JPH09260097A - Plasma generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plasma generating source which can control a plasma quantity in a reaction chamber and its distribution or activity of a gas component by combining a plasma generating method based on the new principle with a plasma generating method used so far. SOLUTION: In a plasma generator having a reaction chamber 10 to hold plasma, an electromagnetic wave generating source and an electromagnetic wave radiating part to radiate an electromagnetic wave generated by this electromagnetic wave generating source to the reaction chamber, it has one or plural electromagnetic wave generating sources, and at least two or more kinds of different electromagnetic wave radiating parts are combined with each other. In this case, a plasma generating coil 23 installed in a plasma generating part 11 connected to the reaction chamber 10 and an electrode 24 which exists in the reaction chamber 10 and supplies electric power to plasma, are used as a combination of the electromagnetic wave radiating part.

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 equipped with a plasma generator, and more particularly to a processing apparatus suitable for fine processing of semiconductor elements.

[0002]

2. Description of the Related Art In a dry etching apparatus or a chemical vapor deposition (CVD) apparatus using plasma, a discharge chamber is irradiated with electromagnetic waves such as microwaves and RF high frequencies to generate plasma. Then, the plasma decomposes, ionizes, or excites the molecular gas introduced into the discharge chamber to activate the molecular gas for etching or film formation. In order to perform etching with a good shape and film formation with a good film quality, the balance of the components of plasma and activated gas is important. Since such activation of gas is performed by plasma, what kind of activation occurs depends largely on what kind of plasma is generated. In other words, it is an important point how much the energy of the electromagnetic wave radiated into the discharge chamber and what kind of path it takes to lead to activation.

Typical conventional plasma generators are, for example, a RIE plasma device using parallel plate electrodes, a microwave ECR plasma device and an inductively coupled plasma device. These devices differ in the wavelength of electromagnetic waves used and the manner of coupling with plasma (ECR, capacitive coupling, inductive coupling), and gas activation unique to each device is performed.

Further, in a process using a wafer of 5 inches or more, it is an important issue to make the treatment process within the wafer uniform, so that the shapes of the electrodes and the coils are optimized, or the microwave radiation condition is optimized. As a result, the plasma distribution has been controlled to perform uniform processing.

[0005]

In the conventional plasma generator, since a single kind of electromagnetic wave source and a single kind of electromagnetic wave radiation part are used, activation peculiar to each plasma generation method is performed. Therefore, when a specific plasma source is used, the balance of gas components may not be optimal for the intended process. In addition, if the conditions of the wafer such as the line width of the wiring and the thickness and material of the protective film material are slightly changed, the optimum process condition may not be found with the plasma source. In the present invention, activation of different gases is mixed by combining two or more types of plasma generation methods that have been conventionally used or by combining a plasma generation method based on a new principle with a conventionally used plasma generation method. The purpose is to widen the adjustment range of gas components.

Furthermore, when a single type of electromagnetic wave radiation section is used, it is necessary to change the shape itself of the electromagnetic wave radiation section in order to control the plasma distribution, and it takes a great deal of time and cost to control the distribution over a wide range. And labor was needed. An object of the present invention is to expand the control range of plasma distribution by mixing two or more plasma generation methods and changing the intensity distribution of electromagnetic waves given to each plasma generation unit. Further, it is aimed to obtain a uniform distribution even in a large-area wafer of 5 inches or more by arranging the positions of these plasma generating parts on concentric circles.

[0007]

In order to achieve the above object, a reaction chamber for holding plasma, an electromagnetic wave generation source, and an electromagnetic wave emission section for emitting the electromagnetic wave generated by the electromagnetic wave generation source to the reaction chamber are provided. In a plasma generation device, one or a plurality of electromagnetic wave generation sources are provided, and at least two or more different electromagnetic wave emission units are combined.

