U.S. patent application number 15/338996 was filed with the patent office on 2017-10-19 for thin film battery device having recessed substrate and method of formation.
The applicant listed for this patent is Applied Materials, Inc.. Invention is credited to Byung-Sung Kwak, Michael Yu-Tak Young.
Application Number | 20170301956 15/338996 |
Document ID | / |
Family ID | 60038434 |
Filed Date | 2017-10-19 |
United States Patent
Application |
20170301956 |
Kind Code |
A1 |
Young; Michael Yu-Tak ; et
al. |
October 19, 2017 |
THIN FILM BATTERY DEVICE HAVING RECESSED SUBSTRATE AND METHOD OF
FORMATION
Abstract
A device. The device may include: a substrate, the substrate
comprising: an upper surface; and a recess extending from the upper
surface into the substrate; an active device region, the active
device region disposed within the recess and having a first
thickness; and an encapsulant, the encapsulant disposed over the
recess and over the active device region, wherein the encapsulant
has a second thickness, wherein the encapsulant extends above the
upper surface of the substrate to a first distance, and wherein the
first distance is less than a sum of the first thickness and second
thickness.
Inventors: |
Young; Michael Yu-Tak;
(Cupertino, CA) ; Kwak; Byung-Sung; (Portland,
OR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Applied Materials, Inc. |
Santa Clara |
CA |
US |
|
|
Family ID: |
60038434 |
Appl. No.: |
15/338996 |
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 10/052 20130101;
H01M 2/08 20130101; H01M 2/1094 20130101; C23C 14/50 20130101; H01M
10/0436 20130101; H01M 2300/0068 20130101; B23K 2103/172 20180801;
B23K 26/0006 20130101; H01M 6/18 20130101; H01J 37/3426 20130101;
H01M 10/0585 20130101; H01M 6/40 20130101; B23K 26/142 20151001;
H01M 6/188 20130101; H01M 2220/30 20130101; B29L 2031/3468
20130101; H01M 2/0207 20130101; H01M 2/026 20130101; H01M 2/0287
20130101; B29C 59/16 20130101; Y02T 10/70 20130101; B23K 2101/34
20180801; H01J 37/32715 20130101; H01M 2/0267 20130101; H01M
2300/0065 20130101; C23C 14/34 20130101; Y02E 60/10 20130101; H01M
4/382 20130101; H01M 4/525 20130101; B29K 2995/0006 20130101; H01M
6/005 20130101; B23K 26/362 20130101; B23K 2101/36 20180801; H01M
10/0525 20130101 |
International
Class: |
H01M 10/0585 20100101
H01M010/0585; H01M 2/08 20060101 H01M002/08; H01M 2/02 20060101
H01M002/02; H01M 10/04 20060101 H01M010/04; H01M 10/0525 20100101
H01M010/0525 |
Claims
1. A device, comprising: a substrate, the substrate comprising: an
upper surface; and a recess extending from the upper surface into
the substrate; an active device region, the active device region
disposed within the recess and having a first thickness; and an
encapsulant, the encapsulant disposed over the recess and over the
active device region, wherein the encapsulant has a second
thickness, wherein the encapsulant extends above the upper surface
of the substrate to a first distance, and wherein the first
distance is less than a sum of the first thickness and second
thickness.
2. The device of claim 1, wherein the recess extends to a first
depth from the upper surface into the substrate, wherein the first
depth is greater than or equal to the first thickness.
3. The device of claim 1, the active device region comprising a
plurality of layers.
4. The device of claim 3, wherein the device is a thin film
battery, the plurality of layers comprising: a cathode current
collector; a lithium-containing cathode; a solid state electrolyte
disposed on the lithium-containing cathode; and an anode region
disposed on the solid state electrolyte; and an anode current
collector disposed on the anode region, the anode current collector
being further disposed adjacent the encapsulant.
5. The device of claim 1, wherein the encapsulant comprises a
plurality of layers, wherein the plurality of layers comprises at
least one rigid layer and at least one polymer layer.
6. The device of claim 1, wherein a portion of the encapsulant is
disposed around the active device region within the recess.
