U.S. patent application number 17/459070 was filed with the patent office on 2021-12-16 for surface smoothing of workpieces.
The applicant listed for this patent is Beijing E-Town Semiconductor Technology, Co., LTD, Mattson Technology, Inc.. Invention is credited to Hua Chung, Xinliang Lu, Qi Zhang.
Application Number | 20210391185 17/459070 |
Document ID | / |
Family ID | 1000005808184 |
Filed Date | 2021-12-16 |
United States Patent
Application |
20210391185 |
Kind Code |
A1 |
Zhang; Qi ; et al. |
December 16, 2021 |
Surface Smoothing of Workpieces
Abstract
Apparatus, systems, and methods for processing workpieces are
provided. In one example implementation, a fluorine and oxygen
plasma-based process can be used to smooth a roughened surface of a
silicon and/or a silicon containing structure. The process can
include generating species from a process gas using an inductive
coupling element in a first chamber. The process can include
introducing a fluorine containing gas and an oxygen containing gas
with the species to create a mixture. The process can further
include exposing the silicon and/or the silicon containing
structure to the mixture such that the mixture at least partially
etches a roughened portion to leave a smoother surface of the
silicon and/or the silicon containing structure.
Inventors: |
Zhang; Qi; (San Jose,
CA) ; Lu; Xinliang; (Fremont, CA) ; Chung;
Hua; (Saratoga, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Beijing E-Town Semiconductor Technology, Co., LTD
Mattson Technology, Inc. |
Beijing
Fremont |
CA |
CN
US |
|
|
Family ID: |
1000005808184 |
Appl. No.: |
17/459070 |
Filed: |
August 27, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16718356 |
Dec 18, 2019 |
11107695 |
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17459070 |
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62832055 |
Apr 10, 2019 |
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62783517 |
Dec 21, 2018 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 21/31116 20130101;
H01J 2237/332 20130101; H01J 37/321 20130101; C23C 16/56 20130101;
H01L 21/0206 20130101; H01J 37/3244 20130101; H01J 2237/3341
20130101; H01J 37/32458 20130101; C23C 16/325 20130101; H01L
21/02236 20130101; H01L 21/02126 20130101; H01L 21/02252 20130101;
H01L 29/66795 20130101 |
International
Class: |
H01L 21/311 20060101
H01L021/311; H01L 21/02 20060101 H01L021/02; H01J 37/32 20060101
H01J037/32; C23C 16/32 20060101 C23C016/32; C23C 16/56 20060101
C23C016/56 |
Claims
1.-15. (canceled)
16. A plasma processing apparatus for processing a workpiece,
comprising: a processing chamber having a workpiece support, the
workpiece support configured to support the workpiece during plasma
processing, wherein the workpiece comprises a silicon containing
layer, wherein a surface of the silicon containing layer comprises
a roughened portion; a plasma chamber separated from the processing
chamber by a separation grid; an inductive coupling element
configured to induce a plasma using a process gas in the plasma
chamber; a first gas source injecting a fluorine containing gas; a
second gas source injecting an oxygen containing gas wherein a
mixture generated by mixing the fluorine containing gas and the
oxygen containing gas with species generated in the plasma pass
through the separation grid to at least partially etch the
roughened portion to leave a smoother surface of the silicon
containing layer.
17. The plasma processing apparatus of claim 16, wherein the
roughened portion comprises a concave area and a convex area,
wherein the concave area is thicker than the convex area, the
mixture at least partially etches the concave area more than the
convex area to leave the smoother surface of the silicon containing
layer.
18. The plasma processing apparatus of claim 16, wherein a
concentration of the fluorine containing gas in the oxygen
containing gas is in the range of about 0.1% to about 5%.
19. The plasma processing apparatus of claim 16, wherein the
mixture at least partially oxidizes and at least partially etches
the at least partially roughened portion simultaneously to leave
the smoother surface.
20. The plasma processing apparatus of claim 16, wherein the
smoother surface comprises a material with a formula
SiO.sub.xF.sub.yC.sub.z, wherein x, y and z are positive integers.
Description
PRIORITY CLAIM
[0001] The present application claims the benefit of priority of
U.S. Provisional Application Ser. No. 62/783,517 titled "Surface
Smoothing of Workpieces," filed on Dec. 21, 2018, which is
incorporated herein by reference. The present application claims
the benefit of priority of U.S. Provisional Application Ser. No.
62/832,055, titled "Surface Smoothing of Workpieces," filed on Apr.
10, 2019, which is incorporated herein by reference.
FIELD
[0002] The present disclosure relates generally to semiconductor
processing and more particularly, surface treatment processes for
smoothing a surface of a workpiece.
BACKGROUND
[0003] The processing of semiconductor workpieces can involve the
deposition and removal of different materials layers on a
substrate. Device dimension and materials thickness continue to
decrease in semiconductor processing with shrinking critical
dimensions in semiconductor devices. In advanced device nodes,
materials surface properties, such as roughness, and interface
integrity become increasingly critical to device performance
SUMMARY
[0004] Aspects and advantages of the invention will be set forth in
part in the following description, or may be obvious from the
description, or may be learned through practice of the
invention.
[0005] One example aspect of the present disclosure is directed to
a method for processing a workpiece. The workpiece can include a
silicon containing layer. A surface of the silicon containing layer
can include a roughened portion. The method can include generating
species from a process gas using an inductive coupling element in a
first chamber; providing a fluorine-containing gas and an
oxygen-containing gas into the species to generate a mixture; and
exposing the surface of the silicon containing layer to the mixture
such that the mixture at least partially etches the roughened
portion to leave a smoother surface of the silicon containing
layer.
[0006] Variations and modifications can be made to example
embodiments of the present disclosure.
