U.S. patent application number 14/054217 was filed with the patent office on 2014-02-06 for glass interposer panels and methods for making the same.
This patent application is currently assigned to CORNING INCORPORATED. The applicant listed for this patent is CORNING INCORPORATED. Invention is credited to Ivan A. Cornejo, Sinue Gomez, James Micheal Harris, Lisa Anne Moore, Sergio Tsuda.
Application Number | 20140034374 14/054217 |
Document ID | / |
Family ID | 44653533 |
Filed Date | 2014-02-06 |
United States Patent
Application |
20140034374 |
Kind Code |
A1 |
Cornejo; Ivan A. ; et
al. |
February 6, 2014 |
GLASS INTERPOSER PANELS AND METHODS FOR MAKING THE SAME
Abstract
Glass interposer panels and methods for forming the same are
described herein. The interposer panels include a glass substrate
core formed from an ion-exchangeable glass. A first layer of
compressive stress may extend from a first surface of the glass
substrate into the thickness T of the glass substrate core to a
first depth of layer D.sub.1. A second layer of compressive stress
may be spaced apart from the first layer of compressive stress and
extending from a second surface of the glass substrate core into
the thickness T of the glass substrate core to a second depth of
layer D.sub.2. A plurality of through-vias may extend through the
thickness T of the glass substrate core. Each through-via is
surrounded by an intermediate zone of compressive stress that
extends from the first layer of compressive stress to the second
layer of compressive stress adjacent to a sidewall of each
through-via.
Inventors: |
Cornejo; Ivan A.; (Corning,
NY) ; Gomez; Sinue; (Corning, NY) ; Harris;
James Micheal; (Elmira, NY) ; Moore; Lisa Anne;
(Corning, NY) ; Tsuda; Sergio; (Horseheads,
NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
CORNING INCORPORATED |
CORNING |
NY |
US |
|
|
Assignee: |
CORNING INCORPORATED
CORNING
NY
|
Family ID: |
44653533 |
Appl. No.: |
14/054217 |
Filed: |
October 15, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12868976 |
Aug 26, 2010 |
8584354 |
|
|
14054217 |
|
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Current U.S.
Class: |
174/264 |
Current CPC
Class: |
H01L 23/49827 20130101;
H05K 1/115 20130101; Y10T 29/49155 20150115; H05K 3/4038 20130101;
C03C 21/002 20130101; Y10T 29/49165 20150115; H05K 2201/09563
20130101; Y10T 29/49117 20150115; H05K 2201/10378 20130101; C03C
15/00 20130101; H05K 1/0306 20130101; H01L 23/15 20130101; H05K
2201/0769 20130101 |
Class at
Publication: |
174/264 |
International
Class: |
H05K 1/11 20060101
H05K001/11; H05K 1/03 20060101 H05K001/03 |
Claims
1. An interposer panel for an electronic assembly, the interposer
panel comprising: a glass substrate core formed from an
ion-exchangeable glass and comprising: a first surface, a second
surface opposite the first surface, and a thickness T; a first
layer of compressive stress extending from the first surface of the
glass substrate core into the thickness T of the glass substrate
core to a first depth of layer D.sub.1; a second layer of
compressive stress spaced apart from the first layer of compressive
stress and extending from the second surface of the glass substrate
core into the thickness T of the glass substrate core to a second
depth of layer D.sub.2; and a plurality of through-vias extending
through the thickness T of the glass substrate core, wherein each
through-via of the plurality of through-vias is surrounded by an
intermediate zone of compressive stress extending from the first
layer of compressive stress to the second layer of compressive
stress adjacent to a sidewall of each through-via.
2. The interposer panel of claim 1, wherein the glass substrate
core is an alkali aluminosilicate glass or an aluminoborosilicate
glass.
3. The interposer panel of claim 1, wherein: the first depth of
layer D.sub.1 is equal to the second depth of layer D.sub.2; and
the intermediate zone of compressive stress has a radial thickness
R from the sidewall of the through-via, wherein the radial
thickness R is equal to the first depth of layer D.sub.1 and the
second depth of layer D.sub.2.
4. The interposer panel of claim 3, wherein the first depth of
layer D.sub.1, the second depth of layer D.sub.2 and the radial
thickness R are from about 5 microns to about 100 microns.
5. The interposer panel of claim 1, wherein a compressive stress in
the first layer of compressive stress, the second layer of
compressive stress and the intermediate zones of compressive stress
is from about 200 MPa to about 1000 MPa.
6. The interposer panel of claim 1, wherein the thickness T of the
glass substrate core is from about 50 microns to about 1
millimeter.
7. The interposer panel of claim 1, wherein the interposer panel
comprises at least one scalloped edge.
8. The interposer panel of claim 7, wherein scalloped portions of
the at least one scalloped edge are filled with a metallic
material, a polymeric material or a frit material.
9.-20. (canceled)
Description
BACKGROUND
[0001] 1. Field
[0002] The present specification generally relates to interposer
panels for electronic package assemblies and, more specifically, to
glass interposer panels for electronic assemblies formed from
strengthened glass.
[0003] 2. Technical Background
[0004] A current trend in the miniaturization of electronic devices
is the 3D integration of electronic components, such as 3D
integrated circuits, on a single substrate such that the electronic
components are stacked thereby forming a more compact package. A
driving force for this trend is consumer demand for mobile and
handheld electronic devices and higher density I/Os as chips become
increasingly complex.
[0005] Currently, organic interposer panels are commonly integrated
into 3D electronic assemblies due to their low cost and ease of
manufacture. However, organic interposer panels exhibit poor
dimensional stability and high thermal mismatch with common
integrated circuit materials, such as silicon, which, in turn,
limits the input/output density and the achievable miniaturization
of the electronic assembly. Further, organic interposer panels
exhibit poor thermal conductivity which also limits the achievable
power density of the electronic assembly.