7. The device of claim 1, further comprising a planarizing polymer
layer disposed between the encapsulant and the active device
region.
8. The device of claim 7, wherein the planarizing polymer layer
comprises a cured polymer.
9. The device of claim 7, wherein the planarizing polymer layer
comprises at least one of: an elongation till break of 70% or
greater and an elastic modulus of less than 20 GPa.
10. A thin film battery, comprising: a substrate, the substrate
comprising: an upper surface; and a recess extending from the upper
surface into the substrate along a first direction; an active
device region, the active device region being disposed within the
recess and having a first thickness, wherein the active device
region comprises: a lithium-containing cathode; a solid state
electrolyte disposed on the lithium-containing cathode; and an
anode region disposed on the solid state electrolyte; and an
encapsulant disposed on the active device region, wherein the
encapsulant comprises: at least one rigid layer; and at least one
polymer layer.
11. The thin film battery of claim 10, wherein the encapsulant has
a second thickness, wherein the encapsulant extends above the upper
surface of the substrate to a first distance, and wherein the first
distance is less than a sum of the first thickness and second
thickness.
12. The thin film battery of claim 10, wherein the recess comprises
a localized height variation along the first direction.
13. The thin film battery of claim 10, wherein the active device
region further comprises an anode current collector and a cathode
current collector, the anode current collector and the cathode
current collector extending onto the upper surface of the
substrate.
14. The thin film battery of claim 10 wherein the at least one
polymer layer is encapsulated within the encapsulant.
15. A method of forming a device, comprising: providing a substrate
having an upper surface; forming a recess within the substrate, the
recess extending from the upper surface into the substrate; forming
an active device region within the recess, the active device region
having a first thickness; and forming an encapsulant over the
active device region, wherein the encapsulant has a second
thickness, and wherein the encapsulant extends above the upper
surface of the substrate to a first distance, wherein the first
distance is less than a sum of the first thickness and second
thickness.
16. The method of claim 15, wherein the forming the active device
region comprises: depositing a cathode current collector;
depositing a lithium-containing cathode layer on the cathode
current collector; depositing a solid state electrolyte layer on
the lithium-containing cathode layer; depositing an anode layer of
the solid state electrolyte layer; depositing an anode current
collector; wherein the cathode current collector, the
lithium-containing cathode layer, solid state electrolyte, the
anode layer, and the anode current collector form an active device
stack; and patterning the active device stack to define a patterned
stack disposed within the recess.
17. The method of claim 15, wherein the forming the encapsulant
comprises: depositing a polymer layer; and depositing a rigid
layer, wherein the polymer layer and the rigid layer form a stack
of layers.
18. The method of claim 15 wherein the forming the recess
comprises: forming a substrate precursor in a green state; molding
the substrate precursor to form a recessed structure having an
initial size in the substrate precursor; and heating the substrate
precursor to form the recess in the substrate, wherein the recess
has a final size different from the initial size.
19. The method of claim 15 wherein the forming the recess
comprises: providing the substrate as a planar substrate; and
etching the substrate to form the recess using laser
micromachining, or using lithographic patterning and etching.
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 thin film battery devices.
BACKGROUND
[0003] Thin film batteries may enable an increasing number of
applications because of their compact size. As an example, a
medical battery cell is a thin film-based micro battery device
built from a battery cell stack deposited on a substrate, where the
thickness of the active battery components may be on the order of
45 micrometers. Additionally, an encapsulation having a thickness
on the order of 40 micrometers to 100 micrometers, such as 45
micrometers, may be deposited over the active battery components.
The different active battery components and encapsulant may be
deposited as a series of thin layers (thin films) and patterned to
form a targeted device structure. Providing adequate step-coverage
of such a structure presents challenges, such as avoiding
step-coverage-related layer breakage. Step-coverage breakage of a
metallization layer carrying active electrical current may result
in catastrophic failure of functionality in such a device.
