JP2000357600A - Plasma treatment device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plasma treatment device capable of controlling a self-bias potential of an electrode without using any high frequency power source which is expensive and occupies a space. SOLUTION: A cathode 3, an anode 4 and a ring electrode 5 are arranged in such a manner as to expose to the inside of a reactor chamber 2. In the state in which treatment gas is introduced into the reactor chamber 2, high frequency electric power is applied between the cathode 3 and the ring electrode 5, and the anode 4, thereby generating plasma inside the reactor chamber 2. A plasma CVD treatment device subjects the surface of a substrate W placed on the anode 4 to a predetermined process by using the resultant plasma. High frequency oscillators 21, 23 for applying high frequency electric power are connected to the cathode 3 and the ring electrode 5, respectively. Furthermore, a matching circuit 30 consisting of a coil and a capacitor for varying the impedance of the anode 4 to thus control a self-bias potential of the anode 4 is connected to the anode 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma processing apparatus for forming a thin film or etching a thin film on a silicon substrate or a glass substrate.

[0002]

2. Description of the Related Art A plasma CVD apparatus is one type of plasma processing apparatus for performing a predetermined process on a substrate using plasma. FIG. 4 shows an example of a plasma CVD apparatus.

[0003] In FIG. 4, reference numeral 1 denotes a vacuum vessel, and the inside thereof is a reaction chamber 2. A disk-shaped cathode electrode 3 is provided on the upper wall of the vacuum vessel 1 with an insulating material 8 interposed therebetween. At the inner bottom of the reaction chamber 2, a disk-shaped anode electrode 4 also serving as a substrate mounting table is provided. The anode electrode 4 includes a shaft 10 supporting the anode electrode 4 and the vacuum vessel 1.
It is held in an insulated state by interposing an insulating material 9 between the two. The cathode electrode 3 and the anode electrode 4 are vertically opposed to each other, and a substrate W to be processed is placed on the upper surface of the anode electrode 4.

[0004] The space between the anode electrode 3 and the cathode electrode 4 is a plasma generation region. A ring electrode 5 is provided on the peripheral wall of the vacuum vessel 1 so as to surround the plasma generation region. Are arranged through. High-frequency oscillators 21, 25, and 23 are connected to the cathode electrode 3, the anode electrode 4, and the ring electrode 5 via phase matching units 22, 26, and 24, respectively.

A gas inlet 18 for supplying a processing gas toward the substrate W on the anode electrode 4 is provided at the center of the cathode electrode 3 located above the reaction chamber 2. Is provided with an exhaust port 19 for exhausting the atmospheric gas in the reaction chamber 2. The gas inlet 18 is connected to a gas supply system (not shown), and the exhaust port 19 is connected to an exhaust pump (not shown).

The gas used for substrate processing is Si
H ₄ , Si (OC ₂ H ₅ ) ₄ , NH ₃ , NF ₃ , C
_{2 F 6, O 2, Ar} , He, 1 kind of gas selected from among the gases N _2, N ₂ O, or a mixture of two or more gases are utilized.

Next, the flow of substrate processing will be described. First, the substrate W is transferred onto the anode electrode 4 in the reaction chamber 2 by a substrate transfer means (not shown), and the inside of the reaction chamber 2 is evacuated using an exhaust pump (not shown). Next, the substrate W is heated to a temperature suitable for the processing by a heating means (not shown). After heating, a processing gas is supplied into the reaction chamber 2 from the gas inlet 18. At the same time, high-frequency power is supplied from the high-frequency oscillators 21, 25, and 23 to the cathode electrode 3, the anode electrode 4,
The plasma is applied to the ring electrode 5 to generate plasma in the reaction chamber 2, and a thin film is formed on the surface of the substrate W using the plasma.

As described above, in the conventional apparatus, as a method of controlling the self-bias potential _Vdc of the anode electrode 4, a method of controlling the high-frequency power applied to the anode electrode 4 is used. Voltage amplitude _Vpp when high-frequency power is applied to anode electrode 4 and self-bias potential V of anode electrode 4
The relationship of _dc is as shown in FIG. This self-bias potential V
_dc is proportional to the magnitude of the high frequency power applied to the anode electrode 4, as shown in FIG. Therefore, the control of the self-bias potential _Vdc can be performed by controlling the high-frequency power.

[0009]

As described above, in the conventional device, the self-bias potential of the anode electrode 4 is controlled by controlling the high-frequency power applied to the anode electrode 4. There was a problem. (1) An extra expensive high-frequency power supply is required. (2) The high-frequency power supply mainly includes a high-frequency oscillator and a phase matching device. However, since the external dimensions thereof are large, if an extra high-frequency power supply is prepared for controlling the self-bias potential of the anode electrode, the installation area is increased. Is difficult to secure. (3) When the high-frequency power supply is remotely controlled, another expensive control circuit is required, which further increases the cost. (4) When a high power is applied, the plasma potential may be adversely affected.

