U.S. patent application number 15/163876 was filed with the patent office on 2017-03-09 for microwave probe, plasma monitoring system including the microwave probe, and method for fabricating semiconductor device using the system.
The applicant listed for this patent is Samsung Electronics Co., Ltd.. Invention is credited to Ki-ho Hwang, Woong Ko, Se-jin Oh, Vasily Pashkovskiy, Doug-yong Sung.
Application Number | 20170069553 15/163876 |
Document ID | / |
Family ID | 58189804 |
Filed Date | 2017-03-09 |
United States Patent
Application |
20170069553 |
Kind Code |
A1 |
Oh; Se-jin ; et al. |
March 9, 2017 |
MICROWAVE PROBE, PLASMA MONITORING SYSTEM INCLUDING THE MICROWAVE
PROBE, AND METHOD FOR FABRICATING SEMICONDUCTOR DEVICE USING THE
SYSTEM
Abstract
Disclosed herein are a microwave probe capable of precisely
detecting a plasma state in a plasma process, a plasma monitoring
system including the probe, and a method of fabricating a
semiconductor device using the system. The microwave probe includes
a body extending in one direction and a head which is connected to
one end of the body and has a flat plate shape. In addition, in the
plasma process, the microwave probe is non-invasively coupled to a
chamber such that a surface of the head contacts an outer surface
of a viewport of the chamber, and the microwave probe applies a
microwave into the chamber through the head and receives signals
generated inside the chamber through the head.
Inventors: |
Oh; Se-jin; (Hwaseong-si,
KR) ; Ko; Woong; (Osan-si, KR) ; Pashkovskiy;
Vasily; (Osan-si, KR) ; Sung; Doug-yong;
(Seoul, KR) ; Hwang; Ki-ho; (Seoul, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Samsung Electronics Co., Ltd. |
Suwon-si |
|
KR |
|
|
Family ID: |
58189804 |
Appl. No.: |
15/163876 |
Filed: |
May 25, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01J 37/32935 20130101;
H01R 9/05 20130101; H01L 21/3065 20130101; H01L 21/67253 20130101;
G01N 22/00 20130101; H01L 21/263 20130101; H01J 37/32082 20130101;
H01L 22/26 20130101 |
International
Class: |
H01L 21/66 20060101
H01L021/66; H01L 21/263 20060101 H01L021/263; H01L 21/78 20060101
H01L021/78 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 3, 2015 |
KR |
10-2015-0124942 |
Claims
1. A method of fabricating a semiconductor device, the method
comprising: non-invasively coupling a microwave probe to a viewport
of a chamber for a plasma process; arranging a wafer inside the
chamber; generating plasma by injecting a process gas into the
chamber and applying RF power to the chamber; applying a microwave
into the chamber through the microwave probe, and receiving signals
generated inside the chamber through the microwave probe; and
detecting a resonant frequency among the received signals, and
analyzing a plasma state inside the chamber based on the resonant
frequency, wherein the microwave probe comprises a body and a head
at a first end of the body, and the applying of the microwave and
the receiving of the signals are performed through the head which
contacts an outer surface of the viewport during the non-invasively
coupling the microwave probe to the viewport.
2. The method according to claim 1, wherein the microwave probe
comprises a ground cover surrounding the body and the head, the
ground cover comprising a through-hole in a central portion of a
base of the ground cover, and in the non-invasively coupling of the
microwave probe, an outer rim of the ground cover that extends away
from the base is coupled to a wall of the chamber to be grounded,
and the body extends to the outside of the ground cover through the
through-hole to be electrically connected to a network analyzer
through a connector that is at a second, opposite end of the
body.
3. The method according to claim 1, wherein in the analyzing of the
plasma state, an electron density of the plasma is calculated based
on the resonant frequency.
4. The method according to claim 3, further comprising: comparing
the electron density of the plasma with a pre-set electron density
value; and adjusting process parameters for generating plasma if
the calculated electron density of the plasma is outside of an
allowable range around the pre-set electron density value.
5. The method according to claim 3, further comprising: comparing
the electron density of the plasma in the plasma process for the
wafer with an electron density of plasma in the plasma process for
another wafer arranged inside the chamber; determining if there is
a difference between the electron densities; if it is determined
that there is a difference between the electronic densities,
analyzing a cause of the difference; and controlling the plasma
process based on the analysis.
6. The method according to claim 3, wherein the wafer is a dummy
wafer which is not subjected to an actual plasma process, and
wherein the method comprises determining a time point of
stabilization of the plasma inside the chamber based on the
electron density of the plasma.
7. The method according to claim 3, further comprising determining
a time point of preventive maintenance (PM) based on the electron
density of the plasma.
8. The method according to claim 1, wherein the plasma process
comprises any one of etching, deposition, and diffusion processes
for the wafer, and in the generating of the plasma, the wafer is
subjected to any one of etching, deposition, and diffusion
processes.
9. The method according to claim 1, wherein if the plasma state is
within an allowable range in the analyzing of the plasma state, the
method comprises: performing a subsequent semiconductor process for
the wafer; separating the wafer into individual semiconductor
chips; and packaging the semiconductor chips.
10. A method of fabricating a semiconductor device, the method
comprising: generating plasma by injecting a process gas into a
chamber, in which a wafer is arranged, and by applying RF power to
the chamber; applying a microwave into the chamber and receiving
signals generated inside the chamber, through a microwave probe
non-invasively coupled to a viewport of the chamber, the microwave
probe comprising a body and a head at one end of the body; and
detecting a resonant frequency among the received signals, and
analyzing a plasma state inside the chamber based on the resonant
frequency.
11. The method according to claim 10, wherein the head comprises a
flat plate, and before the generating of the plasma, the microwave
probe is non-invasively coupled to the viewport of the chamber such
that a surface of the head contacts an outer surface of the
viewport.
12. The method according to claim 10, wherein the microwave probe
comprises a ground cover surrounding the body and the head, the
ground cover comprising a base having a through-hole in a central
portion thereof, and before the generating of the plasma, the
microwave probe is non-invasively coupled to the viewport of the
chamber such that an outer rim of the ground cover that extends
away from the base is coupled to a wall of the chamber to be
grounded.
13. The method according to claim 10, wherein in the analyzing of
the plasma state, a network analyzer connected to the microwave
probe detects the resonant frequency, and a computer calculates an
electron density of the plasma based on the resonant frequency.
14. The method according to claim 13, further comprising: comparing
the electron density of the plasma with a pre-set electron density
value; and adjusting process parameters for a subsequent generating
plasma step if the electron density of the plasma is outside of an
allowable range around the pre-set electron density value.
15. The method according to claim 10, wherein the plasma process
comprises any one of etching, deposition, and diffusion processes
for the wafer, and in the generating of the plasma, the wafer is
subjected to any one of etching, deposition, and diffusion
processes.
16. The method according to claim 10, wherein if the plasma state
is within an allowable range in the analyzing of the plasma state,
the method comprises: performing a subsequent semiconductor process
for the wafer; separating the wafer into individual semiconductor
chips; and packaging the semiconductor chips.
17. A method of fabricating a semiconductor device, the method
comprising: non-invasively coupling a microwave probe to a viewport
held in an outer wall of a chamber for a plasma process; generating
plasma by injecting a process gas into the chamber and applying RF
power to the chamber; applying a microwave into the chamber through
the microwave probe; receiving signals generated inside the chamber
through the microwave probe; detecting a resonant frequency among
the received signals; and analyzing a plasma state inside the
chamber based on the resonant frequency including determining an
electron density of the plasma based on the resonant frequency;
wherein the microwave probe comprises a body and a head at a first
end of the body, and the applying of the microwave and the
receiving of the signals are performed through the head which
contacts an outer surface of the viewport during the non-invasively
coupling the microwave probe to the viewport.
18. The method according to claim 17, wherein the microwave probe
further comprises a ground cover comprising a base having a
through-hole defined therein through which the body extends and an
outer sidewall extending outwardly away from an outer periphery of
the base, and wherein the outer sidewall contacts an outer wall of
the chamber during the non-invasively coupling the microwave probe
to the viewport.
19. The method according to claim 18, wherein the microwave probe
further comprises a filter coupled to the outer sidewall and
surrounding the head, wherein the viewport comprises a central
portion and an outer portion surrounding the central portion, and
wherein the head contacts at least a portion of the central portion
of the viewport and the filter covers at least a portion of the
outer portion of the viewport during the non-invasively coupling
the microwave probe to the viewport.
20. The method according to claim 18, wherein the viewport
comprises a channel defined therein, and wherein the body and the
head are received in the channel with the head contacting an end of
the channel during the non-invasively coupling the microwave probe
to the viewport.
21.-36. (canceled)
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of Korean Patent
Application No. 10-2015-0124942, filed on Sep. 3, 2015, the
disclosure of which is incorporated by reference herein in its
entirety.
BACKGROUND
[0002] The inventive concept relates to an apparatus and a method
for fabricating a semiconductor device, and more particularly, to
an apparatus for monitoring a plasma state in a plasma process, and
a method for fabricating a semiconductor device using the
apparatus.
[0003] Plasma is being widely used for processes of manufacturing
semiconductors, plasma display panels (PDPs), liquid crystal
displays (LCDs), solar cells, and the like. Representative plasma
processes include dry etching, plasma enhanced chemical vapor
deposition (PECVD), sputtering, ashing, and the like. Generally,
capacitively coupled plasma (CCP), inductively coupled plasma
(ICP), helicon plasma, microwave plasma, and the like are being
used. It is known that plasma processes are directly associated
with plasma parameters (for example, an electron density, an
electron temperature, an ion flux, and ion energy), and that, in
particular, an electron density is closely related to throughput.
Therefore, a plasma source having a high electron density is being
actively developed.
SUMMARY
[0004] The inventive concept provides a microwave probe capable of
precisely detecting a plasma state in a plasma process, a plasma
monitoring system including the probe, and a method of fabricating
a semiconductor device using the system.
[0005] According to an aspect of the inventive concept, there is
provided a method of fabricating a semiconductor device, which
includes: non-invasively coupling a microwave probe to a viewport
of a chamber for a plasma process; arranging a wafer inside the
chamber; generating plasma by injecting a process gas into the
chamber and applying RF power to the chamber; applying a microwave
into the chamber through the microwave probe, and receiving signals
generated inside the chamber through the microwave probe; and
detecting a resonant frequency among the received signals, and
analyzing a plasma state inside the chamber based on the resonant
frequency, wherein the microwave probe includes a body and a head
at one end of the body, and applies the microwave and receives the
signals through the head contacting an outer surface of the
viewport.
[0006] According to another aspect of the inventive concept, there
is provided a method of fabricating a semiconductor device, which
includes: generating plasma by injecting a process gas into a
chamber in which a wafer is arranged and by applying RF power to
the chamber; applying a microwave into the chamber and receiving
signals generated inside the chamber, through a microwave probe
non-invasively coupled to a viewport of the chamber, the microwave
probe including a body and a head at one end of the body; and
detecting a resonant frequency among the received signals, and
analyzing a plasma state inside the chamber based on the resonant
frequency.
