U.S. patent application number 10/683759 was filed with the patent office on 2005-04-28 for adhesion between carbon doped oxide and etch stop layers.
Invention is credited to Jain, Ajay, Ott, Andrew, Xu, Jessica, Zhou, Ying.
Application Number | 20050087517 10/683759 |
Document ID | / |
Family ID | 34520562 |
Filed Date | 2005-04-28 |
United States Patent
Application |
20050087517 |
Kind Code |
A1 |
Ott, Andrew ; et
al. |
April 28, 2005 |
Adhesion between carbon doped oxide and etch stop layers
Abstract
The invention forms a graded modified layer in a substrate by
exposing the substrate to hydrogen plasma. Methyl groups may be
removed from carbon doped oxide in the substrate by the hydrogen
plasma treatment. This may result in a stronger interface between
the substrate and an etch stop layer on the substrate.
Inventors: |
Ott, Andrew; (Hillsboro,
OR) ; Jain, Ajay; (Portland, OR) ; Zhou,
Ying; (Tigard, OR) ; Xu, Jessica; (Portland,
OR) |
Correspondence
Address: |
Michael A. Bernadicou
BLAKELY, SOKOLOFF, TAYLOR & ZAFMAN LLP
Seventh Floor
12400 Wilshire Boulevard
Los Angeles
CA
90025
US
|
Family ID: |
34520562 |
Appl. No.: |
10/683759 |
Filed: |
October 9, 2003 |
Current U.S.
Class: |
216/67 ;
257/E21.277; 257/E21.576; 257/E23.167 |
Current CPC
Class: |
H01L 21/02362 20130101;
H01L 21/31633 20130101; H01L 23/5329 20130101; H01L 2924/0002
20130101; H01L 21/76829 20130101; H01L 2924/0002 20130101; H01L
21/02126 20130101; H01L 21/0234 20130101; H01L 2924/00 20130101;
H01L 21/76826 20130101 |
Class at
Publication: |
216/067 |
International
Class: |
C23F 001/00 |
Claims
We claim:
1. A method, comprising: forming a substrate with a top surface;
exposing the top surface of the substrate to hydrogen plasma to
remove methyl groups from the top surface; and depositing an
intermediate layer on the top surface of the substrate.
2. The method of claim 1, wherein the intermediate layer comprises
at least one of an etch stop layer and a diffusion barrier
layer.
3. The method of claim 2, wherein the intermediate layer comprises
at ieast one of SiN, SiON and SiC.
4. The method of claim 2, wherein the substrate comprises at least
one of carbon doped oxide, a spin on dielectric layer, and porous
carbon doped oxide that includes the methyl groups.
5. The method of claim 4, wherein exposing the top surface of the
substrate to hydrogen plasma to remove methyl groups comprises:
disposing the substrate within a plasma chamber; exposing the
substrate to a flow of hydrogen into the plasma chamber; and
applying a radio frequency power for a selected time.
6. The method of claim 5, wherein the substrate is part of a wafer
with a diameter of about 300 mm, and wherein the radio frequency
power has a range from about 200 Watts to about 1000 Watts.
7. The method of claim 5, wherein the substrate is part of a wafer
with a diameter of about 300 mm, and wherein the radio frequency
power has a range from about 400 Watts to about 600 Watts for a 300
mm wafer.
8. The method of claim 5, wherein the selected time is in a range
from about 4 seconds to about 30 seconds.
9. The method of claim 5, wherein the selected time is in a range
from about 10 seconds to about 15 seconds.
10. The method of claim 5, wherein the substrate is exposed to
hydrogen plasma at a temperature in a range from about 200 degrees
Celsius to about 450 degrees Celsius.
11. The method of claim 5, wherein the flow of hydrogen into the
plasma chamber has a flow rate in a range of about 0.1 liter per
minute to about 10 liters per minute.
12. The method of claim 5, wherein the substrate is exposed to
hydrogen plasma at a pressure in a range from about 1 Torr to about
10 Torr.
13. The method of claim 5, wherein the substrate is exposed to
hydrogen plasma at a pressure in a range from about 2 Torr to about
5 Torr.
14. The method of claim 1, wherein exposing the top surface of the
substrate to hydrogen plasma results in a graded modified region of
reduced methyl groups with fewer methyl groups at the top surface
of the substrate.
