U.S. patent application number 09/153141 was filed with the patent office on 2001-07-19 for plasma treatment system and method.
Invention is credited to AMANO, HIDEAKI, NAITO, YOKO.
Application Number | 20010008798 09/153141 |
Document ID | / |
Family ID | 26549223 |
Filed Date | 2001-07-19 |
United States Patent
Application |
20010008798 |
Kind Code |
A1 |
NAITO, YOKO ; et
al. |
July 19, 2001 |
PLASMA TREATMENT SYSTEM AND METHOD
Abstract
It is an object to enhance the degree of freedom for the shape
of an obtained magnetic field to enhance the inplane uniformity of
thickness of first and second films when the first and second films
are continuously formed on a substrate to be treated. A main
electromagnetic coil 5 is provided outside of a plasma chamber 21
so as to be movable vertically by a lifting shaft 52. When plasma
is produced in a vacuum vessel 2 by the electron cyclotron
resonance between a microwave and a magnetic field to continuously
deposit a film of a two-layer structure, which comprises an SiOF
film and an SiO.sub.2 film, on a wafer W with the produced plasma,
a process for forming the SiOF film is carried out while the main
electromagnetic coil 5 is arranged so that the lower surface of the
coil 5 is positioned at a lower position than the lower surface of
a transmission window 23 by 139 mm, and a process for forming the
SiO.sub.2 film is carried out while the main electromagnetic coil 5
is arranged so that the lower surface of the coil 5 is positioned
at a lower position than the lower surface of the transmission 23
by 157 mm.
Inventors: |
NAITO, YOKO;
(SAGAMIHARA-SHI, JP) ; AMANO, HIDEAKI; (ZAMA-SHI,
JP) |
Correspondence
Address: |
BEVERIDGE DEGRANDI WEILACHER & YOUNG
1850 M STREET NW
SUITE 800
WASHINGTON
DC
20036
US
|
Family ID: |
26549223 |
Appl. No.: |
09/153141 |
Filed: |
September 14, 1998 |
Current U.S.
Class: |
438/689 ;
257/E21.276; 257/E21.279 |
Current CPC
Class: |
H01J 37/32678 20130101;
H01L 21/02164 20130101; H01J 37/32192 20130101; H01L 21/02131
20130101; H01L 21/02274 20130101; H01L 21/022 20130101; H01L
21/31612 20130101; C23C 16/511 20130101; H01L 21/02211 20130101;
H01L 21/31629 20130101 |
Class at
Publication: |
438/689 |
International
Class: |
H01L 021/311; H01L
021/302 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 16, 1997 |
JP |
270454/1997 |
Sep 11, 1998 |
JP |
276476/1998 |
Claims
What is claimed is:
1. A plasma treatment system for producing plasma in a vacuum
vessel by the electron cyclotron resonance between a microwave and
a magnetic field to treat a substrate to be treated, with the
produced plasma, wherein magnetic field forming means for forming a
magnetic field in said vacuum vessel is provided so as to be
movable in a direction perpendicular to said substrate, and the
shape of the magnetic field formed in said vacuum vessel is
adjusted by moving said magnetic field forming means in said
direction.
2. A plasma treatment system as set forth in claim 1, wherein said
magnetic field forming means comprises first magnetic field forming
means and second magnetic field forming means, which are provided
so as to be relatively movable in a direction perpendicular to said
substrate, and the shape of the magnetic field formed in said
vacuum vessel is adjusted by relatively moving said first and
second magnetic field forming means in said direction.
3. A plasma treatment system as set forth in claim 1, wherein said
magnetic field forming means comprises first magnetic field forming
means provided around a central axis of said substrate so as to
surround a region facing a surface to be treated of said substrate,
and second magnetic field forming means provided around said
central axis so as to surround a region below at least said
substrate, at least one of said first and second magnetic field
forming means being provided so as to be movable in a direction
perpendicular to said substrate, and the shape of the magnetic
field formed in said vacuum vessel is adjusted by moving said at
least one of said first and second magnetic field forming means in
said direction.
4. A plasma treatment system as set forth in claim 1, wherein said
magnetic field forming means has an electromagnetic coil which is
movable in said direction.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of The Invention
[0002] The present invention relates generally to a plasma
treatment system and method for depositing a thin film, such as
SiOF and SiO.sub.2 films, on a substrate to be treated, such as a
semicondductor wafer, by a plasma treatment, such as an ECR
(Electron Cyclotron Resonance) treatment.
[0003] 2. Related Background Art
[0004] An aluminum wiring is typically used as a wiring pattern for
an integrated circuit. An SiO.sub.2 film, an SiOF film or the like
is typically used as an interlayer insulator film for insulating
the aluminum wiring. These films are formed by means of, e.g., a
plasma treatment system for carrying out the ECR plasma treatment
as shown in FIG. 11.
[0005] For example, in this system, a microwave of, e.g., 2.45 GHz,
is supplied to a plasma producing chamber 1A by means of a
waveguide 11, and a magnetic field of, e.g., 875 gausses, is
applied thereto, so that the interaction (the Electron Cyclotron
Resonance) between the microwave and the magnetic field activates a
plasma gas, such as Ar or O.sub.2 gas, and a thin film deposition
gas, such as SiH.sub.4 gas, which is introduced into a thin film
deposition chamber 1B, to produce plasma serving as active species
to deposit a thin film on a semiconductor wafer (which will be
hereinafter referred to as a "wafer") W mounted on a mounting table
12.
[0006] The magnetic field is applied as a downward magnetic field,
which extends from the plasma chamber 1B to the thin film
deposition chamber 1B, by the combination of a main electromagnetic
coil 13, which is provided so as to surround the plasma chamber 1A,
and an auxiliary electromagnetic coil 14, which is provided below
the thin film deposition chamber 1B.
[0007] By the way, the above described plasma treatment system is
designed to adjust the shape of the magnetic field by changing the
currents flowing through the main electromagnetic coil 13 and the
auxiliary electromagnetic coil 14 since the main electromagnetic
coil 13 and the auxiliary electromagnetic coil 14 are fixed to the
aforementioned positions. However, in a case where only such
adjustment of coil current is carried out, when only the current of
one of the electromagnetic coils is adjusted, the shape of the
magnetic field itself is not changed although the intensity of the
magnetic force on the magnetic potential surface of the magnetic
field applied by the adjusted electromagnetic coil is changed.
