JPH01184922A - Plasma processor useful for etching, ashing, film formation and the like - Google Patents

Abstract

PURPOSE:To produce plasma enabling it to be used effectively for the purpose such as etching, ashing, filming etc., by a method wherein a vacuum vessel is provided with a leading-in means and a microwave leading-in means using a microwave radiating member on a flat plate with a notch part. CONSTITUTION:Microwaves oscillated by a microwave oscillator (c) are fed to an isolator (b) absorbing the microwaves fed back to the oscillator through a waveguide and then further fed to a coaxial converter (a) with a tuner for alignment with a microwave launcher 103. Then, the microwaves are converted to a coaxial tube to be fed to the microwave launcher 103. Furthermore, a processing gas is fed from a gas leading-in port 102 while the microwaves are radiated from a slit of mask to a discharging chamber 107 to produce plasma efficiently by the magnetic field magnetron effect brought about by the electric field of microwaves and an air-core coil.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technology to which the invention pertains] The present invention relates to a plasma processing apparatus. More specifically,
The present invention relates to a plasma processing apparatus that uses plasma to perform etching, sputtering, cleaning, or ashing of an object to be processed and to form a film on a substrate.

[Description of prior art]

Plasma processing involves turning a specific substance into plasma to generate highly active radicals and ions, and bringing these radicals and ions into contact with the object to be processed, etching, forming a deposited film, spanking, cleaning, etc. It refers to a processing method that performs processing such as ashing (ashing), and a plasma processing apparatus refers to an apparatus used to implement the plasma processing method.

Conventionally, such plasma processing apparatuses include a plasma processing chamber formed of a vacuum container having a raw material gas inlet and an exhaust port, and an electromagnetic wave that supplies energy to turn the raw material gas supplied to the plasma processing chamber into plasma. It consists of a supply device.

By the way, the plasma processing method relies on the strong activity of radicals and ions mentioned above, and by appropriately selecting the density of radicals and ions, the temperature of the object to be processed, etc., various treatments such as etching and deposited film formation can be performed. It is a feature of the plasma processing method that it can be performed as desired, and what is important in the plasma processing method is efficient generation of radicals and ions.

Conventionally, as a medium that provides plasma energy, 1
High-frequency electromagnetic waves of about 3.56 MHz were used, but in recent years it has been found that high-density plasma can be generated efficiently by using microwaves of about 2.45 GHz, and plasma using microwaves has been developed. Treatment methods are attracting attention, and several devices have been proposed for this purpose.

For example, amorphous silicon (hereinafter referred to as rA-3iJ) is used as an element member used in semiconductor devices, electrophotographic photoreceptors, image input sensors, imaging devices, photovoltaic elements, various other electronic elements, optical elements, etc. ) A method of forming a deposited film by a plasma CVD method using microwaves (hereinafter referred to as "rMW-PCVD method") and an apparatus therefor have been proposed.

This plasma processing technology uses an electric field generated by microwaves and a magnetic field generated by a magnetic field generator placed outside the discharge chamber to efficiently accelerate electrons, collide with neutral molecules, and ionize them to generate high-density plasma. process. In particular, if the magnitude of the magnetic field is determined so that the cyclotron frequency of electrons and the frequency of microwaves match, plasma can be generated efficiently. Commonly used 2.45GHz
For , the magnitude of the tK tn field is 875 Gauss.

The advantage of this plasma processing technology is that the discharge pressure range is 10-4 to 10 Torr, which is wider than that of the high-frequency discharge type.
At low pressures such as 0 to 10 Torr, the mean free path of ions becomes larger than the ion sheath width. For example, in an etching device, ions enter the sample perpendicularly, making vertical etching possible. Also,
A large amount of excited gas can be generated at a pressure of 0.1 to 10 Torr. Furthermore, since the energy of ions incident on the sample is as low as 20 eV, processing can be performed without damaging the sample.

However, in conventional plasma processing technology, microwaves are supplied to the discharge chamber through a microwave introduction window that is smaller than the cross section of the discharge chamber. There is a problem in that the plasma is absorbed by nearby plasma and a uniform plasma is no longer generated within the discharge chamber.

