JP3355926B2 - Plasma processing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma processing apparatus, and more particularly to a plasma processing apparatus suitable for generating ECR plasma and processing a sample such as a semiconductor substrate (hereinafter abbreviated as "wafer") using the plasma.

[0002]

2. Description of the Related Art In general, in an apparatus for generating a plasma by introducing a microwave into a processing chamber, it is required that a plasma density distribution on a surface to be processed of a sample is uniform.
This is important for ensuring uniformity of processing such as etching. For this purpose, a conventional plasma processing apparatus includes:
For example, reference A. "The Japan Society of Applied Physics Autumn 1994, 19p-
ZV-4 "or literature B. "The Japan Society of Applied Physics 1994
As shown in “Autumn, 19p-ZV-6”, microwaves are radiated from the upper surface of the processing chamber in a ring shape, thereby generating plasma in a ring shape. As a result, a uniform plasma distribution on the wafer surface is obtained. There is a way to get it. this is,
This is because the plasma has a property of diffusing as it is transported from the generation place toward the wafer. Finally, uniformity of the etching rate itself is required,
In this case, since the plasma density distribution is better in the concave shape than in the uniform shape or better in the convex shape, it is desirable to have an adjusting means.

As a means for producing a plasma in a ring shape, for example, there is a means described in Japanese Patent Application Laid-Open No. Hei 6-112161.

[0004]

In this section, problems relating to microwave plasma uniformity will be described first. The above-mentioned prior art documents A and B have ring-shaped plasma radiating means and have a configuration suitable for producing uniform plasma. However, the reached plasma density is 3 to 10 × 10 ¹⁰ cm ^−3. And low level, and industrially necessary level 3 ~
Not more than 10 ¹¹ cm ^-3 . This is because both use a local magnetic field generated by a permanent magnet at the exit of the microwave, so the microwave absorption efficiency is not optimal, and the microwave transmission line design is optimized so that high-power microwaves can be transmitted. The cause is probably not being done. Further, in the case of the prior art document A, a complicated three-dimensionally-depressed structure is introduced into the plasma processing chamber, which causes the generation of foreign matter. Further, Japanese Patent Application Laid-Open No. 6-11216 discloses a conventional technique.
No. 1 discloses a configuration in which a coaxial line is opened in a tapered shape, and the microwave radiating portion is enlarged.

An object of the present invention is to provide a plasma processing apparatus capable of generating high-density plasma with a compact apparatus and performing uniform processing of a sample.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a plasma processing apparatus which generates plasma using an ECR in a processing chamber and processes a sample placed on a sample table in the processing chamber with the plasma. The opposite surface is a vacuum introduction window made of quartz, and the parallel plate disk waveguide is connected to the non-processing chamber side of the vacuum introduction window via a parallel plate disk waveguide connected to a small-diameter coaxial waveguide. This is achieved by providing an enlarged coaxial waveguide connected to the processing chamber, and providing a magnetic field coil for forming a magnetic field in the processing chamber on the outer peripheral portion of the processing chamber and the enlarged coaxial waveguide and on the upper part of the enlarged coaxial waveguide. .

More preferably, the parallel-plate disk-shaped waveguide has a small-diameter and a large-diameter ring-shaped opening, and the enlarged waveguide is connected to the opening.

Another object of the present invention is to provide a plasma processing apparatus for generating plasma using an ECR in a processing chamber and processing the sample placed on a sample table in the processing chamber to which a high-frequency bias is applied by the plasma. A surface facing the table is a vacuum introduction window made of quartz, a counter electrode for the sample is provided in the center of the vacuum introduction window, and a parallel plate disk connected to a small-diameter coaxial waveguide on the side opposite to the processing chamber of the vacuum introduction window. Providing an enlarged coaxial waveguide connected to the parallel-plate disk waveguide via the parallel waveguide, and forming the counter electrode on the processing chamber surface side of the flat disk of the parallel-plate disk waveguide. This is achieved by providing a magnetic field coil for forming a magnetic field in the processing chamber on the outer peripheral portion of the processing chamber and the enlarged coaxial waveguide and on the upper part of the enlarged coaxial waveguide.

[0009] More preferably, the opposing electrode is formed of a member of Si or SiC.

[0010] Preferably, a processing gas blowing mechanism is provided in the counter electrode.

