JPH11149996A - Plasma reactor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plasma reactor capable of compensating the output loss in a transmission line caused by reflecting wave power from a reaction container, and stably generating strong plasma. SOLUTION: A plasma reactor has a cylindrical reaction container to which gas for plasma is supplied; an outside electrode 2 arranged in the outer circumference of the reaction container; a metal cylinder arranged on the inside of the reaction container; and a high frequency power source for supplying high frequency power to the outside electrode 2 through a matching circuit for impedance control, and treatment such as etching or ashing is conducted to a semiconductor substrate with plasma generated. When plasma is generated, an output control means attached to the high frequency power source B detects reflecting wave power from the outside electrode 2 side with a reflecting power meter B4, and adds to output power equivalent to the reflecting wave power to an output circuit B2 with a controller B1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma reactor, and more particularly, to a reduction in effective load power due to a reflected wave power from a reaction vessel, thereby reducing the magnitude of the reflected wave power. The present invention relates to a plasma reactor that can always transmit a predetermined power to a load including a matching circuit and can stably generate plasma.

[0002]

2. Description of the Related Art A plasma reactor is configured to be capable of reducing pressure and has a cylindrical reaction vessel to which a gas for plasma is supplied, an external electrode disposed on the outer periphery of the reaction vessel, and the reaction chamber coaxially with the external electrode. The apparatus includes a metal cylinder disposed inside the container, and supplies high-frequency power to generate plasma between the external electrode and the metal cylinder. In such an apparatus, a metal cylinder is used as an internal electrode or as an etch tunnel, and a semiconductor substrate or the like loaded inside the metal cylinder is subjected to dry processing such as etching, ashing, and CVD.

A predetermined high-frequency power is supplied to the external electrodes from a high-frequency power supply via a matching circuit for adjusting a variation in impedance due to capacitive coupling or inductive coupling between the generated plasma and the external electrodes. Is done. Further, as a matching circuit, a fixed impedance type matching circuit is often used from the viewpoint of operational stability.

[0004]

By the way, in a conventional plasma reactor, when plasma is generated,
The load of the plasma generation circuit on the reaction vessel side, that is, the circuit including the external electrode and the metal cylinder is not a pure resistance, and
Since the state of the plasma also fluctuates constantly, perfect matching cannot be obtained only with the matching circuit, and in the transmission line from the high-frequency power supply to the external electrode, the effective load power decreases due to the reflected wave power. In particular, when a fixed impedance type matching circuit is provided, the amount of impedance mismatch between the high-frequency power supply and the plasma generation circuit increases, so that the power of the reflected wave may increase significantly. As a result, in the plasma reactor, there is a problem that the power input to the plasma cannot be sufficiently increased.

[0005] The present invention has been made based on the above findings, and an object of the present invention is to reduce the effective load power due to the reflected wave power from the reaction vessel, and to stably generate plasma. It is to provide a reactor.

[0006]

In order to solve the above-mentioned problems, a plasma reactor according to the present invention has a cylindrical reaction vessel which is configured to be capable of reducing pressure and is supplied with a plasma gas, and has an outer periphery provided around the reaction vessel. An external electrode disposed, a metal cylinder disposed coaxially with the external electrode inside the reaction vessel, and a high-frequency power supply that supplies high-frequency power to the external electrode via a matching circuit for impedance adjustment. In the plasma reactor provided, the high-frequency power supply is provided with output adjusting means for detecting reflected wave power from the external electrode side when plasma is generated and for adding and outputting power equivalent to the reflected wave power. It is characterized by having.

That is, in the above-mentioned plasma reactor, the specific output adjusting means attached to the high-frequency power supply detects the reflected wave power from the reaction vessel side as the plasma is generated, and is supplied from the high-frequency power supply to the external electrodes. A power equivalent to the reflected wave power is added to the power and output, thereby compensating for a decrease in the effective load power due to the reflected wave power.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration example of a high-frequency power supply and an output adjusting unit in the plasma reactor of the present invention. FIG. 2 is a partially broken side view showing one embodiment of the reactor body in the plasma reactor of the present invention. Hereinafter, in the description of the embodiment, the plasma reactor is simply abbreviated as “reactor”.

[0009] The reactor of the present invention, as shown in FIG.
It mainly comprises a reactor body (A) as a mechanical structure, a high-frequency power supply (B) as a power supply circuit, and a matching circuit (C). Then, as shown in FIG. 2, the reactor main body (A) is configured to be capable of reducing pressure and has a cylindrical reaction vessel (1) to which a plasma gas is supplied.
An external electrode (2) disposed on the outer periphery of the reaction vessel; and a reaction vessel (1) coaxially provided with a predetermined distance from the external electrode.
And a metal cylindrical body (4) arranged inside.

