 |
Claims  |
|
|
What is claimed is:
1. A microwave plasma processing apparatus comprising:
a plasma generation chamber of which periphery is separated from ambient air by a dielectric member;
microwave introduction means utilizing an endless annular wave guide tube provided around said plasma generation chamber and having plural slots;
a processing chamber connected to said plasma generation chamber;
support means for a substrate to be processed, provided in said processing chamber;
gas introduction means for said plasma generation chamber and said processing chamber; and
evacuation means for said plasma generation chamber and said processing chamber;
wherein a circumferential length L.sub.g of said endless annular wave guide tube, a wavelength .lambda..sub.g of the microwave in said endless annular wave guide tube, a circumferential length L.sub.s of said dielectric member and a wavelength
.lambda..sub.s of the surface wave propagating in said dielectric member substantially satisfy a relationship:
wherein n is 0 or a natural number.
2. A microwave processing apparatus according to claim 1, further comprising magnetic field generation means.
3. A microwave processing apparatus according to claim 2, wherein said magnetic field generation means is adapted to control the magnetic field in the vicinity of the slots at a magnetic flux density approximately equal to 3.57.times.10.sup.-11
(T/Hz) times of a frequency of the microwave.
4. A microwave processing apparatus according to claim 1, wherein said substrate support means is provided at a position distant from a generation area of said plasma.
5. A microwave processing apparatus according to claim 1, further comprising means for irradiating the substrate to be processed with optical energy.
6. A microwave processing apparatus according to claim 5, wherein said optical energy includes ultraviolet light.
7. A microwave processing apparatus according to claim 1, further comprising high frequency supply means connected to said support means.
8. A microwave processing apparatus according to claim 1, wherein said wave guide tube is provided therein with a first dielectric material.
9. A microwave processing apparatus according to claim 1, wherein said wave guide tube is provided therein with a second dielectric material which is different from said first dielectric material.
10. A microwave plasma processing apparatus comprising:
a plasma generation chamber of which periphery is separated from ambient air by a dielectric member;
microwave introduction means utilizing a endless annular wave guide tube provided around said plasma generation chamber and having plural slots;
a processing chamber connected to said plasma generation chamber;
support means for a substrate to be processed, provided in said processing chamber;
gas introduction means for said plasma generation chamber and said processing chamber; and
evacuation means for said plasma generation chamber and said processing chamber;
wherein a central radius R.sub.g of said endless annular wave guide tube, a wavelength .lambda..sub.g of the microwave in said endless annular wave guide tube, a central radius R.sub.s of the dielectric member and a wavelength .lambda..sub.s of
the surface wave propagating in said dielectric member substantially satisfy a relationship:
wherein n is 0 or a natural number.
11. A microwave processing apparatus according to claim 10, further comprising a magnetic field generation means.
12. A microwave processing apparatus according to claim 11, wherein said magnetic field generation means is adapted to control the magnetic field in the vicinity of the slots at a magnetic flux density approximately equal to
3.57.times.10.sup.-11 (T/Hz) times of a frequency of the microwave.
13. A microwave processing apparatus according to claim 10, wherein said substrate support means is so provided as to place the substrate at a position distant from a generation area of said plasma.
14. A microwave processing apparatus according to claim 10, further comprising means for irradiating the substrate to be processed with optical energy.
15. A microwave processing apparatus according to claim 14, wherein said optical energy includes ultraviolet light.
16. A microwave processing apparatus according to claim 10, further comprising high frequency supply means connected to said support means.
17. A microwave processing apparatus according to claim 10, wherein said wave guide tube is provided therein with a first dielectric material.
18. A microwave processing apparatus according to claim 10, wherein said wave guide tube is provided therein with a second dielectric material which is different from said first dielectric material.
19. A microwave plasma processing apparatus comprising:
a plasma generation chamber separated from ambient air by a first dielectric material;
a processing chamber connected to said plasma generation chamber;
means for supporting a substrate to be processed, provided in said processing chamber;
microwave introduction means utilizing an endless annular wave guide tube provided around said plasma generation chamber and provided with plural slots;
means for introducing gas for said plasma generation chamber and said processing chamber; and
evacuation means for said plasma generation chamber and said processing chamber;
wherein an interior of said annular wave guide tube is filled with a second dielectric material which is the same as or different from said first dielectric material.
20. A microwave processing apparatus according to claim 19, wherein a ratio of dielectric constants of said first and second dielectric materials is approximately equal to a reciprocal of a square of the ratio of a circumferential lengths of
said first and second dielectric materials.