[0011] The above object is to hold a wafer.
Processing chamber with a sample stage and vacuum exhausting the processing chamber
Vacuum exhaust device and gas supply device that supplies gas to the processing chamber
And introduce a microwave into the processing chamber to generate plasma
Microwave introduction device and a vertical static magnetic field in the processing chamber
Plasma processing apparatus equipped with a magnetic field coil
The microwave introduction device to guide the microwave
Coaxial waveguide converter connected to the waveguide, coaxial waveguide converter
The small diameter coaxial waveguide connected to the vessel and the small diameter coaxial waveguide
A continuous parallel plate disk waveguide and a parallel plate disk
The expanded coaxial waveguide connected to the
Located at the end of the waveguide and forms a microwave inlet to the processing chamber.
This is achieved by comprising a microwave introduction vacuum window to be formed.

Desirably, the disc at the junction between the small-diameter coaxial waveguide impedance Z0 (= 60 ln (R3 / R4)), R3: radius of the outer conductor of the coaxial waveguide, and R4: radius of the inner conductor of the coaxial waveguide) The impedance Z1 on the waveguide side (= 60b / R3, b: distance between parallel disks) matches and the expanded coaxial waveguide impedance Z2 (= 6
0ln (R2 / R1), R2: radius of outer conductor of coaxial tube, R
1: conductor radius in a coaxial waveguide) and impedance Z1 (= 60b /
R1) is characterized in that R1, R2, R3, R4, and b are selected so as to coincide with R1).

Preferably, the outer diameter R2 of the enlarged coaxial waveguide is
However, it is characterized in that it is smaller than the inner diameter R5 of the processing chamber connected to the microwave vacuum window (R2 <R5).

Preferably, the microwave used has a frequency in the range of 500 MHz to 5 GHz.

Preferably, the microwave used is:
It is characterized in that a plurality of microwave sources having different frequencies are used simultaneously.

Preferably, the microwave used is:
It is characterized by using a microwave source whose frequency is variable.

Preferably, a portion of the vacuum window other than the portion corresponding to the microwave radiating portion (R1 <R <R2), which is in contact with the plasma, is connected to the ground conductor plate or Si or
It is characterized by installing a semiconductor plate such as SiC.

Preferably, a magnetic field coil or a permanent magnet is provided using a portion other than the portion corresponding to the microwave radiating portion (R1 <R <R2).

Desirably, the parallel-plate disk-shaped waveguide has two ring-shaped openings of a small diameter and a large diameter, and has a configuration in which an enlarged coaxial waveguide is connected to each closed part. Features.

Preferably, there is provided a means for varying the power distribution of the microwave to the two enlarged coaxial waveguides.

A microwave is radiated in a coaxial ring shape, and the intensity of a static magnetic field for generating electron cyclotron resonance (ECR) (B = 8 when microwave 2.45 GHz is used)
By adjusting 75 gauss), the plasma generation region (that is, the electron cyclotron resonance position) is immediately below the ring radiation source, and plasma is generated in a ring shape. Since the plasma is diffused, it has a uniform plasma distribution when transported onto the wafer.

The uniformity of the plasma on the wafer surface can be changed by changing the diameter of the coaxial ring or double the ring radiation source and changing the microwave radiation intensity from each. That is, in the double ring, the distribution is closer to the center when the inner ring is stronger, and the outer ring is closer to the outer ring when the outer ring is stronger.

If the ECR resonance position is lowered so that the microwave is not immediately absorbed by the plasma after leaving the ring radiator, the microwave intensity distribution is diffused and then absorbed by the plasma. The plasma uniformity becomes variable. That is, the uniformity can be changed by changing the static magnetic field strength.

In the present invention, since the ring-shaped microwave radiation source is installed on the atmosphere side through the vacuum introduction window, there is no concern about the generation of foreign matter due to the radiation source itself.

Since a ring radiator is used, a wafer facing electrode can be provided at the center of the radiator. That is, the conventional ECR type microwave plasma processing apparatus has a structure in which it is difficult to set an electrode at a position facing the wafer, and it is difficult to uniformly apply a high frequency bias.
According to the present invention, this can be solved. Further, a gas pipe for blowing out the processing gas and a member for absorbing excessive radicals in the processing plasma (for example, a Si plate scavenger for fluorine radicals) can be provided in the central portion.