Incidentally, Japanese Unexamined Patent Publication No. 120525/1988 discloses a microwave plasma processing apparatus shown in FIG. 7.

In the figure, 701 is a discharge chamber, 702 is a processing chamber, 703 is a microwave introduction window, 704 is a rectangular waveguide, 705 is a plasma flow, 706 is a plasma extraction window, 707 is a sample, 708
is a sample mounting table, 709 is a sample table, 710 is an exhaust system, 71
1 is a magnetic coil, 712 is a magnetic shield, 713 is a first
A gas introduction system, 714 is a second gas introduction system, and 715 is a cooling water supply port and a drain port.

To generate plasma using the device, exhaust system 710
The discharge chamber 701 and the processing chamber 702 are evacuated to a high vacuum by
First gas introduction system 713 or/and second gas introduction system 714
Introduce more gas to a pressure of 104 to I Torr,
Microwaves are introduced from a microwave source (not shown) into the plasma discharge chamber 701 through a rectangular waveguide 704 and a microwave introduction window 703, and at the same time a magnetic coil 711 disposed around the discharge chamber 701 is used to introduce at least one part of the discharge chamber. A magnetic field that satisfies the electron cyclotron resonance conditions is applied to a part of the system. .

When a 2.45 GHz magnetron is used as a microwave source, the electron cyclotron resonance condition is a magnetic flux attitude of 875 G, and the discharge chamber 701 is a microwave cavity resonator to increase the microwave electric field strength and discharge efficiency. For example, T E +
In the cylindrical cavity resonance mode of 13, the inner rectangular dimension is diameter 17
cffl and has a height of 20 cm. In order to satisfy the resonance mode, the microwave transmission window is preferably small in size. Incidentally, in the conventional example, a waveguide for introducing microwaves (usually JIS standard WRJ-2 (inner diameter 1
09.22m x 54.61m) is used. Plasma generated in the discharge chamber with the above configuration is supplied to the sample 707 via the plasma extraction window 706. When plasma is generated, the introduced microwave is absorbed by the plasma near the microwave introduction window 703 in the discharge chamber. This trend is
The plasma density increases as the plasma density increases, and in that case, microwaves no longer propagate inside the discharge chamber.

As a result, uniform plasma is no longer generated within the discharge chamber, making it impossible to perform uniform processing. In order to avoid this problem and perform uniform processing, the plasma extraction window 706 is narrowed down, but in this case, the area to which plasma is supplied is limited, and the plasma inside the discharge chamber is not effective. There is a problem that it is not used.

On the other hand, in the fields of microwave communication and radar, which are completely different from the relevant technical field, antennas with slots (or slits) in a flat plate have been developed (F. J. Goebels,
and K, C, Kelly, I RETran
actions on Antenna and P
ropagation.

AP-9, July, P342, 1961), and has recently been further developed and improved for satellite broadcast reception (Naohisa Gogo, Masaki Yamaki, Technical Research Report of the Institute of Electronics and Communication Engineers, A.
-P2O-57, Pd2, 1980, or Hideo Sasazawa, Yasuhide Oshima, Denka Sakurai, Makoto Ando, Naohisa Gogo, Institute of Electronics and Communication Engineers Technical Research Report, A-P86-142. P29.198
6).

However, these flat plate slot antennas are mainly intended for application to microwave communications, radar, etc., and are not intended for application to plasma generation at all.

[Purpose of the invention]

The present invention solves the above-mentioned problems in conventional plasma processing apparatuses, efficiently generates plasma, and effectively utilizes the generated plasma for purposes such as etching, ashing, and film formation. The main objective is to provide an improved plasma processing apparatus.

Another object of the present invention is to provide specific microwave radiating means in the microwave introducing means of the vacuum container, so that the microwave can be smoothly supplied to the discharge space of the vacuum container, and plasma can be efficiently generated in the discharge space. An improved plasma processing apparatus that can efficiently perform uniform processing, notching or ashing of a sample, and uniform film formation on a substrate using plasma that is generated in a uniformly and uniformly distributed manner. It is about providing.

