U.S. patent application number 12/985761 was filed with the patent office on 2011-05-05 for phase-shift mask and method of forming the same.
This patent application is currently assigned to SAMSUNG ELECTRONICS CO., LTD.. Invention is credited to Sun-Young Choi, Hee-Bom Kim, Gi-Sung Yoon.
Application Number | 20110104593 12/985761 |
Document ID | / |
Family ID | 39527729 |
Filed Date | 2011-05-05 |
United States Patent
Application |
20110104593 |
Kind Code |
A1 |
Yoon; Gi-Sung ; et
al. |
May 5, 2011 |
PHASE-SHIFT MASK AND METHOD OF FORMING THE SAME
Abstract
In an attenuated phase-shift mask (PSM) and a method of forming
the same, a phase-shift layer and a light-shielding layer are
sequentially stacked on a transparent substrate. The phase-shift
layer and the light-shielding layer are sequentially removed from
the substrate, to form a light-shielding pattern including a first
opening and a phase-shift pattern including a second opening that
is connected to the first opening and partially exposes the
transparent substrate. Then, a transmitting portion is formed
through the light-shielding pattern by partially removing the
light-shielding pattern. The transmitting portion includes at least
one portion of the phase-shift pattern on which a transmittance
controller is formed. In one embodiment, the transmittance
controller comprises a metal having a high absorption coefficient,
and is formed through sputtering and diffusion processes.
Accordingly, the intensity deviation between 0.sup.th and 1.sup.st
order beams may be decreased, to thereby improve the processing
margin of the exposure process.
Inventors: |
Yoon; Gi-Sung; (Yongin-si,
KR) ; Kim; Hee-Bom; (Suwon-si, KR) ; Choi;
Sun-Young; (Seongnam-si, KR) |
Assignee: |
SAMSUNG ELECTRONICS CO.,
LTD.
Suwon-si
KR
|
Family ID: |
39527729 |
Appl. No.: |
12/985761 |
Filed: |
January 6, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12002275 |
Dec 13, 2007 |
7897299 |
|
|
12985761 |
|
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Current U.S.
Class: |
430/5 |
Current CPC
Class: |
G03F 1/32 20130101; G03F
1/68 20130101; G03F 1/80 20130101; G03F 1/54 20130101 |
Class at
Publication: |
430/5 |
International
Class: |
G03F 1/00 20060101
G03F001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 14, 2006 |
KR |
10-2006-0127625 |
Claims
1. A phase-shift mask (PSM), comprising: a transparent substrate
through which light passes; a light-shielding pattern that is
positioned on the transparent substrate and prevents the light from
being incident onto the transparent substrate, the light-shielding
pattern defining a transmitting portion through which the
transparent substrate is partially exposed and the light is
incident onto the transparent substrate; a phase-shift pattern that
is positioned on the transparent substrate exposed through the
transmitting portion, the phase-shift pattern shifting the phase of
the light that passes through the transmitting portion; and a
transmittance controller that is positioned at an upper portion of
the phase-shift pattern in the transmitting portion and controls
the transmittance of the light with respect to the phase-shift
pattern in the transmitting portion.
2. The PSM of claim 1, wherein the transmitting portion has a shape
corresponding to a circuit pattern that is to be transcribed onto a
semiconductor substrate for manufacturing a semiconductor
device.
3. The PSM of claim 1, wherein the phase-shift pattern comprises
molybdenum (Mo) and the light-shielding pattern comprises chromium
(Cr).
4. The PSM of claim 1, wherein the transmittance controller
includes a material selected from the group consisting of chromium
(Cr), molybdenum (Mo) and tungsten (W), and controls the
transmittance of the light passing through the phase-shift pattern,
to thereby decrease an intensity deviation between 0.sup.th and
1.sup.st order beams of the light.
5. The PSM of claim 1, wherein the light includes an argon fluoride
(ArF) excimer laser and the transmittance controller includes a
diffusion layer having a diffusion depth of about 100 nm to about
500 nm from a top surface of the phase-shift pattern.
6. The PSM of claim 5, wherein the phase-shift pattern has a
thickness of about 400 .ANG. to about 600 .ANG. from a surface of
the transparent substrate.
Description
RELATED APPLICATIONS
[0001] This application is a divisional application of U.S. patent
application Ser. No. 12/002,275, filed on Dec. 13, 2007, which
claims priority to Korean patent application number
10-2006-0127625, filed on Dec. 14, 2006 in the Korean Intellectual
Property Office, the contents of which applications are
incorporated herein in their entirety by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] Example embodiments of the present invention relate to a
phase-shift mask (PSM) and a method of forming the same. More
particularly, example embodiments of the present invention relate
to an attenuated PSM for minimizing an intensity difference between
a 0.sup.th order beam and a 1.sup.st order beam, and a method of
forming the same.
[0004] 2. Description of the Related Art
[0005] As semiconductor devices continue to become more highly
integrated, design rules for the devices are becoming gradually
reduced. so that the critical dimensions (CDs) of the semiconductor
devices are currently becoming scaled down to about 0.07 .mu.m, or
less. The above reduction of the design rules and the CDs
necessarily causes the various patterns for the semiconductor
devices to have high resolution.
