JPH06208972A - Plasma processing method - Google Patents

Abstract

PURPOSE:To suppress abnormal discharge by adding the mixture gas containing CF4 used as etching gas with the mixture gas containing at least one of SF6, C2F6, or NF3. CONSTITUTION:An upper part electrode 1 and a lower electrode 2 are, with a specified interval, assigned in parallel in a reaction chamber 3. Many gas introduction openings 4 are provided on the lower part electrode 2 side of the upper part electrode 1. The upper part electrode 1 is connected to a high frequency power source 5, and the lower part electrode 2 is earthed. Relating to etching gas, the mixture gas of CF4 containing 10% of O2 is added with SF6 far suppressing abnormal discharge, then introduced from the gas introduction openings into the reaction chamber 3. The mixture gas of CF4 and O4, and SF6 are flow-controlled by a mask controller. Further, the reaction gas for Si2 film deposition is also introduced from the gas introduction openings into the reaction chamber 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma etching method and a plasma cleaning method, and particularly when a distance between electrodes facing each other is small, it tends to occur when a gas plasma is generated using a mixed gas containing CF _4. The present invention relates to a device capable of suppressing abnormal discharge.

[0002]

2. Description of the Related Art A schematic diagram of a plasma etching apparatus used for manufacturing a semiconductor integrated circuit is shown in FIG. In FIG. 1, the upper electrode 1 and the lower electrode 2 are installed in parallel in the reaction chamber 3 with an interelectrode distance d. The semiconductor substrate 6 is placed on the lower electrode 2. A gas inlet 4 is provided on the lower electrode 2 side of the upper electrode 1. The lower electrode 2 is connected to the high frequency power supply 5, and the upper electrode 1 is grounded. The etching gas is introduced into the reaction chamber 3 through the gas inlet 4.

The structure of a plasma etching apparatus used for manufacturing a large-sized liquid crystal substrate is basically the same as that shown in FIG.

In the production of semiconductor integrated circuits and liquid crystal substrates, when etching SiO ₂ or Si ₃ N _4, etc.,
Generally, a gas containing CF ₄ is used as an etching gas. Upon mixing of O ₂ in CF _4, as compared with etching by only CF _4, the etching rate increases,
A gas added with CF ₄ O ₂ is used as an etching gas. In order to improve the etching selection ratio between the insulating film to be etched and the underlying Si, CHF is added.
It is also common to mix ₃ or H ₂ .

The distance d between the electrodes is defined by the upper electrode 1 and the lower electrode 2.
If the diameter (diagonal length of the electrode if the electrode shape is not circular) is smaller than 1/15 of the diameter of the electrode (diagonal length of the electrode if the electrode shape is not circular) Since the plasma is confined between the electrodes, the plasma density increases and the etching rate increases. This method has been put to practical use as a narrow gap RIE method. Also in the narrow gap RIE method, a mixed gas containing CF ₄ is used as an etching gas.

In addition to the above-described plasma etching method, a plasma cleaning method performed after the film deposition step by the plasma CVD method has been put into practical use as the plasma processing using a mixed gas containing CF _4. is there.

Particularly in the step after the formation of the AI wiring, S
As a method for depositing iO ₂ or Si ₃ N ₄ , a plasma CVD method capable of forming a film at low temperature is widely used. FIG. 2 shows a schematic diagram of a plasma CVD apparatus used for manufacturing a semiconductor laminated circuit. In FIG. 2, the upper electrode 1 and the lower electrode 2 are arranged in parallel in the reaction chamber 3 with an interelectrode distance d ₂ therebetween. The semiconductor substrate 6 is placed on the lower electrode 2. A gas inlet 4 is provided on the lower electrode 2 side of the upper electrode 1. The upper electrode 1 is connected to the high frequency power supply 5, and the lower electrode 2 is grounded. The reaction gas is introduced into the reaction chamber 3 through the gas inlet 4.

Plasma CV used for manufacturing liquid crystal substrates
The configuration of the D device is basically the same as that of FIG. 2 regarding the single-wafer type. As for the batch type, a tray type in which a substrate is fixed to a tray as shown in FIG. 3 to form a film is adopted. In FIG. 3, the electrode 1 and the tray 2 are arranged in parallel in the reaction chamber 3 with a distance d ₃ between the electrodes. Further, in order to improve the processing capacity, it is general that two pairs of the electrodes 1 and the tray 7 are provided on both sides of the heater 8. The liquid crystal substrate 6 is fixed to the tray 7. A gas inlet is provided on the tray 7 side of the electrode 1. The electrode 1 is connected to a high frequency power source 5, and the tray 7 is grounded and has a function as a second electrode (ground electrode). The reaction gas is introduced into the reaction chamber 3 through the gas inlet 4.

