U.S. patent application number 12/509048 was filed with the patent office on 2009-11-19 for method of forming a phase changeable structure.
This patent application is currently assigned to SAMSUNG ELECTRONICS CO., LTD.. Invention is credited to Jun-Soo Bae, Young-Soo Lim.
Application Number | 20090283741 12/509048 |
Document ID | / |
Family ID | 38534032 |
Filed Date | 2009-11-19 |
United States Patent
Application |
20090283741 |
Kind Code |
A1 |
Lim; Young-Soo ; et
al. |
November 19, 2009 |
METHOD OF FORMING A PHASE CHANGEABLE STRUCTURE
Abstract
The present invention relates to a method of forming a phase
changeable structure wherein an upper electrode is formed on a
phase changeable layer. A material including fluorine can be
provided to the phase changeable layer and the upper electrode. The
phase changeable layer can be etched to form a phase changeable
pattern. Oxygen plasma or water vapor plasma can then be provided
to the upper electrode and the phase changeable pattern.
Inventors: |
Lim; Young-Soo;
(Chungcheongbuk-do, KR) ; Bae; Jun-Soo;
(Gyeonggi-do, KR) |
Correspondence
Address: |
MARGER JOHNSON & MCCOLLOM, P.C.
210 SW MORRISON STREET, SUITE 400
PORTLAND
OR
97204
US
|
Assignee: |
SAMSUNG ELECTRONICS CO.,
LTD.
Gyeonggi-do
KR
|
Family ID: |
38534032 |
Appl. No.: |
12/509048 |
Filed: |
July 24, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11625142 |
Jan 19, 2007 |
7582568 |
|
|
12509048 |
|
|
|
|
Current U.S.
Class: |
257/4 ;
257/E47.001; 257/E47.005; 438/478 |
Current CPC
Class: |
H01L 45/144 20130101;
H01L 45/1675 20130101; H01L 45/06 20130101; H01L 45/1233
20130101 |
Class at
Publication: |
257/4 ; 438/478;
257/E47.001; 257/E47.005 |
International
Class: |
H01L 47/00 20060101
H01L047/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 20, 2006 |
KR |
10-2006-0006057 |
Jan 17, 2007 |
KR |
10-2007-0005007 |
Claims
1. A method of forming at least part of a phase changeable
structure, the method comprising: forming a phase changeable layer
on a lower electrode; forming a conductive layer on the phase
changeable layer; etching the conductive layer and at least a
portion of the phase changeable layer with a first material having
a chlorine-containing compound and a fluorine-containing compound
to form an upper electrode and at least a portion of a phase
changeable pattern; and exposing the upper electrode and the phase
changeable pattern to a second material having an oxygen-containing
compound.
2. The method of claim 1, further comprising a step of evacuating
substantially all of the first material before the exposing
step.
3. The method of claim 1, wherein the oxygen-containing compound is
selected from the group consisting of oxygen plasma, water vapor
plasma, and mixtures thereof.
4. The method of claim 1, wherein the exposing step is conducted at
a temperature of less than about 150.degree. C.
5. The method of claim 1, wherein the exposing step is conducted in
situ.
6. The method of claim 1, wherein the phase changeable layer
comprises a calcogenide selected from the group consisting of
germanium, antimony, tellurium, and any combination thereof.
7. The method of claim 1, wherein the conductive layer comprises a
metal selected from the group consisting of tungsten, titanium,
titanium nitride, tantalum, tantalum nitride, molybdenum nitride,
niobium nitride, titanium silicon nitride, aluminum, titanium
aluminum nitride, titanium boron nitride, zirconium silicon
nitride, tungsten silicon nitride, tungsten boron nitride,
zirconium aluminum nitride, molybdenum silicon nitride, molybdenum
aluminum nitride, tantalum silicon nitride, tantalum aluminum
nitride, copper, aluminum copper, alloys thereof, and any
combination thereof.
8. The method of claim 1, wherein the fluorine-containing compound
is selected from the group consisting of tetrafluoromethane,
trifluoromethane, difluoromethane, monofluoromethane, and any
combination thereof.