Step-coverage breakage of a dielectric or a metal layer functioning
as a gas and moisture permeation barrier may result in gas and
moisture permeation from the cell ambient to the cell interior,
leading to poor cell cycle life. Furthermore, the cell structure
step-ledges are very vulnerable to degradation induced by cell
volume expansion of the thin film battery structure during cell
cycling operations of a thin film battery.
[0004] With respect to these and other considerations the present
disclosure is provided.
BRIEF SUMMARY
[0005] In one embodiment, a device may include a substrate, the
substrate comprising: an upper surface; and a recess extending from
the upper surface into the substrate; an active device region, the
active device region disposed within the recess and having a first
thickness. The device may include an encapsulant, the encapsulant
disposed over the recess and over the active device region, wherein
the encapsulant has a second thickness. The encapsulant may extend
above the upper surface of the substrate to a first distance, and
wherein the first distance is less than a sum of the first
thickness and second thickness.
[0006] In another embodiment, a thin film battery may include a
substrate, the substrate comprising: an upper surface; and a recess
extending from the upper surface into the substrate along a first
direction. The battery may include an active device region, the
active device region being disposed within the recess and having a
first thickness. The active device region may include a
lithium-containing cathode; a solid state electrolyte disposed on
the lithium-containing cathode; and an anode region disposed on the
solid state electrode; and an encapsulant disposed on the active
device region. The encapsulant may include at least one rigid layer
and at least one polymer layer.
[0007] In another embodiment, a method of forming a device, may
include: providing a substrate having an upper surface; forming a
recess within the substrate, the recess extending from the upper
surface into the substrate; forming an active device region within
the recess, the active device region having a first thickness; and
forming an encapsulant over the active device region, wherein the
encapsulant has a second thickness, and wherein the encapsulant
extends above the upper surface of the substrate to a first
distance, wherein the first distance is less than a sum of the
first thickness and second thickness.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1A shows a device arranged according to embodiments of
the disclosure;
[0009] FIG. 1B shows a device arranged according to other
embodiments of the disclosure;
[0010] FIG. 2A shows another device according to further
embodiments of the disclosure;
[0011] FIG. 2B shows an exemplary active device region according to
various embodiments of the disclosure;
[0012] FIG. 2C shows another device according to further
embodiments of the disclosure;
[0013] FIG. 3 illustrates a particular embodiment of a thin film
battery;
[0014] FIG. 4 presents an exemplary process flow according to
embodiments of the disclosure;
[0015] FIG. 5 presents another exemplary process flow according to
other embodiments of the disclosure; and
[0016] FIG. 6 presents a further exemplary process flow according
to embodiments of the disclosure.
[0017] The drawings are not necessarily to scale. The drawings are
merely representations, not intended to portray specific parameters
of the disclosure. The drawings are intended to depict exemplary
embodiments of the disclosure, and therefore are not be considered
as limiting in scope. In the drawings, like numbering represents
like elements.
[0018] Furthermore, certain elements in some of the figures may be
omitted, or illustrated not-to-scale, for illustrative clarity. The
cross-sectional views may be in the form of "slices", or
"near-sighted" cross-sectional views, omitting certain background
lines otherwise visible in a "true" cross-sectional view, for
illustrative clarity. Furthermore, for clarity, some reference
numbers may be omitted in certain drawings.
DETAILED DESCRIPTION
[0019] 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.
[0020] The present embodiments are related to device structures,
such as thin film battery structures and fabrication methods, where
exemplary device structures provide an improved topography as
compared to known device structures. To this end, various
embodiments provide a recessed cell stack structure for a thin film
battery, where at least a portion of a cell stack forming the thin
film battery components is recessed into the host substrate. In
this manner, a battery cell's surrounding edges may be protected by
the walls of a recess provided in the substrate.
[0021] FIG. 1A depicts a device 100 according to various
embodiments of the disclosure. The device 100 may represent a thin
film device, such as a thin film battery in some embodiments. In
other embodiments, the device 100 may represent a non-thin film
device, such as a larger battery. As shown in FIG. 1A, the device
100 includes a substrate 102 having an upper surface 112. The
substrate 102 may also include a recess 104 extending from the
upper surface 112 into the substrate 102 for a distance d.sub.1.
