U.S. patent application number 09/765276 was filed with the patent office on 2001-06-07 for method for the formation of a planarizing coating film on substrate surface.
Invention is credited to Hirosaki, Takako, Iguchi, Etsuko, Kobayashi, Masakazu.
Application Number | 20010003068 09/765276 |
Document ID | / |
Family ID | 16032436 |
Filed Date | 2001-06-07 |
United States Patent
Application |
20010003068 |
Kind Code |
A1 |
Iguchi, Etsuko ; et
al. |
June 7, 2001 |
Method for the formation of a planarizing coating film on substrate
surface
Abstract
A method is disclosed for the formation of a planarizing coating
film on the surface of a substrate having a stepped level
difference under processing for the manufacture of semiconductor
devices. The inventive method capable of giving a planarizing
coating film of excellent planarity and good adhesion to the
substrate surface comprises the steps of: (a) coating the substrate
surface with a coating solution containing, as a film-forming
solute uniformly dissolved in an organic solvent, a
nitrogen-containing organic compound such as benzoguanamine and
melamine having, in a molecule, at least two amino and/or imino
groups each substituted for the nitrogen-bonded hydrogen atom by a
hydroxyalkyl group or an alkoxyalkyl group to form a coating layer;
(b) drying the coating layer by evaporating the organic solvent to
form a dried coating layer; and (c) subjecting the dried coating
layer to a baking treatment at a temperature in the range from 150
to 250.degree. C.
Inventors: |
Iguchi, Etsuko; (Tokyo-to,
JP) ; Hirosaki, Takako; (Kanagawa-ken, JP) ;
Kobayashi, Masakazu; (Chigasaki-shi, JP) |
Correspondence
Address: |
WENDEROTH, LIND & PONACK, L.L.P.
2033 K STREET N. W.
SUITE 800
WASHINGTON
DC
20006-1021
US
|
Family ID: |
16032436 |
Appl. No.: |
09/765276 |
Filed: |
January 22, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09765276 |
Jan 22, 2001 |
|
|
|
09337472 |
Jun 21, 1999 |
|
|
|
Current U.S.
Class: |
438/780 ;
257/E21.259; 438/781 |
Current CPC
Class: |
H01L 21/02118 20130101;
H01L 21/31055 20130101; H01L 21/02282 20130101; H01L 21/312
20130101 |
Class at
Publication: |
438/780 ;
438/781 |
International
Class: |
H01L 021/31; H01L
021/469 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 24, 1998 |
JP |
10-177,524 |
Claims
What is claimed is:
1. A method for the formation of a planarizing coating film on a
substrate surface which comprises the steps of: (a) coating the
substrate surface with a coating solution containing, as a
film-forming solute uniformly dissolved in an organic solvent, a
nitrogen-containing organic compound selected from the group
consisting of melamine, benzoguanamine, acetoguanamine, glycoluril,
urea, thiourea, guanidine, dicyandiamide, alkylene ureas and
succinamide having, in a molecule, at least two amino or imino
groups each substituted for the nitrogen-bonded hydrogen atom by a
hydroxyalkyl group or an alkoxyalkyl group to form a coating layer;
(b) drying the coating layer by evaporating the organic solvent to
form a dried coating layer; and (c) subjecting the dried coating
layer to a baking treatment at a temperature in the range from 150
to 250.degree. C.
2. The method for the formation of a planarizing coating film on a
substrate surface as claimed in claim 1 in which the alkyl group of
the hydroxyalkyl group and alkoxyalkyl group substituting the
nitrogen-containing organic compound has 1 to 4 carbon atoms.
3. The method for the formation of a planarizing coating film on a
substrate surface as claimed in claim 1 in which the alkoxy group
of the alkoxyalkyl group substituting the nitrogen-containing
organic compound has 1 to 4 carbon atoms.
4. The method for the formation of a planarizing coating film on a
substrate surface as claimed in claim 1 in which the film-forming
solute in the coating solution is a methoxymethylated
benzoguanamine or a methoxymethylated melamine.
5. The method for the formation of a planarizing coating film on a
substrate surface as claimed in claim 1 in which the organic
solvent of the coating solution is selected from the group
consisting of alkyleneglycol monoalkyl ethers and esters
thereof.