[0007] These and other features, aspects and advantages of the
present invention will become better understood with reference to
the following description and appended claims. The accompanying
drawings, which are incorporated in and constitute a part of this
specification, illustrate embodiments of the invention and,
together with the description, serve to explain the principles of
the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] Detailed discussion of embodiments directed to one of
ordinary skill in the art are set forth in the specification, which
makes reference to the appended figures, in which:
[0009] FIG. 1 depicts an example surface smoothing process on a
structure according to example embodiments of the present
disclosure;
[0010] FIG. 2 depicts an example surface smoothing process on a
structure according to example embodiments of the present
disclosure;
[0011] FIG. 3 depicts an example surface smoothing process on a
structure according to example embodiments of the present
disclosure;
[0012] FIG. 4 depicts an example plasma processing apparatus
according to example embodiments of the present disclosure;
[0013] FIG. 5 depicts a flow diagram of an example method according
to example embodiments of the present disclosure;
[0014] FIG. 6 depicts a flow diagram of an example method according
to example embodiments of the present disclosure;
[0015] FIG. 7 depicts example introduction of fluorine containing
gas and oxygen containing gas using post-plasma gas injection
according to example embodiments of the present disclosure;
[0016] FIG. 8 depicts an example plasma processing apparatus
according to example embodiments of the present disclosure;
[0017] FIG. 9 depicts an example plasma processing apparatus
according to example embodiments of the present disclosure; and
[0018] FIG. 10 depicts an example surface roughness improvement as
a function of etch amount.
DETAILED DESCRIPTION
[0019] Reference now will be made in detail to embodiments, one or
more examples of which are illustrated in the drawings. Each
example is provided by way of explanation of the embodiments, not
limitation of the present disclosure. In fact, it will be apparent
to those skilled in the art that various modifications and
variations can be made to the embodiments without departing from
the scope or spirit of the present disclosure. For instance,
features illustrated or described as part of one embodiment can be
used with another embodiment to yield a still further embodiment.
Thus, it is intended that aspects of the present disclosure cover
such modifications and variations.
[0020] Example aspects of the present disclosure are directed to
methods for processing a workpiece to at least partially remove a
roughened surface on the workpiece to leave a smoother surface.
Silicon and/or silicon containing structures can sometimes suffer
from increased surface roughness after etching. For instance,
various processes, such as fluorine-containing and/or
oxygen-containing chemistry can be used for etching silicon or
silicon containing materials (e.g., SiGe). However, some etch
processes can leave significant roughness on the materials surface
which can impact interface properties and device performance.
[0021] According to example aspects of the present disclosure, a
fluorine and oxygen plasma-based process can be used to smooth the
roughened surface of the silicon and/or silicon containing
structure. More particularly, a fluorine and oxygen plasma-based
process can be used to detail a soft trim by oxidizing and etching
the surface layer simultaneously to improve surface roughness.
[0022] In some embodiments, the process can include dissociating an
inert gas (e.g., He, Ar, Xe, Ne, etc.) in a plasma chamber (e.g.,
using an inductively coupled plasma source). The process can
include mixing the inert gas with a fluorine-containing gas and an
oxygen-containing gas to form fluorine radicals and oxygen
radicals. The fluorine radicals and the oxygen radicals can be
exposed to the workpiece for smoothing of a silicon and/or
silicon-containing structure or other surface in the workpiece.
[0023] In some embodiments, the fluorine radicals and/or the oxygen
radicals can be generated in the plasma chamber that is separated
from a processing chamber by a separation grid. The workpiece can
be located in the processing chamber. The radicals generated in the
plasma chamber can pass through the separation grid (e.g., as
neutral species) for exposure to the workpiece in the processing
chamber.
[0024] The fluorine radicals and the oxygen radicals can by
generated by inducing a plasma from a process gas in the plasma
chamber using an inductively coupled plasma source. The process gas
can be a mixture comprising a fluorine containing gas, an oxygen
containing gas, and/or a carrier gas. The fluorine containing gas
can be, for instance, tetrafluoromethane (CF.sub.4), nitrogen
trifluoride (NF.sub.3), or a gas with a formula CF.sub.xH.sub.y
(e.g., x and y are positive integers), etc. The oxygen containing
gas can be, for instance, oxygen (O.sub.2), water vapor (H.sub.2O),
or nitrous oxide (N.sub.2O), etc. The carrier gas (also referred to
as an insert gas) can be, for instance, helium (He), argon (Ar),
xenon (Xe), neon (Ne), nitrogen (N.sub.2), etc.
[0025] In some embodiments, the fluorine radicals and/or oxygen
radicals can be generated by injecting fluorine containing gas
and/or oxygen containing gas with species excited by a plasma
source (e.g., excited inert gas species) at a downstream location
of the plasma chamber. For instance, the fluorine containing gas
and/or the oxygen containing gas can be injected at or below the
separation grid using post plasma gas injection.
[0026] One example application of the process according to example
embodiments of the present disclosure can be performed during
direct etching of silicon and/or silicon containing structures. For
instance, an etching process can be implemented using
fluorine-containing, oxygen-containing, and inert gas. The process
can leave a smoother surface with an oxidation layer on top of the
surface. The oxidation layer can be removed, for instance, by a wet
process, e.g., hydrofluoric acid (HF) dip, or removed by a dry etch
process (e.g., plasma based process).
[0027] Another example application can be for surface treatment of
a roughened silicon or silicon containing surface, such as
crystalline silicon, polysilicon, or silicon germanium. The
roughened surface can be induced by a previous etch process or
deposition process (e.g., wet etch process or a dry etch process).
The roughed surface can be treated using a remote plasma (e.g.,
plasma generated in a remote plasma source separated from a
processing chamber by a separation grid). The plasma can be based
on fluorine-containing and/or oxygen-containing gases. The process
can mitigate surface roughness with some material loss.
[0028] In some embodiments, the materials losses and the smoothing
effect using the process(s) according to example embodiments of the
present disclosure can be balanced. For instance, material losses
can be increased to provide a smoother surface. Less material
losses can result in less smoothing effect. As one example, silicon
surface roughness can be reduced by 30% with less silicon loss
relative to achieving a pristine silicon surface with more material
loss.
[0029] In some embodiments, the method can include generating
fluorine (F), oxygen (O), carbon (C) or nitrogen (N) radicals with
some bonds among those species. During reaction of the roughed
surface with those species, there can also be a surface layer
formed with composition (e.g., represented by the formula
SiO.sub.xF.sub.yC.sub.z, where x, y, z are positive integers). On
the rough surface, a concave area may have a thicker formed surface
layer while the convex area has a thinner formed surface layer.
With some process time, the concave area can be etched more
relative to the convex area, making the surface smoother. The
formed surface layer can be easily removed by a wet process like
diluted HF dip and/or removed by a dry etch process. It can also
possible to leave at the surface for the next step if the process
flow allows.
