JPH0666296B2 - Plasma processing device - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a plasma processing apparatus that decomposes a gaseous substance using plasma to perform a film forming process or an etching process on a sample surface. The present invention relates to an ECR microwave plasma processing apparatus which introduces waves to generate plasma by electron cyclotron resonance (ECR) and performs processing.

[Background of the Invention]

As a conventional ECR microwave plasma processing apparatus, a magnetic field having a desired magnetic field distribution and magnetic field strength is formed in a vacuum chamber, and a source gas of a predetermined pressure introduced into the vacuum chamber is irradiated with microwave power to generate a microwave electric field. There has been known a device for generating a plasma discharge by the interaction of the above magnetic field and decomposing the raw material gas to form a thin film on a predetermined substrate or perform an etching treatment, for example, JP-A-56-155535.
It is described in the official gazette.

FIG. 4 is a principle configuration diagram illustrating a conventional ECR microwave plasma processing apparatus described in the above publication. In FIG. 4, 1 is a plasma generation chamber forming a cavity resonator, 2 is a sample chamber, 3 is a microwave introduction window made of quartz glass, 4 is a rectangular waveguide, and a frequency of 2.45GH generated by a magnetron, for example.
Introduce microwave of z. A magnetic coil 5 forms a magnetic field in the plasma generation chamber 1 that satisfies the electron cyclotron resonance condition, for example, a magnetic field with a magnetic flux density of 875 G in the case of a microwave of 2.45 GHz and a divergent magnetic field in the sample chamber 2. It is for doing. Reference numerals 6 and 7 denote source gas introduction ports, and the gas introduction port 7 is necessary in the film forming process but not necessary in the etching process. Reference numeral 8 is a plasma extraction window, 9 is a sample stand, 10 is a sample substrate, 11 is an exhaust port, which is connected to a pump system for reducing the pressure during film formation to about 3 × 10 ^{−2 to} 5 × 10 ⁻⁵ Torr, for example. . 12 is an RF power supply and 13 is an impedance matching circuit.

With this configuration, the source gas (non-film forming gas) introduced from the gas inlet 6 into the plasma generation chamber 1 is decomposed and activated (plasma) by the plasma discharge by the microwave, and is diverged from the plasma extraction window 8 by the divergent magnetic field. It is pulled out to the sample chamber 2 side. In the case of the film forming process, another source gas (film forming gas) introduced into the sample chamber 2 from the gas inlet 7 reacts with the decomposition activation gas from the plasma generation chamber 1 in the sample chamber 2. Then, a thin film is formed on the surface of the sample substrate 10 on the sample table 9. In this case, since the energy of the ions incident on the substrate 10 is about 10 to 20 eV, it is possible to apply a negative bias to the sample stage 9 from the RF power source 12 via the impedance matching circuit 13 as necessary. . Applying a negative bias to such a substrate is particularly important when performing an anisotropic etching process.

The ECR microwave plasma processing device based on such a principle can discharge at a low gas pressure of (1) gas pressure of 3 × 10 ^{-2 to} 5 × 10 ^-5 Torr, and a high electron temperature (~ 8 eV) can be obtained. It can decompose difficult decomposable gas and can use a wide range of gas species.
(2) The incident energy of the ions is low (about 20 eV), and the kinetic energy of the incident ions can be controlled to some extent by applying an external voltage to the sample stage 9 if necessary. (3) In the treated film because of the electrodeless discharge In addition, there is a feature that contamination is small due to mixing of impurities, and anisotropic etching can be performed especially under the condition that plasma damage is small, and a high quality thin film can be formed at a low temperature.

However, in this conventional apparatus, a substantially uniform processing speed can be obtained in the processing area corresponding to the diameter of the plasma generation chamber (discharge chamber) in the case of the apparatus shown in FIG. 4, and there are many productivity problems. . If the uniform processing area is expanded by expanding the scale of the apparatus, a large electromagnet is required to maintain the magnetic density required for electron cyclotron resonance, which is not realistic. In order to increase the processing area, it is conceivable to arrange a plurality of substrates in parallel with the direction of the magnetic force line to perform the plasma processing apparatus, but simply disposing the sample in this way significantly deteriorates the uniformity of the processing speed. However, in the case of performing the film forming process, it is difficult to obtain the same result as in the case of setting the sample surface at right angles to the direction of the magnetic force line in terms of the film density and the film forming rate, and therefore it has not been conventionally used.

