JPH02130923A - Plasma reaction equipment - Google Patents

Abstract

PURPOSE:To maintain high density plasma, and improve uniformity by a method wherein minimum magnetic field is formed by superposing multipole cusped magnetic field and mirror magnetic field. CONSTITUTION:Permanent magnets 10 to form multipole cusp magnetic field, and solenoids 12 to form mirror magnetic field are installed on the peripheral part of a plasma generating chamber. An exhaust vent 7 is installed at the bottom part of the reaction chamber 1. An iron core 11 constitutes a magnetic circuit retaining and connecting each of the permanent magnets 10. Multipole cusp magnetic field by four pairs of the permanent magnets 10 and mirror magnetic field by two solenoids 12 are synthesized to form minimum magnetic field. Plasma is generated in a region along magnetic line of force, and diffuses toward the central part of the plasma generating chamber 2 where the magnetic force becomes minimum. Thereby, the inside of the chamber 2 is filled with plasma of uniform density.

Description

[Detailed Description of the Invention] [Field of Application] This invention relates to a plasma reaction in which plasma is generated by gas discharge and the generated plasma is used to perform processing such as etching or forming a thin film on the surface of a semiconductor substrate. The present invention relates to an apparatus, particularly a plasma reactor capable of generating high-density plasma with good uniformity.

[Conventional technology]

When manufacturing a semiconductor device such as an IC, a semiconductor substrate (wafer) is subjected to processes such as etching and thin film formation. One such semiconductor substrate processing apparatus is a plasma reaction apparatus that utilizes plasma generated by gas discharge.

FIG. 3 is a schematic longitudinal sectional view of a typical plasma reactor that utilizes plasma generated by electron cyclotron resonance discharge. ! In FIG. 3, this plasma reactor includes a reaction chamber 1, a cylindrical plasma generation chamber 2 provided at the upper part of the reaction chamber 1 and whose lower end is open to the upper part of the reaction chamber 1, and a plasma generation chamber 2 at one end. The other end is connected to the opening on the top surface of 2 and the other end is a microwave generating means (not shown) K.
and a waveguide 3 that is connected to the waveguide 3 and guides the microwave generated by the microwave generation means to the plasma generation chamber 2.

It comprises a quartz plate 4 adhered to an opening formed on the upper surface of the plasma generation chamber 2, and a plurality of minimal magnetic field forming coils 5 surrounding the plasma generation chamber 2 and provided on its outer periphery. There is. Note that a gas inlet 6 is provided at the top of the plasma generator II2, and an exhaust lower is provided at the side of the reaction chamber l. Further, in the lower part of the reaction chamber 1, a holding table 8 is provided opposite to the lower end of the opening of the plasma generation chamber 2, and a semiconductor substrate 9 is placed on this holding table 8.

Conventional plasma reactor as mentioned above! After fully exhausting the gas remaining inside the reaction chamber l from the exhaust lower, a part of the gas is exhausted while introducing the reactive gas into the plasma generation chamber 2 and the reaction chamber l from the gas inlet 6. Exhaust air from the lower part and maintain the gas pressure in both chambers at a specified value. Moreover, the frequency generated by the microwave generating means is 2.45G.
Hz microwaves are introduced into the plasma generation chamber 2 via a waveguide 3 and a quartz plate 4. On the other hand, the coil 5 for forming a minimal magnetic field provided around the plasma generation chamber 2 is energized from a power source (not shown), and from this coil 5aK for forming a minimal magnetic field, inside the plasma generation chamber 2 and the reaction chamber 1, A non-uniform magnetic field is formed that emanates from the plasma generation chamber 2 toward the reaction chamber IK.

As a result, the electrons of the reactive gas in the plasma generation chamber 2 are
It is accelerated by absorbing the electromagnetic energy of the microwave by electron cyclotron resonance, and descends spirally while moving circularly within the plasma generation chamber 2.

High-density gas plasma is generated in the plasma generation chamber 2 due to the collision of electrons moving in a circular motion at high speed. 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 used to perform processes such as etching and thin film formation on the surface of the semiconductor substrate 9 on the holding table B. give Note that the type of gas, pressure, microwave power, etc. used at this time are selected depending on the type of substrate processing process.

[Problem to be solved by the invention]

In conventional plasma reactors equipped with coils for forming a minimal magnetic field, the minimal magnetic field was created using a Yotsufue magnetic field coil, a baseball coil, a Yin-Yang coil, etc., so the plasma was compressed by the magnetic field at both ends of the coil.
There has been a problem in that the cross-sectional shape of the plasma is elliptical, making it difficult to improve uniformity when processing semiconductor substrates. Additionally, if the coil is multipolarized to improve uniformity, the magnetic field strength cannot be made strong enough.
Requires larger coils and higher output power for excitation,
There was a practical problem.

This invention was made to solve the above-mentioned problems, and aims to maintain high-density plasma by utilizing a minimal magnetic field and to obtain a plasma reactor with excellent uniformity.