In this case, as a combination of the electromagnetic wave radiating section, a plasma generating coil attached to a plasma generating section connected to the reaction chamber and an electrode in the reaction chamber for supplying electric power to the plasma are used. At this time, the electromagnetic wave emitting unit may be a combination of one or a plurality of plasma generating coils and one or a plurality of electrodes. The plasma generating coils or electrodes are arranged on concentric circles.

Electromagnetic waves can be applied to the electrodes in the reaction chamber for supplying electric power to the plasma. further,
DC potential can be applied to the electrodes, but at this time,
When the plasma potential is Vs and the plasma electron temperature is Te, the DC potential V generated at the electrodes is controlled so as to satisfy V> 19xTe + Vs.

When a plurality of coils are used, each coil has an impedance adjusting function, each coil is connected in parallel, and the output side of the electromagnetic wave generator that supplies the electromagnetic wave to each coil. It is configured to have an impedance matching mechanism.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. 1A and 1B are diagrams of a plasma generator showing an embodiment of the present invention, FIG. 1A is a sectional view of the plasma generator, and FIG. 1B is a plan view showing a positional relationship between a workpiece, a coil, and an electrode. .

Inside the reaction vessel 10, there is an electrode 32 on which an object to be treated 31 is placed, and an electromagnetic wave generator 20C is connected via a matching box 21C. In the opposite part of the object to be processed,
Plasma generation chamber with at least a part made of insulator
11 are connected and a coil 23 for plasma generation is arranged. A cylindrical electrode 24 is arranged in the reaction chamber 10. The coil 23 and the electrode 24 are arranged on a concentric circle whose axis is a vertical line passing through the center of the surface of the workpiece 31 to be processed. A DC power source 22 having a positive potential is connected to the electrode 24. Further, although not shown in FIG. 1, a reaction gas introduction mechanism and an exhaust mechanism are provided.

In the plasma generator configured as described above, plasma is generated as follows. First, the reaction chamber
While the 10 is exhausted, a reaction gas is supplied into the reaction chamber 10 so that the inside of the reaction chamber 10 is adjusted to a predetermined pressure. In this state, the matching controller 21a from the electromagnetic wave generator 20a
When an electromagnetic wave is supplied to the coil 23 through, the electrons in the plasma generation chamber 11 are driven by inductive coupling with the coil 23, the electrons repeatedly collide with gas molecules, and as a result, high-density plasma is generated in the plasma generation chamber 11. To generate.

The plasma generated in the plasma generation chamber 11 spreads to the reaction chamber 10 by diffusion. At this time, the reaction chamber
Since most of the 10 are grounded, the plasma
The potential of the plasma itself is adjusted so that an equal amount of electrons and ions are lost in the grounded reaction chamber. As a result, the floating potential of the plasma is close to the ground potential, and the plasma potential is approximately 10-30 V, which is the sum of the floating potential and the value of 3-5 times the electron temperature.

At this time, a positive DC potential V is applied to the electrode 24. Here, this potential V satisfies V> 19xTe + Vs when the plasma potential is Vs and the electron temperature of the plasma is Te. When this condition is satisfied, electromagnetic waves are emitted from the end of the electron sheath formed in the electrode. The electrons in the plasma oscillate by the electromagnetic waves while drifting toward the electron sheath. In this way, the electrons, which have obtained energy from the electrode 24, collide with gas molecules in the reaction chamber 10 one after another to generate plasma.

Here, the physical process of emitting electromagnetic waves from the end of the electron sheath is as follows. It is the electrons and ions that diffuse from the plasma that make up the electron sheath. Therefore, the response speed of the electric field in the electron sheath is about the plasma frequency of electrons. When electrons flow into the electron sheath at a speed higher than the response speed of the electric field, the electric field of the electron sheath cannot follow the movement of the electric field of the inflowing electrons. At this time, a discontinuous surface of the electric field is formed in the electron sheath, and electromagnetic waves are emitted by the oscillating electric field generated in the process of relaxation. At this time, the higher the velocity of the electrons flowing in, that is, the higher the potential V applied from the DC power source 22, the stronger the intensity of the emitted electromagnetic wave. The frequency of the emitted electromagnetic wave is about the plasma frequency (GHz). This electromagnetic wave generation mechanism is exactly the same as the principle of the oscillation diode.