[0008] For example, a divergent field shown in FIG. 12 can be
obtained by causing the current flowing through the auxiliary
electromagnetic coil 14 to be far smaller than the current flowing
through the main electromagnetic coil 13 or to be zero. However, if
only the current flowing through the main electromagnetic coil 13
is increased without changing the current flowing through the
auxiliary electromagnetic coil 14, only the intensity of the
magnetic force on the magnetic potential surface shown by the
dotted lines in FIG. 12 is increased.
[0009] In addition, when the respective currents of the main
electromagnetic coil 13 and the auxiliary electromagnetic coil 14
are adjusted, the shape of the magnetic field is greatly changed.
For example, when the current flowing through the auxiliary
electromagnetic coil 14 is higher than that in the case of the
divergent field, a mirror field shown in FIG. 13(a) is formed, and
when the direction of the current flowing through the auxiliary
electromagnetic coil 14 is inverted, a cusp field shown in FIG.
13(b) is formed. As described above, the shape of the applied
magnetic field changed by only the adjustment of currents flowing
through the electromagnetic coils is restricted, and the degree of
freedom for the shape of the obtained magnetic field is small.
[0010] By the way, in recent years, a thin film of a two-layer
structure obtained by stacking an SiOF film and an SiO.sub.2 film
is provided in order to obtain a high quality interlayer insulator
film. Such a film is continuously formed in, e.g., the above
described plasma treatment system. However, the conditions in the
processes for depositing these films are different from each other.
If the shape of the magnetic field is optimized for one of the
films, the inplane uniformity of thickness of the other film is
deteriorated.
[0011] Therefore, it is required to adjust the shape of the
magnetic field so as to enhance the inplane uniformity of thickness
of both films. However, as described above, the degree of freedom
for the shape of the magnetic field is small in the present
circumstances, so that it is very difficult to adjust the shape of
the magnetic field. In recent years, the scale down of devices is
accelerated, so that it is required to provide thinner interlayer
insulator films. Therefore, it is conceived that it is more
difficult to adjust the shape of the magnetic field.
SUMMARY OF THE INVENTION
[0012] It is therefore an object of the present invention to
eliminate the aforementioned problems and to provide a plasma
treatment system which can enhance the degree of freedom for the
shape of an obtained magnetic field by providing a movable magnetic
field forming means.
[0013] It is another object of the present invention to provide a
plasma treatment method which can enhance the inplane uniformity of
thickness of first and second films when the first and second films
are continuously deposited on a substrate to be treated.
[0014] In order to accomplish the aforementioned and other objects,
according to one aspect of the present invention, there is provided
a plasma treatment system for producing plasma in a vacuum vessel
by the electron cyclotron resonance between a microwave and a
magnetic field to treat a substrate to be treated, with the
produced plasma, wherein magnetic field forming means for forming a
magnetic field in the vacuum vessel is provided so as to be movable
in a direction perpendicular to the substrate, and the shape of the
magnetic field formed in the vacuum vessel is adjusted by moving
the magnetic field forming means in the direction.
[0015] The magnetic field forming means may comprise first magnetic
field forming means provided around a central axis of the substrate
so as to surround a region facing a surface to be treated of the
substrate, and second magnetic field forming means provided around
the central axis so as to surround a region below at least the
substrate, at least one of the first and second magnetic field
forming means being provided so as to be movable in a direction
perpendicular to the substrate. In this case, the magnetic field
forming means may be an electromagnetic coil.
[0016] According to another aspect of the present invention, there
is provided a plasma treatment method for activating a thin film
deposition gas to produce plasma in a vacuum vessel by the electron
cyclotron resonance between a microwave and a magnetic field to
sequentially deposit first and second films on a substrate to be
treated, the plasma treatment method comprising the steps of:
arranging magnetic forming means for forming a magnetic field in
the vacuum vessel, at a first position to activate a first thin
film deposition gas to produce plasma to form a first film on a
surface to be treated of the substrate; and arranging the magnetic
field forming means at a second position to activate a second thin
film deposition gas to produce plasma to form a second film on the
surface of the first film formed on the substrate.
[0017] According to another aspect of the present invention, there
is provided a plasma treatment method for supplying a microwave
into a vacuum vessel by high-frequency producing means and for
forming a magnetic field in the vacuum vessel by magnetic field
forming means, to produce plasma in the vacuum vessel by the
electron cyclotron resonance between the microwave and the magnetic
field to treat a substrate to be treated, with the produced plasma,
the plasma treatment method comprising: a first step of introducing
the substrate into the vacuum vessel and producing plasma to heat
the substrate; and a second step of activating a thin film
deposition gas to produce plasma in the vacuum vessel to form a
thin fi:lm on the substrate with the produced plasma, wherein the
position of the magnetic field forming means is changed between
positions in the first and second steps to change the shape of the
magnetic field so that a magnetic flux density on the substrate
when plasma is produced in the first step is greater than that in
the second step.
[0018] According to a further aspect of the present invention,
there is provided a plasma treatment method for supplying a
microwave into a vacuum vessel by high-frequency producing means
and for forming a magnetic field in the vacuum vessel by magnetic
field forming means, to produce plasma in the vacuum vessel by the
electron cyclotron resonance between the microwave and the magnetic
field to treat a substrate to be treated, with the produced plasma,
the plasma treatment method comprising: an etching step of
activating an etching gas to produce plasma in the vacuum vessel to
etch the substrate with the plasma; and a post-treatment step of
activating a post-treatment gas to produce plasma in the vacuum
vessel to carry out a post-treatment with the plasma, wherein the
position of the magnetic field forming means is changed between
positions in the etching and post-treatment steps to change the
shape of the magnetic field so that a magnetic flux density on the
substrate when plasma is produced in the post-treatment step is
greater than that in the etching step. This post-treatment includes
a treatment for removing the residual of the etching gas, and a
treatment for ashing the resist film with oxygen gas.