21. A microwave processing apparatus according to claim 19, further comprising a magnetic field generation means.
22. A microwave processing apparatus according to claim 21, wherein the magnetic field in the vicinity of the slots has a magnetic flux density approximately equal to 3.57.times.10.sup.-11 (T/Hz) times of a frequency of the microwave.
23. A microwave processing apparatus according to claim 19, wherein said substrate support means is provided at a position distant from a generation area of said plasma.
24. A microwave processing apparatus according to claim 19, further comprising means for irradiating the substrate to be processed with optical energy.
25. A microwave processing apparatus according to claim 19, further comprising high frequency supply means connected to said support means.
26. A microwave plasma processing method utilizing a microwave plasma processing apparatus comprising a plasma generation chamber of which periphery is separated from ambient air by a dielectric member; microwave introduction means utilizing an
endless annular wave guide tube provided around said plasma generation chamber and provided with plural slots; a processing chamber connected to said plasma generation chamber; support means for a substrate to be processed; provided in said processing
chamber; gas introduction means for said plasma generation chamber and said processing chamber; and evacuation means for said plasma generation chamber and said processing chamber; adapted to effect a plasma process on said substrate by selecting a
circumferential length L.sub.g of said endless annular wave guide tube, a wavelength .lambda..sub.g of the microwave in said endless annular wave guide tube, a circumferential length L.sub.s of said dielectric member and a wavelength .lambda..sub.s of
the surface wave propagating in said dielectric member so as to substantially satisfy a relationship:
wherein n is 0 or a natural number.
27. A microwave processing method according to claim 26, wherein the plasma process is effected under application of a magnetic field.
28. A microwave processing method according to claim 27, wherein said magnetic field is so controlled that the magnetic field in a vicinity of the slots is at a magnetic flux density approximately equal to 3.57.times.10.sup.-11 (T/Hz) times of a
frequency of the microwave.
29. A microwave processing method according to claim 26, comprising a step of placing said substrate on said substrate support means at a position distant from a generation area of said plasma.
30. A microwave processing method according to claim 26, wherein the plasma process is effected under irradiation of the processed substrate with optical energy.
31. A microwave processing method according to claim 30, wherein said optical energy includes ultraviolet light.
32. A microwave processing method according to claim 26, wherein the plasma process is effected by supplying high frequency to said support means.
33. A microwave processing method according to claim 26, wherein a interior of said wave guide tube is filled with a first dielectric material.
34. A microwave processing method according to claim 26, wherein an interior of said wave guide tube is filled with a second dielectric material which is different from said first dielectric material.
35. A microwave processing method according to claim 26, wherein said plasma process is film forming.
36. A microwave processing method according to claim 26, wherein said plasma process is etching.
37. A microwave processing method according to claim 26, wherein said plasma process is ashing.
38. A microwave plasma processing method utilizing a microwave plasma processing apparatus comprising a plasma generation chamber of which periphery is separated from ambient air by a dielectric member; microwave introduction means utilizing a
cylindrical endless annular wave guide tube provided around said plasma generation chamber and provided with plural slots; a processing chamber connected to said plasma generation chamber; support means for a substrate to be processed; provided in the
processing chamber; gas introduction means for said plasma generation chamber and said processing chamber, and evacuation means for said plasma generation chamber and said processing chamber, adapted for effecting a plasma process by selecting a central
radius R.sub.g of said endless annular wave guide tube, a wavelength .lambda..sub.g of the microwave in said endless annular wave guide tube, a central radius R.sub.s of said dielectric member and a wavelength .lambda..sub.s of the surface wave
propagating in said dielectric member so as to substantially satisfy a relationship:
wherein n is 0 or a natural number.
39. A microwave processing method according to claim 38, wherein the plasma process is effected under application of a magnetic field.
40. A microwave processing method according to claim 39, wherein said magnetic field is so controlled that the magnetic field in a vicinity of the slots is at a magnetic flux density approximately equal to 3.57.times.10.sup.-11 (T/Hz) times of a
frequency of the microwave.
41. A microwave processing method according to claim 38, comprising a step of placing said substrate on said substrate support means at a position distant from a generation area of said plasma.
42. A microwave processing method according to claim 38, wherein the plasma process is effected under irradiation of the processed substrate with optical energy.
43. A microwave processing method according to claim 42, wherein said optical energy includes ultraviolet light.
44. A microwave processing method according to claim 38, wherein the plasma process is effected by supplying high frequency to said support means.