[0006] Various resolution enhancement technologies (RETs) have been
applied to processes for manufacturing semiconductor devices so as
to form high-resolution patterns. For example, methods have been
suggested for increasing the numerical aperture (NA) of a lens so
as to irradiate illumination light onto a minute area of an object
in an exposure system, and improving the illumination light to have
a short wavelength through a dipole or a cross-pole illumination
process. Particularly, a krypton fluoride (KrF) excimer laser
having a wavelength of about 248 nm, an argon fluoride (ArF)
excimer laser having a wavelength of about 193 nm and a fluorine
(F2) excimer laser having a wavelength of about 157 nm are widely
used as the illumination light of the exposure system in accordance
with the technical trend of high-integration degrees of
semiconductor devices. Accordingly, the resolution of a pattern may
be sufficiently increased by using short-wavelength light as the
illumination light. However, the short wavelength light also causes
deterioration of depth of focus (DOF) in an exposure process. For
that reason, the RETs commonly adopt a phase-shift mask (PSM) so as
to avoid deterioration of the DOF. An initial PSM includes various
stepped portions that are formed or arranged in a transparent
substrate, and thus the phase of the light penetrating through the
PSM is shifted by the stepped portions. However, more recent PSMs
have been configured to include an additional layer that is formed
on a transparent substrate, and thus the phase of the illumination
light is shifted by the additional layer. Particularly, an
attenuated PSM has been widely used for forming a
large-aspect-ratio pattern such as a contact hole, or an isolation
pattern.
[0007] The attenuated PSM may shift the phase of the illumination
light and control the transmittance of the illumination light using
a single layer or a double layer in such a manner that the
intensity of a 0.sup.th order beam becomes similar to that of a
1.sup.st order beam of the illumination light. As a result, the
attenuated PSM allows an object to undergo a uniform exposure in an
exposure system. A 2.sup.nd order or higher beam of the
illumination light may hardly be irradiated onto the same position
as the 0.sup.th order beam due to the recent reduction in pattern
sizes. For that reason, the light intensity of an illumination site
on the object is generally estimated based on the 0.sup.th and
1.sup.st order beams of the illumination light. That is, when an
intensity difference (hereinafter referred to as intensity
deviation) between the 0.sup.th and the 1.sup.st order beams is
within an allowable range, the 0.sup.th and the 1.sup.st order
beams irradiated onto an exposure site of the object may be
substantially treated as a single beam having a uniform intensity,
and thus a circuit pattern on a mask may be accurately transcribed
onto the object.
[0008] However, the recent reduction of CDs and pattern sizes of
semiconductor devices may also cause a decrease of the transmission
area of the attenuated PSM, to thereby increase the intensity
deviation between the 0.sup.th and the 1.sup.st order beams. As a
result, the solubility of a first portion of the exposure site onto
which the 0.sup.th order beam is irradiated can be different from
that of a second portion of the exposure site onto which the
1.sup.st order beam is irradiated, and thus there is a problem in
that the circuit pattern on the mask may not be accurately
transcribed onto the object.
[0009] FIG. 1 is a graph showing intensities of the 0.sup.th and
the 1.sup.st order beams diffracted by a conventional attenuated
PSM. In FIG. 1, the vertical axis represents beam intensity, and
the horizontal axis represents a pattern size.
[0010] Referring to FIG. 1, as the pattern size becomes smaller,
the intensity deviation between the 0.sup.th and the 1.sup.st order
beams becomes greater. Particularly, as the pattern size decreases,
the intensity of the 0.sup.th order beam is decreased and the
intensity of the 1.sup.st order beam is not substantially changed.
As a result, as the pattern size decreases, the intensity deviation
is increased. Particularly, the intensity deviation when the
pattern size is about 40 nm is about two times the intensity
deviation when the pattern size is about 100 nm.
[0011] In an effort to decrease the intensity deviation between the
0.sup.th and the 1.sup.st order beams, there has been suggested
that a phase-edge PSM (PEPSM), which compensates for a phase shift
at an edge of a light-shielding pattern, or a chromeless mask
(CLM), be used in place of the attenuated PSM. However, there is a
problem in that use of the above PEPSM or CLM requires an
additional process, which can decrease process efficiency in a
manufacturing process of a semiconductor device.
SUMMARY OF THE INVENTION
[0012] Accordingly, embodiments of the present invention provide a
phase-shift mask (PSM) for decreasing an intensity deviation
between the 0.sup.th and the 1.sup.st order beams at an exposure
site of an object. An improved attenuated PSM is provided, in which
the intensity deviation is sufficiently decreased at the exposure
site of the object, despite size reduction in a light-shielding
pattern.
[0013] Embodiments of the present invention also provide a method
of manufacturing the above PSM.
[0014] According to an aspect of the present invention, there is
provided a PSM including a transmittance controller. The PSM
includes a transparent substrate through which light passes, a
light-shielding pattern that is positioned on the transparent
substrate and may prevent the light from being incident onto the
transparent substrate, a phase-shift pattern that is positioned on
the transparent substrate exposed through the transmitting portion
and a transmittance controller that is positioned at an upper
portion of the phase-shift pattern in the transmitting portion. The
light-shielding pattern defines a transmitting portion through
which the transparent substrate is partially exposed and the light
is incident onto the transparent substrate, and the phase-shift
pattern shifts the phase of the light that passes through the
transmitting portion. The transmittance controller controls the
transmittance of the light with respect to the phase-shift pattern
in the transmitting portion.