6. The method for the formation of a planarizing coating film on a
substrate surface as claimed in claim 1 in which the baking
treatment in step (c) is conducted for a length of time in the
range from 1 to 30 minutes.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a method for the formation
of a planarizing coating film on the surface of a substrate having
stepped level differences or, more particularly, to a method for
the formation of a planarizing coating film having an excellently
flat and smooth surface on a substrate surface having stepped level
differences by using a unique coating solution containing a
planarizing film-forming organic ingredient.
[0002] It is a remarkable trend in the modern technological field
of semiconductor devices that the electronic circuit wiring is
constructed on the surface of a substrate such as a semiconductor
silicon wafer with a higher and higher degree of integration
density with an increase in the fineness so that it is sometimes
the case that the circuit wiring layer is formed to have a
multilayered structure. As a consequence of such a multilayered
structure of the circuit wiring layer, the surface of the substrate
in an intermediate stage of processing with formation of a
multilayered circuit wiring layer or layers cannot be flat enough
but has a stepped level difference with raises and recesses on the
surface not to be suitable for a further photolithographic
patterning work thereon resulting in a great adverse influence on
the performance and reliability of the semiconductor device as the
final product. It is accordingly an established technique that a
photolithographic patterning work on a non-even surface is preceded
by the formation of a planarizing coating film having a flat and
uniform surface to cover the raised and recessed surface areas.
[0003] A great variety of coating solutions are proposed and
practically employed in the prior art for the formation of a
planarizing coating film. Besides the basic requirements for the
planarizing coating solutions that excellent planarization can be
obtained therewith by reliably and reproducibly filling up the
recesses in the extremely fine circuit wiring patterns with further
improved wettability to the fine raises and recesses, a planarizing
coating film in recent years is required to satisfy the etching
rate condition having adaptability to CVD films as a film also
having properties as an etch-back material.
[0004] Examples of the coating solutions for the formation of a
planarizing coating film under current use include a coating
solution of which the film-forming ingredient is a
hydrolysis-condensation product of an alkoxysilane compound or a
halogenosilane compound as disclosed in Japanese Patent Kokai
5-32410 and a coating solution containing a polymethyl
silsesquioxane resin and a tetraalkylammonium compound in an
organic solvent as disclosed in Japanese Patent Kokai 8-143818. The
former coating solution has problems that the coating film formed
therefrom, which is an inorganic silicon oxide film or a so-called
inorganic SOG film, is liable to cause crack formation when the
coating film has a large aspect ratio in addition to the
insufficient filling-up adaptability to very fine circuit wiring
patterns. The latter coating solution is also defective in respect
of incomplete planarization on a stepped substrate surface
consequently with a narrow effective focusing depth latitude in the
pattern-wise exposure of a photoresist layer formed on the
planarizing coating film to light leading to a decrease in the
pattern resolution and also in respect of the uncontrollable
variation of the etching rate which heavily depends on the residual
amount of the solvent and the conditions of the baking treatment
including the baking temperature.
[0005] In addition to the above described planarizing coating
solutions, polyimide resins are proposed as the film-forming
resinous ingredient in a coating solution for planarization. A
problem in a polyimide resin-based planarizing coating film is that
a baking treatment of the coating film sometimes results in a
decrease in the surface planarity of the coating film necessitating
a reflow treatment in addition to the problem in the filling-up
behavior inhibiting practical application of those resins.
SUMMARY OF THE INVENTION
[0006] The present invention accordingly has an object to provide a
novel and improved method for the formation of a planarizing
coating film on a substrate surface having stepped level
differences to be freed from the above described problems and
disadvantages in the prior art methods by using a conventional
coating solution for planarization.
[0007] Thus, the method of the present invention for the formation
of a planarizing coating film on a substrate surface comprises the
steps of:
[0008] (a) coating the substrate surface with a coating solution
containing, as a film-forming solute uniformly dissolved in an
organic solvent, a nitrogen-containing organic compound selected
from the group consisting of melamine, benzoguanamine,
acetoguanamine, glycoluril, urea, thiourea, guanidine,
dicyandiamide, alkylene ureas and succinamide having, in a
molecule, at least two amino and/or imino groups each substituted
for the nitrogen-bonded hydrogen atom by a hydroxyalkyl group or an
alkoxyalkyl group to form a coating layer;
[0009] (b) drying the coating layer by evaporating the organic
solvent to form a dried coating layer; and
[0010] (c) subjecting the dried coating layer to a baking treatment
at a temperature in the range from 150 to 250.degree. C.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0011] Examples of the amino or imino group-containing organic
nitrogen compound to be substituted by hydroxyalkyl and/or
alkoxyalkyl groups to give the solute compound in the coating
solution used in step (a) of the inventive method include melamine,
benzoguanamine, acetoguanamine, glycoluril, urea, thiourea,
guanidine, dicyandiamide, alkylene ureas, succinamide and the like.