Additionally, the device may include an active device region 106,
where the active device region 106 is disposed within the recess
104. The active device region 106 may include a plurality of
components forming part of an active device, such as a plurality of
structures forming the active part of a battery.
[0022] In embodiments where device 100 represents a thin film
battery, the active device region 106 may comprise a cell stack
formed from a plurality of layers, where the different layers
function as different parts of the battery. Examples of such layers
include a cathode current collector, a lithium-containing cathode,
a solid state electrolyte, where the solid state electrolyte may be
disposed on the lithium-containing cathode, an anode region
disposed on the solid state electrolyte, an anode (e.g., Li metal)
and a current collector, and so forth. While such layers may be
initially deposited in blanket form, the layers may be subsequently
patterned to form the active device region 106 as a cell stack,
where the active device region 106 is located within the recess 104
as shown.
[0023] The active device region 106 as shown may have a first
thickness represented by t.sub.1. In various embodiments, the
relative size of d.sub.1 and t.sub.1 may be arranged to accommodate
the active device region 106 partially or completely within the
recess 104. As shown in the example of FIG. 1A, d.sub.1 may be
greater than t.sub.1, resulting in the active device region 106
being completely contained within the recess 104, meaning the top
of active device region 106 is below the upper surface 112. As an
example, in the case of a thin film battery t.sub.1 may be 45
.mu.m, while d.sub.1 is 50 .mu.m. The embodiments are not limited
in this context.
[0024] As further shown in FIG. 1A, the device 100 may include an
encapsulant 108, where the encapsulant 108 is disposed on or over
the active device region 106, and where the encapsulant 108 may
also be disposed over the upper surface 112 as shown. In some
embodiments, the encapsulant 108 may be formed using known
encapsulant materials for encapsulating thin film batteries. The
encapsulant 108 may have a second thickness shown as t.sub.2 in
FIG. 1A. As an example, in the case of a thin film battery, the
encapsulant 108 may have a thickness in the range of 40 .mu.m to
100 .mu.m and in particular embodiments a thickness of 45 .mu.m.
The embodiments are not limited in this context.
[0025] In the example geometry of FIG. 1A, the encapsulant 108 may
have a planar structure wherein the encapsulant 108 extends above
the upper surface 112 to a first distance, represented by h.sub.1.
Because of the planar structure of encapsulant 108, the first
distance may be equivalent to the thickness, t.sub.2, of the
encapsulant 108. An advantage provided by the structure of device
100 is the lesser topography generated by the combination of the
active device region 106 and encapsulant 108, as compared to known
thin film batteries. In particular, because in the present
embodiment the active device region 106 is formed on the bottom of
the recess 104, and not on the upper surface 112, the active device
region 106 and encapsulant 108 together generate a profile
extending just to h.sub.1, above the upper surface 112.
Additionally, there is no offset or curvature in the profile of the
encapsulant 108 in the region 122, as compared to the profile
120.
[0026] In other embodiments, convenience or other considerations
may dictate the depth of a recess being less than t.sub.1. Turning
now to FIG. 1B there is shown another embodiment of a device,
device 150 where the device 150 is similar to device 100. In this
case the device 150 includes a recess 154 where the depth of the
recess 154 is represented by d.sub.2. In this case, d.sub.2 is less
than t.sub.1, generating an encapsulant 108 having a profile 120,
extending to a height h.sub.2 above the upper surface 112 in the
region above the recess 154, as shown in FIG. 1B. Depending upon
the extent of height h.sub.2 of the resulting encapsulant 108 after
deposition, this structure may also provide an advantage over known
thin film devices, where an active device region 106 may be formed
on the upper surface 112, resulting in the encapsulant projecting
to a greater extent above the upper surface 112.
