JPH01184921A - Plasma processor useful for etching, ashing, film formation and the like - Google Patents

Abstract

PURPOSE:To enable plasma to be produced efficiently as well as 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 means of material gas, a magnetic field generating means and a microwave leading means using a radiating member with multiple coaxitial tube structure. CONSTITUTION:Microwaves converted to coaxial tubes to be led into a reaction chamber are aligned with plungers 11, 13, 14 from a waveguide 6 located on the topmost position so that the microwaves may be led into the coaxial tubes using an inner conductor 10 as a rod antenna. These coaxial tubes pass through the other waveguides 8, 9 to lead the microwaves from the waveguide 8 to the coaxial tubes 12-15. Likewise, the microwaves led from the waveguide 9 to the coaxial tubes 15-16 are radiated from microwave radiating members 11-19 to discharging space 4 through a microwave transmitting window. At this time, the power of microwaves fed to respective waveguides can be controlled to freely change the plasma density in respective discharge regions drawing concentric circles from the center of antenna so that the processing rate of an element 3 to be processed may be equalized extending over all surface.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field 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 suitable for etching, sputtering, cleaning, or ashing of an object to be processed, and for forming a film on a substrate.

[Description of prior art]

Plasma processing method 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, deposited film formation, sputtering, cleaning, and ashing. It refers to a processing method that performs processing such as (ashing), and the 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. The ability to scale as desired is a feature of the plasma processing method, and what is important in the plasma processing method is the 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 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. Use processing. In particular, if the magnitude of the magnetic field is determined so that the cyclotron frequency of electrons and the frequency of microwaves are partially equal, plasma can be generated efficiently. Commonly used 2.45GHz
, the magnitude of the 6n field is 875 Gauss.

The advantage of this plasma processing technology is that the discharge pressure range is wider from 10-4 to 1 O Torr 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. ,0
．． At a pressure of 1=10 Torr, a large amount of excited gas can be generated. 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 equipment, 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 not generated within the discharge chamber.

Incidentally, Japanese Unexamined Patent Publication No. 120525/1983 discloses a microwave plasma processing apparatus as shown in FIG.
In the figure, 401 is a discharge chamber, 402 is a processing chamber, 403 is a microwave introduction window, 404 is a rectangular waveguide, 405 is a plasma flow, 406 is a plasma extraction window, 407 is a sample, 408
409 is the sample stand, 410 is the exhaust system, 41
1 is a magnetic coil, 412 is a magnetic shield, 413 is a first
A gas introduction system, 414 a second gas sensing system, and 415 a cooling water inlet and drain port.

To generate plasma using the device, exhaust system 410
The discharge chamber 401 and the processing chamber 402 are evacuated to a high vacuum by
First gas introduction system 413 or/and second gas introduction system 414
A gas is introduced into the plasma discharge chamber 401 at a pressure of 10-h to 1 Torr, and microwaves from a microwave R (not shown) are introduced into the plasma discharge chamber 401 through a rectangular waveguide 404 and a microwave introduction window 403. At the same time, a magnetic coil 411 disposed around the discharge chamber 401 applies a magnetic field satisfying electron cyclotron resonance conditions to at least a portion of the discharge chamber.

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 401 is equipped with a microwave cavity resonator to increase the microwave electric field strength and discharge efficiency. The system is configured to meet the following conditions. For example, T E +
In the +3 cylindrical cavity resonance mode, the inner rectangular dimension is diameter 1
It is said to be 7cm and 20cII+ in height. In order to satisfy the resonance mode, the microwave transmission window is preferably small in size. Incidentally, in the conventional example, a waveguide having the same size as the inner cross section of a microwave introducing waveguide (usually JIS standard WRJ-2 (inner diameter 109.22 mm x 54.61 mm) is used) is used. Plasma generated in the discharge chamber with the above configuration is supplied to the sample 407 through the plasma extraction window 406. When plasma is generated, the introduced microwaves are absorbed by the plasma near the microwave introduction window 403 in the discharge chamber. This tendency 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 406 is narrowed down, but in that case, the area to which plasma is supplied is limited, and the plasma inside the discharge chamber is not effective. The problem is that it is not used.

[Purpose of the invention]

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

Another object of the present invention is to provide a specific microwave radiation means in the microwave introduction means to the discharge space in the vacuum container, so that the microwave can be smoothly supplied to the discharge space in the vacuum container. The plasma is generated efficiently and in a controlled distribution state, and the generated plasma can efficiently perform controlled etching or ashing of the sample and deposition of a film on the substrate. An object of the present invention is to provide a plasma processing apparatus.

[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 radiating member having a multiple coaxial tube structure.