45. A microwave processing method according to claim 38, wherein an interior of said wave guide tube is filled with a first material.
46. A microwave processing method according to claim 38, wherein an interior of said wave guide tube is filled with a second dielectric material which is different from said first dielectric material.
47. A microwave processing method according to claim 38, wherein said plasma process is film forming.
48. A microwave processing method according to claim 38, wherein said plasma process is etching.
49. A microwave processing method according to claim 38, wherein said plasma process is ashing.
50. A microwave plasma processing method wherein a substrate is placed in a microwave plasma processing apparatus comprising a plasma generation chamber separated from ambient air by a first dielectric material; a processing chamber connected
to the plasma generation chamber; means for supporting a substrate to be processed, to be placed in the processing chamber; microwave introduction means utilizing an endless annular wave guide tube provided around said plasma generation chamber and
provided with plural slots; means for introducing gas for said plasma generation chamber and said processing chamber; and evacuation means for said plasma generation chamber and said processing chamber, wherein the interior of said annular wave guide
tube is filled with a second dielectric material which is the same as or different from the first dielectric material, thereby effecting a plasma process.
51. A microwave processing method according to claim 50, wherein a ratio of the dielectric constants of said first and second dielectric materials is approximately equal to a reciprocal of a square of a ratio of circumferential lengths of said
first and second dielectric materials.
52. A microwave processing method according to claim 50, wherein said plasma process is effected under application of a magnetic field.
53. A microwave processing method according to claim 52, wherein the magnetic field in a vicinity of the slots has a magnetic flux density approximately equal to 3.57.times.10.sup.-11 (T/Hz) times of a frequency of the microwave.
54. A microwave processing method according to claim 50, comprising a step of placing said substrate on said substrate support means at a position distant from a generation area of said plasma.
55. A microwave processing method according to claim 50, wherein the plasma process is effected under irradiation of the substrate with optical energy.
56. A microwave processing method according to claim 50, wherein the plasma process is effected by supplying high frequency to said support means.
57. A microwave processing method according to claim 50, wherein said plasma process is film forming.
58. A microwave processing method according to claim 50, wherein said plasma process is etching.
59. A microwave processing method according to claim 50, wherein said plasma process is ashing. |
|
 |
|
 |
Claims |
|
|
|
Description |
|
|
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a microwave plasma processing apparatus and a method therefor, and more particularly to a microwave plasma processing apparatus and a method therefor capable of generating highly dense plasma uniformly over a
large area, allowing high-quality processing of a large-area substrate at a low temperature at a high speed.
2. Related Background Art
Among the plasma processing apparatuses utilizing microwaves as the exciting source for plasma generation, there are already known the CVD apparatus, the etching apparatus, the ashing apparatus, etc.
Film formation with microwave plasma CVD apparatus is conducted in the following manner. A gas is introduced in the plasma generation chamber and the film forming chamber (processing chamber) of the microwave plasma CVD apparatus, and a
microwave energy is supplied to generate plasma in the plasma generation chamber, thereby exciting and decomposing the gas and depositing a film on a substrate positioned in the film forming chamber (processing chamber).
Etching of a substrate with such microwave a plasma etching apparatus is conducted in the following manner: an etchant gas is introduced in the processing chamber of the apparatus, and a microwave energy is supplied to excite and decompose the
etchant gas and to generate plasma in the processing chamber, thereby etching the surface of a substrate provided in the processing chamber.
Such microwave plasma processing apparatus, utilizing microwave as the exciting source for the gas, can accelerate the electrons with an electric field of a high frequency, thereby efficiently ionizing and exciting the gas molecules.
Consequently such apparatus has high efficiencies in the ionization, excitation and decomposition of the gas, thus providing advantages of forming highly dense plasma relatively easily and of achieving high-quality processing at a low temperature with a
high speed. Also since microwaves can pass through a dielectric substance, the plasma processing apparatus can be constructed in an electrodeless discharge type, whereby the plasma processing can be achieved in a highly clean environment.
To attain a higher processing speed in such microwave plasma processing apparatus, an apparatus utilizing electron cyclotron resonance (ECR) has been commercialized. The ECR is a phenomenon in which, for a magnetic flux density of 87.5 mT, the
electron cyclotron frequency in which the electrons revolve around the magnetic flux, coincides with the common microwave frequency 2.45 GHz whereby the electrons are accelerated by resonant absorption of the microwave thereby generating highly dense
plasma. In such ECR plasma processing apparatus, there are known four representative configurations for the microwave introducing means and the magnetic field generating means.