[0027] In either circumstance of FIG. 1A or FIG. 1B, the device 100
or device 150 may be arranged wherein the encapsulant 108 extends
above the upper surface of the substrate to a first distance
(h.sub.1), wherein h.sub.1 is less than a sum of the first
thickness (t.sub.1) of the active device region 106 and second
thickness (t.sub.2) of the encapsulant. The advantages afforded by
these configurations may be further illustrated using "realistic"
values for the various entities of a thin film battery as embodied
by device 100. As an example where the thickness of the active
device region of a thin film battery, t.sub.1, is 45 .mu.m, d.sub.1
is 50 .mu.m, and the encapsulant thickness, t.sub.2, is 45 .mu.m,
the structure of FIG. 1A may yield a value of h.sub.1 of 45 .mu.m.
This value for h.sub.1 of 45 .mu.m means the thickness of the
active device region 106 does not contribute to the value of
h.sub.1 since the thickness of the encapsulant t.sub.2, is just 45
.mu.m. Accordingly, a device stack including the active device
region 106 and encapsulant 108, having a total thickness of 90
.mu.m, is accommodated in the device 100 in a manner where the
device stack extends just 45 .mu.m above the upper surface 112 of
substrate 102. Notably, a similar device stack having a total
thickness of 90 .mu.m and constructed where the active device
region is formed on the upper surface 112, would extend 90 .mu.m
above the upper surface 112 (see h.sub.2). Accordingly, in this
example, the topography generated by a thin film battery above the
upper surface of a substrate is reduced by 50% in comparison to a
known device structure. This structure provides a further advantage
of reducing the Z-axis height variation so as to accommodate better
Z-axis lithographic pattern lens focusing capability for patterning
to be performed using optical lithography, as an example.
[0028] As further illustrated in FIG. 1A, the recess 104 may be
larger than the active device region 106, including within the X-Y
plane of the Cartesian coordinate system shown. In various
embodiments as discussed further below, material may be provided
within a region 114 to encompass the active device region 106
within the recess 104, including the gap between the top of active
device region 106 and the bottom of encapsulant 108. In some
embodiments, this material may be provided in addition to the
encapsulant 108.
[0029] Turning now to FIG. 2A, there is shown a device 200
according to further embodiments of the disclosure. In this
embodiment, the device 200 may represent a thin film battery, where
the active device region 106 includes a plurality of layers. FIG.
2B depicts a variant of the active device region including a
cathode current collector 212, a lithium-containing cathode 214, a
solid state electrolyte 216, an anode region 218 and an anode
current collector 220. Again, the active device region 106 is
disposed in a recess 104 as detailed above with respect to FIG. 1.
The substrate 102 may be formed of a material such as yttria
stabilized zirconium oxide (YSZ), alumina, a ceramic, or other
known material for forming a thin film battery. The embodiments are
not limited in this context.
[0030] The device 200 may also include an encapsulant 202, where
the encapsulant 202 includes a plurality of layers. The encapsulant
202 may be a thin film encapsulant where a total thickness (along
the Z-axis) of the encapsulant 202 is on the order of tens of
micrometers, such as 10 .mu.m to 100 .mu.m. The embodiments are not
limited in this context. As an example, the encapsulant may include
a layer 204 composed of a first material and a layer 206 composed
of a second material. The first material and second material may
perform different functions in some embodiments. For example, layer
204 may be a polymer layer, and in some embodiments may be a soft
and pliable polymer, providing flexibility to the encapsulant 202.
In various embodiments, when the layer 204 is a polymer layer, this
layer may be composed of multiple polymer sub-layers, where the
properties of the different polymer sub-layers may vary among one
another. For example, one polymer sub-layer of the polymer layer
may be especially flexible as compared to other polymer
sub-layers.
[0031] Layer 206 may be a rigid layer, such as rigid dielectric,
rigid metal, such as Cu, Al, Pt, Au, or other metal, or rigid
polymer, used as a permeation blocking layer to prevent diffusion
of species through the encapsulant, such as contaminant species
present in ambient surrounding the device 200. The layer 204 and
layer 206 may be arranged in repeating fashion as shown. In
particular embodiments, the layer 204 may be a polymer layer and
layer 206 may be a rigid dielectric layer, such as silicon nitride.
