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Claims  |
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What is claimed is:
1. A method of creating patterned multilayer films for use in the
production of semiconductor circuits, and systems wherein at least one of
said multilayers is etch-resistant, comprising:
(a) applying an imaging layer of polymeric material over the surface of at
least one underlaying layer of polymeric material;
(b) using radiation to create a latent image within said imaging layer;
(c) developing said latent image to create a patterned layer of polymeric
material over the surface of said at least one underlaying layer of
polymeric material;
(d) altering said developed, patterned layer of polymeric material so that
it is capable of reacting with an organometallic reagent; and
(e) reacting said patterned layer of polymeric material with an
organometallic reagent in order to render said patterned layer of
polymeric material etch resistant.
2. A method of creating patterned multilayer films for use in the
production of semiconductor circuits and systems wherein at least one of
said multilayers is etch-resistant, comprising:
(a) applying an imaging layer of polymeric material over the surface of at
least one underlaying layer of polymeric material;
(b) using radiation to create a latent image within said imaging layer;
(c) altering said imaged layer in order to promote subsequent development
capabilities, and in order to enable the subsequently developed image to
sufficiently react with organometallic reagents, or for either of the
preceding purposes;
(d) developing said altered image layer to create a patterned layer of
polymeric material over the surface of said at least one underlaying layer
of polymeric material; and
(e) reacting said patterned layer of polymeric material with an
organometallic reagent in order to render said patterned layer of
polymeric material etch-resistant.
3. A method of producing multilayer films for use in the production of
semiconductor circuits and systems, wherein at least one of said
multilayers is etch-resistant, comprising:
(a) applying at least one layer of polymeric material to the surface of a
substrate;
(b) applying a layer of radiation-sensitive material over the surface of
said at least one layer of polymeric material;
(c) exposing at least a portion of said layer of radiation-sensitive
material to radiation, in order to create a latent image therein;
(d) reacting the irradiated portion of said radiation-sensitive material
with a reagent to alter its chemical structure or composition to produce a
material with different development characteristics from the irradiated
portion of said radiation-sensitive material;
(e) exposing at least the previously unexposed portions of the layer of
radiation-sensitive material to radiation;
(f) developing said layer of radiation-sensitive material to remove the
portions exposed in step (e), creating a pattern upon the surface of said
at least one layer of polymeric material; and
(g) reacting said developed, patterned layer with an organometallic reagent
in order to create an etch resistant material.
4. The method of claim 3 wherein the portions of said layer of radiation
sensitive material which are irradiated in step (c) contain functional
groups capable of reacting with said organometallic reagent both prior to
irradiation in step (c) and after the irradiation in step (e).
5. The method of claim 4 wherein said radiation-sensitive material is
comprised of a polymeric material selected from the group consisting of
novolaks and polyvinylphenols.
6. A method of producing multilayer films for use in the production of
semiconductor circuits and systems, wherein at least one of said
multilayers is etch-resistant, comprising:
(a) applying at least one layer of polymeric material to the surface of a
substrate;
(b) applying a layer of radiation-sensitive polymeric material containing
reactive functional groups in selected from the group consisting of OH,
COOH, NH, and SH, over the surface of said at least one layer of polymeric
material;
(c) exposing at least a portion of said layer of radiation-sensitive
material to radiation, in order to create a latent image therein;
(d) reacting the irradiated portion of said radiation-sensitive material to
alter its chemical structure and composition to produce a material with
development characteristics different from the irradiated portion of the
radiation-sensitive material;
(e) exposing at least the previously unexposed portions of the layer of
radiation-sensitive material to radiation;
(f) developing said latent image within said layer of radiation-sensitive
material to remove the portions exposed in step (e), creating a pattern
upon the surface of said at least one layer of polymeric material;
(g) reacting said developed, patterned layer with an organometallic reagent
in order to create an etch-resistant material.
7. A method of producing multilayer films for use in the production of
semiconductor circuits and systems, wherein at least one of said
multilayers is etch-resistant, comprising:
(a) applying at least one layer of polymeric material to a substrate;
(b) applying a layer of radiation-sensitive material, which is not capable
of significantly reacting with an organometallic reagent prior to
irradiation, over the surface of said at least one layer of polymeric
material;
(c) exposing at least a portion of said layer of radiation-sensitive
material to radiation, in order to create a latent image containing
reactive groups therein;
(d) developing said layer of radiation-sensitive material to create a
positive tone pattern upon the surface of said at least one layer of
polymeric material;
(e) exposing said developed, patterned layer of radiation-sensitive
material to radiation in order to generate reactive groups therein; and
(f) reacting said patterned, exposed layer of step (e) with an
organometallic reagent in order to create an etch-resistant material.