Further, in the conventional apparatus, in addition to the above-mentioned problem in productivity related to the uniform processing area, a negative bias can be applied from the RF power source 12 to the sample stage 9 in the case of anisotropic etching processing as a performance constraint. Although indispensable, the bias voltage that can be formed is limited to about 100 V because the wall of the sample chamber 2 plays the role of the counter electrode when the RF power is turned on. In addition, if a metal thin film or a highly conductive semiconductor thin film is to be formed in the case of a film forming process, a conductive film is likely to be adhered and formed on the microwave introduction window 3 and it is easy to block microwaves, so that practical use is practically impossible. There is a problem that the formation of the insulating film is limited.

[Object of the Invention]

The object of the present invention is to enable simultaneous treatment and etching treatment for a plurality of samples simultaneously and at a uniform treatment speed even when the area of each sample is large, and also to improve the condition. It is intended to provide a plasma processing apparatus capable of performing an anisotropic etching process and a film forming process of a highly conductive thin film.

[Outline of Invention]

To achieve the above object, a plasma processing apparatus according to the present invention converts a non-film forming gas introduced into a vacuum chamber into a plasma by a magnetic field formed in the vacuum chamber and a microwave introduced into the vacuum chamber. In addition, the non-film forming gas turned into plasma is directly applied to the sample substrate placed in the magnetic field, or indirectly in the presence of the film forming gas, whereby Etching process,
Alternatively, the film forming process is performed,
A vacuum chamber whose inside is evacuated by exhaustion, a magnetron for generating microwaves, a waveguide for propagating microwaves from the magnetron, and a microwave from the waveguide are introduced into the vacuum chamber. In order to allow the microwave to propagate to the vacuum chamber even when the conductive coating is attached to the inner wall surface, which also serves as a microwave introduction window for the vacuum chamber, the vacuum chamber is entirely housed in the waveguide. A discharge tube whose lower end is attached to the vacuum chamber in a state of being communicated with the vacuum chamber and which is entirely made of quartz glass and which is arranged around the outer periphery of the waveguide in a state of including the discharge tube inside and the upper part of the discharge tube. The magnetic field intensity in the region is higher than the magnetic flux density satisfying the electron cyclotron resonance condition, and the magnetic field intensity in the lower region of the discharge tube is almost the same as the magnetic flux density satisfying the electron cyclotron resonance condition. A first magnetic coil for generating, in parallel arranged over the vertical direction on the outer periphery of the vacuum chamber,
Second and third magnetic coils for respectively generating magnetic fields so as to form a magnetic field region of substantially uniform magnetic field strength in the vacuum chamber together with the magnetic field by the first magnetic coil, and inside the discharge tube from outside the vacuum chamber. The non-film forming gas inlet for introducing the non-film forming gas, the film forming gas inlet for allowing the film forming gas to be introduced into the vacuum chamber from the outside of the vacuum chamber, and the uniform A predetermined number of substrate holders for holding two or more sample substrates at regular intervals in a magnetic field region of uniform magnetic field strength with the direction of magnetic force lines in the magnetic field region being substantially parallel to the sample substrate surface. A predetermined number of counter electrodes arranged at intermediate positions between the substrate holders, the counter electrodes,
RF for applying a negative bias between the substrate holders
This is achieved by providing at least a power source.

Example of Invention

An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a principle block diagram showing an embodiment of an ECR microwave plasma processing apparatus according to the present invention. In FIG. 1, reference numeral 21 is, for example, a quartz glass discharge tube having an inner diameter of 100 mmφ, 2
2 is a sample chamber (vacuum chamber), 23 is a magnetron for generating a microwave of 2.45 GHz, and 24 is a circular waveguide.
In this example, the microwave is introduced in the Heusler mode without using the discharge chamber (plasma generation chamber) of the cavity resonator structure shown in FIG. 4, but the present invention is not limited to this. 25 is a magnetic coil for forming a magnetic field satisfying the electron cyclotron resonance condition, and the magnetic field strength by this is preferably larger than the magnetic flux density of the electron cyclotron resonance condition at the tip of the discharge tube 21 along the propagation path of the microwave. , Discharge tube 21
The magnetic flux density that satisfies the electron cyclotron resonance condition is set to be, for example, 875 G at the exit portion of. Reference numeral 26 is a first gas inlet having an annular blow-out portion from which gas is blown to the discharge tube 21 side, and the raw material gas (non-film forming gas) introduced is generated by plasma discharge by microwaves in the discharge tube 21. Decomposition is activated. Reference numeral 27 is a second gas inlet having an annular outlet from which gas is blown to the sample chamber 22 side, and another type of raw material gas (film forming gas) introduced during film formation processing is decomposed from the discharge tube 21. Reacts with the gas inside the sample chamber 22. 28 and 29 are the magnetic field generated by the magnetic coil 25 and the sample chamber 22
Magnetic coils arranged in parallel to form a region having a substantially uniform magnetic field strength therein. In this example, a magnetic field having the same polarity as that of the magnetic coil 25 is formed by the magnetic coil 29, and by the magnetic coil 28. By forming a magnetic field of opposite polarity, a region having a substantially uniform magnetic field strength, for example, a magnetic flux density of about 150 G is formed in the region inside the sample chamber 22 near the magnetic coil 29. An exhaust port 30 is connected to an exhaust system including an oil diffusion pump and an oil rotary pump. Reference numeral 31 denotes a plurality of sample substrates, 32 denotes a substrate holder, and the sample substrate 31 is installed in the sample chamber 22 in a region where the magnetic field strength is substantially uniform and substantially parallel to the magnetic force line direction. 33 is the distance between the electrode and the substrate holder (electrode) 32,
For example, a counter electrode arranged as 30 mm, 34 is an RF power source (oscillator), 35 is an impedance matching circuit, and a negative bias is applied between the substrate holder 32 and the counter electrode 33 from the RF power source 34 via the impedance matching circuit 35. As a result, an electric field perpendicular to the surface of the sample substrate 31 can be formed.