[Structure and effects of the invention]

The present invention solves the above-mentioned problems in conventional plasma processing apparatuses and achieves the above objects. An improved plasma processing apparatus includes at least an introducing means, a magnetic field generating means, and a microwave introducing means, and the microwave introducing means uses a flat microwave emitting member having a notch.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The plasma processing apparatus of the present invention having the above-mentioned configuration will be described in detail below with reference to embodiments of the drawings.

FIG. 1 is a schematic cross-sectional view of a typical plasma processing apparatus according to the present invention. In FIG. 1, +01 is a vacuum container for keeping the processing section in vacuum, 102 is a gas inlet for introducing processing gas into the vacuum container, and 103 is a microwave launcher for emitting microwaves. 107 is a discharge chamber where plasma exists, and 104 is a discharge chamber in which microwaves are transmitted to the discharge chamber 107.
This is a mask with slits made in a conductor plate that emits light, and an example of a spiral mask is shown in Figure 2.

In FIG. 2, 201 indicates a vortex-shaped slit, and microwaves are supplied through this slit. Further, 105 is a microwave transmitting window made of a dielectric material such as quartz, alumina, boron nitride forsterite, etc., and the microwave launcher 103 and the discharge chamber 107
Vacuum seal between. 106a is a coaxial outer conductor for supplying microwaves to the microwave launcher 103;
106b is an inner conductor connected to the center of the mask 104. 108 is a sample to be processed, 109 is a sample holder,
110 is a vacuum exhaust system for maintaining the processing pressure in the discharge chamber;
111 is an air-core coil for generating a magnetic field within the discharge chamber.

In the above configuration, the microwave (usually 2.450H2) generated by the microwave oscillator is supplied by a waveguide to an isolake that absorbs the microwave returning to the microwave oscillator, and is further matched with the microwave launcher 103. The waveguide is then sent to a coaxial converter with a tuner to convert it from a waveguide to a coaxial tube, and then a microwave launcher.
103. On the other hand, a processing gas, for example, CI gas for etching a Si substrate, SiH4 gas for amorphous Si film formation, 0 gas for resist ashing, is supplied from the gas inlet 102, and microwaves are supplied from the slit 201 of the mask to the discharge chamber 107. plasma is efficiently generated by the magnetron effect of the microwave electric field and the magnetic field generated by the air-core coil. In addition, the magnitude of the magnetic field is set to the same value as the electron cyclotron frequency and the microwave frequency (875 GHz in the case of 2.45 GH, 2
Gauss), electrons are resonantly heated and plasma is generated more efficiently. The sample 108 is processed by ions and radicals present in the plasma of the processing gas generated in the discharge chamber 107.

Plasma density, temperature, and ion valence, which have a strong influence on sample processing, depend on the intensity of the emitted microwaves.

Therefore, in order to perform processing with good uniformity over the entire surface of the sample, the intensity distribution of the emitted microwave must be made uniform in a plane parallel to the sample surface, which is due to the slit width S of the spiral slit. , by changing the slit interval d (see FIG. 2). For example, if the intensity of the microwave is strong at the center, the slit interval d is increased at the center and decreased at the periphery. The width of the slit can also be determined in the same manner. The shape of the slit described here is not limited to the spiral shape, but the same effect can be obtained by using any shape such as a concentric circle or a shape having a large number of cross slots.

After plasma is generated, microwaves are absorbed in the discharge space near the microwave window, as described above.

However, since the direction of the magnetic flux density of the magnetic field generated by the air-core coil 111 is perpendicular to the surface of the sample 108, the generated plasma does not spread much in the direction perpendicular to the sample surface along this magnetic field, and is efficiently It reaches the surface of the sample 108 and performs the desired treatment.

Also, move the sample holder 109 from 1/2 to 1/1 from the strongest magnetic field.
By moving the plasma away to a point where it becomes about 0, it is possible to obtain divergence and acceleration of the plasma by the magnetic field, which can also accelerate the processing.

The means for supplying microwaves to the microwave launcher 103 is not limited to a coaxial tube. Regarding this point, FIG. 3 shows a method using a waveguide. In FIG. 3, numeral 306 is a waveguide that supplies microwaves to the microwave launcher 303, and the same reference numerals as in FIG. 1 indicate the same components as in FIG.