[0030] The above process is an etching process, which removes Si
(amorphous Si, poly Si, crystalline Si or SiGe), as well as a
deposition process, which forms SiO.sub.xF.sub.yC.sub.z layers. The
layer thickness can be closely related to etch amount, so the
roughness improvement comes with a loss of Si materials.
[0031] Adjusting the process condition such as the flow ratio of
the fluorine containing gas, the flow ratio of the oxygen
containing gas, plasma power, process pressure, and/or process
temperature can adjust the ratio between the amount of material
loss and surface smoothness improvement. As a result, the surface
smoothing effect can be enhanced by adjusting those process
parameters.
[0032] In some embodiments, the surface smoothing is done on a
vertical structure, rather than on a planer surface. For instance,
the surface smoothing can be implemented on a Si or SiGe Fin
structure for FINFET devices. Smoothing efficiency (and hence also
the material loss) on some 3D structures need to be same at top and
bottom. These can also be enhanced by adjusting the process
conditions.
[0033] For some applications, the formed surface layer needs to
remain on the surface with high quality. One measure of quality can
be the etch rate vs an etch rate for thermal oxide. To improve the
quality, process parameters such as flow ratio of the fluorine
containing gas, the flow ratio of the oxygen containing gas, plasma
power, process pressure, and/or process temperature can be
tuned.
[0034] Example process parameters for one example implementation
according to example embodiments of the present disclosure are
provided below: [0035] Workpiece Temperature: about 100.degree. C.
to about 600.degree. C., such as about 150.degree. C. to about
300.degree. C.; [0036] Pressure: about 100 mTorr to about 4 Torr;
such as about 400 mTorr to about 800 mTorr; [0037] CF.sub.4
Percentage in O.sub.2: about 0.1% to about 5%, such as 0.1% to
about 1%; [0038] Plasma Source Power: about 100 W to about 3000 W,
such as about 400 W to about 1000 W.
[0039] One example aspect of the present disclosure is directed to
a method for processing a workpiece. The workpiece can include a
silicon containing layer (e.g., crystalline silicon, polysilicon,
silicon germanium, or Fin structure for FINFET devices). A surface
of the silicon containing layer can include one or more roughened
portions. The method can include generating species from a process
gas using an inductive coupling element in a first chamber,
introducing a fluorine containing gas (e.g., tetrafluoromethane
(CF.sub.4), nitrogen trifluoride (NF.sub.3), or a gas with a
formula CF.sub.xH.sub.y, wherein x and y are positive integers) and
an oxygen containing gas (e.g., oxygen (O.sub.2), water vapor
(H.sub.2O), or nitrous oxide (NO.sub.2)) with the species to create
a mixture (e.g., including fluorine radicals and oxygen radicals),
exposing the surface of the silicon containing layer to the mixture
such that the mixture etches the roughened portion to leave a
smoother surface of the silicon containing layer.
[0040] In some embodiments, the roughened portion can include a
concave area and a convex area. The concave area can be thicker
than the convex area. As used herein, a roughened portion refers to
a surface having concave and convex areas, even at a nanometer
scale level. There is no requirement that the surface be
intentionally roughened for a surface to be considered a roughened
surface.
[0041] The mixture can etch the concave area more than the convex
area to leave the smoother surface of the silicon containing layer.
As used herein, a smoother surface results from or is left from a
process (e.g., exposure to a mixture) when a surface roughness of
the surface is reduced relative to prior implementation of the
process.
[0042] In some embodiments, a concentration of the fluorine
containing gas in the oxygen containing gas is in the range of
about 0.1% to about 5%. In some embodiments, the process gas can
include an inert gas (also referred to a carrier gas), e.g., helium
(He), argon (Ar), xenon (Xe), neon (Ne), nitrogen (N.sub.2). In
some embodiments, at least one of the fluorine containing gas and
the oxygen containing gas can be part of the process gas. For
instance, the workpiece can be in a second chamber that is
separated from the first chamber by a separation grid. At least one
of the fluorine containing gas and the oxygen containing gas can be
introduced via a post-plasma gas injection source located at or
below the separation grid. The at least one of the fluorine
containing gas and the oxygen containing gas can be mixed with the
species to create a filtered mixture for exposure to the
workpiece.
[0043] In some embodiments, the mixture can oxidize and etch the
roughened portion simultaneously to leave the smoother surface. In
some embodiments, an oxidation layer can be formed on the smoother
surface of the silicon containing layer. The method can further
include a wet process (e.g., HF dip process) or a dry etch process
to remove the oxidation layer. In some embodiments, the method can
further include a deposition process such that a formed surface
layer with a formula SiO.sub.xF.sub.yC.sub.z where x, y and z are
positive integers remains on the workpiece. In some embodiments,
the formed surface layer can be removed by a wet process or by a
dry chemical etch process.
[0044] One example aspect of the present disclosure is directed to
a plasma processing apparatus for processing a workpiece. The
plasma processing apparatus can include a processing chamber having
a workpiece support. The workpiece support can support the
workpiece during plasma processing. The workpiece can include a
silicon containing layer. A surface of the silicon containing layer
can include one or more roughened portions. The plasma processing
apparatus can further include a plasma chamber separated from the
processing chamber by a separation grid. The plasma processing
apparatus can include an inductive coupling element to induce a
plasma in a process gas in the plasma chamber. The plasma
processing apparatus can include a first gas source injecting a
fluorine containing gas, and a second gas source injecting an
oxygen containing gas. A mixture generated by mixing the fluorine
containing gas and the oxygen containing gas with species generated
in the plasma can pass through the separation grid to etch the one
or more roughened portions to leave a smoother surface of the
silicon containing layer.
[0045] Example aspects of the present disclosure provide a number
of technical effects and benefits. For instance, a fluorine and
oxygen containing plasma (e.g., an inductively coupled plasma
source) can etch one or more roughened portions of a silicon
containing structure layer (e.g., Fin structure for FINFET devices)
to leave a smoother surface of the silicon containing structure
with reduced silicon material loss. As such, a surface roughness of
the silicon containing structure can be improved such that
interface properties and device performance can be improved.