[0007] According to a further aspect of the inventive concept,
there is provided a microwave probe which includes: a body
extending in one direction; and a head which is connected to one
end of the body and has a flat plate structure, wherein in a plasma
process, the microwave probe is configured to be non-invasively
coupled to a chamber such that a surface of the head contacts an
outer surface of a viewport of the chamber, and configured to apply
a microwave into the chamber and to receive signals generated
inside the chamber through the head.
[0008] According to yet another aspect of the inventive concept,
there is provided a plasma monitoring system which includes: a
chamber for a plasma process; an RF power supply for generating
plasma inside the chamber; a microwave probe configured to be
non-invasively coupled to a viewport included in the chamber, the
microwave probe including a body and a head at one end of the body;
and a network analyzer configured to be electrically connected to
the microwave probe.
[0009] According to yet another aspect of the inventive concept,
there is provided a method of fabricating a semiconductor device.
The method includes: non-invasively coupling a microwave probe to a
viewport held in an outer wall of a chamber for a plasma process;
generating plasma by injecting a process gas into the chamber and
applying RF power to the chamber; applying a microwave into the
chamber through the microwave probe; receiving signals generated
inside the chamber through the microwave probe; detecting a
resonant frequency among the received signals; and analyzing a
plasma state inside the chamber based on the resonant frequency
including determining an electron density of the plasma based on
the resonant frequency. The microwave probe includes a body and a
head at a first end of the body, and the applying of the microwave
and the receiving of the signals are performed through the head
which contacts an outer surface of the viewport during the
non-invasively coupling the microwave probe to the viewport.
[0010] According to the inventive concept, in a plasma process, the
microwave probe is non-invasively coupled to the viewport of the
chamber, and thus can be advantageously used for monitoring a
plasma state inside the chamber. For example, since the microwave
probe is non-invasively coupled to an outside of the chamber, the
microwave probe itself does not affect a plasma state inside the
chamber. In addition, using the non-invasive microwave probe, a
microwave is applied, and signals inside the chamber are received,
whereby the plasma state inside the chamber can be accurately
detected and monitored.
[0011] According to the inventive concept, the plasma monitoring
system includes the microwave probe non-invasively coupled to the
viewport of the chamber, whereby the plasma state inside the
chamber can be accurately detected without an influence on the
plasma state inside the chamber. In addition, the plasma monitoring
system precisely monitors whether there is a problem in the plasma
state by calculating an electron density based on the measured
resonant frequency, and controls process conditions of a plasma
process, thereby optimizing the plasma process.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] Example embodiments of the inventive concept will be more
clearly understood from the following detailed description taken in
conjunction with the accompanying drawings in which:
[0013] FIGS. 1A and 1B are a perspective view and a side view of a
microwave probe according to an example embodiment of the inventive
concept;
[0014] FIGS. 2A to 2D are a perspective view, plan views, and a
sectional view of a microwave probe according to an example
embodiment of the inventive concept;
[0015] FIGS. 3A and 3B are a plan view and a sectional view of a
microwave probe according to an example embodiment of the inventive
concept;
[0016] FIGS. 4A and 4B are a perspective view and a plan view of a
microwave probe according to an example embodiment of the inventive
concept;
[0017] FIG. 5 illustrates plan views of various shapes of head
surfaces of microwave probes according to example embodiments of
the inventive concept;
[0018] FIG. 6 illustrates perspective views of various shapes of
bodies of microwave probes according to example embodiments of the
inventive concept;
[0019] FIGS. 7A and 7B are sectional views of microwave probes
according to example embodiments of the inventive concept;
[0020] FIGS. 8A and 8B are a sectional view and a plan view of the
microwave probe of FIG. 2A, which is coupled to a chamber;
[0021] FIGS. 9A and 9B are a sectional view and a plan view of the
microwave probe of FIG. 3A, which is coupled to a chamber;
[0022] FIG. 10 is a plan view of the microwave probe of FIG. 2A,
which is coupled to a chamber;
[0023] FIG. 11 is a conceptual diagram for explaining a method of
detecting a plasma state inside a chamber using a microwave probe
according to an example embodiment of the inventive concept;
[0024] FIGS. 12A and 12B are sectional views of microwave probes
according to example embodiments of the inventive concept, which
are coupled to differently-shaped viewports included in
chambers;
[0025] FIGS. 13A and 13B are graphs depicting reflection
coefficients along with frequencies while a pressure and applied
power inside a chamber are changed, using a microwave probe
according to an example embodiment of the inventive concept;
[0026] FIG. 14 is a graph depicting a correlation between an
oscillation frequency of plasma and an absorption frequency of a
surface wave depending upon a pressure change;
[0027] FIG. 15 is a schematic configuration diagram of a plasma
monitoring system including a microwave probe according to an
example embodiment of the inventive concept;
[0028] FIG. 16 is a graph showing a concept for determining a time
point of stabilization of plasma inside a chamber using a plasma
monitoring system according to an example embodiment of the
inventive concept;
[0029] FIG. 17 is a conceptual diagram for explaining utilization
of a plasma monitoring system according to an example embodiment of
the inventive concept relating to tool matching between
chambers;
[0030] FIG. 18 is a graph showing a concept for determining a time
point of preventive maintenance (PM) of a chamber using a plasma
monitoring system according to an example embodiment of the
inventive concept;
[0031] FIG. 19 is a graph depicting electron densities of plasma
detected using a plasma monitoring system according to an example
embodiment of the inventive concept in plasma processes for a first
wafer and a ninth wafer;
[0032] FIG. 20 is a flow chart illustrating a process of monitoring
a plasma state and controlling a plasma process according to an
example embodiment of the inventive concept; and
[0033] FIG. 21 is a flow chart illustrating a process of
fabricating a semiconductor device through control of a plasma
process according to an example embodiment of the inventive
concept.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0034] Hereinafter, example embodiments of the inventive concept
will be described in detail with reference to the accompanying
drawings. It should be understood that the example embodiments are
provided for complete disclosure and thorough understanding of the
inventive concept by those of ordinary skill in the art, and that
the inventive concept is not limited to the following embodiments
and may be embodied in different ways.
[0035] As used herein, the term "and/or" includes any and all
combinations of one or more of the associated listed items.
Expressions such as "at least one of," when preceding a list of
elements, modify the entire list of elements and do not modify the
individual elements of the list.
[0036] It will be understood that when a component is referred to
as being connected to another component, the component may be
directly connected to the other component, or a third component may
also be interposed therebetween. Similarly, when a component is
referred to as being placed on another component, the component may
be directly placed on the other component, or a third component may
also be interposed therebetween. In the drawings, the sizes or
structures of components may be exaggerated for clarity, and
portions not essential to the description may be omitted for
clarity. Like components will be denoted by like reference numerals
throughout the specification. In addition, the terminology used
herein is only for the purpose of describing specific embodiments
of the inventive concept and is not intended to limit the inventive
concept.
[0037] FIGS. 1A and 1B are a perspective view and a side view of a
microwave probe according to an example embodiment of the inventive
concept.
[0038] Referring to FIGS. 1A and 1B, a microwave probe 100
according to the present example embodiment may include a body 110,
a head 120, and a connector 130.
[0039] The body 110 may include a metal layer 112 and an insulation
covering layer 114 surrounding the metal layer 112. The metal layer
112 may include, for example, a metal having good electrical
conductivity, such as copper (Cu), aluminum (Al), and the like. The
metal layer 112 may be flexible. However, in some cases,
flexibility of the metal layer 112 may be suppressed due to an
increase in hardness or thickness of the metal layer 112. The metal
layer 112 may have a pillar or line shape extending in one
direction. The metal layer 112 may have a thickness of about 1 mm
and a length of a few centimeters. Of course, the thickness and
length of the metal layer 112 are not limited thereto. For
reference, the thickness of the metal layer 112 may refer to a
diameter when the metal layer 112 has a circular pillar shape, and
may refer to a length of a thinner side when the metal layer 112
has a rectangular or quadrangular pillar shape. In some
embodiments, the metal layer 112 is a rod.
[0040] The insulation covering layer 114 may serve to protect the
metal layer 112 and to insulate the metal layer 112 from other
conductive materials external to the metal layer 112. For example,
as shown in FIGS. 2A to 2D, when a microwave probe 100a includes a
conductive ground cover 140, the insulation covering layer 114 may
serve to insulate the metal layer 112 and the ground cover 140 from
each other. The insulation covering layer 114 may include, for
example, cotton, natural rubber, synthetic rubber, a synthetic
resin (or plastic), ceramic, or the like.
[0041] The insulation covering layer 114 may have a cylindrical
tube shape surrounding the metal layer 112. Of course, the shape of
the insulation covering layer 114 is not limited thereto. The body
110 including the insulation covering layer 114 may have a first
thickness T1 of, for example, 10 mm or less. However, the thickness
of the body 110 is not limited thereto. The insulation covering
layer 114 may be flexible in conjunction with the metal layer 112.
Thus, the body 110 as a whole may be flexible. When flexibility of
the metal layer 112 is suppressed, flexibility of the insulation
covering layer 114 may also be suppressed, and thus, the insulation
covering layer 114 may include a high-hardness plastic or
ceramic.
[0042] The body 110 may be formed in the same or similar structure
as cables used for RF signal transfer. For example, the body 110
may include various RF cables such as RG 58, RG 316, RG 400, RG
402, RG 405, SF/SR 085, SF/SR 141, LMR 200 cables, and the like. In
some cases, the insulation covering layer 114 may not be formed in
or on the body 110. In other words, the body 110 may include only
the metal layer 112, and an outer surface of the metal layer 112
may be exposed to the outside of the metal layer 112. Specific
shapes of the body 110 will be described below in more detail with
reference to FIG. 6.
[0043] The head 120 may be coupled to one end of the body 110, and
may have a flat plate structure. For example, the head 120 may have
a circular flat plate structure such as a disk. Of course, the
structure of the head 120 is not limited thereto. The head 120 may
include a metal having good conductivity, such as Cu, Al, and the
like, similar to the metal layer 112. For example, the head 120 of
the microwave probe 100 may include Cu.
[0044] The head 120 may have a different area according to sizes of
a viewport (see the reference numeral 220 in FIGS. 8A and 8B)
mounted on a chamber. For example, when the head 120 is formed in a
circular flat plate structure, the head 120 may have a first
diameter D1 of 75% or 80% or more of a diameter of the viewport.
For example, when the viewport has a diameter of 5 cm, the head 120
may have a first diameter D1 of 4 cm or more. Of course, the area
or diameter of the head 120 is not limited to the numerical values
set forth above. For example, the head 120 may have an area that is
less than an area corresponding to 75% of the diameter of the
viewport, or in some cases, may have an area that is greater than
the area of the viewport. In addition, the head 120 may have a
second thickness T2 of 10 mm or less. However, the thickness of the
head 120 is not limited thereto.
