JPH0572097B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a microwave plasma processing apparatus, and in particular to a microwave plasma processing apparatus suitable for generating plasma by applying the electric field of a microwave and the magnetic field of a magnet. It relates to a processing device.

[Background of the invention]

In recent years, etching of substrates, which are samples, has become increasingly dry due to the increased need for microfabrication. This dry process includes reactive ion etching, plasma etching, etc., but with the shift to ultra-LSI, it is possible to perform finer processing, and there are fewer undercuts.
There is a need for a next-generation etching process that satisfies the requirements of low ion damage and high uniformity.

A microwave plasma etching device that can satisfy this requirement uses an electric field generated by microwaves and a magnetic field generated by a solenoid coil to cause cyclotron movement of electrons, and is capable of high-density plasma discharge even at a gas pressure as low as 10 ^-2 Pa. There is an etching process used. That is, the microwaves generated by the microwave generator propagate to the waveguide via a microwave propagation means such as a waveguide or coaxial cable.
A discharge is generated by the interaction with the magnetic field generated by the solenoid coil that is installed on the outer periphery of the waveguide and surrounds the discharge tube. It is absorbed into the process gas inside the tube and the process gas is turned into plasma. The substrate placed on the susceptor is etched using ions or chemically active neutral particles (hereinafter abbreviated as active particles) in the plasma. In order to further increase the density of the plasma generated in the discharge tube, for example, three solenoid coils installed around the outer periphery of the waveguide and one permanent magnet installed in the susceptor section where the substrate is placed are used to generate a mirror magnetic field. generates and confines the plasma within a certain range. Also, a thin film is formed using plasma.
Such technology is also being used in CVD technology.

However, in the above-mentioned conventional technology, since it is possible to discharge under a gas pressure as low as 10 ^-2 Pa, it is possible to uniformly disperse the process gas, or in other words, perform uniform etching processing or thin film formation (hereinafter abbreviated as "processing"). Although the conditions are met, the magnetic field used to confine the plasma is not uniform in the radial and axial directions of the discharge tube due to the shape characteristics of the solenoid coil. Therefore, the plasma density confined within the discharge tube by the magnetic field is non-uniform in the radial and axial directions of the discharge tube, and naturally non-uniform on the processing surface of the substrate, so it is difficult to process the substrate uniformly. The problem was that I couldn't do it. Note that the maximum point of this plasma density is distributed on concentric circles, and the radius of the concentric circle varies depending on the plasma generation conditions, such as gas pressure, microwave power, magnetic field strength, etc., but for example, the maximum point is at the center of the axis. In some cases, the distribution is maximum at the periphery, and the distribution is not uniform.

Note that a microwave plasma processing apparatus as described in Japanese Unexamined Patent Application Publication No. 168230/1983 is related to this type of apparatus. When processing a sample using plasma excited by microwaves, this device separates the reaction chamber for processing the sample from the plasma generation chamber using a shielding plate with multiple holes, and shields the sample from the plasma generation chamber. The sample could be processed uniformly by rotating and/or moving up and down relative to the plate.

However, in this device, the plasma generation chamber is divided by a shielding plate so that the sample and plasma are not directly related, and this device is different from the above-mentioned conventional device in which a mirror magnetic field is formed above the substrate. was not taken into account.

[Purpose of the invention]

An object of the present invention is to provide a microwave plasma processing apparatus that can uniformly process a substrate.

[Summary of the invention]

In the present invention, an orthogonal electromagnetic field is formed by a microwave generating means and a first magnetic field generating means, and a plasma is generated in a vacuum container. When confining plasma in a vacuum container and performing plasma processing using magnetic field generating means, the direction of the axis of the vacuum container is
By reciprocating the sample stage equipped with a second magnetic field generation means, the impedance of the plasma confined within the vacuum vessel is changed, and the radial distance where the maximum plasma density is distributed within the vacuum vessel is changed. This allows the substrate to be processed uniformly.

[Embodiments of the invention]

In a microwave plasma processing apparatus, it is important to make the plasma density uniform throughout the discharge tube, at least in the radial direction of the discharge tube, by using a solenoid coil, which is the first magnetic field generating means for generating a mirror magnetic field, and a solenoid coil, which is the first magnetic field generating means for generating a mirror magnetic field. This is extremely difficult due to the configuration with permanent magnets, which are the magnetic field generating means in step 2.

Therefore, the present invention reciprocates a sample stage equipped with a permanent magnet in the direction of the central axis of the magnetic field generated by the solenoid coil, that is, in the direction of the axis of the vacuum vessel, while maintaining the non-uniform plasma density. ing. If this is done, the volume of the plasma confined within the discharge tube, that is, confined by the mirror magnetic field, changes, or in other words, the impedance of the plasma changes, causing mismatching of the microwave circuit. As a result, the maximum point of plasma density moves in the radial direction of the discharge tube, and although the plasma density is non-uniform, it changes periodically with a certain range of variation, so that the processing is averaged.

An embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

Figure 1 shows a microwave plasma processing apparatus,
In this case, a discharge tube 30 made of an electrically insulating material is connected to the vacuum vessel 21 connected to the vacuum exhaust device 10 and provided with a nozzle 20 for introducing a process gas, and a discharge tube 30 formed of an electrically insulating material is connected to the vacuum vessel 21 in an airtight manner. It is configured. A waveguide 40 including the discharge tube 30 is concentrically disposed outside the discharge tube 30, and a solenoid coil 50 is concentrically arranged in the waveguide 40.
For example, three pieces, in this case, three stages separated in the height direction are arranged in a ring. The waveguide 40 is connected to a microwave generator 70 by a microwave propagation means 60 such as a waveguide or a coaxial cable. In this case, a reciprocating device 80 is installed at a lower position of the vacuum container 21, and a reciprocating shaft 81 of the reciprocating device 80
The vacuum vessel 21 and the discharge tube 3 are connected to each other so as to maintain airtightness and to be able to reciprocate in the direction of the arrow in parallel with the axis of the discharge tube 30.
0 and is provided in a protruding manner in a space 90 formed by. At the upper end of the reciprocating shaft 81 is a susceptor 10 which is a sample stage.
A permanent magnet 51 is provided below the susceptor 100. In addition, nozzle 20
A process gas supply device 130 is connected to the gas conduit 120 .

In the device configured as described above, the plasma density distribution confined within the discharge tube 30 by the magnetic field formed by the solenoid coil 50 and the permanent magnet 51 is in the central axis direction of the magnetic field formed by the solenoid coil 50, That is, depending on the position of the susceptor 100 and the permanent magnet 51 with respect to the axial direction of the discharge tube, that is, at the upper position shown in FIG. 1, the plasma density becomes maximum at the center of the discharge tube 30 shown in FIG. The plasma density A becomes smaller as the radial distance R increases, and the plasma density A reaches its maximum at a certain radial distance R of the discharge tube 30 shown in FIG. 2b at the lower position shown in FIG. Varies between.

Figure 3 shows the radial distance L ₁ from the axial center of the discharge tube 30 to the position where the plasma density is maximum when the microwave power is approximately 200W and the maximum magnetic field is approximately 1300 Gauss directly above the discharge tube 30. , the moving distance of the susceptor 100 and the permanent magnet 51 from the top to the bottom shown in FIG. 1 in the axial direction of the discharge tube.
This shows the relationship with L ₂ , in this case, L ₂ = 20
At mm, L ₁ begins to increase and saturates to L ₁ = 100 mm at L ₂ = 80 mm. Therefore, the size of the substrate 110 placed on the susceptor 100 is, for example, the diameter
If it is 150 mm, in this case, L ₂ ≒ 60 mm can correspond to the outer peripheral side processing surface of the substrate 110. Therefore, by setting the reciprocating stroke length of the susceptor 100 and the permanent magnet 51 to 60 mm, the substrate 110
The plasma densities corresponding to the treated surface are averaged.
Note that other operations are the same as those of the prior art, so explanations will be omitted.

As described above, according to this embodiment, plasma is generated by the action of the microwave electric field and the magnetic field of the solenoid coil, and the inside of the discharge tube is generated by the magnetic field formed by the solenoid coil and the permanent magnet provided in the susceptor. In other words, when plasma is confined within a vacuum vessel and a substrate is subjected to plasma processing, a susceptor equipped with a permanent magnet is reciprocated in the axial direction of the vacuum vessel, thereby reducing the amount of plasma confined within the vacuum vessel. By changing the impedance, the distance in the radial direction where the maximum plasma density is distributed within the vacuum chamber can be changed, so that the substrate can be processed uniformly.

〔Effect of the invention〕

According to the present invention, plasma is generated by the electric field of the microwave generating means and the magnetic field of the first magnetic field generating means, and the plasma is generated between the first magnetic field generating means and the second magnetic field generating means provided on the sample stage. Therefore, in a plasma processing device that confines plasma in a vacuum container,
By reciprocating the sample stage provided with the second magnetic field generating means in the axial direction of the vacuum container, the sample is confined in the vacuum container by the first magnetic field generating means and the second magnetic field generating means. By changing the impedance of the generated plasma, the distance in the radial direction where the maximum plasma density is distributed within the vacuum container can be changed, which has the effect of uniformly processing the substrate.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing an example of a microwave plasma processing apparatus embodying the present invention, FIG.
b is a relationship diagram between the radial distance of the discharge tube and the plasma density, and Figure 3 is the reciprocating stroke length of the substrate and the position from the center of the discharge tube to the position where the plasma density is maximum, which the inventors obtained in experiments. It is a relationship diagram with the distance. 10...Evacuation device, 30...Discharge tube, 40
...Waveguide, 50...Solenoid coil, 60...
...Microwave propagation means, 70...Microwave generator, 80...Reciprocating device, 81...Reciprocating shaft,
100...Susceptor, 110...Substrate, 130...
...Process gas supply equipment.

Claims (1)

[Scope of Claims] 1. A vacuum container to which a processing gas is supplied and evacuated, a microwave generating means for forming an orthogonal electromagnetic field for converting the processing gas into plasma within the vacuum container, and a first comprising a magnetic field generating means, a sample stand with a sample placement surface arranged in a direction perpendicular to the magnetic field, and a second magnetic field generation means provided on the sample stand on a side opposite to the sample placement surface, 1. In a microwave plasma processing apparatus in which the plasma is confined within the vacuum vessel by a magnetic field generated by a second magnetic field generating means, the plasma density distribution confined within the vacuum vessel is such that the plasma density distribution is in the axial direction of the vacuum vessel. At one position, the distribution is maximum at the axial center of the vacuum vessel, and becomes smaller as the radial distance increases, and at the other position in the axial direction of the vacuum vessel, which is different from the one position, the axial center of the vacuum vessel is The micro-micrometer is characterized by comprising a driving means for reciprocating the sample stage and the second magnetic field generating means in the axial direction of the vacuum container so that the distribution becomes maximum at a predetermined position in the radial direction excluding Wave plasma treatment equipment.