JPH0614521B2 - Microwave plasma processing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline] In a microwave plasma processing apparatus for performing plasma processing with microwaves transmitted through a microwave transmission window provided in a direction perpendicular to an electric field of microwaves traveling in a microwave waveguide, By keeping the distance between the inner surface of the microwave waveguide and the surface of the stage on which the object is placed opposite to each other across the transmission window to 1/2 or less of the wavelength of the microwave, the matching area can be widened and the device can be handled easily. It is easy to train.

[Industrial application field]

The present invention relates to a microwave plasma processing apparatus used in a wafer process or the like for manufacturing a semiconductor device.

In a wafer process for manufacturing a semiconductor device, a dry process technique tends to be frequently used along with miniaturization of a pattern, but it is desired to increase a process speed and a process temperature.

In order to meet the demand, there is a microwave plasma processing device that performs etching or film formation on the wafer surface by a chemical reaction using plasma, but the processing speed, processing temperature, etc. are further improved and handling becomes easier. Is desired.

[Conventional technology]

The conventional microwave plasma processing apparatus is as shown in the side sectional view of the main part of FIG.

That is, the central discharge chamber 21 is vacuum-sealed by a discharge tube 22 made of a dielectric material (quartz or alumina) for transmitting microwaves, and a processing object A such as a wafer is placed below the discharge chamber 21. The stage 23 is arranged so that the object A to be processed is discharged from the discharge chamber 21.
During this period, a mirror magnetic field is applied by the solenoid coil 24 and the permanent magnet 25, the discharge chamber 21 and the processing chamber 26 are exhausted to a predetermined pressure close to a vacuum, and the reaction gas is introduced from the gas inlet 27 and generated in the magnetron 28. 2.45 GHz microwave 31 passing through the rectangular waveguide 29 and the circular waveguide 30 into the discharge tube 2
The upper surface 22a of 2 is introduced into the discharge chamber 21 as a microwave transmission window, and plasma is generated in the discharge chamber 21 to process the object A (for example, written by Takuo Sugano: Semiconductor Plasma Process Technology, Showa Showa). 55, Industrial Books, p. 139).

In the figure, reference numeral 32 denotes a stub made of a metal rod for reflecting the microwave reflected from the discharge tube 22 side again and correcting misalignment due to variations and fluctuations of the magnetron 28. The above correction is carried out by changing the insertion length into the inside.

Conventionally, an apparatus that introduces microwaves into a vacuum processing chamber, generates a process, and processes an object to be processed includes a microwave transmission window that is made of quartz or alumina that transmits microwaves and that vacuum-seals the vacuum processing chamber. It is generally provided perpendicularly to the traveling direction of the microwave (hereinafter, such a method is referred to as a vertical incidence method), and specific examples thereof are JP-B-53-24779, JP-B-53-34461, and JP-A-53-34461. See, for example, Japanese Patent Publication No. 53-110378.

[Problems to be solved by the invention]

In the device of the vertical incidence method described above, when the microwave is introduced into the vacuum processing chamber, the microwave is generated at the interface between the atmosphere on the waveguide side and the microwave transmitting window and between the microwave transmitting window and the vacuum processing chamber. It reflects at two points on the interface.

On the other hand, the reflection of microwaves is deviated by λ / 2 (where λ is a wavelength) between reflection when traveling from a region having a small dielectric constant to a region having large permittivity and reflection when traveling from a region having a large dielectric constant to a region having small permittivity. Occurs.

The permittivity of the vacuum processing chamber changes significantly depending on the presence or absence of plasma. If the permittivity of the waveguide side, the microwave transmission window, and the vacuum treating chamber are ε ₁ , ε ₂ , and ε ₃ , respectively, the plasma When there is no plasma, ε ₁ <ε ₂ > ε ₃ , and when there is plasma, ε ₁ <ε ₂ <ε ₃ .

Therefore, the microwave is well transmitted through the microwave transmission window in the absence of plasma, that is, the phases of the reflected waves reflected at the two locations are reversed when the plasma is absent. If the thickness is set, the phase of the reflected waves will be aligned when the plasma is generated, and the microwave transmission will be poor, so it is practical to improve the microwave transmission with or without plasma. It is impossible and no matter how the stub is adjusted, there is a problem that the utilization efficiency of microwaves for plasma generation is poor.

Further, when plasma is generated, microwaves are rapidly attenuated from the microwave transmission window toward the inside of the vacuum processing chamber, and the plasma density is accordingly reduced.

Therefore, when the object to be processed is placed near the microwave transmission window in order to increase the processing speed and aiming at a place where the plasma density is high, the object to be processed and the stage on which the object to be processed are placed are conductive. In this case, these planes become the fuss of the electric field (the electric field is the minimum), and it becomes difficult to effectively generate plasma depending on the distance from the microwave transmission window.

Therefore, in the conventional vertical incidence method, it is necessary to increase the distance () between the microwave transmission window and the stage, for example, λ / 4 or more. There is a problem that it becomes low and the processing speed becomes slow.