[0046] Aspects of the present disclosure are discussed with
reference to a "workpiece" "wafer" or semiconductor wafer for
purposes of illustration and discussion. Those of ordinary skill in
the art, using the disclosures provided herein, will understand
that the example aspects of the present disclosure can be used in
association with any semiconductor substrate or other suitable
substrate. In addition, the use of the term "about" in conjunction
with a numerical value is intended to refer to within ten percent
(10%) of the stated numerical value. A "pedestal" refers to any
structure that can be used to support a workpiece.
[0047] FIG. 1 depicts an example surface smoothing process on a
structure 50 according to example embodiments of the present
disclosure. The structure 50 is a silicon containing structure
(e.g., a FIN structure, crystalline silicon, polysilicon, or
silicon germanium) with a roughened surface 52. The roughened
surface 52 can include a convex area 54 and a concave area 56.
[0048] An etching process 60A according to example aspects of the
present disclosure can be conducted on the structure 50 to remove
one or more portions of the roughened surface 52. Fluorine
containing gas (e.g., tetrafluoromethane (CF.sub.4), nitrogen
trifluoride (NF.sub.3), or a gas with a formula CF.sub.xH.sub.y,
wherein x and y are positive integers) and oxygen containing gas
(e.g., oxygen (O.sub.2), water vapor (H.sub.2O), or nitrous oxide
(NO.sub.2)) are introduced into the etching process 60A. For
instance, the fluorine containing gas and oxygen containing gas can
be part of a process gas. As another example, at least one of the
fluorine containing gas and the oxygen containing gas can be
introduced via a post-plasma gas injection source. The etching
process 60A removes the roughened surface 52 and leaves a smoother
surface 58. As such, a surface roughness can be improved while
keeping critical dimension 59 loss small.
[0049] In some embodiments (not shown in FIG. 1), the concave area
56 can be thicker than the convex area 54. The etching process 60A
can etch the concave area 55 more than the convex area 54 to leave
the smoother surface 58 of the structure 50.
[0050] FIG. 2 depicts an example surface smoothing process on a
structure 50 according to example embodiments of the present
disclosure. The structure 50 is a silicon containing structure with
a roughened surface 52.
[0051] An oxidation and etching process 60B according to example
aspects of the present disclosure can be conducted on the structure
50 to remove one or more portions of the roughened surface 52.
Fluorine containing gas (e.g., tetrafluoromethane (CF.sub.4),
nitrogen trifluoride (NF.sub.3), or a gas with a formula
CF.sub.xH.sub.y, wherein x and y are positive integers) and oxygen
containing gas (e.g., oxygen (O.sub.2), water vapor (H.sub.2O), or
nitrous oxide (NO.sub.2)) are introduced into the oxidation and
etching process 60B. For instance, the fluorine containing gas and
oxygen containing gas can be part of a process gas. As another
example, at least one of the fluorine containing gas and the oxygen
containing gas can be introduced via a post-plasma gas injection
source. The oxidation and etching process 60B oxidizes and etches
the roughened surface 52 simultaneously to leave a smoother surface
58 with an oxidation layer topmost. Subsequent to the oxidation and
etching process 60B, a wet process or a dry etch process 70 is
conducted on the structure 50 to remove the oxidation layer 62. As
such, a surface roughness can be improved while keeping critical
dimension 59 loss small.
[0052] FIG. 3 depicts an example surface smoothing process on a
structure 50 according to example embodiments of the present
disclosure. The structure 50 is a silicon containing structure with
a roughened surface 52.
[0053] An etching and deposition process 60C according to example
aspects of the present disclosure can be conducted on the structure
50 to remove one or more portions of the roughened surface 52.
Fluorine containing gas (e.g., tetrafluoromethane (CF.sub.4),
nitrogen trifluoride (NF.sub.3), or a gas with a formula
CF.sub.xH.sub.y, wherein x and y are positive integers) and oxygen
containing gas (e.g., oxygen (O.sub.2), water vapor (H.sub.2O), or
nitrous oxide (NO.sub.2)) are introduced into the etching and
deposition process 60C. For instance, the fluorine containing gas
and oxygen containing gas can be part of a process gas. As another
example, at least one of the fluorine containing gas and the oxygen
containing gas can be introduced via a post-plasma gas injection
source. The etching and deposition process 60C etches the roughened
surface 52 and deposits a surface layer 64 with a formula
SiO.sub.xF.sub.yC.sub.z where x, y and z are positive integers to
leave a smoother surface 58. Subsequent to the etching and
deposition process 60C, a wet process or a dry etch process 70 is
conducted on the structure 50 to remove the surface layer 64. As
such, a surface roughness can be improved while keeping critical
dimension loss small.
[0054] FIG. 4 depicts an example plasma processing apparatus
according to example embodiments of the present disclosure. As
illustrated, plasma processing apparatus 100 includes a processing
chamber 110 and a plasma chamber 120 that is separated from the
processing chamber 110. Processing chamber 110 includes a workpiece
support or pedestal 112 operable to support a workpiece 114 to be
processed, such as a semiconductor wafer. In this example
illustration, a plasma is generated in plasma chamber 120 (i.e.,
plasma generation region) by an inductively coupled plasma source
135 and desired species are channeled from the plasma chamber 120
to the surface of workpiece 114 through a separation grid assembly
200.
[0055] Aspects of the present disclosure are discussed with
reference to an inductively coupled plasma source for purposes of
illustration and discussion. Those of ordinary skill in the art,
using the disclosures provided herein, will understand that any
plasma source (e.g., inductively coupled plasma source,
capacitively coupled plasma source, etc.) can be used without
deviating from the scope of the present disclosure.
[0056] The plasma chamber 120 includes a dielectric side wall 122
and a ceiling 124. The dielectric side wall 122, ceiling 124, and
separation grid 200 define a plasma chamber interior 125.
Dielectric side wall 122 can be formed from a dielectric material,
such as quartz and/or alumina. The inductively coupled plasma
source 135 can include an induction coil 130 disposed adjacent the
dielectric side wall 122 about the plasma chamber 120. The
induction coil 130 is coupled to an RF power generator 134 through
a suitable matching network 132. Process gases (e.g., a fluorine
containing gas, an oxygen containing gas, and a carrier gas) can be
provided to the chamber interior from gas supply 150 and annular
gas distribution channel 151 or other suitable gas introduction
mechanism. When the induction coil 130 is energized with RF power
from the RF power generator 134, a plasma can be generated in the
plasma chamber 120. In a particular embodiment, the plasma
processing apparatus 100 can include an optional grounded Faraday
shield 128 to reduce capacitive coupling of the induction coil 130
to the plasma.