[0015] In some example embodiments, the transmitting portion has a
shape corresponding to a circuit pattern that is to be transcribed
onto a semiconductor substrate for manufacturing a semiconductor
device, and the phase-shift pattern comprises molybdenum (Mo) and
the light-shielding pattern comprises chromium (Cr). The
transmittance controller can include a material selected from the
group consisting of chromium (Cr), molybdenum (Mo) and tungsten
(W), and controls the transmittance of the light passing through
the phase-shift pattern, to thereby decrease an intensity deviation
between 0.sup.th and 1.sup.st order beams of the light. The light
includes an argon fluoride (ArF) excimer laser and the
transmittance controller includes a diffusion layer having a
diffusion depth of about 100 nm to about 500 nm from a top surface
of the phase-shift pattern. The phase-shift pattern has a thickness
of about 400 .ANG. to about 600 .ANG. A from a surface of the
transparent substrate.
[0016] According to another aspect of the present invention, there
is provided a method of forming a PSM. A phase-shift layer and a
light-shielding layer are sequentially formed on a transparent
substrate, to thereby form a blank mask on the transparent
substrate. A light-shielding pattern and a phase-shift pattern are
formed on the transparent substrate by consecutively and partially
removing the phase-shift layer and the light-shielding layer. The
light-shielding pattern includes a first opening and the
phase-shift pattern includes a second opening that is connected to
the first opening and partially exposes the transparent substrate.
A transmitting portion is formed in the light-shielding pattern by
partially removing the light-shielding pattern. The transmitting
portion includes at least one portion of the phase-shift pattern on
which a transmittance controller is formed.
[0017] In one example embodiment, the phase-shift layer comprises a
material selected from the group consisting of molybdenum (Mo),
molybdenum silicon (MoSi), molybdenum silicon nitride (MoSiN),
molybdenum silicon oxynitride (MoSiON), molybdenum silicon
carbonitride (MoSiCN), and molybdenum silicon carbon oxynitride
(MoSiCON), and the light-shielding layer comprises a material
selected from the group consisting of chromium (Cr), chromium
nitride (CrN), chromium carbide (CrC), and chromium carbonitride
(CrCN). In some example, embodiments, the transparent substrate can
comprise quartz, and the blank mask includes an object mask for an
attenuated PSM.
[0018] In some example, embodiments, forming the light-shielding
pattern and the phase-shift pattern includes: forming a first mask
pattern on a surface of the blank mask; partially etching the
light-shielding layer using the first mask pattern as an etching
mask, to thereby form the light-shielding pattern including the
first opening through which the phase-shift layer is partially
exposed; removing the first mask pattern from a surface of the
light-shielding pattern; and partially etching the phase-shift
layer using the light-shielding pattern as an etching mask, to
thereby form the phase-shift pattern including the second opening
that is connected to the first opening. The first mask pattern can
include a photoresist pattern that is formed on the blank mask by a
photolithography process. Etching of the light-shielding layer and
the phase-shift layer can be performed by a dry etching process
using a mixture of chlorine (Cl2) gas and oxygen (O2) gas as an
etching gas, or can be performed by a wet etching process using a
mixture of ceric ammonium nitrate (Ce(NH4)2(NO3)6) and perchloric
acid (HClO4) as an etchant.
[0019] In some example embodiments, forming the light-shielding
pattern and the phase-shift pattern can include: forming a first
mask pattern on a surface of the blank mask; partially etching the
light-shielding layer and the phase-shift layer sequentially using
the first mask as an etching mask, to thereby form the second
opening through which the transparent substrate is partially
exposed and the first opening that is connected to the second
opening; and removing the first mask pattern from a surface of the
light-shielding pattern.
[0020] In some example embodiments, the transmitting portion may be
formed through the following example steps. A mask layer is formed
on the light-shielding pattern to a sufficient thickness to fill up
the first and second openings, and the mask layer is partially
removed from the light-shielding pattern, to thereby form a second
mask pattern through which at least one light-shielding pattern is
exposed. The light-shielding pattern exposed through the second
mask pattern is etched off using the second mask pattern as an
etching mask, to thereby form a preliminary transmitting portion
through which the phase-shift pattern is exposed. Then, a thin
layer is formed on the phase-shift pattern exposed through the
preliminary transmitting portion, and a material of the thin layer
is diffused into the phase-shift pattern.
[0021] The light-shielding layer may be removed from the substrate
by a dry etching process using a mixture of chlorine (Cl2) gas and
oxygen (O2) gas as an etching gas, or by a wet etching process
using a mixture of ceric ammonium nitrate (Ce(NH4)2(NO3)6) and
perchloric acid (HClO4) as an etchant. Forming the thin layer on
the phase-shift pattern can include depositing a metal material
onto a surface of the phase-shift pattern exposed through the
preliminary transmitting portion using the second mask pattern on
the light-shielding pattern as a deposition mask. The metal
material can have an absorption coefficient of no less than about
1.5, and the metal material can include any one selected from the
group consisting of chromium (Cr), molybdenum (Mo), tungsten (W)
and combinations thereof. The metal material can be deposited onto
the phase-shift pattern by a physical vapor deposition (PVD)
process such as a sputtering process that is performed using bias
power of about 600 W to about 4,500 W using helium (He) gas or
argon (Ar) gas as a sputtering gas. The material of the thin layer
may be diffused into the phase-shift pattern by an annealing
process. For example, the annealing process may be performed in a
rapid thermal treatment apparatus using a tungsten-halogen lamp as
a heat source. Prior to the annealing process, the second mask
pattern can be removed from the transparent substrate, so that the
transparent substrate is exposed through the phase-shift
pattern.
