U.S. patent application number 14/609782 was filed with the patent office on 2016-08-04 for nitridation on hdp oxide before high-k deposition to prevent oxygen ingress.
The applicant listed for this patent is INTERNATIONAL BUSINESS MACHINES CORPORATION. Invention is credited to Takashi Ando, Veeraraghavan S. Basker, Johnathan E. Faltermeier, Hemanth Jagannathan, Tenko Yamashita.
Application Number | 20160225628 14/609782 |
Document ID | / |
Family ID | 56554674 |
Filed Date | 2016-08-04 |
United States Patent
Application |
20160225628 |
Kind Code |
A1 |
Ando; Takashi ; et
al. |
August 4, 2016 |
NITRIDATION ON HDP OXIDE BEFORE HIGH-K DEPOSITION TO PREVENT OXYGEN
INGRESS
Abstract
A method of reducing a migration of oxygen into a high-k
dielectric layer of a semiconducting device is disclosed. An oxide
layer of the semiconducting device is deposited on a substrate. A
chemical composition of a top portion of the oxide layer is
altered. The high-k dielectric layer is deposited on the top
portion of the oxide layer to form the semiconducting device. The
altered chemical composition of the top portion of the oxide layer
reduces migration of oxygen into the high-k dielectric layer.
Inventors: |
Ando; Takashi; (Tuckahoe,
NY) ; Basker; Veeraraghavan S.; (Schenectady, NY)
; Faltermeier; Johnathan E.; (San Jose, CA) ;
Jagannathan; Hemanth; (Guilderland, NY) ; Yamashita;
Tenko; (Schenectady, NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
INTERNATIONAL BUSINESS MACHINES CORPORATION |
Armonk |
NY |
US |
|
|
Family ID: |
56554674 |
Appl. No.: |
14/609782 |
Filed: |
January 30, 2015 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 29/517 20130101;
H01L 21/02225 20130101; H01L 21/022 20130101; H01L 21/02299
20130101; H01L 21/76829 20130101; H01L 21/02296 20130101; H01L
21/02164 20130101; H01L 21/02332 20130101; H01L 21/02227 20130101;
H01L 21/02186 20130101; H01L 29/4966 20130101; H01L 21/28158
20130101; H01L 21/76826 20130101; H01L 29/6656 20130101; H01L
21/28238 20130101; H01L 21/28211 20130101; H01L 29/518 20130101;
H01L 29/66545 20130101 |
International
Class: |
H01L 21/28 20060101
H01L021/28; H01L 21/02 20060101 H01L021/02 |
Claims
1. A method of reducing a migration of oxygen into a high-k
dielectric layer of a semiconducting device, comprising: forming a
first dummy gate and a second dummy gate to define a first gap;
depositing an oxide layer of the semiconducting device on a
substrate in the first gap; altering a chemical composition of a
top portion of the oxide layer; removing the first dummy gate and
the second dummy gate to define a second gap; depositing the high-k
dielectric layer on the top portion of the oxide layer and in the
second gap, wherein the altered chemical composition of the top
portion of the oxide layer reduces migration of oxygen into the
high-k dielectric layer; annealing the semiconducting device,
wherein the top portion of the oxide layer prevents migration of
oxygen from the oxide layer into the high-k dielectric layer during
the annealing; and removing a first segment of the high-k
dielectric layer from the top portion of the oxide layer after the
annealing of the semi-conducting device to dissociate the high-k
dielectric layer from the oxide layer, wherein a second segment of
the high-k dielectric layer lines the second gap to define a gate
lining.
2. The method of claim 1, wherein altering the chemical composition
of the top portion of the oxide layer further comprises diffusing
nitrogen into the top portion of the oxide layer.
3. The method of claim 2, further comprising diffusing the nitrogen
into the top portion by performing at least one of: nitrogen
implantation; annealing under an ammonia (NH.sub.3) ambient; a
plasma treatment with nitrogen in the plasma; and a plasma
treatment with ammonia in the plasma.