Although not shown in the apparatus shown in FIG. 3, the microwave oscillated by the microwave oscillator absorbs reflected waves by the circulator, is matched with the load side by the tuner, and is connected to the microwave launcher by the waveguide 306. 303. The microwaves are radiated into the discharge chamber 107 through the slits of the slitted mask 104 as shown in FIG. 2, generate plasma in the same manner as in the previous embodiment, and process the sample 108.

As the next embodiment, a device for applying high frequency power to the sample holder 109 is shown in FIG. In Figure 4, 412
is an insulator for electrically insulating the sample holder, 41
3 is a high frequency power supply for supplying high frequency power to the sample holder, and 414 is a capacitor for floating the holder in direct current. Other components denoted by the same reference numerals as in FIG. 1 indicate the same components as in FIG.

To explain the operation of this device, plasma is generated in the discharge chamber 107 using microwave waves in the same manner as in the embodiment described above. At the same time, when high frequency power is applied to the sample holder,
Since the sample holder is DC-floated by the capacitor 414, it is negatively biased and the sample 118
The bias voltage accelerates the ions toward the ion, facilitating processing by the ions. The energy of the ions is determined by the bias voltage, and the bias voltage is determined by the radio frequency power, so the energy of the ions can be controlled by the radio frequency power.

In the case of etching, for example, in 5 in 2 etching, which requires a certain amount of ion energy, the ion energy can be controlled to avoid damage caused by ion collisions (and to obtain an appropriate etching rate).

In addition, in film deposition of SiO, the energy of ions is controlled and the film is deposited while moderate etching by ion bombardment is simultaneously progressing, thereby eliminating unevenness on the film and forming a flat film.

The frequency of the high frequency used is 2 to 3 MHz or more, and the energy of ions can be controlled by a bias voltage, and an industrial high frequency of 13.56 MHz is usually used. on the other hand,
At a high frequency of 2 to 3 MHz or less, the energy of ions cannot be controlled by bias voltage, but since the ions are directly accelerated by the high frequency electric field, the energy of ions can be controlled in the same way. The frequency usually used is 1
The range is from 00KH2 to 500K112. In this case, the high frequency may be applied not to the sample holder but to the opposing microwave launcher 103. This is because the slit-to-nod spacing is usually 100C11 or less, and the slit width S is 1 cm or less, so high frequency (≦13.56MHz)
This is because it can be regarded as a flat plate.

An example is shown in FIG. In FIG. 5, 515 is a device for blocking high frequency waves from going to the coaxial converter with tuner, and for example, it may have a choke structure commonly used in microwave circuits, and 516 is a device for blocking high frequency waves from going to the coaxial converter with tuner. This is an insulator for electrically insulating the parts, and the same reference numerals as in FIGS. 1 and 4 indicate the same parts as in FIGS. 1 and 4. Next, the operation of this device will be explained. Similar to the embodiment shown in FIG. 4, plasma is generated in the discharge chamber 107 by microwaves, and the microwave launcher is
A high frequency wave is applied to the whole, and a high frequency electric field is generated between the conductor plate 104, the plasma, and the sample holder (or sample), and the ions are accelerated by this electric field, resulting in etching, ashing,
Film formation etc. can be performed efficiently.

On the two sides to which high frequency waves are simultaneously applied as described above, the conductor plate 104 and the sample holder 109 act as opposing electrodes of the parallel plate type reaction device, so the high frequency electric field is simply applied to one side, and unlike the case where there is no opposing flat plate electrode, there is a mask. - A uniform high frequency electric field is generated between the plasma and the sample holder, allowing uniform etching, ashing, film formation, etc.

As the next example, FIG. 6 shows an apparatus in which ions are extracted from plasma generated in the discharge chamber 107 using an electrode group and irradiated onto a sample 10B for treatment.

In Fig. 6, 617 is an insulating inner container made of quartz, alumina, boron nitride, forsterite, etc. that transmits microwaves and is used to insulate the plasma generated in the discharge chamber from the vacuum vessel; TL poles for ion extraction with holes opened and the holes optically aligned with each other; 621° and 622 are DC power sources for applying DC voltage to extraction electrodes 618 and 619; 623 is a processing chamber; 102° is installed in the processing chamber. This is the gas inlet.

