U.S. patent application number 16/010571 was filed with the patent office on 2019-12-19 for semiconductor device with anti-deflection layers.
The applicant listed for this patent is Raytheon Company. Invention is credited to Andrew P. Clarke, George Grama, Michael J. Rondon.
Application Number | 20190385954 16/010571 |
Document ID | / |
Family ID | 66625281 |
Filed Date | 2019-12-19 |
United States Patent
Application |
20190385954 |
Kind Code |
A1 |
Rondon; Michael J. ; et
al. |
December 19, 2019 |
SEMICONDUCTOR DEVICE WITH ANTI-DEFLECTION LAYERS
Abstract
A semiconductor device has a substrate with both compressive and
tensile layers deposited overlying a single major surface (face) of
the device. The tensile layer may be deposited directly on the
substrate of the device, with the compressive layer overlying the
tensile layer. A transition material may be located between the
tensile layer and the compressive layer. The transition material
may be a compound including the components of one or both of the
tensile layer and the compressive layer. In a specific embodiment,
the tensile material may be a silicon nitride, the compressive
layer may be a silicon oxide, and the transition material may be a
silicon oxy-nitride, which may be formed by oxidizing the surface
of the tensile silicon nitride layer. By depositing both tensile
and compressive layers on the same face of the device the opposite
major surface (face) is free for processing.
Inventors: |
Rondon; Michael J.; (Santa
Rosa, CA) ; Clarke; Andrew P.; (Santa Barbara,
CA) ; Grama; George; (Orcutt, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Raytheon Company |
Waltham |
MA |
US |
|
|
Family ID: |
66625281 |
Appl. No.: |
16/010571 |
Filed: |
June 18, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 21/0214 20130101;
H01L 23/3192 20130101; H01L 21/02304 20130101; H01L 21/02266
20130101; H01L 21/0217 20130101; C23C 14/0652 20130101; H01L 23/562
20130101; C23C 14/5853 20130101; H01L 21/02326 20130101; H01L
23/291 20130101; H01L 21/02164 20130101; C23C 14/0036 20130101 |
International
Class: |
H01L 23/00 20060101
H01L023/00; H01L 21/02 20060101 H01L021/02 |
Claims
1. A semiconductor device comprising: a substrate; a tensile layer
overlying a major surface of the substrate; a compressive layer
overlying the major surface; and an intermediate layer between the
tensile layer and the compressive layer, and in contact with both
the tensile layer and the compressive layer; wherein the tensile
layer and the compressive layer both impart forces onto the
substrate, to thereby keep the substrate from bowing.
2. (canceled)
3. The semiconductor device of claim 1, wherein the intermediate
layer is thinner than the compressive layer and the tensile
layer.
4. The semiconductor device of claim 1, wherein the intermediate
layer is an oxidized surface of the compressive layer or the
tensile layer.
5. The semiconductor device of claim 1, wherein the tensile layer
is closer than the compressive layer to the substrate.
6. The semiconductor device of claim 1, wherein the tensile layer
is a silicon nitride layer; and wherein the compressive layer is a
silicon oxide layer.
7. The semiconductor device of claim 6, wherein the intermediate
layer is a silicon oxy-nitride layer.
8. The semiconductor device of claim 1, wherein a tensile force of
the tensile layer balances out a compressive force of the
compressive layer.
9. A method of making a semiconductor device, the method
comprising: depositing a tensile layer overlying a major face of a
substrate of the device; and depositing a compressive layer
overlying the major face; wherein the tensile layer and the
compressive layer both impart forces onto the substrate, to thereby
keep the substrate from bowing; and wherein the depositing of the
tensile layer or the depositing of the compressive layer includes
depositing directly on the major surface of the substrate.
10. The method of claim 9, wherein depositing the tensile layer
occurs before the depositing the compressive layer, with the
compressive layer deposited overlying the tensile layer.
11. The method of claim 9, further comprising forming an
intermediate layer that is between the tensile layer and the
compressive layer, wherein after the depositing of the tensile
layer and the depositing of the compressive layer the intermediate
layer is in contact with both the tensile layer and the compressive
layer.