In order to generate an electron sheath at the electrode 24, there is a limitation that the amount of electrons flowing into the electrode 24 among the electrons lost from the whole plasma in the reaction chamber 10 must be negligible. . Therefore, the area of the electrode 24 cannot be increased at all. The area of the electrode 24 is determined by the energy distribution of electrons, the mass ratio of electrons to ions, and the area of the structure having the ground potential in the reaction chamber, and is generally 50% or less of the area of the structure having the ground potential in the reaction chamber. . Theoretically, when the area of the electrode 24 is extremely small, the plasma potential is not influenced by the electrode. However, when the area of the electrode 24 becomes large to some extent or the electric potential of the electrode 24 becomes high to some extent, the electric potential of the plasma in the vicinity of the electrode is dragged by the electric potential of the electrode 24 and rises to form an electrostatic field in the plasma. In this case, electrons flow into the electrode 24 not only by diffusion from the plasma but also by the drift mechanism by the electrostatic field.

As described above, the electrode 24 transfers energy to electrons through the two mechanisms of electromagnetic wave emission and electrostatic drift of electrons. Therefore, by adjusting the potential of the DC power source 22, the amount of energy transferred from the electrodes to the plasma can be adjusted. Since this energy transfer mechanism is different from the inductive coupling by the coil 23, the activation of gas molecules in the vicinity of the electrode 24 is different from that in the plasma generation chamber 11. Furthermore, by adjusting the electric power of the electromagnetic wave applied to the coil 23 and the electric power applied to the electrodes, the amount and distribution of plasma in the reaction chamber 10 can be controlled.

The present invention is not limited to the embodiment shown in FIG. 1, and various modifications are possible. For example, the following modifications are possible.

(1) The shape of the electrode 24 can be freely changed.
The shape is not limited to the single cylindrical shape shown in (1), and may be flat, rod-shaped, or ring-shaped, or may be divided.

(2) As in the embodiment shown in FIG. 2, not only a DC power source but also an electromagnetic wave generator can be connected to the electrode 24.

(3) As in the embodiment shown in FIG. 2, the coil 23
The number of windings, the shape and the number, or the shape of the plasma generating unit 11 and the positional relationship with the reaction chamber 10 are not limited to those shown in the drawings.
It can be freely transformed. The second embodiment will be described below.

The second embodiment shown in FIG. 2 employs a structure in which the number of plasma generating chambers 11 and the number of coils 23 are increased, and an electromagnetic wave generator 20b is connected to the electrode 24 via a matching controller 21b. The configuration is adopted. (a) is a cross-sectional view of the plasma generator, and (b) is a plan view showing the positional relationship among the workpiece 31, the coil 23 and the electrode 24.

As shown in FIG. 2, by disposing a plurality of plasma generating chambers on a concentric circle, controllability of the amount and distribution of plasma in the reaction chamber 10 can be improved. That is, by controlling the power supply to the plasma reaction chamber 23a in the center of the concentric circles, the plurality of plasma reaction chambers 23b arranged on the circumference and the electrode 24, the amount of plasma generated in each portion of the reaction chamber and The distribution can be controlled more finely.

Further, when a high frequency is applied to the electrode 24 by the electromagnetic wave generator, different oscillating electric fields can be applied to the electrons of the plasma, and the generation amount of the plasma and the plasma distribution can be controlled more finely.