According to different embodiments, the sequence of layer 204 and
layer 206 may repeat two or more times. The embodiments are not
limited in this context. In various embodiments, in the encapsulant
202, the layers 204, which layers may be a polymer layer, may be
encapsulated within the encapsulant 202, such as shown
schematically in FIG. 2A. As such, the layer 206, as well as
subsequent layers, may encapsulate a given polymer layer to create
a permeation blocking layer, including around edges of a polymer
layer.
[0032] 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.
[0033] As further shown in FIG. 2A, the device 200 may include a
first electrical contact 208 and a second electrical contact 210,
where these contacts are used to connect to a cathode and anode,
respectively, of a thin film battery. As in the embodiment of FIG.
1A, because the active device region 106 is disposed within the
recess 104, the active device region 106 and encapsulant 202
present a reduced topography as compared to known thin film battery
structures.
[0034] Additionally, because the various layers of the encapsulant
202 are not disposed on an active device structure extending above
the upper surface 112, the various layers, including layer 204 and
layer 206, may be formed on a flat surface and may extend in a
planar fashion as shown in the X-Y plane, while not bending. For
example, referring also again to FIG. 1B, there are shown partial
contours of a layer 124 and a layer 126 generated under the
scenario of profile 120, assuming the encapsulant 108 is formed
from multiple layers. In the example of FIG. 1B, the layer 124 and
layer 126 may bend in the region 122. In the extreme case of known
thin film devices where the encapsulant is formed on top of an
active device stack extending from the upper surface 112, the
profile of an encapsulant may be even sharper in the region 122,
resulting is severe bending and strain or stress on the layers
formed in such an encapsulant. Notably, in FIG. 2A the layers of
encapsulant 202 do not bend since the top of encapsulant 202 is
planar. Accordingly, this planar structure places less stress on
the individual layers of the encapsulant 202, making failure less
likely and providing longer life to a battery cell.
[0035] FIG. 2C depicts a thin film battery 250 according to further
embodiments of the disclosure. In this example, the active device
region may include a cathode current collector 222, cathode 224,
solid state electrolyte 226, anode 228, and anode current collector
230. After formation of the recess 104, the cathode current
collector 222, cathode 224, solid state electrolyte 226, anode 228,
and anode current collector 230 may be formed by blanket deposition
and patterning. In this embodiment, the cathode current collector
222 and anode current collector 230 extend to opposite sides of
encapsulant 202, in a coplanar configuration with one another. This
arrangement may provide a structure more resistant to attack from
ambient species as compared to device 200. In various embodiments,
fill material may be provided in the region 232.
[0036] Turning now to FIG. 3 there is shown a structure of a thin
film battery 300 according to further embodiments of the
disclosure. The thin film battery 300 may include some of the
components of the device 200, where like components are labeled the
same. A hallmark of the thin film battery 300 is the provision of a
planarizing polymer layer 302, disposed between the encapsulant 202
and the active device region 106. In some embodiments the
planarizing polymer layer 302 may be composed of a cured polymer.
Examples of a cured polymer include a silicone, an epoxy, or a
polyimide. In some embodiments, the planarizing polymer layer 302
may be dispensed as a liquid or relatively lower viscosity material
into the recess 104 after formation of the active device region 106
in the recess 104. The planarizing polymer layer 302 may be
subsequently cured to form a solid layer. The planarizing polymer
layer 302 may further extend over the upper surface 112. After
formation, the planarizing polymer layer 302 may present a planar
surface for depositing of the encapsulant 202. As shown, the
planarizing polymer layer 302 may be encapsulated by a layer 206,
such as a rigid metal layer or rigid dielectric layer, acting as a
permeation blocking layer. The thickness of the planarizing polymer
layer 302 above the upper surface 112 may range from 5 .mu.m to 60
.mu.m in some embodiments. While not specifically shown, a
planarizing polymer layer may optionally be included in the
embodiment of FIG. 1, for example. In a variant of the thin film
battery 300, cathode current collector and anode current collector
contacts may be formed to the sides of encapsulant 202, so as to
extend over the upper surface 112, as shown in FIG. 2C, for
example.