More specifically, such configurations are (i) a configuration in which microwaves, transmitted through a wave guide tube, are introduced into a cylindrical plasma generation chamber through a transmissive window from a direction opposite to a
substrate to be processed (hereinafter, simply referred to as "processed substrate") while a diverging magnetic field concentric with the central axis of the plasma generation chamber is introduced through an electromagnetic coil provided around the
plasma generation chamber; (ii) a configuration in which microwaves, transmitted through a wave guide tube, are introduced into a bell-shaped plasma generation chamber through a transmissive window from a direction opposite to the processed substrate
while a magnetic field concentric with the central axis of the plasma generation chamber is introduced through an electromagnetic coil provided around the plasma generation chamber; (iii) a configuration in which microwaves are introduced into the plasma
generation chamber from the periphery thereof through a Rigitano coil, which is a kind of cylindrical slot antenna, while a magnetic field concentric with the central axis of the plasma generation chamber is introduced through an electromagnetic coil
provided around the plasma generation chamber; and (iv) a configuration in which microwaves, transmitted through a wave guide tube, are introduced into a cylindrical plasma generation chamber through a flat plate-shaped slot antenna from a direction
opposite to the processed substrate while a loop-shaped magnetic field parallel to the plane of the antenna is introduced by a permanent magnet provided behind the flat antenna.
In the field of such microwave plasma processing apparatus, there is recently proposed an apparatus utilizing an annular wave guide tube having plural slots on the internal lateral face thereof, for uniform and efficient introduction of the
microwave, as disclosed in the U.S. Pat. No. 5,487,875. An example of such microwave processing apparatus is shown in FIG. 1, and the plasma generating mechanism of such apparatus is shown in a schematic cross-sectional view in FIG. 2. In these
drawings there are shown a plasma generation chamber 501; a dielectric member 502 separating the plasma generation chamber 501 from the ambient air; a slotted endless annular wave guide tube 503 for introducing the microwave into the plasma generation
chamber 501; plasma generating gas introduction means 504; a processing chamber 511 connected with the plasma generation chamber 501; a substrate 512 to be processed; a support member 513 for the processed substrate 512; a heater 514 for heating the
processed substrate 512; process gas introduction means 515; a gas outlet 516; a block 521 for distributing the microwave to the right and to the left; a slot 522; microwave 523 introduced in the annular wave guide tube 503; microwave 524 propagating in
the annular wave guide tube 503; leaking wave 525 of the microwave introduced through the slot 522 and the dielectric member 502 into the plasma generation chamber 501; surface wave 526 of the microwave transmitted by the slot 522 and propagating in the
dielectric member 502; plasma 527 generated by the leaking wave; and plasma 528 generated by the surface wave.
The generation of plasma and the processing therewith are carried out in the following manner. The interiors of the plasma generation chamber 501 and the processing chamber 511 are evacuated by a vacuum system (not shown). Then plasma
generating gas is introduced, by gas introduction means 504, into the plasma generation chamber 501 at a predetermined flow rate. Then a conductance value provided in the vacuum system (not shown) is so adjusted as to maintain the interior of the plasma
generation chamber 501 at a predetermined pressure. A desired electric power is supplied from a microwave source (not shown), through the annular wave guide tube 503, into the plasma generation chamber 501. The microwave 523 introduced into the annular
wave guide tube 503 is distributed to the left and to the right by the distributing block 521, and propagates with an in-tube wavelength longer than the wavelength in the free space. The leaking wave 525, introduced into the plasma generation chamber
501 through the slots 522 which are provided at an interval of 1/2 or 1/4 of the guide wavelength of such propagating microwave 524 and also through the dielectric member 502, generates plasma 527 in the vicinity of the slot 522. Also the microwave made
incident with an angle equal to or larger than the Brewster's angle to a normal line to the surface of the dielectric member 502 is totally reflected by the first surface of the dielectric member 502 and propagates inside the dielectric member 502 as a
surface wave 526. Also the leaking electric field of the surface wave 526 generates plasma 528. Processing gas, introduced into the processing chamber 511 through the processing gas introduction pipe 515, is excited by the generated dense plasma, and
thus excited gas processes the surface of the processed substrate 512 placed on the support member 513. The processing gas may also be introduced from the plasma generating gas introduction means 504.