[0019] According to a still further aspect of the present
invention, there is provided a plasma treatment method for
supplying a microwave into a vacuum vessel by high-frequency
producing means and for forming a magnetic field in the vacuum
vessel by magnetic field forming means, to produce plasma in the
vacuum vessel by the electron cyclotron resonance between the
microwave and the magnetic field to treat a substrate to be
treated, with the produced plasma, the plasma treatment method
comprising: an etching step of activating an etching gas to produce
plasma in the vacuum vessel to etch a natural oxide film on the
surface of the substrate with the plasma; and a thin film
deposition step of activating a thin film deposition gas to produce
plasma in the vacuum vessel to form a thin film on the surface of
the substrate with the plasma, wherein the position of the magnetic
field forming means is changed between positions in the etching and
thin film deposition steps to change the shape of the magnetic
field so that a magnetic flux density on the substrate when plasma
is produced in the etching step is greater than that in the thin
film deposition.
[0020] According to the present invention, since the magnetic field
forming means is movable, the degree of freedom for the shape of
the obtained magnetic field is enhanced. In addition, according to
the present invention, when the first and second films are
continuously deposited on the substrate to be treated, the shape of
the magnetic field can be selected so as to enhance the inplane
uniformity of thickness of the first film, and the shape of the
magnetic field can be selected so as to enhance the inplane
uniformity of thickness of the second film. As a result, the
inplane uniformity of thickness of each of the first and second
films continuously deposited can be enhanced.
[0021] Moreover, according to the present invention, since the
magnetic field forming means is movable, the degree of freedom for
the shape of the magnetic field is enhanced, and a plasma treatment
suitable for each of two steps can be carried out by changing the
profile of the magnetic field.
[0022] For example, during the preheat, the quantity of energy
input into the wafer W is regarded as more important than the
uniformity to form a magnetic field so as to increase the quantity
of energy input, and during the thin film deposition, the
uniformity is regarded as more important than the quantity of
energy input to form a magnetic field having a high inplane
uniformity. The shape of the magnetic field is changed by changing
the position of the magnetic field forming means between a position
during the preheat and a position during the thin film deposition
or by changing the current flowing through the electromagnetic coil
of the magnetic field forming means, so that plasma suitable for
the respective treatments can be produced to reduce the preheat
time.
[0023] For example, between the etching step of etching the
substrate to be treated and the post-treatment step or between the
etching step of etching the natural oxide film and the thin film
deposition step, the position of the magnetic field forming means
is changed to change the shape of the magnetic field, so that
plasma suitable for the respective treatments can be produced.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1 is a sectional view of a preferred embodiment of a
plasma treatment system according to the present invention;
[0025] FIG. 2 is a sectional view showing an example of a film of a
two-layer structure formed by the plasma treatment system of FIG.
1;
[0026] FIG. 3 is a characteristic diagram showing the relationship
between the position of a main electromagnetic coil and the inplane
uniformity of thickness;
[0027] FIG. 4 is a characteristic diagram showing the relationship
between the position of a main electromagnetic coil and the thin
film deposition speed;
[0028] FIGS. 5(a) and 5(b) are sectional views showing the
relationship between the position of a main electromagnetic coil
and the shape of a magnetic field;
[0029] FIGS. 6(a) and 6(b) are sectional views showing the
relationship between the position of a main electromagnetic coil
and the shape of a magnetic field in another preferred embodiment
according to the present invention;
[0030] FIG. 7 is a schematic diagram for explaining the intensity
of energy input;
[0031] FIGS. 8(a) and 8(b) are sectional views of another preferred
embodiment according to the present invention;
[0032] FIGS. 9(a) and 9(b) are sectional views of another preferred
embodiment according to the present invention;
[0033] FIG. 10 is a longitudinal section of another preferred
embodiment of a plasma treatment system according to the present
invention;
[0034] FIG. 11 is a sectional view of a conventional plasma
treatment system;
[0035] FIG. 12 is an explanatory drawing showing a divergent field
applied to a conventional plasma treatment system; and
[0036] FIGS. 13(a) and 13(b) are explanatory drawings showing
mirror and cusp fields applied to a conventional plasma treatment
system.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0037] FIG. 1 is a sectional view of a preferred embodiment of a
plasma treatment system according to the present invention. In this
figure, 2 denotes a vacuum vessel of, e.g., aluminum. The vacuum
vessel 2 comprises a plasma chamber 21 for producing plasma, and a
thin film deposition chamber 22 provided below the plasma chamber
21 to be communicated therewith. The vacuum vessel 2 is grounded to
have a zero potential.
[0038] A transmission window 23 of a microwave permeable material
is airtightly provided on the upper end portion of the vacuum
vessel 2 for maintaining the vacuum in the vacuum vessel 2. Outside
of the transmission window 23, a waveguide 24 connected to a
high-frequency power supply (not shown) serving as a plasma
producing high-frequency supply means is provided. A microwave of,
e.g., 2.45 GHz, produced by the high-frequency power supply can be
guided by the waveguide 24 to be introduced from the transmission
window 23 into the plasma chamber 21.
[0039] On the upper side of the side wall defining the plasma
chamber 21, gas nozzles 31 for supplying, e.g., a thin film
deposition gas, are arranged at regular intervals in the
circumferential directions thereof. The gas nozzles 31 are
connected to a plasma gas source (not shown) so as to be able to
uniformly supply plasma gases, such as Ar and O.sub.2 gases, to the
upper portion in the plasma chamber 21. Furthermore, although only
two nozzles 31 are shown in the drawing to simplify the drawing,
two or more nozzles 31 are provided in fact.
[0040] A ring-shaped thin film deposition gas supply portion 32 is
provided in the upper portion of the thin film deposition chamber
22, i.e., in a portion communicating with the plasma chamber 21.
The thin film deposition gas supply portion 32 is formed with a gas
supply port 32a in the inner periphery surface thereof. The thin
film deposition gas supply portion 32 is connected to one end of a
gas supply pipe 33, the other end of which is a thin film
deposition gas source (not shown). Thus, thin film deposition
gases, such as SiH.sub.4 and SiF.sub.4, are jetted from the gas
supply port 32a into the thin film deposition chamber 22.
[0041] In the thin film deposition chamber 22, a mounting table 4
for holding the wafer W is provided on the upper portion of a
cylindrical supporting member 40. The supporting member 40 passes
through the bottom wall of the vacuum vessel 2. The supporting
member 40 is movable vertically with respect to the vacuum vessel 2
while maintaining the airtightness of the vacuum vessel 2. The
mounting table 4 comprises a mounting table body 41, and a
dielectric plate 42 with a built-in heater and a built-in
electrode. The mounting surface serves as an electrostatic chuck.