[0022] According to example embodiments of the present invention, a
transmittance controller is formed on an upper portion of a
phase-shift pattern of an attenuated PSM, and controls an amount of
light transmitted to an object substrate, thereby minimizing an
intensity deviation between 0.sup.th and 1.sup.st order beams of
illumination light at the object substrate. Therefore, the pattern
may be uniformly formed on the object substrate by an exposure
process using the attenuated PSM including the transmittance
controller.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] The above and other features and advantages of the
embodiments of the present invention will become readily apparent
by reference to the following detailed description when considering
in conjunction with the accompanying drawings, in which:
[0024] FIG. 1 is a graph showing intensities of the 0.sup.th and
the 1.sup.st order beams diffracted by a conventional attenuated
phase-shift mask (PSM);
[0025] FIG. 2 is a cross-sectional view illustrating a phase-shift
mask in accordance with an example embodiment of the present
invention;
[0026] FIGS. 3A to 3G are cross-sectional views illustrating
processing steps for manufacturing the PSM shown in FIG. 2;
[0027] FIGS. 4A and 4B are graphs showing a relationship between
the thickness of a transmittance controller and the intensity of
transmitted light; and
[0028] FIGS. 5A and 5B are graphs showing process windows and
exposure latitudes of exposure processes in which the PSM including
the transmittance controller is used.
DETAILED DESCRIPTION OF EMBODIMENTS
[0029] Embodiments of the invention are described more fully
hereinafter with reference to the accompanying drawings, in which
example embodiments of the invention are shown. This invention may,
however, be embodied in many different forms and should not be
construed as limited to the embodiments set forth herein. Rather,
these embodiments are provided so that this disclosure will be
thorough and complete, and will fully convey the scope of the
invention to those skilled in the art. In the drawings, the size
and relative sizes of layers and regions may be exaggerated for
clarity.
[0030] It will be understood that when an element or layer is
referred to as being "on," "connected to" or "coupled to" another
element or layer, it can be directly on, connected or coupled to
the other element or layer or intervening elements or layers may be
present. In contrast, when an element is referred to as being
"directly on," "directly connected to" or "directly coupled to"
another element or layer, there are no intervening elements or
layers present. Like numbers refer to like elements throughout. As
used herein, the term "and/or" includes any and all combinations of
one or more of the associated listed items.
[0031] It will be understood that, although the terms first,
second, third etc. may be used herein to describe various elements,
components, regions, layers and/or sections, these elements,
components, regions, layers and/or sections should not be limited
by these terms. These terms are only used to distinguish one
element, component, region, layer or section from another region,
layer or section. Thus, a first element, component, region, layer
or section discussed below could be termed a second element,
component, region, layer or section without departing from the
teachings of the present invention.
[0032] Spatially relative terms, such as "beneath," "below,"
"lower," "above," "upper" and the like, may be used herein for ease
of description to describe one element or feature's relationship to
another element(s) or feature(s) as illustrated in the figures. It
will be understood that the spatially relative terms are intended
to encompass different orientations of the device in use or
operation in addition to the orientation depicted in the figures.
For example, if the device in the figures is turned over, elements
described as "below" or "beneath" other elements or features would
then be oriented "above" the other elements or features. Thus, the
exemplary term "below" can encompass both an orientation of above
and below. The device may be otherwise oriented (rotated 90 degrees
or at other orientations) and the spatially relative descriptors
used herein interpreted accordingly.
[0033] The terminology used herein is for the purpose of describing
particular embodiments only and is not intended to be limiting of
the invention. As used herein, the singular forms "a," "an" and
"the" are intended to include the plural forms as well, unless the
context clearly indicates otherwise. It will be further understood
that the terms "comprises" and/or "comprising," when used in this
specification, specify the presence of stated features, integers,
steps, operations, elements, and/or components, but do not preclude
the presence or addition of one or more other features, integers,
steps, operations, elements, components, and/or groups thereof.
[0034] Embodiments of the invention are described herein with
reference to cross-section illustrations that are schematic
illustrations of idealized embodiments (and intermediate
structures) of the invention. As such, variations from the shapes
of the illustrations as a result, for example, of manufacturing
techniques and/or tolerances, are to be expected. Thus, embodiments
of the invention should not be construed as limited to the
particular shapes of regions illustrated herein but are to include
deviations in shapes that result, for example, from manufacturing.
For example, an implanted region illustrated as a rectangle will,
typically, have rounded or curved features and/or a gradient of
implant concentration at its edges rather than a binary change from
implanted to non-implanted region. Likewise, a buried region formed
by implantation may result in some implantation in the region
between the buried region and the surface through which the
implantation takes place. Thus, the regions illustrated in the
figures are schematic in nature and their shapes are not intended
to illustrate the actual shape of a region of a device and are not
intended to limit the scope of the invention.
[0035] Unless otherwise defined, all terms (including technical and
scientific terms) used herein have the same meaning as commonly
understood by one of ordinary skill in the art to which this
invention belongs. It will be further understood that terms, such
as those defined in commonly used dictionaries, should be
interpreted as having a meaning that is consistent with their
meaning in the context of the relevant art and will not be
interpreted in an idealized or overly formal sense unless expressly
so defined herein.
[0036] FIG. 2 is a cross-sectional view illustrating a phase-shift
mask (PSM) in accordance with an example embodiment of the present
invention.
[0037] Referring to FIG. 2, a PSM 900 in accordance with an example
embodiment of the present invention includes a transparent
substrate 100 through which illumination light passes, a
light-shielding pattern 200 and a phase-shift pattern 300 on the
transparent substrate 100 and a transmittance controller 400, or
transmittance control pattern, on the phase-shift pattern 300.
