JPH065553A - Plasma treatment device - Google Patents

Abstract

PURPOSE:To restrain local electric field concentration when arranging a gas injector in a plasma generation region. CONSTITUTION:A reaction tube 1 of double structure which consists of an outer tube 1a and an inner tube 1b provided with a gas flow-in hole T is used and a pair of plasma generating electrodes 5, 6 are arranged in an outer peripheral surface of the outer tube 1a through a center of the outer tube 1a. A cross sectional contour of each of the electrodes 5, 6 are formed to an arc and both the electrodes 5, 6 are divided into two electrodes 5a, 5b and 6a, 6b, respectively with a space S therebetween from a center along circumferential direction of the outer tube 1a. An injector 8 wherein a number of gas injection holes are arranged in a length direction of the reaction tube 1 is provided at an opposite position of the space S between the outer tube 1a and the inner tube 1b.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a plasma processing apparatus.

[0002]

As is well known, active species such as ions, complex ions and radicals are present in plasma obtained by discharging a certain type of gas. The surface treatment of a semiconductor wafer may be mentioned. The plasma treatment is used for etching and forming various films in the semiconductor wafer manufacturing process because of the high-precision process control and the like.

The plasma processing includes anisotropic etching having a processing direction and various other processings. Among them, as an apparatus for performing isotropic etching having no processing direction and ashing of a resist film. For example, there is known a device in which an electrode is opposed to a gas introduction port in the upper part of a reaction tube and a high-frequency voltage is applied between the electrodes to introduce the generated plasma into a processing region.

Further, isotropic etching is used not only for removing semiconductor wafers, but also for removing an adhered film such as polysilicon adhered to the inner wall of a reaction tube after a CVD process. As described in Japanese Patent Publication No. 196820, a pair of electrodes each having a circular cross section along the circumferential direction of the reaction tube are opposed to each other on the outer side of the reaction tube through the center of the reaction tube. The processing gas is introduced into the reaction tube to generate plasma therein, and the plasma is used to clean the reaction tube.

[0005]

By the way, the present inventors have made the reaction tube a double structure and have a large number of gas injection holes in order to uniformly perform isotropic etching and ashing on a large number of wafers. We are investigating a configuration in which the injectors arranged along the length direction of the reaction tube are installed between the inner cylinder and the outer cylinder.

In this type of plasma processing, there are cases where the processing is performed only by radicals. When using the injector for such processing, for example, if the electrode structure of the above publication is used, FIG. As shown, the inner cylinder 1 is placed at a position facing the pair of electrodes 13a and 13b.
It is a good idea to arrange the injector 10 between the outer cylinder 1 and the outer cylinder 12 and to form the gas inflow holes 14 between both ends of the electrodes 13a and 13b in the inner cylinder 11, respectively. Because the gas injected from the injector 10 is exposed to the electric field for a long time by increasing the distance between the injector 10 and the gas inflow hole 14, the gas effectively becomes plasma, and at the same time, a large amount of radicals are generated. Is.

However, since the injector 10 has a large number of gas injection holes along the length direction of the reaction tube,
If the above-mentioned configuration is adopted, the electric field is concentrated in the gas injection hole and the portion is heated, and therefore, for example, the injector 10 is used.
Even if it is made of quartz, there is a risk that the temperature will be locally high and the contaminants will be scattered from the quartz. Further, since the plasma state in the lengthwise direction of the injector changes, there is a problem in that the surface to wafer uniformity of the wafer is deteriorated.

The present invention has been made under such a background, and an object thereof is a plasma processing apparatus capable of suppressing local electric field concentration when arranging a gas injection pipe or the like in a plasma generation region. To provide.

[0009]

According to a first aspect of the present invention, there is provided a reaction tube for processing an object to be processed with plasma, and an electrode pair for plasma generation arranged along each tube wall of the reaction tube. In the provided plasma processing apparatus, one and / or the other electrode of the electrode pair is divided in the circumferential direction of the reaction tube via a gap.

According to a second aspect of the present invention, in the first aspect of the invention, the gas injection pipe in which a plurality of gas injection holes are arranged along the longitudinal direction of the reaction pipe is opposed to the gap formed by dividing the electrode. It is characterized in that it is provided in the area.

[0011]

For example, in the case where the gas injection pipe is provided as in claim 2, when a predetermined high frequency voltage is applied between the electrodes, the processing gas injected from the gas injection hole of the gas injection pipe is discharged by the electric field and becomes plasma, The object to be processed is etched, for example. Here, since one electrode and / or the other electrode is divided in the circumferential direction of the reaction tube, the electric field is weak in the region facing the gap formed by the division, and therefore the degree of electric field concentration in the gas injection hole is reduced. Since it is small, local heating of the gas injection pipe is suppressed, and the plasma state in the length direction becomes uniform.

