U.S. patent application number 16/582115 was filed with the patent office on 2020-03-26 for plasma processing apparatus.
This patent application is currently assigned to TOKYO ELECTRON LIMITED. The applicant listed for this patent is TOKYO ELECTRON LIMITED. Invention is credited to Takaaki KIKUCHI, Takaharu MIYADATE, Atsushi OGATA, Nobutaka SASAKI, Takashi TAIRA, Shuichi TAKAHASHI.
Application Number | 20200098550 16/582115 |
Document ID | / |
Family ID | 69883612 |
Filed Date | 2020-03-26 |
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United States Patent
Application |
20200098550 |
Kind Code |
A1 |
TAKAHASHI; Shuichi ; et
al. |
March 26, 2020 |
PLASMA PROCESSING APPARATUS
Abstract
In a plasma processing apparatus, a table has a wafer support to
hold a wafer and a peripheral segment surrounding the wafer support
and having through-holes. The peripheral segment has an upper
surface lower than that of the wafer support. An outer focus ring
is disposed over the peripheral segment and has a recess or a
cutout at an inner portion of the outer focus ring, and the recess
or cutout has through-holes. An inner focus ring is disposed in the
recess or cutout of the outer focus ring. Lift pins respectively
extend through the through-holes of the peripheral segment and the
through-holes of the recess or cutout of the outer focus ring.
Shift mechanisms control shift of the respective lift pins.
Inventors: |
TAKAHASHI; Shuichi; (Miyagi,
JP) ; MIYADATE; Takaharu; (Miyagi, JP) ;
KIKUCHI; Takaaki; (Miyagi, JP) ; OGATA; Atsushi;
(Miyagi, JP) ; SASAKI; Nobutaka; (Miyagi, JP)
; TAIRA; Takashi; (Miyagi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TOKYO ELECTRON LIMITED |
Tokyo |
|
JP |
|
|
Assignee: |
TOKYO ELECTRON LIMITED
Tokyo
JP
|
Family ID: |
69883612 |
Appl. No.: |
16/582115 |
Filed: |
September 25, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01J 37/32642 20130101;
H01L 21/6833 20130101; H01L 21/67109 20130101; H01J 2237/002
20130101; H01L 21/67103 20130101; H01J 2237/20235 20130101; H01L
21/68735 20130101; H01L 21/68742 20130101; H01J 37/32724 20130101;
H01L 21/67069 20130101; H01L 21/6831 20130101; H01J 2237/334
20130101 |
International
Class: |
H01J 37/32 20060101
H01J037/32; H01L 21/687 20060101 H01L021/687 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 26, 2018 |
JP |
2018-180956 |
Claims
1. A plasma processing apparatus comprising: a table having a wafer
support to hold a wafer and a peripheral segment surrounding the
wafer support and having through-holes, the peripheral segment
having an upper surface lower than that of the wafer support; an
outer focus ring disposed over the peripheral segment and having a
recess or a cutout at an inner portion of the outer focus ring, the
recess or cutout having through-holes; an inner focus ring disposed
in the recess or cutout of the outer focus ring; lift pins
respectivley extending through the through-holes of the peripheral
segment and the through-holes of the recess or cutout of the outer
focus ring; and shift mechanisms to control shift of the respective
lift pins.
2. The apparatus of claim 1, wherein the lift pins are in contact
with the inner focus ring during plasma processing.
3. The apparatus of claim 1, wherein each of the shift mechanisms
is capable of verically shifting the corresponding lift pin with a
first shift precision of about 0.02 mm at a pitch of 1 mm to 2 mm
and a second shift precision of about 0.1 mm at a pitch of 20
mm.
4. The apparatus of claim 1, wherein each of the shift mechanisms
includes: a driver; a thruster coaxially connected to the
corresponding lift pin; and a transmitter configured to transmit a
power of the driver to the thruster.
5. The apparatus of claim 1, wherein an inner peripheral surface
and a bottom surface of the outer focus ring are insulated from the
table.
6. The apparatus of claim 1, wherein the through-holes are disposed
at substantially equal intervals in a circumferential direction of
the outer focus ring.
7. The apparatus of claim 1, wherein the inner focus ring has a
radial width in a range from 3 mm to 15 mm.
8. The apparatus of claim 1, wherein the inner focus ring has an
inner diameter greater than an outer diameter of the wafer.
9. The apparatus of claim 1, wherein an upper end of an inner
peripheral surface of the inner focus ring has a chamfered upper
inner corner.
10. The apparatus of claim 1, wherein a height of an upper face of
the inner focus ring is lower at an inner side of the inner focus
ring than that at an outer side of the inner focus ring.
11. A plasma processing apparatus comprising: a table having a
wafer support to hold a wafer and a peripheral segment surrounding
the wafer support and having through-holes, the peripheral segment
having an upper surface lower than that of the wafer support; a
focus ring disposed over the peripheral segment of the table and
having an inner periphery facing an outer periphery of the wafer
support; lift pins extending through the table for raising the
focus ring; and shift mechanisms configured to control shift of the
respective lift pins with one of a first shift precision and a
second shift precision different from the first shift
precision.
12. The apparatus of claim 11, wherein the first shift precision is
higher than the second shift precision.
13. The apparatus of claim 12, wherein the first shift precision is
used for raising the focus ring to a plasma processing position,
and the second shift precision is used for raising the focus ring
to an unloading position.
14. The apparatus of claim 3, wherein a moving speed in the axial
direction of the lift pins during the vertical shift with the
second shift precision is higher than a moving speed in the axial
direction of the lift pins during the vertical shift with the first
shift precision.
15. The apparatus of claim 11, wherein a moving speed in the axial
direction of the lift pins during the control with the second shift
precision is higher than a moving speed in the axial direction of
the lift pins during the control with the first shift precision.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to Japanese Patent
Application No. 2018-180956, filed on Sep. 26, 2018, the entire
contents of which are incorporated herein by reference.