The reactor may be either a coaxial feed type or a counter electrode type using an etch tunnel. The coaxial feed type reactor is a reactor of a type in which a metal cylindrical body (4) is used as an internal electrode by grounding it, while a counter electrode type reactor is that a metal cylindrical body (4) is grounded. Instead, it is a reactor that is used as an etch tunnel.

The reaction vessel (1) is usually formed of quartz glass and, for example, supports (9, 2) on a lower base (12).
At 9), it is vertically arranged on a gantry supporting the upper base (10) and the bottom plate (7). The upper end of the reaction vessel (1) has an upper lid (5) for radiating heat after the treatment.
It is sealed with a top plate (5) that can be opened and closed in 2). The top plate (5) is supported by four support rods (8, 8) erected on the bottom plate (7). These support rods (8) load the top plate (5) and the reaction vessel (1) generated when the top plate (5) and the bottom plate (7) are sucked when the inside of the reaction vessel (1) is evacuated. Supports the axial load of 1).

In the center of the bottom plate (7), a circular opening having a diameter such that a so-called wafer boat (16) for supporting a large number of wafers in multiple stages can pass therethrough is provided in the reaction vessel (1). The upper base (10) is provided with a circular opening which is coaxial with the opening and has a somewhat larger diameter. The circular opening of the bottom plate (7) is hermetically sealed by a lower lid (17) of a reaction vessel which has a flat convex vertical cross-sectional shape and can be moved up and down with a wafer boat (16) placed thereon. Is stopped.

The above-mentioned reaction vessel (1) has a gas introduction pipe (13) provided with a large number of gas ejection holes (not shown) along the longitudinal direction for introducing a plasma gas into the reaction vessel. Is inserted from above. Furthermore, a reaction vessel (1)
A gas exhaust pipe (15) provided with a number of gas suction holes (not shown) along the longitudinal direction is inserted from above, and the reaction vessel (1) is passed through the suction holes by the operation of a vacuum system. The inside is depressurized, and the reaction exhaust gas is exhausted outside the system.

The reaction vessel (1) is provided with a temperature control mechanism (3) comprising a heat source such as a far-infrared heater and a reflector for utilizing radiant heat in order to promote the reaction. In addition, as a temperature control mechanism, a heat source such as a ceramic heater which is not affected by plasma is disposed on the inner peripheral side of the metal cylindrical body (4).
A mechanism for heating the internal wafer from a shorter distance may be employed.

The external electrode (2) is formed in a cylindrical shape with an electrode material and dimensional specifications capable of applying a required voltage and current,
Usually, it is closely attached to the outer peripheral surface of the reaction vessel (1). Then, it is connected to a high frequency power supply (B) via a matching circuit (C) for impedance adjustment shown in FIG. Also,
As shown in FIG. 2, the metal cylinder (4) is made of a wafer boat (1) made of a surface-treated aluminum alloy or the like.
6) is formed to have a diameter capable of accommodating 6). Many small holes are uniformly arranged on the peripheral wall of the metal cylinder (4).

In the above power supply circuit section, generally,
The high-frequency power supply (B) is installed separately from the reactor body (A), and the matching circuit (C) is installed directly on the gantry or in the very vicinity of the gantry. As shown in FIG. 1, the high-frequency power source (B) supplies a high-frequency power of about 1 to 100 MHz to the reactor body (A), that is, the external electrode (2) through a matching circuit (C). A power supply that can supply about 5 KW is used.
Basically, the high-frequency power supply (B) includes a controller (B1) that includes a storage operation unit and regulates a frequency and an output, and an output circuit (B2) that includes a high-frequency oscillation circuit and a power amplifier. .

As is well known, the matching circuit (C) includes a plasma generation circuit based on capacitive coupling and inductive coupling of plasma generated in the reaction vessel (1), that is, an external electrode (2) and a metal cylindrical body (4). It is a network composed of an inductance, a capacitance, and the like for correcting the fluctuation of the impedance of the included circuit and matching the impedance of the high frequency power supply (B) with the impedance of the plasma generation circuit. , High frequency power supply (B). As the matching circuit (C), any of a variable impedance type that operates in response to a change in the impedance of the reaction vessel (1) and a fixed impedance type in which the internal impedance is set in advance may be used.

The most important feature of the present invention is that the output adjusting means for detecting the reflected wave power from the external electrode (2) side when the plasma is generated and for adding and outputting the same power as the reflected wave power is a high frequency power supply. (B). In the present invention, the output adjusting means may include an output circuit (B2)
A traveling wave power meter (B3) which detects the traveling wave power from the output circuit (B2) and feeds it back to the controller (B1), and which is disposed on the output side of the output circuit (B2); It comprises a reflected wave power meter (B4) that detects the reflected wave power to the output circuit (B2) side and feeds back the value to the controller (B1), and the above-described controller (B1).