To explain the operation of the apparatus shown in FIG. 6, microwaves emitted from the slits or slots of the conductor plate 104 pass through the insulating inner container 618 and are supplied to the discharge chamber 107.

Next, processing gases such as N2 gas are introduced from 102 and SiH4 gas is introduced from 102' when depositing a SiN film on a Si substrate as a sample.

The discharge chamber 10 is
Plasma is generated within 7, and the plasma diffuses along the magnetic lines of force and reaches the ion extraction electrode 618. Ions (mainly N", N2") in the plasma have a direct flow rate of #62
2 to get the energy depending on the applied voltage,
In addition, the spread of ions is controlled by the voltage applied by the electrode 619, and the sample 108 placed on the sample holder 109 installed in the processing chamber 623 is irradiated with S i H
4 to deposit a SiN film. The extraction electrodes need not be limited to the three-layer structure shown in FIG. 5, and the same effect can be obtained with one or two electrodes.

The distribution of ions extracted from the plasma chamber 107 largely depends on the distribution of plasma in the plasma chamber, and a uniform ion beam is generated by generating uniform plasma by emitting microwaves from a conductor plate with slits. Obtainable. With this ion beam, 10
By etching under the pressure of the -' Torr stage, the ion beam with the same direction reaches the sample, and etching proceeds in the direction of ion travel, making anisotropic etching possible.

Etching Example A case will be described in which a Si substrate is used as the sample 118 in the apparatus shown in FIG. 1, and Si is etched.

First, a Si substrate is placed on the sample holder 109.

Next, the inside of the vacuum container 101 is evacuated to an internal pressure of 2×10-” Torr or less using the evacuation system 110. Next, etching gas C12 is introduced from the gas inlet 102, and the pulp (not shown) in the evacuation system is evacuated. Adjust the conductance of the tube and set the internal pressure to 3 x 10-'' Torr. Next, the microwave oscillator is energized to oscillate a 2.45 GHz, 200 W microwave, and the tuner of the coaxial converter with tuner is adjusted so that the reflected power is 30 W or less.
Microwaves are radiated through slits made in the conductor plate 104 to generate plasma in the discharge space 107. cz", czt"" ions and radicals C18°C in plasma
1! * Etches the Si substrate. After being etched for a predetermined period of time, it was taken out and the amount of etching was measured, and it was found that the etching was well-uniform.

Resist Ashing An example of novolac-based resist ashing applied on a Si substrate as a sample 118 in the apparatus shown in FIG. 1 will be described.

First, a Si substrate with a resist attached is placed on a sample holder 109.
The inside of the chamber is evacuated to an internal pressure of 2 x 10-'' Torr or less. Next, 200 sec of 0.0 gas is introduced from the gas inlet 102, the conductance of the pulp (not shown) in the vacuum evacuation system is adjusted, and the internal pressure is reduced to 2. energize the zero-order microwave oscillator set to ×10-”Torr, 2.45GHz,
A 500 W microwave is oscillated, a tuner of a coaxial converter with a tuner is adjusted so that the reflected power is 30 W or less, and the microwave is radiated from a slit made in the conductor plate 104 to generate plasma in the discharge space 107. generate. This plasma is exposed to a resist, and 01,0□ in the plasma. ion, 0. ．． Ashing of the resist is performed using 0'' radicals. After performing ashing for a predetermined time, the resist was taken out and the amount of ashing was measured, and it was found that ashing with good uniformity was achieved.

Example of forming an a-3i deposited film A case will be described in which an a-3i deposited film is formed on a quartz substrate as a sample 118 using the apparatus shown in FIG.

First, a quartz substrate is placed on the sample holder 109.

Next, the inside of the vacuum container 101 is pumped by the vacuum evacuation system 110.
Degas to an internal pressure of X 10-'' Torr or less. Next, 20 sccm of 5iHn gas is supplied from the gas inlet 102.

