JPH0281434A - Plasma treatment apparatus - Google Patents

Abstract

PURPOSE:To form a high density plasma under a high gas pressure condition and improve a treatment speed by a method wherein an electromagnetic field intensified by a resonator is introduced through a microwave transmitting window into a plasma CVD treatment chamber to which a magnetic field with ECR conditions can be applied. CONSTITUTION:A magnetron 3 which is a microwave generator is attached to a cavity resonator 1 through a waveguide 2. A metal thin film 6 having a thickness about a surface current skin depth is formed on a microwave transmitting window 4. The microwave introduced by the cavity resonator 1 is reflected by the metal thin film 6 formed on the microwave transmitting window 4. Although a surface current is applied to the metal thin film 6, in accordance with the electromagnetic field of the microwave, the microwave is transmitted through the microwave transmitting window 4 and emitted into a treatment chamber 5. As a magnetic field with ECR conditions is applied to the treatment chamber 5, a high density plasma of CVD raw gas is formed by the cyclotron resonance of electrons.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to the manufacture of semiconductor devices, and relates to a plasma generation method suitable for plasma processing of semiconductor substrates such as plasma CVD, sputtering, and dry etching.

[Conventional technology]

Plasma CV in semiconductor device 07'2 Zuma processing
In method D, a source gas is introduced into a processing chamber in a vacuum atmosphere to form plasma, and chemically highly reactive ions and radicals (neutral active species) are generated through the ionization and dissociation process of the source gas. A thin film is formed as a reaction product on a semiconductor substrate. For example, silicon nitride film (SiNx
), SiH4+N is used as the raw material gas.
A mixed gas such as H31SiH4+N2 is used, and 5iH-? Generates ions and radicals such as NH. These ions and radicals form SiH+ xNH+(1+x)H-+SiNx+ on the semiconductor substrate.
A silicon nitride film (SiNx) is formed on a semiconductor substrate by a reaction such as (1+x)Hx.

In this way, in plasma processing equipment that utilizes the generation and reaction of ions and radicals, in order to improve the processing speed, it is necessary to increase the concentration of ions and radicals, and the ninth step is to form high-density plasma. There is a need. A plasma generation method using microwaves and μ waves has been proposed as one method for achieving this objective.

When plasma is generated using microwaves, even if the microwaves generated by a magnetron are introduced into a low-pressure processing chamber, the electric field strength of the microwaves is not sufficient, so sufficient energy is not supplied to the electrons in the plasma, and the plasma is difficult to generate. To keep this in mind, in order to obtain high-density plasma in the plasma generation method using microwaves, for example, as shown in Japanese Patent Application Laid-Open No. 60-415255, electron cyclotron resonance (electron cyclotron resonance) using a magnetic field in microwaves of 2.45 GHz is used. There is an E(:R) type plasma processing equipment.This type of plasma processing equipment uses NC to efficiently input microwave power into the plasma.
The plasma density is improved by applying an external magnetic field that satisfies the R condition to cause cyclotron resonance in the electrons in the plasma.

[Problem that the invention seeks to solve]

However, in the plasma processing apparatus of the above-mentioned prior art,
Under high pressure conditions, where the cyclotron motion of electrons is disturbed by collisions with gas molecules in the plasma, the efficiency of accelerating electrons by the microwave electric field decreases, resulting in a decrease in plasma density.

Conversely, even if the gas pressure is low, the plasma density decreases because the frequency of ionization and excitation of gas molecules due to collisions decreases. That is, the change in plasma density with respect to gas pressure in the conventional ECR microwave plasma processing apparatus has a relationship as shown in curve (b) of FIG. 2. Next, in the conventional ECR plasma processing apparatus,! 1
Under iCR conditions, high-density plasma can be obtained by efficiently injecting microwave power into the plasma at 10-2 Tor.
The gas pressure is on the order of r.

In order to speed up plasma CVD processing, it is essential to increase the supply amount of source gas, that is, the gas flow rate. However, in the conventional BCR type processing apparatus, the high-density plasma generation conditions are limited to a narrow gas pressure range of about 10 Torr, so when a large flow of gas is flowed, the gas pressure increases and the plasma density decreases. Furthermore, it is difficult to increase the size of the vacuum evacuation system to accommodate a large gas flow rate, and there is a problem in that it is difficult to increase the processing speed.

Further, in the above-mentioned conventional technology, since the structure generates plasma in a resonator, when plasma is generated, the wavelength of the microwave changes depending on the density of the plasma, so there is a problem that the resonance condition is no longer satisfied.

An object of the present invention is to provide a plasma CVD apparatus that can form high-density plasma even under conditions of high gas pressure and has a high processing speed.

[Means for solving problems]

The above purpose is to install a resonator between a microwave waveguide and a plasma processing chamber, to configure the resonator, and to contact the plasma processing chamber to seal the processing chamber under vacuum. If it is a thin metal film (for example, copper) that allows microwaves to pass through the window (dielectric material such as quartz or alumina),
This is achieved by forming an electromagnetic field of about 5 μm) and introducing an electromagnetic field strengthened by a resonator through the microwave transmission window into a plasma CVD processing chamber where a magnetic field under BCR conditions can be applied.

[Effect]

In the above-mentioned microwave processing device according to the present invention, the microwave introduced into the cavity resonator chamber from the waveguide is reflected by the microwave transmission window formed of a thin metal film, so that it becomes a certain resonance mode. The electromagnetic field of the microwave is strengthened by creating a standing wave in a cavity designed to create a standing wave. Furthermore, a surface current flows through the metal thin film formed on the microwave transmission window in response to the electromagnetic field of the microwave. Since the thickness of the metal thin film is as thin as the skin depth of the surface current, an electromagnetic field is also generated on the plasma processing chamber side opposite to the cavity resonator side across the metal thin film. Therefore, the microwave passes through the microwave transmission window and is introduced into the plasma processing chamber. A magnetic field under ECR conditions is formed in the plasma processing chamber.

