U.S. patent application number 15/338958 was filed with the patent office on 2017-10-19 for multilayer thin film device encapsulation using soft and pliable layer first.
The applicant listed for this patent is Applied Materials, Inc.. Invention is credited to Jeffrey L. Franklin, Byung-Sung Kwak, Giback Park, Lizhong Sun, Miaojun Wang, Michael Yu-Tak Young.
Application Number | 20170301892 15/338958 |
Document ID | / |
Family ID | 60038434 |
Filed Date | 2017-10-19 |
United States Patent
Application |
20170301892 |
Kind Code |
A1 |
Kwak; Byung-Sung ; et
al. |
October 19, 2017 |
MULTILAYER THIN FILM DEVICE ENCAPSULATION USING SOFT AND PLIABLE
LAYER FIRST
Abstract
A thin film device. The thin film device may include: an active
device region, the active device region comprising a diffusant; and
a thin film encapsulant disposed adjacent to the active device
region and encapsulating at least a portion of the active device
region, the thin film encapsulant comprising: a first layer, the
first layer disposed immediately adjacent the active device region
and comprising a soft and pliable material; and a second layer
disposed on the first layer, the second layer comprising a rigid
dielectric material or rigid metal material.
Inventors: |
Kwak; Byung-Sung; (Portland,
OR) ; Sun; Lizhong; (San Jose, CA) ; Park;
Giback; (San Jose, CA) ; Young; Michael Yu-Tak;
(Cupertino, CA) ; Franklin; Jeffrey L.;
(Albuquerque, NM) ; Wang; Miaojun; (San Jose,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Applied Materials, Inc. |
Santa Clara |
CA |
US |
|
|
Family ID: |
60038434 |
Appl. No.: |
15/338958 |
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 2/0267 20130101;
H01J 37/32715 20130101; B23K 26/0006 20130101; H01M 2/0287
20130101; H01M 6/40 20130101; H01M 10/0585 20130101; B23K 2103/172
20180801; H01M 2/08 20130101; B23K 2101/36 20180801; B29K 2995/0006
20130101; H01M 2/0207 20130101; H01M 10/052 20130101; C23C 14/34
20130101; H01M 2/026 20130101; B23K 2101/34 20180801; Y02T 10/70
20130101; B29L 2031/3468 20130101; H01M 2220/30 20130101; B29C
59/16 20130101; B23K 26/142 20151001; C23C 14/50 20130101; H01M
10/0436 20130101; H01J 37/3426 20130101; H01M 2300/0068 20130101;
Y02E 60/10 20130101; H01M 6/005 20130101; H01M 6/18 20130101; H01M
2/1094 20130101; H01M 6/188 20130101; H01M 4/382 20130101; H01M
4/525 20130101; B23K 26/362 20130101; H01M 10/0525 20130101; H01M
2300/0065 20130101 |
International
Class: |
H01M 2/02 20060101
H01M002/02; H01M 2/02 20060101 H01M002/02; H01M 2/02 20060101
H01M002/02; H01M 2/08 20060101 H01M002/08; 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 comprising a diffusant; and a thin film
encapsulant disposed adjacent to the active device region and
encapsulating at least a portion of the active device region, the
thin film encapsulant comprising: a first layer, the first layer
disposed immediately adjacent the active device region and
comprising a soft and pliable material; and a second layer disposed
on the first layer, the second layer comprising a rigid dielectric
material or rigid metal material.
2. The thin film device of claim 1, wherein the active device
region comprises: a source region comprising the diffusant; and a
selective expansion region, the selective expansion region being
disposed immediately adjacent the first layer, wherein transport of
the diffusant takes place reversibly between the source region and
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 thin film
encapsulant comprises a first thickness in a first device state and
a second thickness in a second device state, wherein the anode
comprises a third thickness in the first device state and a fourth
thickness in the second device state, wherein the third thickness
is less than the fourth thickness by at least 1 um.
5. The thin film device of claim 4, 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.
6. The thin film device of claim 1, wherein the first layer
comprises a polymer layer, the polymer layer further comprising a
polymer layer stack including at least one sub-layer.
7. The thin film device of claim 1, the first layer 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 first layer and the second
layer together forming a first dyad, wherein the thin film
encapsulant comprises at least one additional dyad, the at least
one additional dyad being disposed on the first dyad.