The electrode is connected to a DC power supply (not shown) for the
electrostatic chuck and to a high-frequency power supply 43 for
applying a bias voltage for drawing ions into the wafer W. An
exhaust pipe 25 is connected to the bottom of the thin film
deposition chamber 22.
[0042] In vicinity of the outer periphery of the side wall defining
the plasma chamber 21, a ring-shaped main electromagnetic coil 5
serving as a first magnetic field forming means is arranged so as
to surround the plasma chamber 21. Below the thin film deposition
chamber 22, a ring-shaped auxiliary electromagnetic coil 6 serving
as a second magnetic field forming means is arranged. These coils 5
and 6 are designed to form a magnetic field B of, e.g., 875
gausses, which extends downward across the thin film deposition
chamber 22. For example, the main electromagnetic coil 5 has an
inside diameter of 350 mm, an outside diameter of 486 mm and a
height of 276 mm, and the auxiliary electromagnetic coil 6 has an
inside diameter of 505 mm, an outside diameter of 605 mm and a
height of 120 mm.
[0043] One end side of a plate supporting member 51 is mounted on
the upper side of the outer periphery of the main electromagnetic
coil 5 at, e.g., two positions. The other end side of the
supporting member 51 is mounted on the outer periphery of a lifting
shaft 52 arranged above the waveguide 24. The main electromagnetic
coil 5 is suspended from the supporting member 51. On the other
hand, the auxiliary electromagnetic coil 6 is provided on a
ring-shaped horizontal supporting plate 61. A part of the
supporting plate 61 is mounted on a lifting shaft 63 by means of a
mounting member 62.
[0044] The lifting shafts 52 and 63 are movable vertically by means
of actuators, respectively. Thus, the main electromagnetic coil 5
is designed to move vertically with respect to the plasma chamber
21 by the vertical movement of the lifting shaft 52, and the
auxiliary electromagnetic coil 6 is designed to move vertically
with respect to the thin film deposition chamber 22 by the vertical
movement of the lifting shaft 63. For example, the waveguide 24 is
formed by connecting one end of a horizontal rectangular waveguide
to the upper side of a conical waveguide. In this case, the
rectangular waveguide is arranged so as not to interfere with the
supporting member 51.
[0045] A method for depositing a film of a two-layer structure
(which will be hereinafter referred to as a "two-layer film"),
which comprises an SiOF film serving as a first film and an
SiO.sub.2 film serving as a second film, on a wafer W serving as a
substrate to be treated, by means of the above described plasma
treatment system will be described below. First, referring to FIG.
2, this two-layer film will be briefly described. This film
comprises an interlayer insulator film 71 of an SiOF film, and a
cap film 72 of an SiO.sub.2 film formed on the surface thereof Such
structure enhances thermal stability.
[0046] The enhanced thermal stability means that the draft of
fluorine (F) is small even at a high temperature. In the two-layer
film, the SiO.sub.2 film is more tightly formed than the SiOF film,
so that F dissociated from the SiOF film can not pass through the
SiO.sub.2 film. Thus, the draft of F is restricted, so that the
thermal stability is enhanced. The thickness of the SiOF film is
about 5000 angstrom, and the thickness of the SiO.sub.2 film is
about 300 angstrom.
[0047] In order to form such a two-layer film, the main
electromagnetic coil 5 is first moved by the lifting shaft 52 so
that the lower surface of the coil 5 is arranged at a lower
position than the lower surface of the transmission window 23 by,
e.g., 139 mm, and the auxiliary electromagnetic coil 6 is moved by
the lifting shaft 63 so that the upper surface of the coil 6 is
arranged at a lower position than the bottom surface of the thin
film deposition chamber 22 by, e.g., 50 mm. On the other hand, a
gate valve (not shown) provided on the side wall of the vacuum
vessel 2 is open, and a wafer W, on which an aluminum wiring has
been formed, is introduced from a load-lock chamber (not shown) by
means of a transport arm (not shown) to be mounted on the mounting
table 4.
[0048] Subsequently, after the gate valve is closed so that the
interior is closed, the internal atmosphere is evacuated to a
predetermined degree of vacuum. Then, plasma gases, e.g., Ar and
O.sub.2 gases, are introduced from the gas nozzles 31 into the
plasma chamber 21 at predetermined flow rates, and a first thin
film deposition gas, e.g., SiF.sub.4 gas, is introduced from the
thin film deposition gas supply portion 32 into the thin film
deposition chamber 22 at a predetermined flow rate. Then, the
pressure in the vacuum vessel 2 is maintained at a process pressure
of 0.25 Pa, and a bias voltage with 13.56 MHz and 2700 W is applied
to the mounting table 4 by means of the high-frequency power supply
43. In addition, the surface temperature of the mounting table 4 is
set to be 200.degree. C.
[0049] On the other hand, a high frequency (microwave) M of 2.45
GHz and 2500 W is introduced from the high frequency power supply
into the plasma chamber 21 via the waveguide 24 and the
transmission window 23. In addition, the currents of the main
electromagnetic coil 5 and the auxiliary electromagnetic coil 6 are
set to be 200 A and 160 A, respectively, to apply a mirror field B.
Thus, in the plasma chamber 21, the interaction between the
magnetic field B and the microwave M induces E (electric
field).times.H (magnetic field) to cause electron cyclotron
resonance to produce plasma. This resonance produces plasma of Ar
gas to enhance the density thereof. Thus, the plasma is stabilized
by Ar gas.
[0050] The produced plasma flows from the plasma chamber 21 into
the thin film deposition chamber 22 as a plasma stream. The
SiF.sub.4 gas supplied to the thin film deposition chamber 22 is
activated by the plasma stream to form active species (plasma). On
the other hand, the plasma ions are drawn into the wafer W by the
bias voltage to scrape off the corners of the pattern (recessed
portion) on the surface of the wafer W to increase the frontage
thereof. While this sputter etching is carried out, an SiOF film is
deposited by the plasma of the thin film deposition gas to be
embedded in the recessed portion. Thus, the interlayer insulator
film 71 of SiOF film is formed.
[0051] Subsequently, the main electromagnetic coil 5 is further
moved so that the lower surface of the coil 5 is positioned at a
lower position than the lower surface of the transmission window 23
by, e.g., 157 mm. At this time, the upper surface of the auxiliary
electromagnetic coil 6 remains being positioned at a lower position
than the bottom surface of the thin film deposition chamber 22 by,
e.g., 50 mm.
