JPH0641633B2 - Microwave plasma processing equipment - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a processing apparatus using microwave plasma among plasma processing apparatuses for manufacturing semiconductor elements and the like using low-temperature plasma, and particularly to CVD, etching, The present invention relates to a microwave plasma processing apparatus suitable for large area processing of various technologies such as sputtering.

[Conventional technology]

With the miniaturization of semiconductor elements, dry process has become an important technology. Above all, plasma processing technology using microwaves has been regarded as important. For example, plasma discharge using electron cyclotron discharge (ECR) by microwave discharge can discharge at low pressure (10 ^-5 Torr), so that generated ions can be aligned in the direction, high-density plasma can be generated, and electrodeless Since it is an electric discharge, it has a long life, and active gas can be used. FIG. 4 shows the basic structure of a conventional plasma generation source using ECR discharge and an ECR-CVD apparatus using the same. The microwave source not shown is, for example, 2.45GH
It is constructed using a magnetron of z. Generally, the microwave waveguide 3 is a rectangular waveguide of 96 mm × 27 mm or 109 mm × 54 mm. Further, the plasma generation chamber 1 has an inner diameter of about 200 mm, and often has a microwave cavity structure to efficiently input microwave power. The microwave power introduced into the plasma generation chamber 1 by the waveguide 3 is consumed to generate plasma. The generated plasma is drawn out toward the sample 9 from the plasma drawing window 10. The plasma extraction window 10 is provided for securing the cavity resonator structure of the plasma generation chamber 1 and for extracting a uniform portion of the generated plasma. That is, the electric field strength of the microwave is weakened in the peripheral portion of the plasma generation chamber 1, and there is a difference in plasma density generated in the central portion and the peripheral portion, so that only a uniform portion is drawn out. The magnetic coil 4 is provided to achieve a direct current magnetic field (875 Gauss) satisfying so-called ECR conditions. The generated plasma efficiently diffuses toward the sample 9, which is the weak magnetic field region. As described above, substrate processing such as CVD and etching can be performed by the plasma reaching the sample 9.

The microwave plasma processing apparatus in the prior art has a structure in which the microwave power generated by the magnetron is introduced into the plasma generation chamber 1 via the waveguide 3 as described above. Usually, the propagation mode of the microwave in the waveguide is the rectangular TE10 mode as shown in FIG. 5, and when the plasma generation chamber 1 is circular, the microwave mode is the TE11 mode as shown in FIG. Occurs. In addition, (a) and (b) in FIG. 5 and FIG. 6 are a horizontal cross section and a vertical cross section, respectively.

As a technique capable of generating a microwave plasma having a larger area, there is a technique for controlling a microwave mode as described in, for example, JP-A-1-122123. In the present technology, as shown in FIG. 7, two sides where the cross-sectional shapes of the microwave waveguide 3 and the connection surface 2 of the plasma generation chamber 1 face each other are arcs of concentric circles about the axis of the plasma generation chamber 4 It was intended to control the microwave mode by making the shape of a quadrangle. In this technology TM
O1 mode, TM11 mode, etc. can be formed.

[Problems to be Solved by the Invention]

However, the plasma generation technique using microwaves of TMO1 mode and TM11 mode described in JP-A-1-122123 has the following problems. For TE11 mode, TM11 mode, and TMO1 mode, the radius a of the cylindrical waveguide has the following relationship when the cutoff wavelength of the propagating microwave is λc.

λc = 3.412a (TE11 mode) λc = 1.640a (TM11 mode) λc = 2.613a (TMO1 mode) From the above formula, the TM11 mode has a radius a2.08 times the cylindrical waveguide radius in the TM11 mode compared to the conventional TE11 mode. Then it can be increased to 1.31 times. However, in the TM11 mode, there is a problem that the electromagnetic field distribution of microwaves is not uniform as shown in FIG. 8 and thus uniform plasma cannot be generated. As shown in FIG. 9, the electromagnetic field distribution of the eye wave is uniform in the TMO1 mode, but from the viewpoint of increasing the area, it is only 1.31 times the size of the conventional TE11 mode.

An object of the present invention is to provide a plasma processing apparatus that efficiently introduces uniform microwave power into a plasma generation chamber over a large area.

[Means for Solving the Problems]

The microwave plasma processing apparatus of the present invention is a plasma processing apparatus comprising a waveguide connected to a microwave power supply and a plasma generation chamber connected to the waveguide, and at least one of the waveguide and the plasma generation chamber. The cross-sectional shape of the connecting surface with the chamber is characterized in that the line of intersection between the H surface of the waveguide and the connecting surface is a radius, and the line of intersection between the E surface and the connecting surface is an arc. It is a thing.

