Plasma treatment device

The present invention relates to a plasma processing apparatus.

There is a plasma processing device that generates plasma by applying a high frequency wave between two electrodes and processes a substrate by the plasma. Such a plasma processing device can operate as a sputtering device or an etching device depending on the area ratio and / or bias of the two electrodes. The plasma processing device configured as a sputtering device has a first electrode for holding a target and a second electrode for holding a substrate, and a high frequency is applied between the first electrode and the second electrode to obtain a first electrode. Plasma is generated between the electrode and the second electrode (between the target and the substrate). The generation of plasma creates a self-bias voltage on the surface of the target, which causes ions to collide with the target and emit particles of the material that make it up from the target.

Patent Document 1 describes a plasma surface treatment apparatus including an equilibrium-unbalanced converter. This plasma surface treatment device includes a high-frequency power supply, a power amplifier, an impedance matcher, a coaxial cable, a vacuum vessel, a discharge gas mixing box, a non-grounded electrode, a grounded electrode, and a transformer-type balanced unbalanced transformer. And have. The discharge gas mixing box, non-grounded electrode, grounded electrode and transformer type equilibrium unbalanced converter are arranged in a vacuum vessel. The non-grounded electrode is installed in the vacuum vessel via an insulator support and a discharge gas mixing box. The ground electrode supports the substrate. Further, the ground electrode is electrically connected to the vacuum vessel. The output of the high frequency power supply is supplied between the non-grounded electrode and the grounded electrode via a power amplifier, an impedance matching box, a coaxial cable and a transformer type balanced unbalanced converter. According to Patent Document 1, the common mode current Ix flowing through the member of the vacuum vessel connected to the ground electrode is cut off by the transformer type equilibrium unbalanced converter.

In the plasma surface treatment apparatus described in Patent Document 1, since the ground electrode and the vacuum vessel are electrically connected, the vacuum vessel can function as an anode in addition to the ground electrode. The self-bias voltage may depend on the state of the part that can function as the cathode and the state of the part that can function as the anode. Therefore, when the vacuum vessel also functions as an anode in addition to the substrate holding electrode, the cell bias voltage may change depending on the state of the portion of the vacuum vessel that functions as the anode. Changes in the self-bias voltage result in changes in the plasma potential, and changes in the plasma potential can affect the processing of the substrate, for example, affecting the properties of the film to be formed.

When a film is formed on the substrate by a sputtering device, a film can also be formed on the inner surface of the vacuum vessel. This can change the state of the part of the vacuum vessel that can function as the anode. Therefore, if the sputtering apparatus is continuously used, the self-bias voltage may change due to the film formed on the inner surface of the vacuum vessel, and the plasma potential may also change. Therefore, conventionally, it has been difficult to maintain the characteristics of the film formed on the substrate constant when the sputtering apparatus is used for a long period of time.

Similarly, even when the etching apparatus is used for a long period of time, the self-bias voltage is changed by the film formed on the inner surface of the vacuum vessel, which can change the plasma potential, so that the etching characteristics of the substrate are kept constant. It was difficult to do.

<p><patcit num="1"><text>Japanese Unexamined Patent Publication No. 2009-302566</text></patcit></p>

The present invention has been made based on the above-mentioned problem recognition, and provides an advantageous technique for stabilizing the plasma potential in long-term use. One aspect of the present invention relates to a plasma processing apparatus, wherein the plasma processing apparatus includes a balun having a first input terminal, a second input terminal, a first output terminal and a second output terminal, a vacuum vessel, and the vacuum. A first electrode insulated from the container and electrically connected to the first output terminal and a second electrode insulated from the vacuum container and electrically connected to the second output terminal are provided. The second electrode is arranged so as to surround the first electrode over the entire circumference.

<figref num="1">The figure which shows typically the structure of the plasma processing apparatus of 1st Embodiment of this invention.</figref><figref num="2A">The figure which shows the structural example of a balun.</figref><figref num="2B">The figure which shows the other configuration example of a balun.</figref><figref num="3">The figure which shows typically the structure of the plasma processing apparatus of 2nd Embodiment of this invention.</figref>

Hereinafter, the present invention will be described through its exemplary embodiments with reference to the accompanying drawings.

FIG. 1 schematically shows the configuration of the plasma processing apparatus 1 according to the first embodiment of the present invention. The plasma processing apparatus 1 of the first embodiment can operate as a sputtering apparatus that forms a film on the substrate 112 by sputtering. The plasma processing apparatus 1 includes a balun (balanced / unbalanced conversion circuit) 103, a vacuum vessel 110, a first electrode 106, a second electrode 111, and a substrate holding portion 132. Alternatively, the plasma processing apparatus 1 is understood to include a balun 103 and a main body 10, and the main body 10 includes a vacuum container 110, a first electrode 106, a second electrode 111, and a substrate holding portion 132. You may. The main body 10 has a first terminal 251 and a second terminal 252. The first electrode 106 may be arranged in cooperation with the vacuum vessel 110 so as to separate the vacuum space and the external space (that is, to form a part of the vacuum partition wall), or the first electrode 106 of the vacuum vessel 110. It may be placed inside. The second electrode 111 may be arranged in cooperation with the vacuum vessel 110 so as to separate the vacuum space and the external space (that is, to form a part of the vacuum partition wall), or the second electrode 111 of the vacuum vessel 110. It may be placed inside.