[0057] As shown in FIG. 4, a separation grid 200 separates the
plasma chamber 120 from the processing chamber 110. The separation
grid 200 can be used to perform ion filtering from a mixture
generated by plasma in the plasma chamber 120 to generate a
filtered mixture. The filtered mixture can be exposed to the
workpiece 114 in the processing chamber.
[0058] In some embodiments, the separation grid 200 can be a
multi-plate separation grid. For instance, the separation grid 200
can include a first grid plate 210 and a second grid plate 220 that
are spaced apart in parallel relationship to one another. The first
grid plate 210 and the second grid plate 220 can be separated by a
distance.
[0059] The first grid plate 210 can have a first grid pattern
having a plurality of holes. The second grid plate 220 can have a
second grid pattern having a plurality of holes. The first grid
pattern can be the same as or different from the second grid
pattern. Charged particles can recombine on the walls in their path
through the holes of each grid plate 210, 220 in the separation
grid. Neutral species (e.g., radicals) can flow relatively freely
through the holes in the first grid plate 210 and the second grid
plate 220. The size of the holes and thickness of each grid plate
210 and 220 can affect transparency for both charged and neutral
particles.
[0060] In some embodiments, the first grid plate 210 can be made of
metal (e.g., aluminum) or other electrically conductive material
and/or the second grid plate 220 can be made from either an
electrically conductive material or dielectric material (e.g.,
quartz, ceramic, etc.). In some embodiments, the first grid plate
210 and/or the second grid plate 220 can be made of other
materials, such as silicon or silicon carbide. In the event a grid
plate is made of metal or other electrically conductive material,
the grid plate can be grounded. In some embodiments, the grid
assembly can include a single grid with one grid plate.
[0061] As shown in FIG. 4, according to example aspects of the
present disclosure, the apparatus 100 can include a gas delivery
system 150 configured to deliver process gas to the plasma chamber
120, for instance, via gas distribution channel 151 or other
distribution system (e.g., showerhead). The gas delivery system can
include a plurality of feed gas lines 159. The feed gas lines 159
can be controlled using valves and/or mass flow controllers to
deliver a desired amount of gases into the plasma chamber as
process gas. As shown in FIG. 4, the gas delivery system 150 can
include feed gas line(s) for delivery of a fluorine containing gas
(e.g., tetrafluoromethane (CF.sub.4), nitrogen trifluoride
(NF.sub.3), or a gas with a formula CF.sub.xH.sub.y, wherein x and
y are positive integers), feed gas line(s) for delivery of an
oxygen containing gas (e.g., oxygen (O.sub.2), water vapor
(H.sub.2O), or nitrous oxide (NO.sub.2)), and feed gas line(s) for
delivery of an inert gas (e.g., helium (He), argon (Ar), xenon
(Xe), neon (Ne), or nitrogen (N.sub.2)). A control valve and/or
mass flow controller 158 can be used to control a flow rate of each
feed gas line to flow a process gas into the plasma chamber
120.
[0062] FIG. 5 depicts a flow diagram of an example method (500)
according to example embodiments of the present disclosure. The
method (500) will be discussed with reference to the plasma
processing apparatus 100 of FIG. 4 by way of example. The method
(500) can be implemented in any suitable plasma processing
apparatus. FIG. 5 depicts steps performed in a particular order for
purposes of illustration and discussion. Those of ordinary skill in
the art, using the disclosures provided herein, will understand
that various steps of any of the methods described herein can be
omitted, expanded, performed simultaneously, rearranged, and/or
modified in various ways without deviating from the scope of the
present disclosure. In addition, various steps (not illustrated)
can be performed without deviating from the scope of the present
disclosure.
[0063] At (510), the method can include placing a workpiece on a
workpiece support in a processing chamber. For instance, a
workpiece 114 can be placed on a workpiece support 112 in a
processing chamber 110. The workpiece 114 can include a silicon
containing layer having one or more roughened portions. For
instance, a FIN structure 50 includes a roughened surface 52.
[0064] At (520), the method can include generating species from a
process gas using an inductive coupling element in a second
chamber. For instance, a gas delivery system 150 of a plasma
processing apparatus 100 can use the feed gas lines 159 to deliver
a process gas into a plasma chamber 120 to generate the
species.
[0065] At (530), the method can include introducing a fluorine
containing gas and an oxygen containing gas with the species to
create a mixture. In some embodiments, fluorine containing gas
and/or an oxygen containing gas can be introduced as part of the
process gas. For instance, the gas delivery system 150 can use the
feed gas lines 159 to deliver the fluorine containing gas and the
oxygen containing gas into the plasma chamber 120 to create a
mixture (e.g., radicals). In some embodiments, the fluorine
containing gas and/or the oxygen containing gas can be introduced
via a post-plasma gas injection, as further described in FIGS. 6
and 7.
[0066] In some embodiments, a concentration of the fluorine
containing gas relative to the oxygen containing gas is in the
range of about 0.1% to about 5%. For instance, a concentration of
CF.sub.4 relative to O.sub.2 is in a range of about 0.1% to about
5%, such as in a range of about 0.1% to about 1%.
[0067] At (540), the method can include exposing the surface of the
workpiece to the mixture such that the mixture at least partially
etches at least partially roughened portion to leave a smoother
surface of the workpiece. For instance, the workpiece 114 can be
exposed to the species generated in the inductively coupled plasma
to remove one or more roughened portions of the workpiece 114.
[0068] FIG. 6 depicts a flow diagram of an example method (600)
according to example embodiments of the present disclosure. The
method (600) will be discussed with reference to the plasma
processing apparatus 100 of FIG. 4 by way of example. The method
(600) can be implemented in any suitable plasma processing
apparatus. FIG. 6 depicts steps performed in a particular order for
purposes of illustration and discussion. Those of ordinary skill in
the art, using the disclosures provided herein, will understand
that various steps of any of the methods described herein can be
omitted, expanded, performed simultaneously, rearranged, and/or
modified in various ways without deviating from the scope of the
present disclosure. In addition, various steps (not illustrated)
can be performed without deviating from the scope of the present
disclosure.