12. The method of claim 11, wherein the intermediate layer is
formed after the depositing of the tensile layer, and before the
depositing of the compressive layer.
13. The method of claim 12, wherein the intermediate layer is
formed by oxidizing a surface of the tensile layer.
14. The method of claim 9, wherein depositing the tensile layer
includes depositing silicon nitride.
15. The method of claim 14, wherein depositing the silicon nitride
includes depositing the silicon nitride by physical vapor
deposition.
16. The method of claim 14, wherein depositing the silicon nitride
includes columnar deposition of the silicon nitride.
17. The method of claim 14, wherein forming the intermediate layer
includes oxidizing a surface of the silicon nitride, to form
silicon oxy-nitride.
18. The method of claim 17, wherein oxidizing includes exposing the
surface of the silicon nitride to air.
19. The method of claim 17, wherein depositing the compressive
layer includes depositing silicon oxide on the silicon
oxy-nitride.
20. The method of claim 19, wherein depositing the silicon oxide
includes depositing the silicon oxide by physical vapor
deposition.
21. The semiconductor device of claim 1, wherein the tensile layer
or the compressive layer is in contact with the major surface of
the substrate.
22. The semiconductor device of claim 1, wherein the tensile layer,
the intermediate layer, and the compressive layer together form a
neutral deflection layer overlying the substrate and in contact
with the major surface of the substrate.
Description
FIELD OF THE INVENTION
[0001] The invention is in the field of semiconductor devices, with
mechanisms to prevent deflection.
DESCRIPTION OF THE RELATED ART
[0002] In semiconductor devices it is desirable to keep the device
from bowing. One approach to prevent bowing has been to deposit
material on both opposite sides (major surfaces) of a semiconductor
wafer. For example depositing compressive stress material on both
front and back major surfaces balances stresses, preventing bowing.
However it is not always desirable or practical to deposit material
on both major surfaces.
SUMMARY OF THE INVENTION
[0003] A semiconductor device has a neutral deflection dual layer
on a face of a substrate, with a tensile layer and a compressive
layer.
[0004] A semiconductor device has a silicon nitride tensile layer
on a face of a substrate, with a silicon oxide compressive layer on
an oxidized surface of the silicon nitride layer.
[0005] According to an aspect of the invention, a semiconductor
device includes: a substrate; a tensile layer overlying a major
surface of the substrate; and a compressive layer overlying the
major surface. The tensile layer and the compressive layer both
impart forces onto the substrate, to thereby keep the substrate
from bowing.
[0006] According to an embodiment of any paragraph(s) of this
summary, the device includes an intermediate layer between the
tensile layer and the compressive layer.
[0007] According to an embodiment of any paragraph(s) of this
summary, the intermediate layer transmits stresses between the
tensile layer and the compressive layer.
[0008] According to an embodiment of any paragraph(s) of this
summary, the intermediate layer is thinner than the compressive
layer and the tensile layer.
[0009] According to an embodiment of any paragraph(s) of this
summary, the intermediate layer is an oxidized surface of the
compressive layer or the tensile layer.
[0010] According to an embodiment of any paragraph(s) of this
summary, the tensile layer is closer than the compressive layer to
the substrate.
[0011] According to an embodiment of any paragraph(s) of this
summary, the tensile layer is a silicon nitride layer.
[0012] According to an embodiment of any paragraph(s) of this
summary, the compressive layer is a silicon oxide layer.
[0013] According to an embodiment of any paragraph(s) of this
summary, the intermediate layer is a silicon oxy-nitride layer.
[0014] According to an embodiment of any paragraph(s) of this
summary, a tensile force of the tensile layer balances out a
compressive force of the compressive layer.
[0015] According to another aspect of the invention, a method of
making a semiconductor device includes the steps of: depositing a
tensile layer overlying a major face of a substrate of the device;
and depositing a compressive layer overlying the major face. The
tensile layer and the compressive layer both impart forces onto the
substrate, to thereby keep the substrate from bowing.