8. The method of claim 7 wherein said radiation-sensitive materials are
polymers containing functional components selected from the group
containing of o-nitrobenzene derivatives (which rearrange on exposure to
radiation to form alcohols, acids and amines), photo-fries reactive units
and diazoketones.
9. A method of producing multilayer films for use in the production of
semiconductor circuits and systems, wherein at least one of said
multilayers is etch-resistant, comprising:
(a) applying at least one layer of polymeric material to a substrate;
(b) applying a layer of radiation-sensitive material over the surface of
said at least one layer of polymeric material;
(c) exposing at least a portion of said layer of radiation-sensitive
material to radiation, in order to create a latent image therein;
(d) reacting the irradiated portion of said radiation-sensitive material in
order to produce a reacted material which is soluble in polar solvents or
in an aqueous base;
(e) developing said layer of radiation-sensitive material to create a
positive tone pattern upon the surface of said at least one layer of
polymeric material;
(f) exposing said developed, patterned layer of radiation-sensitive
material to radiation;
(g) reacting the patterned, irradiated layer of step (f) to create a
reacted material capable of reaction with an organometallic reagent; and
(h) reacting said patterned, layer of step (g) with an organometallic
reagent in order to create an etch-resistant material.
10. The method of claim 9 wherein said radiation-sensitive material is not
capable of significantly reacting with said organometallic reagent prior
to exposure to radiation.
11. The method of claim 10 wherein said radiation-sensitive material is
selected from the group consisting of sensitized poly(t-butyl
methacrylate) poly(t-butyloxycarbonyloxystyrene), and copolymers thereof.
12. A method of producing multilayer films for use in the production of
semiconductor circuits and systems, wherein at least one of said
multilayers is etch-resistant, comprising;
(a) applying at least one layer of polymeric material to a substrate;
(b) applying a layer of radiation-sensitive material over the surface of
said at least one layer of polymeric material;
(c) exposing at least a portion of said layer of radiation-sensitive
material to radiation;
(d) reacting the irradiated portion of said radiation-sensitive material in
order to produce a reacted material which is soluble in polar solvents or
in an aqueous base and which is capable of reacting with an organometallic
reagent;
(e) developing said layer of radiation-sensitive material to create a
negative tone pattern upon the surface of said at least one layer of
polymeric material; and
(f) reacting said developed layer with an organometallic reagent in order
to create an etch-resistant material.
13. The method of claim 12 wherein said radiation-sensitive material is not
capable of significantly reacting with said organometallic reagent prior
to exposure to radiation.
14. The method of claim 13 wherein said radiation-sensitive material is
selected from the group consisting of sensitized poly (t-butyl
methacrylate), poly (t-butyloxycarbonyloxystyrene), and copolymers
thereof.
15. The method of claims 1, 2, 3, 6, 7, 9 or 12 including an additional
step wherein the pattern in said etch-resistant, patterned layer is
transferred to at least one of said at least one layers of polymeric
material, using an oxygen plasma or reactive ion etching. |
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Claims |
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Description |
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BACKGROUND OF THE INVENTION
1. Technical Field
The present invention is concerned with multilayer films which are used in
the production of semiconductor circuits and systems. The films may become
a permanent part of the circuit or system; or, they may be used as masks
which are removed during processing, so that they do not become part of
the final circuit or system.
The present invention is particularly concerned with a method of producing
multilayer polymeric films wherein at least one of the layers is
etch-resistant.
2. Background Art
In the manufacture of semiconductor chips and systems, including packaging,
multilayer films are used as insulators, semiconductors, and conductors.
In the production of patterned devices, multilayer films are often used to
achieve pattern transfer.
