JPH07105384B2 - Plasma reactor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a plasma reactor in which plasma is generated by gas discharge and the generated plasma is used to perform processing such as etching and thin film formation on the surface of a semiconductor substrate. In particular, the present invention relates to a plasma reactor capable of uniformly generating high-density plasma.

[Conventional technology]

When manufacturing a semiconductor device such as an IC, processes such as etching and thin film formation are performed on a semiconductor substrate (wafer). As one of such semiconductor substrate processing apparatuses, there is a plasma reaction apparatus using plasma generated by gas discharge.

FIG. 3 is a schematic vertical cross-sectional view of a general plasma reaction apparatus using plasma generated by electron cyclotron resonance discharge. In FIG. 3, this plasma reactor is provided with a reaction chamber 1, a cylindrical plasma generation chamber 2 provided at an upper portion of the reaction chamber 1 and having a lower end opened to an upper portion of the reaction chamber 1, and a plasma generation at one end. A waveguide 3 which is connected to an opening on the upper surface of the chamber 2 and has the other end connected to a microwave generating means (not shown), and which guides the microwave generated by the microwave generating means to the plasma generating chamber 2. , A quartz plate 4 attached to an opening formed on the upper surface of the plasma generation chamber 2
And a plurality of minimum magnetic field forming coils 5 provided around the plasma generation chamber 2 and provided on the outer periphery thereof.
A gas inlet 6 is provided above the plasma generation chamber 2, and an exhaust port 7 is provided at the side of the reaction chamber 1.
A holding table 8 is provided in the lower part of the reaction chamber 1 so as to face the lower end of the opening of the plasma generation chamber 2, and a semiconductor substrate 9 is placed on the holding table 8.

The conventional plasma reactor is configured as described above, and after the gas remaining in the reaction chamber 1 is sufficiently exhausted through the exhaust port 7, the reaction is performed from the gas introduction port 6 into the plasma generation chamber 2 and the reaction chamber 1. Part of the gas is exhausted from the exhaust port 7 while introducing the volatile gas, and the gas pressure in both chambers is maintained at a predetermined value. Further, a microwave having a frequency of 2.45 GHz generated by the microwave generation means is introduced into the plasma generation chamber 2 via the waveguide 3 and the quartz plate 4. On the other hand, a power source (not shown) is supplied to the minimal magnetic field forming coil 5 provided around the plasma generation chamber 2.
Then, a non-uniform magnetic field diverging from the plasma generation chamber 2 toward the reaction chamber 1 is formed in the plasma generation chamber 2 and the reaction chamber 1 by energizing from the above.

As a result, the electrons of the reactive gas in the plasma generation chamber 2 are
Electron cyclotron resonance absorbs the electromagnetic energy of microwaves to accelerate them, and they spirally descend in the plasma generation chamber 2 while making a circular motion. In this way, due to the collision of electrons that move circularly at high speed, high-density gas plasma is generated in the plasma generation chamber 2. This gas plasma is transferred from the plasma generation chamber 2 into the reaction chamber 1 along the lines of magnetic force formed by the minimal magnetic field forming coil 5, and is subjected to processing such as etching or thin film formation on the surface of the semiconductor substrate 9 on the holding table 8. Give. The type of gas, pressure, microwave power, etc. used at this time are selected according to the type of substrate processing step.

[Problems to be Solved by the Invention]

In the conventional plasma reaction device provided with the coil for forming a minimum magnetic field, the Yohue magnetic field coil, the baseball coil, the in-Yan coil, etc. formed a minimum magnetic field, so that the plasma was compressed by the magnetic field at both ends of the coil,
The plasma has an elliptical cross-section, which makes it difficult to improve the uniformity when processing a semiconductor substrate. Moreover, if the number of poles of the coil is increased to improve the uniformity, the magnetic field strength cannot be increased sufficiently,
It requires larger coils and higher excitation power output,
There was a problem in practice.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to obtain a plasma reactor which maintains a high density plasma by utilizing a minimum magnetic field and is excellent in uniformity.

[Means for Solving the Problems]

The plasma reactor according to the present invention is provided with a permanent magnet that forms a multi-pole cusp magnetic field, and a plurality of coil means that are provided so as to sandwich the permanent magnet and that forms a mirror magnetic field.