[0012]

FIG. 1 is a diagram showing an example of a plasma processing apparatus used in an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a reaction tube. The reaction tube 1 includes an outer cylinder 1a made of, for example, quartz, and an inner cylinder 1b made of, for example, quartz arranged concentrically in the outer cylinder 1a with a gap therebetween. It is configured.

The outer cylinder 1a and the inner cylinder 1b are respectively held at their lower ends by a cylindrical manifold 2 made of stainless steel or the like, and the manifold 2 is not shown in the drawings.
The O-ring 1c is fixed between the manifold 2 and the lower end of the outer cylinder 1a while being fixed in a state of being held on a plate (base). There is.
A disc-shaped cap portion 2a made of stainless steel or the like is openably and closably provided in an opening at a lower end portion of the manifold 2, and a substantially central portion of the cap portion 2a is driven by a rotation mechanism (not shown). The rotary shaft 2b is inserted in an airtight state by, for example, a magnetic seal, and the turntable 3 is fixed to the upper end of the rotary shaft 2b.

On the upper surface of the turntable 3, a heat retaining tube 3a made of quartz is installed. On the heat retaining tube 3a, for example, 25 or 50 semiconductor wafers W are each placed in a substantially horizontal state. And a predetermined gap between them, for example 4.76 mm
A wafer boat 4 made of quartz, which is stacked and accommodated at intervals, is mounted. The wafer boat 4 is configured to hold the peripheral edge portion of each wafer at, for example, four positions along the circumferential direction, and is integrated with the heat insulating cylinder 3a of the cap portion 2a and the like by a transport mechanism (not shown) to form a reaction tube. It is carried in and out in 1.

An exhaust passage 2c for discharging the processing gas in the reaction tube 1 to set the inside of the reaction tube 1 to a predetermined reduced pressure atmosphere is connected to the side surface of the manifold 2.

On the outer peripheral surface of the outer cylinder 1a, as shown in FIGS. 1 to 3, an electrode 5 connected to a high frequency power source E and a grounded electrode 6 are opposed to each other via the center of the outer cylinder 1a. The pair of electrodes 5 and 6 constitute a pair of electrodes for plasma generation. The electrodes 5 and 6 are made of, for example, aluminum, and
Each of the cross-sectional shapes is formed in an arc shape along the outer peripheral surface of the outer cylinder 1a, and the upper and lower ends are located corresponding to the height levels of the upper and lower ends of the wafer boat 4, respectively. As shown in FIG. 4, the electrodes 5 and 6 are positioned so that the crossing angle θ of the diagonal lines connecting the ends of the electrodes 5 and 6 is, for example, 135 degrees. Is also divided into two electrodes 5a, 5b (6a, 6b) from the center along the circumferential direction of the outer cylinder 1a with a gap S therebetween.

A large number of gas inflow holes T are formed in the vertical direction in the inner cylinder 1b, for example, at an intermediate position between the electrodes 5 and 6, and further in a position facing the arrangement region of the gas inflow holes T. A cover body (hereinafter referred to as an "etch tunnel") 7 made of a material such as aluminum, which is a conductive cylinder having a large number of active species introduction control holes 7a formed therein, covers the outer peripheral surface of the inner cylinder 1b. It is provided. However, the positions of the gas inflow hole T and the introduction hole 7a are not limited to the above-mentioned regions.

Between the outer cylinder 1a and the inner cylinder 1b, gas injection pipes (positions facing the gap S, which is the divided region of the electrode 5, and the gap S, which is the divided region of the electrode 6, respectively. Hereinafter, “injectors”) 8 are vertically arranged, that is, arranged along the length direction of the reaction tube 1. This injector 8
Has a gas injection hole 8a for injecting the processing gas toward the inner cylinder 1b in a region corresponding to the upper and lower ends of the wafer boat 4 with a predetermined gap in the vertical direction. The lower end side of the injector 8 is bent in an L shape to penetrate the side wall of the manifold 2 in an airtight manner, and is connected to a gas supply source (not shown) of a processing gas such as Freon (CF4) gas or oxygen gas. . In FIG. 1, for convenience, the injector 8, the gas inflow hole T of the inner cylinder 1b, and the introduction hole 7a of the etch tunnel 7 are shown in a line.

Next, an example of plasma processing using the above-mentioned apparatus will be described. FIG. 5A is a schematic view of the surface of a semiconductor wafer W as an object to be plasma-processed by the above-mentioned apparatus. In this wafer W, a silicon oxide film having a pattern on a polysilicon film 91. 92 is laminated, and a resist film 93 is further formed on the surface of the silicon oxide film 92.
And a damaged portion 94 due to impact of directional ions during etching is formed.

