U.S. patent application number 15/338950 was filed with the patent office on 2017-10-19 for thin film device encapsulation using volume change accommodating materials.
The applicant listed for this patent is Applied Materials, Inc.. Invention is credited to Jeffrey L. Franklin, Byung-Sung Kwak, Giback Park, Lizhong Sun, Robert Jan Visser, Michael Yu-Tak Young.
Application Number | 20170301897 15/338950 |
Document ID | / |
Family ID | 60038434 |
Filed Date | 2017-10-19 |
United States Patent
Application |
20170301897 |
Kind Code |
A1 |
Young; Michael Yu-Tak ; et
al. |
October 19, 2017 |
THIN FILM DEVICE ENCAPSULATION USING VOLUME CHANGE ACCOMMODATING
MATERIALS
Abstract
A thin film device, comprising: an active device region, the
active device region having reversible motion at least along a
first direction between a first device state and a second device
state; and a thin film encapsulant disposed adjacent the selective
expansion region, wherein the thin film encapsulant comprises a
first thickness in the first device state and a second thickness in
the second device state, the first thickness being greater than the
second thickness by 10% or greater, wherein the thin film
encapsulant comprises a laser-etchable material.
Inventors: |
Young; Michael Yu-Tak;
(Cupertino, CA) ; Kwak; Byung-Sung; (Portland,
OR) ; Park; Giback; (San Jose, CA) ; Sun;
Lizhong; (San Jose, CA) ; Franklin; Jeffrey L.;
(Albuquerque, NM) ; Visser; Robert Jan; (Menlo
Park, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Applied Materials, Inc. |
Santa Clara |
CA |
US |
|
|
Family ID: |
60038434 |
Appl. No.: |
15/338950 |
Filed: |
October 31, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62322415 |
Apr 14, 2016 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01M 2/0287 20130101;
H01M 2/0267 20130101; H01M 2300/0068 20130101; B29L 2031/3468
20130101; C23C 14/50 20130101; H01J 37/3426 20130101; H01M 2220/30
20130101; H01M 10/0525 20130101; H01M 4/382 20130101; B23K 2101/34
20180801; H01M 10/0585 20130101; B23K 26/142 20151001; H01M 6/188
20130101; H01M 10/052 20130101; Y02T 10/70 20130101; H01M 6/005
20130101; B23K 26/362 20130101; H01M 6/18 20130101; B23K 26/0006
20130101; B23K 2103/172 20180801; H01M 10/0436 20130101; H01M
2300/0065 20130101; H01M 4/525 20130101; H01M 6/40 20130101; B29C
59/16 20130101; Y02E 60/10 20130101; H01M 2/1094 20130101; H01M
2/08 20130101; H01J 37/32715 20130101; C23C 14/34 20130101; H01M
2/026 20130101; H01M 2/0207 20130101; B29K 2995/0006 20130101; B23K
2101/36 20180801 |
International
Class: |
H01M 2/10 20060101
H01M002/10; H01M 2/08 20060101 H01M002/08; H01M 2/02 20060101
H01M002/02; H01M 10/0525 20100101 H01M010/0525; H01M 10/0585
20100101 H01M010/0585 |
Claims
1. A thin film device, comprising: an active device region, the
active device region having reversible motion at least along a
first direction between a first device state and a second device
state; and a thin film encapsulant disposed adjacent the active
device region, wherein the thin film encapsulant comprises a first
thickness in the first device state and a second thickness in the
second device state, the first thickness being greater than the
second thickness by 10% or greater, wherein the thin film
encapsulant comprises a laser-etchable material.
2. The thin film device of claim 1, wherein the active device
region comprises: a source region comprising a diffusant; and a
selective expansion region, wherein transport of the diffusant
takes place from the source region to the selective expansion
region.
3. The thin film device of claim 2, wherein the source region
comprises a solid state cathode, and wherein the selective
expansion region comprises an anode.
4. The thin film device of claim 3, wherein the anode comprises a
third thickness in the first device state and a fourth thickness in
the second device state, wherein a sum of the first thickness and
third thickness differs by 10% or less from a sum of the second
thickness and fourth thickness.