[0038] For example, the transparent substrate 100 may include a
glass substrate comprising quartz, and thus most of the
illumination light incident thereto passes through the transparent
substrate 100. An optional, supplementary thin layer such as an
indium tin oxide layer may be further formed on the transparent
substrate 100.
[0039] The light-shielding pattern 200 for shielding the
illumination light and the phase-shift pattern 300 for shifting the
phase of the illumination light are positioned on the transparent
substrate 100. In the present embodiment, the phase-shift pattern
300 and the light-shielding pattern 200 are sequentially stacked on
a top surface of the transparent substrate 100.
[0040] The light-shielding pattern 200 is positioned on the
transparent substrate 100, and operates to prevent the illumination
light from passing through the substrate 100. In example
embodiments of the present invention, the light-shielding pattern
200 may comprise chromium (Cr), chromium nitride (CrN), chromium
carbide (CrC) or chromium carbonitride (CrCN). These may be used
alone or in combinations thereof. The light-shielding pattern 200
includes an opening 280 through which the transparent substrate 100
is partially exposed, so that the illumination light is partially
incident onto the transparent substrate 100 through the opening 280
of the light-shielding pattern 200. Hereinafter, the opening 280 of
the light-shielding pattern 200 is referred to as a transmitting
portion 280 of the light-shielding pattern 200. As a result, the
transmitting portion 280 has the same shape as a circuit pattern
that is to be transcribed onto a semiconductor substrate for a
semiconductor device. Accordingly, the top surface of the
transparent substrate 100 is partially exposed in correspondence
with the transmitting portion 280, and other portions of the top
surface of the transparent substrate 100 are covered by the
light-shielding pattern 200. As a result, the illumination light is
incident onto the transparent substrate 100 in accordance with the
circuit pattern.
[0041] The phase-shift pattern 300 may be interposed between the
light-shielding pattern 200 and the transparent substrate 100, so
that the phase of the illumination light is shifted before being
incident onto the transparent substrate 100, to thereby control the
intensity of a coherent light due to interference between
diffracted beams of the illumination light. Particularly, the
light-shielding pattern 200 is partially removed from the substrate
100, and no light-shielding pattern 200 is positioned in the
transmitting portion 280 and the transparent substrate 100 is
partially exposed through the transmitting portion 280. Therefore,
only portions of the phase-shift pattern 300 are positioned in the
transmitting portion 280, without the light-shielding pattern
200.
[0042] In example embodiments, the phase-shift pattern 300 may
comprise molybdenum (Mo), molybdenum silicon (MoSi), molybdenum
silicon nitride (MoSiN), molybdenum silicon oxynitride (MoSiON),
molybdenum silicon carbonitride (MoSiCN), or molybdenum silicon
carbon oxynitride (MoSiCON). These may be used alone or in
combinations thereof.
[0043] The illumination light incident onto the phase-shift pattern
300 is transmitted through the phase-shift pattern 300 at a given
transmittance, and the phase of the transmitted light is shifted at
an angle with respect to that of the incident light onto the
phase-shift pattern 300. When the PSM 900 is used as a mask pattern
in an exposure process, the illumination light penetrates through
the transmitting portion 280 of the light-shielding pattern 200 and
the illumination light is diffracted by the phase-shift pattern
300. Each of the diffracted beams of the illumination light
interferes with one another constructively or destructively on a
semiconductor substrate. That is, the illumination light is
transformed into a coherent light on the semiconductor substrate.
In the present embodiment, 0.sup.th and 1.sup.st order beams are
mainly used as a light source for exposing the semiconductor
substrate. The 0.sup.th order beam indicates the diffracted beam of
the illumination light that does not interfere with any other
diffracted beams of the illumination light, and the 1.sup.st order
beam indicates a coherent beam in which the diffracted beams of the
illumination light constructively interfere with each other at a
position firstly close to the 0.sup.th order beam of the
illumination light. The phase-shift pattern 300 shifts the phase of
the illumination light passing through the phase-shift pattern 300
in such a manner that the 0.sup.th and 1.sup.st order beams are
exposed to a photoresist film on the semiconductor substrate at a
uniform intensity.
[0044] In an example embodiment, the transmittance controller 400
is located on the phase-shift pattern 300, so that the
transmittance of the illumination light that is incident onto the
phase-shift pattern 300 is controlled. Particularly, the amount of
the light passing through the phase-shift mask 300 may be
controller by the transmittance controller 400, so that the
intensity deviation between the 0.sup.th and 1.sup.st order beams
may be minimized on the photoresist film on the semiconductor
substrate.
[0045] For example, the transmittance controller 400 may include a
diffusion layer that is diffused to a depth of about 100 nm to
about 500 nm from a top surface of the phase-shift pattern 300. The
transmittance controller 400 may comprise a metal having a large
absorption coefficient. In the present embodiment, the
transmittance controller 400 may comprise a metal having an
absorption coefficient of no less than about 1.5. Examples of the
metal may include chromium (Cr), molybdenum (Mo) and tungsten (W).
In the present embodiment, the phase-shift pattern 300 may have a
thickness of about 4,000 nm to about 6,000 nm, so that the
transmittance controller 400 occupies about 1.25% to about 8.3% of
the thickness of the phase-shift pattern 300 at an upper portion
thereof.