4. (canceled)
5. (canceled)
6. (canceled)
7. A method of reducing oxygen migration into a high-k dielectric
layer of a transistor during manufacture of the transistor,
comprising: forming a first dummy gate and a second dummy gate on a
substrate to define a first gap; depositing an oxide layer of the
transistor on the substrate in the first gap; altering a chemical
composition of a top portion of the oxide layer; removing the first
dummy gate and the second dummy gate to define a second gap;
depositing the high-k dielectric layer on the top portion of the
oxide layer and in the second gap, wherein the altered chemical
composition top portion of the oxide layer reduces migration of
oxygen from the oxide layer into the high-k dielectric layer, and
wherein the high-k dielectric layer is deposited onto surfaces of
the substrate within the gap; annealing the transistor, wherein the
top portion of the oxide layer prevents migration of oxygen from
the oxide layer into the high-k dielectric layer during the
annealing; removing a first segment of the high-k dielectric layer
from the top portion of the oxide layer after the annealing of the
transistor to dissociate the high-k dielectric layer from the oxide
layer, wherein a second segment of the high-k dielectric layer
lines the second gap to define a gate lining; depositing a titanium
nitride layer over the high-k dielectric layer; and depositing a
low resistivity metal in the second gap to form the transistor.
8. The method of claim 7, wherein the substrate includes at least
one of a source of the transistor and the drain of the transistor
formed therein.
9. (canceled)
10. The method of claim 7, wherein altering the chemical
composition of the top portion of the oxide layer further comprises
diffusing nitrogen into the top portion of the oxide layer.
11. The method of claim 10, further comprising diffusing the
nitrogen into the top portion of the oxide layer by performing at
least one of: nitrogen implantation; annealing under an ammonia
(NH.sub.3) ambient; a plasma treatment with nitrogen in the plasma;
and a plasma treatment with ammonia in the plasma.
12. (canceled)
13. (canceled)
14. A method of manufacturing a high-k metal gate (HKMG)
transistor, comprising: forming a first dummy gate and a second
dummy gate on a substrate to define a first gap; depositing an
oxide layer on in the first gap; altering a chemical composition of
a top portion of the oxide layer; removing the first dummy gate and
the second dummy gate to define a second gap; depositing a layer of
high-k dielectric layer on the top portion of the oxide material
and in the second gap, wherein the altered chemical composition of
the top portion of the oxide layer reduces migration of oxygen into
the high-k dielectric layer; annealing the HKMG transistor, wherein
the top portion of the oxide layer prevents migration of oxygen
from the oxide layer into the high-k dielectric layer during the
annealing; and removing a first segment of the high-k dielectric
layer from the top portion of the oxide layer after the annealing
of the semi-conducting device to dissociate the high-k dielectric
layer from the oxide layer, wherein a second segment of the high-k
dielectric layer lines the second gap and a portion of the
substrate in the second gap to define a gate lining; depositing a
titanium nitride layer over the high-k dielectric layer; and
depositing a low resistivity metal in the second gap to form the
transistor.
15. (canceled)
16. (canceled)
17. The method of claim 14, wherein altering the chemical
composition of the top portion of the oxide layer further comprises
diffusing nitrogen into the top portion of the oxide layer.
18. The method of claim 17, further comprising diffusing the
nitrogen into the top portion of the oxide layer by performing at
least one of: nitrogen implantation; annealing under an ammonia
(NH.sub.3) ambient; a plasma treatment with nitrogen in the plasma;
and a plasma treatment with ammonia in the plasma.
19. (canceled)
20. (canceled)
Description
BACKGROUND
[0001] The present invention relates generally to methods of
manufacturing a transistor, and more specifically, to a method of
reducing oxygen migration into a high-k dielectric layer of a
transistor during manufacture of the transistor.
[0002] In various high-k metal gate (HKMG) transistors, a source
and a drain are built into a substrate and a gate structure is
built on top of the substrate. The gate structure includes gate
material in a gap between flowable oxide materials built on top of
the substrate. The gap is generally lined with a high-k dielectric
material. However, since the high-k dielectric material is in
contact with the top surfaces of the flowable oxide material during
a manufacturing stage, oxygen molecules can migrate from the
flowable oxide material into the high-k dielectric material. Once
inside the high-k dielectric material, the oxygen can affect the
performance of the resulting HKMG transistor. Therefore, there is a
desire to reduce or prevent migration of oxygen atoms into the
high-k dielectric layer of the gate structure.