15. The method of claim 14, wherein the graded modified region
extends less than about 100 angstroms below the top surface of the
substrate.
16. The method of claim 14, wherein the graded modified region
extends less than about 50 angstroms below the top surface of the
substrate.
17. A device, comprising: a substrate with a top surface; a graded
region of the substrate starting at the top surface of the
substrate and extending a distance into the substrate, the graded
region having fewer methyl groups at the top surface of the
substrate and more methyl groups further into the substrate; and an
intermediate layer on the top surface of the substrate.
18. The device of claim 17, wherein the graded region extends less
than about 100 angstroms below the top surface of the
substrate.
19. The device of claim 17, wherein the graded region extends less
than about 50 angstroms below the top surface of the substrate.
20. The device of claim 17, wherein the intermediate layer
comprises at least one of an etch stop layer and a diffusion
barrier layer.
21. The device of claim 20, wherein the intermediate layer
comprises at least one of SiN, SiON and SiC.
22. The device of claim 21, wherein the substrate comprises at
least one of carbon doped oxide, spin on dielectric, and porous
carbon doped oxide that includes the methyl groups.
23. The device of claim 17, further comprising an interlayer
dielectric layer.
24. The device of claim 17, further comprising: an interlayer
dielectric layer; a via extending from the substrate through the
intermediate layer and the interlayer dielectric layer; a connector
electrically connected to the via; and a package electrically
connected to the connector.
25. A method, comprising: forming a first layer comprising carbon
doped oxide; exposing the carbon doped oxide to hydrogen plasma to
remove methyl groups from the carbon doped oxide; and depositing a
second layer comprising at least one of SiN and SiC on the first
layer.
26. The method of claim 25, wherein exposing the carbon doped oxide
to hydrogen plasma comprises: disposing the carbon doped oxide
within a plasma chamber; flowing hydrogen into the chamber at a
rate of about 1 liter per minute; heating the carbon doped oxide to
a temperature in a range of about 200 degrees Celsius to about 450
degrees Celsius; and applying a radio frequency power in a range
from about 400 Watts to about 600 Watts for a time in a range from
about 10 seconds to about 15 seconds.
Description
BACKGROUND
[0001] 1. Field of the Invention
[0002] This invention relates to layers in microelectronic
circuits, and more particularly to adhesion strength between layers
of microelectronic circuits.
BACKGROUND OF THE INVENTION
[0003] FIG. 1 is a side cross sectional view of a mircroelectronic
circuit package assembly 100. A die 102 is connected to a package
110 by connectors 112, such as solder balls. The die 102 may
include multiple layers, such as an etch stop layer 104 and a
substrate layer 106. There is an interface 108 between the two
layers 104, 106 in the die 102. Such an interface may be between an
etch stop layer 104 and a carbon doped oxide layer that is located
at the upper surface of the substrate layer 106.
[0004] During fabrication of the package assembly 100, the package
110 and die 102 may be raised to an elevated temperature.
Subsequently, as the temperature decreases, the package 110 and die
102 may have different coefficients of thermal expansion and/or may
cool at different rates. This may cause stresses to occur between
the package 110 and the die 102 and/or within the die 102, such as
at the interface 108 between the etch stop layer 104 and the
substrate layer 106.
[0005] In conventional package assemblies 100, the connectors 112
may be solder balls that comprise a lead-tin alloy. Such connectors
112 are relatively soft. Stresses generated by differing
coefficients of thermal expansion and/or cooling rates between the
package 110 and the die 102 may cause such soft solder ball
connectors 112 to deform. This deformation may act to reduce
stresses acting on the interface 108 between layers 104, 106 in the
die 102.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] The present invention is illustrated by way of example and
is not limited in the figures of the accompanying drawings, in
which like references indicate similar elements. Features shown in
the drawings are not intended to be drawn to scale, nor are they
intended to be shown in precise positional relationship.