5. The thin film device of claim 2, wherein the thin film
encapsulant comprises a polymer layer disposed adjacent the
selective expansion region.
6. The thin film device of claim 1, wherein the thin film
encapsulant comprises a multilayer stack, the multilayer stack
including at least one polymer layer.
7. The thin film device of claim 1, the thin film encapsulant
comprising at least one of: a getter/absorbent infused silicone, a
porous low dielectric constant material, a silver paste, and epoxy,
a printed circuit board) material, a photo-resist material,
silicone, rubber, urethane, polyurethane, polyurea,
polytetrafluoroethylene, parylene, polypropylene, polystyrene,
polyimide, nylon, acetal, ultem, acrylic, epoxy, and phenolic a
polymer, or combination thereof.
8. The thin film device of claim 1, the thin film encapsulant
comprising a plurality of dyads, a dyad comprising a polymer layer
and at least one of: a rigid dielectric layer and a metal
layer.
9. The thin film device of claim 8, wherein the polymer layer
comprises a polymer stack, the polymer stack including a plurality
of polymer sub-layers, wherein at least one sub-layer of the
plurality of polymer sub-layers.
10. The thin film device of claim 2, the thin film device
comprising a lithium thin film battery, the active device region
comprising a cathode of the lithium thin film battery, the
selective expansion region comprising an anode of the lithium thin
film battery.
11. The thin film device of claim 10, further comprising a solid
state electrolyte disposed between the anode and the cathode,
wherein the thin film encapsulant encapsulates the cathode, the
anode, and the solid state electrolyte.
12. The thin film device of claim 2, the thin film encapsulant
comprising a polymer layer arranged as a polymer layer stack having
a thickness of 10 um to 50 um, the selective expansion region
comprising an anode, wherein an anode thickness changes by at least
1 um between the first device state and the second device
state.
13. A thin film battery, comprising: a cathode region comprising a
diffusant; an anode, wherein transport of the diffusant takes place
between the cathode region and the anode; and a thin film
encapsulant disposed adjacent the anode, wherein the thin film
encapsulant comprises a first thickness in a first device state and
a second thickness in a second device state, the first thickness
being greater than the second thickness by 10% or greater, wherein
the thin film encapsulant comprises a laser-etchable material.
14. The thin film battery of claim 13, wherein the thin film
encapsulant comprises a layer absorbent to laser radiation at a
wavelength in a range of 157 nm to 1064 nm.
15. The thin film battery of claim 13, the thin film encapsulant
comprising at least one of: a getter/absorbent infused silicone, a
porous low dielectric constant material, a silver paste, and epoxy,
a printed circuit board material, a photo-resist material,
silicone, rubber, urethane, polyurethane, polyurea,
polytetrafluoroethylene, parylene, polypropylene, polystyrene,
polyimide, nylon, acetal, ultem, acrylic, epoxy, and phenolic a
polymer, or combination thereof.
16. The thin film battery of claim 13, wherein the anode comprises
a third thickness in the first device state and a fourth thickness
in the second device state, wherein a sum of the first thickness
and third thickness differs by 10% or less from a sum of the second
thickness and fourth thickness.
Description
RELATED APPLICATIONS
[0001] This Application claims priority to U.S. provisional patent
application No. 62/322,415, filed Apr. 14, 2016, entitled Volume
Change Accommodating TFE Materials, and incorporated by reference
herein in its entirety.
FIELD
[0002] The present embodiments relate to thin film encapsulation
(TFE) technology used to protect active devices, and more
particularly to encapsulating electrochemical devices.
BACKGROUND
[0003] Thin film encapsulation technology is often employed in
devices where the devices are purely electrical devices or
electro-optical devices, such as Organic Light Emitting Diodes
(OLED). Other than possibly experiencing a generally small global
thermal expansion from heat generation during the device operation,
these electrical devices and electro-optical devices do not exhibit
volume changes during operation, since just electrons and photons
are transported within the devices during operation. Such global
effects due to global thermal expansion of a device may affect in a
similar fashion every component of a given device including the
thin film encapsulant, and thus, may not lead to significant
internal stress. In this manner, the functionality of the thin film
encapsulant in a purely electrical device or electro-optic device
is not generally susceptible to stresses from non-uniform expansion
during operation.
