JPH0456774A - Plasma reactor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a plasma reaction device that generates plasma by gas discharge and uses the generated plasma to perform processing such as etching or forming a thin film on the surface of a semiconductor substrate. Regarding.

[Conventional technology]

In the manufacture of semiconductor devices such as ICs, semiconductor substrates (
Processes such as thin film formation and etching are performed on wafers, and one type of semiconductor substrate processing apparatus is a plasma reaction apparatus that utilizes plasma generated by gas discharge.

FIG. 5 is a sectional view schematically showing a conventional plasma reaction apparatus used for RIE (reactive ion etching), etc., and will be described below.

As shown in FIG. 5, for example, a cathode electrode 3, which is one flat plate electrode, is fixed to the bottom surface of a hollow cylindrical reaction container 1 via an insulator 2, and a cathode electrode 3, which is one of the flat electrodes, is fixed to the bottom surface of the reaction container 1, which has a hollow cylindrical shape, for example.
An anode electrode 4, which is the other grounded flat plate electrode, is fixed, a picture electrode 3.4 is provided facing inside the reaction vessel 1, and a wafer 5 is mounted and held on the cathode electrode 3.

At this time, a plurality of gas outlets 6a and gas channels 6b are formed in the anode electrode 4, and the gas channels communicate with a gas introduction lower formed on the top surface of the reaction vessel 1. 6b and each gas outlet 6a, the reaction vessel 1
Gas is introduced into the reaction vessel 1 and exhausted from an exhaust port 8 formed at the bottom of the reaction vessel 1 .

Further, one end of the high frequency power supply 9 is connected to an impedance matching device 10.
It is connected to the cathode electrode 3 via the electrode 3.4, and the other end is grounded, so that a high frequency electric field is formed between the two electrodes 3.4.

Furthermore, a pair of mirror magnetic field generating coils lla and llb are disposed at opposing positions on the outside of the reaction vessel 1, and
In order to rotate the mirror magnetic field, multiple sets of mirror magnetic field generating coils are arranged at fixed angles with respect to the central axis of the reaction vessel 1, and each set of mirror magnetic field generating coils is sequentially switched at a fixed period. By applying electricity, the mirror magnetic field is rotated in a fixed direction to prevent uneven distribution of plasma.

When forming a thin film or etching on the wafer 5 using an apparatus having such a configuration, the unnecessary gas in the reaction vessel 1 is sufficiently exhausted through the exhaust port 8, and then the gas introduction lower, the gas flow path 6b, and each gas are removed. While the reactive gas is introduced into the reaction vessel 1 through the blow-off port 6a, a portion of the reactive gas is exhausted through the exhaust port 8, and the pressure inside the reaction vessel 1 is maintained at a predetermined value.

Next, a high frequency power of 13.56 MHz is applied to the cathode electrode 3 by the power source 9, and the coils lla and l
lb is energized to generate a mirror magnetic field, and magnetron discharge is started in the reaction vessel 1 due to the high-frequency electric field between both electrodes 3.4 and the mirror magnetic field having lines of magnetic force perpendicular to this, and a high-density gas plasma is generated. By the reaction of this high-density gas plasma, thin film formation, etching, etc. are performed on the surface of the wafer 5.

The type of reactive gas used here, the pressure, the electric power from the high frequency power source 8, etc. are appropriately selected depending on the type of Ueno treatment process.

By the way, in the case of such a plasma reactor, as mentioned above, by rotating the mirror magnetic field using multiple sets (2 to 3 sets) of mirror magnetic field generating coils, ExB
(E is electric field, B is magnetic field) In order to prevent uneven distribution of plasma due to drift and make the plasma density uniform, in this case, although the plasma density is made uniform over time,
The plasma density at any given time becomes non-uniform, and the potential of the wafer 5 in the plasma and the distribution of the surface potential of the wafer 5 become as shown in FIG. 6, for example.

However, the horizontal axis in FIG. 6 is the distance with respect to the center point of the wafer 5, and the vertical axis is the absolute value of the potential ■.
The one-dot chain line represents the potential of the wafer 5, the solid line represents the local potential on the surface of the wafer 5, and the X marks represent measurement points.

[Problem to be solved by the invention]

In the conventional case, as shown in FIG. 6, a difference occurs between the potential of the wafer 5 at any given time and the local potential of the surface of the wafer 5, and the difference in potential increases as the distance from the center of the wafer 5 increases. There is a problem in that an electric field is applied to a semiconductor device formed on the surface of the insulating film, causing damage to the formed device, especially in the case of a thin insulating film.

This invention was made in order to solve the above-mentioned problems, and it is possible to obtain a plasma reactor that maintains high-density plasma by magnetron discharge, has excellent uniformity, and causes less damage to forming devices. The purpose is to

[Means to solve the problem]

A plasma reactor according to the present invention is a plasma reactor in which two flat plate electrodes are provided in a reaction vessel in parallel and facing each other, and plasma is generated by discharge of an introduced gas between the two electrodes. The present invention is characterized in that a magnetic field generating means is provided for generating a minimal magnetic field in which the magnetic flux density becomes minimal between the two electrodes.