Each of these nitrogen-containing organic compounds has two or more
of amino and/or imino groups bonded to the carbon atoms in a
molecule. It is essential that at least two of the amino/imino
groups are substituted for the nitrogen-bonded hydrogen atoms by
hydroxyalkyl and/or alkoxyalkyl groups. Examples of the alkyl group
to form the hydroxyalkyl or alkoxyalkyl group include those having
1 to 4 carbon atoms such as methyl, ethyl, n-propyl, isopropyl,
n-butyl, isobutyl, sec-butyl and tert-butyl groups. Examples of the
alkoxy groups to alkoxylate the above mentioned alkyl groups
include those having 1 to 4 carbon atoms such as methoxy, ethoxy,
n-propoxy and n-butoxy groups. The position of substitution on the
alkyl groups by the hydroxyl or alkoxy group is not particularly
limitative.
[0012] When the nitrogen-containing organic compound has two or
more amino/imino groups in a molecule, it is optional that a part
or all of the amino/imino groups are substituted by the
hydroxyalkyl and/or alkoxyalkyl groups. It is further optional that
the nitrogen-containing organic compound has, besides amino/imino
groups, other substituent groups such as nitro, cyano and carboxyl
groups and halogen atoms.
[0013] Particular examples of the nitrogen-containing organic
compound having amino/imino groups substituted by hydroxyalkyl
and/or alkoxyalkyl groups suitable as the solute in the coating
solution used in the inventive method include, though not
particularly limitative thereto, methoxymethylated melamines,
methoxymethylated-butoxymethylated melamines, butoxymethylated
melamines, carboxyl group-containing
methoxymethylated-isobutoxymethylated melamines, methoxymethylated
benzoguanamines, methoxymethylated-ethoxymethylated
benzoguanamines, methoxymethylated-butoxymethylated
benzoguanamines, butoxymethylated benzoguanamines, butoxymethylated
glycolurils, carboxyl group-containing
methoxymethylated-ethoxymethylated glycolurils, methylolated
benzoguanamines, methylolated glycolurils and the like, of which
methoxymethylated benzoguanamines and methoxymethylated melamines
are particularly preferable, although any of these compounds can be
used either singly or as a combination of two kinds or more
according to need.
[0014] The coating solution used in step (a) of the inventive
method is prepared by uniformly dissolving the above described
nitrogen-containing organic compound in a suitable organic solvent.
Examples of the organic solvents include, though not particularly
limitative thereto, monohydric alcohols such as methyl, ethyl,
propyl and butyl alcohols, polyhydric alcohols such as
ethyleneglycol, diethyleneglycol and propyleneglycol, derivatives
of polyhydric alcohols such as ethyleneglycol monomethyl ether,
ethyleneglycol monoethyl ether, ethyleneglycol monopropyl ether,
ethyleneglycol monobutyl ether, propyleneglycol monomethyl ether,
propyleneglycol monoethyl ether, propyleneglycol monopropyl ether,
propyleneglycol monobutyl ether, ethyleneglycol monomethyl ether
acetate, ethyleneglycol monoethyl ether acetate, propyleneglycol
monomethyl ether acetate and propyleneglycol monoethyl ether
acetate, and so on, of which alkyleneglycol monoalkyl ethers and
esters thereof such as propyleneglycol monomethyl ether and acetate
thereof are particularly preferable, although any of these organic
solvents can be used either singly or as a mixture of two kinds or
more according to need.