TECHNICAL FIELD
[0002] The present disclosure relates to a plasma processing
apparatus.
BACKGROUND
[0003] As it is known, a plasma processing apparatus including a
focus ring has been provided (see, Japanese Patent Application
Publication No. 2008-244274). The focus ring is disposed to
surround an outer periphery of a processing target, e.g., a
semiconductor wafer (hereinafter, referred to as "wafer"). The
focus ring is provided to control plasma near the outer periphery
of the wafer to improve in-plane etching uniformity of the
wafer.
[0004] The present disclosure provides a technique capable of
improving the positional accuracy in driving and transferring the
focus ring.
SUMMARY
[0005] In accordance with an aspect of the present disclosure,
there is provided a plasma processing apparatus including: a table
having a wafer support to hold a wafer and a peripheral segment
surrounding the wafer support and having through-holes, the
peripheral segment having an upper surface lower than that of the
wafer support; an outer focus ring disposed over the peripheral
segment and having a recess or a cutout at an inner portion of the
outer focus ring, the recess or cutout having through-holes; an
inner focus ring disposed in the recess or cutout of the outer
focus ring; lift pins respectively extending through the
through-holes of the peripheral segment and the through-holes of
the recess or cutout of the outer focus ring; and shift mechanisms
to control shift of the respective lift pins.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] The objects and features of the present disclosure will
become apparent from the following description of embodiments,
given in conjunction with the accompanying drawings, in which:
[0007] FIG. 1 shows an example of a configuration of a plasma
processing apparatus according to an embodiment;
[0008] FIG. 2 shows an example of configurations of a focus ring, a
lift pin, and a shift mechanism according to the embodiment;
[0009] FIG. 3A is a cross-sectional view of the focus ring
according to the embodiment;
[0010] FIG. 3B is a perspective view of the focus ring according to
the embodiment.
[0011] FIG. 3C is a top view of an outer focus ring according to
the embodiment;
[0012] FIG. 3D is a top view showing a state in which an inner
focus ring is disposed at the outer focus ring according to the
embodiment;
[0013] FIG. 4A explains a first shift control of the inner focus
ring according to the embodiment;
[0014] FIG. 4B explains a second shift control of the inner focus
ring according to the embodiment;
[0015] FIG. 5 is a cross-sectional view of a focus ring according
to a first modification;
[0016] FIG. 6A explains a first shift control of an inner focus
ring according to the first modification; and
[0017] FIG. 6B explains a second shift control of the inner focus
ring according to the first modification.
DETAILED DESCRIPTION
[0018] Hereinafter, embodiments will be described in detail with
reference to the accompanying drawings. The following embodiments
are not intended to limit the present disclosure. The respective
embodiments may be appropriately combined with each other within a
range in which processing contents do not contradict each other.
Like reference numerals will be given to substantially like parts
throughout this specification and the drawings, and redundant
description thereof will be omitted.
[0019] In the following description, when a wafer is held on a
table of a plasma processing apparatus, the table side when viewed
from the wafer is referred to as "lower side," and the opposite
side is referred to as "upper side."
[0020] FIG. 1 shows an example of a configuration of a plasma
processing apparatus 5 according to an embodiment. In the present
embodiment, a capacitively coupled parallel plate type plasma
processing apparatus will be described as an example of the plasma
processing apparatus 5.
[0021] The plasma processing apparatus 5 includes a chamber 10 that
is a cylindrical vacuum container made of a metal such as aluminum,
stainless steel, or the like. The chamber 10 is an example of a
processing container and has an inner space serving as a processing
chamber where plasma processing is performed. The chamber 10 is
grounded.
[0022] At a lower central portion of the chamber 10, a disk-shaped
stage 12 for mounting thereon a target object, e.g., a wafer W, is
disposed as a substrate holder serving as a lower electrode. The
stage 12 is supported by a cylindrical support 16 that is made of,
e.g., aluminum, and extends vertically upward from the bottom of
the chamber 10 and a housing 100 disposed at an inner side of the
cylindrical support 16. In the example shown in FIG. 1, a structure
45 is disposed between the stage 12 and the housing 100. A recess
is formed on a contact surface between the structure 45 and the
stage 12, and a sealing member 47 is disposed in the recess. The
housing 100 is made of, e.g., ceramic. In the example shown in FIG.
1, the cylindrical support 16 includes an aluminum portion 16a
disposed at a lower portion of the chamber 10 and a quartz portion
16b disposed on the aluminum portion 16a.
[0023] An annular gas exhaust passage 18 is formed between the
cylindrical support 16 and an inner wall of the chamber 10. An
annular baffle plate 20 is installed at an upstream side or an
inlet of the gas exhaust passage 18, and a gas exhaust port 22 is
provided at a downstream side of the gas exhaust passage 18. The
baffle plate 20 is fitted to the cylindrical support portion 16 to
be reinforced by the aluminum portion 16a.
[0024] A gas exhaust unit (GEU) 26 is connected to the gas exhaust
port 22 through a gas exhaust line 24. The gas exhaust unit 26 has
a vacuum pump such as a turbo molecular pump or the like, and thus
can reduce a pressure in a plasma generation space S in the chamber
10 to a desired vacuum level. A gate valve 28 for opening and
closing a loading/unloading port 27 for the wafer W is disposed an
outer sidewall of the chamber 10.
[0025] A second high frequency power supply 30 is electrically
connected to the stage 12 via a matching unit (MU) 32 and a power
feed rod 34. The second high frequency power supply 30 is
configured to output a high frequency power LF at a variable power
level, the high frequency power LF having a first frequency (e.g.,
13.56 MHz) suitable for controlling energy of ions to be attracted
to the wafer W. The matching unit 32 includes a reactance variable
matching circuit for matching an impedance of the second high
frequency power supply 30 side and an impedance of a load (plasma
or the like) side.