[0046] According to the PSM 900 of embodiments of the present
invention, the transmittance controller 400 is positioned on the
phase-shift pattern 300, to thereby control the transmittance of
the light passing through the phase-shift pattern 300. The
intensity of the 0.sup.th and 1.sup.st order beams, which form the
coherent light irradiated onto the photoresist film on the
semiconductor substrate, may be determined in accordance with the
amount of light passing through the phase-shift pattern 300, so
that the transmittance controller 400 may minimize the intensity
deviation between the 0.sup.th and 1.sup.st order beams. As a
result, when the PSM 900 is used as a mask pattern for an exposure
process, the intensity deviation between the 0.sup.th and 1.sup.st
order beams may be sufficiently reduced to thereby improve the
uniformity of the exposure process to the photoresist film on the
semiconductor substrate.
[0047] FIGS. 3A to 3G are cross-sectional views illustrating
processing steps for manufacturing the PSM shown in FIG. 2.
[0048] Referring to FIGS. 2 and 3A, a phase-shift layer 300a and a
light-shielding layer 200a are sequentially stacked on the
transparent substrate 100 through which most of the light passes,
to thereby form a blank mask layer on the transparent substrate
100.
[0049] For example, the phase-shift layer 300a may comprise
molybdenum (Mo), molybdenum silicon (MoSi), molybdenum silicon
nitride (MoSiN), molybdenum silicon oxynitride (MoSiON), molybdenum
silicon carbonitride (MoSiCN), or molybdenum silicon carbon
oxynitride (MoSiCON). These may be used alone or in combinations
thereof. In addition, the light-shielding layer 200a may comprise
chromium (Cr), chromium nitride (CrN), chromium carbide (CrC) or
chromium carbonitride (CrCN). These may also be used alone or in
combinations thereof. In the present example embodiment, the
phase-shift layer 300a may comprise molybdenum silicon (MoSi), and
the light-shielding layer 200a may comprise chromium (Cr). Further,
the transparent substrate 100 may include a glass substrate
comprising quartz, and the blank mask may be formed into an
attenuated PSM in subsequent processes.
[0050] Referring to FIGS. 2 and 3B, the phase-shift layer 300a and
the light-shielding layer 200a are partially removed from the
transparent substrate 100, thereby forming the light-shielding
pattern 200 including a first opening 220 and the phase-shift
pattern 300 including a second opening 320 that is connected to the
first opening 220. The transparent substrate 100 may be partially
exposed through the first and second openings 220 and 320.
[0051] In example embodiments, a first mask pattern 500 is formed
on the light-shielding layer 200a of the blank mask. The first mask
pattern 500 may include a photoresist pattern that may be formed
from a photoresist film by a photolithography process. Then, the
light-shielding layer 200a is partially etched off using the first
mask pattern 500 as an etching mask, thereby forming the first
opening 220 through which the phase-shift layer 300a is partially
exposed. Accordingly, the light-shielding layer 200a is formed into
the light-shielding pattern 200 including the first opening 220.
Thereafter, the first mask pattern 500 is removed from the
light-shielding pattern 200. Then, the phase-shift layer 300a is
partially etched off using the light-shielding pattern as an
etching mask, thereby forming the second opening 320 consecutively
to the first opening 220. Therefore, the phase-shift layer 300a is
formed into the phase mask pattern 300 including the second opening
320.
[0052] In an example embodiment, the light-shielding layer 200a and
the phase-shift layer 300a may be etched off by a dry etching
process using a mixture of chlorine (Cl2) gas and oxygen (O2) gas
as an etching gas or by a wet etching process using a mixture of
ceric ammonium nitrate (Ce(NH4)2(NO3)6) and perchloric acid (HClO4)
as an etchant. The composition of the etching gas or the etchant
may be varied in accordance with the composition of the
light-shielding layer 200a or the phase-shift layer 300a, as would
be known to one of the ordinary skill in the art.
[0053] In another example embodiment, the light-shielding layer
200a and the phase-shift layer 300a may be sequentially and
continuously etched off by a single etching process using the first
mask pattern 500 as an etching mask. The first mask pattern 500 is
formed on the light-shielding layer 200a, and the light-shielding
layer 200a and the phase-shift layer 300a are partially etched off
sequentially and continuously using the first mask pattern 500 as
an etching mask, thereby forming the second opening 320 through
which the transparent substrate 100 is partially exposed and the
first opening 220 that is connected to the second opening 320.
[0054] Thereafter, the first mask pattern 500 is removed from the
light-shielding pattern 200 by a strip process.
[0055] Referring to FIGS. 2 and 3C, a second mask pattern 600 is
formed on the light-shielding pattern 200, and a transmitting
portion is to be formed in the light-shielding pattern 200 in the
following processes.
[0056] A mask layer (not shown) is formed on the light-shielding
pattern 200 to a sufficient thickness to fill up the first and
second openings 220 and 320, and then a planarization process is
performed on the mask layer in such a manner that the mask layer
has a given thickness from a top surface of the light-shielding
pattern 200. The mask layer is partially removed from the
light-shielding pattern 200 by a photolithography process, thereby
forming the second mask pattern 600 through which the
light-shielding pattern 200 is partially exposed. In the present
embodiment, the processing conditions of the photolithography
process are adjusted to sufficiently expose a top surface of the
light-shielding pattern 200, and a top surface of the mask pattern
600 filling up the first and second openings 220 and 320 is
positioned lower than or equal to the top surface of the
light-shielding pattern 200. The removed portion of the mask
pattern 600 is formed into a preliminary transmitting portion 240
in FIG. 3D that is formed into the transmitting portion 280 in FIG.
3F through which the illumination light is transmitted onto the
transparent substrate 100 in a subsequent process.