In the plasma CVD method, the distance between the electrodes is set to the upper electrode 1 (the electrode 1 in the tray type) and the lower electrode 2.
1 of the diameter of the electrode having the smaller diameter (the length of the diagonal line of the electrode when the electrode shape is not circular) out of (the tray 7 in the case of the tray type) (the length of the diagonal line of the electrode when the electrode shape is not circular) When it is set to / 15 or less, the deposition rate remarkably increases. This method is also applicable to narrow gap plasma C
It has been put to practical use as the VD method.

When the insulating film is deposited on the substrate by the plasma CVD method, the insulating material is deposited on the upper and lower electrodes (in the case of the tray type, the electrode and the tray) and the inner wall of the reaction chamber. The deposits are peeled off during the reaction or during the transfer of the substrate and become dust. Furthermore, if a gas plug (generally, a hole having an inner diameter of 0.4 to 1.0 mm) generally provided in the upper electrode (the electrode in the case of a tray type) is clogged with a deposit, the in-plane uniformity of the deposition rate is Becomes worse.

Therefore, after the step of film deposition by the plasma CVD method is completed, the substrate is taken out of the reaction chamber, and then an etching gas is introduced into the reaction chamber to generate plasma, so that the inner wall of the reaction chamber and the electrodes are formed. Plasma cleaning is performed for the purpose of removing the deposited insulator. (In the case of the tray type, the tray is cleaned off-line.) Also in this plasma cleaning method, a mixed gas containing CF ₄ is generally used as an etching gas, as in the plasma etching method.

[0012]

As is clear from the above description, the plasma cleaning method as a plasma etching method has a commonality in that the insulating film is removed. Etching gas,
As a cleaning gas, a mixed gas containing CF ₄ is generally used. Further, in order to increase the etching rate in the plasma etching method or the deposition rate in the plasma CVD method, the narrow gap between the electrodes reduces the distance between the electrodes. Is being done.

However, when a mixed gas containing CF ₄ is used, the distance between the electrodes is set to the upper electrode (tray type plasma C
VD device electrode) and lower electrode (tray type plasma C)
The diameter of the electrode having the smaller diameter (the length of the diagonal line of the electrode when the electrode shape is not circular) in the tray in the case of the VD device (the length of the diagonal line of the electrode when the electrode shape is not circular)
If it is set to 1/15 or less, the plasma may become unstable. Especially when the pressure in the reaction chamber is lowered and the high frequency power is increased, abnormal discharge is likely to occur. Abnormal discharge is a phenomenon in which a portion having an abnormally high plasma density locally occurs, which not only deteriorates the in-plane uniformity of etching or cleaning, but also damages the electrode and the substrate. When abnormal discharge occurs, the etching rate or cleaning rate must be sacrificed to reduce the high frequency power. In view of such problems of the conventional method, the present invention relates to a plasma etching method and a plasma cleaning method, and particularly when generating a gas plasma using a mixed gas containing CF ₄ when the distance between opposing electrodes is small. The purpose is to suppress abnormal discharge that tends to occur.

[0014]

In the present invention, a mixed gas containing at least one of SF ₆ , C ₂ F ₆ and NF ₃ is added to a mixed gas containing CF ₄ used as an etching gas (cleaning gas). .

[0015]

According to the present invention, a mixed gas containing CF ₄ used as an etching gas (cleaning gas) is mixed with SF ₆ and C.
By adding a mixed gas containing at least one of ₂ F ₆ and NF ₃ , plasma can be stabilized, and as a result, abnormal discharge that tends to occur when the distance between the electrodes is small can be suppressed.

[0016]

EXAMPLE A cleaning process after the film deposition process by the plasma CVD method used for depositing an interlayer SiO ₂ film in a manufacturing process of a reaction body integrated circuit having a multilayer wiring structure will be described below as an example. The apparatus used for the experiment is a 6-inch plasma CVD apparatus for semiconductor substrates.