The balun 103 has a first input terminal 201, a second input terminal 202, a first output terminal 211, and a second output terminal 212. An unbalanced circuit is connected to the first input terminal 201 and the second input terminal 202 of the balun 103, and a balanced circuit is connected to the first output terminal 211 and the second output terminal 212 of the balun 103. To. At least a portion of the vacuum vessel 110 may be composed of conductors. The vacuum vessel 110 may include a grounded portion. In one example, the conductors that make up at least a portion of the vacuum vessel 110 can be grounded, while in another example, the conductors that make up at least a portion of the vacuum vessel 110 are electrically connected to grounding via an inductor. sell. The first electrode 106 and the second electrode 111 are insulated from (a conductor forming at least a part of) the vacuum vessel 110. In the example shown in FIG. 1, the first electrode 106 and the second electrode 111 are insulated from (a conductor forming at least a part of) the vacuum vessel 110 by an insulator 131.

In the first embodiment, the first electrode 106 is the cathode and holds the target 109. The target 109 can be, for example, an insulator material or a conductor material. Further, in the first embodiment, the second electrode 111 is an anode. The first electrode 106 is electrically connected to the first output terminal 211, and the second electrode 111 is electrically connected to the second output terminal 212. The fact that the first electrode 106 and the first output terminal 211 are electrically connected means that the first electrode 106 and the first output terminal are connected so that a current flows between the first electrode 106 and the first output terminal 211. It means that a current path is configured between and the 211. Similarly, in this specification, the fact that a and b are electrically connected means that a current path is constructed between a and b so that a current flows between a and b. means.

In the above configuration, the first electrode 106 is electrically connected to the first terminal 251 and the second electrode 111 is electrically connected to the second terminal 252, and the first terminal 251 is electrically connected to the first output terminal 211. It can also be understood as a configuration in which the second terminal 252 is electrically connected to the second output terminal 212.

The first electrode 106 and the second electrode 111 are arranged so as to face the space on the side of the substrate holding portion 132 (the substrate 112 held by the substrate holding portion 132). The second electrode 111 may be arranged so as to surround the first electrode 106 over the entire circumference. The second electrode 111 may have, for example, a tubular shape. It is desirable that the first electrode 106 and the second electrode 111 have a coaxial structure. In one example, the first electrode 106 has a cylindrical shape centered on the virtual axis, and the second electrode 111 has a cylindrical shape centered on the virtual axis.

The configuration of the first electrode 106 and the second electrode 111 as described above is advantageous for reducing the impedance between the first electrode 106 and the second electrode 111, which is grounded from the output side of the balun 103. It is advantageous for reducing the current flowing through the current, that is, the common mode current. Reducing the common mode current means making it difficult for the vacuum vessel 110 to function as an anode. An unintended film may be formed on the inner wall of the vacuum vessel 110 due to the formation of a film on the substrate 112, but by making the vacuum vessel 110 an anode to make it difficult to function, the state of the inner wall of the vacuum vessel 110 is affected. The plasma potential can be desensitized. This is advantageous for stabilizing the plasma potential during long-term use of the plasma processing apparatus 1. From another point of view, the impedance between the first electrode 106 and the second electrode 111 is preferably smaller than the impedance between the first electrode 106 and the vacuum vessel 110. This is advantageous for reducing the above-mentioned common mode current.

The distance (the size of the gap) between the first electrode 106 and the second electrode 111 is preferably the Debye length or less. This is effective for suppressing plasma from entering the gap between the first electrode 106 and the second electrode 111.

The voltage appearing at the second electrode 111 may depend on the impedance between the second output terminal 212 and the second electrode 111. Therefore, it is desirable to shorten the electrical path length between the second output terminal 212 and the second electrode 111. Alternatively, it is desirable that the electric path connecting the first output terminal 211 and the first electrode 106 and the electric path connecting the second output terminal 212 and the second electrode 111 have a coaxial structure.

In the first embodiment, the first electrode 106 and the first output terminal 211 (first terminal 251) are electrically connected via the blocking capacitor 104. The blocking capacitor 104 cuts off the direct current flowing between the first output terminal 211 and the first electrode 106 (or between the first output terminal 211 and the second output terminal 212). Instead of providing the blocking capacitor 104, the impedance matching circuit 102 described later may be configured to cut off the direct current flowing between the first input terminal 201 and the second input terminal 202. Alternatively, the blocking capacitor 104 may be arranged in the electrical path between the second electrode 111 and the second output terminal 212.