FIGS. 3 and 4 schematically illustrate the relationship between the annular wave guide tube 503 and the plasma generation chamber 501. In FIGS. 3 and 4, components the same as those in FIGS. 1 and 2 are represented by the same numbers. FIGS. 3
and 4 are respectively a schematic perspective view and a schematic cross-sectional view, showing the principal parts only.
Such microwave plasma processing apparatus is capable, with a microwave power of 1 kW or higher, of generating low-temperature high-density plasma of an electronic temperature of 3 eV or less and an electron density of 10.sup.12 /cm.sup.3 or
higher uniformly in a space of a large diameter of 300 mm of higher, thereby causing sufficient reaction of the gas and supplying the gas in the activated state to the substrate, whereby high-quality processing can be achieved with a high speed, even at
a low temperature.
However, in consideration of the low-temperature processing with the microwave plasma processing apparatus capable of generating low-temperature high-density plasma as shown in FIGS. 1 and 2, there is desired an apparatus and a method therefor,
capable of generating plasma of a higher density in a larger diameter space with a lower power, in order to achieve processing such as film forming, etching or ashing with higher quality at a lower temperature at a higher speed.
SUMMARY OF THE INVENTION
In consideration of the foregoing, an object of the present invention is to provide a microwave plasma processing apparatus and a method therefor, capable of generating uniform high-density plasma of a large area with a low power, thereby
enabling high-quality processing at a high speed, even at a low temperature.
Another object of the present invention is to provide a microwave plasma processing apparatus comprising a plasma generation chamber whose periphery is separated from the ambient air by a dielectric member, microwave introduction means utilizing
an endless annular wave guide tube provided around the plasma generation chamber and provided with plural slots, a processing chamber connected to the plasma generation chamber, support means for a substrate to be processed, provided in the processing
chamber, gas introduction means for the plasma generation chamber and the processing chamber, and evacuation means for the plasma generation chamber and the processing chamber, wherein the circumferential length L.sub.g of the endless annular wave guide
tube, the wavelength .lambda..sub.g of the microwave in the endless annular wave guide tube, the circumferential length L.sub.s of the dielectric member and the wavelength .lambda..sub.s of the surface wave propagating in the dielectric member
substantially satisfy a relationship:
wherein n is 0 or a natural number.
Still another object of the present invention is to provide a microwave plasma processing apparatus comprising a plasma generation chamber of which periphery is separated from the ambient air by a dielectric member, microwave introduction means
utilizing a cylindrical endless annular wave guide tube provided around the plasma generation chamber and provided with plural slots, a processing chamber connected to the plasma generation chamber, support means for a substrate to be processed, provided
in the processing chamber, gas introduction means for the plasma generation chamber and the processing chamber, and evacuation means for the plasma generation chamber and the processing chamber, wherein the central radius R.sub.g of the endless annular
wave guide tube, the wavelength .lambda..sub.g of the microwave in the endless annular wave guide tube, the central radius R.sub.s of the dielectric member and the wavelength .lambda..sub.s of the surface wave propagating in the dielectric member
substantially satisfy a relationship:
wherein n is 0 or a natural number.
Still another object of the present invention is to provide a microwave plasma processing apparatus comprising a plasma generation chamber separated from the ambient air by a first dielectric material, a processing chamber connected to the plasma
generation chamber, means for supporting a substrate to be processed, to be placed in the processing chamber, microwave introduction means utilizing an endless annular wave guide tube provided around the plasma generation chamber and provided with plural
slots, means for introducing gas for the plasma generation chamber and the processing chamber, and evacuation means for the plasma generation chamber and the processing chamber, wherein the interior of the annular wave guide tube is filled with a second
dielectric material which is the same as or different from the first dielectric material.
Still another object of the present invention is to provide a microwave plasma processing method utilizing a microwave plasma processing apparatus comprising a plasma generation chamber of which periphery is separated from the ambient air by a
dielectric member, microwave introduction means utilizing an endless annular wave guide tube provided around the plasma generation chamber and provided with plural slots, a processing chamber connected to the plasma generation chamber, support means for
a substrate to be processed, provided in the processing chamber, gas introduction means for the plasma generation chamber and the processing chamber, and evacuation means for the plasma generation chamber and the processing chamber, and selecting the
circumferential length L.sub.g of the endless annular wave guide tube, the wavelength .lambda..sub.g of the microwave in the endless annular wave guide tube, the circumferential length L.sub.s of the dielectric member and the wavelength .lambda..sub.s of
the surface wave propagating in the dielectric member so as to substantially satisfy a relationship:
wherein n is 0 or a natural number, thereby effecting a plasma process on the substrate.