Using the device of this configuration, for example, the first
While introducing oxygen from the gas inlet 26 of the sample chamber 22
Silane is introduced from the second gas introduction port 27 to the side to form silicon dioxide on a 3-inch square silicon wafer (sample substrate) 31 at a film formation pressure of about 1 × 10 ⁻³ Torr. When, for example, an RF wave (radio wave) of 13.5 MHz is applied to the substrate holder 32, a film of silicon dioxide having a refractive index of 1.46 is obtained with a film thickness uniformity of ± 5%, and the sample substrate surface is used as a magnetic field line. The same film formation as in the case where they are arranged almost vertically is possible. This is considered to be due to the effect of replacing the conventional ion acceleration effect by the divergent magnetic field with the electric field, and the applied radio frequency power is 20 to 30 V.
It is sufficiently effective that a negative bias of 1 can be applied.
In this embodiment, a radio wave is applied to the sample holder 32 side so that a negative bias is easily applied to the sample substrate 31 side.However, when the film forming process is simply performed, the required bias is small, and thus the counter electrode 33 side is exposed to the radio wave. It is also possible to turn on and ground the sample holder 32 side. Also, the radio frequency is not limited to 13.5 MHz, and may be direct current in the case of a conductive sample. If the radio frequency power input to the sample holder 32 is further increased, it is possible to perform sputtering with oxygen ions on the surface of the sample substrate 31, but in this way, a negative bias of about 100 V, which was not possible with conventional devices. However, this device can be applied with good controllability. Such a wide range of controllability of negative bias is particularly effective when anisotropic etching is performed using this apparatus. For example, the second gas inlet 27 is closed and SF ₆ gas is supplied from the first gas inlet 26. Good anisotropic etching is possible by introducing and etching the silicon wafer (sample substrate 31).

FIG. 2 is a principle configuration diagram showing another embodiment in which the gas outlet of the second gas inlet 27 of FIG. 1 toward the sample chamber 22 is provided on the electrode surface of the counter electrode 33. In FIG. 2, reference numeral 36 is a counter electrode having a gas outlet on the electrode surface facing the surface of the sample substrate 31 on the sample holder 32, and other configurations are the same as those in FIG. As described above, in this apparatus, the surface of the sample substrate 31 can be disposed substantially parallel to the magnetic lines of force as described with reference to FIG. 1. Therefore, when plasma film formation is performed, the gas introduced to the sample chamber 22 side is microscopic. It is possible to dispose the gas outlet of the second gas inlet 27 so that it is difficult to diffuse toward the wave introducing portion. Using the device of this configuration, for example, a discharge tube
Argon gas is introduced as a source gas to the 21 side to excite plasma by microwaves, and silane gas is introduced from the surface of the counter electrode 36 as a source gas to the sample chamber 22 side and onto the glass substrate (sample substrate 31). An amorphous silicon film is formed. In this case, a quartz glass discharge tube
It is possible to form a film on the sample substrate 31 under the condition that the amount of the adhered film formed on the film 21 is extremely small. Therefore, the present invention can be applied to the film forming process of a conductive thin film, which is difficult with the conventional apparatus.