[Action]

In the present invention, since the minimum magnetic field is formed in the plasma generation chamber by the permanent magnet and the coil means and the magnetic field in the central portion of the plasma generation chamber is weaker than that in the outer peripheral portion, the plasma in the plasma generation chamber is stable. Be trapped. Therefore, a stable and dense plasma is generated in the plasma generation chamber, and the processing speed of the semiconductor substrate is improved.
Also, the conditions for plasma generation such as gas pressure are alleviated.
Furthermore, due to the multi-pole cusp magnetic field by the permanent magnet, the effective plasma generation area becomes the outer peripheral part of the plasma generation chamber,
In addition, the axial symmetry improves the uniformity of semiconductor substrate processing.

〔Example〕

An embodiment of the present invention will be described below with reference to the accompanying drawings. However, the structure and operation of the following embodiments are the same as those of the plasma reactor shown in FIG. 3 except for a part thereof, and therefore only the differences will be described in detail below and the other points will be described in detail. Is omitted.

FIG. 1 is a schematic sectional view showing an embodiment of the present invention.
In this embodiment, instead of the minimum magnetic field forming coil 5 shown in FIG. 3, a permanent magnet 10 and a mirror magnetic field, which are provided around the plasma generating chamber 2 and form a multipolar cusp magnetic field, are formed inside the plasma generating chamber 2. The plasma reactor has the same configuration as that of the plasma reactor shown in FIG. 3 except that the coil means, for example, the solenoid 12 is provided.

In this embodiment, the exhaust port 7 is provided at the bottom of the reaction chamber 1, and the iron core 11 constitutes a magnetic circuit for holding and connecting the permanent magnets 10 to each other.

FIG. 2 is a cross-sectional view taken along the line I-I in FIG. For example, the multi-pole cusp magnetic field generated by four pairs of permanent magnets 10 and the mirror magnetic field generated by, for example, two solenoid coils 12 are combined to form a minimum magnetic field. The plasma is generated in a region along the magnetic field lines shown in FIG. 2, and diffuses toward the central portion of the plasma generation chamber 2 where the magnetic field is minimum. Therefore, the inside of the plasma generation chamber 2 is filled with plasma having a uniform density. The generated plasma is transferred into the reaction chamber 1 with the same axially symmetrical cross-sectional shape as in the plasma generation chamber 2, and processes the surface of the semiconductor substrate 9 placed on the holding table 8.

Table 1 shows the uniformity when etching the Si substrate using the plasma reactor of the present embodiment, in comparison with the conventional side. The uniformity was markedly improved in this example as compared with the conventional example in which the uniformity was poor because the plasma was strongly compressed.

Specific examples of the specifications of this embodiment are as follows.

Plasma generation chamber diameter 200 mm Plasma generation chamber axial length 180 mm Mirror magnetic field spacing 220 mm Permanent magnet surface magnetic flux density 1500 Gauss Also, since the magnetic field in the plasma reactor of this example is a minimum magnetic field, plasma can be stably confined. The plasma generation density is improved, and the reaction rate in semiconductor substrate processing can be increased.

In the above description, only the embodiment in which the plasma is generated by using the electron cyclotron resonance discharge is described, but the present invention is the high frequency discharge, the magnetron discharge, the PIG.
It can also be applied to plasma reactors that utilize electric discharge.

〔The invention's effect〕

As described above, according to the present invention, a permanent magnet that forms a multipole cusp magnetic field, and a plurality of coil means that are provided so as to sandwich the permanent magnet and that forms a mirror magnetic field are provided. Since it is formed by synthesizing the mirror magnetic field, stable high density plasma can be generated with good uniformity, and further, the processing uniformity of the semiconductor substrate can be improved and the processing speed can be increased.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an embodiment of the present invention, FIG. 2 is a horizontal sectional view taken along line I--I of FIG. 1, and FIG. 3 is a sectional view showing a conventional plasma reactor. In the figure, 1 is a reaction chamber, 2 is a plasma generation chamber, 9 is a semiconductor substrate, 10 is a permanent magnet, and 12 is a solenoid coil. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A plasma reactor in which plasma is generated in a plasma generation chamber by gas discharge, and processing such as etching or thin film formation on a surface of a semiconductor substrate in the reaction chamber is performed around the plasma generation chamber. A permanent magnet for forming a multipole cusp magnetic field therein, and a plurality of coil means for sandwiching the permanent magnet to form a mirror magnetic field, wherein the multipole cusp magnetic field and the mirror magnetic field are superposed. A plasma reactor characterized by being formed into a minimal magnetic field.