[0052] Then, plasma gases, e.g., Ar and O.sub.2 gases, are
introduced into the plasma chamber 21 at predetermined flow rates,
and a second thin film deposition gas, e.g., SiH.sub.4 gas, is
introduced into the thin film deposition chamber 22 at a
predetermined flow rate. Then, the pressure in the vacuum vessel 2
is maintained at a process pressure of, e.g., 0.25 Pa, and a bias
voltage with 13.56 MHz and 2250 W is applied. In addition, the
surface temperature of the mounting table 4 is set to be
200.degree. C.
[0053] On the other hand, a high frequency M of 2.45 MHz and 2250 W
is introduced into the plasma chamber 21, and the currents of the
main electromagnetic coil 5 and the auxiliary electromagnetic coil
6 are set to be 200 A and 200 A, respectively, to apply a mirror
field B to activate SiH.sub.4 gas by the electron cyclotron
resonance. Thus, a cap film 72 of SiO.sub.2 film is formed on the
surface of the interlayer insulator film 71 of SiOF film.
[0054] In such a plasma treatment system, the main electromagnetic
coil 5 and the auxiliary electromagnetic coil 6 are provided so as
to be movable vertically, and the position of the main
electromagnetic coil 5 is changed in the processes for depositing
the SiOF and SiO.sub.2 films in the above described preferred
embodiment, so that it is possible to enhance the inplane
uniformity of thickness of the SiOF and SiO.sub.2 films. It was
measured that the inplane uniformity of thickness of the SiOF film
was about 6%, and the inplane uniformity of thickness of the
SiO.sub.2 film was about 5%.
[0055] An example of experiment carried out to confirm the
relationship between the inplane uniformity of thickness and the
position of the electromagnetic coil will be described below. In
this example, the plasma treatment system shown in FIG. 1 was used.
In this system, Ar and O.sub.2 gasses were introduced into the
plasma chamber 21 at flow rates of 350 sccm and 200 sc cm,
respectively, and SiF.sub.4 gas was supplied to the plasma chamber
21 at a flow rate of 140 sccm. In addition, a high frequency power
of 2500 W, a bias power of 2700 W and a thin film deposition
temperature of 200.degree. C. were applied to deposit an SiOF film
having a thickness of 5000 angstrom on the wafer on the same
process conditions as those in the above described preferred
embodiment.
[0056] In this case, while the upper surface of the auxiliary
electromagnetic coil 6 was arranged at a lower position than the
bottom surface of the thin film deposition chamber 22 by 25 mm, the
main electromagnetic coil 5 was arranged at different positions to
deposit thin films, and the deposition speed and the inplane
uniformity of the obtained SiOF films were examined. The inplane
uniformity was measured by the fully automatic spectral
ellipsometric measuring method, and the calculation thereof was
carried out by calculating the values of 3 .sigma. with respect to
49 points in plane.
[0057] In addition, Ar and O.sub.2 gases were introduced into the
plasma chamber 21 at flow rates of 200 sccm and 104 sccm,
respectively, and SiH.sub.4 was supplied thereto at a flow rate of
80 sccm. A high frequency power of 2250 W, a bias power of 2250 W
and a thin film deposition temperature of 200.degree. C. were
applied to deposit an SiO.sub.2 film having a thickness of 5000
angstrom on a wafer on the same process conditions as those in the
above described preferred embodiment. Thus, the same experiment was
ca li med out.
[0058] These results are shown in FIGS. 3 and 4. FIG. 3 shows the
inplane uniformity of thickness of the SiOF and SiO.sub.2 films by
.diamond-solid. and , respectively, and FIG. 4 shows the deposition
speed thereof. In these drawings, the position of the main
electromagnetic coil 5 on abscissa is shown by the distance between
the lower surface of the coil 5 and the lower surface of the
transmission window 23.
[0059] It was ascertained by these results that, by moving the main
electromagnetic coil 5, the inplane uniformity of thickness of the
SiOF film changed between 6% and 21% and the inplane uniformity of
thickness of SiO.sub.2 film changed between 5% and 15%. Thus, it
was ascertained that there were coil positions at which the SiOF
and SiO.sub.2 films had the highest inplane uniformity of
thickness, the coil positions being different in accordance with
the kind of film.
[0060] It was ascertained that, for example, when the SiOF film was
deposited, the optimum position of the main electromagnetic coil 5
was a position at which the lower surface of the coil 5 was
arranged at a lower position than the lower surface of the
transmission window 23 by 139 mm, and when the SiO.sub.2 film was
deposited, the optimum position of the main electromagnetic coil 5
was a position at which the lower surface of the coil 5 was
arranged at a lower position than the lower surface of the
transmission window 23 by 157 mm, so that the inplane uniformity of
thickness of the respective films was enhanced to about 5 to 6% by
arranging the coil 5 to the optimum positions in the respective
processes. It was also ascertained that the deposition speed was
not deteriorated even if the main electromagnetic coil 5 was
arranged at the optimum position.
[0061] Thus, it is guessed that the reason why the optimum
positions of the electromagnetic coil for enhancing the inplane
uniformity of thickness exist is as follows. It is conceived that
the shape of the applied magnetic field is different in the
respective deposition process since the position of the main
electromagnetic coil 5 is different in the respective deposition
processes in the above described preferred embodiment. For example,
when the position of the auxiliary electromagnetic coil 6 is fixed
and the position of the main electromagnetic coil 5 is varied to
form a mirror field as shown in FIG. 3, FIG. 5(a) shows the shape
of the magnetic field when the main electromagnetic coil 5 is
arranged at a higher position, and FIG. 5(b) shows the shape of the
magnetic field when the main electromagnetic coil 5 is arranged at
a lower position. Thus, it is conceived that the shape of the
obtained magnetic field is changed in accordance with the position
of the main electromagnetic coil 5.
