JP2002313736A - Plasma treating equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide plasma treating equipment wherein treatment of high quality is enabled at a high speed. SOLUTION: This plasma treating equipment is provided with a cathode 2, a high frequency power source 5 connected with the cathode 2, and a magnetron magnetic field generating means (magnet 20) which is arranged in the vicinity of the cathode 2. At least the surface of the cathode 2 whose surface facing the plasma (grow region 6) is composed of metal containing at lest one kind out of W, Ta, Mo, Ti and Zr, or alloy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an apparatus for performing plasma processing such as plasma CVD and plasma etching.

[0002]

2. Description of the Related Art Si thin films and DLC (Diamond Like Carbo)
n) Plasma CVD is used to form a thin film. In addition, plasma etching is used to form a fine pattern required for manufacturing a semiconductor element or the like. Plasma CVD is a method of forming a film by converting a raw material gas into plasma and depositing ionized and dissociated species such as ions and radicals in the plasma on the surface of a substrate. On the other hand, plasma etching uses ionization and
This is a method of performing etching by causing a dissociated species to collide with an object to be processed.

As a plasma generation source used for plasma processing such as plasma CVD and plasma etching, for example, a capacitively-coupled high-frequency plasma source using a frequency of 13.56 MHz and Japanese Patent Application Laid-Open No. 64-65843 are disclosed. Some of them use electron cyclotron resonance (ECR). Among them, the capacitively-coupled high-frequency plasma source can perform large-area processing and stable discharge, and can be manufactured at a lower cost than an ECR plasma source.

The capacitively coupled high-frequency plasma processing apparatus generates plasma between a high-frequency electrode and a ground electrode, and applies a high-frequency voltage to the high-frequency electrode via a coupling capacitor. At this time, a deep negative bias is formed on average by the self-bias effect, so that the high-frequency electrode functions as a cathode. Then, a glow region is generated between the high-frequency electrode and the ground electrode. In this specification, the high-frequency electrode is called a cathode, and the ground electrode is called an anode.

FIG. 2 is a sectional view showing a main part of a capacitively coupled plasma processing apparatus and a potential distribution in the processing apparatus. In the device shown in FIG. 2, a cathode 2 and an anode 3 are arranged to face each other, a high frequency power supply 5 is connected to the cathode 2 via a coupling capacitor 4, and the anode 3 is grounded. Cathode 2
When a high-frequency voltage is applied to the electrodes, a glow region 6 that is a high-density plasma region is generated between the two electrodes, and a cathode sheath is formed on the front surface (the surface facing the plasma) of the cathode 2 and the anode 3 An anode sheath is formed on the front surface (surface facing the plasma). Both the cathode sheath and the anode sheath are regions where light emission is weak.

[0006] A large potential difference appears in the cathode sheath, and ions in the plasma are accelerated by this potential difference and collide with the cathode 2 with a large energy, and secondary electrons (γ electrons) are emitted from the surface of the cathode 2 by the γ action. . Released γ
The electrons are accelerated by the potential gradient in the cathode sheath and enter the glow region 6 with a large energy, and ionize the gas molecules by the α action, so that the discharge is maintained. The darkness of the cathode sheath is caused by the γ emitted from the cathode 2.
This is because the gas molecules cannot be excited until the electrons are accelerated to the lowest excitation energy of the gas molecules.

On the other hand, in the vicinity of the anode 3, the electron current density to the anode 3 is usually smaller than the current density associated with the random particle flux, so that the anode potential becomes lower than the plasma potential in order to repel electrons by that much. Thus, an anode sheath having a potential gradient as shown is formed. However, when the area of the anode is small and the electron current density is equal to or higher than the current density associated with the random particle flux, the anode becomes higher than the plasma potential, and an electron sheath with partial ionization may be formed. In addition,
When the anode potential is lower than the plasma potential as in the example shown,
The anode sheath is an ion sheath.