[Action]

With the above configuration, the propagation mode in the plasma generation chamber becomes the TEO1 mode, as will be described in detail later, microwave power is efficiently and uniformly propagated in the plasma generation chamber, and a plasma with a larger area than in the past is generated. Is possible.

〔Example〕

FIG. 1 shows an embodiment of the present invention. As mentioned above, with a regular rectangular waveguide, 96 mm × 27 mm or 109 mm
A x54 mm waveguide was used. In these waveguides
Since microwaves propagate in the TE10 mode, for example, if it is simply connected to a plasma generation chamber with a cylindrical shape, generation of TE11 mode or generation of harmonic components is promoted in the plasma generation chamber, and it is difficult to obtain a uniform microwave electric field. . Therefore, in order to uniformly input microwave power, for example, in order to generate a microwave mode having electric lines of force parallel to the side wall of the plasma generation chamber 1 having a cylindrical shape, two short shapes of the rectangular waveguide 3 are formed. A converter 20 is connected so that one of the sides is an arc and the remaining one is the center point of the arc. The length of this converter is, for example, the wavelength (2.
The length may be equal to or longer than 122 mm for 45 GHz). As described above, the lines of electric force of the microwave have lines of electric force parallel to the circular arc. FIG. 2 shows an example in which microwaves can be introduced in a large area by arranging a plurality of the converters 20 described above.

FIG. 3 is a diagram showing an electromagnetic field distribution in a cross section according to FIGS. 2 (a) to (e). As shown in FIG. 3, the TE10 mode (a) which is a propagation mode in a general rectangular waveguide is transformed as shown in (b) → (c), and further, (c) →
A surface (E surface) that is stacked with (d) and is parallel to the lines of electric force.
Becomes a circular arc and the partition wall (H surface) perpendicular to the lines of electric force is removed to obtain a circular TE01 mode as shown in (e). The size of the cylindrical waveguide for generating the TE01 mode thus obtained is larger than that of the rectangular waveguide used for the TE10 mode propagation conventionally used, and the microwave power can be uniformly propagated. It will be possible. Therefore, the diameter of the waveguide connected to the plasma generation chamber can be increased, and the TE01 mode can be used to propagate microwaves with a uniform distribution regardless of the size of the waveguide diameter. Can be generated.

FIG. 2 shows an example in which a large-area TE01 mode waveguide is formed by using eight rectangular waveguides. However, the effect of the present invention can be achieved without particular limitation on the number of rectangular waveguides. One may be used as shown in FIG. Further, the effect shown in the present invention can be obtained even if one or more arbitrary waveguides are omitted from the waveguides shown in FIG.

In the TE01 mode, the microwave cutoff wavelength λc and the radius a of the cylindrical waveguide satisfy the relationship of λc = 1.640a, so that the size of the conventional TE11 mode microwave waveguide can be increased by 2.08 times. .

According to the present invention, by positively utilizing the TE01 mode microwave, the size of the waveguide can be increased, and the microwave power can be uniformly input to the large-area plasma generation chamber.

〔The invention's effect〕

Since the present invention can control the microwave propagation mode so as to be suitable for large-area plasma generation, large-area microwave plasma processing can be performed. By using the microwave plasma processing apparatus according to the present invention, it is possible to perform uniform and large-area processing for each process of etching, deposition, sputtering, ion beam mixing, and ion implantation.

[Brief description of drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention, FIG. 2 is a diagram showing a second embodiment of the present invention, and FIG. 3 is a diagram from a rectangular waveguide to a large cylindrical waveguide according to the present invention. Fig. 4 is a diagram showing an example of a conventional plasma processing apparatus, Fig. 5 is a diagram showing an electromagnetic field distribution in a TE10 rectangular waveguide, and Fig. 6 is a TE11 mode cylindrical conductor. FIG. 7 is a diagram showing an electromagnetic field distribution in a wave tube, FIG. 7 is a diagram showing an example of a prior art relating to large-area plasma generation, and FIGS. 8 and 9 are electromagnetic field distributions in a TM11 mode and TM01 mode cylindrical waveguide, respectively. Fig. 1 ... Plasma generation chamber, 2 ... Microwave introduction window, 3 ... Microwave waveguide, 4 ... Magnetic coil, 5 and 6 ... Gas introduction port, 7 ... Plasma flow, 8 ... Sample stage, 9 ... Sample.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Takaharu Oshima 46-59 Nakahara, Tobata-ku, Kitakyushu, Fukuoka Prefecture Nippon Steel Corporation Machinery & Plant Division

Claims (1)

[Claims] 1. A plasma processing apparatus comprising a waveguide connected to a microwave power source and a plasma generation chamber connected to the waveguide, wherein at least one connection surface between the waveguide and the plasma generation chamber. The plasma processing apparatus is characterized in that the cross-section has a radius of intersection between the H-plane and the tangential plane of the waveguide and an arc between the E-plane and the connection plane.