9. The method of claim 1, wherein the first material further
includes a diluent compound in a plasma state.
10. The method of claim 9, wherein the diluent compound is selected
from the group consisting of helium, neon, argon, krypton, xenon,
radon or any combination thereof.
11. A phase changeable structure obtained from the method of claim
1, wherein the structure shows decreased damage of the phase
changeable pattern.
Description
CROSS-REFERENCE TO RELATED PATENT APPLICATION
[0001] This application is a Divisional of U.S. Ser. No.
11/625,142, filed on Jan. 19, 2007, now is pending, which claims
priority from Korean Patent Application Nos. 10-2006-0006057 filed
on Jan. 20, 2006, and 10-2007-0005007 filed on Jan. 17, 2007 in the
Korean Intellectual Property Office, all of the disclosure of which
are incorporated herein by reference in their entirety.
FIELD OF THE INVENTION
[0002] The present invention relates to a method of forming a
structure in a memory cell. More particularly, the present
invention relates to a method of forming a phase changeable
structure in a memory cell.
BACKGROUND OF THE INVENTION
[0003] Nonvolatile memory devices have garnered much interest in
recent times, including nonvolatile memory devices made of a phase
changeable structure. Referencing FIG. 1, a phase changeable
structure typically includes a lower electrode 200, a phase
changeable pattern 310 and an upper electrode 410. A phase
changeable pattern can be obtained from etching a phase changeable
layer using a mask pattern. The phase changeable pattern is
typically situated between the lower electrode and the upper
electrode and can include a calcogenide.
[0004] Typically, a predetermined amount of current (e.g.,
generated by a difference in voltage between the lower electrode
and the upper electrode) can be applied to the phase changeable
pattern to induce a change in phase from a single crystalline state
having a relatively low electric resistance into an amorphous state
having a relatively high electric resistance. In addition, when the
current applied to the phase changeable pattern is reduced or
removed, the phase changeable pattern may be changed from the
amorphous state into the single crystalline state.
[0005] In accordance with a conventional method of forming a phase
changeable structure, a phase changeable layer is formed on a lower
electrode. A metal nitride layer is then formed on the phase
changeable layer. Thereafter, a first etching process is performed
on the metal nitride layer to form an upper electrode 410 on the
phase changeable layer, as illustrated in FIG. 1. A second etching
process is then performed on the phase changeable layer to form a
phase changeable pattern 310, as illustrated in FIG. 1.
[0006] When either or both of the first etching process or the
second etching process is performed using a chlorine-containing
etching material, a commonly used etchant, a significant amount of
defects were detected in the phase changeable pattern. It is
believed that chlorine may reside on a side face of the phase
changeable pattern or at an interface between the phase changeable
pattern and the upper electrode. It is also believed that this
remaining chlorine residue or a byproduct thereof may contribute to
defect formation, such as via erosion, in succeeding processes. An
illustration of the typical defects that can be formed is
illustrated in FIG. 1. Defects can occur between the phase
changeable pattern 310 and the top electrode 410 as illustrated by
reference number 302 in either or both portions of the phase
changeable structure. Defects can also occur on a side face of the
phase changeable pattern 310, as illustrated by reference numbers
304 and 306. Defects can also occur between phase changeable
pattern 310 and the insulating layer, as illustrated by reference
number 306. When such defects occur, erratic and discontinuous
resistance to current behavior can be exhibited, as illustrated in
FIG. 2.
SUMMARY OF THE INVENTION
[0007] The present invention provides a method of forming a phase
changeable structure including a phase changeable pattern having a
reduction in defects.
[0008] In accordance with a first embodiment of the present
invention, a phase changeable layer is formed on a lower electrode.
A conductive layer is then formed on the phase changeable layer.
The conductive layer and at least a portion of the phase changeable
layer are then etched by using a first material including a
chlorine-containing compound and a fluorine-containing compound to
form an upper electrode and at least a portion of a phase
changeable pattern, respectively. The upper electrode and the phase
changeable pattern are then exposed to a second material having an
oxygen-containing compound.