Specifically, in the output adjusting means, the traveling wave power meter (B3) feeds back the detected traveling wave power to the controller (B1), and the reflected wave power meter (B4) detects the traveling wave power meter (B4). The reflected wave power is fed back to the controller (B1). Then, the controller (B1) outputs an output condition relating to the power set in advance through the operation panel and the traveling wave power meter (B1).
Based on the magnitude of the actual traveling wave power detected in 3) and the magnitude of the actual reflected wave power detected by the reflected wave power meter (B4), the magnitude of the traveling wave power and the magnitude of the reflected wave power are determined. The output circuit (B2) is controlled so that the difference becomes the set value stored in the controller (B1). That is, the controller (B1) adds the power value equivalent to the reflected wave power value fed back to the previous set value, and outputs the output circuit (B1) based on the added new set value.
It has a function to output to 2).

In the reactor of the present invention, a wafer to be subjected to plasma processing is mounted on a wafer boat (16) and loaded into a metal cylinder (4) through a circular opening of a bottom plate (7). . The inside of the reaction vessel (1) is depressurized to a predetermined degree of vacuum through a gas discharge pipe (15), and then the gas introduction pipe (1) is maintained while maintaining the aforementioned degree of vacuum.
The gas for plasma is supplied through 3). As the plasma gas, various material gases are used in accordance with the processing, as in the conventional case. For example, in the case of ashing processing,
Oxygen, hydrogen, argon, water, or the like is used. In the case of etching, fluorine, bromine, chlorine, or the like is used.

In the above-mentioned reactor, for example, 27.12 MHz from the high frequency power supply (B) to the external electrode (2).
When an electric power of 2 KW is supplied, an electric field is generated between the external electrode (2) and the metal cylinder (4). As a result, the supplied gas is turned into plasma in the reaction vessel (1), and The wafer is processed by radicals in the plasma mainly flowing into the metal cylinder (4).

In the above-described processing operation, when plasma is generated, the traveling wave power meter (B3) of the output adjusting means attached to the high frequency power supply (B) controls the traveling wave power in the transmission line reaching the external electrode (2). And outputs its magnitude to the controller (B1). Further, the power meter (B4) detects the reflected wave power generated in the transmission line to the output circuit (B2) side, and determines the magnitude of the reflected power.
Output to 1). Then, the controller (B1) adds the same power as the reflected wave power and outputs it as a new set value to the output circuit (B2). Therefore, the reactor of the present invention can compensate for a decrease in effective load power due to reflected wave power.

The initial reflected wave power generated in the transmission line varies depending on the type of plasma and the configuration of the plasma generating circuit, but is about 10 to 400 W when the initial power output is about 2 KW as described above. Of course, the value of the reflected wave power changes depending on the control of the output circuit (B2) by the controller (B1), but the output adjusting means continuously responds, and finally the output circuit (B2).
The output from can be brought as close as possible to the desired set value.

That is, since the reactor of the present invention can always supply the desired level of high-frequency power to the external electrode (2) reliably, the reactor between the external electrode (2) and the metal cylindrical body (4) can be supplied. Thus, plasma can be stably generated at a predetermined power, and as a result, more stable processing of the wafer can be realized. In the reactor of the present invention, the operation panel and controller (B1) of the high-frequency power supply (B) can be installed separately from the output circuit (B2).
4) can be installed separately from the high-frequency power supply (B) if it is the output side of the high-frequency power supply (B). In addition, the present invention can be similarly applied to a capacitively-coupled or inductively-coupled single-wafer type reactor using a high frequency, in addition to the batch-type reactor illustrated in FIG.

[0025]

As described above, according to the plasma reactor of the present invention, the desired level of high-frequency power can always be reliably supplied to the external electrode, so that the distance between the external electrode and the metal cylinder can be increased. Thus, plasma can be generated stably, and more stable processing of the wafer can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration example of a high-frequency power supply and an output adjusting unit.

FIG. 2 is a partially broken side view showing one embodiment of a reactor body.

[Explanation of symbols]

 1: reaction vessel 13: gas introduction pipe 15: gas discharge pipe 16: wafer boat 2: external electrode 4: metal cylinder A: reactor body B: high frequency power supply B1: controller B2: output circuit B3: traveling wave power meter B4 : Reflected wave power meter C: Matching circuit

──────────────────────────────────────────────────の Continued on front page (51) Int.Cl. ⁶ Identification code FI H01L 21/31 H01L 21/302 B

Claims (1)

[Claims] A cylindrical reaction vessel configured to be capable of reducing pressure and supplied with a plasma gas; an external electrode disposed on an outer periphery of the reaction vessel; and an inside of the reaction vessel coaxially with the external electrode. In a plasma reactor provided with a metal cylinder disposed and a high-frequency power supply for supplying high-frequency power to the external electrode via a matching circuit for impedance adjustment, the high-frequency power supply includes: A plasma reactor, further comprising output adjustment means for detecting reflected wave power from an external electrode side and adding and outputting power equivalent to the reflected wave power.