[0004] Notably, in an electrochemical device ("chemical" portion),
matter such as elements, ions, or other chemical species having a
physical volume (the physical volume of electrons may be considered
to be approximately zero) are transported within the device during
operation with physical volume move. For known electrochemical
devices, e.g., a lithium thin film battery (LiTFB) based upon
lithium (Li), Li is transported from one side to the other side of
a battery as electrons are transported in an external circuit
connected to the LiTFB, where the electrons move in an opposite
direction to the chemical and elements. One particular example of
the volume change experienced by a LiTFB is as follows. When
charging a thin film battery having a lithium cobalt oxide
(LiCoO.sub.2) cathode (.about.15 .mu.m to 17 .mu.m thick
LiCoO.sub.2), an amount of Li equivalent to several micrometers
thick layer, such as 6 micrometers (assuming 100% density), may be
transported to the anode when loading is approximately 1
mAhr/cm.sup.2. When Li returns to the cathode side in a discharge
process, a comparable volume reduction may result on the anode side
(assuming 100% efficiency). The cathode side may also undergo a
volume change in an opposite manner, while such changes are much
smaller as compared to the anode side.
[0005] As such, known thin film encapsulant structures may be
lacking the ability to accommodate such volume change in a robust
manner, to ensure the thin film encapsulant continues to provide
protection of the electrochemical device during repeated cycling of
the device.
[0006] With respect to these and other considerations the present
disclosure is provided.
BRIEF SUMMARY
[0007] In one embodiment, a thin film device may include an active
device region, the active device region having reversible motion at
least along a first direction between a first device state and a
second device state. The thin film device may also include a thin
film encapsulant disposed adjacent the selective expansion region,
wherein the thin film encapsulant comprises a first thickness in
the first device state and a second thickness in the second device
state. The first thickness may be greater than the second thickness
by 10% or greater, wherein the thin film encapsulant comprises a
laser-etchable material.
[0008] In another embodiment, a thin film battery may include a
cathode region comprising a diffusant; an anode, wherein transport
of the diffusant takes place between the cathode region to and the
anode; and a thin film encapsulant disposed adjacent the anode. The
thin film encapsulant may include a first thickness in a first
device state and a second thickness in a second device state, the
first thickness being greater than the second thickness by 10% or
greater, wherein the thin film encapsulant comprises a
laser-etchable material.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1A illustrates a thin film device according to various
embodiments of the disclosure;
[0010] FIG. 1B shows a second instance for operation of the thin
film device of FIG. 1A;
[0011] FIG. 1C provides one embodiment of a thin film encapsulant,
arranged as a dyad, according to embodiments of the disclosure;
and
[0012] FIG. 2A and FIG. 2B illustrate views of a thin film battery
according to various embodiments of the disclosure.
DETAILED DESCRIPTION
[0013] The present embodiments will now be described more fully
hereinafter with reference to the accompanying drawings, where some
embodiments are shown. The subject matter of the present disclosure
may be embodied in many different forms and are not to be construed
as limited to the embodiments set forth herein. These embodiments
are provided so this disclosure will be thorough and complete, and
will fully convey the scope of the subject matter to those skilled
in the art. In the drawings, like numbers refer to like elements
throughout.
[0014] The present embodiments are related to thin film encapsulant
materials and processes, where a thin film encapsulant is used to
minimize ambient exposure of active devices. The present
embodiments provide novel structures and materials combinations for
thin film encapsulants. In various embodiments a thin film
encapsulant may be provided to encapsulate active device regions
where motion takes place within the active device region during
operation. The thin film encapsulant and the active device region
may be referred to herein as a "device." In addition, the active
device region may constitute an active device as detailed below.