[0009] In accordance with a second embodiment of the present
invention, a phase changeable layer is formed on a lower electrode.
A conductive layer including metal is then formed on the phase
changeable layer. At least a portion of the conductive layer is
etched by using a first material having a chlorine-containing
compound to form an upper electrode. The upper electrode and the
phase changeable layer are then exposed to a second material having
a fluorine-containing compound. The phase changeable layer is then
etched by using a third material that is substantially free of
chlorine to form a phase changeable pattern.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The above and other advantages of the present invention will
become readily apparent by reference to the following detailed
description when considered in conjunction with the accompanying
drawings in which:
[0011] FIG. 1 is a cross-sectional view illustrating a phase
changeable structure having typical defects;
[0012] FIG. 2 is a graph showing electric resistance in relation to
current of a phase changeable structure containing the typical
defects illustrated in FIG. 1;
[0013] FIGS. 3 and 4 are cross-sectional views illustrating a
method of forming a phase changeable structure in accordance with a
first embodiment of the present invention;
[0014] FIG. 5 is a graph showing electric resistance in relation to
current of a phase changeable pattern formed by using the methods
of one embodiment of the present invention ; and
[0015] FIGS. 6 to 8 are cross-sectional views illustrating a method
of forming a phase changeable structure in accordance with a second
embodiment of the present invention.
DESCRIPTION OF THE EMBODIMENTS
[0016] Embodiments of the present invention will be described with
reference to the accompanying drawings. The present invention may,
however, be embodied in many different forms and should not be
construed as limited to the embodiments set forth herein. Rather,
the embodiments are provided so that disclosure of the present
invention will be thorough and complete, and will fully convey the
scope of the present invention to those skilled in the art. The
principles and features of this invention may be employed in varied
and numerous embodiments without departing from the scope of the
present invention. In the drawings, the relative sizes of layers
and regions may be exaggerated for clarity. The drawings are not to
scale. Unless otherwise indicated, like reference numerals
designate like elements throughout the drawings.
[0017] It will also be understood that when an element or layer is
referred to as being "on," "connected to" and/or "coupled to"
another element or layer, the element or layer may be directly on,
connected and/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" and/or "directly coupled to" another element or layer, no
intervening elements or layers are present. As used herein, the
term "and/or" may include any and all combinations of one or more
of the associated listed items.
[0018] It will also be understood that, although the terms first,
second, 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 may be used to distinguish one element,
component, region, layer and/or section from another element,
component, region, layer and/or section. For example, a first
element, component, region, layer and/or section discussed below
could be termed a second element, component, region, layer and/or
section without departing from the teachings of the present
invention.
[0019] Spatially relative terms, such as "beneath," "below,"
"lower," "above," "upper" and the like may be used to describe an
element and/or feature's relationship to another element(s) and/or
feature(s) as, for example, illustrated in the figures. It will be
understood that the spatially relative terms are intended to
encompass different orientations of the device in use and/or
operation in addition to the orientation depicted in the figures.
For example, when the device in the figures is turned over,
elements described as "below" and/or "beneath" other elements or
features would then be oriented "above" the other elements or
features. The device may be otherwise oriented (rotated 90 degrees
or at other orientations) and the spatially relative descriptors
used herein interpreted accordingly.
[0020] The terminology used herein is for the purpose of describing
particular embodiments only and is not intended to limit of the
invention. As used herein, the singular terms "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 "includes" and/or "including", when used in this
specification, specify the presence of stated features, integers,
steps, operations, elements, and/or components, but do not preclude
the presence and/or addition of one or more other features,
integers, steps, operations, elements, components, and/or groups
thereof.
[0021] Unless otherwise defined, all terms (including technical and
scientific terms) used herein may have the same meaning as what is
commonly understood by one of ordinary skill in the art. 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 this
specification and the relevant art and will not be interpreted in
an idealized and/or overly formal sense unless expressly so defined
herein.
