -- --
89.6 92.1 72.9 18.0 -- (80:20) 3 iPrHFAMA:HFIPMA -- 87.9 89.1 69.4
17.8 -- (80:20) 44 -- MAA/SEMA/MMA -- 50.9 68.1 12.4 45.9 --
(40:2.5:57.5) 46 -- MAA/SEMA/MMA -- 54.1 72.2 20.7 45.4 --
(20:2.5:77.5) 83 iPriPrHFAMA/STAR MAA/SEMA/MMA 50:50 88.9 92.0 65.6
24.6 +22.9 (80:20) (40:2.5:57.5) 84 iPrHFAMA:HFIPMA MAA/SEMA/MMA
50:50 85.8 90.0 60.8 28.7 +19.9 (80:20) (40:2.5:57.5) 85
iPriPrHFAMA/STAR MAA/SEMA/MMA 50:50 85.6 91.3 57.9 32.3 +15.2
(80:20) (40:2.5:57.5) 86 iPrHFAMA:HFIPMA MAA/SEMA/MMA 50:50 82.7
89.1 54.5 34.5 +13.6 (80:20) (40:2.5:57.5) 87 iPriPrHFAMA/STAR
MAA/SEMA/MMA 50:50 86.3 91.4 61.5 30.1 +14.7 (80:20) (20:2.5:77.5)
88 iPrHFAMA:HFIPMA MAA/SEMA/MMA 50:50 83.7 90.1 59.2 30.3 +14.2
(80:20) (20:2.5:77.5) Dissolution rates in nm/s for examples 83,
84, 85, 86, 87 and 88 are respectively, 1280, 1920, 1280, 1920, 220
and 120. Examples 83 and 84 on SiO.sub.2, examples 85-88 on
photoresist (JSR AR1682J).
[0114] A true test of the ability of a topcoat is its ability to
prevent leaching of photoacid generator (PAG) into water. The
normalized measurements of PAG leaching for the various graded
topcoat materials on JSR AR1682J resist are shown in Table IX. All
of the graded topcoats show that greater than 97% of the baseline
(resist without topcoat) extraction has been prevented by the
graded topcoat.
TABLE-US-00009 TABLE IX Sample Normalized PAG extraction AR1682J
(no topcoat) 100 Example 72 2.58 Example 73 1.40 Example 78 1.24
Example 81 0.62 Example 87 0.36
[0115] FIG. 3 is a dissolution plot of exemplary topcoat mixtures.
Dissolution rates of examples 68 (curve 250), 71 (curve 255), 69
(curve 260) and 68 (curve 265) as measured by a quartz crystal
microbalance are illustrated. All four samples show a linear
dissolution rate with no swelling, minimal dissolution lag, and no
scumming.
[0116] FIG. 4 is a dissolution plot of exemplary topcoat mixtures
on a photoresist layer. Curve 270 is exposed photoresist, curve 275
is example 69, curve 280 is example 73 exposed and curve 285 is
example 73 unexposed. The dissolution behavior of the topcoat
mixtures are unaffected when cast on photoresist. Just like the
contact angles, the dissolution rate is unaffected by the substrate
and exposure. The slight swelling peak (characteristic of the
photoresist) is unchanged when the graded topcoat is present. This
indicates that minimal inter-diffusion between the topcoat and
resist has occurred.
[0117] FIG. 5 is a contrast plot of exemplary topcoat mixtures on a
photoresist layer. The effects of the graded topcoat and its
individual component polymers on the contrast curve of the resist
(JSR AR1682J) are shown in FIG. 5. Curve 290 is photoresist, curve
295 is photoresist coated with example 33, curve 300 is photoresist
coated with example 73 and curve 305 is photoresist coated with
example 7. While water contact angles indicate the class A polymer
has segregated to the air interface, which polymer has segregated
to the resist interface can be probed by examination of the
contrast curve. When a class A polymer is cast onto the photoresist
resist, the dose required to fully expose the photoresist resist is
increased considerably. However, with the graded topcoat, the dose
required to expose the photoresist is about the same as when a
topcoat comprising only class B polymer is used. This indicates
that the class B polymer has segregated to the resist
interface.