[0026] An electrostatic chuck 36 for attacting and holding the
wafer W by a Coulomb force is disposed on an upper surface of the
stage 12. The electrostatic chuck 36 has an electrode 36a made of a
conductive film and two insulating films 36b. The electrode 36a is
embedded between the two insulating films 36b, and a DC power
supply 40 is electrically connected to the electrode 36a through a
switch 42 and a coated wire 43. The insulating films 36b are made
of, e.g., a ceramic sintered body. The wafer W is attracted and
held on the electrostatic chuck 36 by an electrostatic force such
as a Coulomb force generated by a DC current supplied from the DC
power supply 40. A heater H that is a heating element is disposed
in the electrostatic chuck 36. A heater power supply (not shown) is
connected to the heater H. The temperature of the wafer W on the
electrostatic chuck 36 is controlled to a predetermined temperature
by heating using the heater H and cooling using a coolant to be
described later. Further, the heater H may be disposed in the stage
12.
[0027] An annular coolant channel 44 extending in, e.g., a
circumferential direction, is formed in the stage 12. A coolant,
e.g., cooling water cw, having a predetermined temperature is
supplied from a chiller unit through lines 46 and 48 and circulated
in the coolant flow channel 44. Accordingly, the temperature of the
wafer W on the electrostatic chuck 36 can be controlled by the
temperature of the coolant. In addition, a heat transfer gas such
as He gas from a heat transfer gas supply unit is supplied to a gap
between an upper surface of the electrostatic chuck 36 and the
backside of the wafer W through a gas supply line 50. Further, a
pusher pin that is raised and lowered while penetrating through the
stage 12 in a vertical direction to load and unload the wafer W,
and a shift mechanism for driving the pusher pin are provided.
[0028] A gas shower head 51 is disposed to block an opening formed
at the ceiling of the chamber 10 through a shield ring 54 that
covers an outer edge of the gas shower head 51. The gas shower head
51 is made of silicon. The gas shower head 51 also serves as a
facing electrode (upper electrode) opposite to the stage 12 (lower
electrode).
[0029] A gas inlet 56 for introducing a gas is formed at the gas
shower head 51. A diffusion space 58 connected to the gas inlet 56
is disposed in the gas shower head 51. The gas outputted from a gas
supply source (GS) 66 is supplied to the diffusion space 58 through
the gas inlet 56, and then diffused and introduced into the plasma
generation space S through a plurality of gas injection holes
52.
[0030] A first high frequency power supply 57 is electrically
connected to the gas shower head 51 through a matching unit (MU) 59
and a power feed line 60. The first high frequency power supply 57
is configured to output a high frequency power HF at a variable
power level, the high frequency power HF having a second frequency
(e.g., 40 MHz) that is suitable for plasma generation and is higher
than the first frequency. The matching unit 59 includes a reactance
variable matching circuit for matching an impedance of the first
high frequency power supply 57 side and the impedance of the load
(plasma or the like) side.
[0031] A controller (CNT) 74 includes, e.g., a microcomputer, and
is configured to control the operations of the respective
components in the plasma processing apparatus 5 and the operation
of the entire apparatus. The components of the plasma processing
apparatus 5 include the gas exhaust unit 26, the first high
frequency power supply 57, the second high frequency power supply
30, the matching units 32 and 59, the switch 42 for the
electrostatic chuck, the gas supply source (GS) 66, the chiller
unit, the heat transfer gas supply unit, and the like.
[0032] In order to perform various processes such as etching and
the like in the plasma processing apparatus 5, first, the gate
valve 28 is opened, and the wafer W is loaded into the chamber 10
and mounted on the electrostatic chuck 36. Then, the gate valve 28
is closed, and a predetermined gas is introduced from the gas
supply source 66 into the chamber 10 at a predetermined flow rate
and a predetermined flow rate ratio. Then, the pressure in the
chamber 10 is reduced to a predetermined set value by the gas
exhaust unit 26. Further, the first high frequency power supply 57
is turned on to output the high frequency power HF for plasma
generation at a predetermined power level. The high frequency power
HF is supplied to the gas shower head 51 through the matching unit
59 and the power feed line 60.
[0033] When the high frequency power LF for ion attraction control
is applied, the second high frequency power supply 30 is turned on
to output the high frequency power LF at a predetermined power
level. The high frequency power LF is applied to the stage 12
through the matching unit 32 and the power feed rod 34. In
addition, the heat transfer gas is supplied from the heat transfer
gas supply unit to the contact surface between the electrostatic
chuck 36 and the wafer W. Further, the switch 42 is turned on to
apply the DC voltage from the DC power supply 40 to the electrode
36a of the electrostatic chuck 36, and the heat transfer gas is
confined to the contact surface by electrostatic attractive
force.
[0034] <Configuration of Focus Ring FR According to
Embodiment>
[0035] A focus ring FR is disposed at an outer periphery of the
stage 12 to annularly surround an outer periphery of the wafer W.
The focus ring FR is configured to control the plasma at the outer
periphery of the wafer and improve the uniformity of the processing
such as an in-plane etching rate of the wafer W or the like. In
addition, a cover ring CR is disposed to surround an outer
periphery of the focus ring FR. The cover ring CR is a ring-shaped
member made of, e.g., quartz, and protects an upper surface of the
cylindrical support 16 from the plasma.
[0036] The etching rate and/or the etching shape at an edge portion
of the wafer W changes depending on a height of the focus ring FR.
Therefore, when the height of an upper surface of the focus ring FT
changes due to consumption of the focus ring FR, the sheath shape
above the edge portion of the wafer W changes which leads to the
change of the processing shape at the edge portion of the wafer W.