SUMMARY
[0003] According to one embodiment of the present invention, a
method of reducing migration of oxygen into a high-k dielectric
layer of a semiconducting device includes: depositing an oxide
layer of the semiconducting device on a substrate; altering a
chemical composition of a top portion of the oxide layer; and
depositing the high-k dielectric layer on the top portion of the
oxide layer to form the semiconducting device, wherein the altered
chemical composition of the top portion of the oxide layer reduces
the migration of oxygen into the high-k dielectric layer.
[0004] According to another embodiment of the present invention, a
method of reducing oxygen migration into a high-k dielectric layer
of a transistor during manufacture of the transistor includes:
depositing an oxide layer of the transistor on a substrate;
altering a chemical composition of a top portion of the oxide
layer; and depositing the high-k dielectric material on the top
portion of the oxide layer, wherein the altered chemical
composition top portion of the oxide layer reduces migration of
oxygen from the oxide layer into the high-k dielectric layer.
[0005] According to another embodiment of the present invention, a
method of manufacturing a high-k metal gate (HKMG) transistor
includes: depositing an oxide layer on a substrate; altering a
chemical composition of a top portion of the oxide material; and
depositing a layer of high-k dielectric material on the top portion
of the oxide material, wherein the altered chemical composition of
the top portion of the oxide layer reduces a migration of oxygen
into the layer.
[0006] Additional features and advantages are realized through the
techniques of the present invention. Other embodiments and aspects
of the invention are described in detail herein and are considered
a part of the claimed invention. For a better understanding of the
invention with the advantages and the features, refer to the
description and to the drawings.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0007] The subject matter which is regarded as the invention is
particularly pointed out and distinctly claimed in the claims at
the conclusion of the specification. The forgoing and other
features, and advantages of the invention are apparent from the
following detailed description taken in conjunction with the
accompanying drawings in which:
[0008] FIG. 1 shows a transistor in one stage of a conventional
high-k metal gate (HKMG) transistor manufacturing process;
[0009] FIGS. 2-9 show various stages of a manufacturing process of
the present invention in which migration of oxygen into the high-k
dielectric layer is reduced, hindered or prevented in a resulting
transistor or semiconducting device, in which:
[0010] FIG. 2 shows a first stage in which various sources and
drains have been formed within a substrate;
[0011] FIG. 3 shows a second stage in which a flowable oxide (FOX)
is deposited in gaps between dummy gates on a substrate;
[0012] FIG. 4 shows a third stage in which nitridation is performed
on the flowable oxide;
[0013] FIG. 5 shows a fourth manufacturing stage in which the thin
nitride layers covering the dummy gates are removed;
[0014] FIG. 6 shows a manufacturing fifth stage in which the dummy
gates are removed;
[0015] FIG. 7 shows a sixth manufacturing stage in which a high-k
dielectric layer is deposited;
[0016] FIG. 8 shows a seventh manufacturing stage in which a
titanium nitride layer is deposited;
[0017] FIG. 9 shows an eighth manufacturing stage in which
amorphous silicon is deposited in the gaps; and
[0018] FIG. 10 shows a flowchart illustrating the method disclosed
herein for manufacturing a transistor with low oxygen concentration
in the high-k dielectric layer.
DETAILED DESCRIPTION
[0019] FIG. 1 shows a transistor 100 in one stage of a conventional
high-k metal gate (HKMG) transistor manufacturing process. The
transistor 100 includes a substrate 102 and a gate structure
includes a first flowable oxide (FOX) layer segment 104 and a
second flowable oxide layer segment 106 deposited on the substrate
102. The first flowable oxide layer segment 104 and second flowable
oxide layer segment 106 are separated by a gap which includes
spacers 108a and 108b. A layer 110 of high-k dielectric material is
deposited. The high-k dielectric layer 110 includes a first segment
110a that covers a top surface of the first flowable oxide layer
segment 104, a second segment 110b that covers a top surface of the
second flowable oxide layer segment 106 and a third segment 110c
that lines the gap between the first flowable oxide layer segment
104 and second flowable oxide layer segment 106. In particular, the
third segment 110c lines surface 112a of spacer 108a, surface 112b
of spacer 108b and surface 112c of substrate 102 in the gap. A
titanium nitride (TiN) layer 114 covers the high-k dielectric layer
110. A gate material 118 (e.g., amorphous silicon) is deposited on
top of the TiN layer 114 in the gap.
