U.S. patent application number 15/882666 was filed with the patent office on 2019-03-21 for phase change memory stack with treated sidewalls.
The applicant listed for this patent is Micron Technology, Inc.. Invention is credited to Tsz W. Chan, Yongjun Jeff Hu, Swapnil Lengade, Everett Allen McTeer, Shu Qin.
Application Number | 20190088867 15/882666 |
Document ID | / |
Family ID | 54355856 |
Filed Date | 2019-03-21 |
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United States Patent
Application |
20190088867 |
Kind Code |
A9 |
Chan; Tsz W. ; et
al. |
March 21, 2019 |
PHASE CHANGE MEMORY STACK WITH TREATED SIDEWALLS
Abstract
Memory devices and methods for fabricating memory devices have
been disclosed. One such method includes forming the memory stack
out of a plurality of elements. An adhesion species is formed on at
least one sidewall of the memory stack wherein the adhesion species
has a gradient structure that results in the adhesion species
intermixing with an element of the memory stack to terminate
unsatisfied atomic bonds of the element. The gradient structure
further comprises a film of the adhesion species on an outer
surface of the at least one sidewall. A dielectric material is
implanted into the film of the adhesion species to form a
sidewall
Inventors: |
Chan; Tsz W.; (Boise,
ID) ; Hu; Yongjun Jeff; (Boise, ID) ; Lengade;
Swapnil; (Boise, ID) ; Qin; Shu; (Boise,
ID) ; McTeer; Everett Allen; (Eagle, ID) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Micron Technology, Inc. |
Boise |
ID |
US |
|
|
Prior
Publication: |
|
Document Identifier |
Publication Date |
|
US 20180166629 A1 |
June 14, 2018 |
|
|
Family ID: |
54355856 |
Appl. No.: |
15/882666 |
Filed: |
January 29, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
15090292 |
Apr 4, 2016 |
10079340 |
|
|
15882666 |
|
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|
|
14266415 |
Apr 30, 2014 |
9306159 |
|
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15090292 |
|
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 45/1233 20130101;
H01L 45/144 20130101; H01L 45/12 20130101; H01L 45/165 20130101;
H01L 45/16 20130101; H01L 27/2481 20130101; G11C 13/0004 20130101;
H01L 45/1616 20130101; H01L 45/06 20130101; H01L 45/1675 20130101;
H01L 27/2409 20130101; H01L 45/141 20130101; H01L 27/2427 20130101;
H01L 45/1253 20130101 |
International
Class: |
H01L 45/00 20060101
H01L045/00; G11C 13/00 20060101 G11C013/00; H01L 27/24 20060101
H01L027/24 |
Claims
1. A method of fabricating a memory stack, comprising: forming the
memory stack comprising multiple stacked elements, the memory stack
defined in part by sidewalls; forming an adhesion species on at
least one sidewall of the memory stack, including intermixing the
adhesion species with an element of the memory stack, and further
including forming a film of the adhesion species on an outer
surface of the intermixed adhesion species; and implanting a
dielectric material into the adhesion species film.
2. The method of claim 1, wherein intermixing the adhesion species
with the element comprises implanting the adhesion species into the
sidewall of the element.
3. The method of claim 2, wherein implanting the adhesion species
into the sidewall of the element comprises performing a plasma
doping process at an energy less than 3 keV.
4. The method of claim 1, wherein implanting the dielectric
material into the adhesion species film comprises a plasma doping
process at an energy within the range of 0-2 keV.
5. The method of claim 1, wherein forming the adhesion species
comprises performing both a plasma doping process and a deposition
process.
6. The method of claim 5, wherein performing the plasma doping
process comprises performing a plasma doping of boron into the
sidewall of the element of the memory stack.
7. The method of claim 6, wherein implanting the dielectric
material into the film comprises implanting a nitride forming
material into the film to form a boron and nitride (BN.sub.x)
dielectric film.
8. The method of claim 1, wherein forming the memory stack
comprising forming multiple stacked elements comprising: forming a
word line material; forming a first electrode material over the
word line material; forming a variable resistance material over the
second electrode material; and firming a second electrode material
over the phase change material.
9. The method of claim 8, wherein at east one of the st and second
electrode materials includes carbon.
10. The method of claim 9, wherein the boron adhesion species
terminates unsatisfied atomic bonds of the carbon.
11. The method of claim 8, wherein forming the word line material
comprisesforming a material including tungsten.
12. A memory structure, comprising: multiple memory stacks, each
memory stack including, an electrode, a variable resistance
material comprising a chalcogenide material, the variable
resistance material disposed to a first side of the electrode in
the memory stack, and wherein at least the electrode has a surface
doped with an adhesion species that intermixes with the material of
the electrode, and a film comprising the material of the adhesion
species formed over at least doped surface of the electrode.