[0022] Embodiments of the present invention are described with
reference to cross-section illustrations that are schematic
illustrations of idealized embodiments of the present 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 present 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, a region
illustrated as a rectangle will, typically, have rounded or curved
features. Thus, the regions illustrated in the figures are
schematic in nature of a device and are not intended to limit the
scope of the present invention.
Embodiment 1
[0023] FIGS. 3 and 4 are cross-sectional views illustrating a
method of forming a phase changeable structure in accordance with a
first embodiment of the present invention.
[0024] Referring to FIG. 3, an insulating layer 100 having a hole
10 is formed. The insulating layer 100 may be formed using oxide or
nitride. For example, the insulating layer 100 may be formed using
phosphor silicate glass (PSG), boro-phosphor silicate glass (BPSG),
undoped silicate glass (USG), spin on glass (SOG), tetra ethyl
ortho silicate (TEOS), plasma enhanced-TEOS (PE-TEOS), flowable
oxide (FOX), high density plasma-chemical vapor deposition
(HDP-CVD) oxide or silicon nitride.
[0025] A lower electrode 200 is formed in the hole 10. The lower
electrode 200 may be formed using metal, metal nitride or
combination thereof. For example, the lower electrode 200 may be
formed using tungsten, titanium, titanium nitride, tantalum,
tantalum nitride, molybdenum nitride, niobium nitride, titanium
silicon nitride, aluminum, titanium aluminum nitride, titanium
boron nitride, zirconium silicon nitride, tungsten silicon nitride,
tungsten boron nitride, zirconium aluminum nitride, molybdenum
silicon nitride, molybdenum aluminum nitride, tantalum silicon
nitride, tantalum aluminum nitride, copper, aluminum copper, alloys
thereof, or any combination thereof. Alternatively, the lower
electrode may include polysilicon doped with impurities. An upper
face of the insulating layer 100 may be substantially coplanar with
an upper face of the lower electrode 200.
[0026] A phase changeable layer 300 is then formed on the
insulating layer 100 and the lower electrode 200. The phase
changeable layer 300 may include calcogenide. The calcogenide may
include germanium (Ge), antimony (Sb) and tellurium (Te). The
calcogenide can also include dopants such as silicon (Si), aluminum
(Al), titanium (Ti), carbon (C), or any combination thereof.
[0027] A conductive layer 400 including metal is then formed on the
phase changeable layer 300. The conductive layer 400 may be formed
using metal, metal nitride or combination thereof. For example, the
conductive layer 400 may be formed using tungsten, titanium,
titanium nitride, tantalum, tantalum nitride, molybdenum nitride,
niobium nitride, titanium silicon nitride, aluminum, titanium
aluminum nitride, titanium boron nitride, zirconium silicon
nitride, tungsten silicon nitride, tungsten boron nitride,
zirconium aluminum nitride, molybdenum silicon nitride, molybdenum
aluminum nitride, tantalum silicon nitride, tantalum aluminum
nitride, copper, aluminum copper, alloys thereof, or any
combination thereof.
[0028] The conductive layer 400 may be formed by a sputtering
process, a chemical vapor deposition (CVD) process, an electron
bean deposition process, an atomic layer deposition (ALD) process
or a pulse laser deposition (PLD) process.
[0029] A mask pattern 500 is then formed on the conductive layer
400. The mask pattern 500 may include material having an etching
selectively with respect to the conductive layer 400 and the phase
changeable layer 300.
[0030] Referring to FIGS. 3 and 4, the conductive layer 400 and the
phase changeable layer 300 can be successively etched using the
mask pattern 500 as an etch mask. Particularly, the conductive
layer 400 and the phase changeable layer 300 are etched using a
first material including a chlorine-containing compound and a
fluorine-containing compound. Thus, the conductive layer 400 and
the phase changeable layer 300 are transformed into an upper
electrode 410 and a phase changeable pattern 310, respectively. The
mask pattern 500 is then removed.