In the present embodiment, the edge portion of the wafer W
indicates a ring-shaped portion spaced apart from the center of the
wafer W by a distance of about 140 mm to 150 mm in a radial
direction. The clearance between the components of the plasma
processing apparatus 5 may be about 0.1 mm to 0.5 mm. However, the
clearance is appropriately omitted in the drawings.
[0037] Therefore, the plasma processing apparatus 5 of the present
embodiment includes the focus ring FR that is divided into two
parts. In the present embodiment, the focus ring FR is divided into
an inner focus ring 38i and an outer focus ring 38o.
[0038] Further, the plasma processing apparatus 5 of the present
embodiment is configured to adjust a position of an upper surface
of the inner focus ring 38i that affects the in-plane etching
uniformity of the wafer in response to the consumption of the focus
ring FR. Further, the plasma processing apparatus 5 of the present
embodiment is configured to automatically replace the inner focus
ring 38i without opening and closing the chamber 10. Therefore, the
plasma processing apparatus 5 of the present embodiment further
includes shift mechanisms 200 and lift pins 102 in a one-to-one
relationship with the shift mechanisms 200. Hereinafter, the
adjustment of the position of the upper surface of the inner focus
ring 38i, which is performed to maintain the uniformity of the
plasma processing, is referred to as "first shift control." The
control for raising the inner focus ring 38i in order to replace
and transfer the inner focus ring 38i is referred to as "second
shift control."
[0039] When the first shift control is performed, each of the shift
mechanisms 200 adjusts a shift amount of the corresponding the lift
pin 102 with a driving precision of 0.02 mm at a pitch of 1.0 mm to
2.0 mm, for example. The position of the upper surface of the inner
focus ring 38i is adjusted by the shift of the respective lift pins
102.
[0040] When the second shift control is performed, each of the
shift mechanisms 200 adjusts the shift amount of the corresponding
lift pin 102 with a driving precision of about 0.1 mm at a pitch of
about 20 mm, e.g., 18 mm. In other words, in the second shift
control, the shift mechanisms 200 move the lift pins 102 at a pitch
larger than that used for adjusting the position of the upper
surface of the inner focus ring 38i. As the lift pins 102 are moved
up, the inner focus ring 38i is lifted. The lifted inner focus ring
38i can be transferred to the outside of the chamber 10 by the same
transfer unit as that used for transferring the wafer W.
Thereafter, a new inner focus ring 38i can be transferred into the
chamber 10 in the same manner as for transferring the wafer W.
[0041] <Configuration Example of Shift Mechanism 200>
[0042] FIG. 2 shows an example of the configurations of the focus
ring FR, the lift pins 102, and the shift mechanisms 200 according
to the embodiment. In FIGS. 2 to 6B, only one lift pin 102 and one
shift mechanism are illustrated for the sake of convenience. First,
the shift mechanism 200 will be described with reference to FIG.
2.
[0043] The shift mechanism 200 includes a driver 101, a transmitter
103, and a thruster 105.
[0044] The driver 101 is, e.g., a motor such as a stepping motor,
or an air driving mechanism. The driver 101 is arranged at a
position apart from the axial direction of the lift pin 102 and is
connected to the lift pin 102 through the transmitter 103 and the
thruster 105. The power generated by the driver 101 is transmitted
to the thruster 105 and further the lift pin 102 through the
transmitter 103. As for a micron level driver, a piezo actuator may
be appropriately employed. However, in the present embodiment, a
motor such as the stepping motor, the air driver, or the like is
employed to perform the first shift control and the second shift
control by one shift mechanism 200.
[0045] The transmitter 103 is disposed between the driver 101 and
the thruster 105 that are disposed on two different axes, and
connects the driver 101 and the thruster 105. The transmitter 103
transmits the power of the driver 101 to the thruster 105 and the
lift pin 102. The transmitter 103 is configured to connect an end
portion of the driver 101 and the thruster 105.
[0046] The thruster 105 is provided to absorb the deviation caused
by disposing the driver 101 and the lift pin 102 at different axes.
The driver 101 and the lift pin 102 are connected by the
transmitter 103. Since, however, the driver 101 and the lift pin
102 are disposed at the end portions of the transmitter 103, a
direction of the load applied to the lift pin 102 may be deviated
from the vertical direction due to the inclination of the
transmitter 103 or the like. When the direction of the load applied
to the lift pin 102 is deviated from the vertical direction, the
lift pin 102 may be damaged. Therefore, the thruster 105 is
provided to absorb the deviation in a shift direction of the lift
pin 102.
[0047] By providing the shift mechanism 200, the power generated by
the driver 101 is transmitted to the lift pin 102, and the lift pin
102 is moved vertically.
[0048] Meanwhile, depending on the configuration of the plasma
processing apparatus 5, the driver 101 and the lift pin 102 may be
arranged coaxially. In this case, the transmitter 103 and the
thruster 105 may be omitted.
[0049] <Configuration Example of Lift Pin 102>
[0050] The lift pin 102 is connected to the thruster 105 of the
shift mechanism 200 and extends upward from the thruster 105. The
lift pin 102 extends thorough through-holes 12a, 36f, and 38f (see
FIG. 3A, which will be described later) extending through the stage
12, the electrostatic chuck 36, and the outer focus ring 38o. The
upper end of the lift pin 102 is brought into contact with a bottom
surface of the inner focus ring 38i to support the inner focus ring
38i. Further, an O-ring 110 is disposed in the through-hole 12a of
the stage 12 to partition a vacuum space and an atmosphere space.
In the present embodiment, the upper end of the lift pin 102 is in
contact with the bottom surface of the inner focus ring 38i even
when the first shift control and the second shift control are not
performed.