[0008]

To increase the processing speed in a plasma processing apparatus, it is effective to increase the plasma density. As a thin film forming means capable of increasing the plasma density, for example, a magnetron sputtering method is known. In the magnetron sputtering method, electrons draw a cycloidal trajectory in the vicinity of a target functioning as a cathode by the action of orthogonal electric and magnetic fields.
As a result, the electrons repeatedly collide with the plasma gas, and a high-density plasma is generated. Therefore, the sputtering efficiency of the target is increased, and a high-speed film can be formed.

The present inventors, as shown in FIG.
A flat magnetron type electrode is formed by arranging a magnet on the back side (left side in the figure) of
A thin film was formed by the VD method. However, as in the case of magnetron sputtering, the cathode 2 is sputtered,
As a result, the cathode constituent material is mixed into the thin film formed on the processing target 7. Therefore, although it depends on the required level, it has been found that a thin film of desired quality may not be formed.

An object of the present invention is to provide a plasma processing apparatus capable of performing high quality processing at high speed.

[0011]

This and other objects are achieved by the present invention which is defined below as (1) to (3). (1) A cathode, a high-frequency power supply connected thereto, and a magnetron magnetic field generating means near the cathode, wherein at least the surface of the cathode facing the plasma is W, Ta, M
A plasma processing apparatus comprising a metal or an alloy containing at least one of o, Ti and Zr. (2) The plasma processing apparatus according to (1), wherein at least a surface of the cathode facing the plasma is a metal or an alloy composed of at least one of W, Ta, Mo, Ti and Zr. (3) The plasma processing apparatus according to the above (1) or (2), which is used for plasma processing using a gas containing H ₂ .

[0012]

FIG. 1 is a sectional view of a main part of a plasma processing apparatus according to the present invention and a potential distribution in the processing apparatus.

In this device, the cathode 2 has a magnet 20 as a magnetron magnetic field generating means on the back side, and is a flat magnetron type electrode. FIG. 4 shows the structure of the magnet 20. FIG. 4 shows the device shown in FIG.
FIG. 3 is a cross-sectional view when the cathode 2 side is viewed from the anode 3 side. However, the cathode 2 has been removed, and the vacuum chamber 100 accommodating the main part of the apparatus is shown. As shown in FIG.
The magnet 20 is composed of a center magnet 20A and an annular outer peripheral magnet 20B surrounding the center magnet 20A, similarly to a normal magnetron sputtering apparatus. However, the center magnet 20A
Has an annular structure in order to introduce a processing gas such as a source gas into the vacuum chamber 100 from the center thereof. The configuration of the apparatus shown in FIG. 1 other than the magnet 20 is the same as that of the conventional apparatus shown in FIG. Easy to cathode 2 is sputtered when the planar magnetron type electrode, a large amount of ions generated by the high density plasma are accelerated by the cathode sheath voltage V _S, in order to enter the cathode 2. Incidentally, a cathode sheath voltage V _S, as shown in FIG. 1, a value obtained by subtracting the cathode potential V _C from the plasma potential V _P.

Therefore, in the present invention, the cathode 2 is made of a material which is not easily sputtered by ions. as a result,
The amount of the constituent material of the cathode 2 flying to the processing target 7 is reduced.
Therefore, if the present invention is applied to a plasma CVD apparatus,
It is possible to form a high-quality thin film with a small amount of impurities on the object to be processed 7 at a high speed, and if the method is applied to plasma etching, the object to be processed 7 can be etched at a high speed, and furthermore, impurities on the surface to be etched can be obtained. Adhesion can be prevented.

[0015] As a cathode constituting material in a normal plasma processing apparatus, good workability and NF ₃ used as a cleaning gas when cleaning the inside of the apparatus are used.
Al is often used because of its low reactivity with respect to. However, a cathode made of Al is relatively easily sputtered. On the other hand, in the present invention, the cathode 2 is made of W, T
a, Mo, a metal or an alloy containing at least one of Ti and Zr, preferably W, Ta, M
o, a metal or an alloy comprising at least one of Ti and Zr, more preferably W, Ta, Mo, T
It is composed of any one of i and Zr. As a result, the amount of cathode sputtering can be significantly reduced.

