JPS6258631A - Microwave plasma processor - Google Patents

Abstract

PURPOSE:To improve the performance of a processor by setting a breakdown problem of transmitting windows by a method wherein microwave transmitting windows are formed of multiple windows at the interval of wavelength in tube/4. CONSTITUTION:Microwaves are led into a plasma processing part through microwave transmitting windows 1 provided in parallel with the advancing direction of microwave to plasma-process a specimen 2 to be processed by turning gas in the plasma processing part into plasma. At this time, the transmitting windows 1 are formed of multiple windows at the interval of lambdag/4 (lambdag: wavelength in tube). In such a constitution, the transmitting windows 1 become slit type small windows hardly broken while the plasma processor fills the role of subwaveguide of microwaves to suffice the plasma region regardless of small opening space of respective windows. Through these procedures, the performance of processor can be improved by settling the breakdown problem of transmitting windows 1.

Description

[Detailed Description of the Invention] [Summary] In a horizontal incidence type microwave plasma processing apparatus,
The microwave transmission window is composed of a plurality of small windows spaced apart by λg/4.

[Industrial Field of Application] The present invention relates to a microwave plasma processing apparatus, and particularly to improvement of a plasma processing apparatus for higher performance.

As a process technology for semiconductor manufacturing, dry processing has become a very important technology for miniaturization and high integration of semiconductor devices. Recently, plasma processing using microwaves has been used in such dry processes.
It is used in the process of plasma etching with 10 oxygen gas. This microwave (2.45 GH2) plasma treatment has the advantage of higher excitation efficiency than conventional plasma treatment using high frequency (13.56 MH2).

However, there are still some aspects of this type of microwave plasma processing equipment that have not been sufficiently studied, and these problems have been studied and
Must be improved.

[Prior Art] Generally, in a microwave plasma processing apparatus, a microwave generation section and a plasma processing section (chamber) are connected by a waveguide. In many cases, a window was provided and microwave power was introduced into the plasma processing chamber through the microwave-transmitting window. Here, the microwave-transmitting window is a window that allows microwaves to pass through while vacuum-sealing the inside of the plasma processing chamber, and quartz or alumina is suitable material.

By the way, in contrast to the so-called vertical incidence method of microwaves in which a microwave transmission window is provided perpendicularly to the direction of microwave propagation (electric field direction), the inventor proposed a method in which microwaves are (Refer to Japanese Patent Application No. 59-252909) in order to develop a microwave plasma processing apparatus that uses a so-called horizontal incidence microwave method, which is provided with a transmission window.

FIG. 4 shows a side cross-sectional view of the horizontal incidence type microwave plasma processing apparatus, and FIG. 5 is a cross-section taken along line AA' in the same figure. 1 is a microwave transmission window, 2 is a wafer to be processed, 3 is a waveguide, 4 is a plasma processing chamber, and a magnetron (
A microwave of 2,45 GH2 generated by The light is transmitted through the transmission window 1 and introduced into the plasma processing chamber 4.

On the other hand, in the plasma processing chamber 4, the wafer 2 is placed parallel to the transmission window 1, and while being vacuum-suctioned from the exhaust port 5,
A reaction gas is introduced from the other gas inlet 6 to reduce the degree of pressure reduction to 0. The pressure should be approximately 1 Torr to several Torr. Then, the inflowing reaction gas is turned into plasma by the microwave, and the plasma-excited gas reacts with the wafer to perform plasma etching.

Compared to vertical incidence processing equipment, horizontal incidence processing equipment has far less microwave reflection, extremely good matching, and generates plasma efficiently, allowing wafers to be processed at high speed. . In microwave plasma processing equipment, there is a problem in that microwaves must be sequentially introduced into the atmosphere with different dielectric constants (ε), into a transmission window, and into a vacuum (depressurized). If matching is achieved in the vacuum state of the plasma processing chamber (no plasma is being generated), a paradoxical situation arises in that in the state where plasma is generated, reflection becomes stronger and matching cannot be achieved, which has the disadvantage that matching is not very good. .

On the other hand, in the horizontal incidence method, the electric field is applied perpendicularly to the transmission window, which improves this, allows for a smaller plasma processing chamber, and has the advantage of good microwave matching and extremely low microwave reflection. be.

For details, please refer to the above-mentioned Japanese Patent Application No. 59-252909.