Then, the wafer boat 4 accommodating 25 or 50 such semiconductor wafers W is loaded into the reaction tube 1 by a transfer mechanism (not shown). Subsequently, the inside of the reaction tube 1 is evacuated to a predetermined degree of vacuum by a vacuum pump or the like connected to the exhaust passage 2c, and then a processing gas composed of a mixed gas of CFC gas and oxygen gas is introduced into the injector 8 to inject it. Of the gas is discharged from the gas outflow hole 8a, and the inside of the reaction tube 1 is evacuated while controlling the pressure so as to have a predetermined pressure. A voltage is applied to generate plasma of the mixed gas.

Fluorine radicals and oxygen radicals in the plasma pass through the etch tunnel 7 and further into the inner cylinder 1b through the gas inflow hole T to reach the damaged portion 94 of the semiconductor wafer W (see FIG. 5A). On the other hand, isotropic etching is performed to remove the damaged portion 94 as shown in FIG.

According to such an embodiment, when a high frequency voltage is applied between the electrodes 5 and 6, the processing gas is discharged and plasma is generated as shown by the dotted line in FIG. 2, but the injector 8 has electrodes 5 and 6. Are located in the regions facing the gap S, which is each of the divided regions, and the electric field is weak in the regions, so the electric field concentration in the gas injection holes 8a of the injector 8 is weak, and therefore local heating is suppressed. As a result, scattering of pollutants is suppressed, and the plasma state in the length direction of the injector 8 becomes uniform. The backside etching of the wafer and the ashing of the resist film may be performed using the above-mentioned apparatus.

In the above description, the number of injectors 8 may be one, and in this case, only one electrode 2 (3) of the electrodes 2 and 3 may be divided. Further, when the electrode 2 (3) is divided, instead of dividing it into two as in the embodiment, it is divided into three or more, and the injector 8 is placed at a position facing each gap.
May be arranged.

Further, according to the present invention, the processing gas is supplied from the upper portion of the reaction tube 1 without using the injector 8, and the introduction hole 7a of the etching tunnel 7 and the gas inflow hole T of the inner cylinder 1b are introduced.
May be formed only at the position facing the gap in the electrodes 2 and 3, in which case the electric field concentration is suppressed in the introduction hole 7a and the gas inflow hole T. Further, the object to be processed is not limited to a semiconductor wafer, but may be an LCD substrate or the like.

[0025]

According to the present invention, since one electrode and / or the other electrode of the electrode pair for plasma generation is divided in the circumferential direction of the reaction tube, the electric field is weak in the region facing the gap, Therefore, if a gas injection pipe having gas injection holes is arranged in this region, electric field concentration can be suppressed, local heating can be suppressed, and scattering of pollutants can be prevented and plasma can be made uniform.

[Brief description of drawings]

FIG. 1 is a vertical sectional side view showing an embodiment of the present invention.

FIG. 2 is a cross-sectional plan view showing a main part of the embodiment of the present invention.

FIG. 3 is a perspective view showing a main part of an embodiment of the present invention.

FIG. 4 is a plan view showing an example of the structure of an electrode pair for plasma generation.

FIG. 5 is an explanatory diagram showing an example of a semiconductor wafer.

FIG. 6 is a plan view showing a conventional example of a plasma processing apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reaction tube 2 Manifold 4 Wafer boat 5, 5a, 5b, 6, 6a, 6b Electrode 7 Cover body (etch tunnel) 7a Introduction hole 8 Gas injection pipe (injector) 8a Gas injection hole S Gap

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor, Hisashi Kato 2-3-1, Nishi-Shinjuku, Shinjuku-ku, Tokyo Inside Tokyo Electron Co., Ltd. (72) Inventor, Junichi Kakizaki 1-24-1, Shiroyama-machi, Tsukui-gun, Kanagawa Prefecture No. Tokyo Electron Sagami Co., Ltd. (72) Inventor, Koji Aoki 1-24-2, Machiya, Shiroyama-cho, Tsukui-gun, Kanagawa Prefecture No. 41, Tokyo Electron Sagami Co., Ltd. (72) Inventor Haruki Mori, Komukai Toshiba, Kawasaki, Kanagawa No. 1 town, Toshiba Research Institute, Inc. (72) Inventor Tatsuo Shiogetsu No. 1, Komukai Toshiba town, Kouki-ku, Kawasaki-shi, Kanagawa No. 1, Toshiba Research Institute, Inc.

Claims (2)

[Claims] 1. A plasma processing apparatus comprising: a reaction tube for processing an object to be processed with plasma; and a plasma-generating electrode pair arranged along a tube wall of the reaction tube. A plasma processing apparatus in which one and / or the other electrode is divided in the circumferential direction of a reaction tube with a gap. 2. The plasma processing according to claim 1, wherein a gas injection tube having a plurality of gas injection holes arranged along the longitudinal direction of the reaction tube is provided in a region facing a gap formed by dividing the electrode. apparatus.