[0016] According to an embodiment of any paragraph(s) of this
summary, depositing the tensile layer occurs before the depositing
the compressive layer, with the compressive layer deposited
overlying the tensile layer.
[0017] According to an embodiment of any paragraph(s) of this
summary, the method includes forming an intermediate layer that is
between the tensile layer and the compressive layer.
[0018] According to an embodiment of any paragraph(s) of this
summary, the intermediate layer is formed after the depositing of
the tensile layer, and before the depositing of the compressive
layer.
[0019] According to an embodiment of any paragraph(s) of this
summary, the intermediate layer is formed by oxidizing a surface of
the tensile layer.
[0020] According to an embodiment of any paragraph(s) of this
summary, depositing the tensile layer includes depositing silicon
nitride.
[0021] According to an embodiment of any paragraph(s) of this
summary, depositing the silicon nitride includes depositing the
silicon nitride by physical vapor deposition.
[0022] According to an embodiment of any paragraph(s) of this
summary, depositing the silicon nitride includes columnar
deposition of the silicon nitride.
[0023] According to an embodiment of any paragraph(s) of this
summary, forming the intermediate layer includes oxidizing a
surface of the silicon nitride, to form silicon oxy-nitride.
[0024] According to an embodiment of any paragraph(s) of this
summary, oxidizing includes exposing the surface of the silicon
nitride to air.
[0025] According to an embodiment of any paragraph(s) of this
summary, depositing the compressive layer includes depositing
silicon oxide on the silicon oxy-nitride.
[0026] According to an embodiment of any paragraph(s) of this
summary, depositing the silicon oxide includes depositing the
silicon oxide by physical vapor deposition.
[0027] To the accomplishment of the foregoing and related ends, the
invention comprises the features hereinafter fully described and
particularly pointed out in the claims. The following description
and the annexed drawings set forth in detail certain illustrative
embodiments of the invention. These embodiments are indicative,
however, of but a few of the various ways in which the principles
of the invention may be employed. Other objects, advantages and
novel features of the invention will become apparent from the
following detailed description of the invention when considered in
conjunction with the drawings.
BRIEF DESCRIPTION OF DRAWINGS
[0028] The annexed drawings show various aspects of the
invention.
[0029] FIG. 1 is a side cross-sectional view of a semiconductor
device in accordance with an embodiment of the present
invention.
[0030] FIG. 2 is a side cross-sectional view of the semiconductor
device of FIG. 1, with additional components installed.
[0031] FIG. 3 is a high-level flow chart of a method of making a
semiconductor device, according to an embodiment of the
invention.
[0032] FIG. 4 is a side cross-sectional view of a semiconductor
device in accordance with another embodiment of the present
invention.
[0033] FIG. 5 is a side cross-sectional view of a semiconductor
device in accordance with yet another embodiment of the present
invention.
DETAILED DESCRIPTION
[0034] A semiconductor device has a substrate with both compressive
and tensile layers deposited overlying a single major surface
(front face) of the device. The tensile layer may be deposited
directly on the substrate of the device, with the compressive layer
overlying the tensile layer. A transition material (intermediate
layer) may be located between the tensile layer and the compressive
layer. The transition material may be a compound including the
components of one or both of the tensile layer and the compressive
layer. In a specific embodiment, the tensile material may be a
silicon nitride, the compressive layer may be a silicon oxide, and
the transition material may be a silicon oxy-nitride, which may be
formed by oxidizing the surface of the tensile silicon nitride
layer. The materials may be deposited using physical vapor
deposition. Conditions for the vapor deposition may be controlled
to achieve desired growth rates and/or characteristics of the
tensile and compressive layers. By depositing both tensile and
compressive layers on the same face of the device the opposite
major surface (face) is free for processing.
