JPH053736B2 - - Google Patents

Description

[Detailed Description of the Invention] [Summary] A microwave transmission window is placed parallel to the microwave electric field.
Alternatively, in a vertically installed microwave plasma processing apparatus, as a countermeasure against the rapid attenuation of plasma as it approaches the object to be processed from the window in the processing chamber, especially in the latter case, the structure is such that the microwave does not pass between the object to be processed and the object to be processed. You can reduce the spacing between windows. Therefore,
Since radiation when the window material is heated by plasma can impair the treatment distribution and, in extreme cases, even cause damage to the device, we propose a device that efficiently cools the window with cooling gas. .

[Industrial application field]

The present invention relates to a microwave plasma processing apparatus in which a microwave transmission window is provided with air cooling means.

In the manufacture of semiconductor devices, as elements become smaller, processes are becoming increasingly dry, and microwave plasma processing is one such process, which is frequently used for etching and resist ashing (ashing and peeling).

A microwave plasma processing device is a device that guides 2.45GHz microwaves generated by a magnetron into a processing chamber through a waveguide, generates plasma, and processes the object to be processed.

At this time, a vertical incidence method is generally used in which a microwave transmission window is provided parallel to the electric field of the microwave (perpendicular to the propagation of the microwave).
In the specification of No. 252909, a horizontal incidence method was proposed in which a microwave transmission window is provided perpendicular to the microwave electric field (parallel to the direction of microwave propagation).

In the vertical incidence method, when microwaves are introduced into the processing chamber, they are reflected at the interface between the atmosphere on the waveguide side and the window material, and the interface between the window material and the plasma on the processing chamber side, and the processing chamber is vacuumed. The impedance varies greatly from the plasma to the plasma, making it difficult to create well-matched threads. Further, since the microwave is rapidly attenuated as it enters the processing chamber through the transmission window, it is difficult to uniformly plasma-process the entire object to be processed.

In contrast, in the horizontal incidence method, an insulator (window material) is placed perpendicular to the electric field that generates microwaves, so microwaves are efficiently introduced into the processing chamber and uniformly spread over the entire object to be processed. can be brought into contact with plasma. However, when the window material of the transmission window is heated by plasma, radiation can impair the processing distribution and, in extreme cases, may cause damage to the device, so measures to cool the transmission window are desired.

Therefore, in the present invention, the horizontal incidence method, which is easily affected by the radiant heat of the window material, will be explained as an example.

Next, for comparison, a similar example of the present invention in which the inside of the waveguide or the gas activation chamber is cooled will be described.

JP-A-59-177931 The device disclosed in this specification by the present inventor is designed to prevent shortening of the service life of a magnetron and an antenna by flowing a cooling gas into a waveguide in a vertical incidence system. This is what I did.

Utility Model Publication No. 56-5309, JP-A No. 53-60882 The gas activation chamber passing through the waveguide has a double structure, with the inner cylinder serving as the active gas passage region, and cooling gas or A liquid is pumped in to cool the inner cylinder to prevent etching of the quartz inner cylinder.

In this case, the activated gas generated in the gas activation chamber is introduced into the processing chamber.

[Conventional technology]

FIG. 4 is a sectional view of a conventional microwave plasma processing apparatus in which a microwave transmission window is provided in a direction perpendicular to the electric field.

In the figure, 1 is a waveguide, 2 is a microwave generated by conventional means and propagates in the direction of the arrow, 3 is a microwave transmission window made of quartz or ceramic, 4 is an object to be processed, and 5 is a to be processed. A stage on which the body is placed, 6 an exhaust port connected to a normal exhaust system (not shown), and 7 a reaction (etching) gas inlet for processing.

As shown in the figure, since the microwave transmission window is installed perpendicular to the electric field, the microwave mode is efficiently absorbed into the processing chamber without being disturbed, so it was confirmed that matching could be achieved easily. .

According to actual measurements by the present inventor, in O ₂ plasma at a pressure of 1 Torr, the reflection of microwaves is extremely small, 30% without matching and 5% with matching, making high-speed processing possible.

However, the distance between the microwave transmission window 3 and the object to be processed 4 is reduced due to the attenuation of the plasma in the processing chamber.
Therefore, the window material of the microwave transmission window 3 is heated by the plasma to a temperature of 300 to 500°C, and the radiation from this deteriorates the processing distribution of the object to be processed 4. In extreme cases, it may cause device damage.