The plasma processing apparatus 1 may further include a high frequency power supply 101 and an impedance matching circuit 102 arranged between the high frequency power supply 101 and the balun 103. The high frequency power supply 101 supplies high frequency (high frequency current, high frequency voltage, high frequency power) between the first input terminal 201 and the second input terminal 202 of the balun 103 via the impedance matching circuit 102. In other words, the high frequency power supply 101 supplies high frequency (high frequency current, high frequency voltage, high frequency power) between the first electrode 106 and the second electrode 111 via the impedance matching circuit 102, the balun 103, and the blocking capacitor 104. .. Alternatively, the high frequency power supply 101 can be understood as supplying a high frequency between the first terminal 251 and the second terminal 252 of the main body 10 via the impedance matching circuit 102 and the balun 103.

Gas (for example, Ar, Kr or Xe gas) is supplied to the internal space of the vacuum vessel 110 through a gas supply unit (not shown) provided in the vacuum vessel 110. Further, a high frequency is supplied between the first electrode 106 and the second electrode 111 by the high frequency power supply 101 via the impedance matching circuit 102, the balun 103, and the blocking capacitor 104. As a result, plasma is generated, a self-bias voltage is generated on the surface of the target 109, ions in the plasma collide with the surface of the target 109, and particles of the material constituting the target 109 are emitted from the target 109. Then, a film is formed on the substrate 112 by these particles.

FIG. 2A shows a configuration example of the balun 103. The balun 103 shown in FIG. 2A has a first coil 221 that connects the first input terminal 201 and the first output terminal 211, and a second coil 222 that connects the second input terminal 202 and the second output terminal 212. And have. The first coil 221 and the second coil 222 are coils having the same number of turns and share an iron core.

FIG. 2B shows another configuration example of the balun 103. The balun 103 shown in FIG. 2B has a first coil 221 that connects the first input terminal 201 and the first output terminal 211, and a second coil 222 that connects the second input terminal 202 and the second output terminal 212. And have. Further, the balun 103 shown in FIG. 2B shares the iron core with the first coil 221 and is magnetically coupled to the first coil 221 as the third coil 223, and shares the iron core with the second coil 222. It may have two coils 222 and a fourth coil 224 that is magnetically coupled. The first output terminal 211 and the second output terminal 212 are connected by a series circuit including the third coil 223 and the fourth coil 224. The first coil 221, the second coil 222, the third coil 223, and the fourth coil 224 are coils having the same number of turns and share an iron core.

FIG. 3 schematically shows the configuration of the plasma processing apparatus 1 according to the second embodiment of the present invention. Matters not described as the second embodiment may follow the first embodiment. The plasma processing apparatus 1 of the second embodiment can operate as an etching apparatus for etching the substrate 112. In the second embodiment, the first electrode 106 is a cathode and holds the substrate 112. Further, in the second embodiment, the second electrode 111 is an anode. At least a portion of the vacuum vessel 110 may be composed of conductors. The vacuum vessel 110 may include a grounded portion. In one example, the conductors that make up at least a portion of the vacuum vessel 110 can be grounded. In another example, the conductors that make up at least a portion of the vacuum vessel 110 may be electrically connected to ground via an inductor. The first electrode 106 and the second electrode 111 are insulated from (a conductor forming at least a part of) the vacuum vessel 110. In the example shown in FIG. 3, the first electrode 106 and the second electrode 111 are insulated from (a conductor forming at least a part of) the vacuum vessel 110 by an insulator 131.

In the plasma processing apparatus 1 of the second embodiment, the first electrode 106 and the first output terminal 211 can be electrically connected via the blocking capacitor 104. In other words, in the plasma processing apparatus 1 of the second embodiment, the blocking capacitor 104 may be arranged in the electrical connection path between the first electrode 106 and the first input terminal 211. Instead of providing the blocking capacitor 104, the impedance matching circuit 102 may be configured to block the direct current flowing between the first input terminal 201 and the second input terminal 202. Alternatively, the blocking capacitor 104 may be arranged between the second electrode 111 and the second output terminal 212.

The present invention is not limited to the above embodiments, and various modifications and modifications can be made without departing from the spirit and scope of the present invention. Therefore, in order to make the scope of the present invention public, the following claims are attached.

1: Plasma processing device, 10: Main body, 101: High frequency power supply, 102: Impedance matching circuit, 103: Balun, 104: Blocking capacitor, 106: First electrode, 107, 108: Insulator, 109: Target, 110: Vacuum Container, 111: 2nd electrode, 112: Substrate, 132: Substrate holder, 201: 1st input impedance terminal, 202: 2nd input terminal, 211: 1st output terminal, 212: 2nd output terminal, 251: 1st 1 terminal, 252: 2nd terminal, 221: 1st coil, 222: 2nd coil, 223: 3rd coil, 224: 4th coil,