[0035] FIG. 1 shows a semiconductor device 10 that includes a
substrate 12, with a tensile layer 14 overlying a major surface
(front face) 16 of the substrate 12, and a compressive layer 18
overlying both the tensile layer 14 and the front face 16. There
may also be an intermediate layer (or transition layer) 22 between
the tensile layer 14 and the compressive layer 16. As explained in
greater detail below, the intermediate layer 22 transmits stresses
from the compressive layer 18 through to the tensile layer 14 and
the substrate 12. The intermediate layer 22 may be a compound that
includes one or more components also in the tensile layer 14 and/or
the compressive layer 16. Alternatively the intermediate layer 22
may be formed by chemical compounding of a surface of the tensile
layer 14, for example by forming an oxide layer on the surface of
the tensile layer 14.
[0036] The intermediate layer 22 may be used to facilitate
deposition of the compressive layer 18 overlying the tensile layer
14. The intermediate layer 22 may make for a more consistent device
10 in its performance in terms of being able to prevent bowing of
the substrate 12. Toward that end, the intermediate layer 22 may
facilitate consistency in the stresses and/or in the transmission
of stresses from the compressive layer 18 to the tensile layer 14.
However these possibilities are not definitive or exhaustive, and
the intermediate layer 22 may provide different or additional
benefits to the device 10.
[0037] Formation of the tensile layer 14 and the compressive layer
18 both overlying the front face 16 allows operations to be
performed on a back face (major surface) 26 of the substrate 12.
For example it may be possible to reduce thickness of the device 10
as needed by removing material along the back face 26. Or it may be
important to keep the back side 26 available for other purposes,
such as for placement of sensitive devices (components), or for
bonding to other structures for stacking of wafers or semiconductor
devices.
[0038] In one embodiment the tensile layer 14 is a silicon nitride,
the compressive layer 18 is a silicon oxide, and the intermediate
layer 22 is a silicon oxy-nitride. These are only example
materials, and other suitable materials are possible as
alternatives. The layers may be formed with compositions and
thicknesses so as to put a desired stress on the substrate 12, to
keep the substrate 12 from bowing.
[0039] The silicon nitride tensile layer 14 may have a thickness
from 0.1 .mu.m to 1 .mu.m, for example having a thickness of
0.6.+-.0.02 .mu.m. The silicon oxide compressive layer 18 may have
a thickness of less than 1 .mu.m, such as 0.5.+-.0.02 .mu.m. The
silicon oxy-nitride intermediate layer 22 may have a thickness of
about 200 .ANG. (200 Angstroms), such as 200.+-.50 .ANG. (200.+-.50
Angstroms). These values are examples, and should not be construed
as limitations. For example a wide varieties of other layer
thicknesses may be used, such as while maintaining the general
ratios in the thicknesses of the layer. For instance, keeping the
ratio of silicon nitride to silicon oxide thicknesses at 6:5 will
keep the bow close to zero for thin films on the order of 0.1-10
.mu.m.
[0040] As an alternative stoichiometric tantalum nitride and
tantalum may be used, with an intermediate transition layer of
sub-stoichiometric tantalum nitride. The tantalum nitride is
compressive, the tantalum in tensile, and the sub-stoichiometric
tantalum nitride allows the tantalum to grow with tensile stress.
Another alternative possibility is using a bilayer of tantalum
nitride and copper, with an intermediate layer of tantalum
oxy-nitride, which may be created by exposing the tantalum nitride
film to atmosphere to oxidize.
[0041] FIG. 2 shows a view of the device 10 at a later stage in
processing, when electronic components 40 have been placed on the
front face 16, for example engaging conductive traces and/or vias
on the substrate 12. Parts of the layers 14, 18, and 22 may be
removed, such as by selective etching, in order to form or place
the components 40 on the substrate 12. In other embodiments, the
layers 14, 18, and 22 may be deposited onto or around existing
components and structures. It will be appreciated that the layers
14, 18, and 22 may be removed only at certain discrete locations,
leaving the remaining parts of the layers 14, 18, and 22 as
continuous layers that overly large portions of the front face
16.
[0042] It is often desirable for the electronic components 40 to be
electrically isolated from one another. Therefore it is desirable
for the materials used in the layers 14, 18, and 22 to be
dielectrics (electrically insulating). The silicon oxide, silicon
nitride, and silicon oxy-nitride materials used in one embodiment
of the invention satisfy this condition. In addition silicon
nitride has the characteristic of strongly adhering to most
substrates used for electronic devices.
