JPH06216089A - Dry etching method - Google Patents

Abstract

PURPOSE:To prevent wiring malfunction due to aftercorrosion by providing a plasma etching step of replacing chlorine adhered to a wiring material with fluorine and a plasma etching step of forming a protective film on the material to disturb contact of the surface of the material with the atmosphere. CONSTITUTION:Cl2, CHCl3, BCl3, N2 gas are introduced as etching gas into a vacuum chamber. Al alloy of a wiring material is plasma etched. Thereafter, a pressure in the chamber is held at 600mTorr while introducing 50SCCM of CF4 gas, and high frequency power of 200W is applied for 30 sec. Then, two stages of postprocessing of introducing 50SCCM of CHF3 and applying high frequency power under similar conditions are conducted. After-corrosion occurring at the material can be completely prevented by providing the two stages of the postprocessing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry etching method capable of preventing after-corrosion which occurs when a wiring material on a semiconductor wafer is plasma-etched using a chlorine-based gas in a semiconductor manufacturing process. Is.

[0002]

2. Description of the Related Art In recent years, plasma etching using chlorine-based gas has been widely used for wiring processing of semiconductor devices.

The conventional plasma etching of the wiring material will be described below. FIG. 3 schematically shows an example of the reactive ion etching apparatus. This dry etching apparatus has a metallic vacuum chamber 4 in which an upper electrode 5,
The lower electrode 6 is installed, and the lower electrode 6 is kept at a constant temperature by the water circulation type temperature control device 7. Also,
A high frequency power source 9 is connected to the lower electrode 6 via an impedance matching circuit 8 and plasma can be generated between the electrodes 5 and 6. An etching gas is introduced into the vacuum chamber 4 through the mass flow controller 10, and the exhaust system 11 can appropriately maintain the pressure in the vacuum chamber 4.

With the above-described structure, the wiring material on the semiconductor wafer 12, which is the workpiece, is placed on the lower electrode 6 as shown in FIG. 3, and high-frequency power is applied between the electrodes in a chlorine-based gas inflow state. Is applied for plasma etching. After the etching is completed, when the semiconductor wafer 12 is taken out into the atmosphere, after-corrosion occurs in the wiring material.
Therefore, as a post-treatment, pure water cleaning or heat treatment, fluorine substitution of chlorine by fluorine-based gas plasma, protective film formation, dry ashing treatment, etc. are performed independently, or fluorine substitution, protective film formation and dry ashing are combined. Has been processed.

In order to evaluate the above-mentioned conventional method, Cl ₂ , CH ₂ is put in the vacuum chamber 4 of the dry etching apparatus.
Introducing Cl ₃ , BCl ₃ and N ₂ gas into Al which is a wiring material
After plasma etching the alloy,
Post-treatment was attempted under various etching conditions. After that, the semiconductor wafer 9 was taken out of the vacuum chamber 4 and left in the atmosphere, and after 5 minutes, 24 hours, and 48 hours, microscopic observation was performed.

First, the first post-treatment is formation of a protective film, and CHF ₃ gas, which is easy to form a Teflon-based polymer film, is added with 50 SCCM.
While introducing, the pressure in the vacuum chamber 4 is 600 mTorr
And the high frequency power of 200 W was applied for 30 seconds. Figure 2 shows the situation of after-corrosion caused by this post-processing.
It shows in (a).

The second method is chlorine substitution with chlorine. The CHF ₃ gas used in the first post-treatment is changed to CF ₄ gas which produces CF ₃ which is easily recombined with chlorine. Post-treatment was carried out under the conditions. The result is shown in FIG.

The third is dry ashing, in which the CHF ₃ gas used in the first post-treatment is changed to O ₂ and the post-treatment is performed by etching for 120 seconds. The result is shown in FIG.

[0009]

However, in any of the above-mentioned conventional methods, after-corrosion is likely to occur in the wiring material on the semiconductor wafer, particularly in the wiring material having a laminated structure which has been frequently used in recent years. It is difficult to completely prevent it, and there is a problem that wiring failure occurs.

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide a dry etching method for manufacturing a semiconductor device free from wiring defects due to after-corrosion.

[0011]

In order to achieve this object, the dry etching method of the present invention provides a method for etching a wiring material on a semiconductor wafer immediately after the step of etching the wiring material on a semiconductor wafer by generating plasma of chlorine-based etching gas. A two-step post-treatment process is provided, which is a plasma etching process of replacing the attached chlorine with fluorine and a plasma etching process of forming a protective film on the wiring material in order to prevent the surface of the wiring material from coming into contact with the atmosphere.