Specifically, when the resist is ashed by oxygen radicals, if the ash is 4 cm or more at 4 Torr or 4 cm or more at 1 Torr, the ashing can be performed but the speed is slow.

[Means for solving problems]

FIG. 1 is a side sectional view of a main part of an embodiment of a microwave plasma processing apparatus according to the present invention.

The above-mentioned problems are caused by the vacuum treatment in which the microwave waveguide 11 having the microwave transmission window 13 provided in the direction perpendicular to the electric field of the microwave 12 and the microwave transmission window 13 are vacuum-sealed as shown in FIG. The chamber 14 and the vacuum processing chamber 14 face the microwave transmission window 13 and place the object A to be processed thereon.
15 and an exhaust port 16 and a gas introduction port 17 are provided, and the distance a between the inner surface of the microwave waveguide 11 and the surface of the stage 15 which are opposed to each other with the microwave transmission window 13 interposed therebetween is 1 of the wavelength of the microwave 12.
The problem is solved by the microwave plasma processing apparatus of the present invention, which is ½ or less.

[Action]

The main body of the above microwave plasma processing apparatus is the one disclosed by the inventor of the present application in Japanese Patent Application No. 59-252909, and by providing the microwave transmitting window 13 in the direction perpendicular to the electric field of the microwave 12, The microwave 12 can be introduced into the vacuum processing chamber 14 without disturbing the mode of the wave 12, so that the plasma can be efficiently generated and the plasma can be contributed to the processing of the object A to be processed. Has a feature that it is smaller than the conventional one.

The present invention adds to this device a requirement regarding the distance a between the inner surface of the microwave waveguide 11 and the surface of the stage 15 which are opposed to each other with the microwave transmission window 13 interposed therebetween.

The microwave 12 in the microwave waveguide 11 has a component parallel to and a component perpendicular to the microwave transmission window 13. The parallel component does not change the mode before and after the plasma generation, but the vertical component changes the mode under the influence of the state change of the plasma generation region.

Therefore, if the distance a between the inner surface of the microwave waveguide 11 and the surface of the stage 15 which are opposed to each other with the microwave transmission window 13 interposed therebetween is set to be half the wavelength of the microwave 12 or less, most of the vertical component is present in that region. The entire microwave 12 mode becomes extremely stable before and after plasma generation.

This also facilitates handling of the device, such as widening the alignment area of the device and facilitating adjustment of the stub 18 for alignment.

〔Example〕

In the embodiment shown in FIG. 1, the microwave of 2.45 GHz 12
And the distance a between the upper wall inner surface of the microwave waveguide 11 and the surface of the stage 15 is set to 40 mm, and the distance b between the lower surface of the microwave transmission window 13 and the surface of the stage 15 is set to 3 mm.
Oxygen was introduced into 14 at a rate of 300 cc / min, the vacuum degree was 0.3 Torr, and the resist on the wafer to be processed A was ashed with a power of 1.5 KW, and the adjustment position of the stub 18 was within the range of about 10 mm. In all, it was possible to incinerate at an etching rate of about 5 times that of the conventional example, and even if the resist contained an altered layer, it could be removed neatly.

Further, at this time, when the stage 15 was cooled by the present apparatus, the temperature of the object to be processed A became 100 ° C. or lower,
In the case of normal plasma treatment, it was possible to carry out the treatment at a lower temperature than that of 200 ° C or higher.

When the distance a was set to 80 mm, the adjustment position range of the stub 18 for obtaining ashing similar to the above was about 5 mm.

In comparison with this, setting the interval a to be half the wavelength of the microwave 12 or less facilitates the adjustment of the stub 18.

〔The invention's effect〕

As described above, according to the configuration of the present invention, it is possible to provide a compact microwave plasma processing apparatus that can efficiently and easily handle microwaves and can process an object at low temperature. Therefore, it is possible to improve the processing quality and the processing speed.

[Brief description of drawings]

FIG. 1 is a side sectional view of a main part of an embodiment of a microwave plasma processing apparatus according to the present invention, and FIG. 2 is a side sectional view of a main part of a conventional microwave plasma processing apparatus. In the figure, 11, 29 and 30 are microwave waveguides, 12 and 31 are microwaves, 13 and 22a are microwave transmission windows, 14 and 26 are vacuum processing chambers, 15 and 23 are stages, 16 is an exhaust port, 17 27 is a gas inlet, 18 and 32 are stubs, and A is an object to be treated.

Claims (1)

[Claims] 1. A microwave waveguide (11) having a microwave transmission window (13) provided in a direction perpendicular to an electric field of the microwave (12), and a vacuum sealed by the microwave transmission window (13). The vacuum processing chamber (14) includes a stage (15) facing the microwave transmission window (13) on which the object (A) to be processed is placed, an exhaust port (16), and a processing chamber (14). A gas inlet (17) is provided, and a gap (a) between the inner surface of the microwave waveguide (11) and the surface of the stage (15) facing each other with the microwave transmission window (13) interposed therebetween is
A microwave plasma processing apparatus, characterized in that the wavelength is ½ or less of the wavelength of the microwave (12).