The motion within an active device region of the overall device may
extend up to serval micrometers, for example. Examples of active
devices forming all or part of the active device region include
piezoelectric devices, shape memory alloy devices, MEMS device, as
well as electrochemical devices such as thin film batteries wherein
the active component materials are highly sensitive/reactive to
moisture or other ambient materials. To this end, known
electrochemical devices such as thin film batteries may be provided
with encapsulation to protect the active component materials. The
present embodiments also address a problem encountered in devices
such as thin film batteries, where a large physical volume change
(expansion and contraction) may take place during the operation of
the device. More particularly, as noted, volume changes in a device
such as a Li thin film battery may take place in a localized or
non-uniform manner in a "selective expansion" region, such as an
anode. Various embodiments of the disclosure provide appropriate
structures and appropriate thin film encapsulant materials and
methods of applying such materials in a device, such as a thin film
battery, resulting in device structures meeting stringent thin film
encapsulant requirements. The present embodiments may also provide
structures and materials in a thin film encapsulant serving a
combination of other functions. These other functions may include
providing improved planarization capability, chemical stability
when in contact with diffusant species such as Li, and adequate
absorption of laser irradiation over given wavelengths, to provide
maskless patternability.
[0015] In various embodiments, a device such as a thin film device,
is provided with a novel thin film encapsulant region (or, simply,
"thin film encapsulant"). As noted, the device may be a
piezoelectric device, shape memory alloy device, MEMS device in
some embodiments. In other embodiments, the film device may be a
thin film battery or electrochromic window. In these embodiments,
the active device region may exhibit reversible motion at least
along a first direction between a first device state and a second
device state, where motion takes place over a scale of tenths of
micrometers or up to several micrometers. The embodiments are not
limited in this context. The reversible motion may take place in a
plurality of cycles, such as tens of cycles, hundreds of cycles,
thousands of cycles, millions of cycles, and so forth.
[0016] In embodiments where active device is an electrochemical
device such as a thin film battery, the active device region may
include a source region comprising a diffusant, as well as a
selective expansion region, wherein transport of the diffusant
takes place from the source region to the selective expansion
region. According to various embodiments, the transport of
diffusant may take place reversibly between the source region and
the selective expansion region. In embodiments where the thin film
device is a Li thin film battery, a cathode, such as a solid state
cathode, may act as the source region and may include a material
such as LiCoO.sub.2 or similar material. In embodiments of a Li
thin film battery, an anode may act as a selective expansion
region, where a large volume change takes place selectively in the
selective expansion region, as opposed to other regions in the thin
film device.
[0017] To accommodate changes in volume in a selective expansion
region, various embodiments provide materials and/or structures in
a thin film encapsulant, where the thin film encapsulant is
effective to accommodate volume expansion and contraction in the
selective expansion region, rendering a more robust thin film
device.
[0018] According to various embodiments, the thin film encapsulant
may include at least one layer and may encapsulate at least
portions of the source region and selective expansion region. In
various embodiments, the thin film encapsulant, at least in a
portion adjacent the selective expansion region, may reversibly
vary thickness from a first thickness to a second thickness to
accommodate changes in volume or thickness of materials in the
selective expansion region. For example, in a thin film battery
where an anode or a portion of an anode may constitute a selective
expansion region, as a result of lithium migration, the anode may
change in thickness by several micrometers between a charged state
and a discharged state in the thin film battery. In the present
embodiments, the thin film encapsulant may expand or contract in
thickness to accommodate for the increase or decrease in anode
thickness, resulting in less stress, less mechanical failure, and
better protection of the active device of a thin film device.
Depending upon the thickness of the thin film encapsulant, the
change in thickness between a first thickness in a charged state
and a second thickness in discharged state may be as follows. The
first thickness may be greater than the second thickness by 5% or
more, and in some examples, the first thickness is greater than the
second thickness by 10% or more. The embodiments are not limited in
this context.
[0019] According to various embodiments, the thin film encapsulant
may include at least one layer comprising a laser-etchable material
and in particular a material etchable according to laser ablation
or similar process. In a thin film encapsulant containing a
laser-etchable material, electromagnetic radiation of a given
wavelength of a laser beam is highly absorbed in the thin film
encapsulant. Examples of suitable radiation wavelengths include the
range from 157 nm to 1064 nm. For example, for a laser beam having
a wavelength in the visible range, a transparent or completely
clear-appearing polymer layer may not be highly absorbent of the
electromagnetic radiation of the laser beam. For the same laser
beam having wavelength in the visible range, an opaque, black, or
translucent polymer layer may be highly absorbent of the
electromagnetic radiation, and may accordingly be deemed a
laser-etchable material. The embodiments are not limited in this
context. In this manner, a patterned thin film device such as a
thin film battery may be formed, where the active device portions
of the thin film battery as well as a volume-change-accommodating
encapsulant can be patterned using a maskless process. A useful
maskless process includes laser patterning, suitable to define the
final device structure including the thin film encapsulant.