13. The memory device of claim 12, wherein electrode comprises
carbon, and wherein the adhesion species comprises boron.
14. The memory device of claim 12, further comprising a dielectric
material liner implanted into the adhesion species film.
15. The memory device of claim 14, wherein the adhesion species
comprises boron and the implanted dielectric material liner
comprises boron and nitride (BN.sub.X).
16. The memory device of claim 14, wherein the variable resistance
material comprises one or more of Germanium (Ge), Antimony (Sb),
Tellurium (Te), Indium (In), Aluminum (Al), Gallium (Ga), Tin (Sn),
Bismuth (Bi), Sulphur (S), Oxygen (O), Gold (Au), Palladium (Pd),
Copper (Cu), Cobalt (Co), Silver (Ag), and/or Platinum (Pt).
17. A method for fabricating a memory device comprising: forming
multiple memory stacks defined in part by sidewalls, each memory
stack fabricated by: forming a first electrode over a word line
material; forming a variable resistance material over the first
electrode; forming a second electrode over the variable resistance
material; and patterning and etching the first and second
electrodes and the variable resistance material to form the
multiple memory stacks; forming an adhesion species on at least one
sidewall of each of multiple memory stacks using a doping process
and a deposition process, wherein the adhesion species comprises a
first portion implanted to intermix with at least one element of
the memory stack, and a second portion comprising a film of the
adhesion species over the first portion; and forming a liner
material on the sidewalls of multiple memory stacks by implanting a
dielectric material into the film of the adhesion species.
18. The method of claim 17, wherein forming the adhesion species
comprises forming a gradient structured adhesion species on the
sidewalls, comprising: using a plasma doping process to implant a
boron species; and using a deposition process to form a boron film
on the sidewall over the implanted boron species.
19. The method of claim 17, wherein ning the liner material
comprises forming a boron and nitride (BN.sub.X) liner iia over at
least one of the first and second electrodes.
20. The method of claim 17, further comprising forming a dielectric
fill material between pairs of the memory stacks.
21. The method of claim 17, wherein forming the liner material
comprises forming the liner material through a plasma doping
process at a temperature of less than 390.hoarfrost. C.
Description
PRIORITY APPLICATION
[0001] This application is a continuation of U.S. application Ser.
No. 15/090,292, filed Apr. 4, 2016, which is a divisional of U.S.
application Ser. No. 14/266,415, filed Apr. 30, 2014, now issued as
U.S. Pat. No. 9,306,159, all of which are incorporated herein by
reference in their entireties.
BACKGROUND
[0002] Memory devices are typically provided as internal,
semiconductor, integrated circuits in apparatuses such as computers
or other electronic devices. There are many different types of
memory including random-access memory (RAM), read only memory
(ROM), dynamic random access memory (DRAM), synchronous dynamic
random access memory (SDRAM), and non-volatile (e.g., phase change
memory, flash) memory.
[0003] Non-volatile memories are important elements of integrated
circuits due to their ability to maintain data absent a power
supply. Phase change materials have been investigated for use in
non-volatile memory cells. Phase change memory (PCM) elements
include phase change materials, such as chalcogenide alloys, that
are capable of stably transitioning between amorphous and
crystalline phases. Each phase exhibits a particular resistance
state and the resistance states distinguish the logic values of the
memory element. Specifically, an amorphous state exhibits a
relatively high resistance and a crystalline state exhibits a
relatively low resistance. One of different logic levels (e.g.,
logic 1 or logic 0) can be assigned to each of these states.
[0004] There are general needs to improve PCM devices.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] FIG. 1 illustrates a cross-sectional view of a typical phase
change memory stack.
[0006] FIGS. 2-7 illustrate an embodiment of a process flow to
fabricate a phase change memory stack having treated sidewalls.
[0007] FIG. 8 illustrates a block diagram of a memory system in
accordance with the embodiments of FIGS. 2-7.
[0008] FIG. 9 illustrates a plot of adhesion species deposition
depth versus pulse voltage.
[0009] FIG. 10 illustrates a plot of adhesion species deposition
depth versus implant nominal dose.
DETAILED DESCRIPTION
[0010] As described subsequently, a method for fabricating a memory
stack (e.g., memory device) with treated sidewalls can increase the
adhesion of dielectric passivation material to the electrodes. This
can reduce inter-diffusion between the electrodes and adjacent
materials in the memory stack.
[0011] FIG. 1 illustrates a typical memory cell stack for a PCM.