[0043] The device 10 may initially have a wafer for its substrate,
with the wafer being subdivided into individual devices. The
individual devices may be used in any of a wide variety of
products, and may have any of a variety of components, such as
conductive traces, switches, capacitors, etc. Devices such as the
device 10 may be stacked as a part of a larger electronic device,
for 3D wafer stacking, for example.
[0044] With reference now to FIG. 3, steps are shown for a method
100 for producing the device 10 (FIG. 1). The steps shown in FIG. 3
and described below are only a few of the steps used in forming a
final device, with the illustrated steps focused on the process of
preventing bowing or other deflection.
[0045] In step 102 the tensile layer 14 (FIG. 1) is deposited
overlying a major surface (front face) 16 of the substrate 12. The
deposition may be by physical vapor deposition (PVD), which is a
different process than the plasma enhanced chemical vapor
deposition (PECVD) that is usually used for depositing this
material. Advantages for PVD include facilitating cassette wafer
processing, providing a shorter cycle time and higher throughput, a
low material consumption rate, and low contamination risk.
[0046] The PVD process is performed in a sealed chamber, with the
gaseous source materials in a pressure-controlled atmosphere. It
has been found that as the chamber pressure increases the tensile
film stress of the deposited layer (the tensile layer 14 (FIG. 1))
increases, but the deposition rate drops. Thus some sort of balance
needs to be struck between a desirable tensile stress for the
deposited material, and a faster rate of deposition. Additionally
the chamber pressure may be selected so as to yield a deposited
material that has a similar magnitude of stress as the material of
the compressive layer 18 (FIG. 1), so as to minimize (or reduce)
the amount of the tensile material that needs to be deposited. A
smaller amount of deposition is preferable because it makes the
deposition process proceed faster and at lower cost. In addition,
it is possible for deposited silicon nitride to be either
compressive or tensile, depending on how it is deposited. For the
tensile layer 14 of course tensile silicon nitride is desired.
[0047] The chamber pressure for the PVD process in step 102 may be
about 3 mTorr, for example being 3.1.+-.0.1 mTorr, to give
non-limiting example values. The primary source for the chamber
pressure may be an inert gas, such as argon. The flow of nitrogen
gas may be controlled to prevent poisoning, where material on the
target used for deposition accumulates faster than the sputtering
process occurs. Temperature in the chamber may be controlled,
and/or the processing time may be controlled, to prevent damage to
a target for sputtering, and/or to avoid deleterious effects to the
substrate (wafer) 12 and/or to the deposited material.
[0048] Increasing of the pressure in the chamber leads to growth of
silicon nitride in columnar structures, which produces a more
porous and tensile film. The spacing between columnar grains
produces a lower refractive index that the typical stoichiometric
silicon nitride (Si.sub.3N.sub.4), although the porous columnar
form that may be used for the tensile layer 14 may also have the
same stoichiometric silicon nitride.
[0049] It has been found that silicon nitride yields a wafer bow of
-49 .mu.m for every 1 .mu.m of thickness of the tensile layer 14,
to give a single non-limiting example value. The thickness of the
layers 14 and 18 may be selected balance out tension and
compression forces on the substrate 12.
[0050] In step 104 the intermediate layer 22 (FIG. 1) is formed.
The intermediate layer 22 may be formed by oxidizing the top of the
tensile layer 14, for example oxidizing the surface of the silicon
nitride to form oxy-nitride. This may be done by exposing the
silicon nitride to air, for a sufficient time to form oxidize the
top layers of the silicon nitride, to produce the intermediate
layer 22. This forms a film gradient from the silicon nitride
tensile layer 14 to the silicon oxy-nitride of the intermediate
layer 22. This forms a solid base for the subsequent formation of
the silicon oxide compression layer 18.
[0051] Silicon nitride may be oxidized at room temperature and
atmospheric pressure to form a surface layer, such as with a
thickness of 100.+-.50 Angstroms of silicon oxy-nitride. The top
monolayers of silicon nitride oxidize within the first 5-10 minutes
of air exposure.