[0045] The head 120 may be electrically connected to the metal
layer of the body 110. The head 120 may apply a microwave, which is
transferred from the outside of the microwave probe 100 through the
metal layer 112, into the chamber (see the reference numeral 200 in
FIG. 11 or 15). In addition, the head 120 may receive signals
generated inside the chamber and transfer the signals to the
outside of the microwave probe 100 through the metal layer 112.
[0046] To improve the functionality of the head 120 for applying a
microwave and/or receiving signals, the head 120 may contact the
viewport of the chamber. For example, when the microwave probe 100
is coupled to the viewport of the chamber in a plasma process, the
microwave probe 100 may be coupled to the viewport such that a
surface of the head 120 contacts an outer surface of the viewport.
In addition, to improve the functionality set forth above, various
patterns may be formed on the surface of the head 120 contacting
the viewport. The structure of the head 120, and the patterns
formed on the surface of the head 120 will be explained below in
more detail in descriptions related to FIG. 5.
[0047] The connector 130 may be coupled to the other, opposite end
of the body 110. The connector 130 may be a connection device for
electrically connecting an external cable or wire (see the
reference numeral 310 in FIG. 8A) outside the microwave probe 100
to the body 110. The connector 130 may be an RF connector
transferring an RF signal such as microwaves and the like. For
example, the connector 130 may include SubMiniature A (SMA),
SubMiniature B (SMB), N type, Bayonet Neil-Concelman (BNC), TNC,
7/16 DIN connectors, and the like. Of course, the connector 130 is
not limited to the connectors set forth above. The external wire
connected to the connector 130 may be an RF cable, for example, an
RG 58, RG 316, RG 400, RG 402, RG 405, SF/SR 085, SF/SR 141, LMR
200 cable, or the like. Of course, the external wire is not limited
to the RF cables set forth above.
[0048] The connector 130 may be omitted from the microwave probe
100 according to the present example embodiment. For example, the
body 110 of the microwave probe 100 may be directly connected to a
network analyzer (see the reference numeral 300 in FIG. 15). That
is, the body 110 may be directly connected to a connector mounted
on the network analyzer. Here, the body 110 may be formed, for
example, in an RF cable structure. The network analyzer may
generate a microwave to transfer the microwave to the outside
thereof, and may receive a signal transferred from the outside
thereof to detect a resonant frequency or the like.
[0049] The microwave probe 100 according to the present example
embodiment may be non-invasively coupled to a viewport (see the
reference numeral 220 in FIG. 15) of a chamber (see the reference
numeral 200 in FIG. 15) in a plasma process. Here, the term
"non-invasively" may mean that the microwave probe 100 is coupled
to an outside of the chamber instead of invading or being inserted
into the chamber. In addition, since the microwave probe 100 does
not invade into the chamber and thus does not contact plasma, the
non-invasive manner may also be referred to as a non-contact
manner.
[0050] The microwave probe 100 may include a structure for coupling
to the chamber. For example, the structure for coupling to the
chamber may be formed on any one of the body 110, the head 120, and
the connector 130. For example, a structure for various mechanical
coupling, such as screw coupling, hook coupling, wedge coupling,
snap coupling, and the like, may be mounted on the microwave probe
100, and a structure corresponding to the above structure may be
mounted on a wall of the chamber, whereby the microwave probe 100
may be coupled to a viewport of the chamber using the coupling
features or manners set forth above. A structure such as a vacuum
sucker may be mounted on the microwave probe 100, whereby the
microwave probe 100 may be coupled to the viewport of the chamber
through a vacuum suction principle. In addition, the microwave
probe 100 may also be coupled to the viewport of the chamber using
an adhesive tape arranged on a surface of the head 120.
[0051] In some cases, the microwave probe 100 may be naturally
coupled to the viewport of the chamber without a separate coupling
means. For example, if the viewport is formed in a circular
recessed structure, the head 120 may be formed to a similar size to
or substantially the same size as the viewport and inserted into
the viewport having the recessed structure, whereby the microwave
probe 100 can be naturally coupled to the viewport of the
chamber.
[0052] The microwave probe 100 according to the present example
embodiment may be non-invasively coupled to the viewport of the
chamber in a plasma process, and thus be used to monitor a plasma
state inside the chamber. More specifically, the microwave probe
100 may be coupled to an outer surface of the viewport mounted on
the chamber in such a manner that the microwave probe 100 contacts
the outer surface of the viewport, whereby the microwave probe 100
can be easily coupled to the chamber without a change in shape of
the viewport. In addition, the microwave probe 100 is
non-invasively coupled to the outside of the chamber, whereby the
microwave probe 100 itself does not affect the plasma state inside
the chamber. Therefore, using the non-invasive microwave probe 100,
a microwave is applied into the chamber, and signals generated
inside the chamber are received, whereby the plasma state inside
the chamber can be accurately detected and monitored. A principle
of detecting and monitoring the plasma state inside the chamber
using the microwave probe 100 will be described below in more
detail with reference to FIG. 11.
[0053] FIG. 2A is a perspective view of a microwave probe according
to an example embodiment of the inventive concept, FIG. 2B is a
plan view of the microwave probe when the microwave probe is viewed
from a head side towards a connector, FIG. 2C is a sectional view
of the microwave probe including the connector, and FIG. 2D is a
plan view of the microwave probe when the microwave probe is viewed
from a connector side towards the head after a body, the head, and
the connector are removed from the microwave probe. In the interest
of brevity, details which have been described above with reference
to FIGS. 1A and 1B may be only briefly described or omitted.
[0054] Referring to FIGS. 2A to 2D, a microwave probe 100a
according to the present example embodiment may differ from the
microwave probe 100 of FIGS. 1A and 1B in that the microwave probe
100a further includes a ground cover 140. Specifically, the
microwave probe 100a according to the present example embodiment
may further include the ground cover 140 surrounding a body 110 and
a head 120.
[0055] As shown in FIGS. 2A to 2D, the ground cover 140 may have a
rectangular frame structure with one side closed such that a rim or
outer sidewall of the ground cover 140 protrudes or extends from a
base of the ground cover 140 to surround the body 110 and the head
120. A through-hole H1 may be formed in a central portion of the
ground cover 140, and the body 110 may extend through the
through-hole H1 to be connected to a connector 130 external to the
ground cover 140. In some cases, the through-hole H1 is formed to
have a larger size in the ground cover 140, and the connector 130
may be inserted into the through-hole H1.
[0056] The rim of the ground cover 140 may be brought into tight
contact with a wall of a chamber (200 in FIG. 15) to be coupled
(e.g., by a fastener such as a screw) to the chamber. Thus, a screw
hole S may be formed in a portion of the ground cover 140. Of
course, in the ground cover 140, a structure for hook coupling,
wedge coupling, snap coupling, or the like may be formed instead of
a structure for screw coupling. As shown in FIG. 8A, when the
ground cover 140 is coupled to a wall 210 of the chamber 200, a
surface of the head 120 may contact an outer surface of a viewport
220 of the chamber 200.
[0057] The ground cover 140 may include a conductive material, for
example, a metal such as Cu, Al, and the like. The overall ground
cover 140 may be a metal, or only a surface of the ground cover 140
may be a metal. The ground cover 140 may maintain a grounded state
in a plasma process. The ground cover 140 alone may be grounded by
directly connecting the ground cover 140 to a ground, and the
ground cover 140 and the wall of the chamber may be grounded
together by coupling the ground cover 140 to the wall of the
chamber connected to a ground.
[0058] The ground cover 140 in a grounded state can block radiation
of plasma light from the viewport of the chamber, and prevent a
noise external to the microwave probe 100a from entering or flowing
into the head 120. Due to the presence of the ground cover 140, a
reception efficiency of the head 120 for signals generated inside
the chamber can be improved. Thus, measurement sensitivity of a
surface wave resonant frequency can be improved. In addition, as
described above, the body 110 includes the insulation covering
layer 114, whereby the external noise can be prevented from
entering or flowing in the metal layer 112. Further, the head 120
may be formed in a thin film disk shape that contacts the viewport
of the chamber, thereby further improving the reception efficiency
of the head 120.
[0059] As a result, the microwave probe 100a according to the
present example embodiment includes the body 110 including the
insulation covering layer 114, the disk-shaped head 120, and the
ground cover 140 which can maintain a grounded state while covering
the body 110 and the head, thereby maximizing a reception
efficiency for signals generated inside the chamber, for example,
measurement sensitivity for a surface wave resonant frequency.
[0060] FIGS. 3A and 3B are a plan view and a sectional view of a
microwave probe according to an example embodiment of the inventive
concept. FIG. 3A is a plan view of the microwave probe when the
microwave probe is viewed from a head side towards a connector. In
the interest of brevity, details which have been described above
with reference to FIGS. 1A to 2D may be only briefly described or
omitted.
[0061] Referring to FIGS. 3A and 3B, a microwave probe 100b
according to the present example embodiment may differ from the
microwave probe 100a of FIG. 2A in that the microwave probe 100b
further includes a filter 150. In addition, a head 120a of the
microwave probe 100b may have an area that is different from the
area of the head 120 of the microwave probe 100a of FIG. 2A.
[0062] In the microwave probe 100b, the head 120a may have a second
diameter D2, and the second diameter D2 may be less than the first
diameter D1 of the head 120 of the microwave probe 100 or 100a of
FIG. 1A or 2A. For example, the second diameter D2 of the head 120a
may range from about 2 cm to about 3 cm. If a viewport (see the
reference numeral 220 in FIG. 15) of a chamber (see the reference
numeral 200 in FIG. 15) has a diameter of about 5 cm, the head 120a
may have a second diameter D2 that is 75% or less of the diameter
of the viewport.
[0063] As such, if the head 120a has a relatively small area, when
the microwave probe 100b is coupled to the chamber, an outer
portion of the viewport may not contact the head 120a and may be
exposed. In a plasma process, plasma light may be radiated through
the exposed portion of the viewport.
[0064] In a plasma process, a plasma state inside the chamber may
be directly confirmed by an eye in some cases. Here, the outer
portion of the viewport, which does not contact the head 120a and
is exposed, may be used to confirm the plasma state. Plasma light
may include ultra-violet (UV) light which can damage eyesight or a
skin. Therefore, a filter to block UV light may be desirable.
[0065] The microwave probe 100b according to the present example
embodiment may include the filter 150, for example, a UV filter
capable of blocking UV light. The filter 150 may have a shape
surrounding an outer portion of the head 120a. Specifically, the
filter 150 may have a circular disk shape in which a central
portion is empty (e.g., a ring shape). The head 120a may be
inserted into the central portion of the filter 150, and thus be
surrounded by the filter 150. For example, the central portion of
the filter 150 may have a circular shape like the head 120a, and
the central open portion may have an area that is almost equal to
or slightly greater than an area of the head 120a.