[0020] Turning now to FIG. 1A there is shown a thin film device 100
according to embodiments of the disclosure. The thin film device
100 may constitute an electrochemical device such as a thin film
battery, electrochromic window, or other electrochemical device. In
the embodiment of FIG. 1A, the thin film device 100 may include a
substrate 102 and a source region 104 disposed on the substrate
102. In various embodiments the source region 104 may represent a
cathode of a thin film device such as a thin film battery. The
source region 104 may act as a source of a diffusant such as
lithium, where the diffusant may reversibly diffuse from the source
region 104 and into the source region 104. The thin film device 100
may also include an intermediate region 106 disposed on the source
region, and a selective expansion region 108 disposed on the
intermediate region 106. The selective expansion region 108 may be
an anode, for example, of a thin film device. In the instance shown
in FIG. 1A, the thin film device 100 may represent a thin film
battery in a discharged state where the battery is not charged so
charge species such as lithium are depleted from the anode. In this
example, the selective expansion region 108 remains relatively
contracted, while the thin film encapsulant 110 is relatively
expanded or relaxed, as represented by the first thickness, ti,
along the X-axis of the Cartesian coordinate system shown.
[0021] Turning now to FIG. 1B there is shown a second instance for
operation of the thin film device 100, representing, for example, a
second device state of the thin film device 100. In the instance
shown in FIG. 1B, the thin film device 100 may represent a thin
film battery in a charged state. In the charged state the battery
may be charged by outdiffusion of a diffusant such as lithium from
the source region 104 and the transporting of the diffusant across
intermediate region 106 to accumulate at an anode, represented by
the selective expansion region 108. Accordingly, the selective
expansion region 108 may be expanded with respect to the state of
FIG. 1A, while the thin film encapsulant is relatively compressed
as represented by a second thickness t.sub.2. According to various
embodiments, the change in thickness of the selective expansion
region 108 from a third thickness, t.sub.3, in the discharged state
of FIG. 1A to a fourth thickness, t.sub.4, in the charged state of
FIG. 1B may displace the thin film encapsulant 110. The
displacement of thin film encapsulant 110 may take place at least
in a region 114, where the region 114 is adjacent the selective
expansion region 108. Accordingly, the thin film encapsulant 110
may accommodate the expansion of the selective expansion region 108
by a reduction in thickness of the thin film encapsulant 110 from
the first thickness, t.sub.1, as represented by the discharged
state of FIG. 1A to the second thickness, t.sub.2, as shown in the
charged state of FIG. 1B. Accordingly, the thin film encapsulant
110 may be vertically stretched at the battery cell edges.
[0022] In some embodiments the thin film encapsulant 110 includes a
polymer stack (not separately shown in FIG. 1A) including at least
one polymer layer and a permeation blocking layer, such as a rigid
dielectric layer or a metal layer. In variants of such embodiments,
the individual thicknesses (t.sub.1, t.sub.2, t.sub.3 and t.sub.4)
may change during cycling. At the same time, the thickness of the
at least one polymer layer of thin film encapsulant 110 may be
sufficiently large and the polymer layer sufficiently pliable, so
as to accommodate the expansion and the contraction taking place
during cycling in the following manner. During cycling, where
t.sub.1 and t.sub.2 may represent opposite extremes of thickness,
the thickness and pliability of the polymer layer may be such where
the sum of the first thickness and third thickness differs by 10%
or less from a sum of the second thickness and fourth thickness, as
defined above. This relationship may be expressed symbolically
where the thickness sum of t.sub.2+t.sub.4 is not substantially
different from the thickness sum of t.sub.1+t.sub.3, such as a
difference of less than 10%; and in some cases the thickness sum of
t.sub.2+t.sub.4 differs from the thickness sum of t.sub.1+t.sub.3
by less than 5%. In this manner, the pressure on the permeation
blocking layer of the thin film encapsulant 110 is minimized. As
noted above, in known batteries an amount of Li equivalent to
several micrometers thick layer, such as 6 micrometers (assuming
100% density), may be transported to an anode. Accordingly, various
embodiments of a thin film encapsulant 110 may accommodate
expansion and contraction on the order of at least one micrometer,
and in some cases, several micrometers, such as 6 micrometers or
more. In particular, this accommodation of thickness changes up to
6 micrometers or more may be such where the thickness sum of
t.sub.2+t.sub.4 does not substantially vary from the thickness sum
of t.sub.1+t.sub.3, such as a difference of less than 10%.