An example of the pattern transfer application is the use of multilayer
films as masks during processing steps. Frequently the multilayer masking
films are polymeric, due to ease of use and the relatively low cost of
such materials. Depending on the pattern to be transferred, the multilayer
mask may be comprised of several different polymeric materials, each
material to accomplish a specific task. For example, a substrate to which
a mask is to be applied may exhibit a multitude of geometries,
necessitating the use of a planarizing layer prior to the layer of masking
which is patterned (the imaging layer), in order to provide accuracy
during patterning. Once the imaging layer has been patterned, it is
necessary to transfer the pattern through the planarizing layer to the
substrate. A current trend in the semiconductor industry is to use dry
etching techniques to transfer the pattern through the planarizing layer.
This is because conventional wet processes, which utilize solvent to
transfer the pattern in the imaging layer through the planarizing layer,
do not provide the anisotropic removal mechanism considered necessary to
achieve optimal dimensional control within the parameters of today's
systems.
Examples of dry-developable multilayer patterned films (resists) are
provided in U.S. Pat. Nos. 4,426,247 to Tamamura et al., 4,433,044 to
Meyer et al., 4,357,369 to Kilichowski et al., and 4,430,153 to Gleason et
al. In all of the above patents, one of the resist layers comprises a
silicon-containing polymer. The silicon-containing layer is imaged and
developed into a pattern. Subsequently, the patterned layer of resist is
exposed to an oxygen plasma or to reactive ion etching; this causes the
formation of silicon oxides in the patterned layer, which protect
underlaying polymeric layers and permit transfer of the pattern through
the underlying polymeric layers.
Recently, processes have been developed which permit selective conversion
of portions of a non-silicon-containing resist layer to a
silicon-containing, etch-resistant form. The resist layer is imaged but
not developed, and the latent image within the layer is reacted with an
organometallic reagent to incorporate an oxide-forming metal such as
silicon into the image. The latent image is then dry developable, and the
etch-resistant images, as well as underlying planarizing layers, can then
be dry etched using an oxygen plasma to simultaneously develop and
transfer the pattern through to the substrate below.
Examples of this latter method of obtaining dry-developable multilayer
resists are described in U.S. Pat. No. 4,552,833 to Ito et al., and in
U.S. patent application Ser. No. 679,527 (assigned to the assignee of the
present invention). The disclosures of U.S. Pat. No. 4,552,833 and U.S.
patent application are incorporated herein by reference.
However, the methods of creating dry-developable multilayer resists
described in the two referencies above provide a negative tone pattern,
and many practitioners within the semiconductor industry prefer to use a
positive tone pattern. In addition, the two methods described present
problems on application to novolak resist materials of the type most
commonly used in semiconductor industry lithography.
SUMMARY OF THE INVENTION
In accordance with the present invention, a method is provided for creating
multilayer films wherein at least one layer is a patterned, etch-resistant
layer, and wherein either positive or negative tone patterns can be
obtained. An etchant such as oxygen plasma can then be used to transfer
the pattern in the etch-resistant layer through any adjacent polymeric
layers shielded by the etch-resistant, patterned layer, such as (but not
limited to) underlying layers.
One of the preferred embodiments of the present invention discloses a
method of producing multilayer films for use in the production of
semiconductor circuits and systems, wherein at least one of the
multilayers is etch-resistant, comprising:
(a) applying an imaging layer of polymeric material over the surface of at
least one underlayer of polymeric material;
(b) creating a latent image within said imaging layer;
(c) developing said latent image to create a patterned layer of polymeric
material over the surface of said at least one underlayer of polymeric
material; and
(d) reacting said patterned layer of polymeric material with an
organometallic reagent in order to render said patterned layer of
polymeric material etch-resistant.
In the above embodiment, when the layer of radiation-sensitive material is
capable of reacting with the organometallic reagent prior to irradiation
and after development of the image, a positive tone pattern can be
obtained if the irradiated portion of the radiation-sensitive material can
be selectively removed in development step (c). The portion of the layer
of radiation-sensitive material remaining after step (c) can be directly
reacted with the organometallic reagent. A negative tone pattern can be
obtained if the irradiated portion of the radiation-sensitive material
becomes selectively resistant to the development process of step (c), so
that it is the non-irradiated portion of the layer which is removed upon
development. The irradiated portion of the layer remaining after
development can be subsequently reacted with the organometallic reagent.