[0062] These drawings will be briefly described. In these drawings,
L1 denotes the central position of the main electromagnetic coil 5
in vertical directions, L2 denotes the central position of the
auxiliary electromagnetic coil 6 in vertical directions, and L3
denotes a position at which the horizontal component of the
magnetic field (the intensity of the magnetic field in horizontal
directions) Br is substantially zero. In FIG. 5(a), the distance A
between L1 and L3 is substantially equal to the distance B between
L2 and L3, and in FIG. 5(a), the distance A between L1 and L3 is
substantially equal to the distance B between L2 and L3. As can be
clearly seen from these drawings, the position of L3 is positioned
in vicinity of the upper surface of the mounting table 4 in the
case of FIG. 5(a) in which the main electromagnetic coil 5 is
positioned at a higher position, and the position of L3 is
positioned in vicinity of the central portion of the mounting table
4 in the case of FIG. 5(b) in which the main electromagnetic coil 5
is positioned at a lower position, so that the position of L3 of
the obtained magnetic field is lower than in the case of FIG.
5(a).
[0063] In the case of the SiOF film, SiF.sub.4 gas serving as a
thin film deposition gas is dissociated to an active species of
SiF.sub.3 (SiF.sub.3*) and an active species of F (F*) as shown by
the following formula (1). In the case of the SiO.sub.2 film,
SiH.sub.4 gas serving as the thin film deposition gas is
dissociated to an active species of SiH.sub.3 (SiH.sub.3*) and an
active species of H (H*) as shown by the follo wing formula
(2).
SiF.sub.4.fwdarw.SiF.sub.3*+F* (1)
SiH.sub.4.fwdarw.SiH.sub.3*+H* (2)
[0064] Thus, although the active species obtained by activation is
different in accordance with the kind of thin film deposition gas,
the weight and life of the active species are different in
accordance with the kind of the active species, so that it is
conceived that, by this difference, the scattering way of the
different active species is different even if the shape of the
magnetic field is same. Therefore, it is guessed that there is the
optimum shape to enhance the inplane uniformity of thickness in
accordance with the kind of the thin film deposition gas.
[0065] Thus, in this preferred embodiment, the shape of the
magnetic field is changed by moving the main electromagnetic coil
5, so that the degree of freedom for the shape of the obtained
magnetic field is increased by combining the adjustment of the coil
position with the adjustment of the coil current. Thus, the optimum
shape of the magnetic field to enhance the inplane uniformity of
thickness in the respective processes for depositing the SIOF and
SiO.sub.2 films can be obtained by the adjustment of the coil
position and coil current,
[0066] Therefore, if the coil position and coil current for
obtaining the optimum shape of the magnetic field are previously
determined by experiment, even if different kinds of films are
continuously formed by means of the same plasma treatment system,
it is possible to easily obtain films, each having a high inplane
uniformity of thickness.
[0067] Subsequently, refining to FIGS. 6(a), 6(b) and 7, another
preferred embodiment of the present invention will be described
below. In this preferred embodiment, the present invention is
applied to preheat. The term "preheat" means the pretreatment for
the thin film deposition. For example, when a thin film deposition
gas is introduced to carry out the thin film deposition immediately
after a wafer W of ordinary temperature is mounted on the mounting
table, although the wafer W is heated by plasma, the temperature
thereof is not raised to a predetermined temperature which is set
when the thin film deposition is carried out, so that the thin film
deposition proceeds at a lower temperature than a predetermined
temperature. Thus, a thin film having a bad quality is formed. In
order to prevent this, the preheat is carried out. Specifically,
after the wafer W is mounted on the mounting table, before the thin
film deposition gas is introduced, plasma is produced, and the
wafer W is heated to a predetermined temperature, e.g., a thin film
deposition temperature, by the produced plasma.
[0068] A series of processes for forming an interlayer insulator
film of a CF film on a wafer W by means of the above described
plasma treatment system will be described below. First, the
positions of the main electromagnetic coil 5 and the auxiliary
electromagnetic coil 6 are set to, e.g., positions shown in FIG.
6(a) so as to obtain the shape of the magnetic field in which the
lines of magnetic force are converged on the central portion of the
wafer W.
[0069] Then, the wafer W is fed into the vacuum vessel 2 to be
mounted on the mounting table 4 to carry out preheat serving as a
first step (see FIG. 6(a)). That is, Ar gas is introduced into the
first vacuum chamber 21 at a predetermined flow rate. In addition,
under a predetermined process pressure, a microwave of 2.45 GHz and
2.8 kW is applied from the high-frequency power supply (not shown),
and a bias power of 13.56 MHz and 0 kW is applied to the mounting
table 4 from the high-frequency power supply 43. The surface
temperature of the mounting table 4 is set to be always, e.g.,
80.degree. C. Then, Ar gas is activated by the electron cyclotron
resonance to produce plasma, by which the wafer W is heated. Until
the temperature of the wafer W reaches about 400.degree. C., the
plasma is produced for about 20 seconds to carry out preheat.
[0070] Subsequently, the positions of the main electromagnetic coil
5 and the auxiliary electromagnetic coil 6 are set to, e.g.,
positions shown in FIG. 6(b) so as to obtain the shape of the
magnetic field in which the outside magnetic field is widened in
the plane of the wafer W so that the lines of magnetic force is
substantially uniform in the plane of the wafer W. Thus, a CF film
is deposited as a second step. In this case, for example, the
position of the auxiliary electromagnetic coil 6 is not changed and
the position of the main electromagnetic coil 5 is moved upwards to
form the aforementioned shape of magnetic field.
[0071] The deposition of the CF film is carried out by introducing
a plasma gas, e.g., Ar, and thin film deposition gases, e.g.,
C.sub.4F.sub.8 and C.sub.2H.sub.4 gases, into the vacuum vessel 2
at predetermined flow rates, respectively, and by applying a
microwave of 2.45 GHz and 2.7 kW and a bias voltage of 13.56 MHz
and 2.0 kW under a predetermined process pressure to activate the
gases to produce plasma by the electron cyclotron resonance.
[0072] In such a preferred embodiment, since the position of the
main electromagnetic coil 5 is changed between a position during
the preheat and a position during the thin film deposition to
produce plasma suitable for the respective treatments, it is
possible to reduce the time required for the preheat. That is,
during the preheat, the quantity of energy input into the wafer W
is regarded as more important than the uniformity to form a
magnetic field so as to increase the quantity of energy input, and
during the thin film deposition, the uniformity is regarded as more
important than the quantity of energy input to form a magnetic
field having a high inplane uniformity.