[0023] In various embodiments, the thin film encapsulant 110 may
have an elongation property of at least 5%. In particular
embodiments, the elongation to break may be 70% or greater for at
least one polymer layer of the thin film encapsulant.
[0024] According to various embodiments, the thin film encapsulant
110 may include a polymer layer having a thickness of 10 .mu.m to
50 .mu.m, and the selective expansion region 108 may constitute an
anode. The anode thickness may change by at least 1 .mu.m between a
charged state and a discharged state. In specific embodiments, the
polymer layer of the thin film encapsulant 110 may constitute a
polymer layer stack including multiple sub-layers of different
polymers, where at least one sub-layer is soft and pliable. By
proper choice of the thickness of thin film encapsulant and the
materials for a thin film encapsulant, the thin film encapsulant
110 may have adequate flexibility to accommodate expansion and
contraction of at least 1 .mu.m when the thin film device 100 is
cycled between states, such as a charged state and discharged state
in embodiments of a thin film battery. The accommodation of changes
in volume of the selective expansion region 108 may be accomplished
in a manner avoiding stress-induced cracking in the encapsulant
materials, as well as delamination or other degradation, where such
degradation may compromise the integrity of the thin film device
being protected.
[0025] According to various embodiments of the disclosure a thin
film encapsulant may be formed from a multilayer stack, where the
multilayer stack includes at least one polymer layer. In specific
embodiments, a given polymer "layer" is arranged as a polymer layer
stack having a plurality of polymer sub-layers as described above.
In particular embodiments, the thin film encapsulant 110 may
include a getter/absorbent infused polymer material, a porous low
dielectric constant material, an epoxy, a printed circuit board
material, a photo-resist material, or a silver paste, and
combinations thereof. In addition to the aforementioned materials,
particular examples of suitable polymer materials include silicone,
rubber, urethane, polyurethane, polyurea, polytetrafluoroethylene
(PTFE), parylene, polypropylene, polystyrene, polyimide, nylon,
acetal, ultem, acrylic, epoxy, and phenolic polymers. The
embodiments are not limited in this context.
[0026] In various embodiments, the thin film encapsulant 110 may be
arranged with a dyad, where a given dyad includes a polymer layer
and a rigid moisture barrier layer such as a dielectric layer or a
metal layer, or combinations of metal layer and dielectric layer.
The dyad may act as a "functional dyad" where at least one layer of
the functional dyad provides a diffusion barrier to contaminants
such as moisture; and at least one layer includes a soft and
pliable layer for accommodating changes in dimension of an active
device region in a reversible manner. A suitable metal layer may
include Cu, Al, Pt, Au, or other metal. A rigid dielectric layer
may be composed of a known material such as silicon nitride where
the rigid dielectric layer has a combination of relatively high
elastic modulus and hardness, for example. In the case of silicon
nitride, the Vicker's hardness is .about.13 GPa, and Young's
Modulus is .about.43500 Kpsi or .about.300 GPa). Accordingly, the
rigid dielectric layer is less pliable than the polymer layer
(e.g., exemplary mechanical properties of polymer layers include
silicone: hardness of .about.A40 Shore A, Young's Modulus of
.about.0.9 Kpsi or .about.6.2 MPa; Parylene-C: hardness of
.about.Rockwell R80, Young's Modulus of .about.400 Kpsi or
.about.2.8 GPa; KMPR: Young's Modulus of .about.1015 Kpsi or
.about.7.0 GPa; polyimide: hardness of D87 Shore D, Young's Modulus
of .about.2500 Kpsi or .about.17.2 GPa). Other examples of
appropriate rigid dielectric materials include sputtered dielectric
materials (i.e. sputtered Pyrex or similar borosilicate material),
low temperature spin-on or powder coated dielectric or glaze
coatings (processed with or without surface Rapid Thermal
Processing to improve barrier properties).