[0006] Alternatives to organic interposer panels include silicon
interposer panels. Silicon interposer panels exhibit improved
thermal and dimensional characteristics relative to organic
interposer panels. However, silicon interposer panels are
relatively expensive to produce and are limited in size.
[0007] Accordingly, a need exists for alternative interposer panels
with improved strength, durability and suitable thermal
characteristics.
SUMMARY
[0008] According to one embodiment, an interposer panel for an
electronic assembly includes a glass substrate core formed from an
ion-exchangeable glass. The glass substrate core includes a first
surface, a second surface opposite the first surface, and a
thickness T. A first layer of compressive stress may extend from
the first surface of the glass substrate core into the thickness T
of the glass substrate core to a first depth of layer D.sub.1. A
second layer of compressive stress may be spaced apart from the
first layer of compressive stress and extending from the second
surface of the glass substrate core into the thickness T of the
glass substrate core to a second depth of layer D.sub.2. A
plurality of through-vias may extend through the thickness T of the
glass substrate core. Each through-via of the plurality of
through-vias is surrounded by an intermediate zone of compressive
stress that extends from the first layer of compressive stress to
the second layer of compressive stress adjacent to a sidewall of
each through-via.
[0009] In another embodiment, a method for making an interposer
panel for an electronic assembly includes forming a plurality of
through-vias in a glass substrate core. Thereafter, a first layer
of compressive stress, a second layer of compressive stress, and a
plurality of intermediate zones of compressive stress may be
induced in the glass substrate core. The first layer of compressive
stress may extend from a first surface of the glass substrate core
into a thickness T of the glass substrate core to a first depth of
layer D.sub.1. The second layer of compressive stress may extend
from a second surface of the glass substrate core into the
thickness T of the glass substrate core to a second depth of layer
D.sub.2. The first layer of compressive stress is spaced apart from
the second layer of compressive stress. A sidewall of each
through-via of the plurality of through-vias is surrounded by one
of the plurality of intermediate zones of compressive stress. Each
intermediate zone of compressive stress of the plurality of
intermediate zones of compressive stress extends from the first
layer of compressive stress to the second layer of compressive
stress adjacent the sidewall of each through-via.
[0010] In yet another embodiment, a method for making an interposer
panel for an electronic assembly, includes forming a plurality of
through-vias in a glass substrate core comprising ion-exchangeable
glass. Thereafter, the glass substrate core is etched to remove
flaws from the glass substrate core such that a strength of the
glass substrate core is greater than before etching. The glass
substrate core may then be strengthened by ion exchange to form a
first layer of compressive stress extending from a first surface of
the glass substrate core into a thickness T of the glass substrate
core. The first layer of compressive stress may have a first depth
of layer D.sub.1. A second layer of compressive stress may extend
from a second surface of the glass substrate core into a thickness
T of the glass substrate core. The second layer of compressive
stress has a second depth of layer D.sub.2 and is spaced apart from
the first layer of compressive stress. The plurality of
intermediate zones of compressive stress may generally correspond
to the plurality of through-vias such that each through-via of the
plurality of through-vias is surrounded by a corresponding one of
the plurality of intermediate zones of compressive stress.
[0011] Additional features and advantages of the invention will be
set forth in the detailed description which follows, and in part
will be readily apparent to those skilled in the art from that
description or recognized by practicing the embodiments described
herein, including the detailed description which follows, the
claims, as well as the appended drawings.
[0012] It is to be understood that both the foregoing general
description and the following detailed description describe various
embodiments and are intended to provide an overview or framework
for understanding the nature and character of the claimed subject
matter. The accompanying drawings are included to provide a further
understanding of the various embodiments, and are incorporated into
and constitute a part of this specification. The drawings
illustrate the various embodiments described herein, and together
with the description serve to explain the principles and operations
of the claimed subject matter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 schematically depicts a glass interposer panel
according to one or more embodiments shown and described
herein;
[0014] FIG. 2 schematically depicts a cross section of a glass
interposer panel illustrating one configuration of the through-vias
according to one or more embodiments shown and described
herein;
[0015] FIG. 3 schematically depicts a cross section of a glass
interposer panel illustrating another configuration of the
through-vias according to one or more embodiments shown and
described herein;
[0016] FIG. 4 schematically depicts a cross section of a glass
interposer panel illustrating the depth of layer of compressive
stress introduced in the glass interposer panel according to one or
more embodiments shown and described herein;
[0017] FIG. 5 schematically depicts a cross section of a glass
interposer panel with a barrier layer according to one or more
embodiments shown and described herein;
[0018] FIG. 6 schematically depicts a cross section of a glass
interposer panel with a barrier layer and an adhesion layer
according to one or more embodiments shown and described
herein;
[0019] FIG. 7 schematically depicts a cross section of a glass
interposer panel with a barrier layer, and adhesion layer, and
metallized through-vias according to one or more embodiments shown
and described herein;
[0020] FIG. 8 schematically depicts a glass interposer panel with
metallized through-vias according to one or more embodiments shown
and described herein;
[0021] FIG. 9 graphically depicts a plot of the failure stress
(x-axis) as a function of reliability (y-axis) of a glass substrate
core with a single mechanically drilled through-via in i)
as-drilled condition; ii) after chemical etching; and iii) after
chemical etching followed by ion exchange strengthening;
[0022] FIG. 10 graphically depicts a plot of the failure stress
(x-axis) as a function of reliability (y-axis) of a glass substrate
core with multiple mechanically drilled through-vias in i)
as-drilled condition; ii) after chemical etching; and iii) after
chemical etching followed by ion exchange strengthening;
[0023] FIG. 11 graphically depicts a plot of the failure stress
(x-axis) as a function of reliability (y-axis) of a glass substrate
core with a single laser drilled through-via in i) as-drilled
condition; ii) after chemical etching; and iii) after chemical
etching followed by ion exchange strengthening;
[0024] FIG. 12 schematically depicts a glass interposer panel with
a scalloped edge according to one or more embodiments shown and
described herein; and
[0025] FIG. 13 schematically depicts a glass interposer panel with
a metallized scalloped edge according to one or more embodiments
shown and described herein.