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 diagram showing a typical example of the apparatus of the present invention. In FIG. 1, ■ is a vacuum container, 2 is a holder for an object to be processed, 3 is an object to be processed, 4 is a discharge space where electric discharge occurs, and 5
? is an air-core coil for forming a magnetic field in the reaction chamber 4; 6 is a gas inlet for introducing processing gas; ? , 8.9 indicate the waveguides, respectively. And 10.12,15. ．．
Reference numerals 16 and 13 respectively indicate coaxial pipe conductors for introducing microwaves from the waveguides, and plungers 11, 13, and 14 respectively perform matching when converting the microwave propagation path from the waveguide to the coaxial pipe. Reference numerals 17 to 19 indicate microwave radiating members in the form of expanded tips of coaxial tubes, 20 indicates a microwave transmission window for transmitting microwaves and sealing vacuum, and 21 indicates a cover. A high frequency power source for supplying high frequency power to the processing object holder 2 is shown.

The operation of the apparatus shown in FIG. 1 is carried out, for example, as follows.

That is, the inside of the vacuum container 1 is kept at a pressure of 10-' to 10-hTorr or less in advance by an exhaust system (not shown). Next, a reaction gas used for processing is introduced through the gas inlet 24 to a predetermined pressure.

For example, in the case of Si-based etching, SF or the like is used as the reaction gas, and the operating pressure during processing is 10-3To.
It can be done on rr machine. The microwaves generated by the microwave oscillator are divided by the number of waveguides by a microwave distributor (three systems here), and the waveguides are stacked in parallel through a power controller that controls the intensity of each waveguide, and a phase converter. 7. 8. Guided by 9. From there, the microwave is further converted into a coaxial tube and introduced into the reaction chamber.

At this time, first, from the waveguide 6 located at the top, matching is performed using the plungers 11, 13. It will be destroyed. The second coaxial tube passes through the waveguide 8.9 below it, and at this time the outer conductor 12
is used as a new internal conductor, and microwaves are guided from the waveguide 8 between 12 and 15. Similarly, from waveguide 9 to coaxial tube 1
Microwaves are introduced between 5 and 16. The microwaves propagating through each layer of the coaxial tube are radiated from the microwave radiating members 11 to 19 into the discharge space 4 through the microwave transmission window.

The material for the microwave-transmitting window is preferably a microwave-transparent substance such as quartz, alumina, or boron nitride. Processing body 3
Here, as shown in Figure 2, the introduction of microwaves is controlled independently from the microwave oscillators and the waveguides. , 8. 9 and control microwaves. At this time, by controlling the microwave power supplied to each waveguide, it is possible to freely change the plasma density on each discharge head, which is concentrically formed from the center of the antenna. It becomes possible to make the processing speed of the processing body 3 uniform over the entire surface.

It is also possible to control the microwave power radiated from each radiating member and process the desired distribution. In Fig. 1, a three-layer structure is shown, but in general, an n-layer structure may be used.
The more multiplexed, the more detailed control becomes possible. Furthermore, by stopping discharge in unnecessary areas depending on the size of the object to be processed, strong discharge can be generated only in necessary areas with the same electric power.

In addition, the processing object holder 2 is a high frequency type A21 (usually 13
．． By supplying high-frequency power higher than 56 MHz, ions incident on the sample can be accelerated by the plasma generated thereby and the bias voltage generated in the object to be processed. The bias voltage at this time can be controlled by high frequency power, and thereby the incident ions can be controlled, making it possible to perform processing with good controllability.

FIG. 3 shows another representative example of the plasma processing apparatus of the present invention. In FIG. 3, 22 is a processing chamber, 23 is a discharge vessel of the ion source, and 24° and 24'' are gas inlet ports for introducing reaction gas into the ion source. 25 is a
The inner container is made of a material that insulates plasma and transmits microwaves. Reference numerals 26, 27, and 28 indicate an extraction electrode that extracts ions from the plasma generated by the ion source and accelerates them to a predetermined energy. 29, 30 indicates a DC power supply for applying a DC voltage to the electrodes.

This example is an example in which the apparatus according to the present invention is applied to an ion beam processing apparatus. The example device is operated, for example, as follows. That is, after both the processing chamber and the ion source are evacuated to a pressure of 1 x 10-'' Torr or less by an evacuation system (not shown), the reaction gas is introduced into the ion source through the gas inlet 24, and in the above example, Discharge space 4 in the method described
A discharge with arbitrarily distributed plasma density is generated.