[0015] The concentration of the
hydroxyalkyl/alkoxyalkyl-substituted nitrogen-containing organic
compound in the coating solution used in step (a) of the inventive
method is not particularly limitative and can be selected in the
range of conventional concentrations depending on the particular
object of planarization although the concentration can be as high
as 85% by weight or even higher. This extremely high concentration
of the planarizing coating solution is in a remarkable contrast
with conventional planarizing coating solutions in which the
concentration of the film-forming ingredient can rarely exceed
about 20% by weight. The high concentration of the film-forming
ingredient in the coating solution is particularly advantageous
when a planarizing coating film having a large thickness is desired
by conducting a single coating work with the coating solution.
[0016] Step (a) of the inventive method is conducted by applying
the above described planarizing coating solution by a suitable
coating method of spinner coating, spray coating, dip coating and
the like to the surface of a substrate having stepped level
differences by providing, for example, a circuit wiring layer,
inorganic coating layer and so on. The amount of coating with the
planarizing coating solution naturally depends on the degree of the
stepped level differences on the substrate surface to accomplish
full planarization.
[0017] Step (a) of the inventive method for the formation of a
coating layer of the planarizing coating solution is followed by
step (b) in which the wet coating layer is freed from the solvent
by evaporating the solvent, if necessary, by heating at a
temperature not exceeding the boiling point of the solvent to give
a dried coating layer.
[0018] The thus obtained dried coating layer is then subjected in
step (c) of the inventive method to a baking treatment so as to
complete a cured planarizing coating film. The baking treatment is
conducted in an oxidizing atmosphere such as air at a temperature
in the range from 150 to 250.degree. C. The length of time taken
for this baking treatment naturally depends on the baking
temperature and other factors but a fully cured planarizing coating
film can be obtained usually by a baking treatment for 1 to 30
minutes.
[0019] Besides the above described film-forming solute, the.
planarizing coating solution used in the inventive method can be
admixed with various kinds of additives having compatibility or
miscibility with the film-forming solute including surface active
agents and crosslinking promoters with an object to further improve
the coating workability and the properties of the planarizing
coating film formed by using the solution. Examples of the
crosslinking promoters include carboxylic acids such as oxalic
acid, maleic acid, 2-hydroxybenzoic acid, 3,5-dinitrobenzoic acid
and 2,6-dihydroxybenzoic acid as well as a copolymeric acid which
is a copolymer of 2-hydroxybenzoic acid and p-xylene (SAX, a
commercial product by Mitsui Chemical Co.), ester compounds such as
a dialkylaminoalcohol p-toluenesulfonate,
2,2',4,4'-tetrahydroxybenzophenone and others. These crosslinking
promoters can be added to the coating solution in an amount not
exceeding 5% by weight based on the amount of the film-forming
ingredient. Examples of the surface active agents, which serve to
prevent striation in the coating layer, include fluorine-containing
ones sold under the trade names of Surflons SC-103 and SR-100 (each
a product by Asahi Glass Co.), EF-351 (a product by Tohoku
Fertilizers Co.), Florads Fc-135, Fc-98, Fc-430, Fc-431 and Fc-176
(each a product by Sumitomo 3M Co.) and the like. These surface
active agents can be added to the coating solution in an amount not
exceeding 0.2% by weight based on the amount of the film-forming
ingredient.
[0020] The substrate material provided on the surface with a
planarizing coating film according to the inventive method can be
subjected to an etch-back treatment so as to further improve the
surface planarity of the planarizing coating film. This is because,
since the planarizing coating film formed according to the
inventive method is a film of an organic material, the rate of
etching can readily be controlled in conducting the etching
treatment by modifying the composition of the etching gas so that
good matching can be accomplished with the underlying layer such as
an insulating layer and semiconductor layer. In addition to the
extremely high planarity, the thus obtained planarizing coating
film exhibits excellent properties such as full wettability to the
substrate surface having stepped level differences in an extremely
fine pattern.
[0021] In the following, the method of the present invention is
illustrated in more detail by way of Examples. In the following
Examples and Comparative Examples, the planarizing coating film was
evaluated in two ways as given below.
[0022] (1) Surface Condition of Planarizing Coating Film as
Cured
[0023] A cross section of the planarizing coating film as formed by
undertaking the baking treatment was examined by using a scanning
electron microscope.
[0024] (2) Surface Condition After Etch-Back
[0025] A cross section of the planarizing coating film after an
etch-back treatment over the whole surface was examined by using a
scanning electron microscope.