In another preferred embodiment, wherein the image within the
radiation-sensitive material cannot be developed to provide the desired
pattern directly after irradiation, it is necessary to carry out an
additional reaction step prior to development of the image. In such case,
the method comprises the same steps (a) and (b) followed by a step (c) in
which the layer of radiation-sensitive material is further reacted in
order to alter its development characteristics, step (d) in which the
reacted image is developed to create a pattern upon the surface of the at
least one layer of polymeric material, and step (e) in which the developed
image is reacted with an organometallic reagent in order to create an
etch-resistant material. Again, either a positive or a negative tone
pattern can be obtained, depending upon the effect of steps (b), (c) and
(d) upon the particular radiation-sensitive material used.
In both of the above embodiments, the radiation-sensitive material is
capable of reacting with the organometallic reagent prior to irradiation
and after development of the image. The purpose of the radiation is to
create the image only, and the purpose of any additional reaction steps
following irradiation but prior to development of the image is to
distinguish the solubility characteristics of the originally irradiated
and non-irradiated areas, to provide the desired pattern tone upon
development.
There are additional embodiments of the present invention in which the
radiation-sensitive material is not capable of reacting with the
organometallic reagent prior to irradiation. In these embodiments,
radiation is required to initiate a reaction which alters the chemical
composition of the radiation-sensitive material so that it is capable of
reacting with the organometallic reagent. Depending on the
radiation-sensitive material, irradiation may be followed by an additional
reaction step in order to obtain a material capable of reacting with the
organometallic reagent.
In cases wherein the radiation-sensitive material is not capable of
reacting with the organometallic reagent prior to irradiation, and it is
desired to produce a positive tone pattern, the method of the present
invention comprises:
(a) applying an imaging layer of polymeric material over the surface of at
least one underlayer of polymeric material;
(b) creating a latent image within said imaging layer;
(c) developing said latent image to create a positive tone pattern over the
surface of said at least one underlayer of polymeric material;
(d) exposing the developed, patterned layer of radiation-sensitive material
to radiation; and
(e) reacting the developed, irradiated layer of step (d) with an
organometallic reagent in order to create an etch-resistant material.
The additional irradiation of the developed image in step (d) is necessary,
because the radiation-sensitive material remaining after development has
not been irradiated, and is not capable of reacting with the
organometallic reagent until after irradiation.
In cases wherein the radiation-sensitive material is capable of reacting
with the organometallic reagent only after irradiation, and it is desired
to obtain a negative tone pattern, the method of the present invention is
the same as above except that step (d) is excluded because it is no longer
necessary.
In other embodiments of the present invention, wherein the
radiation-sensitive material is not capable of reacting with the
organometallic reagent prior to irradiation, and wherein irradiation alone
is not sufficient to create either the desired development characteristics
or sufficient capability of reacting with the organometallic reagent, it
is necessary to carry out an additional reaction step. The additional
reaction step may be carried out before development to obtain the desired
development characteristics, or may be carried out before or after
development to obtain sufficient capability of reacting with the
organometallic reagent.
One example of the method of the present invention then comprises the same
steps (a) and (b) as described above, followed by a step (c) in which the
layer of radiation-sensitive material is further reacted in order to alter
its development characteristics, reactivity, or both. Step (c) is followed
by step (d) in which the reacted image is developed to create a pattern
upon the surface of the at least one layer of polymeric material, and step
(e) in which the developed image is reacted with an organometallic reagent
in order to create an etch-resistant material. Again, either a positive or
a negative tone pattern can be obtained, depending upon the
radiation-sensitive material used and the particular combination of
irradiation and development steps used.
In all of the above embodiments, once the etch-resistant material is
created, oxygen plasma (or any functionally equivalent dry etchant) can be
used to transfer the pattern in the etch-resistant layer through any
adjacent polymeric layers shielded by the etch-resistant patterned layer.
The method of the present invention can be used to provide multilayered,
patterned films for masking and for applications in which the patterned
films become a permanent part of the circuit or system. In the latter
case, it may be desirable to remove the patterned imaging layer subsequent
to pattern transfer, or to carry out an additional reaction subsequent to
pattern transfer which removes residual organometallic components and/or
metallic compounds.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1 through 6 depict a series of process steps for producing a
multilayered, patterned film with a positive tone pattern, wherein the
upper film layer is etch-resistant, and wherein the upper film (imaging)
layer contains reactive groups prior to irradiation and after development
of the image.