[0057] Referring to FIGS. 2 and 3D, the light-shielding pattern 200
is etched off from the phase-shift pattern 300 using the second
mask pattern 600 as an etching mask, thereby forming the
preliminary transmitting portion 240 through which the phase-shift
pattern 300 is exposed. In some example embodiments, the
light-shielding pattern 200 exposed through the second mask pattern
600 may be etched off by a dry etching process using a mixture of
chlorine (Cl2) gas and oxygen (O2) gas as an etching gas or by a
wet etching process using a mixture of ceric ammonium nitrate
(Ce(NH4)2(NO3)6) and perchloric acid (HClO4) as an etchant in a
process similar to that for forming the first and second openings
220 and 320. The phase-shift pattern 300 can function as an etching
stop layer in the above etching process, so that only the
light-shielding pattern 200 is removed from the transparent
substrate 100. The second mask pattern 600 in the first opening 220
may also be removed from the transparent substrate 100
simultaneously with the light-shielding pattern 200. When an etch
rate of the light-shielding pattern 200 is the same as that of the
second mask pattern 600, a top surface of the second mask pattern
600 remaining in the second opening 320 is coplanar with a top
surface of the phase-shift pattern 300. Embodiments of the present
invention do not necessarily require that the top surface of the
second mask pattern 600 in the second opening 320 be coplanar with
the top surface of the phase-shift pattern 300, as would be known
to one of the ordinary skill in the art. In the present embodiment,
the second mask pattern 600 in the second opening 320 may be formed
to have a sufficient thickness for protecting the transparent
substrate 100 in a subsequent deposition process for forming the
transmittance controller.
[0058] Referring to FIGS. 2 and 3E, a thin layer 700a is formed on
the phase-shift pattern 300 and the second mask pattern 600 in the
second opening 320.
[0059] In an example embodiment, a metal is deposited onto the
phase-shift pattern 300 and the second mask pattern 600 in the
preliminary transmitting portion 240 by a physical vapor deposition
(PVD) process, thereby forming the metal thin layer 700a on the
phase-shift pattern 300 and the second mask pattern 600. In the
present embodiment, the transparent substrate 100 including the
preliminary transmitting portion 240 is loaded into a chamber for a
sputtering process in which a metal target is positioned. Inert
gases such as argon (Ar) gases and helium (He) gases are supplied
into the processing chamber and bias power of about 600 W to about
4,500 W is applied to the processing chamber. Then, the inert gases
are transformed into plasma and the metal of the target is ionized
in the processing chamber. The metal ions are deposited onto top
surfaces of the phase-shift pattern 300 and the second mask pattern
600 in the preliminary transmitting portion 240.
[0060] For example, the metal may have an absorption coefficient of
no less than about 1.5. Examples of the metal include chromium
(Cr), molybdenum (Mo) and tungsten (W). These may be used alone or
in combinations thereof. The magnitude of the absorption
coefficient and the metal having the absorption coefficient may be
varied in accordance with the wavelength of the illumination light,
exposure conditions, and the desired design rule, size and/or shape
of the pattern, so that the embodiments of the present invention
should not be limited to these example metal materials but various
other materials can be used as the metal, as would be apparent to
one skilled in the art.
[0061] Referring to FIGS. 2 and 3F, the second mask pattern 600 is
removed from the transparent substrate 100. In a case where the
second mask pattern 600 includes a photoresist pattern, a strip
process may be used for removing the second mask pattern 600.
Particularly, when the second mask pattern 600 in the second
opening 320 is removed from the transparent substrate 100, the thin
layer 700a on the second mask pattern 600 is also removed from the
transparent substrate 100 simultaneously with the second mask
pattern 600. Therefore, the transparent substrate 100 is partially
exposed through the second opening 320 and the thin layer 700a
remains only on the phase-shift pattern 300, thereby forming a thin
layer pattern 700 on the phase-shift pattern 300. As a result, the
transmitting portion 280 defined by the light-shielding pattern 200
is formed on the transparent substrate 100. The transmitting
portion 280 includes a first portion 280a defined by the
light-shielding pattern 200 and a second portion 280b including the
phase-shift pattern 300 for controlling the amount of the light
transmitted thereto.
[0062] Referring to FIGS. 2 and 3G, a heat treatment is performed
on the substrate 100 including the thin layer pattern 700, so that
the metal in the thin layer pattern 700 is diffused into the
phase-shift pattern 300. As a result, the transmittance controller
400 for controlling the amount of the light transmitted to the
phase-shift pattern 300 is formed on the phase-shift pattern 300.
The amount of the transmitted light may be determined by the
material comprising the transmittance controller 400 and by the
thickness of the transmittance controller 400.
[0063] The heat treatment may include a rapid thermal process using
a tungsten-halogen lamp as a heat source. For example, the heat
treatment may include an annealing process. The annealing process
may be performed at a temperature of about 800.degree. C. to about
1,500.degree. C. for about 3 seconds to about 10 seconds.
Accordingly, the metal material of the metal thin layer 700 may be
diffused into the phase-shift pattern 300 at a depth about 100 nm
to about 500 nm.
[0064] FIGS. 4A and 4B are graphs showing a relationship between
the thickness of the transmittance controller and the intensity of
the transmitted light. That is, FIGS. 4A and 4B indicate the
thickness of the transmittance controller that minimizes the
intensity deviation between diffracted beams. FIG. 4A shows
experimental results in a case where the pattern size is about 45
nm, and FIG. 4B shows experimental results in a case where the
pattern size is about 63 nm. Further, in FIGS. 4A and 4B, numeral I
indicates intensity variation of the 0.sup.th order beam, and
numeral II indicates intensity variation of the 1.sup.st order
beam. Various experiments were performed for the results of FIGS.