DETAILED DESCRIPTION
[0026] Reference will now be made in detail to various embodiments
of glass interposer panels and methods of making the same, examples
of which are illustrated in the accompanying drawings. One
embodiment of a glass interposer panel is schematically depicted in
FIG. 1. The glass interposer panel generally comprises a glass
substrate core formed from an ion-exchangeable glass. A plurality
of through-vias extend through the thickness of the glass substrate
core. A first layer of compressive stress extends from the first
surface of the glass substrate core to a depth of layer D.sub.1. A
second layer of compressive stress extends from the second surface
of the glass substrate core to a depth of layer D.sub.2. Each
through-via of the plurality of through-vias is surrounded by an
intermediate zone of compressive stress that extends from the first
layer of compressive stress to the second layer of compressive
stress adjacent to the sidewall of each through-via. Glass
interposer panels and methods for forming glass interposer panels
will be described in more detail herein with reference to the
appended figures.
[0027] Referring now to FIG. 1, a glass interposer panel 100 is
schematically depicted according to one or more embodiments shown
and described herein. The glass interposer panel 100 generally
comprises a glass substrate core 102 in which a plurality of
through-vias 104 are formed. In the embodiments described herein,
the glass substrate core 102 is formed from a glass composition
which may be chemically strengthened, such as by ion exchange
processing. For example, the glass substrate core 102 may be formed
from soda-lime glass batch compositions, alkali aluminosilicate
glass batch compositions, alkali aluminoborosilicate glass batch
compositions or other glass batch compositions which may be
strengthened by ion exchange after formation. In one particular
example, the glass substrate core 102 is formed from Gorilla.TM.
glass produced by Corning, Inc.
[0028] In one embodiment, the glass substrate core is formed from a
glass composition which has a high coefficient of thermal expansion
(CTE). For example, the CTE of the glass substrate core may be
similar to the CTEs of circuit materials which may be applied to
the glass substrate core, including, without limitation,
semiconductor materials, metallic materials and the like. In one
embodiment the CTE of the glass substrate core may be from about
45.times.10.sup.-7/.degree. C. to about
100.times.10.sup.-7/.degree. C. However, it should be understood
that, in other embodiments, the CTE of the glass substrate core may
be less than about 45.times.10.sup.-7/.degree. C.
[0029] The glass substrate core 102 is generally planar with a
first surface 106 and a second surface 108 positioned opposite to
and planar with the first surface. The glass substrate core 102
generally has a thickness T (FIG. 2) extending between the first
surface 106 and the second surface 108. In the embodiments
described herein the thickness T of the glass substrate core 102 is
from about 50 microns to about 1 mm For example, in one embodiment,
the glass substrate core 102 has a thickness from about 100 microns
to about 150 microns. In another embodiment, the glass substrate
core 102 has as thickness from about 150 microns to about 500
microns. In yet another embodiment, the glass substrate core 102
has a thickness from about 300 microns to about 700 microns.
[0030] The glass substrate core 102 is initially provided in
as-drawn condition (i.e., prior to strengthening by ion exchange)
before the through-vias 104 are formed through the thickness T of
the glass substrate core 102. Thereafter, the through-vias 104 are
formed in the un-strengthened glass substrate core 102 to create
the glass interposer panel 100. Forming the through-vias 104 in the
un-strengthened glass substrate core 102, as described herein,
reduces cracking or chipping of the glass substrate core,
particularly in areas adjacent to the through-vias 104 where the
glass substrate core 102 is susceptible to damage during machining
after ion-exchange strengthening.
[0031] In one embodiment, the glass substrate core 102 may be
annealed prior to forming the through-vias 104. Annealing the glass
substrate core 102 reduces or eliminates residual stresses present
in the glass substrate core 102 which may lead to cracking or
chipping of the glass substrate core during formation of the
through-vias when the residual stresses are present in the glass
substrate core during formation of the through-vias 104. In
embodiments where the glass substrate core 102 is annealed, the
annealing process may comprise heating the glass substrate core to
the annealing point of the glass (i.e., to a temperature where the
dynamic viscosity of the glass is about 1.times.10.sup.13 Poise).
However, it should be understood that the annealing step is
optional and that, in some embodiments, through-vias may be formed
in the glass substrate core without first undergoing an annealing
step.
[0032] The through-vias 104 may be formed in the un-strengthened
glass substrate core 102 using any one of a variety of forming
techniques. For example, the through-vias 104 may be formed by
mechanical drilling, etching, laser ablation, laser assisted
processes, abrasive blasting, abrasive water jet machining, focused
electro-thermal energy or any other suitable forming technique. In
one particular embodiment the through-vias 104 are formed using a
laser ablation technique as described in U.S. Pat. No. 6,990,285
entitled "Method of making at least one hole in a transparent body
and devices made by this method" and assigned to Corning, Inc., the
entirety of which is herein incorporated by reference.