Introducing 8 sccm of Ht gas and pumping the pulp (
(not shown) and adjust the internal pressure to 1×1O
-3 Torr. Next, the microwave oscillator is energized to oscillate a 2.45 GHz, 500 W microwave, the tuner of the tuner-equipped coaxial converter is adjusted so that the reflected power is 30 W or less, and the slit made in the conductor plate 104 is Microwaves are emitted to generate plasma in the discharge space 107. This plasma is exposed to a quartz substrate, and a-3i is deposited for a predetermined period of time to obtain a film of a desired thickness. The deposited film thus obtained was a-3i:H,
When this was subjected to various tests, a uniform and homogeneous film was obtained.

[Summary of effects of the invention]

As explained above, according to the plasma processing apparatus of the present invention, which uses a flat plate with slits (or slots) to supply microwaves, the uniformity of plasma processing is improved, and the microwaves are applied only to the processing section. Since it can supply waves, it can efficiently supply microwaves.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of a plasma processing apparatus embodying the present invention, Fig. 2 is a plan view of a mask having spiral slits, and Fig. 3 shows microwaves supplied by a waveguide. It is a partial sectional view of the microwave supply part in the case of supplying microwaves. FIG. 4 is a cross-sectional view of the device that applies high-frequency power to the sample holder, No. 5 UfJ is a cross-sectional view of the device that applies high-frequency power to the microwave launcher, and No. 6 UfJ is a cross-sectional view of the device that applies high-frequency power to the microwave launcher.
The figure is a cross-sectional view of a device that extracts and processes ions from a discharge chamber. Furthermore, FIG. 7 is a cross-sectional view of a conventional microwave plasma. Regarding FIG. 1, 101... vacuum container, 102...
Gas inlet, 103...Microwave launcher-110
4...Slit or slotted conductor plate, 105...
Microwave transmission window, 106a... Coaxial tube outer conductor, 10
6b... Coaxial pipe inner conductor, 107... Discharge chamber, 10B
...Sample, 109...Sample holder, 110...
Vacuum exhaust system, 111... air core coil. Regarding Fig. 2, 201... spiral slit. Regarding Fig. 3, 303...Microwave launcher-1
306... Waveguide. Regarding FIG. 4, 412... Insulator, 413... High frequency power supply, 414... Capacitor. Regarding FIG. 5, 516...Insulator. Regarding FIG. 6, 617... microwave transparent inner container;
61'8, 619, 620... Ion extraction electrode, 621, 622... DC power supply, 623... Processing chamber. Regarding FIG. 7, 701... plasma discharge chamber, 702
...Processing room, 703...Microwave introduction window, 704
... Rectangular waveguide, 705 ... Plasma flow, 706.
...Plasma drawer window, 707...Sample, 708...
- Sample mounting table, 709... Sample stand, 710... Exhaust system, 711... Magnetic coil, 712... Magnetic shield, 713... First gas introduction system, 714... Second gas Introduction system, 715...Cooling water supply port, drain port. Figure 2 Figure 3 Figure 7

Claims (6)

[Claims] (1) A plasma processing apparatus comprising a vacuum vessel having a discharge space, and the vacuum vessel having at least means for introducing a raw material gas for processing, a magnetic field generation means, and a microwave introduction means, the plasma processing apparatus comprising: A plasma processing apparatus characterized in that a flat microwave radiating member having a notch is used as a microwave introducing means. (2) The plasma processing apparatus according to claim (1), wherein a coaxial tube or a waveguide for supplying microwaves is coupled to the microwave radiation member. (3) The plasma processing apparatus according to claim (1), wherein the holding means for the sample to be processed or the substrate for film formation placed in the vacuum container is equipped with a high frequency supply means. (4) A part of the means for supplying microwaves to the microwave radiating member is provided with a means for blocking high frequencies, so that high frequencies can be supplied to the microwave radiating member ( The plasma processing apparatus according to item 1). (5) The discharge space processes the space (i) in which discharge occurs and the sample or forms a film on the substrate using an ion extraction electrode made of a conductive material provided in the space. Claim 1, characterized in that the electrode is selectively drawn out into the space (ii) from the plasma generated in the space (i). The plasma processing apparatus according to item 1). (6) The plasma according to claim (5), wherein the electrode is composed of one or more members made of a conductive material and having a plurality of gaps. Processing equipment.