4A and 4B under conditions in which an argon fluoride (ArF) excimer
laser is used as a light source and the phase-shift pattern on
which the transmittance controller comprising chromium (Cr) is
positioned has a thickness of about 677 .ANG..
[0065] Referring to FIG. 4A, when an exposure process was performed
to form a pattern having a half-pitch of about 45 nm using the PSM,
the intensity deviation between the 0.sup.th and the 1.sup.st order
beams continuously improved until the thickness of the
transmittance controller increased to about 380 nm. However, when
the thickness of the transmittance controller was more than about
380 nm, the intensity deviation between the 0.sup.th and the
1.sup.st order beams no longer improved. Referring to FIG. 4B, when
an exposure process was performed to form a pattern having a
half-pitch of about 63 nm using the PSM, the intensity deviation
between the 0.sup.th and the 1.sup.st order beams was minimized
when the thickness of the transmittance controller was about 90 nm.
In contrast, the intensity deviation between the 0.sup.th and the
1.sup.st order beams increased when the thickness of the
transmittance controller was more than about 90 nm.
[0066] Accordingly, the intensity deviation between the 0.sup.th
and the 1.sup.st order beams may be improved by the transmittance
controller, and the optimal thickness of the transmittance
controller for minimizing the intensity deviation may be varied in
accordance with processing conditions for an exposure process.
[0067] The improvement of the intensity deviation between the
0.sup.th and the 1.sup.st order beams may extend an allowable error
range of a depth of focus (DOF) and a proper dose of the light for
the exposure process, so that the process window and the exposure
latitude of the exposure process may be enlarged, thereby
increasing the processing margin of the exposure process.
[0068] FIGS. 5A and 5B are graphs showing process windows and
exposure latitudes of exposure processes in which the PSM including
the transmittance controller is used. FIG. 5A shows experimental
results of the exposure process for forming a pattern having a
half-pitch of about 45 nm, and FIG. 5B shows experimental results
of the exposure process for forming a pattern having a half-pitch
of about 63 nm. In FIGS. 5A and 5B, Graph I shows experimental
results of the exposure process using a conventional attenuated PSM
without the transmittance controller, and Graph II shows
experimental results of the exposure process using an attenuated
PSM including the transmittance controller that comprises chromium
(Cr). Graph III shows experimental results of the exposure process
using an attenuated PSM including the transmittance controller that
comprises molybdenum (Mo), and Graph IV shows experimental results
of the exposure process using an attenuated PSM including the
transmittance controller that comprises tungsten (W). In FIGS. 5A
and 5B, the horizontal axis denotes a DOF of the exposure process,
and the vertical axis denotes a dose of the light. The process
window of the exposure process is denoted as reference letter
A.sub.i in each of the graphs. The process window indicates an
allowable range of the dose at an optimal DOF in each of the
exposure processes. As a result, as the process window becomes
larger, the processing margin of the exposure process becomes
greater. Since the processing margin of the exposure process is
enlarged, the possibility of processing defects may be decreased,
to thereby improve the reliability of the exposure process.
[0069] Referring to FIG. 5A, when an exposure process was performed
for forming the pattern having a half-pitch of about 45 nm, the
transmittance controller on the attenuated PSM increased the size
of the process window. That is, the sizes of the process windows
A2, A3, and A4 that were caused by an exposure process using the
attenuated PSM including the transmittance controller were much
greater than the size of the process window A1 that was caused by
an exposure process using the attenuated PSM without the
transmittance controller. Further, the transmittance controller
also improved the exposure latitude, for example, from about 10.07%
to about 11.70%, 12.15% and 11.86%, respectively.
[0070] Referring to FIG. 5B, when an exposure process is performed
for forming the pattern having a half-pitch of about 63 nm, the
transmittance controller on the attenuated PSM also increased the
size of the process window. That is, the sizes of the process
windows A6, A7, and A8 that were caused by an exposure process
using the attenuated PSM including the transmittance controller
were much greater than the size of the process window A5 that was
caused by an exposure process using the attenuated PSM without the
transmittance controller. Further, the transmittance controller
also improved the exposure latitude, for example, from about 10.34%
to about 11.15%, 11.71% and 11.26%, respectively.
[0071] Accordingly, the presence of the transmittance controller on
the phase-shift pattern can operate to improve the process window
and exposure latitude of the exposure process as well as decrease
the intensity deviation between the 0.sup.th and the 1.sup.st order
beams.
[0072] According the example embodiments of the present invention,
a transmittance controller comprising a metal is formed on an upper
portion of a phase-shift pattern of an attenuated PSM, thereby
minimizing an intensity deviation between 0.sup.th and 1.sup.st
order beams of illumination light at a photoresist film on a
semiconductor substrate. In addition, the transmittance controller
of the attenuated PSM may also improve the size of a process window
and the size of an exposure latitude in an exposure process,
thereby increasing the processing margin of the exposure process.
As a result, the process reliability of an exposure process may be
sufficiently increased despite a small pattern size, so that a
minute pattern may be formed on a semiconductor substrate with
sufficient accuracy.
[0073] Although the example embodiments of the present invention
have been described, it is understood that the present invention
should not be limited to these example embodiments but various
changes and modifications can be made by one skilled in the art
within the spirit and scope of the present invention as hereinafter
claimed.
* * * * *