[0033] Referring now to FIGS. 1 and 2, in one embodiment, the
through-vias 104 have a substantially circular cross section in the
plane of the glass substrate core 102 and a diameter ID in the
range from about 10 microns to about 1 mm In the embodiment shown
in FIG. 2, the through-vias 104 have a substantially cylindrical
sidewall 122 such that the diameter ID of each through-via 104 is
the same at the first surface 106 of the glass substrate core 102
and the second surface 108 of the glass substrate core 102. In the
embodiment shown in FIG. 2, each through-via 104 has approximately
the same diameter ID. However, in other embodiments (not shown),
the through-vias may be formed with different diameters. For
example, a first plurality of through-vias may be formed with a
first diameter, while a second plurality of through-vias may be
formed with a second diameter.
[0034] Referring now to FIGS. 1 and 3, in another embodiment, the
through-vias 104 may be formed such that the through-vias 104 are
substantially conical, as depicted in FIG. 3. For example, the
through-vias 104 may be formed such that the sidewall 122 of the
through-via 104 tapers between the first surface 106 of the glass
substrate core 102 and the second surface 108 of the glass
substrate core 102. In this embodiment, the through-vias 104 may
have a first diameter ID.sub.1 at the first surface 106 of the
glass substrate core 102 and a second, different diameter ID.sub.2
at the second surface of the glass substrate core 102.
[0035] In yet another embodiment (not shown), the through-vias 104
may be formed such that the sidewalls of the through-vias taper
from the first surface of the glass substrate core to a mid-plane
of the glass substrate core (i.e., a plane through the glass
substrate core between the first surface of the glass substrate
core and a second surface of the glass substrate core) and expand
from a mid-plane of the glass substrate core to the second surface
of the glass substrate core (i.e., the through-vias have the
general shape of an hour glass through the thickness T of the glass
substrate core 102). In this embodiment, the through-vias 104 may
have first diameter at the first surface of the glass substrate
core, a second diameter at the second surface of the glass
substrate core, and a third diameter at a mid-plane of the glass
substrate core such that the first diameter and the second diameter
are greater than the third diameter. In one embodiment, the first
diameter and the second diameter may be equal.
[0036] While specific reference has been made herein to
through-vias with different cross-sectional geometries through the
thickness of the glass substrate core, it should be understood that
the through-vias may take on a variety of other cross-sectional
geometries and, as such, the embodiments described herein are not
limited to any particular cross-sectional geometry of the
through-vias.
[0037] While FIGS. 2 and 3 depict embodiments of through-vias with
substantially cylindrical sidewalls and embodiments of through-vias
with substantially conical sidewalls, it should be understood that
both types of through-vias may be formed in a single glass
interposer panel 100. Further, in the embodiment of the glass
interposer panel 100 depicted in FIG. 1, the through-vias 104 are
formed in the un-strengthened glass substrate core in a regular
pattern. However, it should be understood that, in other
embodiments, the through-vias 104 may be formed in a non-regular
pattern.
[0038] Moreover, while the through-vias 104 are depicted as having
a circular cross section in the plane of the glass substrate core
102 in the embodiment of the glass interposer panel 100 depicted in
FIG. 1, it should be understood that the through-vias may have
other planar cross-sectional geometries. For example, the
through-vias may have various other cross sectional geometries in
the plane of the glass substrate core, including, without
limitation, elliptical cross sections, square cross sections,
rectangular cross sections, triangular cross sections, and the
like. Further, it should be understood that through-vias 104 with
different cross sectional geometries may be formed in a single
interposer panel.
[0039] In the embodiments of the glass interposer panel 100 shown
and described herein, the glass interposer panel 100 is formed with
a plurality of through-vias 104. However, in other embodiments (not
shown), the glass interposer panel 100 may also include one or more
blind-vias, such as when a via does not extend through the
thickness T of the glass substrate core 102. In these embodiments,
the blind-vias may be formed using the same techniques as the
through-vias and may have similar dimensions and planar
cross-sectional geometries as the through-vias.
[0040] In one embodiment, the glass interposer panel 100 may be
annealed after formation of the through-vias 104. In this
embodiment, the annealing step may be utilized to reduce stresses
that develop in the glass interposer panel 100 during formation of
the through-vias 104. For example, where laser-assisted processing
is used to form the through-vias 104, thermal stresses may remain
in the glass substrate core after formation of the through-vias.
The annealing step may be utilized to relieve these residual
stresses such that the glass interposer panel 100 is substantially
stress-free. However, it should be understood that an annealing
step performed after formation of the through-vias is optional and
that, in some embodiments, the glass interposer panel 100 is not
annealed after formation of the through-vias.
[0041] In another embodiment, the glass substrate core 102 may be
chemically etched after formation of the through-vias. For example,
the glass substrate core may be chemically etched by submerging the
glass substrate core in an acid solution which removes defects from
the surface of the glass substrate core and from the interior of
the through-vias. Removing these defects by etching reduces the
number of crack initiation locations in the interposer panel and,
as a result, improves the strength of the glass interposer panel.
In one embodiment, where the glass interposer panel is formed from
Gorilla.TM. glass, the glass interposer panel may be chemically
etched in a solution of HF:HCl:20H.sub.2O for 15 minutes to remove
defects from the surface of the glass interposer panels and from
the through-vias. However, it should be understood that the
chemical etching step after formation of the through-vias is
optional and that, in some embodiments, the glass interposer panel
is not chemically etched after formation of the through-vias.