[Means to solve the problem]

The plasma reaction apparatus according to the present invention is provided with a permanent magnet that forms a multipolar cusp magnetic field and a coil means that forms a mirror magnetic field.

[For production]

In this invention, a minimal magnetic field is formed within the plasma generation chamber by the permanent magnet and coil means, and the magnetic field at the center of the plasma generation chamber is weaker than at the outer periphery, so the plasma within the plasma generation chamber is stabilized. be trapped. Therefore, stable plasma with high density is generated in the plasma generation chamber, and the processing speed of semiconductor substrates is improved.

Additionally, conditions for plasma generation such as gas pressure are relaxed.

Moreover, due to the multipolar cusp magnetic field generated by the permanent magnet, the effective plasma generation area becomes the outer periphery of the plasma generation chamber,
Moreover, since it is axially symmetrical, the uniformity of semiconductor substrate processing is improved.

``Practice flI'' Hereinafter, one embodiment of the present invention will be described based on the attached drawings.However, the structure and operation of the following embodiment are the same as the plasma reactor shown in FIG. 3 except for some parts. In the following, only the points that are particularly different will be explained in detail, and detailed explanations of other points will be omitted.

FIG. 1 is a schematic vertical sectional view showing an embodiment of the present invention. This embodiment is provided around the plasma generation chamber 2 instead of the minimum magnetic field forming coil 50 shown in FIG. Means e.g. Renoid 12
The plasma reactor has the same structure as the plasma reactor shown in FIG. 3, except that it is equipped with a.

In this embodiment, the exhaust lower is provided at the bottom of the reaction chamber 1, and the iron core 11 serves as a magnetic circuit that holds and connects the permanent magnets 1O.

FIG. 2 is a cross-sectional view at IIM [-f in FIG. 1. , the multi-pole magnetic field generated by the four pairs of permanent magnets 10 and the mirror magnetic field generated by, for example, two solenoid coils 12 are combined to form a minimal magnetic field. Plasma is generated in a region along the magnetic lines of force shown in FIG. 2, and diffuses toward the center of the plus-one generation chamber 2 where the magnetic field is minimal. Therefore, the inside of the plasma generation chamber 2 is filled with plasma of uniform density. The generated plasma is transferred into the reaction chamber 1 while maintaining the same axially symmetrical cross-sectional shape as in the plasma generation chamber 2, and processes the surface of the semiconductor substrate 90 placed on the holding table 8.

Table 1 Etching characteristics of approximately 15c+a (6 inch) Si substrate Table 1 shows the uniformity when etching a Si substrate using the plasma reactor of this example in comparison with the conventional example. be. Compared to the conventional example in which the uniformity was poor due to strong compression of the plasma, the uniformity in this example was significantly improved.Specific examples of the specifications of this example are as follows.

Plasma generation chamber diameter 200ram Plasma generation chamber axial length 18orIL+! Mira-magnetic field spacing: 22011M Permanent magnet surface magnetic flux density: 1500 Gauss Also, since the magnetic field in the plasma reactor of this example is an extremely small magnetic field, plasma can be stably confined, plasma generation density is improved, and it is useful in semiconductor substrate processing. The reaction rate can be increased.

In addition, in the above explanation, only the embodiment in which plasma is generated using electron cyclotron resonance discharge has been explained, but this invention also applies to high frequency discharge, magnetron discharge, PI
It can also be applied to plasma reaction devices that use G discharge or the like.

〔Effect of the invention〕

As described above, the present invention provides a permanent magnet that forms a multipolar cusp magnetic field and a coil means that forms a mirror magnetic field, and forms an extremely small magnetic field by combining the multipolar cusp magnetic field and the mirror magnetic field. This has the effect that plasma can be generated with good uniformity, and as a result, the uniformity of processing semiconductor substrates can be improved and the processing speed can also be increased.

[BRIEF DESCRIPTION OF THE DRAWINGS] Fig. 1 is a longitudinal cross-sectional view showing an embodiment of the present invention, Fig. 2 is a cross-sectional view taken along the line [-1 in Fig. 1, and Fig. 3 is a cross-sectional view of a conventional plasma reactor. FIG. In the figure, l is a reaction chamber and 2 is a plasma generation chamber. 9 is a semiconductor substrate, IO is a permanent magnet, and 12 is a solenoid coil. In addition, in the figures, the same reference numerals indicate the same or equivalent parts. Daikonjinzo Gado Terusei Figure 1 and Figure 2

Claims (1)

[Claims] (1) In a plasma reactor that generates plasma in a plasma generation chamber by gas discharge and performs processing such as etching or thin film formation on the surface of a semiconductor substrate in the reaction chamber using the generated plasma, a , a plasma reaction comprising a permanent magnet forming a multipolar cusp magnetic field and a coil means forming a mirror magnetic field therein, wherein the multipolar cusp magnetic field and the mirror magnetic field are superimposed to form a minimal magnetic field. Device.