[0007] FIG. 1 is a side cross sectional view of a microelectronic
circuit package assembly.
[0008] FIG. 2 is a side cross sectional view of a package assembly
with a strengthened interface between an etch stop layer and a
substrate.
[0009] FIGS. 3a through 3d are cross sectional side views that
illustrate how a die may be fabricated with a stronger interface
between a substrate and etch stop layer.
[0010] FIG. 4 is a chart that illustrates how methyl groups may be
removed by the hydrogen plasma treatment.
[0011] FIG. 5 is a chart that illustrates how the interface may be
strengthened by applying the hydrogen plasma treatment to the
substrate.
DETAILED DESCRIPTION
[0012] In the following detailed description of embodiments of the
invention, reference is made to the accompanying drawings in which
like references indicate similar elements. The illustrative
embodiments described herein are disclosed in sufficient detail to
enable those skilled in the art to practice the invention. The
following detailed description is therefore not to be taken in a
limiting sense, and the scope of the invention is defined only by
the appended claims.
[0013] FIG. 2 is a side cross sectional view of a package assembly
200 with a strengthened interface 208 between an etch stop layer
206 and a substrate 204 according to one embodiment of the present
invention. The package assembly 200 may include a die 202 connected
to a package 214 by connectors 216. The connectors 216 may comprise
a stiff material such as copper that deforms relatively little in
comparison with lead-containing solder balls. These stiffer
connectors 216 may include substantially no lead. Such stiffer
connectors 216 may therefore subject the die 202 to more stress
during heating and cooling, due to differing coefficients of
thermal expansion and/or cooling rates of the package 214 and die
202, than softer connectors that deform to reduce the stress to
which the die 202 is subjected.
[0014] The die 202 may include a substrate 204. In an embodiment,
the substrate 204 may include carbon doped oxide ("CDO") material
at a top surface. This CDO material may act as a dielectric with a
low dielectric constant (a low "k"). Above the substrate 204 may be
an etch stop layer 206. Alternatively, the etch stop layer 206 may
be a diffusion barrier layer 206. The term "etch stop layer" will
therefore refer to both an etch stop layer and a diffusion barrier
layer. In some embodiments, the etch stop layer 206 may comprise a
material such as SiN or SiC. There may be an interface 208 between
the etch stop layer 206 and the substrate 204. Stiff connectors
216, such as copper connectors 216, may cause relatively high
stresses to act on the interface 208. The interface 208 may be
strengthened so that it may withstand increased stress resulting to
that the etch stop layer 206 remains adhered to the substrate 204.
Such a strengthening may be achieved through modifying a portion of
the substrate 204 to increase adhesion between the substrate 204
and the etch stop layer 206.
[0015] There may also be an interlayer dielectric ("ILD") layer 210
above the etch stop layer 206. The ILD layer 210 may comprise a
material with a low k, such as SiO2, SiOF, CDO, polymer-containing
dielectrics, or other dielectric materials. Extending through the
ILD layer 210 and the etch stop layer 206 may be a via or
interconnect 216. The via 216 may comprise a conductive material
such as aluminum, copper, or other conductive materials. This via
216 may electrically connect a conductor on the top surface of the
substrate 204 to a connector 216. This connector 216 may then
electrically connect the conductor on the top surface of the
substrate to a conductor in the package 214.
[0016] FIGS. 3a through 3d are cross sectional side views that
illustrate how a die 202 may be fabricated with a stronger
interface 208 between a substrate 204 and etch stop layer 206,
according to one embodiment. This may be done by use of a plasma
enhanced chemical vapor deposition ("PECVD") treatment, where
hydrogen plasma is used to modify carbon doped oxide ("CDO")
material in the substrate 204.
[0017] FIG. 3a is a cross sectional side view that illustrates the
substrate 204 according to one embodiment. The substrate 204 may be
any layer generated when making an integrated circuit. The
substrate 204 thus may comprise, for example, active and passive
devices that are formed on a silicon wafer, such as transistors,
capacitors, resistors, diffused junctions, gate electrodes, local
interconnects, or other structures. The substrate 204 may also
comprise insulating materials (e.g., silicon dioxide, either
undoped or doped with phosphorus or boron and phosphorus; silicon
nitride; silicon oxynitride; or a polymer), and may comprise other
formed materials. The substrate 204 may include CDO material at a
top surface, along with patterned conductors.