[0052] The deposition of silicon oxide directly on the silicon
nitride may produce undesirable and/or unpredictable results. The
silicon oxide stress is affected by the surface it grows upon. It
is believed that when silicon oxide is deposited (grown) directly
on silicon nitride, the porous silicon nitride induces columnar
growth in the silicon oxide. This may produce a tensile silicon
oxide, for example having a bow of -33 .mu.m for every 1 .mu.m
deposited, when what is desired is for the silicon oxide to be
compressive, to provide a force on the substrate 12 that
counteracts the tensile force of the underlying layer 14. However
when the silicon nitride surface is oxidized first, the top
oxidized monolayers form a compact film surface that allows the
silicon oxide form to grow densely, producing a compressive film.
For example the silicon oxide may have a wafer bow of +85 .mu.m for
every 1 .mu.m of silicon oxide thickness. This allows formation of
a compressive layer that counteracts the tensile force from the
silicon nitride.
[0053] The above mechanisms are conjectures for the observed
advantageous performance of devices with the intermediate layer 22.
It should be appreciated that the actual mechanisms of material
growth may be different from those described above.
[0054] Finally, in step 106 the compressive layer 18 (FIG. 1) is
deposited overlying the tensile layer 14. More specifically, the
intermediate layer 22 may be used to facilitate deposition of the
compressive layer 18 overlying the tensile layer 14. The
compressive layer 18 may be deposited by a PVD or other suitable
deposition or formation process. When using PVD, compressive films
form at low pressures on the order of 0.1-2 mTorr. For example, to
balance the deflection from a tensile silicon nitride film
deposited at 3 mTorr, a comprehensive silicon dioxide film may be
deposited at 0.6 mTorr. Compressive dielectric films, for example
silicon oxide and silicon nitride, may alternatively be deposited
using electron beam evaporation. Other material sets of compressive
films, typically metals, may be deposited using electroplating.
FIG. 4 shows an alternative arrangement of a semiconductor device
210 that has a compressive layer 218 overlying a front face 216 of
a substrate 212. A tensile layer 214 overlies the compressive layer
218, with an intermediate layer 222 between the layers 214 and 218.
The device 210 may function similarly to the device 10 (FIG. 1)
with regard to resisting bowing or deformation. Certain materials
sets, for example tantalum nitride and copper, allow for the
compressive film to be deposited first (tantalum nitride) and the
tensile film to be deposited on top (copper). In some cases, an
intermediate layer of tantalum may be used between the tantalum
nitride and copper layers to promote copper adhesion.
[0055] FIG. 5 shows another alternative of a semiconductor device
310 that has a tensile layer 314 on a front face 316 of a substrate
312, and a compressive layer 318 is formed directly on the tensile
layer 314. The intervening layer 22 (FIG. 1) is omitted in this
embodiment. Although an intermediate layer has advantages, as
described above, it may be possible to omit the intermediate layer
in some situations, such as with certain materials. As an example,
tensile copper may be deposited directly onto compressive tantalum
nitride to form a balanced film stack. The two films have
complimentary deflections that can cancel out without the aid of an
intermediate film.
[0056] Although the invention has been shown and described with
respect to a certain preferred embodiment or embodiments, it is
obvious that equivalent alterations and modifications will occur to
others skilled in the art upon the reading and understanding of
this specification and the annexed drawings. In particular regard
to the various functions performed by the above described elements
(components, assemblies, devices, compositions, etc.), the terms
(including a reference to a "means") used to describe such elements
are intended to correspond, unless otherwise indicated, to any
element which performs the specified function of the described
element (i.e., that is functionally equivalent), even though not
structurally equivalent to the disclosed structure which performs
the function in the herein illustrated exemplary embodiment or
embodiments of the invention. In addition, while a particular
feature of the invention may have been described above with respect
to only one or more of several illustrated embodiments, such
feature may be combined with one or more other features of the
other embodiments, as may be desired and advantageous for any given
or particular application.
* * * * *