Carbon can be used as top 101, middle 102, and bottom 103
electrodes for the memory cell stack. Carbon is chemically inert
and does not react easily with the phase change material 110 or the
selector device material 111. This inert chemistry can also lead to
poor adhesion of sidewalls to the carbon electrodes. As a result,
it can be possible for the sidewall material 120, 121 to
inter-diffuse 130, 131 between the selector device material 111 and
the phase change material 110. This can occur at higher local
temperatures during device operation. The inter-diffusion can cause
reliability issues, degrade leakage current, and affect threshold
voltage stability.
[0012] FIGS. 2-7 illustrate various steps in fabricating a memory
stack (e.g., PCM) in addition to treating the sidewalls of the
memory stack with an adhesion species. These fabrication steps are
for purposes of illustration only as the different elements of the
stack can be formed by different processes.
[0013] FIG. 2 illustrates an embodiment of a blanket deposition of
the initial memory stack material 200. The memory stack can include
a word line material (e.g., tungsten (W)) 201. A first electrode
material 202 (e.g., carbon) can be formed on the word line material
201. A selector device material 203 may be formed on the first
electrode material 202.
[0014] The selector device material 203 (SD) may include Selenium
(Se), Arsenic (As), Germanium (Ge), Tin (Sn), Tellurium (Te),
Silicon (Si), Lead (Pb), Carbon (C), or Bismuth (Bi) as well as
other materials. Other embodiments can include selector device
material 203 comprising one or more of these elements as well as
one or more of these elements combined with other elements.
[0015] A second electrode material 204 (e.g., carbon) can be formed
on the selector device material 203. A phase change material 205
can be formed on the second electrode material 204.
[0016] The phase change material 205 (PM) can include chalcogenide
elementssuch as Germanium (Ge), Antimony (Sb), Tellurium (Te),
Indium (In) as well as other chalcogenide elements, combinations of
these elements, or combinations of these element with other
elements. The phase change material 205 can additionally include
Aluminum (Al), Gallium (Ga), Tin (Sn), Bismuth (Bi), Sulphur (S),
Oxygen (O), Gold (Au), Palladium (Pd), Copper (Cu), Cobalt (Co),
Silver (Ag), or Platinum (Pt) as well as other elements. Additional
embodiments can combine these elements with the chalcogenide
elements.
[0017] A third electrode material 206 (e.g., carbon) can be formed
on the phase change material 205. Forming the third electrode
material 206, as well as the other materials 201-205 of the memory
stack, can be done with a blanket deposition method or some other
deposition method.
[0018] After the initial memory stack material 200 has been formed,
an etch process (e.g., dry etch) can be performed on the stack
material 200 to create trenches 301-304 as illustrated in FIG. 3.
FIG. 3 illustrates that the stack material 200 has been divided by
the plurality of trenches 301-304 into a plurality of memory stacks
311-315, each stack comprising the architecture illustrated in FIG.
2.
[0019] In another embodiment, the stack material 200 can be dry
etched patterned in both x and y directions. Thus, subsequent
sidewall liners can be added on four sidewalls, as illustrated in
FIG. 7.
[0020] FIG. 4 illustrates the treatment of the sidewalls of
particular ones of the stack 311-315 as formed in FIG. 3. This
treatment enhances the dielectric liner adhesion to the electrode
surfaces. In an embodiment, a plasma immersion technique (e.g.,
plasma doping) can be used to implant an adhesion species in the
stack sidewalls and deposit a dielectric liner (e.g., nitride).
While FIG. 4 illustrates the treatment process with regard to only
one sidewall of one electrode, the sidewalls of the other
electrodes can experience a similar process.
[0021] The sidewall treatment process illustrated in FIG. 4
includes a step 430 of implanting the sidewall of the carbon
electrode(s) 204 with an adhesion species (e.g., boron) using a
relatively low energy (e.g., <3k eV) plasma doping (PLAD)
process 400. This can be accomplished by exposing the sidewall to a
diborane gas (B.sub.2H.sub.6) resulting in a B--C layer 410 as a
result of the boron terminating unsatisfied atomic bonds of the
carbon.
[0022] A subsequent step 431 includes depositing a boron film 411
on the electrode 204. As a result of the PLAD implant/deposition
process 400, a gradient structure 420 of B--C bonds and the boron
film is formed that can be approximately 1-6 nm thick.
[0023] Another step 432 includes implanting a dielectric material
(e.g., nitride (N)) into the B-C gradient 420. For example, a
relatively low energy (e.g., 0-2k eV) NH.sub.3 or N.sub.2/H.sub.2
PLAD process 401 can implant nitrogen atoms into the boron film 411
to form a BN.sub.x film 412 on the carbon electrode 204 sidewall.
The BN.sub.x film 412 can he referred to as the sidewall liners or
dielectric liners.
[0024] The process illustrated in FIG. 4 can sult in a dielectric
liner 412 that can be a few atomic layers thick. If a thicker
BN.sub.x film is desired, the process of FIG. 4 can be
repeated.