In FIG. 2, the upper electrode 1 having a diameter of 150 mm and the lower electrode 2 having a diameter of 150 mm have a distance of 5 m.
m are arranged in parallel in the reaction chamber 3. A large number (about 3000) of gas inlets 4 having a hole diameter of 0.5 mm are provided on the lower electrode 2 side of the upper electrode 1. The upper electrode 1 is connected to the high frequency power supply 5, and the lower electrode 2 is grounded. Etching gas (cleaning gas), the O ₂ to 10% inclusive mixed gas CF _4, after the addition of SF ₆ for the abnormal discharge suppression is introduced into the reaction chamber 3 through the gas inlet 4. The flow rate of the mixed gas of CF ₄ and O ₂ and SF ₆ can be controlled by a mass flow controller (not shown). Also, the reaction gas for depositing the SiO ₂ film is similar to the etching gas (cleaning gas).
It is introduced into the reaction chamber 3 through the gas inlet 4.

In FIG. 4, a SiO ₂ film is deposited to a thickness of 2 μm on a semiconductor substrate under normal deposition conditions, the substrate is taken out of the reaction chamber, the pressure in the reaction chamber is set to 500 mmTorr, and an etching gas (cleaning gas) is used. Total flow rate of 60sc
cm (constant) and the addition amount of SF ₆ (flow ratio) is 0 to 2
This is obtained by changing the value to 0% to find the maximum high-frequency power that enables normal discharge without abnormal discharge.

As can be seen from FIG. 4, the amount of SF ₆ added is 0%.
When, there is no condition for normal discharge. As the amount of SF ₆ added increases, the maximum high frequency power that can be normally discharged increases. When the amount of SF ₆ added becomes 20%,
Discharge of 1000 W is possible. When the SF ₆ addition amount is further increased, the maximum high frequency power that can be normally discharged is further increased.

In this embodiment, the cleaning process after the film deposition process by the plasma CVD method used for manufacturing a semiconductor integrated circuit has been described, but the present invention is applicable to a plasma CVD apparatus used for manufacturing a liquid crystal substrate, etc. The method is also applicable to the cleaning method in the plasma CVD apparatus, or the plasma etching method used for manufacturing semiconductor integrated circuits, liquid crystal substrates and the like.

In this embodiment, CF ₄ containing 10% of O ₂ is used as the mixed gas containing CF ₄ .
Of course, the mixing ratio of O ₂ is not limited to 10%. Alternatively, the mixed gas containing CF ₄ may contain a component other than O ₂ , such as CHF ₃ or H ₂ .

In the present embodiment, the case where the inter-electrode distance is 5 mm has been described, but in the present invention, the inter-electrode distance is the diameter of the two electrodes (if the electrode shape is not circular, the length of the diagonal line of the electrodes). Is smaller than 1/15 of the diameter of the smaller electrode (if the electrode shape is not circular, the diagonal length of the electrode) is not more than 1/15.

In this embodiment, SF ₆ is used as the gas for suppressing abnormal discharge added to the mixed gas containing CF ₄ , but the additive gas is not limited to SF _6. The same effect can be obtained by adding a mixed gas containing at least one of ₆ , C ₂ F ₆ and NF ₃ .

[0024]

As described above, according to the present invention, in a plasma CVD apparatus, a mixed gas containing CF ₄ used as a cleaning gas (etching gas) contains SF ₆ , C ₂ F ₆ , and NF ₃ . By adding a mixed gas containing at least one of them, cleaning can be performed without causing abnormal discharge.

In the plasma etching method as well, an abnormal discharge is caused by adding a mixed gas containing at least one of SF ₆ , C ₂ F ₆ and NF ₃ to a mixed gas containing CF ₄ used as an etching gas. Can be suppressed.

[Brief description of drawings]

FIG. 1 is a block diagram of a plasma etching apparatus.

FIG. 2 is a configuration diagram of a plasma CVD apparatus according to an embodiment of the present invention.

FIG. 3 is a block diagram of a conventional CVD apparatus

FIG. 4 shows the maximum high-frequency power and S that enable normal discharge.
Characteristic diagram showing the relationship with the amount of F ₆ added

[Explanation of symbols]

 1 Upper electrode 2 Lower electrode 3 Reaction chamber 4 Gas inlet 5 High frequency power source

Claims (1)

[Claims] 1. A vacuum vessel having two electrodes, wherein
The distance between two electrodes is the diameter of the electrode with the smaller diameter (the length of the diagonal line of the electrode when the electrode shape is not circular) of the two electrodes (the length of the diagonal line of the electrode when the electrode shape is not circular) In the plasma processing apparatus of 1/15 or less, the plasma processing method is to introduce a mixed gas containing CF ₄ into the vacuum container and apply high frequency power between the two electrodes to generate gas plasma. And the CF
₄ in a mixed gas containing a plasma processing method characterized by adding a mixed gas containing at least one of _{SF 6, C 2 F 6,} NF 3.