[Effect]

In this invention, since the magnetic field generation means generates a minimal magnetic field in which the magnetic flux density is minimal between the two electrodes, the magnetic flux density increases near the inner wall of the reaction vessel, and the plasma generated between the two electrodes is directed toward the inner wall of the reaction vessel. This suppresses the diffusion of high-density plasma between the two electrodes, and the density of the plasma between the two electrodes becomes almost uniform and axially symmetrical. This prevents damage to the devices formed on the wafer.

〔Example〕

FIG. 1 is a schematic diagram of an embodiment of the plasma reactor of the present invention.

1 is different from FIG. 5 in that, instead of the mirror magnetic field generating coils lla and llb, a multiple cusp magnetic field generating coil 12 is used as a magnetic field generating means for generating a minimal magnetic field in the reaction vessel 1. This is because it is provided on the outside of the container 1.

At this time, the multiple cusp magnetic field generation coil 12 is equipped with eight current paths parallel to the mother vessel of the hollow cylindrical reaction vessel 1, and these current paths are arranged at a constant angle with respect to the central axis of the reaction vessel 1. are arranged for each.

Although not shown in FIG. 1, both electrodes 3.4 shown in FIG. 5 are disposed within the reaction vessel 1. As shown in FIG.

By the way, FIG. 3 is a schematic cross-sectional view taken along the line xx' in FIG. 1, and by passing a current through the coil 12 in the direction of the arrow in FIG. Lines of magnetic force as shown by the arrows in the figure are generated, and a minimal magnetic field is formed in which the magnetic flux density is minimal at approximately the center of the reaction vessel 1.

Due to such a minimal magnetic field, the plasma generated in the reaction vessel 1 is confined in the inner part surrounded by the magnetic lines of force in Fig. 3, and the plasma diffusion toward the inner wall of the reaction vessel 1 is suppressed by the magnetic lines of force. , the plasma in the inner part surrounded by magnetic field lines becomes dense and uniform.

Therefore, the magnetic flux density at the center of the reaction vessel 1 is almost zero, the magnetic flux density in the plasma generation region between the picture electrodes 3 and 4 is minimal, and the magnetic flux density increases as it approaches the inner wall of the reaction vessel 1. Diffusion of plasma generated between the electrodes 3.4 toward the inner wall of the reaction vessel 1 can be suppressed, and high-density plasma can be stably maintained between the electrodes 3.4.

Furthermore, since the plasma density between the two electrodes 3.4 is almost uniform and axially symmetrical, the potential of the wafer 5 fixed to the cathode electrode 3 and the potential of the surface of the wafer 5 are approximately equal, as shown in FIG. Therefore, there is no difference between the potential of the wafer 5 and the local potential of the surface of the wafer 5 as in the conventional case, and damage to the devices formed on the wafer 5 can be prevented.
Even through verification, no breakdown voltage failure of the thin insulating film was detected.

However, similar to FIG. 6, the horizontal axis in FIG. The X mark is the potential at the potential measurement point on the surface of the wafer 5.

In the above embodiment, the multiple cusp magnetic field generating coil 12 was used as the magnetic field generating means for generating the minimum magnetic field, but the invention is not limited to this, and for example, a baseball coil or two baseball coils may be used. Needless to say, it is also possible to use opposing coils that are shifted by 90''.

〔Effect of the invention〕

As described above, according to the plasma reactor of the present invention,
In this invention, since the magnetic field generating means generates a minimal magnetic field in which the magnetic flux density is minimal between the two electrodes, it is possible to suppress the diffusion of the plasma generated between the two electrodes toward the inner wall of the reaction vessel, and the plasma generated between the two electrodes can be suppressed. High-density plasma can be stably maintained between the two electrodes, and the density of the plasma between the two electrodes is almost uniform and axially symmetrical, which eliminates the difference in potential between the wafer and the wafer surface as in conventional methods, and the wafer It is possible to prevent damage to the formed device and is extremely advantageous in etching and thin film formation using plasma generated by gas discharge.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an embodiment of the plasma reactor of the present invention, FIG. 2 is a perspective view of a part of FIG. 1, FIG. 3 is an explanatory diagram of the operation of FIG. A distribution diagram of the wafer potential and local potential on the wafer surface when using the device shown in the figure, FIG. 5 is a schematic diagram of a conventional plasma reaction device, and FIG. FIG. 3 is a distribution diagram of local potential on the wafer surface. In the figure, 1 is a reaction vessel, 3 is a cathode electrode, 4 is an anode electrode, and 12 is a multi-cusp magnetic field generating coil. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] (1) In a plasma reaction device in which two flat plate electrodes are provided in a reaction vessel in parallel and facing each other, and plasma is generated by discharge of introduced gas between the two electrodes, the magnetic flux density in the vessel is equal to the electrodes. 1. A plasma reactor characterized in that a magnetic field generating means is provided for generating a minimal magnetic field that becomes minimal between the plasma reactors.