Separately, a processing gas may be simultaneously introduced from the 24' to process the generated plasma.
Processing is performed by applying 0V to +3 kV to extract ions, accelerating them at a predetermined voltage, and irradiating the object to be processed. In the case of an ion beam processing apparatus, since the ion extraction electrode 25 exists as a factor that greatly affects the uniformity, controlling the plasma density distribution according to the present invention has a great effect. Although the structure using electrodes is shown, the same effect can be obtained by using one or two electrodes.

EQUIPMENT EXAMPLE 1 A case will be described in which a 5ift etching of a Si substrate having an Si0g film is performed using the apparatus shown in FIG.

First, the inside of the vacuum container was evacuated to below 10-" Torr, and etching gas CgFa was introduced from the gas inlet 6. The exhaust system was adjusted to reduce the pressure in the discharge space 4 to 1
It was set at 10-'Torr. 13. From high frequency power supply.
A high frequency wave with a power of 56 MHz and 200 W was applied, and a microwave with a power of 200 W was oscillated from a microwave oscillator, and the power controller, phase converter, and plungers 11, 13, and 14 were adjusted, and the reflected microwave was
Etching was carried out for a predetermined period of time under conditions that allowed etching to be kept at 0 W or less and with good uniformity, and desired etching results were obtained. The results showed good uniformity, and compared to numerical RIF, the bias voltage could be lowered to 100 V or less, resulting in etching with less damage.

Apparatus Usage Example 2 A case will be described in which the apparatus shown in FIG. 1 is used to ash a resist (novolac type) applied to a Si substrate.

First, the inside of the vacuum container was evacuated to below I.times.10-' Torr, and etching gas 0□ was introduced from the gas inlet 6. Adjust the exhaust system to reduce the pressure in the discharge space 4 to 3 x 10
−'Torr.

A microwave with a power of 200 W is oscillated from a microwave oscillator, and the power controller phase converter and plungers 11, 13. Ashing was performed for a period of 20 minutes to obtain the desired etching result. The results showed good uniformity, and because the ashing was performed at low pressure, there was no residue, and the ion energy was less than 20 eV, so ashing was possible with little damage.

[Summary of effects of the invention]

As explained above, the present invention provides the following special effects. In other words, in a plasma processing apparatus using microwave discharge, by supplying independent microwaves from each layer of a coaxial tube with a multilayer structure and emitting them concentrically, the uniformity of the processing speed for one object to be processed is improved. do.

Further, the discharge area can be limited depending on the size of the object to be processed.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view of a plasma processing apparatus embodying the present invention, and FIG. 2 is a wiring diagram of a microwave supply section when microwaves are supplied from an independent microwave oscillator. FIG. 3 is a schematic cross-sectional view of an apparatus for extracting ions from plasma. FIG. 4 is a schematic cross-sectional view of a conventional plasma processing apparatus. Regarding FIG. 1, 1... Vacuum device, 2... Object holder, 3... Object to be processed, 4... Discharge space where electric discharge occurs, 5... Air core coil, 6...・Gas inlet, 7
．． 8゜9...Waveguide, to, 12.15.16...
Coaxial pipe conductor, 11, 13.14... plunger, 1
7-19...Microwave radiation member, 20...Microwave transmission window, 21...High frequency power supply. Regarding Fig. 3, 22...processing chamber, 23...discharge vessel, 24.24'...gas inlet, 26, 27.28
...Ion extraction electrode, 29.30...DC power supply. Regarding FIG. 4, 401... plasma discharge chamber, 402
...Processing room, 403...Microwave introduction window, 404
...Rectangular waveguide, 405...Plasma flow, 406.
...Plasma drawer window, 407...Sample, 408...
- Sample mounting table, 409... Sample stand, 410... Exhaust system, 411... Magnetic coil, 412... Magnetic shield, 413... First gas introduction system, 414... Second gas Introduction system, 415...Cooling water supply port, drain port.

Claims (4)

[Claims] (1) A plasma processing apparatus comprising a vacuum vessel having a discharge space, and the vacuum vessel having at least a means for introducing raw material gas, a means for generating a magnetic field, and a means for introducing microwaves, 1. A plasma processing apparatus characterized in that a radiation member having a multi-coaxial tube structure is used as an introduction means. (2) The plasma processing apparatus according to claim 1, wherein microwaves are supplied to the multiple coaxial tubes from independently controlled microwave oscillators. (3) A microwave power controller and/or a phase converter is provided in the middle of supplying microwaves to each coaxial tube of the multiple coaxial tubes, as set forth in claim 1. Plasma processing equipment. (4) The propagation path of microwaves supplied to the multiple coaxial tubes is converted from a waveguide to a coaxial tube on the coaxial line of the multiple coaxial tubes. Plasma processing equipment.