In the present invention, at least the surface of the cathode 2 facing the plasma may be made of the above material. That is, the entire cathode may be made of these materials, or only the vicinity of the surface facing the plasma may be made of the above materials. In the latter case, it is preferable that the material that is difficult to be sputtered exists over a thickness of 3 μm or more from the surface of the cathode facing the plasma.

The present invention is particularly effective when at least H ₂ is used as a raw material gas or a working gas. That is, the amount of sputtering of the cathode when the gas containing H ₂ is turned into plasma is significantly reduced by the present invention. H ₂
Is used, for example, when a thin film made of amorphous silicon is formed by a plasma CVD method.

The processing apparatus of the present invention is not particularly limited except for the constituent material of the cathode, and may be the same as a conventional plasma processing apparatus.

FIG. 3 shows a specific configuration example of the plasma processing apparatus of the present invention. FIG. 3 is obtained by adding a vacuum chamber 100 for accommodating the cathode 2 and the anode 3 to the main part shown in FIG.

An object 7 made of a long flexible film is held in a wound state on the surface of the anode 3 so that continuous plasma processing can be performed.

The vacuum chamber 100 is provided with an exhaust path 101 and a source gas introduction path 102. Plasma CVD
Is performed, the gas in the vacuum chamber 100 is evacuated from an exhaust path 101 connected to an oil rotary pump, a turbo molecular pump, or the like (not shown) to make the inside of the chamber a high vacuum of about 10 ^-4 to 10 ^-5 Pa. Keep this up. Next, the source gas is introduced into the vacuum chamber 100 from the source gas introduction path 102. The supply of the source gas to the source gas introduction path 102 is adjusted by a mass flow controller (not shown). By providing a plurality of mass flow controllers, two or more types of gases can be mixed and used as a source gas.

The pressure in the vacuum chamber 100 during the plasma CVD is preferably 700 Pa or less, more preferably 5 to 20 Pa.
0 Pa. If the pressure is too low, it becomes difficult to increase the plasma density, and the efficiency of the plasma processing is reduced. On the other hand, if the pressure is too high, the generation of higher-order radicals cannot be ignored and it is difficult to obtain a high-quality CVD film.

The pressure in the vacuum chamber 100 during the plasma etching is preferably 400 Pa or less, more preferably 5 Pa or less.
It is 200 Pa. If the pressure is too low, it becomes difficult to increase the plasma density, and the efficiency of the plasma processing is reduced. On the other hand, if the pressure is too high, the etching efficiency tends to decrease due to the generation of polyatomic molecules.

A heating means for heating the object to be processed 7, for example, an electric heater or the like is provided at or near the anode 3 if necessary.

Further, a DC bias voltage may be applied to the anode 3 as needed. When a DC bias voltage is applied in a direction to lower the anode potential, ions are accelerated toward the object to be processed 7, which is particularly effective for improving the efficiency in plasma etching.

The present invention can be applied to the formation of various CVD films. For example, polycrystalline or single crystal diamond, Si,
_{SiC, BN, C, SiN x} , amorphous film made of SiO _x or the like, Si, SiC, polycrystalline film composed of c-BN and the like, Si, SiC, in any production, such as single crystal film composed of c-BN and the like The present invention can also be applied.

The source gas used in the plasma CVD is as follows:
What is necessary is just to select suitably similarly to the conventional according to the formation object,
There is no particular limitation.

[0028]

EXAMPLE No. 1 A plasma processing apparatus having the structure shown in FIG.
A 0.7 μm thick thin film made of amorphous silicon was formed on a polyethylene naphthalate film substrate having a thickness of 0.7 m by a plasma CVD method. The cathode 2 of this device has W
It consisted of. Material gas and its flow _{rate, SiH 4: 50sccm, H 2} : was 500 sccm. Table 1 shows the operating pressure, the cathode sheath voltage V _S, and the plasma density.

Case No. 2 (Comparative) An amorphous silicon thin film was formed in the same manner as in Case No. 1 except that the cathode 2 was made of Al.