Still another object of the present invention is to provide a microwave plasma processing method utilizing a microwave plasma processing apparatus comprising a plasma generation chamber of whose periphery is separated from the ambient air by a
dielectric member, microwave introduction means utilizing a cylindrical endless annular wave guide tube provided around the plasma generation chamber and provided with plural slots, a processing chamber connected to the plasma generation chamber, support
means for a substrate to be processed, provided in the processing chamber, gas introduction means for the plasma generation chamber and the processing chamber, and evacuation means for the plasma generation chamber and the processing chamber, and
selecting the central radius R.sub.g of the endless annular wave guide tube, the wavelength .lambda..sub.g of the microwave in the endless annular wave guide tube, the central radius R.sub.s of the dielectric member and the wavelength .lambda..sub.s of
the surface wave propagating in the dielectric member so as to substantially satisfy a relationship:
wherein n is 0 or a natural number, thereby effecting a plasma process.
Still another object of the present invention is to provide a microwave plasma processing method by placing a substrate in a microwave plasma processing apparatus comprising a plasma generation chamber separated from the ambient air by a first
dielectric material, a processing chamber connected to the plasma generation chamber, means for supporting a substrate to be processed, to be placed in the processing chamber, microwave introduction means utilizing an endless annular wave guide tube
provided around the plasma generation chamber and provided with plural slots, means for introducing gas for the plasma generation chamber and the processing chamber, and evacuation means for the plasma generation chamber and the processing chamber,
wherein the interior of the annular wave guide tube is filled with a second dielectric material which is the same as or different from the first dielectric material, thereby effecting a plasma processing.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic cross-sectional view of a plasma processing apparatus;
FIG. 2 is a schematic cross-sectional view for explaining an example of the plasma generating mechanism;
FIG. 3 is a schematic perspective view of an example of the wave guide tube;
FIG. 4 is a schematic plan view thereof;
FIG. 5 is a schematic cross-sectional view of a plasma processing apparatus;
FIG. 6 is a schematic cross-sectional view for explaining an example of the plasma generating mechanism;
FIG. 7 is a schematic cross-sectional view for explaining an example of the plasma processing apparatus;
FIG. 8 is a schematic cross-sectional view for explaining an example of the plasma generating mechanism; and
FIGS. 9, 10, 11, 12 and 13 are schematic cross-sectional views for explaining examples of the plasma processing apparatus.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Now the present invention will be clarified in detail by preferred embodiments, with reference to the attached drawings.
An example of the microwave plasma processing apparatus of the present invention and the plasma generating mechanism thereof are respectively shown in FIGS. 5 and 6, wherein shown are a plasma generation chamber 101; a dielectric member 102 for
separating the plasma generating chamber 101 from the ambient air; a slotted endless annular wave guide tube 103 for introducing the microwave into the plasma generation chamber 101; plasma generating gas introduction means 104; a processing chamber 111
connected to the plasma generation chamber; a substrate 112 to be processed; a support member 113 for the processed substrate 112; a heater 114 for heating the processed substrate 112; processing gas introduction means 115; an evacuation outlet 116; a
block 121 for distributing the microwave to the left and to the right; a slot 122; microwave 123 introduced into the annular wave guide tube 103; microwave 124 propagating in the annular wave guide tube 103; leaking wave 125 of the microwave introduced
into the plasma generation chamber 101 through the slot 122 and the dielectric member 102; surface wave 126 of the microwave transmitted through the slot 122 and propagating in the dielectric member 102; plasma 127 generated by the leaking wave; and
plasma 128 generated by the surface wave.
The generation of plasma and the processing therewith are carried out in the following manner. The interior of the plasma generation chamber 101 and the processing chamber 111 is evacuated by a vacuum system (not shown). Then plasma generating
gas is introduced, by gas introduction means 104, into the plasma generation chamber 101 at a predetermined flow rate. Then a conductance valve provided in the vacuum system (not shown) is so adjusted as to maintain the interior of the plasma generation
chamber 101 at a predetermined pressure. A desired electric power is supplied from a microwave source (not shown), through the annular wave guide tube 103, into the plasma generation chamber 101, thereby generating plasma therein. The microwave 123
introduced into the annular wave guide tube 103 is distributed to the left and to the right by the distributing block 121, and propagates in the annular wave guide tube 103. The leaking wave 125, introduced into the plasma generation chamber 101 through
the slots 122 which are provided at an interval of 1/2 or 1/4 of the guide wavelength of such propagating microwave 124 and also through the dielectric member 102, generates plasma 127 in the vicinity of the slot 122. Also the microwave entering with an
angle equal to or larger than the Brewster's angle to a normal line to the surface of the dielectric member 102 is totally reflected by the surface of the dielectric member 102 and propagates inside the dielectric member 102 as a surface wave 126. Also
the leaking electric field of the surface wave 126 generates plasma 128.