[0031] The chorine-containing compound may be chorine (Cl.sub.2) or
boron trichloride (BCI.sub.3). The fluorine-containing compound may
be tetrafluoromethane (CF.sub.4), trifluoromethane (CHF.sub.3),
difluoromethane (CH.sub.2F.sub.2), monofluoromethane (CH.sub.3F).
These may be used alone or in a combination thereof.
[0032] The first material may further include a diluent. The
diluent can be selected from the group consisting of helium (He),
neon (Ne), argon (Ar), krypton (Kr), xenon (Xe) or radon (Rn).
These may be used alone or in a combination thereof. It is
preferred to have the first material in a plasma state.
[0033] After the etching step, a second material including an
oxygen-containing compound (e.g., oxygen (O.sub.2) plasma or water
vapor (H.sub.2O) plasma or both) can be provided to the upper
electrode 410 and the phase changeable pattern 310. When the second
material is provided to the upper electrode 410 and the phase
changeable pattern 310, it is believed that chlorine, fluorine and
carbon residing on a sidewall of the phase changeable pattern 310
and between the upper electrode 410 and the phase changeable
pattern 310 may be removed. Here, the second material may be
provided to the upper electrode 410 and the phase changeable
pattern 310 in-situ.
[0034] Particularly, chlorine residing on a sidewall of the phase
changeable pattern 310 and between the upper electrode 410 and the
phase changeable pattern 310 may be converted into the following
reaction products: chlorine dioxide (ClO.sub.2), dichlorine
monoxide (Cl.sub.2O), dichlorine heptoxide (Cl.sub.2O.sub.7),
hydrogen chloride (HCl) and the like. The boiling points of
chlorine dioxide, dichlorine monoxide, dichlorine heptoxide and
hydrogen chloride are about -76.degree. C., about -121.degree. C.,
about -91.degree. C. and about -114.degree. C., respectively.
Because the boiling points of these chlorine-based reaction
products are relatively low, they may be removed via diffusion or
convection from the sidewall of the phase changeable pattern 310
and an interface between the upper electrode 410 and the phase
changeable pattern 310.
[0035] Similarly, fluorine residing on the sidewall of the phase
changeable pattern 310 and between the upper electrode 410 and the
phase changeable pattern 310 may be converted into the following
reaction products: carbonyl fluoride (CF.sub.2O), hydrogen fluoride
(HF) and the like. Boiling points of carbonyl fluoride and hydrogen
fluoride are about -83.1.degree. C. and about -83.5.degree. C.,
respectively. Because the boiling points of these fluorine-based
reaction products are relatively low, they may also be removed via
diffusion or convection from the sidewall of the phase changeable
pattern 310 and the interface between the upper electrode 410 and
the phase changeable pattern 310.
[0036] Likewise, carbon residing on the sidewall of the phase
changeable pattern 310 and between the upper electrode 410 and the
phase changeable pattern 310 may be converted into the following
reaction products: carbonyl fluoride, carbon monoxide (CO), carbon
dioxide (CO.sub.2), carbon dioxide and the like. Boiling points of
carbonyl fluoride, carbon monoxide and carbon dioxide are about
-83.1.degree. C., about -191.5.degree. C. and about -78.degree. C.,
respectively. Because the boiling points of these carbon-based
reaction products are relatively low, they may also be removed via
diffusion or convection from the sidewall of the phase changeable
pattern 310 and the interface between the upper electrode 410 and
the phase changeable pattern 310.
[0037] It is preferred to provide the second material at a
sufficient temperature and pressure and for a sufficient duration
to maximize the formation of the reaction products of the chlorine,
fluorine, carbon, or any combination thereof with the second
material.
[0038] For example, it is preferred to provide the second material
into the chamber at a temperature from about 40.degree. C. to about
150.degree. C. At a temperature lower than about 40.degree. C., it
is believed that the chlorine, fluorine and carbon (e.g., residing
on the sidewall of the phase changeable pattern 310 and between the
upper electrode 410 and the phase changeable pattern 310) may not
sufficiently react with the second material and be removed. On the
other hand, if the temperature is higher than about 150.degree. C.,
the upper electrode 410 and the phase changeable pattern 310 may be
thermally damaged.