Case No. 3 (Comparison) An apparatus having the structure shown in FIG. 2, that is, a conventional apparatus having no magnet for generating a magnetron magnetic field, was used, and
l, an amorphous silicon thin film was formed in the same manner as in Case No. 1.

Evaluation For the thin films formed in each of the above cases, the amount of the cathode constituent material mixed was measured by SIMS. Table 1 shows the results.
In Table 1, “below the detection limit” means 10 ¹⁷ cm ^−3.
Means:

[0032]

[Table 1]

In Table 1, in case No. 2 in which a magnet for generating a magnetron magnetic field was provided but the cathode was made of Al, although the plasma density was high, the amount of the cathode constituent elements mixed into the thin film was extremely large. . In case No. 3 using the conventional apparatus, no cathode constituent element was mixed into the thin film, but the plasma density was low. In contrast,
In Case No. 1 using the apparatus of the present invention in which a magnet for generating a magnetron magnetic field was provided and the cathode was made of W, the plasma density was almost equal to that of Case No. 2, and the cathode constituent elements were contained in the thin film. No contamination is observed.

The cathode is made of Ta, Mo, Ti or Zr.
However, even in the case where the element was formed from the above, mixing of the cathode constituent elements into the amorphous silicon thin film could be suppressed without substantially lowering the plasma density.

[0035]

The plasma processing apparatus of the present invention has a magnet for generating a magnetron magnetic field, so that high-speed plasma processing can be performed. That is, high-speed film formation in plasma CVD and high-speed etching in plasma etching are realized. In addition, since the cathode of the apparatus of the present invention is made of a material that is not easily sputtered, high-quality plasma processing can be performed.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a main part of a plasma processing apparatus of the present invention and a graph showing a potential distribution between a cathode and an anode of the apparatus.

FIG. 2 is a sectional view showing a main part of a conventional plasma processing apparatus and a graph showing a potential distribution between a cathode and an anode of the apparatus.

FIG. 3 is a cross-sectional view illustrating a specific configuration example of the plasma processing apparatus of the present invention.

FIG. 4 is a cross-sectional view illustrating a configuration of a magnet for generating a magnetron magnetic field provided in the plasma processing apparatus of the present invention.

[Explanation of symbols]

 2 Cathode 20 Magnet 20A Center magnet 20B Peripheral magnet 3 Anode 4 Coupling capacitor 5 High frequency power supply 6 Glow area 7 Workpiece 100 Vacuum tank 101 Exhaust path 102 Source gas introduction path

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Shuichi Takamura 11-11, 5860, Nagado, Asahigaoka-cho, Owariasahi-city, Aichi Prefecture (72) Inventor Yoshihiko Uesugi 203, 2609 Tokugawa-cho, Higashi-ku, Nagoya-shi, Aichi 203 72) Inventor Tetsuyasu Ohno 5- 2105 Kakuyama, Nisshin-shi, Aichi F-term (reference) 4G075 AA24 AA30 BC04 BC06 CA25 CA26 CA47 CA62 DA02 EC21 FB02 4K030 AA06 AA17 BA30 CA07 CA12 FA03 HA06 KA14 KA30 KA34 KA46 BA01 A04 A04 A04 A04 BB12 BB13 CA02 5F045 AA09 AB04 AE17 AE19 AE21 BB02 BB09 DP09 EB03 EH04 EH08 EH14

Claims (3)

[Claims] A cathode, a high-frequency power supply connected thereto, and a magnetron magnetic field generating means near the cathode, wherein at least a surface of the cathode facing the plasma is W, T
A plasma processing apparatus comprising a metal or an alloy containing at least one of a, Mo, Ti and Zr. 2. The plasma processing apparatus according to claim 1, wherein at least the surface of the cathode facing the plasma is a metal or an alloy composed of at least one of W, Ta, Mo, Ti and Zr. 3. The plasma processing apparatus according to claim 1, which is used for plasma processing using a gas containing H ₂ .