9. The thin film device of claim 8, wherein the first layer of the
first dyad comprises a first soft and pliable layer, the first soft
and pliable layer having a first layer thickness and further
comprising at least one sub-layer, wherein a second dyad is
disposed on the first dyad and includes a second soft and pliable
layer having a second layer thickness, wherein the pliable layer
thickness is less than the first layer thickness.
10. The thin film device of claim 1, wherein the second layer
comprises a diffusion barrier layer, the diffusion barrier layer
preventing moisture and gas diffusion through the thin film
encapsulant.
11. The thin film device of claim 1, wherein the second layer
comprises silicon nitride, Cu, or Al.
12. The thin film device of claim 1, wherein the second layer
comprises a thickness of 0.25 .mu.m to 5 .mu.m.
13. The thin film device of claim 1, wherein the first layer and
second layer together constitute a dyad, wherein the thin film
encapsulant comprises a plurality of dyads, wherein the first layer
comprises at least one sub-layer.
14. The thin film device of claim 1, further comprising a substrate
base, wherein the active device region and the thin film
encapsulant are disposed on the substrate base, wherein the active
device region and thin film encapsulant together form a device
stack, wherein a thickness of the device stack is 120 .mu.m or
less.
15. A thin film battery, comprising: an active device region, the
active device region comprising: a lithium-containing cathode; and
a solid state electrolyte, disposed on the cathode; an anode
disposed on the solid state electrolyte; and a thin film
encapsulant disposed adjacent to the anode and encapsulating at
least a portion of the lithium-containing cathode, the solid state
electrolyte, and the anode, the thin film encapsulant comprising: a
first layer, the first layer disposed immediately adjacent the
active device region and comprising a soft and pliable material;
and a second layer disposed on the first layer, the second layer
comprising a rigid dielectric material or rigid metal material.
16. The thin film battery of claim 15, wherein the thin film
encapsulant comprises a layer absorbent to laser radiation over a
wavelength range of 157 nm to 1064 nm.
17. The thin film battery of claim 15, the first layer comprising
at least one of: a getter/absorbent infused silicone, a 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.
18. The thin film battery of claim 15, the first layer and the
second layer together forming a first dyad, wherein the thin film
encapsulant comprises at least one additional dyad, the at least
one additional dyad being disposed on the first dyad.
19. The thin film battery of claim 18, wherein the first layer of
the first dyad comprises a first soft and pliable layer, the first
soft and pliable layer having a first layer thickness, wherein a
second dyad is disposed on the first dyad and includes a second
soft and pliable layer having a second layer thickness, wherein the
second layer thickness is less than the first layer thickness.
20. The thin film battery of claim 18, further comprising a
substrate base, wherein the lithium-containing cathode, the solid
state electrolyte, and the anode comprise an active device region,
wherein the active device region and the thin film encapsulant are
disposed on the substrate base, wherein the first layer comprises a
thickness of between 30 .mu.m and 50 .mu.m, wherein a thickness of
the second layer is 5 .mu.m or less, wherein the active device
region and thin film encapsulant together form a device stack, and
wherein a thickness of the device stack is between 50 .mu.m and 80
.mu.m.
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 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
may not be affected by thermal 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., thin film batteries (TFB) based upon lithium (Li),
Li is transported from one side to the other side of a battery as
electrons move around an external circuit connected to the TFB,
where the electrons move in an opposite direction to the chemical
and elements. One particular example of the volume change
experienced by a Li TFB is as follows. When charging a thin film
battery having a lithium-containing cathode such as 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 (given 100% dense
material), may be transported to the anode when loading is
approximately 1 mAhr/cm.sup.2. When Li returns to the cathode in a
discharge process, the same volume reduction may result on the
anode (assuming 100% efficiency). The cathode may also undergo a
volume change during a charging and discharging cycle, while such
changes are smaller as compared to the anode. For example, the
volume of a cathode formed from LiCoO.sub.2 material may expand
during charging when Li is extracted from the crystalline lattice,
while the volume change is relatively small (.about.2%) compared to
volume changes occurring at the anode.
[0005] As such, known thin film encapsulant approaches may be
lacking in providing the ability to accommodate such volume change
in a robust manner, where 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 device may include an active device
region, the active device region comprising a diffusant; and a thin
film encapsulant disposed adjacent to the active device region and
encapsulating at least a portion of the active device region. The
thin film encapsulant may include: a first layer, the first layer
disposed immediately adjacent the active device region and
comprising a soft and pliable material; and a second layer disposed
on the first layer, the second layer comprising a rigid dielectric
material or rigid metal material.