[0037] According to various embodiments, the planarizing polymer
layer 302 (as well as the layer 204) may be a soft and pliable
material, and may have either a high elongation to break or a low
elastic modulus, or the two properties. Examples of useful polymer
properties for planarizing polymer layer 302 include a high
elongation to break, defined herein as an elongation to break of
70% or greater. Other exemplary properties of a planarizing polymer
layer 302 include a relatively lower modulus than a rigid layer,
where a low elastic (Young's) modulus as used herein is an elastic
modulus less than 20 GPa (e.g., 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 2500 Kpsi or .about.17.2 GPa). A rigid
dielectric layer may be composed of a known material such as
silicon nitride (silicon nitride: Vicker's hardness of .about.13
GPa, Young's Modulus of .about.43500 Kpsi or .about.300 GPa), where
the hardness and elastic modulus are greater than the polymer
layer.
[0038] In this manner, the planarizing polymer layer 302 may
provide a cushion to absorb the effect of changes in volume in the
active device region 106 during operation of the thin film battery
300. For example, during charging and discharging of a
lithium-based thin film battery, the anode region (as well as
cathode) may undergo a reversible expansion and contraction as
lithium diffuses into and out of the anode region (cathode). This
reversible dilation may represent a change in dimension on the
order of 5 .mu.m or more along the Z-axis for active device regions
having dimensions on the order of 50 .mu.m along the Z-axis. The
provision of the planarizing polymer layer 302 may accommodate this
dilation in the active device region 106 by allowing elastic
deformation of the planarizing polymer layer to compensate for the
dilation. In this manner, less stress or strain may be imparted to
other regions of the thin film battery 300, such as in rigid
dielectric layers of the encapsulant 202. In turn, this lower
stress or strain may result in less cracking or delamination of the
encapsulant or of layers within the active device region 106,
especially at the perimeter of an active region of the thin film
battery 300. The reliability of interconnect structures such as
first electrical contact 208 and second electrical contact 210 may
also be improved for the same reasons. Accordingly, in addition to
providing a lesser topography above the upper surface 112, the thin
film battery of 300 may provide improved protection against gas and
moisture permeation, and thus better device performance as well as
improved device lifetime
[0039] Turning now to FIG. 4 there is shown a process flow 400
according to some embodiments of the disclosure. At block 402, a
substrate is provided having an upper surface. The substrate may be
a planar substrate such as a polycrystalline ceramic, oxide,
monocrystalline material, semiconductor, or polymer in different
embodiments.
[0040] At block 404, a recess is formed in the substrate, where the
recess extends from the upper surface of the substrate into the
substrate. The recess may be formed to a target depth designed to
accommodate device structures to be formed. In various embodiments,
the recess, including in the active device area, may exhibit a
localized height variation (along the Z-axis), where this height
variation may increase the effective battery cell area, resulting
in increased cell capacity.
[0041] At block 406, an active device region having a first
thickness is formed in the active area recess. In particular
embodiments, the active device region may include a plurality of
layers, such as a cell stack composed of layers for forming a thin
film battery. The first thickness of the active device region may
be chosen so as to place the active device region entirely within
the recess, or partially within the recess in different
embodiments. In some examples, the active device region may be
formed by depositing a plurality of layers in blanket form on the
substrate so as to form a stack of layers. The stack of layers may
be subsequently patterned and etched so as to remove material of
the stack of layers not located in the recess. In some embodiments,
the r stack of layers may be formed and patterned in a manner where
a cathode current collector and anode current collector extend out
of the active area recess, and onto the upper surface of the
substrate.
[0042] In one particular example, forming the active device region
may involve operations including depositing a cathode current
collector; depositing a lithium-containing cathode layer on the
cathode current collector; depositing a solid state electrolyte
layer on the lithium-containing cathode layer; depositing an anode
layer of the solid state electrolyte layer; depositing an anode
current collector; wherein the cathode current collector, the
lithium-containing cathode layer, solid state electrolyte, the
anode layer, and the anode current collector form an active device
stack; and patterning the active device stack to define a patterned
stack disposed within the recess.