If the microwave ring radiation source is installed at a position distant from the inner wall of the plasma processing chamber, the plasma generation position does not directly touch the wall. Thus, damage to the sidewall material can be avoided.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments. FIG. 1 is a front view showing a part of a microwave plasma processing apparatus according to an embodiment of the present invention in a longitudinal section. In FIG. 1, a microwave is transmitted from a waveguide A1, and is shifted to a coaxial TEM mode by a coaxial waveguide converter A2.
It travels through the small-diameter coaxial tube A3. The microwave exiting the coaxial waveguide A3 moves to the parallel disk waveguide A4, spreads, and then moves to the enlarged coaxial waveguide A5, which is a large-diameter coaxial waveguide part, and the processing chamber A6.
Get in. An electromagnetic coil A for generating a static magnetic field around the processing chamber
7 to form an ECR plane A8. The plasma generation part A9 becomes ring-shaped correspondingly and reaches the wafer mounting electrode A10 to be uniform. In FIG. 1, A11 is a vacuum introduction window formed of quartz or the like. A12 is a side wall of the processing chamber A6. The results of measuring the state of plasma generation under this system are shown in FIGS. 2 (a) and 2 (b). FIG.
((A) and (b)) show a two-dimensional distribution measurement of the saturated ion current density (corresponding to the plasma density immediately above the wafer) at a position on the electrode (FIG. 2 (a) shows an ECR plane: 79 mm above the wafer,
FIG. 2 (b) shows an ECR plane: 99 mm above the wafer, which indicates that a highly uniform or concave distribution can be obtained depending on the magnetic field conditions. Also, the obtained current density is 10 in C ₄ F ₈ plasma.
As high as mA / cm ² or more, the required level is evenly reached. The input microwave power was 1-2 kW, but there was no overheating of the waveguide.

The dimensions of such a microwave radiator will be described with reference to FIG. Small diameter coaxial tube characteristic impedance Z0 = 50Ω, parallel disk impedance Z
1 (R), it is necessary to match the enlarged coaxial impedance Z2 so that microwave reflection does not occur at each joint. There is no known document for the impedance Z1, and the impedance Z1 is newly derived. If Write a balanced result, _{Z1 (R) = (bZ a} / 2πjR) * Y 0 2 (KR) / Y 1 2 (KR) ... ( Equation 1). Here, b: distance between disks, R: radial position, Z _a : characteristic impedance of free space (Z _a = 377)
Ω), j: imaginary unit, Y ₁₂ : 1st-order second-order Hankel function, K = 2π / λ: wave number, incident wavelength. If KR> 1, Z1 (R) is asymptotically approximated as _{Z1 (R) = Z a b} / 2πR = 60b / R ... ( Equation 2).

Since the impedance Z2 of the enlarged coaxial portion is expressed as follows: Z2 = 60lnR2 / R1 (Equation 3), Z0: Z1 (R3), Z2 = Z1 (R
The specifications R1, R2, R3, R4, and b may be determined so as to satisfy 1).

FIG. 4 shows a second embodiment of the present invention. It is desired that the uniformity of the plasma can be adjusted from convex to concave rather than completely uniform. This is because the uniformity of, for example, the etching of the sample to be processed is governed by the uniformity of the processing gas and the high-frequency bias in addition to the uniformity of the plasma, and the uniformity of the plasma can be adjusted. Covering means ensuring final etch uniformity. FIG.
The ring radiating portion is provided in a double manner so that microwaves are radiated from the inner ring and the outer ring. By changing the disc spacing b and the inner ring opening diameter ΔR, the power distribution changes, and the distribution of microwaves in the processing chamber changes. To change ΔR, the disk component A41 is replaced. Alternatively, by changing b, as shown in FIG.
It may be changed depending on. Alternatively, as shown in FIG. 6, the ceiling member A43 of the parallel disk is made variable by a plunger mechanism. In the method shown in FIG. 4, each time the uniformity is changed, parts are replaced. However, the waveguide is simpler and more reliable than those shown in FIGS. On the contrary, in FIGS. 5 and 6, the efficiency of the uniformity adjustment is improved, but since the movable portion is brought into the waveguide, the reliability at the time of passing large power becomes a problem.

FIG. 7 shows a third embodiment, in which a conductor structure (aluminum or the like) is introduced on the side facing the processing chamber A below the parallel disk, and the counter electrode A1 for the wafer is introduced.
Form 3 Thereby, the high frequency bias is made uniform. Further, if the member at this position is made of Si or SiC, excess fluorine in the plasma can be absorbed, and the selectivity to base (Si) in the SiO ₂ etching process can be improved. In the present invention, the processing gas blowing mechanism A14 is
This space is used to provide the processing gas flow A
By flowing 15 from the central portion to the outer peripheral portion, uniformity of the processing gas can be expected. In this space, a magnet (coil or permanent magnet) or a magnetic body A16 can be provided, and by arranging the magnetic force lines A17 as shown in the figure, the uniformity of the plasma can be increased.