[0008] In another embodiment, a thin film battery may include an
active device region, where the active device region comprises: a
lithium-containing cathode; and a solid state electrolyte, disposed
on the cathode; an anode disposed on the solid state electrolyte.
The thin film battery may further include a thin film encapsulant
disposed adjacent to the anode and encapsulating at least a portion
of the lithium-containing cathode, the solid state electrolyte, and
the anode. The thin film encapsulant may include a first layer, the
first layer disposed immediately adjacent the active device region
and comprising a soft and pliable material; and a second layer
disposed on the first layer, the second layer comprising a rigid
dielectric material or rigid metal material.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1A illustrates a thin film device according to various
embodiments of the disclosure;
[0010] FIG. 1B provides one embodiment of a thin film encapsulant,
arranged as a dyad structure, according to embodiments of the
disclosure;
[0011] FIG. 2 illustrates a second instance of operation of the
thin film device of FIG. 1A, representing a second state of the
thin film device;
[0012] FIG. 3 illustrates a thin film battery in accordance with
embodiments of the disclosure;
[0013] FIG. 4 shows a thin film battery in accordance with other
embodiments of the disclosure in a first device state; and
[0014] FIG. 5 shows another depiction of the thin film battery of
FIG. 4 in a second device state.
DETAILED DESCRIPTION
[0015] 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.
[0016] The present embodiments are related to thin film encapsulant
structures and technology, where the thin film encapsulant is used
to minimize ambient exposure of active devices. In the present
embodiments, an active device may form an "active device region"
within a device including a thin film encapsulant. The present
embodiments provide novel structures and materials combinations for
thin film encapsulants, where the thin film encapsulants may be
used to encapsulate active devices.
[0017] In various embodiments, a device such as a thin film device,
is provided with a novel thin film encapsulant encapsulating an
active device. Examples of active devices include a piezoelectric
device, shape memory alloy device, or microelectromechanical system
(MEMS) device in some embodiments. In other embodiments, the film
device may be an electrochemical device. Examples of
electrochemical devices include electrochromic windows and thin
film batteries wherein the active component materials are highly
sensitive/reactive to moisture or other ambient materials. To this
end, in various embodiments known electrochemical devices such as
thin film batteries may be provided with encapsulation to protect
the active component materials.
[0018] 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 region. 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.
[0019] In various embodiments, a thin film device is provided with
a novel combination of thin film encapsulant material and/or
structures. The thin film device, such as a thin film battery or
electrochromic window, may include a device stack composed of
active layers, as well as the thin film encapsulant, which thin
film encapsulant may also constitute a multilayer structure.
[0020] According to embodiments of the disclosure, a thin film
device may include an active device region and a thin film
encapsulant. The active device region may include a source region
comprising the diffusant; and a selective expansion region, wherein
transport of the diffusant takes place reversibly between the
source region and the selective expansion region.
[0021] In embodiments where the thin film device is a Li thin film
battery, a cathode may act as the source region and may include a
cathode such as LiCoO.sub.2 or similar material. In the case of
electrochromic windows, the concomitant change in volume of a given
electrode region may be smaller than in thin film batteries. 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.
[0022] 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.
[0023] 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, as well as contraction
in the selective expansion region, rendering a more robust thin
film device.
[0024] In various embodiments of the disclosure, a novel thin film
encapsulant is arranged adjacent a selective expansion region of a
thin film device, such as an anode, where the thin film encapsulant
includes a stack of layers. In particular embodiments, the thin
film encapsulant includes a first layer, where the first layer is
disposed immediately adjacent the selective expansion region and is
formed from a soft and pliable material capable of accommodating a
change in physical volume in the selective expansion region. The
thin film encapsulant may further include a second layer adjacent
the first layer, where the second layer is a rigid metal layer or
rigid dielectric layer, and where the rigid dielectric layer or
rigid metal layer is less pliable than the first 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.
[0025] According to various embodiments, the thin film encapsulant
of a thin film encapsulant may encapsulate at least portions of the
source region and the 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 in order 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, the anode may change in thickness by several
micrometers as a result of lithium migration, 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 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.
[0026] In particular embodiments, and as detailed below, a largest
fraction of the reversible contraction and expansion of the thin
film encapsulant may take place in a first layer of the thin film
encapsulant. In particular, the first layer may be a soft and
pliable layer, and second layer of the thin film encapsulant may be
a permeation blocking layer. The second layer may be a rigid metal
layer or rigid dielectric layer, acting as a diffusion barrier such
as a moisture barrier or gas barrier, or a barrier to diffusion of
other species.