[0025] Relatively low energy plasma immersion implant can have
advantages if used in this process. For example, conformal doping
can be used in the process in order to achieve a tunable
implant/deposition operation regime and a shallow profile. The ion
bomb bombardment nature of an implant process can enhance an
adhesion-friendly species (e.g., boron) by intermixing with the
electrode material. For example, the implanted boron can improve
adhesion by species intermixing and terminating unsatisfied atomic
bonds (e.g., carbon bonds). Other adhesion species besides boron
that have similar properties can also be used. This process can he
accomplished at approximately room temperature. To form the PCM
cells, electrically insulated pillars are formed (e.g., by dry
etching) in the hit line direction while the memory stacks are
formed in the word line direction.
[0026] FIG. 5 illustrates the stacks 311-315 as a result of forming
the sidewall liners 500-508 on the sidewalk of the stacks 311-315
as seen in FIG. 4. The process to form the sidewall liners 500-508
can use any dielectric material that can he implanted into the
adhesive species film 411. For purposes of illustration, a
dielectric material like AlSiO, can be used.
[0027] FIG. 6 illustrates an embodiment for forming a dielectric
fill material 601-604 between adjacent memory stacks. The
dielectric fill material 601-604 can electrically isolate each of
the memory stacks. The dielectric fill material 601-604 can he the
same material as the sidewall liners 500-508 or a different
dielectric material.
[0028] FIG. 7 illustrates an embodiment for forming additional
decks of memory stacks. For example, FIG. 7 shows two memory stacks
701, 702 coupled together at a common bit line 703. The sidewalls
or the sidewall liner treatment described previously with reference
to FIG. 4 and below with reference to FIG. 8 may he repeated for
the memory stacks at each of the decks. Other embodiments can have
additional decks of memory stacks 701, 702. This embodiment can be
obtained by a patterned dry etch process in both the x-direction
and the y-direction and the liner added to the far side
sidewall.
[0029] The represented sequence of layers is for purposes of
illustration only. Other embodiments can use other sequences. For
example, the relative position of the PM and select material (SD)
may be exchanged. Also, the relative positions of word line
material and bit line material may be changed (e.g., having hit
lines at the bottom of the first deck and word lines at the top of
the first deck and possibly shared with a second deck stack.
[0030] FIG. 8 illustrates a block diagram of a memory system that
include a memory device 801 that can use the memory stacks with
treated sidewalls of FIGS. 2-7. A controller 800 may be used to
control operations of the system. The memory device 801, coupled to
the controller 800, may include a memory array comprising memory
cell stacks as described above with reference to FIGS. 2-7.
[0031] The controller 800 may be coupled to the memory device 801
over control, data, and address buses. In another embodiment, the
address and data buses may share a common input/output (I/O) bus.
The controller 800 can be part of the same integrated circuit as
the memory device 801 or as separate integrated circuits.
[0032] FIG. 9 illustrates a plot of adhesion species (e.g., boron)
deposition depth (in nanometers) versus pulse voltage. This plot
assumes a B.sub.2H.sub.6/H.sub.2 PLAD process. The plot shows that
the boron deposition layer thickness can be increased at relatively
low energy (e.g., <200 eV) and low temperature (e.g.,
<approximately 390.degree. C.). Implant mode begins to increase
at approximately 200V.
[0033] FIG. 10 illustrates a plot of adhesion species (e.g., boron)
deposition depth (in nanometers) versus implant nominal dose (in
atmospheres/centimeter). This plot shows that, even for higher
energy (e.g., >3k eV), the implant/deposition intermixing mode
can increase the adhesion species deposition thickness with
dose.
[0034] As used herein, an apparatus may refer to, for example,
circuitry, an integrated circuit die, a memory device, a memory
array, or a system including such a circuit, die, device or
array.
Conclusion
[0035] One or more embodiments of the method for memory stack
sidewall treatment can result in a memory device with memory stacks
having enhanced adhesion to the sidewall liners. For example, an
adhesion species (e.g., boron) can intermix with particular
materials of the memory stack to create better adhesion and, thus,
reduced sidewall material inter-diffusion. The adhesion species can
be implanted in the sidewalls using a PLAD implant/deposition
process to form a gradient of boron film and an atomic intermixed
structure of boron and carbon. A dielectric forming material :e.g.,
N) can then be implanted into the film to form a BN.sub.x sidewall
liner.
[0036] Although specific embodiments have been illustrated and
described herein, it will be appreciated by those of ordinary skill
in the art that any arrangement that is calculated to achieve the
same purpose may be substituted for the specific embodiments shown.
Many adaptations will be apparent to those of ordinary skill in the
art. Accordingly, this application is intended to cover any
adaptations or variations.
* * * * *