[0051] The material of the lift pin 102 is not particularly
limited, but the lift pin 102 is preferably made of a material that
is less likely to generate particles when exposed to plasma, a
material that is less likely to be consumed when exposed to plasma,
or a material having a high stiffness. Therefore, the lift pin 102
is preferably made of sapphire or quartz.
[0052] <Two Steps of Position Control Using Shift Mechanism
200>
[0053] The shift mechanism 200 of the present embodiment is capable
of vertically shifting the lift pin 102 during the first shift
control and the second shift control. The driver 101 of the shift
mechanism 200 is configured to realize a precise vertical shift
(first shift control) with a driving precision of 0.02 mm at a
pitch of, e.g., 1.0 to 2.0 mm as well as a vertical shift having a
larger pitch (second shift control) with a driving precision of
about 0.1 mm at a pitch of about 20.0 mm, e.g., 18 mm.
[0054] When the first shift control is performed, the driver 101 of
the shift mechanism 200 raises the lift pin 102 in response to the
consumption of the inner focus ring 38i due to the plasma
processing. Accordingly, the positional relationship between the
position of the upper surface of the inner focus ring 38i and the
position of an upper surface of the wafer W on a wafer support 36c
is adjusted to a predetermined level. In one example, the position
of the upper surface of the inner focus ring 38i can be aligned
with the position of the upper surface position of the wafer W on
the wafer support 36c.
[0055] When the second shift control is performed, the driver 101
of the shift mechanism 200 raises the lift pin 102 to a position
where the inner focus ring 38i is separated from the outer focus
ring 38o. The first shift control requires a small pitch and a high
driving precision. On the other hand, the second shift control
requires a large pitch and does not require the precision as high
as that for the first shift control. Therefore, the driver 101 of
the shift mechanism 200 can adjust the moving speed of the lift pin
102 during the second shift control to be higher than that during
the first shift control.
[0056] <Configuration Examples of Inner Focus Ring 38i and Outer
Gocus Ring 38o>
[0057] Next, a configuration example of the focus ring FR according
to the embodiment will be described with reference to FIGS. 3A to
3D.
[0058] FIG. 3A is a cross-sectional view of the focus ring FR
according to the embodiment. FIG. 3B is a perspective view of the
focus ring FR according to the embodiment. In the example shown in
FIG. 3A, the electrostatic chuck 36 and the stage 12 constitute a
table having an upper surface for mounting thereon the wafer W. The
electrostatic chuck 36 has the wafer support 36c to hold the wafer
W thereon and a peripheral segment 36d surrounding the wafer
support 36c and having through-holes 36f. The peripheral segment
36d has an upper surface lower than that of the wafer support 36c.
A stepped portion 36e having a predetermined height is formed
between the wafer support 36c and the peripheral segment 36d.
[0059] The outer focus ring 38o is disposed while having a
clearance of about 0.1 mm to 0.5 mm between the outer focus ring
38o and the peripheral segment 36d of the electrostatic chuck 36
and between the outer focus ring 38o and the stepped portion 36e of
the electrostatic chuck 36. In a state shown in FIG. 3A, a bottom
surface of the outer focus ring 38o is disposed on the peripheral
segment 36d of the electrostatic chuck 36. Further, an inner
peripheral surface of the outer focus ring 38o faces the stepped
portion 36e of the electrostatic chuck 36. Further, it is
preferable to promote heat conduction between the outer focus ring
38o and the electrostatic chuck 36. Therefore, although it is not
shown, a heat transfer sheet, e.g., a polymer sheet, may be
provided between the outer focus ring 38o and the peripheral
segment 36d to promote the heat conduction.
[0060] The outer focus ring 38o has a recess 38d formed on an inner
side thereof. The recess 38d is a ring-shaped groove having a width
of about 5 mm to 10 mm. The recess 38d is formed near the inner
peripheral surface of the outer focus ring 38o, e.g., at a position
distant from the inner peripheral surface by a distance of about 1
to 2 mm. The recess 38d has a size that allows the inner focus ring
38i to be disposed in the recess 38d. A height of an upper face of
the outer focus ring 38o is lower on the inner side than on the
outer side of the recess 38d. Further, the through-holes 38f are
formed in a bottom surface of the recess 38d to penetrate through
the outer focus ring 38o in the vertical direction.
[0061] The inner focus ring 38i is a ring-shaped member having a
width that allows the inner focus ring 38i to be accommodated in
the recess 38d of the outer focus ring 38o, e.g., a width slightly
smaller than about 5 mm to 10 mm. In one example, a thicknesses of
the inner focus ring 38i and a thicknesses of the outer focus ring
38o may be set such that the height of the upper surface of the
inner focus ring 38i becomes substantially the same as that of the
upper surface of the outer focus ring 38o when the inner focus ring
38i is disposed in the recess 38d. In the state shown in FIG. 3A,
the inner focus ring 38i may be disposed in the recess 38d, and the
bottom surface of the inner focus ring 38i may be in contact with
the upper end(s) of the lift pin(s) 102 extending through the
through-hole(s) 38f.
[0062] As shown in FIG. 3B, both of the inner focus ring 38i and
the outer focus ring 38o are substantially ring-shaped members. The
substantially ring-shaped recess 38d formed on the upper surface of
the outer focus ring 38o also serves as a positioning part for the
inner focus ring 38i. Therefore, the inner focus ring 38i is not
provided with a mark or a structure for positioning, such as a
notch, an orientation flat, or the like.
[0063] FIG. 3C is a top view of the outer focus ring 38o according
to the embodiment. FIG. 3D is a top view showing a state in which
the inner focus ring 38i is disposed at the outer focus ring 38o
according to the embodiment. As shown in FIG. 3C, a plurality of
through-holes 38f (three in the example shown in FIG. 3C) are
disposed in the recess 38d of the outer focus ring 38o at the
substantially equal intervals in the circumferential direction.