[0020] Contact between the first segment 110a and first flowable
oxide layer segment 104 allows free oxygen 116 within first
flowable oxide layer segment 104 to migrate into first segment
110a. Similarly, contact between the second segment 110b and
flowable oxide layer segment 106 allows free oxygen 116 within
second flowable oxide layer segment 106 to migrate into second
segment 110b. The rate of oxygen migration increases during an
annealing process in which temperatures are elevated. Once inside
the high-k dielectric layer 110, the free oxygen 116 diffuses
quickly throughout the high-k dielectric layer 110 via oxygen
vacancy sites. Thus, free oxygen 116 that has migrated into either
the first segment 110a or the second segment 110b generally flows
into the third segment 110c as shown by migration arrows 122. While
the first segment 110a and the second segment 110b are generally
removed via polishing during subsequent stages of the manufacturing
process and are generally not present in the finished transistor,
the third segment 110c remains as a part of the finished transistor
100. The presence of oxygen into the third segment 110c has an
effect of various properties of the finished transistor, such as on
threshold voltage V.sub.t shift.
[0021] FIGS. 2-5 show various stages of a manufacturing process of
the present invention in which migration of oxygen into the high-k
dielectric layer is reduced, hindered or prevented in a resulting
transistor or semiconducting device.
[0022] FIG. 2 shows a first stage 200 in which various sources 204
and drains 206 have been formed within a substrate 202. The
substrate 202 may include a thin silicon fin or a
silicon-on-insulator (SOI) layer. Dummy gates 208 have been formed
on the substrate 202 and spacers 210 have been deposited to cover
the dummy gates 208. An epitaxial formation layer 212 has been
deposited alongside the spacers 210 and a thin nitride layer of
poly open CMP liner (POC liner) 214 has been formed to cover the
spacers 210, epitaxial formation layer 212 and exposed surfaces of
the substrate 202. The dummy gates 208 are separated by gaps
218.
[0023] FIG. 3 shows a second stage 300 in which a flowable oxide
(FOX) 302 is deposited in the gaps 218. In alternate embodiments,
the flowable oxide 302 may be replaced with a high-density plasma
oxide (HDP) material. The flowable oxide 302 is deposited and
polished in the second stage 300.
[0024] FIG. 4 shows a third stage 400 in which nitridation is
performed on the flowable oxide 302. The nitridation process
diffuses nitrogen into a top oxide layer portion 304 of the
flowable oxide 302 thereby changing its chemical composition. The
flowable oxide 302 below the top oxide layer portion 304 is
unaffected by the nitridation process. The nitridation process
includes diffusing nitrogen into the top oxide layer portion 304.
In various embodiments, diffusing the nitrogen may include at least
one of nitrogen implantation into the top oxide layer portion 304,
annealing the oxide material under an ammonia (NH.sub.3) ambient,
performing a plasma treatment on the oxide material with nitrogen
in the plasma, performing a plasma treatment on the oxide material
with ammonia in the plasma, etc. As a result of the nitridation
process, the top oxide layer portion 304 may form stable SiON bonds
that therefore provide a seal that prevents or reduces a flow of
oxygen from the flowable oxide 302 via the top oxide layer portion
304.
[0025] FIG. 5 shows a fourth manufacturing stage 500 in which the
thin nitride layers covering the dummy gates 208 are removed. The
nitride layers may be removed using various methods including, for
example, chemical mechanical polishing techniques. Removing the
nitride cap exposed the top surface of the dummy gates 208.