[0066] As shown in FIGS. 9A and 9B, the filter 150 may have a shape
and a size that are similar to those of the viewport. Thus, the
filter 150 can cover the outer portion of the viewport, which does
not contact the head 120a. In some cases, although the filter 150
may have a smaller size than the viewport, the filter 150 may have
a larger size than a window region (see the reference numeral VPw
in FIG. 9B) of the viewport, through which light passes.
[0067] The filter 150 may be included in or on the microwave probe
100b in a state of being coupled to a ground cover 140 via an
adhesive or the like. In addition, if the viewport is formed in a
circular recessed structure on the chamber, the filter 150 may be
inserted into the recess-structured viewport separately from the
ground cover 140, and when the microwave probe 100b is coupled to
the chamber, the filter 150 may contact the ground cover 140 to be
included in or on the microwave probe 100b.
[0068] The microwave probe 100b according to the present example
embodiment includes the relatively small head 120a and the filter
150 surrounding the head 120a, whereby a plasma state can be
confirmed by an eye through the viewport at an outer side of the
head 120a while signals can be received through the head 120a. In
addition, a UV filter blocking UV light is used as the filter 150,
thereby protecting an eye from UV light. For reference, a window
portion, through which light can penetrate, may be formed in a
portion of the ground cover 140, and a plasma state may be
confirmed using the window portion. In addition, in some cases, a
plasma state may be confirmed while the ground cover 140 is
separated from the microwave probe 100b.
[0069] FIGS. 4A and 4B are a perspective view and a plan view of a
microwave probe according to an example embodiment of the inventive
concept, and FIG. 4B is a plan view of the microwave probe when the
microwave probe is viewed from a head side towards a connector. In
the interest of brevity, details which have been described above
with reference to FIGS. 1A to 2D may be only briefly described or
omitted.
[0070] Referring to FIGS. 4A and 4B, a microwave probe 100c
according to the present example embodiment may differ from the
microwave probe 100a of FIG. 2A in terms of a shape of a ground
cover 140a. For example, in the microwave probe 100c, the ground
cover 140a may have a circular frame structure with one side
closed. In addition, a rim or sidewall of the ground cover 140a may
protrude or extend from a base of the ground cover 140a to surround
a body 110 and a head 120.
[0071] Fastener holes such as screw holes S for screw coupling may
be formed in the rim of the ground cover 140a. Of course, a
structure for hook coupling, wedge coupling, snap coupling, or the
like may be formed in the ground cover 140a instead of a structure
for screw coupling. Generally, since a viewport (220 in FIG. 220)
of a chamber (200 in FIG. 15) has a circular shape in most cases,
the ground cover 140a may be formed in a circular shape to
symmetrically cover the viewport.
[0072] In the microwave probe 100c, the shape of the ground cover
140a is not limited to the circular shape. For example, the ground
cover 140a may have various shapes, such as an ellipse, polygon,
and the like, based on the shape of the viewport.
[0073] FIG. 5 shows plan views of various shapes of head surfaces
of microwave probes according to example embodiments of the
inventive concept. In the interest of brevity, details which have
been described above with reference to FIGS. 1A and 1B may be only
briefly described or omitted.
[0074] Referring to FIG. 5, a head 120 of FIG. 5(a) is a head
having the most fundamental structure. The head 120 may be formed
in a circular flat plate structure, and may not include any pattern
on a surface thereof. For example, patterns such as grooves may not
be formed on the surface of the head 120, which contacts a viewport
(220 in FIG. 8A) of a chamber (200 in FIG. 8A), and the surface of
the head 120 may be maintained in a smooth state.
[0075] A head 120b of FIG. 5(b) may include irregular patterns on a
surface thereof. For example, a large number of grooves 122 having
a straight line or curve shape may be formed on the surface of the
head 120b. The grooves 122 are formed on the surface of the head
120b, such that an efficiency of microwave application and/or
signal reception through the head 120b can be improved.
[0076] A head 120c of FIG. 5(c) may include a spiral pattern on a
surface thereof. For example, a spiral groove 122a may be formed on
the surface of the head 120c. The spiral groove 122a is formed on
the surface of the head 120c, such that an efficiency of microwave
application and/or signal reception through the head 120c can be
improved.
[0077] A head 120d of FIG. 5(d) may include a large number of
concentric circular patterns on a surface thereof. For example, a
large number of concentric circular grooves 122b may be formed on
the surface of the head 120d. The concentric circular grooves 122b
are formed on the surface of the head 120d, such that an efficiency
of microwave application and/or signal reception through the head
120d can be improved.
[0078] Although the straight line or curve-shaped grooves, the
spiral groove, and the concentric circular grooves on the surface
of the head have been described above as examples, shapes of
patterns on the surface of the head are not limited thereto. For
example, to improve microwave application and/or signal reception
efficiencies of the head, patterns having a wide variety of shapes
may be formed on the surface of the head.
[0079] A head 120e of FIG. 5(e) may have an elliptical flat plate
structure, and a head 120f of FIG. 5(f) may have a rectangular flat
plate structure. Of course, the shape or structure of the head is
not limited to the flat plate structures set forth above. For
example, the head may have various shapes such as triangular flat
plates, pentagonal flat plates, and the like.
[0080] In the microwave probe according to the present example
embodiment, the shape of the head may be variously changed in
consideration of a shape of the viewport with which the head is
brought into contact, or improvement in efficiencies of microwave
application and/or signal reception. In addition, in the microwave
probe according to the present example embodiment, the structure of
the head is not limited to flat plates. For example, in some cases,
the head may have a probe shape instead of a flat plate shape. In
the head having a probe shape, instead of separately forming the
head, a portion of an end of the metal layer 112 of the body 110
may act as the head.
[0081] FIG. 6 shows perspective views of various shapes of bodies
of microwave probes according to example embodiments of the
inventive concept. In the interest of brevity, details which have
been described above with reference to FIGS. 1A and 1B may be only
briefly described or omitted.
[0082] Referring to FIG. 6, FIG. 6(a) shows a metal layer 112 of a
body 110, and the metal layer 112 may have a circular pillar or
cylindrical shape extending in one direction. As described above,
the metal layer 112 may include a metal having good conductivity,
for example, Cu, Al, or the like. The metal layer 112 may have a
thickness of about 1 mm and a length of a few centimeters. Of
course, the thickness and the length of the metal layer 112 are not
limited to the numerical values set forth above.
[0083] FIG. 6(b) shows a metal layer 112a having a rectangular or
quadrangular pillar shape, and the metal layer 112a may have a
thickness and a length, which are similar to those of the metal
layer 112 of FIG. 6(a). For reference, the thickness may refer to a
diameter when the metal layer is a circular pillar, and the
thickness may refer to a length of a shorter side when the metal
layer is a rectangular pillar. Although the circular pillar and
quadrangular pillar shapes are illustrated as examples of
structures of the metal layers 112, 112a in FIGS. 6(a) and 6(b),
the structure of the metal layer is not limited thereto. For
example, the metal layer may also be formed in an elliptical pillar
shape or a polygonal pillar shape other than a quadrangular pillar
shape. The metal layer 112 of FIG. 6(a) itself and the metal layer
112a of FIG. 6(b) itself may respectively constitute bodies 110,
110a without insulation covering layers on outer sides thereof.
[0084] FIG. 6(c) shows a structure of a fundamental body 110, and
the body 110 may include an inner metal layer 112 and an outer
insulation covering layer 114. The metal layer 112 may have a
circular pillar shape like the metal layer 112 of FIG. 6(a). Of
course, the metal layer 112 may have a quadrangular pillar shape
like the metal layer 112a of FIG. 6(b), or may have other polygonal
pillar shapes. The insulation covering layer 114 surrounds the
metal layer 112, and includes an insulating material for insulating
the metal layer 112, as described above.
[0085] FIG. 6(d) shows a body 110b having a coaxial cable
structure. The body 110b may include an inner metal layer 112-1, an
inner insulating layer 114-1, an outer metal layer 112-2, and an
outer insulating layer 114-2. The inner metal layer 112-1 and the
outer metal layer 112-2 may constitute a metal layer 112b, and the
inner insulating layer 114-1 and the outer insulating layer 114-2
may constitute an insulation covering layer 114a.
[0086] The coaxial cable structure may be used when a frequency of
a transferred signal is high. More specifically, since the coaxial
cable exhibits low attenuation of a signal at up to a high
frequency, the coaxial cable is suitable for broadband
transmission. In addition, the coaxial cable can exhibit low
leakage or loss of a signal due to the presence of the outer metal
layer 112-2. The inner insulating layer 114-1 may generally include
polyethylene, and may include a circular plate-shaped spacer when
the cable is thick. In addition, when used in the cable for the
purpose of a high temperature, the inner insulating layer 114-1 may
include teflon. Since materials, signal transfer properties, and
the like of the coaxial cable are known in the art, further details
thereof will be omitted herein.
[0087] The bodies of the microwave probes 100, 100a, 100b, 100c
according to the present embodiment may have a coaxial cable
structure like the body 110b of FIG. 6(d). Thus, the bodies of the
microwave probes 100, 100a, 100b, 100c can stably transfer signals
of relatively high frequencies. In addition, an external cable or
wire (see the reference numeral 310 in FIG. 8A) connected to the
connectors (130 in FIG. 1A, and the like) may also be formed in a
coaxial cable structure. Such a coaxial cable structure is mainly
used for an RF cable which transfers RF signals.
[0088] FIGS. 7A and 7B are sectional views of microwave probes
according to example embodiments of the inventive concept. In the
interest of brevity, details which have been described above with
reference to FIGS. 1A to 6 may be only briefly described or
omitted.
[0089] Referring to FIG. 7A, a microwave probe 100d according to
the present example embodiment may differ from the microwave probe
100 of FIG. 1A in terms of a structure of a head 120b. In the
microwave probe 100d, the head 120b may have a considerably smaller
area. For example, a third diameter D3 of the head 120b may be not
more than three times a first thickness T1 of a body 110. In some
cases, the third diameter D3 of the head 120b may be almost or
substantially the same as the first thickness T1 of the body 110.
Furthermore, the third diameter D3 of the head 120b may be almost
or substantially the same as a thickness of a metal layer 112 of
the body 110. When the third diameter D3 of the head 120b is
substantially the same as the thickness of the metal layer 112 of
the body 110, a portion of the metal layer 112 may be used as the
head without separately forming the head, and the head 120b may
have a probe shape.
[0090] When a viewport 220b has a groove or channel in a central
portion thereof, the head 120b of the microwave probe 100d may be
sized to be inserted into and coupled to the groove of the viewport
220b, as shown in FIG. 12A or 12B. In addition, an area of the head
120b may vary with an area of a bottom or end surface of the groove
of the viewport 220b. For example, the area of the head 120b may be
substantially the same as the area of the bottom surface of the
groove of the viewport 220b. Thus, if an area of the groove of the
viewport 220b is similar to an area of the body 110 of the
microwave probe 100d, the head 120b may have almost or
substantially the same diameter as a cross section of the body
110.