[0027] As used herein, a "soft and pliable" material may refer to a
material having an elastic (Young's) modulus less than 20 GPa, for
example, while a "rigid material" such as a rigid metal or rigid
dielectric may have an elastic modulus greater than 20 GPa. Other
characteristic properties associated with a soft and pliable
material include a relatively high elongation to break, such as 70%
or greater for at least one polymer layer of the thin film
encapsulant. In some examples, such as silicone, a soft and pliable
material may have an elongation to break up to 200% or greater.
[0028] The dielectric breakdown voltage of a rigid dielectric layer
may exceed 4 MV/cm in some examples. The high dielectric breakdown
strength may in general be an indication of high electrical
resistivity. For rigid dielectrics (and polymers) in a battery of
the present embodiments, a high electrical resistivity, as
indicated by the high dielectric breakdown voltage, prevents
shorting from anode current collector or cathode current collector
through the thin film encapsulant.
[0029] In some embodiments, the thin film encapsulant may be
arranged having a plurality of dyads. FIG. 1C provides one
embodiment of a thin film encapsulant 110, arranged as a dyad. The
dyad may include a polymer layer 120 and a rigid dielectric layer
122, where the rigid dielectric layer 122 may be Si.sub.3N.sub.4,
Al2O.sub.3, ytrria stabilized zirconia (YSZ), ZrO.sub.2, SiO.sub.2,
SiO.sub.xN.sub.y, to name a few materials. In other embodiments,
the rigid dielectric layer 122 may instead by a rigid metal layer.
An advantage of a rigid metal layer is the rigid metal layer may
provide strength while being less brittle than a rigid dielectric
layer.
[0030] Configurations where a polymer layer such as polymer layer
120 is a polymer layer stack including multiple polymer sub-layers
may provide advantages over configurations having just one polymer
layer. For example, a three-layer polymer layer stack may have an
inner polymer layer exhibiting soft and pliable properties and
outer polymer layers, where the outer polymer layers are harder and
function to distribute stress more uniformly. The harder polymer
layers may accordingly reduce localized abnormally high stress
points, where such stress points would otherwise cause puncturing
of the rigid dielectric layer 122, for example.
[0031] Turning now to FIG. 2A and FIG. 2B there are shown views of
a thin film battery 200 according to various embodiments of the
disclosure. The thin film battery 200 may include a substrate 102,
intermediate layer 202, a cathode current collector 204, a cathode
206, a solid state electrolyte 208, an anode 210, a thin film
encapsulant 212, and an anode current collector 214, as shown. In
some examples, the intermediate layer 202 may function as a
bi-directional diffusion barrier layer between substrate 102 and
the stack of layers above substrate 102, and may function as an
"adhesion promotion layer." In one embodiment the intermediate
layer 202 may be composed of Al.sub.2O.sub.3 and titanium. In some
embodiments, a cathode current collector 204, cathode 206, solid
state electrolyte 208, anode 210, and anode current collector 214
may be composed of known materials. For example, the cathode
current collector 204 may be a known metal material, the cathode
may be LiCoO.sub.2 or similar material, the solid state electrolyte
208 may be a lithium phosphorus oxynitride (LiPON), the anode 210
may include lithium or lithium-containing material. The anode
current collector 214 may include a metal such as copper, may be
copper plated with lithium, or another known anode current
collector. The embodiments are not limited in this context. The
thin film encapsulant 212 may be a material or set of materials as
discussed above.
[0032] As shown in FIG. 2A, the thin film battery 200 may have a
co-planar structure where cathode current collector 204 and anode
current collector 214 are arranged in a coplanar fashion. In other
embodiments the cathode current collector 204 and anode current
collector 214 may be arranged in a non-coplanar fashion, for
example, where the anode current collector 214 is arranged in a
plane above the cathode current collector. As illustrated, the thin
film encapsulant 212 encapsulates the cathode 206, solid state
electrolyte 208, and anode 210. During operation, the thin film
encapsulant 212 protects these components from attack from water
vapor or other ambient material. When the thin film battery 200 is
cycled between a charged state (FIG. 2B, where diffusant 216
diffuses to the anode 210) and discharged state (FIG. 2A, where the
diffusant 216 diffuses to the cathode 206), the thin film
encapsulant 212 may elastically deform. In particular embodiments,
the thin film encapsulant 212 may elastically deform in a manner to
accommodate the changes in thickness of the anode 210, as generally
described above with respect to FIG. 1A and FIG. 1B.