[0026] FIG. 6 shows a manufacturing fifth stage 600 in which the
dummy gates 208 are removed. Removal of the dummy gates 208 leaves
behind gaps 602. FIG. 7 shows a sixth manufacturing stage 700 in
which a high-k dielectric layer 702 is deposited. Specific examples
of high-k dielectric materials include, but are not limited to:
HfO.sub.2, ZrO.sub.2, La.sub.2O.sub.3, Al.sub.2O.sub.3, TiO.sub.2,
SrTiO.sub.3, LaAlO.sub.3, Y.sub.2O.sub.3, HfO.sub.xN.sub.y,
ZrO.sub.xN.sub.y, La.sub.2O.sub.xN.sub.y, Al.sub.2O.sub.xN.sub.y,
TiO.sub.xN.sub.y, SrTiO.sub.xN.sub.y, LaAlO.sub.xN.sub.y,
Y.sub.2O.sub.xN.sub.y, a silicate thereof, and an alloy thereof.
The high-k dielectric layer 702 covers exposed surfaces including
exposed substrate surfaces in the gaps 602, the sides of the
nitride liner 210 and the top oxide layer portions 304. FIG. 8
shows a seventh manufacturing stage 800 in which a titanium nitride
layer (metal gate portion) 802 is deposited. The titanium nitride
layer 802 covers the high-k dielectric layer 702. FIG. 9 shows an
eighth manufacturing stage 900 in which a low resistivity metal
such as aluminum (Al) or tungsten (W) is deposited in the gaps 602
to complete a gate stack.
[0027] At raised temperatures used in annealing, oxygen is
prevented or inhibited from migrating from the flowable oxide 302
into the high-k dielectric layer 702 due to the presence of the top
oxide layer portion 304. The completed transistor of the present
invention therefore includes a high-k dielectric layer 702 in the
gap 602 that has a reduced amount of oxygen therein in comparison
to a high-k dielectric layer 114 of a transistor 100 (FIG. 1)
manufactured using conventional methods. As a result, various
electrical properties of the transistor of the present invention
are improved, such as a threshold voltage Vt.
[0028] FIG. 10 shows a flowchart 1000 illustrating the method
disclosed herein for manufacturing an HKMG transistor with low
oxygen concentration in the high-k dielectric layer. In Box 1002, a
plurality of flowable oxide layers are formed on a substrate. In
Box 1004, a nitridation process is performed on the flowable oxide
layers to create top oxide layer portions 304 that are resistive to
oxygen flow. In Box 1006, a layer of high-k dielectric material is
deposited on the flowable oxide layers as well as exposed surfaces
in the gap between the flowable oxide layers. In Box 1008, the
transistor is annealed at elevated temperatures. In Box 1010, the
transistor is chemically polished to remove the segments of the
high-k dielectric layer on the top of the flowable oxide layers
302, leaving a high-k dielectric layer in the gap to form the gate
lining.
[0029] The terminology used herein is for the purpose of describing
particular embodiments only and is not intended to be limiting of
the invention. As used herein, the singular forms "a", "an" and
"the" are intended to include the plural forms as well, unless the
context clearly indicates otherwise. It will be further understood
that the terms "comprises" and/or "comprising," when used in this
specification, specify the presence of stated features, integers,
steps, operations, elements, and/or components, but do not preclude
the presence or addition of one more other features, integers,
steps, operations, element components, and/or groups thereof.
[0030] The corresponding structures, materials, acts, and
equivalents of all means or step plus function elements in the
claims below are intended to include any structure, material, or
act for performing the function in combination with other claimed
elements as specifically claimed. The description of the present
invention has been presented for purposes of illustration and
description, but is not intended to be exhaustive or limited to the
invention in the form disclosed. Many modifications and variations
will be apparent to those of ordinary skill in the art without
departing from the scope and spirit of the invention. The
embodiment was chosen and described in order to best explain the
principles of the invention and the practical application, and to
enable others of ordinary skill in the art to understand the
invention for various embodiments with various modifications as are
suited to the particular use contemplated
[0031] The flow diagrams depicted herein are just one example.
There may be many variations to this diagram or the steps (or
operations) described therein without departing from the spirit of
the invention. For instance, the steps may be performed in a
differing order or steps may be added, deleted or modified. All of
these variations are considered a part of the claimed
invention.
[0032] While the preferred embodiment to the invention had been
described, it will be understood that those skilled in the art,
both now and in the future, may make various improvements and
enhancements which fall within the scope of the claims which
follow. These claims should be construed to maintain the proper
protection for the invention first described.
* * * * *