[0091] Referring to FIG. 7B, a microwave probe 100e according to
the present example embodiment may differ from the microwave probe
100a of FIG. 2A in terms of a structure of a head 120b. In the
microwave probe 100e, the head 120b may have a considerably smaller
area like the microwave probe 100d of FIG. 7A. When a viewport 220b
has a groove in the central portion thereof, the microwave probe
100e may also provide a structure which can be easily coupled to
the viewport 220b. Specifically, the head 120b may be inserted into
the groove of the viewport 220b, and a ground cover 140 may be
coupled to an outer wall of a chamber through fastener (e.g.,
screw) coupling or the like, such that the microwave probe 100e may
be coupled to the viewport 220b of the chamber.
[0092] FIGS. 8A and 8B are a sectional view and a plan view of the
microwave probe of FIG. 2A, which is coupled to a chamber. FIG. 8B
is the plan view of the microwave probe of FIG. 2A when the
microwave probe of FIG. 2A is viewed from a connector side towards
the head, and the connector, the ground cover, the chamber wall,
and the like are omitted in FIG. 8B for clarity. In the interest of
brevity, details which have been described above with reference to
FIGS. 1A to 7B may be only briefly described or omitted.
[0093] Referring to FIGS. 8A and 8B, the microwave probe 100a
according to the present example embodiment may be coupled to a
viewport 220 of a chamber 200. The chamber 200 may include a wall
210 such as an outer wall for isolating an inside of the chamber
from an outside of the chamber, and may include a through-hole H2
penetrating through the wall 210 in a portion to which the viewport
220 is mounted. The viewport 220 may be coupled to the wall 210 to
cover or fill the through-hole H2. Since the viewport 220 also
serves to isolate the inside of the chamber from the outside of the
chamber, the viewport 220 may be included in the wall of the
chamber.
[0094] Since the viewport 220 includes a material such as quartz
(SiO.sub.2), sapphire (Al.sub.2O.sub.3), or the like, plasma light
inside the chamber may be radiated to the outside of the chamber
through the viewport 220. Thus, the inside of the chamber or plasma
light may be visually observed through the viewport 220, or an
optical apparatus capable of detecting plasma light may be mounted
on the viewport 220, thereby detecting plasma light through the
optical apparatus.
[0095] As shown in FIG. 8B, the viewport 220 may include a window
region VPw corresponding to the through-hole H2 and an outer region
VPo. The window region VPw may be a region through which plasma
light radiated through the through-hole H2 is transmitted, and the
outer region VPo may be a region which is brought into contact with
and coupled to the wall 210 of the chamber 200. In other words, the
first diameter (D1 in FIG. 2C) of the head 120 may be almost the
same as or slightly less than a fourth diameter D4 of the window
region VPw. In some cases, the first diameter D1 of the head 120
may be greater than the fourth diameter D4 of the window region
VPw. As such, the head 120 may be coupled to the viewport 220 to
cover the overall window region VPw, thereby improving signal
transfer properties of the microwave probe 100a. In particular,
since plasma generated inside the chamber 200 is directly
transferred to the window region VPw of the viewport 220 through
the through-hole H2, the head 120 can more accurately detect a
plasma state.
[0096] The ground cover 140 may be coupled to the wall 210 of the
chamber 200 through fastener (e.g., screw) coupling or the like. As
shown in FIG. 8A, an outer surface of the wall 210 of the chamber
200 may be in the same plane as an outer surface of the viewport
220. Thus, the ground cover 140 may be coupled to the chamber 200
to contact both the outer surface of the viewport 220 and the outer
surface of the wall 210 of the chamber 200. In some cases, the
outer surface of the viewport 220 may be closer to the inside of
the chamber 200 than the outer surface of the wall 210 of the
chamber 200. With this structure, the ground cover 140 may be
coupled to the chamber 200 to contact only the wall 210 of the
chamber 200.
[0097] For reference, the wall 210 of the chamber 200 may generally
include a metal material, and may be maintained in a grounded state
to block noises from the outside of the chamber 200 in a plasma
process. An insulating liner 230 may be arranged on an inner side
or surface of the wall 210 of the chamber 200. The insulating liner
230 may protect the wall 210 of the chamber 200 and cover metal
structures protruding from the wall 210, thereby preventing arcing
inside the chamber. The insulating liner 230 may include ceramic,
quartz, or the like. For example, the insulating liner 230 may have
a structure in which yttrium oxide (Y.sub.2O.sub.3) is coated onto
sapphire (Al.sub.2O.sub.3).
[0098] FIGS. 9A and 9B are a sectional view and a plan view of the
microwave probe of FIG. 3A, which is coupled to a chamber. FIG. 9B
is the plan view of the microwave probe of FIG. 3A when the
microwave probe of FIG. 3A is viewed from a connector side towards
the head, and the connector, the ground cover, the chamber wall,
and the like are omitted in FIG. 9B for clarity. In the interest of
brevity, details which have been described above with reference to
FIGS. 1A to 8B may be only briefly described or omitted.
[0099] Referring to FIGS. 9A and 9B, the microwave probe 100b
according to the present example embodiment may also be coupled to
the viewport 220 of the chamber 200. As described above, the head
120a of the microwave probe 100b may be smaller than the head 120
of the microwave probe 100a of FIG. 2A, and the microwave probe
100b may further include the filter 150 outside or around the head
120a. Thus, the microwave probe 100b may be coupled to the viewport
220 of the chamber 200 such that the outer surface of the viewport
220 is covered with the head 120a and the filter 150.
[0100] More specifically, the head 120a may cover a portion of the
window region VPw of the viewport 220, and the filter 150 may cover
another portion of the window region VPw, which is not covered with
the head 120a, and the outer region VPo. In some cases, the filter
150 may have a smaller size in shape than the viewport 220, and
thus may cover only a portion of the outer region VPo or may not
cover the outer region VPo. The filter 150 covers the exposed
window region VPw, which is not covered with the head 120a, and
thus may block UV light and the like among plasma light. Thus, the
outer region VPo, through which plasma light is not transmitted,
may not be covered or entirely covered.
[0101] In the microwave probe 100b, the ground cover 140 may also
be coupled to the wall 210 of the chamber 200 through fastener
(e.g., screw) coupling or the like. As shown in FIG. 9A, the outer
surface of the wall 210 of the chamber 200 may be in the same plane
as an inner surface of the filter 150. Thus, the ground cover 140
may be coupled to the chamber 200 to contact both the inner surface
of the filter 150 and the outer surface of the wall 210 of the
chamber 200. As shown in FIG. 8A, the outer surface of the wall 210
of the chamber 200 may be in the same plane as the outer surface of
the viewport 220. In this structure, the filter 150 may have a
smaller size in external shape (e.g., smaller diameter) than the
viewport 220, and the ground cover 140 may contact both the outer
surface of the viewport 220 and the outer surface of the wall 210
of the chamber 200. In this case, the ground cover 140 may surround
the head 120a and the filter 150.
[0102] FIG. 10 is a plan view of the microwave probe of FIG. 2A,
which is coupled to a chamber, when the microwave probe of FIG. 2A
is viewed from a connector side towards the head, and the
connector, the ground cover, the chamber wall, and the like are
omitted in FIG. 10 for clarity. In the interest of brevity, details
which have been described above with reference to FIGS. 1A to 9B
may be only briefly described or omitted.
[0103] Referring to FIG. 10, the microwave probe 100a according to
the present example embodiment may have the same structure as the
microwave probe 100a of FIG. 8A. However, a viewport 220a to which
the microwave probe 100a is coupled may differ in shape from the
viewport 220 of FIG. 8B. For example, the viewport 220a may have a
rectangular or square structure as shown in FIG. 10. The viewport
220a may include a window region VPw and an outer region VP'o.
Since a shape of the window region VPw corresponds to the shape of
the through-hole (H2 in FIG. 8A), the window region VPw may be
substantially the same as the window region VPw of the viewport 220
of FIG. 8B. However, due to a difference in the shape of the
viewport 220a, the outer region VP'o may differ in shape from the
outer region VPo of the viewport 220 of FIG. 8B.
[0104] As described above, since the outer region VP'o is a region
to which the wall 210 of the chamber 200 is coupled, the selection
of the shape of the outer region VP'o may not have much
consequence. Thus, the viewport 220a is not limited to circular or
rectangular shapes, and may have a polygonal shape other than
elliptical or rectangular shapes, for example.
[0105] FIG. 11 is a conceptual diagram for explaining a method of
detecting a plasma state inside a chamber using a microwave probe
according to an example embodiment of the inventive concept.
[0106] Referring to FIG. 11, a wafer 500 is disposed on an
electrostatic chuck 240 inside the chamber 200, and plasma P is
generated by injecting a process gas and applying RF power into the
chamber, thereby performing a plasma process using the plasma P.
For example, the plasma process may include etching, deposition,
diffusion, surface treatment, novel material synthesis processes,
and the like. The plasma process, particularly a semiconductor
plasma process will be described in more detail in descriptions
related to FIG. 15. The microwave probes according to the example
embodiments of the inventive concept, for example, the microwave
probe 100a of FIG. 2A may be coupled to the viewport 220 of the
chamber 200. In addition, the microwave probe 100a may be connected
to the network analyzer 300 through the external cable or wire 310
connected to the connector (see the reference numeral 130 in FIG.
2A).
[0107] The network analyzer 300 generates a microwave, and
transfers the microwave to the microwave probe 100a through the
external wire 310, thereby applying the microwave into the chamber
200 through the head (120 in FIG. 2A). The network analyzer 300 may
be a commercial network analyzer. Since a resonant frequency of
several hundred mega hertz (MHz) to a few giga hertz (GHz) is
generally observed in a semiconductor plasma process, the network
analyzer 300 can be used for the semiconductor plasma process as
long as the network analyzer 300 can generate a microwave suitable
for those conditions. The microwave may be transferred from a
signal transmission port of the network analyzer 300 to the
microwave probe 100a through the external wire 310.
[0108] The microwave M.sub.in that is input into the chamber 200
resonates at a specific frequency. Resonance may be sensed through
a change in a measured value of a reflection coefficient S11. That
is, as shown in a graph inside the network analyzer 300 at the left
side in FIG. 11, specific peak values of a reflection coefficient
S11 of an applied signal are observed, and frequencies
corresponding to those peak values may be resonant frequencies
f.sub.r. Since frequencies other than a specific resonant frequency
are fully reflected, the reflection coefficient S11 is almost
1.
[0109] Such a resonant frequency may be explained by resonance of a
surface wave, and a resonant frequency of the surface wave is
physically associated with a density of electrons generated in
plasma. Thus, if the resonant frequency is known, the density of
the electron generated in the plasma can be confirmed. A
correlation between the resonant frequency of the surface wave and
the electron density in the plasma can be described as follows.