When the inner focus ring 38i is disposed in the recess 38d of the
outer focus ring 38o, the through-holes 38f are not seen from
above.
[0064] Referring back to FIG. 3A, the upper face of the outer focus
ring 38o is lower on the radially inner side of the recess 38d than
on the radially outer side of the recess 38d. This is because, in
the configuration shown in FIG. 3A, when the wafer W is held on the
wafer support 36c, the outer periphery of the wafer W overhangs
above the outer focus ring 38o on the inner peripheral side of the
outer focus ring 38o. Further, the inner focus ring 38i has an
inner diameter greater than an outer diameter of the wafer W to
avoid the interference between the inner focus ring 38i and the
wafer W. Further, the upper end of the inner peripheral surface of
the inner focus ring 38i has a chamfered upper inner corner.
[0065] <Vertical Shift of Focus Ring>
[0066] Next, the shift control of the focus ring FR will be
described. FIGS. 4A and 4B explain the first shift control and the
second shift control of the inner focus ring according to the
embodiment, respectively.
[0067] When a new focus ring FR is disposed in the chamber 10,
neither the inner focus ring 38i nor the outer focus ring 38o have
yet to be consumed by the plasma processing. Therefore, as shown in
FIG. 3A, the upper surface of the wafer W held on the wafer support
36c, the upper surface of the inner focus ring 38i, and the upper
surface of the outer focus ring 38o on the radially outer side of
the recess 38d have a predetermined height relationship. In one
example, they have substantially the same height.
[0068] When the plasma processing is performed in the chamber 10,
the focus ring FR is gradually consumed, and the etching uniformity
or the like deteriorates. Therefore, as shown in FIG. 4A, the lift
pin 102 is raised by the first shift control of the shift mechanism
200.
[0069] Then, the inner focus ring 38i is lifted by the lift pin
102, and the upper surface of the wafer W and the upper surface of
the inner focus ring 38i have a predetermined height relationship.
In one example, they have substantially the same height. Here, the
upper surface of the outer focus ring 38o may not have the
predetermined height relationship with the upper surface of the
inner focus ring 38i and the upper surface of the wafer W. However,
the outer focus ring 38o is far from the wafer W compared to the
inner focus ring 38i, and thus is less likely to affect the etching
uniformity.
[0070] Further, the cleaning using plasma may be performed to
remove particles generated in the chamber 10 during the plasma
processing. In the case of removing the foreign substances
deposited between the inner focus ring 38i and the outer focus ring
38o by the plasma, the lift pin 102 can be raised by the first or
the second shift control. This is also applied to modifications to
be described later.
[0071] As the inner focus ring 38i is repeatedly used and consumed,
it is difficult to maintain the etching uniformity. Therefore, the
inner focus ring 38i is disassembled and replaced after the plasma
processing is performed a predetermined number of times. The number
of executions of the plasma processing without replacing the inner
focus ring 38i may be determined depending on the type of plasma
processing, the thickness of the focus ring FR, or the like. Since
the outer focus ring 38o is less likely to affect the etching
uniformity compared to the inner focus ring 38i, the frequency of
the replacement of the outer focus ring 38o is set to be less than
that of the inner focus ring 38i. For example, the outer focus ring
38o may be replaced about once while the inner focus ring 38i is
replaced about three to four times. When the inner focus ring 38i
is replaced, the outer focus ring 38o remains to cover the
peripheral segment 36d of the electrostatic chuck 36. Therefore,
even when the inner focus ring 38i is lifted to perform the
cleaning using the plasma, the electrostatic chuck 36 is covered by
the outer focus ring 38o. Accordingly, the exposure of the
electrostatic chuck 36 to the plasma can be suppressed.
[0072] When the inner focus ring 38i is replaced, the lift pin 102
is raised by the second shift control of the shift mechanism 200 as
shown in FIG. 4B. Then, the inner focus ring 38i is lifted by the
lift pin(s) 102 and separated from the outer focus ring 38o. The
inner focus ring 38i separated from the outer focus ring 38o is
transferred to the outside of the chamber 10 by a robot arm or the
like.
[0073] In accordance with the plasma processing apparatus according
to the embodiment, one shift mechanism 200 can realize both the
position control in raising the focus ring FR during the plasma
processing and the position control in transferring and replacing
the focus ring FR.
[0074] <First Modification>
[0075] The plasma processing apparatus according to the embodiment
can be used to realize a similar position control even in the case
of using a focus ring having another shape. Hereinafter, a focus
ring according to a first modification will be described.
[0076] FIG. 5 is a cross-sectional view of a focus ring FR
according to a first modification. The focus ring FR according to
the first modification has an inner focus ring 38i and an outer
focus ring 38o, as in the case of the focus ring FR according to
the above-described embodiment. However, in the focus ring FR
according to the first modification, the shapes of the inner focus
ring 38i and the outer focus ring 38o are different from those in
the above-described embodiment.
[0077] As shown in FIG. 5, in the focus ring FR according to the
first modification, the outer focus ring 38o has a cutout 38e
instead of the recess 38d. The cutout 38e is formed at the inner
portion of the outer focus ring 38o and has an L-shaped cross
section. The inner focus ring 38i is formed to have a size to be
fittable in the cutout 38e. Unlike the above-described embodiment,
in an initial state, the inner focus ring 38i has an outer portion
having the same height level as that of the upper surface of the
wafer W and an inner portion having an upper surface lower than
that of the outer portion. When the wafer W is held on the wafer
support 36c, the outer periphery of the wafer W overhangs above the
inner portion of the inner focus ring 38i and the outer periphery
of the wafer W faces an inner peripheral surface of the outer
portion of the inner focus ring 38i. A thickness of the inner
portion of the inner focus ring 38i is set such that a
predetermined gap is ensured between the inner portion of the inner
focus ring 38i and the wafer W to prevent the wafer W from being
displaced by the inner portion of the inner focus ring 38i when the
inner focus ring 38i is moved upward by the first shift
control.