[0032]

As described above, according to the present invention, the EC in the processing chamber is provided.
In a plasma processing apparatus for generating plasma using R and processing a sample placed on a sample stage in a processing chamber to which a high-frequency bias is applied by plasma, a vacuum introduction window made of quartz on a surface facing the sample stage in the processing chamber. And, on the side opposite to the processing chamber of the vacuum introduction window, via the parallel-plate disk waveguide connected to the small-diameter coaxial waveguide, the enlarged coaxial waveguide connected to the parallel-plate disk waveguide. By providing a magnetic field coil that forms a magnetic field in the processing chamber on the outer periphery of the processing chamber and the expanded coaxial waveguide and on the upper part of the expanded coaxial waveguide,
It can be a compact device and has an ECR
And high-density plasma can be generated in a ring shape, and uniform processing of the sample can be performed.

Further, by forming the counter electrode on the processing chamber surface side of the flat disk of the parallel flat disk waveguide at the center of the vacuum introduction window, the high frequency bias can be made uniform and the sample can be made uniform. Processing can be further improved.

Further, by forming the opposing electrode with a member of Si or SiC, it is possible to improve the selectivity with respect to the underlying Si at the time of etching SiO _2, and to provide a processing gas blowing mechanism for the opposing electrode. In addition, the uniformity of the processing gas is achieved, and the uniform processing of the sample can be further improved.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a result of a plasma test according to the present invention.

FIG. 3 is an explanatory view showing a dimensional relationship of the present invention.

FIG. 4 is an explanatory view showing a second embodiment (1) of the present invention.

FIG. 5 is an explanatory view showing a second embodiment (2) of the present invention.

FIG. 6 is an explanatory view showing a second embodiment (3) of the present invention.

FIG. 7 is an explanatory view showing a third embodiment of the present invention.

[Explanation of symbols]

A1: waveguide, A2: coaxial waveguide converter, A3: small-diameter coaxial waveguide, A4: parallel disk waveguide, A5: enlarged coaxial waveguide,
A6: processing chamber, A7: electromagnetic coil, A8: ECR surface, A9
... Plasma generator, A10 ... Wafer installation electrode, A11 ...
Vacuum introduction window, A12: Side wall, A41: Disk component, A
42: screw mechanism, A43: ceiling member, A13: counter electrode, A14: processing gas blowing mechanism, A15: processing gas flow, A16: magnet, A17: magnetic force line.

Continued on the front page (51) Int.Cl. ⁷ Identification code FI H01L 21/3065 H01L 21/302 B (72) Inventor Ryoji Nishio 502, Kandate-cho, Tsuchiura-shi, Ibaraki Pref. Hitachi, Ltd. Mechanical Laboratory (72) Invention Person: Manabu Edamura 502, Kandamachi, Tsuchiura-shi, Ibaraki Pref. Machinery Research Laboratory, Hitachi, Ltd. (56) References JP-A-5-47712 (JP, A) JP-A-6-73568 (JP, A) 101071 (JP, A) JP-A-6-333844 (JP, A) JP-A-6-112161 (JP, A) JP-A-7-85995 (JP, A) JP-A-7-99098 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H05H 1/46

Claims (17)