[0018] FIG. 3b is a cross sectional side view that illustrates the
substrate 204 after it has been modified to increase the strength
of the interface 208 according to one embodiment. The substrate 204
may be modified by a plasma treatment. In an embodiment, the
substrate 204 may be modified by a PECVD treatment. The substrate
204 may be placed in a plasma chamber for modification as part of a
wafer that comprises a number of substrates 204, prior to
singulation of the wafer. In an embodiment, several wafers, each
with multiple substrates 204 may be placed in the plasma chamber
for modification. In an embodiment, four wafers may be placed in
the plasma chamber for modification. In an embodiment, the wafers
may have a diameter of 300 millimeters.
[0019] The substrate 204 may be brought to a temperature in a range
from about 200 degrees Celsius to about 450 degrees Celsius. In an
embodiment, the substrate 204 may be brought to a temperature of
about 400 degrees Celsius. A flow of hydrogen may be introduced
into the plasma chamber. In some embodiments, the flow of hydrogen
into the plasma chamber may have a flow rate in a range of about
0.1 liter per minute to about 10 liters per minute. In an
embodiment, the flow of hydrogen into the plasma chamber may have a
flow rate of about 1 liter per minute. A flow of helium, ammonia,
and/or nitrogen or another reducing or inert gas may also be
introduced into the plasma chamber. In some embodiments, the
chamber may have a pressure in a range from about 1 Torr to about
10 Torr. In some embodiments, the chamber may have a pressure in a
range from about 2 Torr to about 5 Torr. In an embodiment, the
chamber may have a pressure of about 2.5 Torr. In an embodiment,
the plasma chamber may be ramped up to the pressure from a lower
starting pressure. A radio frequency ("RF") power source may apply
RF power to the plasma chamber to strike a plasma. In some
embodiments with a 300 mm wafer, the radio frequency power source
may apply a power in a range from about 200 Watts to about 1000
Watts. In some embodiments, the radio frequency power source may
apply a power in a range from about 400 Watts to about 600 Watts.
In an embodiment, the radio frequency power source may apply a
power of about 500 Watts. In some embodiments, the power may be
applied for a time in a range from about 4 seconds to about 30
seconds. In some embodiments, the power may be applied for a time
in a range from about 10 seconds to about 15 seconds. In an
embodiment, the power may be applied for about 12 seconds.
[0020] This may result in a hydrogen plasma flowing over CDO
material in the substrate. The hydrogen plasma may remove methyl
groups from CDO within the substrate. In an embodiment, the longer
the hydrogen plasma treatment, the fewer methyl groups remain. FIG.
4 is a chart 400 that illustrates how methyl groups may be removed
by the hydrogen plasma treatment according to one embodiment. As
shown in the chart 400, in an embodiment, the longer the hydrogen
plasma is applied to the substrate 204, the fewer methyl groups
remain in CDO material at the surface of the substrate 204. Removal
of these methyl groups may result in a stronger interface 208
between the substrate 204 and the etch stop layer 206.
[0021] Returning to FIG. 3b, the PECVD modification of the
substrate 204 may result in a graded modified region 302 of the
substrate. The graded modified region 302 may be a region where
methyl groups formerly present in carbon doped oxide material of
the substrate 204 have been removed by the hydrogen plasma
treatment. The graded region 302 may have a depth 304. In an
embodiment, the depth 304 is about 100 angstroms or less. In an
embodiment, the depth 304 is about 50 angstroms or less. In an
embodiment, the region 302 is graded since more methyl groups have
been removed from the carbon doped oxide near the surface of the
substrate 204 and fewer methyl groups have been removed from carbon
doped oxide further from the surface of the substrate 204. Carbon
doped oxide in an unmodified region 306 that begins beneath the
graded modified region 302 at the depth 304 beneath the surface of
the substrate 204 may remain substantially unchanged, with
substantially the same amount of methyl groups as before the plasma
modification. The relatively small depth 304 of the modified graded
region 302 may allow the substrate 204 to retain a low k value that
is relatively unchanged by the modification.