EXAMPLE 1
[0026] A planarizing coating solution was prepared by dissolving a
methoxymethylated benzoguanamine in propyleneglycol monomethyl
ether acetate in a concentration of 15% by weight.
[0027] A semiconductor silicon wafer provided with a circuit wiring
layer of aluminum was further provided thereon with an insulating
layer of titanium nitride as a first layer and then with a
semiconductor layer of polysilicon as the second layer. The
substrate material having multilayered coating to have a stepped
level difference of 0.20 .mu.m was coated on a spinner with the
above prepared coating solution under such a coating condition as
to form a uniform coating layer of 0.20 .mu.m thickness on a flat
substrate surface followed by a drying treatment by evaporation of
the solvent and a baking treatment in air at 180.degree. C. for 90
seconds to complete a cured planarizing coating film.
[0028] The planarity of the planarizing coating film as cured was
found complete without detecting any stepped level differences on
the surface. The planarity of the planarizing coating film after
the etch-back treatment was also complete.
EXAMPLE 2
[0029] The experimental procedure was substantially the same as in
Example 1 except that the planarizing coating solution was prepared
by using a methoxymethylated melamine instead of the
methoxymethylated benzoguanamine.
[0030] The planarity of the planarizing coating film as cured was
found complete without detecting any stepped level differences on
the surface. The planarity of the planarizing coating film after
the etch-back treatment was also complete.
EXAMPLE 3
[0031] The experimental procedure was substantially the same as in
Example 1 excepting for the replacement of propyleneglycol
monomethyl ether acetate as the solvent of the planarizing coating
solution with propyleneglycol monomethyl ether.
[0032] The planarity of the planarizing coating film as cured was
found complete without detecting any stepped level differences on
the surface. The planarity of the planarizing coating film after
the etch-back treatment was also complete.
EXAMPLE 4
[0033] The experimental procedure was substantially the same as in
Example 1 except that the planarizing coating solution was a 35% by
weight solution of the same methoxymethylated benzoguanamine in
propyleneglycol monomethyl ether acetate. This coating solution had
good storage stability without any noticeable changes in the
properties even after storage for 6 months at room temperature.
[0034] The planarity of the planarizing coating film as cured was
found complete without detecting any stepped level differences on
the surface. The planarity of the planarizing coating film after
the etch-back treatment was also complete.
EXAMPLE 5
[0035] The experimental procedure was substantially the same as in
Example 1 except that the planarizing coating solution was a 80% by
weight solution of the same methoxymethylated benzoguanamine in
propyleneglycol monomethyl ether acetate. This coating solution had
good storage stability without any noticeable changes in the
properties even after storage for 6 months at room temperature.
[0036] The planarity of the planarizing coating film as cured was
found complete without detecting any stepped level, differences on
the surface. The planarity of the planarizing coating film after
the etch-back treatment was also complete.
Comparative Example 1
[0037] The experimental procedure was substantially the same as in
Example 1 except that the planarizing coating solution was a
commercial product which was a 15% by weight solution of a novolak
resin in 2-heptanone.
[0038] The result of the examination of the surface planarity with
a scanning electron microscope was that the surface of the
planarizing coating film as cured had a stepped level difference of
0.04 .mu.m in conformity to the substrate surface. The surface
planarity of the coating film after the etch-back treatment was
also poor.
Comparative Example 2
[0039] A planarizing coating solution was prepared by dissolving 15
parts by weight of a polymethyl silsesquioxane resin having a
weight-average molecular weight of 3000 in 85 parts by weight of a
55:20:25 by weight mixture of ethyl alcohol, butyl alcohol and
methyl 3-methoxypropionate with further addition of 0.0001 part by
weight of tetramethylammonium hydroxide.
[0040] The same silicon substrate as used in Example 1 was coated
on a spinner with the thus prepared planarizing coating solution
followed by evaporation of the solvent on a hot plate at
180.degree. C. for 30 minutes and a baking treatment at 350.degree.
C. for 30 minutes to give a cured planarizing coating film having a
thickness of 0.35 .mu.m.
[0041] The result of the examination of the surface planarity with
a scanning electron microscope was that the surface of the
planarizing coating film as cured had a stepped level difference of
0.04 .mu.m in conformity to the substrate surface. The surface
planarity of the coating film after the etch-back treatment was
also poor.
* * * * *