[0073] The magnetic field is formed by the main electromagnetic
coil 5 and the auxiliary electromagnetic coil 6. The magnetic field
formed by the main electromagnetic coil 5 has a shape which is
widened outside as extending downwards, and the magnetic field
formed by the auxiliary electromagnetic coil 6 has a shape which is
widened outside as extending upwards, so that the outside widened
magnetic field formed by the main electromagnetic coil 5 is
narrowed inside by the auxiliary electromagnetic coil 6. As a
result, the magnetic field formed by the main electromagnetic coil
5 and the auxiliary electromagnetic coil 6 has a shape of a mirror
field which is gradually expanded as extending downwards and
gradually narrowed as further extending downwards. As described
above, the plasma is produced by the interaction between electric
and magnetic fields, and the shape thereof depends on the shape of
the magnetic field.
[0074] In the above described example, the main electromagnetic
coil 5 is moved downwards during the preheat, so that the position
of the most expanded portion of the magnetic field is positioned
below the surface of the wafer, and the magnetic field near the
surface of the wafer is narrowed. In this case, the lines of
magnetic force are converged in vicinity of the central portion of
the wafer W, so that the magnetic flux density is great in vicinity
of the central portion of the wafer W.
[0075] On the other hand, during the thin fi ln deposition, the
position of the main electromagnetic coil 5 is moved to a higher
position than that during the preheat, so that the surface of the
wafer is positioned in vicinity of the most expanded portion of the
magnetic field. Therefore, the outside magnetic field is extended
in vicinity of the surface of the wafer to some extent. In this
case, although the lines of magnetic force are substantially
uniform in the inplane of the wafer W, the magnetic flux density is
decreased.
[0076] The density of plasma produced herein (the intensity of
energy input into the wafer W) is in proportional to the magnetic
flux density. Therefore, as shown in FIG. 7, during the thin film
deposition, although the density of plasma is substantially uniform
in the inplane of the wafer W, the total quantity of energy input
is decreased. On the other hand, during the preheat, although the
intensity of energy input of the produced plasma is uniform in the
inplane of the wafer W, the total quantity is far greater than that
during the thin film deposition.
[0077] Thus, in this method, the positions of the main
electromagnetic coil 5 and the auxiliary electromagnetic coil 6 are
controlled to form a magnetic field having a greater quantity of
energy input of the wafer W during the preheat and to form a
magnetic field having a high inplane uniformity during the thin
film deposition. Therefore, for example, after the wafer W of
ordinary temperature is introduced into the vacuum vessel 2, the
wafer W is mounted on and vacuum held to the mounting table 4. At
this time, the time (preheat time) required for the wafer W, the
temperature of which has been raised to about 80.degree. C., to be
heated to about 400.degree. C. serving as a thin film deposition
temperature may be 20 seconds.
[0078] Conventionally, the preheat and thin film deposition are
carried out by producing plasma which is considered being most
suitable for the thin film deposition. In this case, the time
required for the temperature of a wafer W being 80.degree. C. to be
raised to 400.degree. C. serving as the thin film deposition
temperature is about 60 seconds. Therefore, in this preferred
embodiment, the preheat time can be remarkably reduced in
comparison with the conventional method, so that it is possible to
improve the total throughput.
[0079] In addition, in the above described example, while the bias
power has been 0 kW in order to decrease damage to a device in an
uniform specification, a fine bias power of about 300 W may be
applied to carry out a higher speed preheat during the thin film
deposition for a device, to which damage is small. In this case,
the preheat time can be further reduced.
[0080] Referring to FIG. 8, another preferred embodiment of the
present invention will be described below. In this preferred
embodiment, the present invention is applied to etching. An example
of etching in this preferred embodiment will be described. An
aluminum (Al) layer 82 is formed on the upper surface of a
substrate 81 of, e.g., SiO.sub.2 film, and a pattern of a resist
film 83 is formed on the upper surface of the Al layer 82 to etch
the Al layer 82 with an etching gas, e.g., Cl.sub.2 gas.
[0081] Specifically, such etching will be described. First, as
shown in FIG. 8(a), a step of etching the Al layer 82 with Cl.sub.2
gas is carried out by means of the above described plasma treatment
system. That is, e.g., the positions of the main electromagnetic
coil 5 and the auxiliary electromagnetic coil 6 are set to be,
e.g., positions shown in FIG. 8(a) so as to obtain the shape of a
magnetic field in which the lines of magnetic force are
substantially uniform in the plane of the wafer W.
[0082] Then, plasma gases, e.g., Ar and Cl.sub.2 gases, are
introduced at predetermined flow rates, respectively, and a bias
voltage of 13.56 MHz and a microwave of 2.45 GHz are introduced
under a predetermined process pressure. Then, Cl.sub.2 gas is
activated to produce plasma by the electron cyclotron resonance at
a process pressure of 0.5 Pa to etch the Al layer 82 with the
produced plasma. That is, while plasma ions are drawn into the Al
layer 82 by the bias voltage, the corners of pattern on the surface
are scraped off to extend the frontage thereof to carry out the
sputter etching.
[0083] Thereafter, the positions of the main electromagnetic coil 5
and the auxiliary electromagnetic coil 6 are set to be, e.g.,
positions shown in FIG. 8(b), so as to obtain the shape of a
magnetic field in which the lines of magnetic force are converged
on the central portion of the wafer W. That is, for example, the
position of the main electromagnetic coil 5 is moved downwards
without moving the auxiliary electromagnetic coil 6. Then, a
post-treatment step of removing the residual 85 of Cl.sub.2 gas,
which remains in a groove 84 formed by etching, with a
post-treatment gas is carried out. That is, a plasma gas, e.g., Ar
gas, and a post-treatment gas, e.g., NH.sub.3 gas, are introduced
at predetermined flow rates, respectively, and the NH.sub.3 gas is
activated to produce plasma by the electron cyclotron resonance at
a process pressure of 133 Pa to reduce and thermally evaporate Cl
being the residual 85 to remove Cl.
[0084] In such a preferred embodiment, the shape of the magnetic
field is changed by changing the positions of the main
electromagnetic coil 5 and the auxiliary magnetic coil 6 between
the positions during the etching of the Al layer 82 and the
positions during the post-treatment, so that plasma suitable for
the respective treatments are produced. Therefore, it is possible
to uniformly carry out etching, and it is possible to reduce the
time required for the post-treatment.
[0085] That is, during the etching, the magnetic field is a mirror
field in which the lines of magnetic force are substantially
uniform in the plane of the substrate 81 as shown in FIG. 8(a) as
described in the above described preferred embodiment. In such a
magnetic field, the density of plasma is substantially uniform in
the plane of the substrate 81, so that it is possible to uniformly
carry out etching.