[0022] FIG. 3c is a cross sectional side view that illustrates the
substrate 204 after an etch stop layer 206 has been deposited on
the substrate 204 according to one embodiment. In an embodiment,
the etch stop layer 206 may be deposited on the substrate 204 while
the substrate 204 is in the same plasma chamber in which the graded
modified region 302 was created, and the etch stop layer 206 may be
deposited at the same temperature at which the substrate 204 was
modified to create the graded modified layer 302. The etch stop
layer 206 may comprise a material such as SiN or SiC. There may be
an interface 208 between the etch stop layer 206 and the substrate
204. Modifying the substrate 204 to create the graded modified
layer 302 may cause the interface between the etch stop layer 206
and the substrate 204 to be stronger than it would be otherwise, so
that the etch stop layer 206 may be adhered more strongly to the
substrate 204.
[0023] FIG. 5 is a chart 500 that illustrates how the interface 208
may be strengthened by applying the hydrogen plasma treatment to
the substrate 204 for various times according to one embodiment. As
shown in the chart 500, in an embodiment, treating the substrate
204 by the hydrogen plasma may strengthen the interface 208 between
the substrate 204 and the etch stop layer 206. In an embodiment, up
to an inflection point, the longer the substrate 204 is treated by
the hydrogen plasma, the stronger the interface 208 may be. The
gains achieved by exposing the substrate 204 to the hydrogen plasma
for longer periods may slow so that only minor gains may be
achieved by further exposure, after a certain amount of time.
Excessive exposure length may even start to decrease the interface
208 strength as compared to shorter exposure times.
[0024] FIG. 3d is a cross sectional side view that illustrates the
die 202 after an ILD layer 210 and via 212 have been formed,
according to one embodiment. The ILD layer 210, the via 212, and/or
other structures may be formed using known methods. While an ILD
layer 210 and via 212 are shown in FIG. 3d, other layers and
structures may be formed in addition to, or in place of the ILD
layer 210 and via 212. The layers and structures formed on the
substrate 204, and sections of the etch stop layer 206 removed
during such formation of layers and structures will depend on the
die being fabricated and the use to which it will be put. After the
die 202 has been formed, it may be connected to a package 214 with
a connector 216, as shown in FIG. 2.
[0025] While the foregoing description discusses strengthening an
interface 208 between a substrate 204 and an etch stop layer 206,
other interfaces may also be strengthened. CDO material in a layer,
film, or other form may be treated by hydrogen plasma to remove
methyl groups. An etch stop or diffusion barrier layer, such as
ones that comprise SiN, SiON or SiC may be deposited on the
modified CDO material. The interface between the CDO and etch stop
or diffusion barrier layer may be stronger than if the CDO material
had not been modified. Alternatively, other ILD's with organic
functional groups, such as low k spin on dielectrics or porous CDO
films can be modified in this manner to improve adhesion between
the etch stop layer and ILD layer. In such embodiments, hydrogen
plasma treatment may be used to remove the organic functional
groups from a region near the surface of the material, which may
result in a graded region with fewer organic functional group near
the surface. Finally, this technique could be used to improve the
adhesion between ILD layers for integration schemes where an etch
stop layer 206 is not needed.
[0026] The foregoing description of the embodiments of the
invention has been presented for the purposes of illustration and
description. It is not intended to be exhaustive or to limit the
invention to the precise forms disclosed. This description and the
claims following include terms, such as left, right, over, under,
upper, lower, first, second, etc. that are used for descriptive
purposes only and are not to be construed as limiting. The
embodiments of a device or article described herein can be
manufactured, used, or shipped in a number of positions and
orientations. Persons skilled in the relevant art can appreciate
that many modifications and variations are possible in light of the
above teaching. Persons skilled in the art will recognize various
equivalent combinations and substitutions for various components
shown in the Figures. It is therefore intended that the scope of
the invention be limited not by this detailed description, but
rather by the claims appended hereto.
* * * * *