[0027] 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 base, referred to as the 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 or an electrochromic window. The source
region 104 may act as a source of a diffusant such as lithium,
where the diffusant may reversibly diffuse between the source
region 104 and to the selective expansion region 108. 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 first device state, such as a discharged state,
where the battery is not charged, meaning a diffusant 114, such as
lithium, is depleted from the anode.
[0028] The thin film device 100 further includes a thin film
encapsulant 110, where the thin film encapsulant 110 may include a
plurality of layers as suggested in FIG. 1A. The thin film
encapsulant 110 is disposed immediately adjacent the selective
expansion region 108. 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 t.sub.1. As shown in FIG. 1B, the thin film
encapsulant 110 may include a first layer 122, where the first
layer 122 is disposed immediately adjacent the selective expansion
region 108, and where the first layer 122 comprises a soft and
pliable material. In various embodiments, the first layer 122 may
be a polymer layer, where the polymer layer is a soft and pliable
layer, enabling the polymer layer to reversibly expand and
contract. In various embodiments, the term "polymer layer" as
referred to herein, may constitute a polymer layer stack where the
polymer layer stack includes at least one polymer layer, and may
include multiple layers, which layers may be referred to as
sub-layers. Accordingly, the first layer 122 may constitute a
polymer layer stack including multiple sub-layers of different
polymers, where at least one sub-layer is soft and pliable.
[0029] In various embodiments, the first layer 122 may be a
getter/absorbent infused polymer, a porous low dielectric constant
material, a silver paste, an epoxy, a printed circuit board
material, or a photo-resist material, and a combination 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.
[0030] In various embodiments a second layer 124 of the thin film
encapsulant 110 may be disposed on the first layer 122. The first
layer 122 and the second layer 124 may together form a first dyad,
shown as dyad 120. In various embodiments, the dyad 120 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
gas species, preventing moisture and gas diffusion through the thin
film encapsulant 110. The dyad 120 may also include at least one
layer having the properties of being a soft and pliable layer,
accommodating changes in dimension of an active device region in a
reversible manner. Examples of dyad 120 include a combination of a
polymer layer for first layer 122, and a rigid moisture barrier
layer such as a rigid dielectric layer or a rigid metal layer for
second layer 124, or combinations of rigid metal layer and rigid
dielectric layer. A rigid metal layer may include a rigid metal
material such as Cu, Al, Pt, Au, or other metal. The embodiments
are not limited in this context. In some embodiments, the thin film
encapsulant 110 may contain at least one additional dyad, also
shown as dyads 120, where the at least one additional dyad is
disposed on the first dyad. In the example of FIG. 1B, four dyads
are shown, while the embodiments are not limited in this context.
In particular, in other embodiments a thin film encapsulant may
include fewer or greater number of dyads. In some examples, a given
polymer layer of a dyad may include a plurality of polymer
sub-layers, where at least one polymer sub-layer is soft and
pliable. Examples of soft and pliable polymer materials 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).
[0031] 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 layer or
rigid dielectric layer 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.
[0032] Turning now to FIG. 2, 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. 2, the thin film device 100 may represent a thin film
battery in a charged state. In such a charged state the battery is
charged by outdiffusing the diffusant 114, such as lithium, from
the source region 104, and transporting the diffusant 114 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, where the expansion may
result in 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 a second thickness t.sub.2 as shown in the
charged state of FIG. 2. This reduction in thickness at the thin
film encapsulant 110 may be the result of the change in thickness
of the anode from a third thickness t.sub.3 in the contracted
configuration of FIG. 1A to a fourth thickness t.sub.4 in the
expanded configuration of FIG. 2. In particular, the growth in
thickness of the selective expansion region 108 may displace the
thin film encapsulant 110, at least in a region 115, where the
region 115 is adjacent the selective expansion region 108.
Accordingly, the thin film encapsulant 110 may accommodate the
expansion of the selective expansion region 108, by contracting
from the thickness t.sub.1 to t.sub.2 as shown in the charged
state, representing a second device state, as shown in FIG. 2.
[0033] Configurations where a polymer "layer" or more accurately a
polymer layer stack includes 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 second layer 124, for example.