[0110] First, an oscillation frequency (f.sub.pe) of the plasma can
be represented by Equation (1).
f.sub.pe=1/2.pi.(e.sup.2N.sub.e/.di-elect
cons..sub.0m.sub.e).sup.1/2 Equation (1)
[0111] Here, e is a quantity of electric charge of an electron,
N.sub.e is the number of electrons per unit volume (cm.sup.3), that
is, an electron density, .di-elect cons..sub.0 is a dielectric
constant in vacuum, and m.sub.e is mass of an electron. e,
.di-elect cons..sub.0, and m.sub.e are constants, and if values
thereof are substituted, Equation (1) can be rearranged as Equation
(2).
f.sub.pe (Hz).revreaction.8980(N.sub.e (cm.sup.-3)).sup.1/2
Equation (2)
[0112] The oscillation frequency (f.sub.pe) of the plasma is
proportional to an absorption frequency (f.sub.abs) of the surface
wave, that is, the resonant frequency of the surface wave. In other
words, the oscillation frequency (f.sub.pe) of the plasma and the
absorption frequency (f.sub.abs) of the surface wave may have a
relation of Equation (3).
f.sub.pe.varies.f.sub.abs->f.sub.pe=kf.sub.abs Equation (3)
[0113] Here, a proportional factor k is not a fixed value, but a
value that varies with the viewport, the probe structure,
measurement conditions, and the like. In other words, it is
actually complicated to quantitatively determine the relation
between the oscillation frequency (f.sub.pe) of the plasma and the
resonant frequency of the surface wave. However, the k value is
experimentally and/or statistically determined, and the k value can
then be utilized for the purpose of sensing a qualitative state
change in monitoring for a plasma process.
[0114] Finally, if the resonant frequency of the surface wave, that
is, the absorption frequency (f.sub.abs) of the surface wave is
detected, and the k value is experimentally and/or statistically
determined, the electron density (N.sub.e) of the plasma can be
found by substituting Equation (2), which is an equation relating
to the oscillation frequency (f.sub.pe) of the plasma, into
Equation (3). If a signal of the resonant frequency is actually
measured by the network analyzer 300, the measured resonant
frequency signal is transferred to a computer for analysis, and the
computer finally calculates the electron density of the plasma
using a analysis program. For example, the analysis program may be
a program for calculating the electron density of the plasma using
Equations (1) to (3), the value of the proportional factor k, and
the like. In addition, the value of the proportional factor k may
be experimentally and/or statistically determined based on the
viewport, the probe structure, measurement conditions, and the like
according to a corresponding plasma process. If the electron
density of the plasma is calculated, a density, a state, and the
like of the plasma in the plasma process can be accurately
diagnosed.
[0115] The calculated electron density of the plasma may indicate a
plasma state in the vicinity of the viewport 220 inside the chamber
200. In other words, the resonant frequency may be detected during
the plasma process using the microwave probe 100a and the network
analyzer 300, thereby sensing a plasma state in the vicinity of the
wall (see reference numeral 210 in FIG. 8A) of the chamber 200, on
which the viewport 220 is mounted, in real time. Finally, in the
plasma process, the microwave probe 100a according to the present
example embodiment can contribute to optimizing the plasma process
by monitoring whether there is a problem in the plasma state in
real time.
[0116] For reference, in an existing method of monitoring a plasma
process, a probe is directly inserted into a chamber in an invasive
manner. Such direct insertion of the probe cause process gases in
use and generated reaction species to directly contact a surface of
the probe during the plasma process, and thus has an influence on a
situation of the plasma process. Thus, a distorted situation of the
plasma process is monitored instead of an ideal situation thereof
due to the invasive probe. In conclusion, the method of monitoring
the plasma process by directly inserting the probe into the chamber
is not suitable for industrial enterprises, and is limited to use
for advanced research and development in university institutes, and
the like.
[0117] On the other hand, each of the microwave probes 100, 100a to
100e according to the example embodiments of the inventive concept
is non-invasively coupled to the viewport 220 of the chamber 200,
thereby not affecting the plasma state inside the chamber 200. In
addition, each of the microwave probes 100, 100a to 100e may
include the body 110 including the insulation covering layer 114,
and the disk-shaped head 120, thereby optimizing microwave
application and/or a measurement sensitivity to signals generated
inside the chamber. Further, each of the microwave probes 100, 100a
to 100e may include the ground cover 140 which can maintain a
grounded state while covering the body 110 and the head 120,
thereby maximizing the measurement sensitivity to the signals by
maximizing a signal-to-noise ratio (SNR).
[0118] FIGS. 12A and 12B are sectional views of microwave probes
according to example embodiments of the inventive concept, which
are coupled to differently-shaped viewports included in chambers.
In the interest of brevity, details which have been described above
with reference to FIGS. 1A to 10 may be only briefly described or
omitted.
[0119] Referring to FIG. 12A, a microwave probe 100e according to
the present example embodiment may be substantially the same as the
microwave probe 100e of FIG. 7B. Thus, the microwave probe 100e may
include the body 110, the head 120b, the connector 130, and the
ground cover 140, and the head 120 may have a relatively small
area. For example, the third diameter (D3 in FIG. 7A) of the head
120b may be not more than three times the first thickness (T1 in
FIG. 7A) of the body 110. Of course, the diameter of the head 120b
is not limited thereto.
[0120] The viewport 220b of the chamber 200a may have a structure
in which the viewport 220b is inserted into a through-hole H3 in
the wall 210a of the chamber 200a, and may include a groove or
channel G in the central portion thereof. The groove G of the
viewport 220b may have a cylindrical shape. Of course, the groove G
of the viewport 220b is not limited to the cylindrical shape. A
fifth diameter D5 of the groove G of the viewport 220b may be
similar to or slightly greater than the third diameter D3 of the
head 120b. The microwave probe 100e may be coupled to the chamber
200a such that the body 110 and the head 120b are inserted into the
groove G of the viewport 220b.
[0121] As shown in FIG. 12A, the outer surface of the viewport 220b
and the outer surface of the wall 210a of the chamber 200a may be
in the same plane, and the ground cover 140 may be coupled to the
chamber 200a to contact both the outer surface of the viewport 220b
and the outer surface of the wall 210a of the chamber 200a. Of
course, the outer surface of the viewport 220b may be closer to the
inside of the chamber 200a than the outer surface of the wall 210a
of the chamber 200a. In this case, the ground cover 140 may contact
only the outer surface of the wall 210a of the chamber 200a. Of
course, although not shown in FIG. 12A, the insulating liner 230
may be arranged on the inner side or surface of the wall 210a of
the chamber 200a as in FIG. 8A or 9A.
[0122] Referring to FIG. 12B, a microwave probe 100f according to
the present example embodiment may differ from the microwave probe
100e of FIG. 12A in that the microwave probe 100f further includes
an outer cover layer 115. For example, the microwave probe 100f may
further include the outer cover layer 115 surrounding the body 110.
The outer cover layer 115 may have a cylindrical tube shape, and
have a diameter that is about or almost the same as the fifth
diameter D5 of the groove G of the viewport 220b. The outer cover
layer 115 may include a metal such as Cu, or Al. However, the outer
cover layer 115 may also include a non-metal such as a plastic. In
addition, the outer cover layer 115 may include a non-metal such as
a plastic, and a metal only on an outer surface thereof.
[0123] When the microwave probe 100f is coupled to the viewport
220b of the chamber 200a, the outer cover layer 115 is inserted
into the groove G of the viewport 220b to be firmly secured
therein. Since the outer cover layer 115 is secured to the groove
G, trembling, vibration, deformation, or the like of the head 120b
and the body 110 can be suppressed. In addition, if the outer cover
layer 115 includes a metal, the body 110 and the outer cover layer
115 may form a coaxial cable-like structure, and thus contribute to
improved signal transfer properties of the microwave probe
100f.
[0124] FIGS. 13A and 13B are graphs depicting reflection
coefficients along with frequencies while a pressure and applied
power inside a chamber are changed, using a microwave probe
according to an example embodiment of the inventive concept. An x
axis represents a frequency, and a y axis represents a reflection
coefficient S11. FIG. 13A is a graph obtained by changing the
applied power while a pressure of argon (Ar) gas inside the chamber
is fixed at 1 mTorr, and FIG. 13B is a graph obtained by changing
the pressure of Ar gas while the applied power is fixed at 3
kW.
[0125] Referring to FIG. 13A, it can be seen that a peak value of
the reflection coefficient S11 increases with increasing applied
power. That is, it can be seen that a resonant frequency increases
with increasing power. The increase of the resonant frequency may
mean an increase of a oscillation frequency (f.sub.pe) of plasma,
and the increase of the oscillation frequency (f.sub.pe) of the
plasma may finally mean an increase of an electron density of the
plasma. Thus, it can be seen that the electron density of the
plasma increases with increasing power. The reason for this may be
that since energy, which is transferred to process gases, for
example, Ar gas in the chamber, increases with increasing applied
RF power, kinetic energy and collision frequency of the process
gases increase, thereby increasing a possibility of plasma
generation. As described above, it can be confirmed that since
frequencies other than the resonant frequency are almost fully
reflected, the reflection coefficient S11 is close to 1.
[0126] Referring to FIG. 13B, it can be seen that the peak value of
the reflection coefficient S11 increases with increasing pressure
in the chamber. That is, it can be seen that the resonant frequency
increases with increasing pressure.
[0127] Like the above conclusion that the increase of the resonant
frequency due to the increase of the power leads to the increase of
the electron density of the plasma, the increase of the resonant
frequency due to the increase of the pressure may also lead to the
increase of the electron density of the plasma. The increase of the
electron density of the plasma due to the increase of the pressure
may be caused by the fact that since the increase of the pressure
leads to an increase of an amount of the process gases, for
example, Ar gas in the chamber, the collision frequency of the
process gases increase, thereby increasing a possibility of plasma
generation.
[0128] FIG. 14 is a graph depicting a correlation between an
oscillation frequency of plasma and an absorption frequency of a
surface wave depending upon a pressure change. An x axis represents
the oscillation frequency (f.sub.pe) of the plasma, and a y axis
represents the absorption frequency (f.sub.abs) of the surface
wave, that is, a resonant frequency of the surface wave.
Measurement may be performed in a chamber, on which a round
viewport is mounted, under Ar discharge.
[0129] Referring to FIG. 14, it can be seen that, for each
pressure, there is an approximate one dimensional graph relation
(e.g., an approximate linear relation) between the oscillation
frequency (f.sub.pe) of the plasma and the absorption frequency
(f.sub.abs) of the surface wave. Thus, a value of the proportional
factor k of Equation (3) may be found based on the graph of the
relation between the oscillation frequency (f.sub.pe) of the plasma
and the absorption frequency (f.sub.abs) of the surface wave. As
described above, if the value of the proportional factor k is found
and the resonant frequency is detected, an electron density of the
plasma can be calculated.
[0130] FIG. 15 is a schematic configuration diagram of a plasma
monitoring system including a microwave probe according to an
example embodiment of the inventive concept. In the interest of
brevity, details which have been described above with reference to
FIGS. 1A to 12B may be only briefly described or omitted.