[0039] Similarly, it is preferred to provide the second material
for a duration from about 80 seconds to about 100 seconds at the
above specified temperature ranges. When the reaction duration is
less than about 80 seconds at the above specified temperature
ranges, it is believed that chlorine, fluorine and carbon (e.g.,
residing on the sidewall of the phase changeable pattern 310 and
between the upper electrode 410 and the phase changeable pattern
310) may not sufficiently react with the second material and be
removed. On the other hand, when the reaction duration is greater
than about 100 seconds at the above specified temperature ranges,
the upper electrode 410 and the phase changeable pattern 310 may be
thermally damaged. For example, the second material can be provided
to the upper electrode 410 and the phase changeable pattern 310 for
about 90 seconds.
[0040] In accordance with the present invention, chlorine, fluorine
and carbon may be removed from the sidewall of the phase changeable
pattern 310 and the interface between the upper electrode 410 and
the phase changeable pattern 310. Thus, defects due to chlorine,
fluorine and carbon (e.g., residing on the sidewall of the phase
changeable pattern 310 and between the upper electrode 410 and the
phase changeable pattern 310) that may be generated in succeeding
processes are decreased.
Experiment
[0041] A hole is formed in an insulating layer, which includes
silicon nitride. A titanium nitride lower electrode is then formed
in the hole. Here, an upper face of the insulating layer is
substantially coplanar with an upper face of the lower
electrode.
[0042] A phase changeable layer is then formed on the insulating
layer and the lower electrode. The phase changeable layer includes
germanium, antimony and tellurium. Here, atomic percentages of
germanium, antimony and tellurium are about 24.8%, about 24.5% and
about 50.6%, respectively.
[0043] A titanium nitride layer is then formed on the phase
changeable layer. The titanium nitride layer and phase changeable
layer are successively etched to form an upper electrode and a
phase changeable pattern, respectively. The titanium nitride layer
and the phase changeable layer are successively etched using a
first material including chlorine, tetrafluoromethane, and argon,
as a diluent. The first material has a plasma state.
[0044] A second material including oxygen plasma and water vapor
plasma is then provided to the upper electrode and the phase
changeable pattern. Here, the second material is provided to the
upper electrode and the phase changeable pattern in-situ, i.e., in
the same chamber.
[0045] The second material is provided while maintaining the
chamber at a temperature of about 100.degree. C. Furthermore, the
second material was provided in the chamber for about 90
seconds.
[0046] The phase changeable structure obtained from the method
above exhibit a reduced number of defects at an upper face portion
of the phase changeable pattern making contact with the upper
electrode, at a side face portion of the phase changeable pattern,
at a lower face portion of the phase changeable pattern making
contact with the insulating layer.
[0047] FIG. 5 is a graph showing electric resistance with respect
to current of a phase changeable structure formed according to the
above-described method.
[0048] Referring to FIG. 5, when the current provided to the phase
changeable pattern is less than about 1.5 mA, the phase changeable
pattern may be in a single crystalline state having a relatively
low electric resistance. On the other hand, when the current
provided to the phase changeable pattern is greater than about 1.5
mA, the phase changeable pattern is in the amorphous state having a
relatively low electric resistance.
Embodiment 2
[0049] FIGS. 6 to 8 are cross-sectional views illustrating a method
of forming a phase changeable structure in accordance with a second
embodiment of the present invention.
[0050] Referring to FIG. 6, a hole 11 is formed in an insulating
layer 101. The insulating layer 101 may be formed using oxide or
nitride. For example, the insulating layer 101 may be formed using
PSG, BPSG, USG, SOG, TEOS, PE-TEOS, FOX, HDP-CVD oxide or silicon
nitride.