FIGS. 7 through 13 depict a series of process steps for producing a
multilayered, patterned film with a negative tone pattern, wherein the
upper film layer is etch-resistant, and wherein the upper film (imaging)
layer contains reactive groups prior to irradiation and after development
of the image.
FIGS. 14 through 21 depict a series of process steps for producing a
multilayered, patterned film with a positive tone pattern, wherein the
upper film layer is etch-resistant, and wherein the upper film (imaging)
layer is a radiation-sensitive material containing no reactive groups
prior to irradiation, and wherein an additional reaction step is required
to generate the desired form of active groups in the radiation-sensitive
material.
FIGS. 22 through 28 depict a series of process steps for producing a
multilayered, patterned film with a negative tone pattern, wherein the
upper film layer is etch-resistant, and wherein the upper film (imaging)
layer is a radiation-sensitive material containing no reactive groups
prior to irradiation, and wherein an additional reaction step is required
to generate active groups in the radiation-sensitive material.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Preferred embodiments include examples wherein the layer of
radiation-sensitive material is capable of reacting with the
organometallic reagent both prior to irradiation and after development of
the image. Radiation-sensitive materials meeting this requirement comprise
polymeric materials which contain reactive functional groups such as OH,
COOH, NH and SH. The form of the active groups may be altered during
subsequent process steps in some cases, but reactive groups must remain in
some form after development of the image. Typical polymeric materials of
this type include novolaks, polyvinylphenols, and polyacrylates. The
novolaks and polyvinylphenols are made radiation sensitive by addition of
sensitizers such as diazoquinone derivatives, diazides, or azides.
Multilayered films with a positive tone pattern, made using polymers of the
type described above, are created by the method shown in FIGS. 1-6.
Referring now to FIG. 1, a layer of a polymeric planarizing material 12 is
applied over the surface of a substrate 10. The polymeric planarizing
material need not contain any reactive groups; in fact, it is preferable
that it does not. In addition, it is preferable that the planarizing layer
be comprised of a material capable of withstanding high temperatures in
order to permit subsequent high temperature processing steps. Such high
temperature planarizing layers may be comprised of polyimides, or
commercially available novolak photoresists which have been baked at
temperatures higher than about 200.degree. C. C in order to provide
increased thermal stability and reduced capability to react with
organometallic reagents, or other thermally stable polymers. A layer of
radiation-sensitive material 14 is then applied over the surface of the
polymeric planarizing material. The surface of the radiation-sensitive
material 14 is then exposed to patterned radiation as shown in FIG. 2 in
order to create an image 16 therein, as shown in FIG. 3.
For purposes of this discussion, those to follow, and the claims made
herein, "radiation" should be interpreted to include both photon
(ultraviolet light from 150 nm-600 nm) and radiation emission sources such
as X-ray, electron beam, and ion beam. The particular radiation source
used depends on the sensitivity of the polymer and sensitizers being used.
The image is subsequently developed to provide a positive tone pattern as
shown in FIG. 4, by removal of the irradiated portions of the
radiation-sensitive layer. Often this removal is accomplished using a
solvent for the irradiated material, which solvent does not affect
non-irradiated material.
The developed pattern is now reacted with an organometallic reagent to
provide an etch-resistant pattern 18, as depicted in FIG. 5. Oxygen plasma
or reactive ion etching techniques can then be used to transfer the
pattern of the etch-resistant layer 18 through the underlying planarizing
layer 12, to the substrate surface 20, as shown in FIG. 6. Depending on
the method and conditions of etching, the planarizing layer can be etched
to have straight or undercut sidewalls as shown in the enlargement of FIG.
6.
The organometallic reagent used to render the radiation-sensitive material
etch-resistant can be of the type described in U.S. Pat. No. 4,522,833 to
Ito et al., and patent application Ser. No. 679,527, previously
incorporated by reference. The reagent may also be of the type described
in a patent application entitled "PLASMA-RESISTANT POLYMERIC MATERIAL,
PREPARATION THEREOF, AND USE THEREOF" by Babich et al., filed
simultaneously with this application, by the assignee of this application,
and which is incorporated herein by reference.