[0069] At (610), the method can include heating a workpiece in a
processing chamber. For instance, a workpiece 114 can include a
silicon containing layer having one or more roughened portions. For
instance, a FIN structure 50 includes a roughened surface 52. The
workpiece 114 can be heated in a processing chamber 110 to a
process temperature. The workpiece 114 can be heated, for instance,
using one or more heating systems associated with a workpiece
support 112. In some embodiments, the workpiece 114 can be heated
to a process temperature in the range of about 100.degree. C. to
about 600.degree. C., such as about 150.degree. C. to about
300.degree. C.
[0070] At (620), the method can include admitting a process gas
into a plasma chamber. For instance, a process gas can be admitted
into a plasma chamber interior 125 from a gas source 150 via
annular gas distribution channel 151 or other suitable gas
introduction mechanism. In some embodiments, the process gas can be
an inert gas, such as helium, argon, etc. Other process gases can
be used without deviating from the scope of the present
disclosure.
[0071] At (630), the method can include energizing an inductively
coupled plasma source to generate a plasma in a plasma chamber. For
instance, an induction coil 130 can be energized with RF energy
from RF power generator 134 to generate a plasma in the plasma
chamber interior 125.
[0072] At (640), the method can include filtering one or more ions
generated by the plasma using a separation grid to create a
filtered mixture. The filtered mixture can include neutral species
(e.g., excited inert gas molecules). In some embodiments, the one
or more ions can be filtered using a separation grid assembly
separating the plasma chamber from a processing chamber where the
workpiece is located. For instance, the separation grid assembly
200 can be used to filter ions generated by the plasma. The
separation grid 200 can have a plurality of holes. Charged
particles (e.g., ions) can recombine on the walls in their path
through the plurality of holes. Neutral species (e.g. radicals) can
pass through the holes.
[0073] In some embodiments, the separation grid 200 can be
configured to filter ions with an efficiency greater than or equal
to about 90%, such as greater than or equal to about 95%. A
percentage efficiency for ion filtering refers to the amount of
ions removed from the mixture relative to the total number of ions
in the mixture. For instance, an efficiency of about 90% indicates
that about 90% of the ions are removed during filtering. An
efficiency of about 95% indicates that about 95% of the ions are
removed during filtering.
[0074] In some embodiments, the separation grid 200 can be a
multi-plate separation grid. The multi-plate separation grid can
have multiple separation grid plates in parallel. The arrangement
and alignment of holes in the grid plate can be selected to provide
a desired efficiency for ion filtering, such as greater than or
equal to about 95%.
[0075] For instance, the separation grid 200 can have a first grid
plate 210 and a second grid plate 220 in parallel relationship with
one another. The first grid plate 210 can have a first grid pattern
having a plurality of holes. The second grid plate 220 can have a
second grid pattern having a plurality of holes. The first grid
pattern can be the same as or different from the second grid
pattern. Charged particles (e.g., ions) can recombine on the walls
in their path through the holes of each grid plate 210, 220 in the
separation grid 200. Neutral species (e.g., radicals) can flow
relatively freely through the holes in the first grid plate 210 and
the second grid plate 220.
[0076] At (650), the method can include injecting a fluorine
containing gas and an oxygen containing gas into the filtered
mixture to generate radicals for etching one or more roughened
portions of the workpiece. For instance, the fluorine containing
gas and the oxygen containing gas can be injected via a post-plasma
gas injection system that can be located between the first grid
plate 210 and the second grid plate 220 of the separation grid 200.
The fluorine containing gas and/or the oxygen containing gas can be
injected via a post-plasma gas injection system at a location
beneath the separation grid. Example post plasma gas injection is
illustrated in FIG. 7.
[0077] At (660), the method can include exposing the workpiece to
the filtered mixture in the processing chamber. More particularly,
the workpiece 114 can be exposed to radicals generated in the
plasma and passing through the separation grid assembly 200. For
instance, the workpiece 114 can be exposed to radicals generated
using post plasma gas injection to etch one or more roughened
portions of the workpiece to leave a smoother surface of the
workpiece.
[0078] FIG. 7 depicts example introduction of fluorine containing
gas and oxygen containing gas using post-plasma gas injection
according to example embodiments of the present disclosure. The
separation grid 200 includes a first grid plate 210 and a second
grid plate 220 disposed in parallel relationship. The first grid
plate 210 and the second grid plate 220 can provide for ion/UV
filtering.
[0079] The first grid plate 210 can have a first grid pattern
having a plurality of holes. The second grid plate 220 can have a
second grid pattern having a plurality of holes. The first grid
pattern can be the same as or different from the second grid
pattern. Species 215 from the plasma can be exposed to the
separation grid 200. Charged particles (e.g., ions) can recombine
on the walls in their path through the holes of each grid plate
210, 220 in the separation grid 200. Neutral species can flow
relatively freely through the holes in the first grid plate 210 and
the second grid plate 220.
[0080] Subsequent to the second grid plate 220, a gas injection
source 230 can be configured to introduce a fluorine containing gas
and an oxygen containing gas into the species passing through the
separation grid 200. A mixture 225 can pass through a third grid
plate 235 for exposure to the workpiece in the processing
chamber.
[0081] The present example is discussed with reference to a
separation grid with three grid plates for example purposes. Those
of ordinary skill in the art, using the disclosures provided
herein, will understand that more or fewer grid plates can be used
without deviating from the scope of the present disclosure. In
addition, the fluorine containing gas and an oxygen containing gas
can be mixed with the species at any point in the separation grid
and/or after the separation grid in the processing chamber. For
instance, the gas source 230 can be located between first grid
plate 210 and second grid plate 220.
[0082] FIG. 8 depicts an example plasma processing apparatus 800
according to example embodiments of the present disclosure. The
plasma processing apparatus 800 is similar to the plasma processing
apparatus 100 of FIG. 4.
[0083] More particularly, plasma processing apparatus 800 includes
a processing chamber 110 and a plasma chamber 120 that is separated
from the processing chamber 110. Processing chamber 110 includes a
workpiece support or pedestal 112 operable to hold a workpiece 114
to be processed, such as a semiconductor wafer. In this example
illustration, a plasma is generated in plasma chamber 120 (i.e.,
plasma generation region) by an inductively coupled plasma source
135 and desired species are channeled from the plasma chamber 120
to the surface of substrate 114 through a separation grid assembly
200.