[0042] After the through-vias 104 have been formed in the glass
substrate core 102, the glass interposer panel is chemically
strengthened with an ion exchange process in which smaller metal
ions in the glass are replaced or "exchanged" with larger metal
ions of the same valence within a layer of the glass that is close
to the outer surface of the glass. The replacement of smaller ions
with larger ions creates a compressive stress within the surface of
the glass which extends to a depth of layer (DOL). In one
embodiment, the metal ions are monovalent alkali metal ions (e.g.,
Na.sup.+, K.sup.+, Rb.sup.+, and the like), and ion exchange is
accomplished by immersing the substrate in a bath comprising at
least one molten salt (e.g., KNO.sub.3, K.sub.2SO.sub.4, KCl, or
the like) of the larger metal ion that is to replace the smaller
metal ion in the glass. Alternatively, other monovalent cations
such as Ag.sup.+, Tr, Cu.sup.+, and the like can be exchanged for
the alkali metal cations in the glass. The ion exchange process or
processes that are used to strengthen the glass interposer panels
can include, but are not limited to, immersion of the glass in a
single bath or immersion of the glass in multiple baths of like or
different compositions with washing and/or annealing steps between
immersions.
[0043] By way of example, in the embodiments described herein where
the glass interposer panel 100 is formed from a glass substrate
core 102 comprising Gorilla.TM. glass, the glass interposer panel
may be ion exchange strengthened by immersing the glass substrate
core in a KNO.sub.3 molten salt bath having a temperature of
410.degree. C. When the glass substrate core is immersed in the
salt bath, Na.sup.+ ions in the un-strengthened glass substrate
core are exchanged with K.sup.+ ions thereby introducing
compressive stress in the glass substrate core. The magnitude and
the depth of layer (DOL) of the compressive stress introduced in
the glass substrate core 102 generally depends on the length of
time the glass substrate core is immersed in the salt bath. For
example, immersing a glass substrate core formed from 0.7 mm thick
Gorilla.TM. glass in a KNO.sub.3 salt bath at a temperature of
410.degree. C. for 7 hours produces a compressive stress of
approximately 720 MPa and a depth of layer of 50 microns.
[0044] While reference has been made herein to a specific ion
exchange strengthening process used in conjunction with a specific
glass composition, it should be understood that other ion exchange
processes may also be used. Moreover, it should be understood that
the ion exchange process utilized to strengthen the glass
interposer panel may vary depending on the specific composition of
the glass substrate core from which the glass interposer panel is
formed.
[0045] Referring now to FIG. 4, chemically strengthening the glass
interposer panel 100 induces a first layer 110 of compressive
stress which extends from the first surface 106 of the glass
substrate core 102 into the thickness of the glass substrate core
to a depth of layer D.sub.1. Similarly, chemically strengthening
the glass interposer panel 100 induces a second layer 112 of
compressive stress which extends from the second surface 108 of the
glass substrate core 102 into the thickness of the glass substrate
core 102 to a depth of layer D.sub.2. The first layer 110 of
compressive stress and the second layer 112 of compressive stress
are spaced apart from one another by a layer of central tension
113. In one embodiment described herein, the compressive stress may
be from about 200 MPa to about 1000 MPa. In another embodiment, the
compressive stress may be from about 500 MPa to about 800 MPa. In
yet another embodiment, the compressive stress may be from about
650 MPa to about 900 MPa. In the embodiments described herein, the
first depth of layer D.sub.1 is substantially equal to the second
depth of layer D.sub.2. In one embodiment, the first and the second
depth of layer may each be from about 5 microns to about 100
microns. In another embodiment, the first and the second depth of
layer may each be from about 30 microns to about 60 microns. In yet
another embodiment, the first and the second depth of layer may
each be from about 40 microns to about 60 microns.
[0046] Further, chemically strengthening the glass interposer panel
100 after the through-vias 104 have been formed in the glass
substrate core 102 creates a plurality of intermediate zones 114 of
compressive stress which surround each of the through-vias 104 and
extend from the sidewall 122 of the through-via 104 into the glass
substrate core. For example, each intermediate zone 114 of
compressive stress forms around and directly adjacent to the
sidewall of a corresponding through-via 104 such that the
through-via 104 is surrounded by a cylinder of compressive stress
which extends from the first surface 106 of the glass substrate
core 102 to the second surface 108 of the glass substrate core. In
the embodiments described herein, each intermediate zone 114 of
compressive stress extends from the first layer 110 of compressive
stress to the second layer 112 of compressive stress such that a
cylinder of glass surrounding the through-via is under compression
through the thickness of the glass substrate core 102. Each
intermediate zone 114 of compressive stress has a radial thickness
R. In one embodiment described herein, the radial thickness R is
substantially equal to the first depth of layer D.sub.1 and the
second depth of layer D.sub.2. Accordingly, it should be understood
that, in some embodiments, the intermediate zone 114 of compressive
stress surrounding each through-via 104 may have a radial thickness
from about 5 microns to about 100 microns, while in other
embodiments the radial thickness may be from about 30 microns to
about 60 microns. In still other embodiments the radial thickness R
is from about 40 microns to about 60 microns. In the embodiments
described herein, the compressive stress in each zone of
compressive stress may be from about 200 MPa to about 1000 MPa. For
example, in one embodiment, the compressive stress in each
intermediate zone of compressive stress may be from about 500 MPa
to about 800 MPa. In yet another embodiment, the compressive stress
in each intermediate zone of compressive stress may be from about
650 MPa to about 900 MPa.
[0047] The intermediate zones 114 of compressive stress induced
around each through-via 104 reduce the propensity of the glass
interposer panel to fail from cracks which initiate from the
sidewall of the through-vias 104. Accordingly, the intermediate
zones 114 of compressive stress induced around the through-vias 104
improve the overall strength of the glass interposer panel 100.
Moreover, the intermediate zones 114 of compressive stress induced
around the through-vias may actually increase the strength of the
glass interposer panel 100 to levels which exceed the strength of
the glass substrate core prior to forming the through-vias, as will
be described in more detail herein with reference to specific
examples.
