JPH064917B2 - Plasma processing device - Google Patents

Description

The present invention relates to a plasma processing apparatus used for forming a thin film on a material surface using plasma and ions contained therein, or for etching the material surface. In particular, the present invention relates to a plasma processing apparatus suitable for manufacturing processes of various devices such as semiconductor integrated circuits.

[Prior Art] As a plasma generation method used for thin film formation and etching, there is a plasma generation method using electron cyclotron resonance by microwave excitation, which has features of low gas pressure, high ionization rate, and high activity, It has been clarified that excellent processing characteristics can be achieved by selecting the introduced gas and controlling the ion energy.

FIG. 7 shows a basic configuration diagram of a conventional plasma processing apparatus using microwave electron cyclotron resonance plasma. Here, 1 is a plasma generation chamber, 2 is a sample chamber, 12 is an exhaust passage, and 3 is a microwave introduction window, which is made of, for example, a quartz glass plate. Reference numeral 4 is a rectangular waveguide for introducing microwaves. Reference numeral 9 is a plasma extraction window for guiding the plasma generated in the plasma generation chamber 1 to the sample 11 mounted on the sample table 10. Reference numeral 13 is a magnetic coil for generating a magnetic field strength satisfying the electron cyclotron resonance condition in an appropriate region inside the plasma generation chamber 1, and the plasma flow 8
It is also used to form a divergent magnetic field to form
Microwave source, not shown, for example a frequency 2.45 GHz _Z
Composed of a magnetron. Reference numeral 5 is a cooling water passage of the plasma generation chamber, and 6 and 7 are a first gas introduction system and a second gas introduction system for introducing gas, which are used alone or in combination depending on the processing purpose.

For example, in forming the silicon nitride film, gas is introduced from the first gas introduction system 6 and SiH ₄ gas is introduced from the second gas introduction system 7. In the case of etching, the first gas introduction system 6 or the second
Introducing an etching gas from the gas introduction system 7 such as _{cl 2, SF 6, 0 2} .

The in-plane distribution of the sample in the thin film formation and the processing by etching has a certain degree of non-uniformity depending on the density of the plasma generated in the plasma generation chamber 1 and the density of the drawn plasma flow. Therefore, it is necessary to further improve the uniformity in order to apply it to a large area sample. The reaction of thin film formation and etching is mainly promoted by the electrons that have undergone cyclotron motion along the magnetic field lines of the divergent magnetic field and the ions generated by the collision of the electrons with the gas molecules. It is considered to improve the in-plane distribution of the plasma processing rate of the sample.

FIG. 8 shows a schematic configuration diagram of a plasma processing apparatus to which a conventional magnetic field distribution correction coil is added. This drawing shows an enlarged view of the sample chamber, and the configuration of the other parts is the same as in FIG. A solenoid coil 14 is arranged on the back side of the sample table 10 and a reverse current is applied to the magnetic coil 13 for divergent magnetic field to control the divergent magnetic field distribution in the sample surface.

[Problems to be Solved by the Invention] Although it is possible to improve the uniformity to some extent by the configuration of FIG. 8, since the coil has a solenoidal shape, the divergent magnetic field distribution is partially controlled and a flat process is performed. It is difficult to obtain a velocity distribution, the volume of the coil becomes large, and it is necessary to secure an installation place separately from the sample table.Moreover, in order to prevent the generation of adsorbed gas and dust from the coil, keep the coil in the sample chamber. There are various restrictions on the device configuration such as installation outside. If the magnetic field distribution in the sample surface can be controlled over a wide range to the optimum distribution, and if a small and thin coil can be made, it is possible to expect a significant improvement in characteristics such as an increase in processing area and an increase in processing speed, and the device configuration will be easy.

The present invention solves the above-mentioned conventional drawbacks, provides a plasma processing apparatus capable of controlling the divergent magnetic field distribution of a plasma flow over a wide range, improving the uniformity of the processing speed, and improving the processing area and the processing speed. To aim.

[Means for Solving the Problems] The present invention is directed to holding a sample in a plasma processing apparatus that generates plasma using microwaves and irradiates the sample with plasma or mainly ions in the plasma to perform processing. At least one flat coil for controlling the magnetic field distribution near the surface of the sample table is provided on the surface of the sample table opposite to the sample holding surface.

[Operation] The flat coil of the present invention is a thin disk-shaped coil wound spirally in the diametrical direction. By controlling the distance between the sample stage and the coil, and the coil current, a wide range of control is possible, and a flat plasma processing rate with good uniformity is possible. The combination of the coil and the sample stage can be configured integrally with the sample stage because the entire coil is thin, and the cooling water is circulated to the sample stage to cool the sample. If so, it can be used together with cooling of the coil, which is effective. Further, a bias is applied to the electrostatic attraction method for holding the sample on the sample table and the sample. Even when the RF application method is adopted, the flat coil of the present invention can be incorporated in the sample table.

Embodiments Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of a plasma processing apparatus embodying the present invention. FIG. 1 shows the sample chamber in an enlarged scale, and the configuration of the other parts is the same as in FIG. By the plasma flow 8 guided through the plasma extraction window 9 of the plasma generation chamber 1,
A sample 11 on the sample table 10 is plasma-processed. The sample table 10
A flat coil 15 is placed on the back side of the magnetic coil 13 for generating a divergent magnetic field.
And the central axes are aligned. The flat coil has a structure in which it is spirally wound in the diameter direction from the central axis. In the experimental example, a polyimide-coated copper wire with a wire diameter of 1.5 mm was used as the coil wire, and two layers were stacked to increase the magnetic field strength. The total thickness is about 3 mm and the diameter is about 10 to 20 cm.