According to the present invention, in consideration of the above circumstances, it is possible to control the self-bias potential of the electrode without using a high-frequency power supply which is expensive and takes up space for installation. An object of the present invention is to provide a plasma processing apparatus which does not require a circuit and does not adversely affect a plasma potential.

[0011]

According to a first aspect of the present invention, two electrodes are disposed facing a reaction chamber, and high-frequency power is applied between the two electrodes while a processing gas is introduced into the reaction chamber. In the plasma processing apparatus that generates a plasma in the reaction chamber and performs a predetermined process on the substrate disposed on one of the electrodes by using the plasma, one of the two electrodes is used. And a self-bias potential control circuit that controls the self-bias potential of the electrode by changing the impedance of the electrode while connecting a high-frequency power application circuit that applies high-frequency power to the electrode. It is characterized by being connected.

In the plasma processing apparatus of the present invention, high-frequency power is applied to one electrode, but no high-frequency power is applied to the other electrode, and only the impedance of the electrode is controlled to control the self-bias potential of the electrode. The structure is simple and takes up little space. Therefore, a circuit for controlling the self-bias potential of the electrode by changing the impedance can be constituted by a circuit including at least one of a coil and a capacitor. Further, since the circuit can be formed by such simple elements as the coil and the capacitor, the impedance control by remote operation can be easily performed, and there is no possibility that the plasma potential is adversely affected.

According to a third aspect of the present invention, there is provided a plasma processing apparatus further comprising a detecting means for detecting a self-bias potential of the other electrode, and a means for detecting a difference between the self-bias potential detected by the detecting means and a target self-bias potential. A means for feedback-controlling the self-bias potential control circuit so as to reduce the difference is provided.

In this plasma processing means, since the self-bias potential of the electrode is feedback-controlled, the self-bias potential can be accurately controlled.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a plasma CVD apparatus as an embodiment of the present invention. As shown in FIG. 4, this plasma CVD apparatus has a cathode electrode 3 on the upper part of the reaction chamber 2, an anode electrode 4 on the inner bottom of the reaction chamber 2, and a ring electrode 5 on the peripheral wall of the reaction chamber 2. Have.

As shown in FIG.
Similarly to the above device, a high-frequency power supply device (high-frequency power application circuit) including phase matching devices 22 and 24 and high-frequency oscillators 21 and 23 is connected, and desired high-frequency power can be applied to the cathode electrode 3 and the ring electrode 5. It has become. However, a high-frequency power supply device is not connected to the anode electrode 4, and instead, a matching circuit (self-bias potential control circuit) 30 that controls the self-bias potential of the electrode 4 by changing the impedance of the anode electrode 4. Is connected. The other configuration is the same as that of the apparatus of FIG. 4, and therefore, the same elements are denoted by the same reference numerals and description thereof will be omitted.

As shown in FIG. 2, the matching circuit 30 in this case includes one coil L and two variable capacitors C1 and C1.
2 is used. Two variable capacitors C
1 and C2 are connected in parallel between the anode electrode 4 and the ground E, and the coil L is connected in series to one variable capacitor C1.

As described above, the two variable capacitors C1, C
By forming the matching circuit 30 with two and one coil L, for example, the inductance value (L) of the coil L is fixed, and the capacitance values (C1, C2) of the two variable capacitors C1, C2 are changed. By doing so, a desired self-bias potential can be applied to the anode electrode 4.

FIG. 2 shows a schematic equivalent circuit in the reaction chamber 2. Here, it is assumed that the high-frequency power is applied only to the ring electrode 5 for the sake of simplicity. Assuming that the impedance of the front surface of the ring electrode 5, the front surface of the wall of the reaction chamber 2, and the front surface of the anode electrode 4 are Zr, Ze, Za, the impedance of the anode electrode 4 is Zb, and the impedance of the matching circuit 30 is Zx, respectively. Is expressed by the following equation.

Z = Zr + {Ze (Zb + Zx)} / {Z
e + (Zb + Zx)｝

Here, Zx = (1−ω ₂ C1L) / (jωC1 + jωC2-j
ω ₃ C1C2L), it can be understood from the above equation that the impedance Z in the reaction chamber 2 can be controlled by the values of the coil L of the matching circuit 30 and the capacitors C1 and C2.

In FIG. 2, V1 denotes a ring electrode 5
Vr is the voltage of the ring electrode 5 and Vr
b is the voltage of the anode electrode 4, Vs is the plasma voltage, i1
To i4 are currents, C1 to C6 are capacitors, L is a coil,
E indicates ground.