FIG. 3 is a principle block diagram showing another embodiment for forming a uniform magnetic field region in the sample chamber 22 of FIG. In FIG. 3, reference numeral 37 denotes a high-permeability plate which encloses the magnetic coil 25 and is extended to the sample chamber 22 side. Other configurations are the same as those in FIG. 1 except that the magnetic coil 28 in FIG. As described above, in the apparatus shown in FIG. 1, the uniform magnetic field in the sample chamber 22 is formed by the three sets of magnetic coils 25, 28, 29.
It is also possible to form it by a high-permeability plate 37 and a magnetic coil 29 which are wrapped around and are extended to the sample chamber 22 side.

〔The invention's effect〕

As described above, according to the ECR microwave plasma processing apparatus of the present invention, it is possible to simultaneously process a plurality of samples, which was difficult with the conventional apparatus, and the productivity is remarkably improved. This has the effect of facilitating the etching process in the control region and the film forming process of the highly conductive thin film.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a plasma processing apparatus according to the present invention, and FIG. 2 is a block diagram showing another embodiment of a counter electrode having a gas outlet of a second gas inlet of FIG. FIG. 3 is a block diagram showing another embodiment of a magnetic coil for forming a uniform magnetic field in the sample chamber of FIG. 1, and FIG. 4 is a block diagram illustrating a conventional plasma processing apparatus. 21 ... Discharge tube, 22 ... Sample chamber (vacuum chamber), 23 ... Magnetron, 24 ... Waveguide, 25 ... Magnetic coil, 26, 27 ...
Gas inlet, 28,29 ... Magnetic coil, 30 ... Exhaust port, 31
…… Sample substrate, 32 …… Substrate holder, 33 …… Counter electrode, 34
...... RF power supply, 35 …… Matching circuit, 36 …… Counter electrode with outlet, 37 …… High permeability plate

Claims (3)

[Claims] 1. A non-film forming gas introduced into the vacuum chamber is converted into plasma by a magnetic field formed in the vacuum chamber and a microwave introduced into the vacuum chamber, and the non-film forming gas is converted into plasma. By subjecting the film-forming gas to the sample substrate placed in the magnetic field directly or indirectly in the presence of the film-forming gas, the sample substrate is subjected to etching treatment or film-forming treatment. In the plasma processing apparatus, the inside of which is evacuated by a vacuum chamber and a magnetron which generates microwaves.
A waveguide for propagating microwaves from the magnetron and a microwave introduction window for introducing the microwaves from the waveguide into the vacuum chamber, the vacuum even when a conductive film is attached to the inner wall surface. In order to allow microwaves to propagate to the chamber, the lower end is attached to the vacuum chamber so as to be in communication with the vacuum chamber so that the waveguide is entirely accommodated, and the whole is made of quartz glass. A discharge tube and a state in which the discharge tube is included inside are disposed around the outer periphery of the waveguide, and the magnetic field strength in the upper region of the discharge tube is higher than the magnetic flux density satisfying the electron cyclotron resonance condition. The first magnetic field is generated so that the magnetic field strength in the lower region of the discharge tube is almost the same as the magnetic flux density satisfying the electron cyclotron resonance condition.
Magnetic coil and the magnetic coil are arranged in parallel in the vertical direction around the outer circumference of the vacuum chamber, and together with the magnetic field by the first magnetic coil, a magnetic field is formed in the vacuum chamber so as to form a magnetic field region of substantially uniform magnetic field strength. Second and third magnetic coils for generating the non-film forming gas, a non-film forming gas inlet for introducing the non-film forming gas into the discharge tube from the outside of the vacuum chamber, and the vacuum chamber from the outside of the vacuum chamber In the film-forming gas inlet for allowing the film-forming gas to be introduced therein, and in the magnetic field region of the uniform magnetic field strength, the direction of magnetic force lines in the magnetic field region and the sample substrate surface were made substantially parallel. As a state, a predetermined number of substrate holders for holding two or more sample substrates at regular intervals, a predetermined number of counter electrodes arranged at intermediate positions between the substrate holders, the counter electrodes, the substrate To apply a negative bias between each holder An RF power source, a plasma processing apparatus but formed by at least provided. 2. The polarities of the magnetic fields by the first and third magnetic coils are the same, and the polarities of the magnetic fields by the second magnetic coil arranged between the first and third magnetic coils are the first and third. The plasma processing apparatus according to claim 1, wherein the magnetic fields are formed by the first, second, and third magnetic coils, respectively, which are opposite to the polarities of the magnetic fields by the magnetic coils. 3. The plasma processing apparatus according to claim 1 or 2, wherein the film-forming gas from the film-forming gas inlet is blown out from each of the counter electrodes.