[0012]

It is considered that the cause of the after-corrosion is mainly that chlorine adhering to the wiring material after etching reacts with moisture in the atmosphere to form hydrochloric acid, which corrodes the Al alloy which is the wiring material. Therefore, this residual chlorine is replaced with fluorine that is stable to the atmosphere. This makes it possible to suppress the generation of hydrochloric acid. Further, the contact with hydrochloric acid is prevented by forming such a protective film on the wiring material by using the plasma of the fluorine-based gas which easily forms the polymer film. After-corrosion can be completely prevented by the above two effects.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. The dry etching apparatus to which the dry etching method of the present invention is applied has the same configuration as that shown in the prior art and is shown in FIG.

Vacuum chamber of this dry etching apparatus
Cl as etching gas in -4 ₂, CHCl₃, BC
l₃, N₂Gas is introduced and the Al alloy that is the wiring material is plated.
After the etching, the post-treatment of the present invention as shown below
Tried. That is, CF_FourIntroducing 50 SCCM of gas
Keep the pressure in the vacuum chamber 4 at 600 mTorr and 2
After applying high frequency power of 00W for 30 seconds, CHF₃Gas
Introduce 50 SCCM and apply high frequency power under the same conditions.
This is the post-treatment of the stage.

The principle of this post-processing will be described with reference to FIG. First, in the first step, in order to remove chlorine in FIG. 1 (a), C which forms CF ₃ which is easily recombined with chlorine is produced.
Introduce F ₄ gas. As a result, chlorine can be replaced with fluorine as shown in FIG. Next, in the second step, CHF ₃ gas, which easily forms a Teflon-based polymer film, is introduced. As a result, a protective film as shown in FIG. 1C can be formed. After-corrosion is prevented by the above two effects.

After completion of this post-treatment, the semiconductor wafer 12 is taken out of the vacuum chamber 4 and left in the atmosphere, and
After a lapse of minutes, 24 hours, and 48 hours, microscopic observation was performed and it was confirmed that the occurrence of after-corrosion could be completely prevented. This is shown in FIG. Furthermore, 15
It was confirmed that after-corrosion hardly occurred even after 4 hours (7 days) had elapsed.

[0017]

As described above, according to the present invention, a chlorine-based etching gas is caused to flow in the vacuum chamber 4 in which a pair of electrodes are installed, and high-frequency power is applied between the electrodes 5 and 6 to arrange them on one electrode. In the plasma etching process for etching the wiring material on the semiconductor wafer 12 that has been formed, a step of replacing chlorine adhering to the wiring material with fluorine of a fluorine-based gas plasma after the etching is completed, and fluorine for easily forming a polymer film. A dry etching method capable of completely preventing after-corrosion generated in a wiring material by providing a two-step post-treatment step of forming a protective film on the surface of the wiring material using plasma of a system gas Therefore, it is possible to manufacture a high-quality semiconductor device without wiring defects.

[Brief description of drawings]

FIG. 1 is a diagram for explaining post-processing of the present invention.

FIG. 2 is a diagram showing the amount of after-corrosion generated by the post-treatment of the present invention and the conventional post-treatment.

FIG. 3 is a schematic diagram of a conventional reactive ion etching apparatus.

[Explanation of symbols]

 1 Semiconductor Wafer 2 Wiring Material 3 Protective Film 4 Vacuum Chamber 5 Upper Electrode 6 Lower Electrode 7 Water Circulation Temperature Control Device 8 Impedance Matching Circuit 9 High Frequency Power Supply 10 Mass Flow Controller 11 Exhaust System 12 Semiconductor Wafer

Claims (2)

[Claims] 1. A semiconductor wafer disposed on one of electrodes, in which a chlorine-based etching gas is flown into a vacuum chamber in which a pair of electrodes is installed, and high-frequency power is applied between the electrodes to generate plasma. In the dry etching method for etching the wiring material, the step of replacing chlorine adhering to the wiring material with fluorine of fluorine-based gas plasma after the etching and the plasma of fluorine-based gas forming a Teflon-based polymer film are used. Dry etching method comprising a two-step post-treatment of the step of forming a protective film on the surface of the wiring material. 2. The dry etching according to claim 1, wherein the gas introduced into the vacuum chamber when replacing chlorine with fluorine is CF ₄ , and the gas introduced to form the protective film is CHF _3. Method.