[0034] In various embodiments, the first layer 122, meaning the
layer immediately adjacent the selective expansion region 108, may
be designed to accommodate the entire expansion and contraction or
the largest fraction of the expansion or contraction occurring in
selective expansion region 108. As detailed below, this
accommodation may be accomplished by choice of material or
materials for the first layer 122, as well as the detailed
architecture of the thin film encapsulant 110.
[0035] In some embodiments, while individual thicknesses (t.sub.1,
t.sub.2, t.sub.3 and t.sub.4) may change during cycling, 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. This accommodation may
take place in the following manner. In particular embodiments,
during cycling where t.sub.1 and t.sub.2 may represent opposite
extremes of thickness, the thickness and pliability of the first
layer 122 (or group of layers when first layer 122 is a layer
stack) of thin film encapsulant 110 may be result in the following
relationship. In particular, 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 any diffusion barrier layer of the thin film
encapsulant 110 is minimized. In some embodiments, the first layer
122 may constitute just one polymer layer accommodating the change
in dimension of the selective expansion region 108. In other
embodiments, the first layer 122 may constitute multiple polymer
sub-layers, where at least one polymer sub-layer, and not
necessarily other polymer sub-layers, is soft and pliable. Again,
this property of the polymer sub-layer may lead to the thickness
sum of t.sub.2+t.sub.4 being not substantially different from the
thickness sum of t.sub.1+t.sub.3, such as a difference of less than
10%. In various embodiments, the thin film encapsulant may have an
elongation property of at least 5%.
[0036] Turning now to FIG. 3 there is shown a thin film battery 300
in accordance with embodiments of the disclosure. The thin film
battery 300 may include a substrate base 302, a cathode current
collector 304, a cathode 306, a solid state electrolyte 308, an
anode 310, and a thin film encapsulant 312, as shown. In various
embodiments, the thin film encapsulant 312 may include a plurality
of different layers, such as at least one dyad as generally
described above. In particular, the thin film encapsulant 312 may
include a layer 314, where the layer 314 is directly disposed on
the anode 310. The layer 314 may be formed from a soft and pliable
material, as discussed above. In particular, the layer 314 may be a
polymer layer, and may include a plurality of polymer-sub-layers in
some variants, where the polymer layer, or at least one polymer
sub-layer is soft and pliable, as described above. In this manner,
the layer 314 may accommodate changes in volume of the anode 310 as
the anode 310 increases in thickness or decreases in thickness when
the thin film battery 300 charges or discharges. In some
embodiments, the thickness of the layer 314 (along the X-axis of
the Cartesian coordinate system shown) may be between 10 .mu.m and
50 .mu.m. The embodiments are not limited in this context.
[0037] The thin film encapsulant 312 may further include a layer
316, where the layer 316 is disposed on the layer 314 and is not in
direct contact with the anode 310. The layer 316 may be a rigid
metal layer as described above, or a rigid dielectric layer
composed of a known material such as silicon nitride, where the
pliability of the rigid dielectric layer is much less than the
pliability of layer 314. According to various embodiments, a rigid
dielectric layer may have 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 at least one polymer layer of
the layer 314. Similarly, known metals having a Vicker's hardness
as well as Young's modulus in excess of the values for polymer
materials shown above may be used as layer 316.
[0038] The layer 316 may serve as a diffusion barrier layer, to
prevent diffusion of ambient species such as H.sub.2O (moisture)
from outside the thin film battery 300 from penetrating to active
device regions of the thin film battery 300, including the anode
310, solid state electrolyte 308, and cathode 306, for example. In
some embodiments, the layer 316 may have a thickness of 0.25 .mu.m
to 1 .mu.m. The layer 316 may in some variants include a plurality
of rigid dielectric layers or rigid metal layers, or combinations
thereof. The embodiments are not limited in this context. The layer
314 and layer 316 may together constitute a dyad, where a dyad is
composed of a soft and pliable layer or layers, and a rigid
dielectric layer or rigid metal layer. As illustrated in FIG. 3,
the thin film encapsulant 312 may include a plurality of dyads. For
example, a layer 318 is disposed on the layer 316, where the layer
318 may be a soft and pliable layer, which layer may include a
plurality of polymer-sub-layers in some variants, while a layer 320
is disposed on the layer 318, where the layer 320 may be a rigid
dielectric or rigid metal layer or set of layers. Accordingly, the
layer 318 and layer 320 may be deemed to be a second dyad. This
sequence of alternating between a soft and pliable layer and a
rigid dielectric layer may be repeated, as represented, for example
by layer 322 and layer 324.