[0078] FIGS. 6A and 6B explain the first shift control and the
second shift control of the inner focus ring according to the first
modification, respectively. As shown in FIGS. 6A and 6B, even in
the case of using the focus ring FR according to the first
modification, the first shift control and the second shift control
of the inner focus ring 38i can be realized by using the shift
mechanism 200.
[0079] <Second Modification>
[0080] In the above-described embodiment and the first
modification, the focus ring FR is divided into two parts, i.e.,
the inner focus ring 38i and the outer focus ring 38o. Further, the
plasma processing apparatus performs the first shift control and
the second shift control of the inner focus ring 38i. However, the
present disclosure is not limited thereto, and the focus ring FR
may be formed as one member without being divided into two parts.
For example, the inner focus ring 38i and the outer focus ring 38o
shown in FIG. 3A or FIG. 5 are formed as one member FR. Then, the
shift mechanism 200 controls the position of the upper surface of
the focus ring FR as one member and the transfer of the focus ring
FR.
[0081] In the plasma processing apparatus according to the second
modification, the configurations of the lift pin(s) and the shift
mechanism(s) are the same as those of the above-described
embodiment and the first modification. However, the performance of
the driver (motor or the like) included in the shift mechanism or
the stiffness of the lift pin can be appropriately changed
depending on the size of the focus ring. In the case of
transferring the focus ring through the loading/unloading port 27,
the size of the loading/unloading port 27 is changed in response to
the size of the focus ring.
[0082] In the plasma processing apparatus including the focus ring
according to the second modification, the positional accuracy of
the focus ring can also be improved by using the same shift
mechanism as that of the above-described embodiment.
[0083] In the above-described embodiment and the first and second
modifications, the shift mechanism of the plasma processing
apparatus performs both of the driving and the transfer of the
focus ring. However, the present disclosure is not limited thereto,
and the shift mechanism of the plasma processing apparatus may
perform only the second shift control without performing the first
shift control. On the contrary, the shift mechanism of the plasma
processing apparatus may perform only the first shift control
without performing the second shift control. For example, when the
focus ring is consumed, only the transfer and the replacement of
the focus ring may be performed without adjusting the position of
the upper surface of the focus ring. Alternatively, when the focus
ring is consumed, the position of the upper surface of the focus
ring may be adjusted but the transfer of the focus ring may be
performed by opening the chamber.
[0084] Further, in the above-described embodiment and the first and
second modifications, it is illustrated that the lift pin(s) is
constantly in contact with the bottom surface of the inner focus
ring. However, the present disclosure is not limited thereto, and
the lift pin(s) may not be in constant contact with the focus ring
if the shift mechanism(s) is used only for the second shift control
(transfer) and not used for the first shift control (driving). For
example, the lift pin(s) may be in contact with the inner focus
ring only during the second shift control.
[0085] When the cleaning for removing particles deposited between
the inner focus ring and the outer focus ring is performed, any one
of the first shift control and the second shift control may be
performed.
[0086] <Materials of Parts>
[0087] The respective parts of the focus ring FR are made of Si,
SiO.sub.2, SiC or the like. The outer focus ring 38o and the inner
focus ring 38i may be made of the same material or different
materials.
[0088] <Examples of Dimensions of Components>
[0089] It is assumed that the plasma processing apparatus 5
according to the above-described embodiment is configured to
process a wafer W having a diameter of 300 mm. Further, for
example, a width of the inner focus ring 38i can be adjusted within
a range from about 3 mm to 15 mm. For example, the width and the
diameter of the inner focus ring 38i may be appropriately set under
the condition that an etching rate near the edge portion of the
wafer W is changed while the etching rate of the region of the
wafer excluding the edge portion of the wafer, which includes the
central region of the wafer, is not significantly changed. The
outer diameter of the outer focus ring 38o is, e.g., 360 mm.
[0090] In the case of processing wafers W having different sizes,
the dimensions of the respective components of the plasma
processing apparatus 5 including the focus ring FR are adjusted in
response to the size of the wafer W.
[0091] <Effects of the Embodiment>
[0092] The plasma processing apparatus according to the
above-described embodiment includes the table, the outer focus
ring, the inner focus ring, the lift pins, and the shift
mechanisms. The table has the wafer support to hold the wafer
thereon and the peripheral segment surrounding the wafer support
and having the through-holes, the peripheral segment having an
upper surface lower than that of the wafer support. The outer focus
ring is disposed over the peripheral segment, and has a recess or a
cutout at the inner portion thereof. The recess or cutout has the
through-holes. The inner focus ring is disposed in the recess or
cutout of the outer focus ring. The lift pins respectively extend
through the through-holes of the peripheral segment and the
through-holes of the recess or cutout of the outer focus ring. The
shift mechanisms control the shift of the respective lift pins.
With this configuration, in the plasma processing apparatus of the
embodiment, it is possible to prevent the exposure of the table to
the plasma by disposing the outer focus ring over the peripheral
segment. Further, the plasma processing apparatus of the embodiment
further includes the inner focus ring disposed in the recess or
cutout of the outer focus ring. Therefore, it is not necessary to
form, at the inner focus ring, the notch or the orientation flat
for positioning. Accordingly, the marks for positioning and the
like are not required, which makes it possible to improve the
uniformity of the plasma processing.