[0131] Referring to FIG. 15, a plasma monitoring system 1000
according to the present example embodiment may include a microwave
probe 100a, a chamber 200, a network analyzer 300, RF power
supplies 400-1, 400-2, gas supplying sources 600-1, 600-2, a
pumping device 700, and a computer 800 for analysis.
[0132] For example, the microwave probe 100a may be the microwave
probe 100a of FIG. 2A. Of course, instead of the microwave probe
100a of FIG. 2A, any one of the microwave probes 100, 100b, 100c,
100d, 100e, 100f according to the other example embodiments may be
used for the plasma monitoring system 1000 according to the present
example embodiment. A structure of the microwave probe may
variously changed in consideration of a shape of a viewport 220 of
the chamber, or improvement in efficiencies of microwave
application and/or signal reception. In addition, considering that
a head can greatly contribute to improvement in efficiencies of
microwave application and/or signal reception, the head may have
various shapes as well as may include various-shaped patterns on a
surface thereof, which is brought into contact with the viewport
220 as described above with reference to FIG. 5.
[0133] The chamber 200 may be a chamber for a plasma process. For
example, as shown in FIG. 15, the chamber 200 may be a chamber for
inductively coupled plasma (ICP). Of course, the chamber 200 is not
limited to the chamber for ICP. For example, the plasma monitoring
system 1000 according to the present example embodiment may employ
various chambers such as a chamber for capacitively coupled plasma
(CCP), a chamber for electron cyclotron resonance (ECR) plasma, a
chamber for surface wave plasma (SWP), a chamber for helicon wave
plasma, a chamber for e-beam plasma, and the like. The chamber and
peripheral devices may also be collectively referred to, as a
plasma system, and the peripheral devices may slightly vary with a
kind of chamber. For example, in the plasma monitoring system 1000
according to the present example embodiment, the chamber 200 for
ICP, the RF power supplies 400-1, 400-2, the gas supplying sources
600-1, 600-2, and the pumping device 700 may be configured for an
ICP system.
[0134] For reference, plasma can be divided into low temperature
plasma and thermal plasma according to temperatures. Low
temperature plasma is mainly used for semiconductor processes such
as semiconductor fabrication, metal and ceramic thin film
fabrication, material synthesis, and the like, and thermal plasma
is used for metal cutting, and the like. Low temperature plasma can
be divided again into atmospheric pressure plasma, vacuum plasma,
next generation plasma, and the like according to applications. An
atmospheric pressure plasma technique refers to a technique of
generating low temperature plasma while a pressure of a gas is
maintained at 100 Torr to atmospheric pressure (760 Torr), and may
be used for surface modification, display flat panel cleaning,
light sources for LCDs, and the like. A vacuum plasma technique
refers to a technique of generating low temperature plasma while a
pressure of a gas is maintained at 100 Torr or less, and may be
used for dry etching, thin film deposition, PR ashing, ALD growth,
and the like in semiconductor processes, and used for etching, thin
film deposition, and the like with respect to a display flat panel
in display processes. A next generation plasma technique may refer
to a technique of generating advanced concept low temperature
plasma and/or generating low temperature plasma capable of being
used for next generation new technologies.
[0135] The chamber 200 may fundamentally include the wall 210, the
viewport 220, the electrostatic chuck (ESC) 240, and a shower head
250. Since the wall 210 and the viewport 220 have been described
above with respect to FIGS. 8A and 8B, details thereof will not be
repeated in the interest of brevity. The electrostatic chuck 240 is
arranged in a lower portion inside the chamber 200, and a wafer 500
may be placed on an upper surface of the electrostatic chuck 240
and secured thereto. The electrostatic chuck 240 may allow the
wafer 500 to be secured thereto using electrostatic force. The
shower head 250 is arranged in an upper portion inside the chamber
200, and may spray a process gas or the like into the chamber 200
through a plurality of spray holes.
[0136] The RF power supplies 400-1, 400-2 may include an upper RF
power supply 400-1 and a lower RF power supply 400-2. The upper RF
power supply 400-1 may include an RF generator 410-1, a matcher
430-1, and a coil 450. The RF generator 410-1 generates RF power,
and the matcher 430-1 stabilizes plasma by adjusting impedance. The
matcher 430-1 is also referred to as a matching box. The coil 450
is spirally arranged on an upper side of the chamber 200, and
generates a magnetic field inside the chamber by RF power
application. The magnetic field accelerates electrons or ions
inside the chamber to further accelerate plasma generation.
[0137] The lower RF power supply 400-2 may also include an RF
generator 410-2 and a matcher 430-2, and apply RF power to the
wafer 500 instead of the coil. In some cases, RF power may be
applied to the wafer 500 via the electrostatic chuck 240.
[0138] The gas supplying sources 600-1, 600-2 supply process gases
required for a plasma process. Here, the process gases may refer to
all gases, such as a source gas, a reaction gas, a purge gas, and
the like, required for a corresponding plasma process. Although the
two gas supplying sources 600-1, 600-2 are shown in FIG. 15, two or
more gas supplying sources may be included according to the kinds
of process gases. The process gases of the gas supplying sources
600-1, 600-2 are supplied to the shower head 250 through gas
supplying tubes, and sprayed into the chamber 200 through the
shower head 250. In some cases, a specific process gas of the gas
supplying sources 600-1, 600-2 may be directly supplied into the
chamber 200 through a gas supplying tube directly connected into
the chamber 200.
[0139] The pumping device 700 may discharge gases inside the
chamber 200 to the outside of the chamber 200 through a vacuum pump
or the like after a plasma process. In addition, the pumping device
700 may serve to adjust a pressure inside the chamber 200.
[0140] The network analyzer 300 is as described above with
reference to FIG. 11. The computer 800 for analysis may be a
general personal computer (PC), a workstation, a supercomputer, or
the like. An analysis program, which can calculate an electron
density of plasma based on Equations (1) to (3), the proportional
factor k, and the like, is installed in the computer 800 for
analysis. Thus, the computer 800 for analysis may receive a
detected resonant frequency that is input from the network analyzer
300, and calculate an electron density of plasma using the analysis
program. In addition, the computer 800 for analysis may determine
whether there is a problem in a plasma state by comparing the
calculated electron density of the plasma with a pre-set reference
value. Further, when there is a problem in the plasma state, the
computer 800 for analysis may also analyze a cause thereof and
suggest new process conditions for a plasma process in
question.
[0141] The plasma monitoring system 1000 according to the present
example embodiment includes the microwave probe 100a which is
non-invasively coupled to the viewport 220 of the chamber 200,
whereby the microwave probe 100a does not affect the plasma state
inside the chamber 200. Thus, the plasma monitoring system 1000 can
precisely detect the plasma state inside the chamber 200 using the
microwave probe 100a and the network analyzer 300. In addition, the
plasma monitoring system 1000 includes the microwave probe 100a
which includes the body 110 including the insulation covering layer
114, the disk-shaped head 120, and the ground cover 140 covering
the body 110 and the head 120 and maintaining a grounded state,
thereby optimizing and maximizing microwave application and a
measurement sensitivity to signals inside the chamber 200. Thus,
the plasma monitoring system 1000 accurately detects the resonant
frequency, and accurately calculates the electron density of the
plasma based on the detected resonant frequency, thereby precisely
monitoring whether there is a problem in the plasma state inside
the chamber 200.
[0142] As described with reference to FIGS. 16 to 19, the plasma
monitoring system 1000 according to the present example embodiment
is used for determination of a time point of plasma stabilization,
tool matching between chambers, determination of a time point of
preventive maintenance (PM) for a chamber, sensing of in-process
issues, and the like, thereby significantly contributing to
optimization of a plasma process.
[0143] FIG. 16 is a graph showing a concept for determining a time
point of stabilization of plasma inside a chamber using a plasma
monitoring system according to an example embodiment of the
inventive concept. An x axis represents a wafer number introduced
into a chamber, a left y axis represents an electron density of
plasma inside the chamber, and a right y axis represents an etch
rate. The electron density of the plasma is marked by a symbol
.box-solid., and the etch rate is marked by a symbol .
[0144] Referring to FIG. 16, when a plasma process is newly
performed in the chamber (see the reference numeral 200 in FIG. 15)
in an idle state, it is necessary to determine whether generated
plasma reaches an appropriate state required for the plasma process
in question. That is, before a wafer for devices is subjected to
the plasma process, it is necessary to determine a time point of
plasma stabilization, that is, a time point of plasma back-up, and
only after the time point of plasma stabilization, the wafer for
devices can be subjected to the plasma process.
[0145] Generally, dummy wafers are introduced into the chamber and
subjected to a plasma process, followed by examining the dummy
wafers, for example, etch rates for the dummy wafers, thereby
determining whether plasma reaches an appropriate state. As such,
in the existing method of determining the time point of plasma
stabilization, a large number of dummy wafers, for example, one
hundred or more dummy wafers may be consumed, and a lot of time may
be spent since the dummy wafers need to be examined after the
plasma process.
[0146] However, if the plasma monitoring system (1000 in FIG. 15)
according to the present example embodiment is used, since the
plasma state can be detected in real time, upon determining the
time point of stabilization of plasma inside the chamber,
consumption of the dummy wafer can be significantly reduced, and
relatively short time can be spent. For example, the time point of
plasma stabilization can be accurately determined with consumption
of a few dummy wafers to dozens of dummy wafers.
[0147] As can be seen from the graph of FIG. 16, in the plasma
process for each of the dummy wafers, the electron density of the
plasma can be detected in real time using the plasma monitoring
system (1000 in FIG. 15) according to the present example
embodiment. As such, the electron density of the plasma is detected
in real time, whereby since the plasma state inside the chamber can
be somewhat predicted, examination of etch rates for a large number
of dummy wafers may not be needed. For example, it may be
sufficient only to examine etch rates for a few dummy wafers. Here,
examination of the dummy wafers may correspond to confirming
accuracy of the detected electron density of the plasma.
[0148] FIG. 17 is a conceptual diagram for explaining utilization
of a plasma monitoring system according to an example embodiment of
the inventive concept in tool matching between chambers.
[0149] Referring to FIG. 17, even though plasma processes are
performed in the same (a), (b), and (c) chambers under the same
conditions, states of plasma inside chambers may be different, as
shown in FIG. 17. For example, an electron density of plasma Pa of
the (a) chamber may be 10, an electron density of plasma Pb of the
(b) chamber may be 9, and an electron density of plasma Pc of the
(c) chamber may be 10. These differences may be caused by, for
example, wall conditions of the chambers.
[0150] Therefore, the wall conditions of the chambers may be found
by monitoring the electron density of the plasma inside each of the
chambers in real time using the plasma monitoring system according
to the present example embodiment, thereby utilizing the plasma
monitoring system in tool matching for an appropriate plasma
process of each chamber.
[0151] FIG. 18 is a graph showing a concept for determining a time
point of PM of a chamber using a plasma monitoring system according
to an example embodiment of the inventive concept.