[0048] Referring now to FIGS. 1 and 12-13, in some embodiments,
after the through-vias 104 are formed and the glass interposer
panel 100 is chemically strengthened, the glass interposer panel
100 may be separated into sub-panels before additional processing
occurs. In one embodiment, the glass interposer panel 100 is
separated along at least one parting line 131 which extends across
a row of through-vias 104, as shown in FIG. 1. When the glass
interposer panel 100 is separated using this technique, a sub-panel
140 (FIG. 12) may be produced which has at least one scalloped edge
142. The scalloped portions 144 of the scalloped edge 142 may have
a compressive layer which extends through the thickness of the
sub-panel 140 due to the ion exchange strengthening. Accordingly,
the scalloped edge 142 may have additional edge strength and an
improved resistance to fracture. In this embodiment, the scalloped
portions 144 of the scalloped edge 142 may be filled with a filler
material. For example, in the embodiment depicted in FIG. 13, the
scalloped portions 144 may be metallized or filled with a
conductive material, such as a metallic material 120, to provide a
series of metal pads along the scalloped edge 142. The metal pads
may be used as electrical connections to and from the sub-panel
140. Suitable materials for metallizing the scalloped portions 144
may include, without limitation, copper and copper alloys, gold and
gold alloys, silver and silver alloys, platinum and platinum alloys
or aluminum and aluminum alloys. In an alternative embodiment, the
scalloped portions 144 may be filled with other filler materials
including, without limitation, polymeric materials, frit materials
and the like, to serve other functionalities, such as insulating
the panel or providing protection to the edges of the panel.
[0049] In other embodiments, after the through-vias 104 are formed
and the glass interposer panel 100 is chemically strengthened,
additional material layers and/or components may be added to the
glass interposer panel 100 to prepare the glass interposer panel
100 for use in an electronic assembly. For example, referring to
FIG. 5, a barrier layer 116 may be applied to the glass substrate
core 102 after the glass interposer panel 100 has been strengthened
by ion exchange. In the embodiments described herein, the barrier
layer 116 is applied to the glass substrate core 102 such that the
barrier layer 116 coats the first surface 106 of the glass
substrate core 102, the second surface 108 of the glass substrate
core 102, and the sidewalls 122 of the through-vias 104, as
depicted in FIG. 5. In other embodiments (not shown), the barrier
layer 116 may be applied to the first surface 106 and/or the second
surface 108. The barrier layer 116 prevents the diffusion of alkali
ions from the glass substrate core 102 into materials and/or
components positioned on the glass substrate core 102. Accordingly,
it should be understood that the barrier layer 116 may be formed
from any composition suitable for preventing the diffusion of
alkali ions from the glass substrate core 102. For example, in one
embodiment, the barrier layer is formed from silicon nitride
applied to the substrate to a thickness ranging from a few
nanometers to a few microns. In another embodiment, the barrier
layer may be formed from materials other than silicon nitride,
including, without limitation silicon oxide, silicon dioxide, or
silicon carbide.
[0050] Referring now to FIG. 6, in another embodiment, an adhesion
layer 118 is applied to the glass interposer panel 100 over the
barrier layer 116. In the embodiments described herein, the
adhesion layer 118 is applied to the glass interposer panel 100
such that the adhesion layer 118 is applied over the barrier layer
116. In the embodiments described herein, the adhesion layer 118
coats the first surface 106 of the glass substrate core 102, the
second surface 108 of the glass substrate core 102, and the
sidewalls of the through-vias 104, as depicted in FIG. 5. However,
in other embodiments (not shown), the adhesion layer 118 may be
applied to the sidewalls of the through-vias 104 and in a ring
around the through-vias 104 on the first surface 106 and/or the
second surface 108. The adhesion layer 118 is generally formed from
a material that promotes the adhesion of additional materials
subsequently applied to the glass interposer panel 100 including,
without limitation, metals, dielectric materials, semiconductor
materials, and the like. In the embodiments described herein the
adhesion layer 118 may be formed from various materials including,
without limitation, titanium, titanium alloys, chrome, chrome
alloys, copper or copper alloys. For example, in one embodiment,
the adhesion layer is formed from copper applied to the substrate
to a thickness of less than a nanometer. For example, in one
embodiment, the adhesion layer is has a thickness on the order of
several atomic layer (i.e., a layer having a thickness of several
atoms of the material of the adhesion layer. In another embodiment,
the adhesion layer may be formed from other materials, including,
without limitation, silanes. While the adhesion layer 118 is
applied over the barrier layer 116, it should be understood that,
in other embodiments, the adhesion layer 118 may be applied
directly to the first surface of the glass substrate core, the
second surface of the glass substrate core, the sidewall of each of
the through-vias, or combinations thereof
[0051] Referring now to FIG. 7, after the adhesion layer 118 is
applied to the glass interposer panel 100, the through-vias 104 may
be metallized by filling the through-vias 104 with a conductive
material 120 such as a conductive metallic material. For example,
in one embodiment, the through-vias 104 may be metallized by
depositing a conductive material, such as copper or a copper alloy,
in the through-vias thereby providing a conductive pathway through
the thickness of the glass interposer panel 100. Suitable materials
for metallizing the through-vias may include, without limitation,
copper and copper alloys, gold and gold alloys, silver and silver
alloys, platinum and platinum alloys, or aluminum and aluminum
alloys.
[0052] After the through-vias have been metallized, one or more
dielectric layers (not shown) and/or electrical components (not
shown), such as integrated circuit components, analog circuit
components, semiconductor materials, or the like, may be positioned
on the glass interposer panel 100 to form a three-dimensional
electronic assembly.