Multilayered films with a negative tone pattern are created by the method
shown in FIGS. 7-13. Referring now to FIG. 7, a layer of a polymeric
planarizing material 32 is applied over the surface of a substrate 30. It
is preferable that the planarizing material 32 not contain groups which
are reactive with the organometallic reagent. A layer of
radiation-sensitive material 34 is then applied over the surface of the
polymeric planarizing material 32. The surface of the radiation-sensitive
material 34 is then exposed to patterned radiation as shown in FIG. 8, in
order to create an image 36 therein, as shown in FIG. 9.
The image is subsequently developed by removal of the non-irradiated
portions 34 of the imaging layer, in order to create a negative tone
pattern. If the non-irradiated portions of the imaging layer 34 can be
removed by a technique which does not affect the irradiated material 36
(such as dissolved in a solvent or selectively etched away), the image can
be developed directly, to provide the structure shown in FIG. 11. If the
irradiated image 36 and the non-irradiated material 34 are affected in the
same manner by removal techniques, the irradiated image 36 must undergo an
additional reaction step (as shown in FIG. 10) to alter its chemical
structure or composition, so that the non-irradiated material 34 can be
removed by techniques which do not affect the irradiated, reacted image
38.
After development of the image as shown in FIG. 11, the developed pattern
38 is reacted with an organometallic reagent of the type previously
discussed, to create an etch-resistant material 40, as shown in FIG. 12.
Oxygen plasma or reactive ion etching techniques can then be used to
transfer the pattern of the etch-resistant layer 40 through the underlying
planarizing layer 32, to the substrate surface 42 as shown in FIG. 13.
Other preferred embodiments include examples wherein the
radiation-resistant material is not capable of reacting with the
organometallic reagent prior to irradiation. Two such systems for
producing multilayered, patterned films are described in U.S. Pat. No.
4,552,833 to Ito et al. and U.S. patent application Ser. No. 679,527,
previously incorporated by reference. The first of the above applications
describes the use of polymeric materials combined with sensitizers,
wherein the sensitizer generates an acid upon irradiation which is reacted
with the polymeric material to generate reactive hydrogens on the
polymeric material. Subsequently, the polymeric material is reacted with
the organometallic reagent. Typical polymeric materials used in this
method include poly(t-butyl methacrylate), poly
(t-butyloxycarbonyloxystyrene), and copolymers thereof. Additional
polymeric materials of this type are described in U.S. Pat. No. 4,491,628
to Ito et al., which is hereby incorporated by reference. The first
application also describes the use of polymers such as
poly(p-formyloxystyrene) which generate active hydrogens directly on
irradiation so that it is not necessary to use a sensitizer. The second
application describes additional systems which require no sensitizer. In
these systems, functional groups which become reactive upon irradiation
are attached to the desired polymer backbone. Typical of such functional
groups are o-nitrobenzyl derivatives (which rearrange on exposure to
radiation to form alcohols, acids, and amines), photo-fries reactive
units, and diazoketones.
Multilayered films with a positive tone pattern, made using sensitized
polymers of the type described above, are created by the method shown in
FIGS. 14-21. Referring now to FIG. 14, a layer of polymeric planarizing
material 52 is applied over the surface of a substrate 50. A layer of
radiation-sensitive material 54 is then applied over the surface of the
polymeric planarizing material 52. The surface of the radiation-sensitive
material 54 is then exposed to patterned radiation as shown in FIG. 15, in
order to create an image 56 therein, as shown in FIG. 16.
The image is subsequently developed by removal of the irradiated portions
56 of the imaging layer, in order to create a positive tone pattern. If
the irradiated image 56 can be removed by a technique which does not
affect the non-irradiated material 54 (such as dissolved in a solvent or
selectively wet etched away), the image can be developed directly to
provide the positive tone pattern shown in FIG. 18. If the irradiated
image 56 and the non-irradiated material 54 are affected in the same
manner by removal techniques, the irradiated image 56 must undergo an
additional reaction step, as shown in FIG. 17, to alter its chemical
structure or composition, so that it can be removed by techniques which do
not affect the non-irradiated material 54. The chemically altered,
irradiated image is depicted as 58 in FIG. 17. Subsequently, the
irradiated, chemically altered image 58 can be developed as shown in FIG.
18.