In the apparatus shown in FIGS. 1 and 2, as the surface wave 526 is not excited in the course of propagation, the generated plasma 528 becomes less dense than the plasma 527 generated by the leaking wave 525. However, in case of the apparatus of
the present invention shown in FIGS. 5 and 6, the in-tube wavelength and the circumferential length of the annular wave guide tube 103 are so optimized that the slots 122 are positioned at an interval of 1/2 of the surface wave 126, whereby the surface
wave 126 is amplified in the course of propagation by interference with the leaking wave 125 from other slots to generate denser and more uniform plasma 128 in comparison with the aforementioned case. Processing gas, introduced into the processing
chamber 111 through the processing gas introduction pipe 115, is excited by the generated high-density plasma, and thus excited gas processes the surface of the substrate 112 placed on the support member 113. The processing gas may also be introduced
from the plasma generating gas introduction means 104.
In the above-explained microwave plasma processing apparatus of the present invention, the circumferential length L.sub.g of the annular wave guide tube 103, the wavelength .lambda..sub.g of the microwave 124 therein, the circumferential length
L.sub.s of the dielectric member 102 and the wavelength .lambda..sub.s of the surface wave propagating therein are so selected as to substantially satisfy a relationship:
wherein n is 0 or a natural number, whereby the surface wave of the microwave propagating in the dielectric member is periodically excited to realize stronger and more efficient propagation, thus generating uniform high-density plasma over a
large area with a low electric power. The above-mentioned relationship is preferably satisfied within a range of .+-.10%.
In case the annular wave guide tube 103 has a cylindrical annular shape, the central radius R.sub.g of the annular wave guide tube, the wavelength .lambda..sub.g of the microwave in the endless annular wave guide tube, the central radius R.sub.s
of the dielectric material and the wavelength .lambda..sub.s of the surface wave propagating in the dielectric material are so selected as to substantially satisfy a relationship:
wherein n is 0 or a natural number, whereby the surface wave of the microwave propagating in the dielectric material is periodically excited to realize stronger and more efficient propagation, thus generating uniform high-density plasma over a
large area with a low electric power. The above-mentioned relationship is preferably satisfied within a range of .+-.10%.
Another preferred embodiment of the microwave plasma processing apparatus of the present invention and the plasma generating mechanism thereof are respectively illustrated in FIGS. 7 and 8, in which components the same as those shown in FIGS. 5
and 6 are represented by the same numbers and will not be explained further.
The apparatus shown in FIGS. 7 and 8 is different from the foregoing one in that the annular wave guide tube 103 is filled with a second dielectric material, which is in addition to the dielectric material (first dielectric material) separating
the plasma generation chamber 101 from the ambient air.
In the apparatus shown in FIG. 1, as the surface wave 526 is not excited in the course of propagation, the generated plasma 528 becomes less dense than the plasma 527 generated by the leaking wave 525. However, in the apparatus shown in FIG. 7,
the dielectric constant of the second dielectric material 704 is so optimized that the slots 122 are positioned at an interval of 1/2 of the surface wave 126, whereby the surface wave 126 is amplified in the course of propagation by interference with the
leaking wave 125 from other slots to generate denser and more uniform plasma 128 in comparison with the configuration shown in FIG. 1. Processing gas, introduced into the processing chamber 111 through the processing gas introduction pipe 115, is
excited by the generated high-density plasma, and thus excited gas processes the surface of the processed substrate 112 placed on the support member 113. The processing gas may also be introduced from the plasma generating gas introduction input 104.