[0053] Referring to FIG. 8, in some embodiments, before dielectric
layers and/or electrical components are added to the glass
interposer panel 100, the glass interposer panel 100 may be
separated into a plurality of smaller panels 150 along parting
lines 130. Various separation techniques may be used to separate
the glass interposer panel 100 along the parting lines 130
including, without limitation, laser score and break techniques,
mechanical score and break techniques, laser through cutting and
the like. In embodiments where the central tension in the glass
interposer panel 100 is less than approximately 20 MPa, laser score
and break techniques employing a CO.sub.2 laser or even mechanical
scribe and break techniques may be utilized to facilitate
separation. However, in embodiments where the glass interposer
panels have high levels of central tension, laser through cutting
techniques may be employed to facilitate separation.
EXAMPLES
[0054] The embodiments described herein will be further clarified
by the following examples.
[0055] In each of the following Examples the glass substrates and
glass interposer panels were tested to failure using the
ring-on-ring testing technique described in ASTM C1499-09: Standard
Test Method for Monotonic Equibiaxial Flexural Strength of Advanced
Ceramics at Ambient Temperature. Each set of samples consisted of
10 samples and the average failure stress for the set of 10 samples
was determined by averaging the failure stress for each individual
sample in the set.
[0056] In order to establish a baseline reference for each of the
following examples, a 50 mm.times.50 mm.times.0.7 mm thick
Gorilla.TM. glass substrate without through-vias and without ion
exchange strengthening was mechanically tested to failure using
ring-on-ring testing. The failure stress was determined to be
approximately 450 MPa based on testing. In addition, a 50
mm.times.50 mm.times.0.7 mm thick Gorilla.TM. glass substrate
without through-vias was ion exchange strengthened in molten
KNO.sub.3 at 410.degree. C. for 7 hours to produce a compressive
stress of 720 MPa extending to a depth of layer of 50 microns. The
glass substrate was mechanically tested to failure using
ring-on-ring testing. The failure stress was determined to be
approximately 615 MPa.
Example 1
[0057] Threes sets of 50 mm.times.50 mm glass interposer panels
were formed from Gorilla.TM. alkali aluminosilicate glass. Each
glass interposer panel had a thickness of 0.7 mm In this example, a
single through-via having a diameter of 1 mm was mechanically
drilled at the center of each glass interposer panel, as indicated
in FIG. 9. A first set of glass interposer panels were then
mechanically tested to failure in as-drilled condition (i.e.,
without further processing) using ring-on-ring testing. The applied
stress at failure (i.e., the failure stress) was recorded.
[0058] A second set of glass interposer panels were chemically
etched in a solution of HF:HCl:20H.sub.2O for 15 minutes to remove
defects from the surfaces of the glass interposer panels and from
the through-vias. Each of the glass interposer panels in the second
set of glass interposer panels was then mechanically tested to
failure using ring-on-ring testing. The applied stress at failure
for each glass interposer panel was recorded.
[0059] A third set of glass interposer panels with single 1 mm
diameter through-vias were chemically etched in a solution of
HF:HCl:20H.sub.2O for 15 minutes to remove defects from the surface
of the glass interposer panels and from the through-vias.
Thereafter, each of the glass interposer panels was ion exchange
strengthened in molten KNO.sub.3 at 410.degree. C. for 7 hours. The
resulting layer of compressive stress extended from each surface of
the glass interposer panel to a depth of layer of approximately 50
microns. The ion exchange strengthening also formed an intermediate
zone of compressive stress surrounding the sidewall of the
through-via and extending from the sidewall of the through-via into
the glass interposer panel such that the intermediate zone of
compressive stress had a radial thickness of approximately 50
microns. The compressive stress of the first layer of compressive
stress, the second layer of compressive stress, and the
intermediate zone of compression was approximately 720 MPa.
Thereafter, the third set of glass interposer panels were
mechanically tested to failure using ring-on-ring testing. The
failure stress of each glass interposer panel was recorded.
[0060] Referring now to FIG. 9, the strengths of the glass
interposer panels of Example 1 are graphically illustrated in a
Weibull plot of the failure stress (x-axis) and the reliability
(y-axis). As shown in FIG. 9, the as-drilled glass interposer
panels had an average failure stress of approximately 100 MPa thus
indicating that the glass was significantly weakened after
formation of the through-via relative to an un-drilled glass
substrate. However, the average failure stress of the samples
treated by chemical etching was approximately 400 MPa indicating a
4.times. strength improvement over the as-drilled, non-chemically
etched glass interposer panels and also indicating that the
chemical etching process restored the strength of the as-drilled
interposer panel to approximately 90% of the strength of a
comparable glass substrate without a through-via. Moreover, the
average failure stress of samples treated by chemical etching
followed by ion-exchange strengthening was approximately 2000 MPa
indicating a 20.times. strength improvement over the as-drilled,
non-chemically etched glass interposer panels and a 5.times.
improvement over the as-drilled, chemically etched glass interposer
panels.
Example 2
[0061] Three sets of 50 mm.times.50 mm glass interposer panels were
formed from Gorilla.TM. alkali aluminosilicate glass. Each glass
interposer panel had a thickness of 0.7 mm In this example, five
through-vias were mechanically drilled in the glass interposer
panel in a cross-configuration, as indicated in FIG. 10. Each
through-via had a diameter of 1 mm and an edge-to-edge spacing of
300 microns. A first set of glass interposer panels was
mechanically tested to failure in as-drilled condition (i.e.,
without further processing) using ring-on-ring testing. The applied
stress at failure (i.e., the failure stress) was recorded.