[0084] The plasma chamber 120 includes a dielectric side wall 122
and a ceiling 124. The dielectric side wall 122, ceiling 124, and
separation grid 200 define a plasma chamber interior 125.
Dielectric side wall 122 can be formed from a dielectric material,
such as quartz and/or alumina. The inductively coupled plasma
source 135 can include an induction coil 130 disposed adjacent the
dielectric side wall 122 about the plasma chamber 120. The
induction coil 130 is coupled to an RF power generator 134 through
a suitable matching network 132. Process gases (e.g., an inert gas)
can be provided to the chamber interior from gas supply 150 and
annular gas distribution channel 151 or other suitable gas
introduction mechanism. When the induction coil 130 is energized
with RF power from the RF power generator 134, a plasma can be
generated in the plasma chamber 120. In a particular embodiment,
the plasma processing apparatus 100 can include an optional
grounded Faraday shield 128 to reduce capacitive coupling of the
induction coil 130 to the plasma.
[0085] As shown in FIG. 8, a separation grid 200 separates the
plasma chamber 120 from the processing chamber 110. The separation
grid 200 can be used to perform ion filtering from a mixture
generated by plasma in the plasma chamber 120 to generate a
filtered mixture. The filtered mixture can be exposed to the
workpiece 114 in the processing chamber.
[0086] In some embodiments, the separation grid 200 can be a
multi-plate separation grid. For instance, the separation grid 200
can include a first grid plate 210 and a second grid plate 220 that
are spaced apart in parallel relationship to one another. The first
grid plate 210 and the second grid plate 220 can be separated by a
distance.
[0087] The first grid plate 210 can have a first grid pattern
having a plurality of holes. The second grid plate 220 can have a
second grid pattern having a plurality of holes. The first grid
pattern can be the same as or different from the second grid
pattern. Charged particles can recombine on the walls in their path
through the holes of each grid plate 210, 220 in the separation
grid. Neutral species (e.g., radicals) can flow relatively freely
through the holes in the first grid plate 210 and the second grid
plate 220. The size of the holes and thickness of each grid plate
210 and 220 can affect transparency for both charged and neutral
particles.
[0088] In some embodiments, the first grid plate 210 can be made of
metal (e.g., aluminum) or other electrically conductive material
and/or the second grid plate 220 can be made from either an
electrically conductive material or dielectric material (e.g.,
quartz, ceramic, etc.). In some embodiments, the first grid plate
210 and/or the second grid plate 220 can be made of other
materials, such as silicon or silicon carbide. In the event a grid
plate is made of metal or other electrically conductive material,
the grid plate can be grounded.
[0089] The example plasma processing apparatus 800 of FIG. 8 is
operable to generate a first plasma 802 (e.g., a remote plasma) in
the plasma chamber 120 and a second plasma 804 (e.g., a direct
plasma) in the processing chamber 110. The first plasma 802 can be
generated by an inductively coupled plasma source. The second
plasma 804 can be generated by, for instance, a capacitively
coupled plasma source (e.g., bias). As used herein, a "remote
plasma" refers to a plasma generated remotely from a workpiece,
such as in a plasma chamber separated from a workpiece by a
separation grid. As used herein, a "direct plasma" refers to a
plasma that is directly exposed to a workpiece, such as a plasma
generated in a processing chamber having a pedestal operable to
support the workpiece.
[0090] More particularly, the plasma processing apparatus 800 of
FIG. 8 includes a bias source having bias electrode 810 in the
pedestal 112. The bias electrode 810 can be coupled to an RF power
generator 814 via a suitable matching network 812. When the bias
electrode 810 is energized with RF energy, a second plasma 804 can
be generated from a mixture in the processing chamber 110 for
direct exposure to the workpiece 114. The processing chamber 110
can include a gas exhaust port 816 for evacuating a gas from the
processing chamber 110.
[0091] As shown in FIG. 8, according to example aspects of the
present disclosure, the apparatus 100 can include a gas delivery
system 150 configured to deliver process gas to the plasma chamber
120, for instance, via gas distribution channel 151 or other
distribution system (e.g., showerhead). The gas delivery system can
include a plurality of feed gas lines 159. The feed gas lines 159
can be controlled using valves and/or mass flow controllers to
deliver a desired amount of gases into the plasma chamber as
process gas. As shown in FIG. 4, the gas delivery system 150 can
include feed gas line(s) for delivery of a fluorine containing gas
(e.g., tetrafluoromethane (CF.sub.4), nitrogen trifluoride
(NF.sub.3), or a gas with a formula CF.sub.xH.sub.y, wherein x and
y are positive integers), feed gas line(s) for delivery of an
oxygen containing gas (e.g., oxygen (O.sub.2), water vapor
(H.sub.2O), or nitrous oxide (NO.sub.2)), and feed gas line(s) for
delivery of an inert gas (e.g., helium (He), argon (Ar), xenon
(Xe), neon (Ne), or nitrogen (N.sub.2)). A control valve and/or
mass flow controller 158 can be used to control a flow rate of each
feed gas line to flow a process gas into the plasma chamber
120.
[0092] FIG. 9 depicts an example plasma processing apparatus 900
according to example embodiments of the present disclosure. The
plasma processing apparatus 900 is similar to the plasma processing
apparatus 100 of FIG. 4, and the plasma processing apparatus 800 of
FIG. 8.
[0093] More particularly, plasma processing apparatus 900 includes
a processing chamber 110 and a plasma chamber 120 that is separated
from the processing chamber 110. Processing chamber 110 includes a
substrate holder or pedestal 112 operable to hold a workpiece 114
to be processed, such as a semiconductor wafer. In this example
illustration, a plasma is generated in plasma chamber 120 (i.e.,
plasma generation region) by an inductively coupled plasma source
135 and desired species are channeled from the plasma chamber 120
to the surface of substrate 114 through a separation grid assembly
200.
[0094] The plasma chamber 120 includes a dielectric side wall 122
and a ceiling 124. The dielectric side wall 122, ceiling 124, and
separation grid 200 define a plasma chamber interior 125.