A desired electric power is supplied from a microwave source (not shown), through the annular wave guide tube 103 filled with the second dielectric material 704 and through the first dielectric material 102, into the plasma generation chamber
101, thereby generating plasma therein. The microwave 123 introduced into the annular wave guide tube 103 is distributed to the left and to the right by the distributing block 121, and propagates in the second dielectric material 704 with a shorter
wavelength than in the free space. The leaking wave 125, introduced into the plasma generation chamber 101 through the slots 122 which are provided at an interval of 1/2 or 1/4 of the guide wavelength and also through the first dielectric material 102,
generates plasma 127 in the vicinity of the slot 122. Also the microwave entering with an angle equal to or larger than the Brewster's angle to a normal line to the surface of the first dielectric material 102 is totally reflected by the surface thereof
and propagates inside the first dielectric material 102 as a surface wave 126. Also the leaking electric field of the surface wave 126 generates plasma 128.
As explained in the foregoing, the interior of the annular wave guide tube is filled with a second dielectric material which is the same as or different from the first dielectric material for separating the plasma generation chamber from the
ambient air, and the ratio of the dielectric constants of the first and second dielectric materials is approximately equal to the reciprocal of the square of the ratio of the circumferential lengths of the first and second dielectric materials, whereby
the surface wave of the microwave propagating in the first dielectric material is periodically excited to realize stronger and more efficient propagation, thus generating uniform high-density plasma over a large area with a low electric power.
The frequency of the microwave, employed in the microwave plasma processing apparatus and the method therefor of the present invention, can be suitably selected within a range from 0.8 to 20 GHz.
Also the shape of the wave guide tube employed in the microwave plasma processing apparatus of the present invention may be cylindrical, or another shape such as a disk-shape or a polygonal shape according to the shape of the plasma generation
chamber.
The dielectric material, employed in the microwave plasma processing apparatus and the method therefor of the present invention, can be, for example, a film or a sheet of quartz or SiO.sub.2 -based glass, an inorganic material such as Si.sub.3
N.sub.4, NaCl, LiF, CaF.sub.2, BaF.sub.2, Al.sub.2 O.sub.3, AlN or MgO, or an organic material such as polyethylene, polyester, polycarbonate, cellulose acetate, polypropylene, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyamide or
polyimide.
In the microwave plasma processing apparatus and the method therefor of the present invention, magnetic field generation means may be employed to achieve processing at a lower pressure. Such magnetic field can be, for example, a miller magnetic
field, but there is most preferably employed a cusp magnetic field, having a nodal plane in a plane containing the centers of the plural slots of the slotted annular wave guide tube, showing magnetic fluxes substantially perpendicular to the substrate
support member and having a magnetic flux density in the vicinity of the slots larger than that in the vicinity of the substrate. The magnetic field generation means can be composed of a coil or a permanent magnet. In case of a coil, there may also be
employed cooling means such as a water-cooling or air-cooling mechanism, for avoiding overheating. By the use of such magnetic field generation means, the magnetic field in the vicinity of the slots is preferably controlled at a magnetic flux density of
about 3.57.times.10.sup.-11 (T/Hz) times of the microwave frequency. The above-mentioned control is desirably achieved within a range of .+-.10% of the above-mentioned figure.
For achieving higher quality in the processing, the surface of the processed substrate may be irradiated with optical energy such as ultraviolet energy. For this purpose there can be employed any light source emitting the light absorbed by the
processed substrate or the gas deposited thereon, such as an excimer laser, an excimer lamp, a rare gas resonance line lamp or a low-pressure mercury lamp.
The pressure in the plasma generation chamber and in the processing chamber in the microwave plasma processing method of the present invention is preferably selected within a range, generally from 0.1 Torr to 20 Torr, particularly from 1 mTorr to
100 mTorr in case of film formation, and from 100 mTorr to 10 Torr in case of ashing.
The microwave plasma processing method of the present invention allows efficient formation of various deposited films by suitable selection of the used gas, for example an insulation film such as of Si.sub.3 N.sub.4, SiO.sub.2, Ta.sub.2 O.sub.5,
TiO.sub.2, TiN, Al.sub.2 O.sub.3, AlN or MgF.sub.2, a semiconductor film such as of a-Si (amorphous Si), poly-Si, SiC or GaAs, or a metal film such as of Al, W, Mo, Ti or Ta.
The substrate to be processed by the plasma processing method of the present invention can be semiconductive, electroconductive or electroinsulating. The method is also applicable to plastic materials of low thermal resistance.
Examples of the electroconductive substrate include metals such as Fe, Ni, Cr, Al, Mo, Au, Nb, Ta, V, Ti, Pt or Pb, and alloys thereof such as brass or stainless steel.
Examples of the insulating substrate include a film or a sheet of quartz or SiO.sub.2 -based glass, an inorganic material such as Si.sub.3 N.sub | | |