Since the imaging layer 54 remaining after development contains no reactive
groups, it must be irradiated as shown in FIG. 19 to create the reactive
groups, thus yielding an altered material 60. Again, if irradiation alone
does not generate groups capable of reacting with the organometallic
reagent, an additional reaction step may be required.
Subsequently, the altered imaging layer 60 is reacted with the
organometallic reagent to produce the etch-resistant patterned layer 62
shown in FIG. 20. Oxyqen plasma or reactive ion etching techniques can
then be used to transfer the pattern of the etch-resistant layer 62
through the underlying planarizing layer 52, to the substrate surface 64,
as shown in FIG. 21.
Multilayered films with a negative tone pattern are created by the method
shown in FIGS. 22-28. Referring now to FIG. 22, a layer of a polymeric
planarizing material 72 is applied over the surface of a substrate 70. A
layer of radiation-sensitive material 74 is then applied over the surface
of the polymeric planarizing material 72. The surface of the
radiation-sensitive material 74 is then exposed to patterned radiation as
shown in FIG. 23, in order to create an image 76 therein, as shown in FIG.
24.
The image is subsequently developed by removal of the non-irradiated
portions 74 of the imaging layer, in order to create a negative tone
image. If the non-irradiated material 74 can be removed by a technique
which does not affect the irradiated image 76, the image can be developed
directly to provide the structure shown in FIG. 26. If the irradiated
image 76 and the non-irradiated material 74 are affected in the same
manner by removal techniques, the irradiated image 76 must undergo an
additional reaction step, as shown in FIG. 25, to alter its chemical
structure or composition so that the non-irradiated material 74 can be
removed by techniques which do not affect the irradiated image 76. The
chemically altered, irradiated image is depicted as 78 in FIG. 25.
Subsequently, the chemically altered, irradiated image 78 can be developed
as shown in FIG. 26.
Since the imaged layer contains active groups created during earlier
process steps, the developed image 78 can be reacted with the
organometallic reagent as shown in FIG. 27, to create the etch-resistant,
patterned layer 80. Oxygen plasma or reactive ion etching techniques can
then be used to transfer the pattern of the etch-resistant layer 80
through the underlying planarizing layer 72, to the substrate surface 82
as shown in FIG. 28.
The various embodiments of the present invention provide for the creation
of either negative or positive images; they permit the use of resist
systems commonly used within the semiconductor industry; and they provide
for wet development of the imaging layer, which is preferable in terms of
cost of equipment required and processing rate.
EXAMPLES
Example 1
The first example is of a multilayer patterned film prepared using a
polymer containing reactive groups prior to irradiation and after
development of the image. The pattern produced was positive in tone and
the upper layer of the multilayer patterned film was dry-etch resistant.
The method used to prepare the multilayer patterned film was that depicted
in FIGS. 1-6.
A (planarizing) layer of preimidized polyimide 12 was applied to a silicon
wafer substrate 10 using standard spin coating techniques. The polyimide
had a weight average molecular weight of about 70,000. The .gamma.
-butyrolactone carrier for the polyimide was subsequently removed using a
250.degree. C. bake for a period of about 30 minutes. The thickness of the
polyimide layer 12 was about 2.0 micrometers.
An imaging layer 14 of a novolak polymer resist sensitized with a
diazoquinone derivative was applied by spin coating techniques over the
surface of the polyimide layer 12. The ethyl cellosolve acetate carrier
for the novolak-based resist was subsequently removed using an 85.degree.
C. bake for a period of about 30 minutes. The thickness of the
novolak-based layer was about 1.2 micrometers. The structure produced was
that shown in FIG. 1. The imaging layer 14 was imaged by contact printing,
using near ultraviolet radiation at a dose of about 25 mJ/cm.sup.2, as
shown in FIG. 2, and the resultant structure was that shown in FIG. 3 ,
wherein the image 16 is depicted.
The image was subsequently developed, using an aqueous base developer to
remove the irradiated image material 16, so that the resulting structure
was the positive tone pattern shown in FIG. 4. The developed image, as
determined by scanning electron microscope, was sharp, indicating that no
interlayer mixing had occurred between the planarizing layer 12 and the
imaging layer 14.