Dielectric side wall 122 can be formed from a dielectric material,
such as quartz and/or alumina. The inductively coupled plasma
source 135 can include an induction coil 130 disposed adjacent the
dielectric side wall 122 about the plasma chamber 120. The
induction coil 130 is coupled to an RF power generator 134 through
a suitable matching network 132. Process gas (e.g., an inert gas)
can be provided to the chamber interior from gas supply 150 and
annular gas distribution channel 151 or other suitable gas
introduction mechanism. When the induction coil 130 is energized
with RF power from the RF power generator 134, a plasma can be
generated in the plasma chamber 120. In a particular embodiment,
the plasma processing apparatus 100 can include an optional
grounded Faraday shield 128 to reduce capacitive coupling of the
induction coil 130 to the plasma.
[0095] As shown in FIG. 9, a separation grid 200 separates the
plasma chamber 120 from the processing chamber 110. The separation
grid 200 can be used to perform ion filtering from a mixture
generated by plasma in the plasma chamber 120 to generate a
filtered mixture. The filtered mixture can be exposed to the
workpiece 114 in the processing chamber.
[0096] In some embodiments, the separation grid 200 can be a
multi-plate separation grid. For instance, the separation grid 200
can include a first grid plate 210 and a second grid plate 220 that
are spaced apart in parallel relationship to one another. The first
grid plate 210 and the second grid plate 220 can be separated by a
distance.
[0097] The first grid plate 210 can have a first grid pattern
having a plurality of holes. The second grid plate 220 can have a
second grid pattern having a plurality of holes. The first grid
pattern can be the same as or different from the second grid
pattern. Charged particles can recombine on the walls in their path
through the holes of each grid plate 210, 220 in the separation
grid. Neutral species (e.g., radicals) can flow relatively freely
through the holes in the first grid plate 210 and the second grid
plate 220. The size of the holes and thickness of each grid plate
210 and 220 can affect transparency for both charged and neutral
particles.
[0098] In some embodiments, the first grid plate 210 can be made of
metal (e.g., aluminum) or other electrically conductive material
and/or the second grid plate 220 can be made from either an
electrically conductive material or dielectric material (e.g.,
quartz, ceramic, etc.). In some embodiments, the first grid plate
210 and/or the second grid plate 220 can be made of other
materials, such as silicon or silicon carbide. In the event a grid
plate is made of metal or other electrically conductive material,
the grid plate can be grounded.
[0099] The example plasma processing apparatus 900 of FIG. 9 is
operable to generate a first plasma 902 (e.g., a remote plasma) in
the plasma chamber 120 and a second plasma 904 (e.g., a direct
plasma) in the processing chamber 110. As shown, the plasma
processing apparatus 900 can include an angled dielectric sidewall
922 that extends from the vertical sidewall 122 associated with the
remote plasma chamber 120. The angled dielectric sidewall 922 can
form a part of the processing chamber 110.
[0100] A second inductive plasma source 935 can be located
proximate the dielectric sidewall 922. The second inductive plasma
source 935 can include an induction coil 910 coupled to an RF
generator 914 via a suitable matching network 912. The induction
coil 910, when energized with RF energy, can induce a direct plasma
904 from a mixture in the processing chamber 110. A Faraday shield
928 can be disposed between the induction coil 910 and the sidewall
922.
[0101] The pedestal 112 can be movable in a vertical direction
noted as "V." For instance, the pedestal 112 can include a vertical
lift 916 that can be configured to adjust a distance between the
pedestal 112 and the separation grid assembly 200. As one example,
the pedestal 112 can be located in a first vertical position for
processing using the remote plasma 902. The pedestal 112 can be in
a second vertical position for processing using the direct plasma
904. The first vertical position can be closer to the separation
grid assembly 200 relative to the second vertical position.
[0102] The plasma processing apparatus 900 of FIG. 9 includes a
bias source having bias electrode 810 in the pedestal 112. The bias
electrode 810 can be coupled to an RF power generator 814 via a
suitable matching network 812. The processing chamber 110 can
include a gas exhaust port 816 for evacuating a gas from the
processing chamber 110.
[0103] As shown in FIG. 9, according to example aspects of the
present disclosure, the apparatus 100 can include a gas delivery
system 150 configured to deliver process gas to the plasma chamber
120, for instance, via gas distribution channel 151 or other
distribution system (e.g., showerhead). The gas delivery system can
include a plurality of feed gas lines 159. The feed gas lines 159
can be controlled using valves and/or mass flow controllers to
deliver a desired amount of gases into the plasma chamber as
process gas. As shown in FIG. 4, the gas delivery system 150 can
include feed gas line(s) for delivery of a fluorine containing gas
(e.g., tetrafluoromethane (CF.sub.4), nitrogen trifluoride
(NF.sub.3), or a gas with a formula CF.sub.xH.sub.y, wherein x and
y are positive integers), feed gas line(s) for delivery of an
oxygen containing gas (e.g., oxygen (O.sub.2), water vapor
(H.sub.2O), or nitrous oxide (NO.sub.2)), and feed gas line(s) for
delivery of an inert gas (e.g., helium (He), argon (Ar), xenon
(Xe), neon (Ne), or nitrogen (N.sub.2)). A control valve and/or
mass flow controller 158 can be used to control a flow rate of each
feed gas line to flow a process gas into the plasma chamber
120.
[0104] FIG. 10 depicts an example 1000 surface roughness
improvement 1020 as a function of etch amount 1010. As can be seen
in FIG. 10, there is a correlation between the roughness
improvement 1020 and the etch amount 1010. As the etch amount 1010
increases, the roughness improvement 1020 proportionally increases
with the etch amount 1010 until the roughness improvement 1020
reaches a plateau (e.g., the etch amount 1010 is in a range of
about 30 to about 60).
[0105] While the present subject matter has been described in
detail with respect to specific example embodiments thereof, it
will be appreciated that those skilled in the art, upon attaining
an understanding of the foregoing may readily produce alterations
to, variations of, and equivalents to such embodiments.
Accordingly, the scope of the present disclosure is by way of
example rather than by way of limitation, and the subject
disclosure does not preclude inclusion of such modifications,
variations and/or additions to the present subject matter as would
be readily apparent to one of ordinary skill in the art.
* * * * *