When using a plurality of coils 23, a mechanism for controlling the energy emitted from each coil is required. This control mechanism is shown in FIG. Each coil is composed of a coil L and an impedance adjustment unit Z, which are connected in parallel. In addition to this, Impedan matching controller 21a
To connect the electromagnetic wave generation source 20a. When an electromagnetic wave enters and enters the coil 23, a part of the energy of the electromagnetic wave is transmitted and the rest is reflected according to a certain ratio determined by the impedance of the coil 23. However, the reflected electromagnetic wave energy is reflected again by each coil by the impedance matching controller 21a. By repeating this, the energy of the electromagnetic wave finally becomes
All pass through the coil 23. For example, two coils 23a, 2
3b, and those impedances of the incident energy
If it is adjusted so that a% and b% are transmitted,
In the circuit of, all the energy finally incident is distributed to the coils 23a and 23b in a: b. Therefore, even if a plurality of coils are connected in parallel, the energy of the electromagnetic wave distributed to each coil can be adjusted by adjusting the impedance of each coil.

(4) As in the embodiment shown in FIG. 4A, the positional relationship between the electrode 24 and the coil 23 (plasma generation chamber 11) in the reaction chamber 10 can be reversed. In this case, it is possible to replace the cylindrical electrode 24 of FIG. 4 (a) with a plurality of disc-shaped electrodes as shown in the plan view of FIG. 4 (b).

[0028]

As described above, in the plasma generating apparatus provided with the reaction chamber for holding the plasma, the electromagnetic wave generation source, and the electromagnetic wave emission section for emitting the electromagnetic wave generated by the electromagnetic wave generation source to the reaction chamber, The electromagnetic wave emission part is a coil for plasma generation attached to the plasma generation part connected to the reaction chamber, and an electrode for supplying electric power to the plasma in the reaction chamber, so that the amount of plasma in the reaction chamber It is possible to provide a plasma generation source capable of controlling its distribution or the activity of gas components.

[Brief description of drawings]

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

FIG. 2 is a schematic configuration diagram of a plasma generator according to another embodiment of the present invention.

FIG. 3 is a configuration diagram showing an electromagnetic wave energy distribution control method for a plurality of coils.

FIG. 4 is a schematic configuration diagram of a plasma generator according to another embodiment of the present invention.

[Explanation of symbols]

10 ... Plasma reaction chamber, 11 ... Plasma generating unit, 20 ...
Electromagnetic wave generator, 21 ... Impedance matching controller, 22 ... DC power supply, 23 ... Coil, 24 ... Electrode,
25 ... Choke coil, 31 ... Work piece, 32 ... Electrode on which work piece is mounted.

Claims (6)

[Claims] 1. A plasma generating apparatus comprising: a reaction chamber for holding plasma; an electromagnetic wave generation source; and an electromagnetic wave emission unit for emitting the electromagnetic wave generated by the electromagnetic wave generation source to the reaction chamber, wherein the electromagnetic wave emission unit is a reaction unit. A plasma production apparatus comprising: a plasma production coil attached to a plasma production unit connected to the chamber; and an electrode in the reaction chamber for supplying electric power to the plasma. 2. The plasma generating apparatus according to claim 1, wherein the electromagnetic wave radiating portion is a combination of one or a plurality of plasma generating coils and one or a plurality of electrodes. apparatus. 3. The plasma generating apparatus according to claim 1, wherein the plasma generating coil or electrode is arranged on the circumference. 4. The voltage applied to an electrode for supplying electric power to plasma in the reaction chamber in the plasma generator.
A plasma generation device characterized in that V satisfies V> 19xTe + Vs, where Vs is the plasma potential and Te is the plasma electron temperature. 5. The plasma generation apparatus according to claim 1, wherein an area of an electrode for supplying electric power to the plasma in the reaction chamber is smaller than an area of a structure in contact with the plasma at a ground potential. Plasma generator. 6. In the plasma generator, when a plurality of coils are used, each coil has an impedance adjusting function, each coil is connected in parallel, and an electromagnetic wave is supplied to each coil. A plasma generation apparatus having an impedance matching mechanism on the output side of an electromagnetic wave generator.