[0039] In various other embodiments, a thin film encapsulant may
include any number of layers, where a first layer immediately
adjacent the selective expansion region of a thin film battery or
other electrochemical device, is a soft and pliable layer or
includes at least one soft and pliable sub-layer. At the same time
a second layer disposed on the first layer is a rigid dielectric or
rigid metal layer or set of layers. These configurations provide
advantages over known thin film encapsulants using a rigid
dielectric immediately adjacent an anode region, for example.
Firstly, the thin film encapsulant 312 provides the diffusion
barrier properties imparted by a rigid dielectric or rigid metal
layer by virtue of incorporation of at least one rigid dielectric
or rigid metal layer in a dyad composed of a soft and pliable layer
in combination with a rigid dielectric layer or rigid metal layer.
Additionally, because the first layer adjacent the selective
expansion region is a soft and pliable layer (whether a polymer or
other soft and pliable layer), the volume expansion is more easily
accommodated during a charging cycle when diffusant moves into the
selective expansion region (anode region). The volume expansion is
especially more easily accommodated as compared to batteries
configured with known thin film encapsulants where a rigid
dielectric or rigid metal layer is adjacent the anode. In
particular, the first layer may elastically deform to accommodate
volume changes in an anode region, and may prevent cracks,
delamination, or other damage from occurring in the thin film
encapsulant, where such damage may otherwise occur in thin film
encapsulants where an inflexible, rigid dielectric is disposed
adjacent the anode. In this manner, a thin film encapsulant such as
thin film encapsulant 312 may remain intact after an anode is
charged to allow continued protection of the active device from
attacks by ambient oxidants, where such ambient oxides would
otherwise permeate through a breached thin film encapsulant.
[0040] Moreover, by providing a soft and pliable first layer
adjacent the anode region, during an opposite cycle of discharging
the soft and pliable first layer may expand back to release the
stress and to "fill a void" where the void would otherwise occur
when the diffusant (such as lithium) migrates back to a cathode. By
"filling the void" when the soft and pliable first layer expands
into the region being vacated by diffusant species returning to the
cathode, the electrical contacts in the anode may be enhanced. This
enhancement may provide longer term stability including electrical
and electrochemical performance, such as stable contact resistance
at the anode (selective expansion region) between the anode and
electrolyte.
[0041] In accordance with various embodiments, a thin film
encapsulant, such as the thin film encapsulant 312, may comprise
materials having the property of being laser-etchable, and in
particular may include a layer absorbent to laser radiation over a
target wavelength range provided a laser. 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.
[0042] This property facilitates maskless patterning of the thin
film encapsulant 312, where a laser is used to ablate portions of
the thin film encapsulant 312 in target regions. For example, the
thin film encapsulant 312 may include rigid dielectric or rigid
metal layers (such as layer 316, layer 320, and layer 324) formed
from silicon nitride or similar material, or a rigid metal layer,
such as Cu, (or Cu). In these materials strong electromagnetic
radiation absorption may take place in the wavelength range of 157
nm to 1064 nm to accommodate processing by known lasers generating
radiation in at least a portion of the aforementioned wavelength
range. Similarly, the layer 314, layer 318, and layer 322 may be
formed of a polymer, where the polymer also strongly absorbs
electromagnetic radiation over a similar wavelength range.
Accordingly, a thin film encapsulant may be patterned as shown in
FIG. 3, where the thin film encapsulant 312 conformally coats an
active device region 330 to form a thin film battery, while being
isolated from other structures by the region 340, formed by laser
etching of the layers of the thin film encapsulant 312. In
particular embodiments, the etchability of known polymer materials
used in the thin film encapsulant 312 may be enhanced as needed
where such polymer materials may have relatively lower absorption
of laser radiation. For example, a known polymer such as silicone
may have etchability enhanced by adding a dye to the polymer to
increase radiation absorption, or may be placed between two layers,
where the two layers are more highly etchable by a given laser.
[0043] Turning now to FIG. 4 there is shown a thin film battery 400
in accordance with other embodiments of the disclosure. The thin
film battery 400 may include a substrate base 302, a cathode
current collector 304, a cathode 306, a solid state electrolyte
308, and an anode 310, as described above with respect to FIG. 3.