[0093] Further, in the plasma processing apparatus of the
embodiment, the focus ring is divided into two parts. Therefore,
the position of the focus ring can be controlled without
excessively increasing the number of components. Moreover, in the
plasma processing apparatus of the embodiment, the shift, i.e., the
elevation, of the inner focus ring is controlled at the position of
the recess or the cutout formed at the inner portion of the outer
focus ring. Therefore, the position of the inner focus ring can be
controlled near the outer periphery of the wafer to be processed,
and the positional accuracy of the focus ring can be improved. For
example, in accordance with the embodiment, the horizontal position
and the height position can be accurately controlled during the
first shift control, and the horizontal position can be accurately
controlled during the second shift control.
[0094] In the plasma processing apparatus, the lift pins may be in
contact with the inner focus ring during the plasma processing. For
example, in the case that the focus ring is raised and, then, the
wafer is processed (the first shift control), the lift pins and the
inner focus ring are always in contact with each other during the
processing of any wafer. For example, a first wafer is subjected to
the plasma processing without raising the focus ring, and a third
wafer is subjected to the plasma processing in a state where the
focus ring is raised. In that case, in the plasma processing
apparatus, the contact state between the lift pins and the inner
focus ring is maintained during the processing of the first wafer
as well as the processing of the third wafer. Therefore, the plasma
processing apparatus according to the embodiment can suppress the
variation between the plasma processings in the amount of heat
conducted through the lift pins during the plasma processing.
Accordingly, in accordance with the embodiment, it is possible to
suppress the variation in the processing uniformity between the
wafers.
[0095] In the plasma processing apparatus, each of the shift
mechanisms may vertically shift the corresponding lift pin with at
least two levels of precision. Alternatively, the precision used
for the first shift control may be applied to that for the second
shift control. In accordance with the embodiment, one shift
mechanism can be used to realize the first shift control for a
precise position control and the second shift control for a
position control at a pitch larger than that for the first shift
control.
[0096] In the plasma processing apparatus, each of the shift
mechanisms may vertically shift the corresponding lift pin with a
first shift precision of about 0.02 mm and with a second shift
precision of about 0.1 mm. The first precision of about 0.02 mm may
be used as the second precision. In accordance with the embodiment,
one shift mechanism can be used to realize the position control of
the inner focus ring and the transfer control of the inner focus
ring.
[0097] Further, in the plasma processing apparatus, each of the
shift mechanisms includes the thruster and the transmitter. The
thruster coaxially connected to the corresponding lift pin. The
transmitter transmits the power of the driver disposed on an axis
different from an axis of the corresponding lift pin to the
thruster. Therefore, even if it is difficult to coaxially arrange
the shift mechanisms with the lift pins, respectively, due to the
restriction in the internal configuration of the plasma processing
apparatus, it is possible to suppress the positional displacements
of the lift pins and improve the positional accuracy of the focus
ring.
[0098] Further, in the plasma processing apparatus, the outer focus
ring is disposed such that the inner peripheral surface and the
bottom surface of the outer focus ring are insulated from the
table. Therefore, in accordance with the embodiment, it is possible
to suppress the exposure of the insulating film of the table to the
plasma through the gaps between the components near the focus ring
during the plasma processing.
[0099] Further, in the plasma processing apparatus, a plurality of
through-holes are disposed at substantially equal intervals in the
circumferential direction of the outer focus ring. Therefore, in
accordance with the embodiment, the positional displacement caused
by the shift of the inner focus ring can be suppressed, and the
positional accuracy of the focus ring can be improved.
[0100] In the plasma processing apparatus, the inner focus ring has
the radial width in a range from 3 mm to 15 mm. Therefore, in
accordance with the embodiment, it is possible to improve the
uniformity of the plasma processing while appropriately adjusting
the radial width of the inner focus ring.
[0101] Further, in the plasma processing apparatus, the upper end
of the inner peripheral surface of the inner focus ring has a
chamfered upper inner corner. Therefore, in accordance with the
embodiment, it is possible to suppress the formation of the gap
between the focus ring and the wafer.
[0102] Further, in the plasma processing apparatus, the height of
the upper face of the inner focus ring is lower at the inner side
of the inner focus ring than that at the outer side of the inner
focus ring. Therefore, in accordance with the embodiment, the
uniformity of the plasma processing can be improved by providing
the focus near the wafer.
[0103] The plasma processing apparatus further includes the table,
the focus ring, the lift pins, and the shift mechanisms. The table
has the wafer support to hold thereon the wafer, and the peripheral
segment surrounding the wafer support and having the through-holes,
the peripheral segment having the upper surface lower than that of
the wafer support. The focus ring is disposed over the upper
surface of the peripheral segment of the table, and the inner
peripheral surface of the focus ring is disposed to face the outer
peripheral surface of the wafer support. The lift pins respectively
extend through the table to raise the focus ring. The shift
mechanisms control the shift of the respective lift pins, with one
of the first shift precision and the second shift precision
different from the first shift precision. Further, in the plasma
processing apparatus, the first shift precision is higher than the
second shift precision. Therefore, the positional accuracy of the
focus ring can be improved by allowing the shift mechanisms to
control the vertical shift of the respective lift pins with two
types of shift precision.
[0104] In the plasma processing apparatus, the first shift
precision is used for raising the focus ring to the plasma
processing position, and the second shift precision is used for
raising the focus ring to the unloading position. Therefore, it is
possible to improve the positional accuracy of the focus ring by
controlling the position of the focus ring with the precision
suitable for the plasma processing and the precision suitable for
the unloading of the focus ring.
[0105] While certain embodiments have been described, these
embodiments have been presented by way of example only, and are not
intended to limit the scope of the disclosures. Indeed, the
embodiments described herein may be embodied in a variety of other
forms. Furthermore, various omissions, substitutions and changes in
the form of the embodiments described herein may be made departing
from the spirit of the disclosures. The accompanying claims and
their equivalents are intended to cover such forms or modifications
as would fall within the scope and spirit of the disclosures.
* * * * *