(57) [Claims] 1. A plasma processing apparatus for generating a plasma using an ECR in a processing chamber and processing a sample placed on a sample stage in the processing chamber with the plasma, wherein a surface of the processing chamber facing the sample stage is provided. A vacuum introduction window made of quartz is connected to the parallel plate disk waveguide through a parallel plate disk waveguide connected to a small-diameter coaxial waveguide on the side opposite to the processing chamber of the vacuum introduction window. And a magnetic field coil for forming a magnetic field in the processing chamber is provided on the outer periphery of the processing chamber and the expanded coaxial waveguide and on the upper part of the expanded coaxial waveguide. Plasma processing equipment. 2. A plasma processing apparatus according to claim 1, wherein said parallel-plate disk-shaped waveguide has a small-diameter and a large-diameter ring-shaped opening, and said enlarged waveguide is connected to said opening. A plasma processing apparatus characterized in that: 3. A plasma processing apparatus for generating a plasma using an ECR in a processing chamber and processing a sample placed on a sample stage to which a high-frequency bias is applied in the processing chamber by the plasma. The surface facing the table was a vacuum introduction window made of quartz, a counter electrode for the sample was provided at the center of the vacuum introduction window, and a small-diameter coaxial waveguide was connected to the opposite side of the vacuum introduction window from the processing chamber. An enlarged coaxial waveguide connected to the parallel-plate disk waveguide is provided via the parallel-plate disk waveguide, and the enlarged coaxial waveguide is opposed to the processing chamber surface side of the flat disk of the parallel-plate disk waveguide. A plasma processing apparatus comprising: an electrode; and a magnetic field coil for forming a magnetic field in the processing chamber, provided on an outer peripheral portion of the processing chamber and the expanded coaxial waveguide and on an upper part of the expanded coaxial waveguide. Place. 4. A plasma processing apparatus according to claim 3, wherein said counter electrode is formed of a Si or SiC member. 5. The plasma processing apparatus according to claim 3, wherein a processing gas blowing mechanism is provided on the counter electrode. 6. A sample stage for holding a wafer is provided.
Processing chamber and vacuum evacuation apparatus for evacuating the processing chamber
A gas supply device for supplying gas to the processing chamber;
A microwave generator is introduced into the processing chamber to generate plasma.
Microwave introduction device and vertical static magnetic field generated in the processing chamber
Plasma processing apparatus equipped with a magnetic field coil
In addition, the microwave introduction device has a waveguide through which microwaves are propagated.
A coaxial waveguide converter connected to the waveguide, and the coaxial waveguide
A small-diameter coaxial waveguide connected to a transducer, and the small-diameter coaxial waveguide
A parallel-plate disk-shaped waveguide connected to a waveguide;
Expanded coaxial waveguide connected to a row-plate disc-shaped waveguide
And at the end of the enlarged coaxial waveguide to the processing chamber
A microwave introduction vacuum window forming a microwave introduction part;
A plasma processing apparatus comprising: 7. The plasma processing apparatus according to claim 6, wherein the small-diameter coaxial waveguide has a small-diameter coaxial waveguide impedance Z0 (= 60 ln (R3 / R4), R3: radius of a conductor outside the coaxial waveguide, and R4: coaxial. The internal conductor radius) and the impedance Z1 (= 60b / R3, b: distance between parallel disks) on the disk waveguide side at the junction with the disk waveguide match, and the enlarged coaxial waveguide impedance Z2 ( =
60 ln (R2 / R1), R2: radius of outer conductor of coaxial tube, R
1: conductor radius in the coaxial waveguide) and impedance Z1 (= 6) on the disc waveguide side at the junction with the disc waveguide
0b / R1) so that R1, R2, R3, R
4. A plasma processing apparatus, wherein b is selected. 8. The plasma processing apparatus according to claim 6, wherein said enlarged coaxial waveguide has an outer diameter R2 of said enlarged coaxial waveguide.
However, the plasma processing apparatus is characterized in that it is smaller (R2 <R5) than the inscribed R5 of the processing chamber connected to the microwave vacuum window. 9. The plasma processing apparatus according to claim 6, wherein the microwave used has a frequency in a range of 500 MHz to 5 GHz. 10. The plasma processing apparatus according to claim 6, wherein said microwave uses a plurality of microwave sources having different frequencies at the same time. 11. The plasma processing apparatus according to claim 6, wherein the microwave uses a microwave source whose frequency is variable. 12. The plasma processing apparatus according to claim 6, wherein the microwave introduction vacuum window is used to generate plasma in a portion of the vacuum window other than a portion corresponding to a microwave radiating portion (R1 <R <R2). A plasma processing apparatus characterized in that an earth conductor plate or a semiconductor plate such as Si or SiC is provided in a contact portion. 13. The plasma processing apparatus according to claim 6, wherein the microwave introduction vacuum window uses a portion of the vacuum window other than a portion corresponding to a microwave radiating portion (R1 <R <R2). And a processing gas introduction means. 14. A plasma processing apparatus according to claim 6, wherein said microwave introduction vacuum window uses a portion other than a portion corresponding to a microwave radiating portion (R1 <R <R2) to form a magnetic field coil or a permanent magnet. A plasma processing apparatus comprising: 15. The plasma processing apparatus according to claim 6, wherein said parallel-plate disk-shaped waveguide has two small-diameter and large-diameter ring-shaped openings, and each of said openings has
A plasma processing apparatus having a configuration in which an enlarged coaxial waveguide is connected. 16. The plasma processing apparatus according to claim 6, wherein said enlarged coaxial waveguide has means for variably distributing microwave power to two enlarged coaxial waveguides. . 17. The plasma processing apparatus according to claim 6, wherein said microwave introducing device converts the microwave into a coaxial TEM.
A plasma processing apparatus characterized in that transmission is performed in a mode.