[0086] On the other hand, during the post-treatment, the position
of the main electromagnetic coil 5 is positioned at a lower
position than that during the etching, so that the magnetic field
is a mirror field in which the lines of magnetic force are
converged on a portion in vicinity of the central portion of the
substrate 81 shown in FIG. 8(b) as described in the above preferred
embodiment. In such a magnetic field, the density of plasma is far
greater than that during the etching. However, when the density of
plasma is increased, the quantity of active species is increased,
so that the treatment for removing the residual easily proceeds.
Thus, it is possible to reduce the time required for the
post-treatment.
[0087] Referring to FIGS. 9(a) and 9(b), another example of the
present invention applied to etching Will be described below. An
example of etching in this preferred embodiment will be described.
For example, an SiO.sub.2 film 87 is formed on the upper surface of
a substrate 86 of, e.g., a polysilicon, and a resist film 88 is
formed on the upper surface of the SiO.sub.2 film 87. Then, the
SiO.sub.2 film 87 is etched with an etching gas, e.g., a compound
gas of C (carbon) and F (fluorine), such as C.sub.4F.sub.8 gas,
(which will be hereinafter referred to as a "CF gas").
[0088] Such etching will be specifically described. First, as shown
in FIG. 9(a), a step of etching the SiO.sub.2 film 87 with a CF gas
is carried out by means of the above described plasma treatment
system. That is, the positions of the main electromagnetic coil 5
and the auxiliary electromagnetic coil 6 are set so as to be able
to obtain the shape of a magnetic field in which the lines of
magnetic force are substantially uniform in the plane of the wafer
W. Then, a plasma gas, e.g., Ar gas, and a CF gas are introduced at
predetermined flow rates, respectively. In addition, a bias voltage
of 13.56 MHz and a microwave of 2.45 GHz are introduced at a
process pressure of 0.8 Pa to activate the CF gas to produce plasma
by the electron cyclotron resonance to each the SiO.sub.2 film with
the produced plasma. Thereafter, as shown in FIG. 9(b), a
post-treatment step of ashing the resist film 88 with O.sub.2 gas
is carried out. That is, the positions of the main electromagnetic
coil 5 and the auxiliary electromagnetic coil 6 are set so as to
obtain the shape of a magnetic field in which the lines of magnetic
force is converged at the center of the wafer W. Then, a plasma
gas, e.g., Ar gas, and O.sub.2 gas serving as a post-treatment gas
are introduced at predetermined flow rates to activate the O.sub.2
gas to produce plasma at a process pressure of 1.5 Pa by the
electron cyclotron resonance, and the resist film 88 is removed by
the produced plasma as H.sub.2O and CO.sub.2.
[0089] In such a preferred embodiment, a magnetic field having
lines of magnetic force, which are substantially uniform in the
plane of the substrate 86, is formed during the etching, and a
magnetic field having lines of magnetic force, which are converged
in vicinity of the central portion of the substrate 86, is formed
during the ashing. Therefore, during the etching, substantially
uniform plasma is produced in the plane of the substrate 86, so
that it is possible to achieve uniform etching. On the other hand,
during the ashing, the density of plasma can be greater than that
during the etching, so that the ashing time can be reduced.
[0090] Moreover, when, e.g., a polysilicon film is formed on the
surface of a wafer W, on which, e.g., a p-type or n-type silicon
film is formed, the present invention can be applied to a process
for etching a natural oxide film formed on the wafer W and then
forming the polysilicon film. In this case, a magnetic field, in
which the lines of magnetic force are converged in vicinity of the
central portion, is first formed to etch the natural oxide film,
which is formed on the surface of the silicon film, with, e.g., a
CF gas, and then, a mirror field capable of obtaining a uniform
density of plasma on the surface of the wafer W is formed to carry
out the treatment. Also in this case, the pretreatment, which is a
treatment for removing the natural oxide film, can be carried out
for a short time.
[0091] In the plasma treatment system for carrying out the method
of the present invention, a main electromagnetic coil 9 as shown
in, e.g., FIG. 10, may be used. This main electromagnetic coil 9 is
divided into, e.g., three electromagnetic coils 9A, 9B and 9C,
which are movable vertically by motor drive parts M1, M2 and M3 via
lifting shafts 91, 92 and 93. Other constructions are the same as
those of the plasma treatment system shown in FIG. 1.
[0092] To change the magnetic field as described above is to
control the plasma treatment for the substrate by changing the
profile of the magnetic field during the treatment. The change of
the profile of the magnetic field during the treatment allows the
control for converging the magnetic field at the center and
diffusing the magnetic field to the periphery with respect to the
treatment results in the plane of the substrate.
[0093] According to the present invention, a permanent magnet or
the like may be used as a magnetic field forming means in place of
the electromagnetic coil. As the first and second films, e.g., an
SiOF film, an SiO.sub.2 film based on the CVD, and so forth may be
stacked, or a fluorine containing carbon, an SiN film and so forth
may be stacked. Moreover, in the etching of the Al layer 82, plasma
may be produced without adding NH.sub.3 gas, and other treatments
may be carried out by the produced plasma. Also in this case, the
positions of the main electromagnetic coil 5 and the auxiliary
electromagnetic coil 6 may be adjusted so as to increase the
quantity of energy input of plasma into the substrate.
[0094] According to the present invention, in the adjustment of the
magnetic field forming means, the position of the first magnetic
field forming means may be fixed, and the position of the second
magnetic field forming means may be changed. Alternatively, both of
the first and second magnetic field forming means may be
changed.
[0095] Moreover, the present invention should not be limited to the
application to the production of plasma by the ECR. For example,
the present invention may be applied when plasma is produced by a
method called ICP (Inductive Coupled Plasma), i.e., a method for
supplying an electric field and a magnetic field to a treatment gas
from a coil wound onto a dome-shaped vessel. Moreover, the present
invention may be applied when plasma is produced by the interaction
between a helicon wave of, e.g., 13.56 MHz, which is called helicon
liquid plasma, and a magnetic field applied by a magnetic coil, or
when plasma is produced by applying a magnetic field which is
substantially parallel to two parallel cathodes, which is called
magnetron plasma, or when plasma is produced by applying a
high-frequency power between facing electrodes called parallel
plates.
* * * * *