[0118] It is advantageous for topcoat mixtures to have
.DELTA..theta..sub.receding equal to or greater than about
9.degree.. In some examples it is found that the weighted average
(weighted by the ratio A:B) of the .theta..sub.receding of the
class A and class B polymers of a given topcoat blend is less than
the .theta..sub.receding of the topcoat blend itself as illustrated
in Table X. It should also be noted that the .theta..sub.receding
of the class A polymer is greater than the .theta..sub.receding of
the class B polymer in any given topcoat blend.
TABLE-US-00010 TABLE X TOP- WEIGHT TOP- COAT Class A Class B
AVERAGE COAT .DELTA. EXAM- .theta..sub.receding
.theta..sub.receding A:B .theta..sub.receding .theta..sub.receding
.theta..sub.receding PLE [.degree.] [.degree.] RATIO [.degree.]
[.degree.] [.degree.] 60 70.6 34.3 50:50 52.5 65.6 13.2 68 74.7
42.1 50:50 58.4 72.9 14.5 69 72.9 42.1 50:50 57.5 71.9 14.4 70 74.7
42.1 10:90 45.4 65.7 20.3 71 72.9 42.1 10:90 45.2 63.9 18.7 72 74.7
42.1 50:50 58.4 72.4 14.0 73 72.9 42.1 50:50 57.5 70.2 12.7 74 74.7
42.1 50:50 58.4 72.1 13.7 75 72.9 42.1 50:50 57.5 70.2 12.7 76 74.7
42.1 10:90 43.4 63.0 17.6 77 72.9 42.1 10:90 45.2 62.3 17.1 80 74.7
42.1 50:50 58.4 67.1 8.7 81 66.9 42.1 50:50 54.5 72.3 18.8 82 65.6
44.0 50:50 54.8 64.2 9.4
[0119] The graded film structure in the present invention is ideal
for controlling reflectivity as well if the refractive indices of
the class A and class B polymers are tailored appropriately. For
example, a class A polymer with a refractive index similar to that
of the immersion fluid and a class B polymer with a refractive
index similar to the photoresist would help minimize reflection at
the immersion fluid/topcoat interface and the topcoat/photoresist
interface, respectively. In addition, the ratios of the two
polymers and the overall film thickness can be optimized to provide
a graded immersion topcoat with anti-reflective properties. The
optical properties of several class A and class B polymers are
shown in Table XI. In these examples, the refractive indices (n) of
the class A polymers (examples 1, 3 and 7) are close to that of the
immersion fluid (water, n=1.435 at 193 nm) and the class B polymers
(examples 33 and 46) are close to that of 193 nm photoresists
(typically n=1.6-1.7).
TABLE-US-00011 TABLE XI n k .alpha..sub.10 (193 nm) Example Polymer
(193 nm) (193 nm) [.mu.m.sup.-1] 1 iPriPrHFAMA 1.522 0.00439 0.1241
3 iPrHFAMA:HFIPMA 1.511 0.00411 0.1162 (80:20) 7 iPriPrHFAMA/STAR
1.548 0.00531 0.1501 (80:20) 33 STAR/SEMA/IBOMA 1.626 0.00914
0.2585 (67.5:2.5:30) 46 MAA/SEMA/MMA 1.661 0.00763 0.2156
(20:2.5:77.5)
[0120] The topcoat compositions of the present invention may be
used with other classes of immersion lithography tools, an example
of which is an immersion lithography tool wherein the immersion
fluid is dispensed onto the wafer from openings in the lens barrel
surrounding the lens.
[0121] The description of the embodiments of the present invention
is given above for the understanding of the present invention. It
will be understood that the invention is not limited to the
particular embodiments described herein, but is capable of various
modifications, rearrangements and substitutions as will now become
apparent to those skilled in the art without departing from the
scope of the invention. Therefore, it is intended that the
following claims cover all such modifications and changes as fall
within the true spirit and scope of the invention.
* * * * *