According to the present invention, since the microwave electromagnetic field strength under the 1iICR condition is strong, the time required for electrons to obtain enough energy to excite or ionize gas molecules during cyclotron motion is shortened. Therefore, high-density plasma can be formed even at high gas pressures where the flight time until electron collision is shortened, and a plasma CVD apparatus with high processing speed can be obtained.

〔Example〕

Hereinafter, one embodiment of the present invention will be explained with reference to Figure i@1. FIG. 1 shows a cross section of a processing chamber showing the configuration of a plasma CVD apparatus according to the present invention. In FIG. 1, reference numeral 1 denotes a cavity resonator, to which a magnetron 3, which is a 145 GHz microwave generator, is attached via a waveguide 2. Further, the cavity resonator 1 is connected to a processing chamber 5 through a microwave transmission window 4 made of a dielectric material such as quartz or alumina, and the cavity resonator 1 at atmospheric pressure and the processing chamber 5 in a vacuum atmosphere are connected to each other. are separated. On the microwave transmission window 4, a metal thin film 6 of aluminum, silver, copper, etc. is formed by vapor deposition or plating to a thickness approximately equal to the depth of the surface current skin (for example, in the case of steel (about L5 μm), and cavity resonator 1
They are closely connected to each other in a structure that allows electrical continuity. Inside the processing chamber 5, a lower electrode 7 is installed so as to be electrically insulated from the processing chamber 5 at ground potential by an insulating cover 8, and is connected to a high frequency power source 9. A semiconductor substrate 10 to be subjected to plasma processing is placed on the lower electrode 7 . Coaxial coils 11 and 12 are installed outside the processing chamber 5, and can apply a magnetic field of 875 G inside the processing chamber 5.

Further, a gas supply device (not shown) is connected to the processing chamber 5, and the supplied gas is exhausted from the exhaust port 13 (by an exhaust device (not shown)). The pressure in the processing chamber 5 is controlled to a predetermined pressure during processing.

With the above configuration, the semiconductor substrate 10 is processed by plasma CVDK.
] The operation in the case of film formation processing will be explained. A CVD raw material gas (for example, SiH4+N2 in the case of a silicon nitride film) is supplied to the processing chamber 5 and controlled to a predetermined pressure. Next, a microwave of 2.45 GHz is generated by the magnetron S and introduced into the cavity resonator through the waveguide 2. The microwave introduced into the cavity resonator 1 is reflected by the metal thin film 6 formed on the microwave transmission window 4.

The tube length t of the cavity resonator 1 corresponds to a specific resonance mode (for example, Tl0
11 mode), and the cavity resonator 1
In this case, a standing wave of the microwave in the design mode is generated, and the electromagnetic field of the microwave is strengthened.

At this time, a surface current flows through the thin metal M6 in response to the electromagnetic field of the microwave, but since the thickness of the thin metal film 6 is as thin as the skin, the electric field due to the surface current also flows to the processing chamber 5 side. The generated microwaves are transmitted through the microwave transmission window 4 and radiated into the processing chamber.

At this time, the processing chamber 5 is provided with coaxial coils 11+12.
j5) Since a magnetic field under itcR conditions is applied, a high-density plasma of CVD raw material gas is formed due to cyclotron resonance of 11C atoms.

Here, in the case of this embodiment, compared to the conventional ΣCR method, the electromagnetic field strength of the microwave is stronger, so the electrons can obtain enough energy to excite or ionize the source gas in a short time, so the gas pressure is high. High-density plasma can be maintained even at low temperatures.

Furthermore, during the processing, the lower electrode 7 is supplied with I
AS4M)lz high frequency power is applied, and by controlling the energy of ions incident on the semiconductor substrate 10 by controlling the applied power, control is performed such as suppressing damage caused by ion bombardment and obtaining dense film quality. Can be done.

Figure 2 shows the change in plasma density with respect to gas pressure (curve -) in this example compared to the conventional ECR method (curve (b)).
).

According to this embodiment, as shown in Fig. 2, a high-density plasma can be maintained even in a high gas pressure region where the cyclotron motion of electrons is disturbed by collisions, and the energy of ions can be controlled arbitrarily. , high speed and high quality CVD
membrane can be obtained.

It is clear that the present invention is applicable not only to film formation processing by plasma CVD, but also to processing using plasma such as plasma oxidation and dry etching of semiconductor substrates.

〔Effect of the invention〕

According to the present invention, high-density plasma can be generated even in a high gas pressure region where the density of plasma formed by the ECR method is reduced, so that plasma processing with high processing speed can be realized.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a processing chamber of a plasma processing apparatus according to an embodiment of the present invention, and FIG. 2 is a comparison diagram of the relationship between plasma density and gas pressure changes in the plasma processing apparatus of the present invention and a conventional ECR method. be. 1... Cavity resonator, 2... Waveguide, 5
... Magnetron, 4 ... Microwave transmission window, 5 ... Processing chamber, 6 ... Metal thin film, 7 ... Lower electrode, 8...Insulating cover, 9...High frequency power supply, 10...Semiconductor substrate, 11.12...Coaxial coil, 13...
····exhaust port.

Claims (1)

[Claims] 1. In a plasma processing apparatus comprising a microwave plasma generation means, a processing gas supply means, and an exhaust means, the plasma generation means vacuum-isolates a cavity resonator and a plasma processing chamber, and a cavity resonator and a plasma processing chamber. 1. A plasma processing apparatus comprising a microwave transmitting window, and a metal thin film is formed on the microwave transmitting window.