[0033] As additionally shown in FIG. 2A and FIG. 2B various
components of thin film battery 200 formed on the substrate 102 may
form a layer stack 220, where the layer stack 220 is patterned so
as to form a discrete battery. The layer stack 220 may be formed by
depositing the different layers and subsequently patterning these
layers to form the thin film battery 200 as shown.
[0034] In various embodiments, at least the thin film encapsulant
212 may be patterned by a laser etching process, in particular by a
maskless laser process, such as laser ablation. The material(s) of
the thin film encapsulant 212, including individual polymer layers,
as well as any rigid dielectric or metal layers, such as a rigid
metal layer, may be designed to absorb the electromagnetic
radiation of a given laser used to perform laser ablation. In some
embodiments, having a laser wavelength in the high energy range
(i.e. green, UV, deep UV) is useful to provide good layer-by-layer
material ablation control. Hence, a thin film encapsulant material
having good light absorption properties in these laser wavelengths
may be patterned more effectively. Providing coloration in a thin
film encapsulant material is useful to enable laser beam
absorption. For example, magenta coloring of a thin film
encapsulant will work well in conjunction with the use of green
lasers since green light absorption is maximized for this color.
Black coloring also works well for thin film encapsulant coloring.
Also, dyes and pigments for use as thin film encapsulant material
coloring material may be selected so as not to have chemical
reactivity with battery cell materials of interest.
[0035] While in some of the aforementioned embodiments suitable
radiation wavelengths may include the range from 266 nm to 1064 nm,
in other embodiments excimer laser radiation may be used to pattern
at least the thin film encapsulant part of a device. In this case
the optical properties of materials such as polymers in the thin
film encapsulant may include a layer absorbent to laser radiation
at a wavelength in a range of 157 nm to 1064 nm. In particular, the
thin film encapsulant may be tuned to be highly absorbent at the
wavelength of a given excimer laser, such as .about.157 nm, 172 nm,
193 nm, 248 nm, 1064 nm. Accordingly, radiation wavelengths useful
for patterning a thin film encapsulant in the present embodiments
may extend between 157 nm to 1064 nm. As disclosed herein above, a
thin film encapsulant may be formed for a thin film device where
the structure and materials of the thin film encapsulant
accommodate selective volume changes taking place within certain
regions (a "selective expansion region") of the thin film device.
The selective volume changes may be reversible volume changes where
a component such as an anode increases in thickness and decreases
in thickness. The materials of the thin film encapsulant may be
tailored so a maskless process, such as laser ablation may be used
to pattern the thin film devices. In this manner, electrochemical
device structures able to accommodate volume expansion during
cycling between different states may be conveniently be formed
using a combination of deposition processes and maskless
patterning.
[0036] There are multiple advantages provided by the present
embodiments, including the ability to reduce the amount of
non-active packaging materials used in a thin film device, leading
to enhanced energy density of these devices, as well as the further
advantage of the ability to conveniently form a thin film device
using maskless patterning of the thin film encapsulant.
[0037] The present disclosure is not to be limited in scope by the
specific embodiments described herein. Indeed, other various
embodiments of and modifications to the present disclosure, in
addition to those described herein, will be apparent to those of
ordinary skill in the art from the foregoing description and
accompanying drawings. Thus, such other embodiments and
modifications are intended to fall within the scope of the present
disclosure. Furthermore, the present disclosure has been described
herein in the context of a particular implementation in a
particular environment for a particular purpose, while those of
ordinary skill in the art will recognize the usefulness is not
limited thereto and the present disclosure may be beneficially
implemented in any number of environments for any number of
purposes. Thus, the claims set forth below are to be construed in
view of the full breadth and spirit of the present disclosure as
described herein.
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