The illustration in FIG. 4 may represent a discharged state of the
thin film battery 400. The thin film battery 400 also includes thin
film encapsulant 412, as shown. In various embodiments, the thin
film encapsulant 412 may include a plurality of different layers,
such as at least one dyad as generally described above with respect
to FIG. 3. In the architecture shown in FIG. 4, the thin film
encapsulant 412 includes a first layer, shown as layer 414. The
layer 414 is disposed immediately adjacent the anode 310 and is
made of a soft and pliable material, such as a polymer, or may
include multiple sub-layers, where at least one sub-layer of layer
414 is soft and pliable. In some embodiments of the thin film
encapsulant 412 illustrated in FIG. 4, the layer 414 may be
composed of a similar material as in layer 318 and layer 322.
[0044] According to some embodiments the layer thickness may vary
among different layers of a thin film encapsulant. A hallmark of
the thin film encapsulant 412 is the relative thickness of the
layer 414. In particular, the thickness of the layer 414 may be
designed to accommodate a large fraction, if not all, of the volume
change taking place in anode 310 when the thin film battery 400
charges and discharges. The thickness of the layer 414 may be
designed to be greater than the thickness of other layers in the
thin film encapsulant 412. For example, the thickness of layer 414
may be between 20 .mu.m and 50 .mu.m, while the thickness of the
rigid dielectric or rigid metal layers, layer 316, layer 320, and
layer 324 is 5 .mu.m or less. Moreover, the thickness of additional
soft and pliable layers of the thin film encapsulant 412, such as
layer 318 and layer 322, may be 20 .mu.m or less. The embodiments
are not limited in this context. Altogether, in some embodiments
the thickness of the device stack 420, including the active device
region 330 and thin film encapsulant 412 may be approximately 80 to
120 .mu.m, and in some embodiments may be 50 to 80 .mu.m. The
embodiments are not limited in this context.
[0045] Turning now to FIG. 5, there is shown another depiction of
the thin film battery 400, representing a charged state. As noted
previously, in Li thin film batteries where a cathode is a solid
state cathode formed from LiCoO.sub.2 having a thickness 15 .mu.m
to 17 .mu.m thick, the amount of lithium transported between
cathode and anode during charging may be the equivalent of a 6
.mu.m layer of Li. Accordingly, by arranging a first layer of a
thin film encapsulant 412 to be soft and pliable and to have
thickness in the range up to 50 .mu.m, such an increase in
thickness in the anode 310 may be more easily accommodated while
not causing cracking, delamination or other problems. At the same
time, the thickness of the additional layers of the thin film
encapsulant 412, including additional soft and pliable layers, may
be maintained at relatively lower values, because most or all of
the deformation in the anode 310 may be accommodated by the
reversible elastic deformation in the first layer. This
circumstance is illustrated in FIG. 5, where the layer 414 is
elastically compressed along the Z-axis (compare with FIG. 4),
while the other layers of the thin film encapsulant 412 are not
compressed or otherwise damaged, maintaining their original
dimensions with little or no stress. In particular embodiments,
during cycling where t.sub.1 and t.sub.2 may represent opposite
extremes of thickness for thin film encapsulant 412, the thickness
and pliability of the layer 414 of thin film encapsulant 412 may
result in the following. The thickness sum of t.sub.2+t.sub.4
(shown as t.sub.6 in FIG. 5) may be not substantially different
from the thickness sum of t.sub.1+t.sub.3, (shown as is in FIG. 4)
such as a difference of less than 10%.
[0046] In this manner, the thin film battery 400 may provide an
improved performance compared to known thin film batteries by
providing the following features. Firstly, multiple rigid
dielectric or rigid metal layers are provided to act as diffusion
barriers. Secondly, a layer, the "first layer," is provided
immediately adjacent to an anode to directly absorb the deformation
in the anode caused during charging and discharging of the battery,
all within a compact device structure (50 .mu.m-100 .mu.m). By
absorbing all or most of the deformation of a subjacent layer or
layers within an active device within the first layer of a thin
film encapsulant, the first layer may prevent the remaining layers
including diffusion barriers from deformation, or may greatly
reduce the deformation of such layers.
[0047] There are multiple advantages provided by the present
embodiments, including the ability to reduce the thickness of
non-active packaging materials such as thin film encapsulants used
in a thin film device, leading to enhanced energy density of these
devices. A further advantage lies in improving the robustness
ability of a thin film device encapsulant, where the thin film
device is patternable by a maskless process.
[0048] 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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