With such a configuration, the magnetic field distribution in the sample surface of the plasma flow extracted by the divergent magnetic field is controlled by the flat coil that generates a magnetic field in the direction opposite to the divergent magnetic field. The magnetic field strength in the plane of the sample with only the divergent magnetic field is high in the central part (115 G) and gradually decreases toward the circumferential part (100 G at a position 9 cm away from the center).

In order to confirm the effect of using the flat coil of the present invention, a film formation experiment was conducted on a silicon oxide film. In this experiment, the film forming conditions were O ₂ : 30 cc / min, SiH ₄ : 30 cc / min, and microwave power: 200 W. As the sample, a 5 inch to 6 inch Si wafer was used.

FIG. 2 shows a schematic configuration diagram of a disk-shaped flat coil. The coil had a high winding density, which was wound in a spiral shape from the central axis in the direction of diameter, and had a diameter of 14 cm. The coil and the sample were separated by 5 mm. FIG. 3 shows the magnetic field distribution and the film formation speed distribution when this disk-shaped flat coil is used. The magnetic field distribution of this coil has a pyramid shape in which the magnetic field is strongest at the center of the coil.
The obtained film formation rate distribution is flatter in the central area of 4 cm at a coil current of 5 A, as compared with the case where no coil is used.
Furthermore, at a coil current of 7.5 A, the central area of 7 cm became flat.

FIG. 4 shows a schematic configuration diagram of a donut-shaped flat coil. The coil shape is 18 cm in diameter and 10 cm in the center is made hollow, and the distance between this coil and the sample stage is set to 10 mm in order to have a somewhat gentle magnetic field distribution. FIG. 5 shows the magnetic field distribution and film formation speed distribution when this donut-shaped flat coil is used. The magnetic field distribution of this coil is almost trapezoidal, and the part corresponding to the upper side of this trapezoid corresponds to the coil hollow diameter of 10 cm. The actual sample in-plane distribution is a composite with the divergent magnetic field distribution, and the diameter of 10
The magnetic field strength is high at the outer periphery of cm. As a result of using this coil, the uniformity of the film formation rate distribution was found to be improved over a wide range, and for example, there is ± 10% non-uniformity between the center of the sample surface and the position of ± 6.5 cm unless the coil is used. On the other hand, with a coil current of 10 A, the nonuniformity was reduced to ± 5%, which is half that of the conventional method. FIG. 6 shows a schematic configuration diagram of a flat coil in consideration of winding density. The central part of the coil is wound with a certain interval, and the peripheral part is wound tightly.The magnetic field distribution of this coil has a gently-decreasing curved shape from the central part of the coil to the circumferential part. Is further increased, and the uniformity of the in-plane distribution of the sample can be improved.

As a modification of the present invention, it is possible to form a magnetic field distribution that brings about the same effect by using a plate-shaped permanent magnet having a set magnetic field distribution or by combining the present invention with a high magnetic permeability material such as soft iron. Further, it is possible to further enhance the controllability of the magnetic field distribution by combining a plurality of flat coils.

[Effects of the Invention] As is clear from the above description, in the apparatus of the present invention, the flat coil is used to control the distribution of the divergent magnetic field over a wide range, so that the uniformity of the plasma processing rate is improved and There is an advantage that the processing area can be widened and the throughput can be improved, and in terms of the apparatus configuration, it can be easily combined with the sample table.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an embodiment of the present invention, FIG. 2 is a schematic sectional view of a disk-shaped flat coil, and FIG. 3 is a magnetic field distribution and a SiO ₂ film formation rate distribution when the disk-shaped flat coil is used. Showing the fourth
The figure is a schematic cross-sectional view of a donut-shaped flat coil. Fig. 5 shows the magnetic field distribution and SiO ₂ film formation rate distribution when the donut-shaped flat coil is used. Fig. 6 shows the flat coil with different winding density. FIG. 7 is a schematic sectional view, FIG. 7 is a basic configuration diagram of a plasma processing apparatus, and FIG. 8 is a schematic view of an apparatus using a conventional magnetic field distribution correction coil. 1 ... Plasma generation chamber, 2 ... Sample chamber, 3 ... Microwave introduction window, 4 ... Rectangular waveguide, 5 ... Cooling water channel, 6 ... First gas introduction system, 7 ... Second gas introduction system, 8 ... Plasma flow , 9 ... Plasma extraction window, 10 ... Sample stage, 11 ... Sample, 12 ... Exhaust system, 13 ...
Magnetic coil, 14 ... Solenoid coil, 15 ... Flat coil.

Claims (1)

[Claims] 1. A plasma is generated using microwaves,
In a plasma processing apparatus that performs processing by irradiating a sample with the plasma or mainly ions in the plasma, a magnetic field distribution near the surface of the sample table on a surface of the sample table opposite to the sample holding surface for holding the sample. A plasma processing apparatus, comprising at least one flat coil for controlling the temperature.