[0152] Referring to FIG. 18, if a plasma process is performed in a
chamber for a long period of time, a plasma state inside the
chamber deviates from an appropriate plasma state. That is, as
shown in FIG. 18, an electron density of the plasma starts to
exceed an appropriate level after the time point of PM. Thus, if
the time point of PM is reached, PM, such as cleaning and the like,
for the chamber should be performed.
[0153] The plasma monitoring system according to the present
example embodiment (1000 in FIG. 15) monitors the electron density
of the plasma inside the chamber in real time, thereby relatively
accurately determining the time point of PM. Thus, the plasma
monitoring system can contribute to improvement in a plasma process
efficiency due to reduction of a PM cycle and maintenance of a good
chamber state.
[0154] For reference, a symbol Bup on an x axis may refer to the
time point of plasma stabilization, that is, the time point of
plasma back-up as described above with reference to FIG. 16, and a
symbol S on a y axis may refer to the appropriate electron density
of the plasma.
[0155] FIG. 19 is a graph depicting electron densities of plasma
detected using a plasma monitoring system according to an example
embodiment of the inventive concept in plasma processes for a first
wafer and a ninth wafer.
[0156] Referring to FIG. 19, a plasma process for one wafer may
generally include a plurality of sub-plasma processes. As shown in
FIG. 19, each of the plasma processes for the first wafer (thin
line) and the ninth wafer (thick line) may include a plurality of
sub-plasma processes. In addition, each of the sub-plasma processes
may have a corresponding electron density of plasma, ranges on an x
axis, in which the electron density is 0; these may be periods of
time in which the plasma process is stopped for a short time.
[0157] The plasma processes for the first wafer and the ninth wafer
may be performed in the same chamber under the same process
conditions. Thus, the plasma electron densities of the sub-plasma
processes for the first wafer and the ninth wafer should be the
same. However, as shown in FIG. 19, it can be confirmed that the
plasma electron densities in the sub-plasma processes are
different. Thus, it can be seen that a problem occurred in the
plasma process for the ninth wafer. More precisely, it can be seen
that, among the sub-plasma processes, problems occurred in the
sub-plasma processes (marked by dashed circles) showing noticeable
differences in plasma electron densities. For reference, since
plasma electron densities of second to eighth wafers were
substantially the same as the plasma electron density of the first
wafer, it can be anticipated that there was not a problem until or
after the plasma process for the eighth wafer.
[0158] As such, the plasma monitoring system (1000 in FIG. 15)
according to the present example embodiment measures the electron
density of the plasma in the plasma process for each wafer in real
time, thereby monitoring problems during the plasma process, that
is, in-process issues in real time. In addition, when the
in-process issues are discovered, causes thereof are analyzed and
utilized, whereby the plasma monitoring system can contribute to
optimization of the plasma process. Here, analysis and utilization
of the causes may include, for example, removal of the discovered
causes, solving the problems by changing process conditions when
the causes cannot be removed, or the like.
[0159] FIG. 20 is a flow chart showing a process of monitoring a
plasma state and controlling a plasma process according to an
example embodiment of the inventive concept. For convenience,
descriptions will be made with reference to FIG. 15 together.
[0160] Referring to FIG. 20, first, the microwave probe is coupled
to the viewport 220 of the chamber 200 (S110). The microwave probe
may be the microwave probe 100a of FIG. 2A. Of course, instead of
the microwave probe 100a of FIG. 2A, the microwave probes 100, 100b
to 100c according to the other example embodiments may be coupled
to the viewport 220. In addition, when the viewport 220 has the
structure illustrated in FIG. 12A, the microwave probe 100d, 100e,
or 100f of FIG. 7A, 7B, or 12B may be coupled to the viewport 220.
Coupling the microwave probe 100a to the viewport 220 may mean that
the network analyzer 300 is also coupled to the viewport 220
through the microwave probe 100a. When the microwave probe 100a is
coupled to the chamber 200, the computer 800 for analysis may be
connected to the network analyzer 300, and thereby receive data for
a resonant frequency transferred from the network analyzer 300 in
real time. In addition, the computer 800 for analysis may not be
connected to the network analyzer 300 until the network analyzer
300 detects the resonant frequency. After the network analyzer 300
detects the resonant frequency, the computer 800 for analysis may
be connected to the network analyzer 300, and thereby receive the
data for the resonant frequency, which is stored in the network
analyzer 300.
[0161] The wafer 500 is arranged on the electrostatic chuck 240
inside the chamber 200 (S120). The wafer 500 may also be arranged
on the electrostatic chuck 240 before the coupling of the microwave
probe 100a.
[0162] Plasma is generated by injecting the process gases and
applying RF power into the chamber 200 (S130). The process gases
may be injected into the chamber 200 in such a manner that the
process gases supplied from the gas supplying sources 600-1, 600-2
are sprayed through the shower head 250. The application of the RF
power may be performed in such a manner that the RF power is
respectively applied to the coil 450 on the upper side of the
chamber 200 through the upper RF power supply 400-1 and to the
wafer 500 inside the chamber 200 through the lower RF power supply
400-2.
[0163] In the present operation, the generation of the plasma may
refer to performing a plasma process using the generated plasma.
For example, the plasma process may include etching, deposition,
diffusion, surface treatment, novel material synthesis processes,
and the like.
[0164] Using the microwave probe 100a, a microwave is applied into
the chamber 200, and signals generated inside the chamber 200 are
received (S140). An absorption frequency signal of a surface wave,
that is, a resonant frequency signal of the surface wave may be
included in the generated signals. The microwave may be generated
in the network analyzer 300 and applied into the chamber 200
through the microwave probe 100a. In addition, the signals
generated inside the chamber 200 may be received through the
microwave probe 100a, and transferred to the network analyzer 300
through the external wire 310.
[0165] A resonant frequency of the surface wave is detected from
the received signals, and a plasma state is analyzed based on the
resonant frequency (S150). The detection of the resonant frequency
may be performed by the network analyzer 300. For example, the
network analyzer 300 may detect the resonant frequency of the
surface wave by detecting a peak value of a reflection coefficient
S11.
[0166] The analysis of the plasma state may be performed by the
computer 800 for analysis. For example, the computer 800 for
analysis receives the detected resonant frequency that is input
from the network analyzer 300, and calculates an electron density
of the plasma using an analysis program. The analysis program may
be a program for calculating the electron density of the plasma
using Equations (1) to (3), the value of the proportional factor k,
and the like.
[0167] Whether the plasma state is within an allowable range is
determined (S160). The determination of whether the plasma state is
within the allowable range may be performed by the computer 800 for
analysis. For example, whether there is a problem in the plasma
state may also be determined by comparing the calculated plasma
electron density with a pre-set reference value. Further, when
there is a problem in the plasma state, the computer 800 for
analysis may also analyze a cause thereof and suggest new process
conditions for the plasma process in question.
[0168] If the plasma state is within the allowable range (Yes),
monitoring of the plasma state is terminated. If the plasma state
is outside of the allowable range (No), process parameters of the
plasma process are adjusted (S170). The adjustment of the process
parameters may be performed through, for example, increase or
decrease in pressures of the process gases, increase or decrease in
applied RF power, or the like. The adjustment of the process
parameters may be performed based on data obtained through a
simulation in the computer 800 for analysis.
[0169] After the adjustment of the process parameters, the process
returns to arranging a new wafer inside the chamber (S120), and the
plasma process and monitoring thereof are performed again.
[0170] Since the method of monitoring the plasma state according to
the present example embodiment is performed using the microwave
probe, which is non-invasively coupled to the chamber 200 and has
the structure illustrated in any one of FIG. 1A to FIG. 12B, the
plasma state inside the chamber 200 can be precisely detected and
monitored by the method due to a high reception sensitivity to the
signals inside the chamber 200, with no influence on the plasma
state inside the chamber 200. In addition, the method of
controlling the plasma process according to the present example
embodiment appropriately controls process conditions of the plasma
process based on accurate monitoring of the plasma state inside the
chamber 200 using the microwave probe, thereby optimizing the
plasma process.
[0171] FIG. 21 is a flow chart showing a process of fabricating a
semiconductor device through the control of the plasma process
according to an example embodiment of the inventive concept. In the
interest of brevity, details which have been described above with
reference to FIG. 20 may be only briefly described or omitted.
[0172] Referring to FIG. 21, first, the methods of monitoring the
plasma state and controlling the plasma process described above
with reference to FIG. 20 are performed. The methods of monitoring
the plasma state and controlling the plasma process may include a
plasma process for the wafer 500. For example, the generating of
the plasma (S130) as described with reference to FIG. 20 may
correspond to the plasma process for the wafer 500.
[0173] For reference, in FIG. 21, operation "S160" may refer to
performing the methods of monitoring the plasma state and
controlling the plasma process as described with reference to FIG.
20, and an arrow from operation "S160" may mean that the process
proceeds to the next operation since the methods of monitoring the
plasma state and controlling the plasma process are completed. More
precisely, in operation S160 of determining the allowable range of
the plasma state in FIG. 20, the arrow from operation "S160" may
mean that since the plasma state is within the allowable range
(Yes), the methods of monitoring the plasma state and controlling
the plasma process are completed, and the process proceeds to the
next operation.
[0174] A subsequent semiconductor process for the wafer 500 is
performed (S210). The subsequent semiconductor process for the
wafer 500 may include various processes. For example, the
subsequent semiconductor process for the wafer 500 may include a
deposition process, an etching process, an ion process, a cleaning
process, and the like. The deposition process, the etching process,
the ion process, the cleaning process, and the like may be
processes using plasma, or may be processes not using plasma. If
the processes set forth above are processes using plasma, the
methods of monitoring the plasma state and controlling the plasma
process described above may be used again. The subsequent
semiconductor process for the wafer 500 is performed, thereby
forming integrated circuits and wires required for a semiconductor
device in question. The subsequent semiconductor process for the
wafer may also include a process of testing a wafer-level
semiconductor device.
[0175] The wafer 500 is separated into individual semiconductor
chips (S220). The separation into the individual semiconductor
chips may be performed through a sawing process using a blade or
laser.
[0176] Next, a packaging process for the semiconductor chips is
performed (S230). The packaging process may refer to mounting the
semiconductor chips on a PCB and sealing the chips with a sealant.
The packaging process may include forming a stack package by
stacking a plurality of semiconductors as multiple layers on the
PCB, or forming a package on package (POP) structure by stacking a
stack package on another stack package. A semiconductor device or a
semiconductor package may be completed through the packaging
process for the semiconductor chips. After the packaging process, a
test process for the semiconductor package may be performed.
[0177] The method of fabricating a semiconductor device according
to the present example embodiment performs plasma state monitoring
and plasma process control using the plasma monitoring system 1000
of FIG. 15, thereby optimizing the plasma process. In addition, the
method of fabricating a semiconductor device fabricates
semiconductor devices based on the optimized plasma process,
thereby realizing excellent and highly reliable semiconductor
devices.
[0178] While the inventive concept has been particularly shown and
described with reference to example embodiments thereof, it will be
understood that various changes in form and details may be made
therein without departing from the spirit and scope of the
following claims.
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