[0051] A lower electrode 201 is then formed in the hole 11. The
lower electrode 201 may be formed using metal, metal nitride or
combination thereof. For example, the lower electrode 201 may be
formed using tungsten, titanium, titanium nitride, tantalum,
tantalum nitride, molybdenum nitride, niobium nitride, titanium
silicon nitride, aluminum, titanium aluminum nitride, titanium
boron nitride, zirconium silicon nitride, tungsten silicon nitride,
tungsten boron nitride, zirconium aluminum nitride, molybdenum
silicon nitride, molybdenum aluminum nitride, tantalum silicon
nitride, tantalum aluminum nitride, copper, aluminum copper, alloys
thereof, or combination thereof. Alternatively, the lower electrode
201 may include polysilicon doped with impurities. Here, an upper
face of the insulating layer 101 may be substantially coplanar with
an upper face of the lower electrode 201.
[0052] A phase changeable layer 301 is then formed on the
insulating layer 101 and the lower electrode 201. The phase
changeable layer 301 may include calcogenide. The calcogenide may
include germanium, antimony and tellurium. The calcogenide can also
include dopants such as silicon (Si), aluminum (Al), titanium (Ti),
carbon (C), or any combination thereof.
[0053] A conductive layer 401 including metal is then formed on the
phase changeable layer 301. The conductive layer 401 may be formed
using metal, metal nitride or combination thereof. For example, the
conductive layer 401 may be formed using tungsten, titanium,
titanium nitride, tantalum, tantalum nitride, molybdenum nitride,
niobium nitride, titanium silicon nitride, aluminum, titanium
aluminum nitride, titanium boron nitride, zirconium silicon
nitride, tungsten silicon nitride, tungsten boron nitride,
zirconium aluminum nitride, molybdenum silicon nitride, molybdenum
aluminum nitride, tantalum silicon nitride, tantalum aluminum
nitride, copper, aluminum copper, alloys thereof, or combination
thereof.
[0054] The conductive layer 401 may be formed by a sputtering
process, a chemical vapor deposition process, an electron bean
deposition process, an atomic layer deposition process or a pulse
laser deposition process.
[0055] A mask pattern 501 is then formed on the conductive layer
401. The mask pattern 501 may include material having an etching
selectivity with respect to the conductive layer 401 and the phase
changeable layer 301.
[0056] Referring to FIGS. 6 and 7, a first etching process is
performed on the conductive layer 401 by using the mask pattern 501
as an etch mask. Thus, the conductive layer 401 may be transformed
into an upper electrode 411. The first etching process is performed
using a first material including a chlorine-containing compound.
Nonlimiting examples of chlorine-containing compounds include
chlorine (Cl.sub.2) and boron trichloride (BCl.sub.3).
[0057] Although not illustrated in FIG. 7, a portion of the phase
changeable layer 301 can be partially removed by the first etching
process. Since the etch rate of the first material with respect to
the phase changeable layer 301 can be substantially larger than the
etch rate of the first material with respect to the conductive
layer, it may be difficult to stop the etching process exactly at
the beginning of the phase changeable layer 301.
[0058] A curing process can then be performed on the upper
electrode 411 and the phase changeable layer 301 in a chamber
having a source electrode and a bias electrode. A second material
including a fluorine-containing compound can be provided to the
upper electrode 411 and the phase changeable layer 301 in the
curing process. Nonlimiting examples of the fluorine-containing
compound include tetrafluoromethane, trifluoromethane,
difluoromethane or monofluoromethane. These may be used alone or in
a combination thereof. The curing process may be performed
in-situ.
[0059] The second material may further include a diluent. The
diluent may be helium, neon, argon, krypton, xenon or radon. These
may be used alone or in a combination thereof. It is preferred to
have the second material in a plasma state.
[0060] When the curing process is performed on the upper electrode
411 and the phase changeable layer 301, it is believed that defects
due to chlorine existing on the phase changeable layer and between
the upper electrode 411 and the phase changeable layer 301 may be
decreased.
[0061] The bias electrode can be installed at a chuck located at a
lower portion of the chamber. The chuck typically supports the
upper electrode 411 and the phase changeable layer 301. The source
electrode can be located at an upper portion of the chamber. Here,
the source electrode and the bias electrode can be utilized to
change a state of the second material into the plasma state.