[0043] At block 408, a planarization layer is formed over the
active device region and the recess. The planarization layer may be
a planarizing polymer layer in some embodiments. In some
embodiments, the planarization layer may be formed by dispensing a
relatively low viscosity, liquid like material, onto the substrate,
where the low viscosity material fills the recess around the active
device region. The planarization layer may further extend over the
upper surface of the substrate in some embodiments. When dispensed
as a liquid, the planarization layer may be subsequently cured to
form a solid, such as in the case of silicones, epoxies, and other
curable polymers.
[0044] At block 410, an encapsulant is formed over the
planarization layer and the active device region. The encapsulant
may extend over at least a portion of the upper surface of the
substrate in various embodiments. In some embodiments, the
encapsulant may include a plurality of layers, where different
layers are formed from different materials. In some embodiments,
the encapsulant may include a rigid layer, such as a rigid metal or
rigid dielectric, where the rigid layer encapsulates the
planarization layer at the upper surface of the substrate. The
encapsulant may be formed, for example, by depositing a plurality
of different layers in blanket form to generate a thin film
encapsulant arranged as a stack of layers having a target thickness
for the encapsulant. In some embodiments, the thin film encapsulant
may be subsequently patterned to define an encapsulant structure
extending over the recess and the active device region, and
extending partially over the upper surface of substrate. The
encapsulant and portions of the underlying active device region may
be further patterned to provide for contact structures to the
active device region. In some embodiments, where the anode current
collector and cathode current collector extend along the upper
surface of the substrate, patterning may be performed so as to
exposed the anode current collector and cathode current collector
for external contacts (as in FIG. 2C).
[0045] Turning now to FIG. 5 there is shown another process flow
500 according to embodiments of the disclosure. At block 502, a
substrate precursor is provided in a green state. A green state may
refer to a state of a substrate where the substrate microstructure
is not in final form, and may include material to be subsequently
removed or transformed by application of heat. An example of a
ceramic substrate precursor in a green state may be a composite
including ceramic powder mixed with a combination of other material
such as a liquid and a polymer. In the green state the ceramic
substrate precursor may have semi-solid properties, rendering the
substrate amendable to shaping and molding.
[0046] At block 504, the operation of molding the substrate
precursor in the green state is performed using a mold, where the
mold may have a designed shape and size to form a recessed
structure having an initial size within the ceramic precursor. In
various embodiments, the mold may be a mold stamp, a textured mold
roller, a Gravure roller with laser defined relief patterns or a
printing blanket with defined relief patterns, and so forth. The
recessed structure may have, for example, a dimension in one or
more directions larger than the target size for a final recess,
such as approximately 20% larger in one example.
[0047] At block 506, the substrate precursor, including the
recessed structure, is heated to form a final substrate, wherein a
recess is formed in the final substrate, wherein the recess has a
final size different than the initial size of the recessed
structure formed in the substrate precursor.
[0048] Turning now to FIG. 6 there is shown another process flow
600 according to other embodiments of the disclosure. At block 602,
a planar substrate is provided where the planar substrate has an
upper surface. At block 604, the substrate is etched to form a
recess. The substrate may be etched using laser micromachining or
lithographic patterning and etching to a target depth and according
to a target size and shape. The size and shape of the recess as
well as the depth of the recess may be arranged to accommodate an
active device region of an active device to be formed in the
recess. In various embodiments, the recess, including in the active
device area may exhibit localized height variation (along the
Z-axis), where this height variation may increase the effective
battery cell area, resulting in increased cell capacity.
[0049] While the aforementioned embodiments focus on applications
for thin film batteries, in other embodiments, a battery structure
designed for larger batteries may be formed using a substrate
recess according to the principles of the aforementioned
embodiments.
[0050] There are multiple advantages provided by the present
embodiments, including the ability to reduce the distance a device
stack extends above a substrate upper surface, including the active
device region and encapsulant, while not having to reduce the
thickness of either the active device region or encapsulant.
Further advantages include the ability to reduce stress, cracking,
and delamination in a thin film device while not changing
properties or dimensions of individual components of the thin film
device. Another advantage is the overall reduction of device height
above a substrate, afforded by forming a portion of the thin film
device within a recess in a substrate.
[0051] 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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