[Problems to be Solved by the Invention] By the way, one of the important problems in such a horizontal incidence type microwave plasma processing apparatus is the microwave transmission window 1, which is easily damaged. There is a drawback.

As mentioned above, quartz or alumina are suitable materials for maintaining vacuum sealing and transmitting microwaves.
Of these, quartz has good heat resistance, but is easily etched by fluorine-based gases such as CF4, making it unsuitable for processing semiconductor substrates.

Therefore, in the etching process of semiconductor substrates, an alumina plate is used as the transmission window 1.
At temperatures above ℃, the bending strength rapidly deteriorates and becomes brittle, and since the alumina plate is used as a vacuum-sealed window, it cannot withstand atmospheric pressure and often breaks. In a microwave plasma processing apparatus, a transmission window portion is usually heated to 300 to 400° C. by plasma heat.

Therefore, if the transmission window is made smaller, the strength against destruction can be maintained, but then a plasma region of the required size cannot be obtained.

The present invention proposes a microwave plasma processing apparatus that eliminates these drawbacks.

[Means for solving the problem] The purpose is achieved by a microwave plasma processing apparatus in which the microwave transmission window is composed of a plurality of windows with an interval of λg/4 (λg: wavelength in the tube). be able to.

[Function] That is, the present invention is made small so that it is difficult to be destroyed, and provides a plurality of transmission windows with an interval of λg/4 (λg is the wavelength in the waveguide) so that microwaves can easily pass through. .

[Example] An example will be described in detail below with reference to two drawings.

FIG. 1 is a side sectional view of a microwave plasma processing apparatus according to the present invention, in which the same members as in FIG. 4 are given the same symbols.

As shown in the figure, the microwave transmission window 1 has a support frame 12 interposed below the alumina plate 11, and as shown in FIG.
s, IS'. Moreover, the distance between the centers of the two rectangular aperture transmission windows is set to IQ,'I between λg/4.

In this way, the small slit-shaped windows are difficult to break, and the plasma processing chamber becomes a sub-waveguide for microwaves, so even if the opening area of each window is made small,
Sufficient plasma area is obtained. That is, like a microwave directional coupler, holes are created in the coupling system so that one phase becomes the other phase, and by doing so, the plasma region becomes wider as in the conventional method.

To explain with a specific numerical example, when oxygen plasma is excited in a reduced pressure of 1 Torr using a microwave (2,45G) IZ) with a power of 1.5KH, the conventional alumina with a circular opening of 110 mm The transparent window was destroyed within 2 minutes. However, each has a width of 110 dragons and a length of 27 dragons in the direction of travel.
When two 1m slit-shaped aperture transmission windows are provided and the center distance is set to λg / 4 (about 37m), the windows are 1m long.
It did not break even after being exposed to plasma for 0 minutes.

FIG. 3 shows a cross-sectional perspective view of the transmission window portion of the embodiment explained in FIGS. is very clear.

Although the above example has been described with two square opening windows, the invention is not limited to two windows.

[Effects of the Invention] As can be seen from the above description, according to the present invention, damage to the alumina transmission window is eliminated, contributing to improved performance of the microwave plasma processing apparatus.

[Brief explanation of the drawing]

Fig. 1 is a side cross-sectional view of a microwave plasma processing apparatus according to the present invention, Fig. 2 is a plan view of the microwave plasma processing apparatus according to the present invention as seen from the wafer side, and Fig. 3 is a cross-section of the transmission window portion thereof. A perspective view, FIG. 4 is a side sectional view of a conventional microwave plasma processing apparatus, and FIG. 5 is a sectional view along line AA' in FIG. 4. In the figure, 1 is a transmission window, 2 is a wafer, 3 is a waveguide,
4 is a plasma processing chamber, 5 is an exhaust port,
6 is a reaction gas inlet, 11 is an alumina plate, 1
2 is the support frame, Is, IS" is the rectangular opening transparent window $Llr += or P3';'>2"z8fflkofq
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Claims (1)

[Claims] Microwave plasma processing in which microwaves are introduced into a plasma processing section through a microwave transmission window provided parallel to the direction of microwave propagation, the gas in the plasma processing section is turned into plasma, and the sample to be processed is plasma-treated. It is a device,
A microwave plasma processing apparatus characterized in that the microwave transmission window is composed of a plurality of windows having an interval of λg/4 (λg: tube wavelength).