[0062] Particularly, a first electric power and a second electric
power can be applied to the source electrode and the bias
electrode, respectively. When a ratio of the first electric power
to the second electric power is less than about 2.5:1, it is
believed that the efficiency of the curing process can be low. On
the other hand, when the ratio of the first electric power to the
second electric power is greater than about 10:1, it can be
difficult to control the curing process effectively. Thus, it is
preferred to have the ratio of the first electric power to the
second electric power at a ratio of about 2.5:1 to about 10:1. It
is more preferable to have the ratio of the first electric power to
the second electric power at about 5:1. That is, the first electric
power and the second electric power are about 1,000 Watt and about
200 Watt, respectively.
[0063] When a pressure of the chamber is less than about 1 mTorr,
it is believed that the efficiency of the curing process is low. On
the other hand, when the pressure of the chamber is greater than
about 10 mTorr, it can be difficult to control the first etching
process effectively. Thus, it is preferred to maintain the pressure
of the chamber at about 1 mTorr to about 10 mTorr. It is more
preferable to maintain the pressure of the chamber at about 5
mTorr.
[0064] When a flow ratio of the first component with respect to the
second component is less than about 1:4, it is believed that
undesirable byproducts, such as metal fluoride, may be generated.
On the other hand, when the flow ratio of the first component with
respect to the second component is greater than about 3:2, the
efficiency of the curing process can be low. Thus, it is preferred
to have the flow ratio of the first component with respect to the
second component at about 1:4 to about 3:2. It is more preferred to
have the flow ratio of the first component with respect to the
second component at about 2:3.
[0065] When the curing process is performed for less than about 5
seconds, it is believed that the efficiency of the curing process
may be degraded. On the other hand, when the curing process is
performed for more than about 15 seconds, the second material may
partially remove the upper electrode 411 and the phase changeable
layer 301. Thus, it is preferred to conduct the curing process for
about 5 seconds to about 15 seconds. For example, the curing
process may be performed for about 10 seconds.
[0066] Referring to FIG. 8, a second etching process is performed
on the phase changeable layer 301 by using a third material that is
substantially free of chlorine. Nonlimiting examples of etchants
that are substantially free of chlorine include hydrogen bromide
(HBr), argon (Ar), helium (He), neon (Ne), xenon (Xe), and any
combination thereof. Thus, a phase changeable pattern 311 may be
formed between the upper electrode 411 and the lower electrode 201.
The mask pattern 501 is then removed.
[0067] When the third material includes chlorine, it is believed
that chlorine may be chemically reacted with the phase changeable
layer 301 to generate defects. Particularly, the defects may be
generated at a side face portion of the phase changeable pattern
311.
[0068] Particularly, when the phase changeable layer 301 includes
germanium, antimony and tellurium, a chemical reaction between
chlorine and antimony may occur. Thus, atomic percentages of
antimony may decrease. As a result, it is desirable that the second
material does not include chlorine.
[0069] According to the present embodiment, the curing process is
performed after the conductive layer 411 is etched and before the
phase changeable layer 301 is etched. Thus, the defects due to
chlorine residing on the sidewall of the phase changeable pattern
301 and between the upper electrode 411 and the phase changeable
pattern 301 may be prevented.
[0070] According to the present invention, the reduced number of
defects may be generated at a side face of a phase changeable
pattern and between an upper electrode and the phase changeable
pattern.
[0071] The foregoing is illustrative of the present invention and
is not to be construed as limiting thereof. Although a few
embodiments of this invention have been described, those skilled in
the art will readily appreciate that many modifications are
possible in the embodiments without materially departing from the
novel teachings and advantages of this invention. Accordingly, all
such modifications are intended to be included within the scope of
this invention as defined in the claims. Therefore, it is to be
understood that the foregoing is illustrative of the present
invention and is not to be construed as limited to the specific
embodiments disclosed, and that modifications to the disclosed
embodiments, as well as other embodiments, are intended to be
included within the scope of the appended claims. The invention is
defined by the following claims, with equivalents of the claims to
be included therein.
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