[0062] A second set of glass interposer panels were chemically
etched in a solution of HF:HCl:20H.sub.2O for 15 minutes to remove
defects from the surfaces of the glass interposer panels and from
the through-vias, as described above. Each of the glass interposer
panels in the second set of glass interposer panels was
mechanically tested to failure using ring-on-ring testing. The
applied stress at failure for each glass interposer panel was
recorded.
[0063] A third set of glass interposer panels with 5 through-vias
were chemically etched in a solution of HF:HCl:20H.sub.2O for 15
minutes, as described above and, thereafter, each of the glass
interposer panels was ion exchange strengthened in molten KNO.sub.3
at 410.degree. C. for 7 hours resulting in a compressive stress of
approximately 720 MPa extending to a depth of layer of
approximately 50 microns. The ion exchange strengthening formed an
intermediate zone of compressive stress surrounding the sidewall of
the through-vias and extending from the sidewalls of the
through-vias into the glass interposer panel such that the
intermediate zone of compressive stress had a radial thickness of
approximately 50 microns. Thereafter, the third set of glass
interposer panels were mechanically tested to failure using
ring-on-ring testing. The failure stress of each glass interposer
panel was recorded.
[0064] Referring now to FIG. 10, the strength of the glass
interposer panels of Example 2 are graphically illustrated in a
Weibull plot of the failure stress (x-axis) and the reliability
(y-axis). As shown in FIG. 10, the as-drilled glass interposer
panels had an average failure stress of less than 100 MPa thus
indicating that the glass was significantly weakened after
formation of the through-vias. However, the average failure stress
of the samples treated by chemical etching was approximately 300
MPa, approximately 3.times. greater than the as-drilled,
non-chemically etched glass interposer panels. Moreover, the
average failure stress of samples treated by chemical etching
followed by ion-exchange strengthening was approximately 1000 MPa
indicating a 10.times. strength improvement over the as-drilled,
non-chemically etched glass interposer panels.
Example 3
[0065] Threes sets of 50 mm.times.50 mm glass interposer panels
were formed from Gorilla.TM. alkali aluminosilicate glass. Each
glass interposer panel had a thickness of 0.7 mm In this example, a
single through-via having a diameter of 1 mm was laser drilled at
the center of each glass interposer panel using a femtosecond laser
trepanning technique. A first set of glass interposer panels were
then mechanically tested to failure in as-drilled condition (i.e.,
without further processing) using ring-on-ring testing. The applied
stress at failure (i.e., the failure stress) was recorded.
[0066] A second set of glass interposer panels were chemically
etched in a solution of HF:HCl:20H.sub.2O for 15 minutes to remove
defects from the surfaces of the glass interposer panels and from
the through-vias. Each of the glass interposer panels in the second
set of glass interposer panels was then mechanically tested to
failure using ring-on-ring testing. The applied stress at failure
for each glass interposer panel was recorded.
[0067] A third set of glass interposer panels with single 1 mm
diameter through-vias were chemically etched in a solution of
HF:HCl:20H.sub.2O for 15 minutes to remove defects from the surface
of the glass interposer panels and from the through-vias.
Thereafter, each of the glass interposer panels was ion exchange
strengthened in molten KNO.sub.3 at 410.degree. C. for 7 hours. The
resulting layer of compressive stress extended from each surface of
the glass interposer panel to a depth of layer of approximately 50
microns. The ion exchange strengthening also formed an intermediate
zone of compressive stress surrounding the sidewall of the
through-via and extending from the sidewall of the through-via into
the glass interposer panel such that the intermediate zone of
compressive stress had a radial thickness of approximately 50
microns. The compressive stress of the first layer of compressive
stress, the second layer of compressive stress, and the
intermediate zone of compression was approximately 720 MPa.
Thereafter, the third set of glass interposer panels were
mechanically tested to failure using ring-on-ring testing. The
failure stress of each glass interposer panel was recorded.
[0068] Referring now to FIG. 11, the strengths of the glass
interposer panels of Example 3 are graphically illustrated in a
Weibull plot of the failure stress (x-axis) and the reliability
(y-axis). As shown in FIG. 11, the strength of the interposer
panels of Example 3 followed a similar trend as the interposer
panels with mechanically drilled through-vias in Examples 1 and 2.
Specifically, the strength of the interposer panels after chemical
etching improved relative to the strength of the interposer panels
in as-drilled condition. Further, the strength of the interposer
panels after chemical etching and ion exchange strengthening
improved relative to the strength of the interposer panels which
were only chemically etched.
[0069] While Examples 1-3 describe glass interposer panels which
are chemically etched prior to ion exchange strengthening, it
should be understood that, in alternative embodiments, the glass
interposer panels may be ion exchange strengthened without being
chemically etched prior to ion exchange strengthening.
[0070] Based on the foregoing, it should be understood that the
methods described herein may be used to form glass interposer
panels with increased strength. Specifically, the glass interposer
panels described herein are less susceptible to failure from cracks
propagating from through-vias formed in the glass interposer panels
and, as such, may be readily incorporated into three-dimensional
electronic assemblies without an increased risk of failure due to
cracking. Further, the thermal characteristics of the glass
interposer panels described herein are compatible with materials
commonly used in the manufacture of integrated circuits. Moreover,
the glass interposer panels described herein are dimensionally
stable over a broad range of operating temperatures.
[0071] It will be apparent to those skilled in the art that various
modifications and variations can be made to the embodiments
described herein without departing from the spirit and scope of the
claimed subject matter. Thus it is intended that the specification
cover the modifications and variations of the various embodiments
described herein provided such modification and variations come
within the scope of the appended claims and their equivalents.
* * * * *