[Problem that the invention seeks to solve]

In a conventional microwave plasma processing apparatus in which a microwave transmission window is provided in a direction perpendicular to an electric field, radiant heat from the window material deteriorates the processing distribution of the object to be processed, and in extreme cases may cause damage to the device.

[Means for solving problems]

The above problem can be solved by the present invention, in which a microwave transmission window is arranged between a microwave waveguide whose inside is at atmospheric pressure and a microwave plasma processing chamber which is in a reduced pressure state. The problem is solved by a microwave plasma processing apparatus characterized in that a cooling means is provided for blowing cooling gas from the side into the center of the microwave transmission window.

[Effect]

In the present invention, when air cooling a microwave transmission window,
To enhance the cooling effect by blowing out cooling gas to the center of the window.

1 and 2 in FIG. 2 are a sectional view and a plan view of a microwave plasma apparatus used in an experiment to explain the principle of the present invention.

In the figure, point A is the position where the cooling gas is discharged from inside the waveguide, point B is the center of the window, and point C is the position where the cooling gas is blown onto the window. With respect to point B, point A is symmetrical with point C. It is in.

The cooling effect in this case is shown in FIG. 3 below.

FIG. 3 is a diagram in which the temperature rise at each position was measured with respect to the elapsed time after plasma introduction.

In the figure, Without air cooling, point B would be the highest temperature.

The degree of cooling expressed by the difference between the curve with air cooling and the curve without air cooling near the saturation of the temperature rise is about 150° C., which is the same at both points B and C.

Similar degrees of cooling are approximately 100°C at point A, and at point B,
It is difficult to cool down from point C.

From the above, it is considered to be effective to blow cooling gas directly into the center of the window.

〔Example〕

FIG. 1 is a sectional view of a type of microwave plasma processing apparatus in which a microwave transmission window is provided in a direction perpendicular to an electric field according to the present invention.

In the figure, 1 is a waveguide, 2 is a microwave generated by conventional means and propagates in the direction of the arrow, 3 is a microwave transmission window made of quartz or ceramic, 4 is an object to be processed, and 5 is an object to be processed. 6 is an exhaust port connected to a conventional exhaust system, 7 is a stage on which the
is a reaction gas inlet for processing, and the above is completely the same as in the conventional example.

In the present invention, a blower 8 is provided in the waveguide 1 corresponding to the position where the cooling gas is blown onto the central part B of the microwave transmission window 3. Further, for example, point A,
An exhaust port or exhaust fans 9 and 10 are provided in the waveguide 1 corresponding to point C.

The blower 8, the exhaust port, or the exhaust fans 9, 10 are attached to the waveguide 1 while being electromagnetically shielded.

With the device having the above structure, the microwave transmission window can be efficiently cooled.

In the embodiment, a horizontal incidence type device which is highly effective has been described, but the gist of the present invention does not change even if it is applied to a vertical incidence type device.

〔Effect of the invention〕

As described in detail above, in the microwave plasma processing apparatus according to the present invention, the processing distribution of the object to be processed is prevented from becoming poor due to the radiant heat of the window material, and furthermore, damage to the device is prevented.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of a microwave plasma processing apparatus according to the present invention in which a microwave transmission window is provided perpendicular to the electric field, and Fig. 2 is a cross-sectional view of a microwave plasma processing apparatus according to the present invention in which a microwave transmission window is provided in a direction perpendicular to the electric field. A cross-sectional view and a plan view of the wave plasma device. Figure 3 is a diagram showing the temperature rise at each location measured over the elapsed time after plasma introduction. Figure 4 shows a conventional microwave transmission window installed perpendicular to the electric field. 1 is a sectional view of a type of microwave plasma processing apparatus. In the figure, 1 is a waveguide, 2 is a microwave, and 3 is a waveguide.
is a microwave transmission window, 4 is an object to be processed, 5 is a stage, 6 is an exhaust port, 7 is a gas inlet port, 8 is a blower,
9 and 10 are exhaust ports or exhaust fans.

Claims (1)

[Claims] 1. In a configuration in which a microwave transmission window is placed between a microwave conductive tube whose interior is at atmospheric pressure and a microwave plasma processing chamber where the pressure is reduced, the microwave transmission window is opened from the microwave waveguide side. A microwave plasma processing apparatus characterized in that a cooling means for spraying cooling gas is provided in the central part.