After development of the image, the structure shown in FIG. 4 was exposed
to the full output of a microlite 126 PC Photostabilizer (made by Fusion
Systems Corporation) for about 30 seconds, and then exposed to the vapors
of boiling hexamethyldisilazane (HMDS) for a period of about 45 minutes in
order to produce the silicon-containing etch-resistant layer 18 shown in
FIG. 5. Since the polyimide layer 12 contained no reactive groups, it was
assumed there was no reaction of the HMDS with the polyimide layer.
The pattern of the etch-resistant imaged layer 18 was subsequently
transferred through the polyimide layer 12 to the surface 20 of the
silicon wafer substrate 10 by oxygen reactive ion etching using a parallel
plate RIE tool.
Scanning electron micrographs of the two layer patterned film structure
atop the silicon wafer substrate show a layer of the etch-resistant
imaging material 18 capping the planarizing layer 12, wherein the
planarizing layer exhibits straight side walls, and wherein the exposed
substrate surface 20 exhibits no debris or apparent contamination.
Example 2
The second example is of a multilayer patterned film, prepared using a
polymer containing no reactive groups prior to irradiation. The pattern
created was positive in tone, and the upper layer of the patterned film
was dry-etch resistant. The method used to prepare the multilayer
patterned film was that depicted in FIGS. 14-21.
A layer of novolak polymeric material 52 was applied to the surface of a
silicon wafer 50 by standard spin coating techniques. The carrier for the
novolak was removed using an oven bake. The oven bake included a hard bake
at a temperature over 200.degree. C. to provide increased thermal
stability and to reduce the ability of the organometallic reagent (used in
subsequent process steps) to penetrate and react with functional groups
within the novolak.
An imaging layer of poly(t-butoxycarbonyloxystyrene) (PBOCS) containing
triphenylsulfonium hexafluoroarsenate (18.5% to the total solids) 54 was
then applied over the surface of the novolak layer 52 using standard spin
coating techniques. The cellosolve acetate carrier for the
PBOCS-triphenyl-sulfonium hexafluoroarsenate was subsequently removed
using a 100.degree. C. bake for about 15 minutes. The structure produced
was that shown in FIG. 14. The imaging layer 54 was then exposed to 254 nm
radiation at a dosage of about 5 mJ/cm.sup.2 as depicted in FIG. 15, in
order to create the image 56 as shown in FIG. 16.
The latent image 56 in the PBOCS was then converted to a form exhibiting
the desired reactive functionality 58 using an oven bake at about
100.degree. C. for a period of about two minutes, as represented by FIG.
17.
The converted image 58 was subsequently developed to provide the positive
tone image shown in FIG. 18 using an isopropyl alcohol developer solvent
with an exposure period of about 2 minutes, followed by an isopropyl
alcohol rinse.
Since the non-irradiated imaging layer 54 did not contain reactive groups
after the above process steps, it was necessary to irradiate this
material. The surface of the structure was flood exposed to about 5 mJ/cm
of 254 nm radiation, as depicted in FIG. 19, followed by a 100.degree. C.
bake for a period of about 2 minutes in order to convert the PBOCS polymer
to a form containing active hydrogens, represented by imaging layer 60.
The silicon wafer 50 with overlaying layers 52 and 60 was then placed in a
vacuum oven at about 110.degree. C. along with hexamethyldisilazane (HMDS)
vapors at a pressure greater than 50 torr for a period of about 10
minutes. FIG. 20 shows the imaging layer 60 converted to a
silicon-containing, etch-resistant material 62 after the reaction of the
reactive hydrogens within layer 60 with the HMDS.
The pattern within the imaging layer 62 was subsequently transferred
through the planarizing layer 52 to the surface 64 of the silicon wafer 50
by oxygen reactive ion etching using a Tegal parallel plate RIE tool.
Scanning electron micrographs of the two layer polymeric film structure
atop the silicon wafer show that the planarizing layer exhibits straight
sidewalls, and the surface 64 of the substrate 50 exhibits no debris.
The above process has also been demonstrated using PBOCS containing
hexafluroantimonate at concentrations as low as about 4% by weight to the
total solids. Additional resist compositions which combine a polymer
having recurrent acid labile pendant groups with a cationic photoinitiator
are described in U.S. Pat. No. 4,491,628 to Ito et al., previously
incorporated by reference.
Example 3
The third example is of a multilayer patterned film, prepared using a
polymer containing no reactive groups prior to irradiation. The pattern
was created was negative in tone, and the upper layer of the patterned
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