FIG. 3 shows the equivalent circuit shown in FIG.
9 illustrates the result of examining the dependency of the self-bias voltage of the anode electrode 4 when the capacitance value (C1) of the capacitor C1 is changed.

As shown in this figure, when the capacitance of the capacitor C1 changes, the self-bias potential of the anode electrode 4 changes. For example, when the self-bias potential of the anode electrode 4 is -160 V, the capacitance of the capacitor C1 may be 200 PF.

Thus, the coil L and the capacitor C1,
By changing the impedance of the matching circuit 30 composed of C2, the self-bias potential of the anode electrode 4 can be controlled, so that it can be constructed at a lower cost than when using a conventional high-frequency power supply. In addition, the structure can be simplified, and there is no need to secure an extra installation place. Also, when controlling the impedance remotely,
For example, since it is sufficient to change only the capacitance of the capacitor, there is no need to provide an expensive control circuit. Further, since high-frequency power is not applied to the anode electrode 4, there is no possibility that the plasma potential is adversely affected even at high power.

A detecting means for detecting the self-bias potential of the anode electrode 4 is added, and the matching circuit 30 is designed to reduce the difference between the self-bias potential detected by the detecting means and the target self-bias potential. If means for feedback controlling the impedance is provided, more accurate self-bias potential control can be realized.

In the above embodiment, the plasma CVD
Although the case of the apparatus has been described, the present invention can be applied to other types of plasma processing apparatuses.

[0028]

As described above, according to the present invention,
High-frequency power is applied to one electrode, but no high-frequency power is applied to the other electrode, and only the impedance of the electrode is changed to control the self-bias potential of the electrode. The circuit that controls
Instead of a large-scale device such as a high-frequency power supply device, it can be constituted by a simple high-frequency circuit using a coil and a capacitor. Therefore, the cost can be reduced, and the installation area can be easily secured because the extra high frequency power supply device can be omitted. In addition, since a circuit can be formed by such simple elements as a coil and a capacitor, impedance control by remote operation can be easily performed, and there is no possibility of adversely affecting the plasma potential even at high power.

Further, when the self-bias potential of the electrode is detected by the detecting means, and the impedance is feedback-controlled based on the detected value, more accurate self-bias potential control becomes possible.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a plasma CVD apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing a schematic equivalent circuit in a reaction chamber of the apparatus.

FIG. 3 is a characteristic diagram showing a dependency of a self-bias potential of an anode electrode on a change in capacitance of a capacitor C1 in the equivalent circuit.

FIG. 4 is a schematic configuration diagram of a conventional plasma CVD apparatus.

FIG. 5 is a characteristic diagram showing a relationship between a voltage amplitude V _pp and a self-bias potential V _dc of the anode electrode when high-frequency power is applied to the anode electrode in a conventional device.

FIG. 6 is a characteristic diagram showing a relationship between applied power and self-bias potential when high-frequency power is applied to an anode electrode in a conventional device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vacuum container 2 Reaction chamber 3 Cathode electrode 4 Anode electrode 5 Ring electrode 21, 23 High frequency oscillator (High frequency power application circuit) 22, 24 Phase matching device (High frequency power application circuit) 30 Matching circuit (Self bias potential control circuit) W substrate C1, C2 Capacitor L coil

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 21/3065 H01L 21/31 C 21/31 21/302 C F term (Reference) 4K030 CA04 CA06 FA03 KA20 KA30 KA39 KA41 KA45 4K057 DA20 DD01 DM40 DN01 5F004 AA16 BC08 BD04 5F045 AA08 AC01 AC12 BB08 DP03

Claims (3)

[Claims] 1. Two electrodes are arranged so as to face a reaction chamber, and the two electrodes are placed in a state where a processing gas is introduced into the reaction chamber.
A plasma processing apparatus that generates a plasma in the reaction chamber by applying high-frequency power between the two electrodes and uses the plasma to perform a predetermined process on a substrate disposed on one of the electrodes; A high-frequency power application circuit for applying high-frequency power to the one electrode is connected to one of the two electrodes, and the other electrode has a self-bias potential by changing the impedance of the electrode. A plasma processing apparatus to which a self-bias potential control circuit for controlling is connected. 2. The plasma processing apparatus according to claim 1, wherein the self-bias potential control circuit includes at least one of a coil and a capacitor for changing the impedance. 3. A detecting means for detecting a self-bias potential of said other electrode, and said self-bias potential is reduced so as to reduce a difference between the self-bias potential detected by said detecting means and a target self-bias potential. 3. The plasma processing apparatus according to claim 1, further comprising means for feedback-controlling the control circuit.