JPH06163468A - Magnetron rie dry etching method - Google Patents

Abstract

PURPOSE:To carry out a dry etching process without producing metal deposits or redeposits on a wafer by a method wherein the input and stoppage of microwaves are periodically repeated. CONSTITUTION:Reactive gas is turned into plasma by microwaves and activated by a magnetic field to etch metal. In a magnetron RIE dry etching method as mentioned above, an input and stoppage of microwaves are periodically repeated. Or, microwaves are periodically increased or decreased in input power. For, instance, microwaves outputted from an RF oscillator 5 are supplied to a cathode 2 to turn Cl2, CF4, and N2 into plasma, which is activated by a magnetic field. The power of the RF oscillator 5 is turned ON or OFF by an RF controller 8, and an operation where an RF power of 600W is applied to the cathode 2 for 600ms and then shut off for 400ms is repeatedly carried out.

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 using magnetron RIE, and more particularly to a method for performing metal etching.

[0002]

2. Description of the Related Art As a conventional metal type etching apparatus using a magnetron RIE, there is one as shown in FIG. As shown in FIG. 6, the chamber 1 is evacuated to 5 × 10 ⁻⁷ Torr by the exhaust pump 6.
The Si wafer 4 is placed on the cathode 2. The magnetic material 3 is in the cathode 2, and is located on the upper side of the chamber 1 and the side surface of the chamber 1.
It is installed in several places. The magnetic field B acts in the direction shown in FIG. 6 and has a strength of about 100 gauss on the wafer surface.

Cl ₂ , CF ₄ and N ₂ are introduced from the gas inlet 7 and exhausted by the exhaust pump 6 so as to keep the pressure in the chamber 1 at 35 Torr.

Next, the cathode 2 has an RF oscillator 1
A microwave of 3.56 MHz is applied. This allows
Cl ₂ , CF ₄ , and N ₂ are activated by receiving the energy of microwaves to be turned into plasma and further receiving energy from the magnetic field.

The semiconductor wafer 4 is shown in FIG.
It has a shape as shown in FIG. The SiN film 16 is provided on the Si substrate 11 to have a thickness of about 1000 angstroms.
A Ti film 12 and a Pt film 13 are provided thereon with a thickness of 500 angstroms. Further, an Au film 14 which is selectively plated is provided thereon with a thickness of about 5000 angstroms.

Cl ₂ and CF _{4 which} have been turned into plasma do not react with Au but react with Ti and Pt and etch away Ti and Pt except under Au.

[0007]

In this conventional magnetron RIE metal etching apparatus, as shown in FIG. 7 (B), a metal residue 17 is generated in the step portion of the Si substrate 11, which causes the device to be short-circuited. There was a drawback that it would end up. This is because if the dry etching has a strong anisotropy, the side surface is less likely to be etched.

In order to eliminate the metal residue 17, there is a method of increasing the pressure in the chamber during etching. As a result, the anisotropy of dry etching is weakened and is nearly isotropic, and the metal residue 17 does not occur.

However, instead of this, as shown in FIG. 7C, the generated deposit 15 was generated on the SiN film 17, resulting in poor reliability and poor appearance. This is because Ti and Pt react with Cl, C, and F to form a gas containing Ti and Pt during etching, and are etched. However, if the pressure during etching is high, the gas is very close to the wafer surface. , Ti and Pt
When the gas concentration including is too high with etching and exceeds a certain critical point (critical point x in FIG. 4B), redeposition starts to occur (FIG. 2B).

The deposit is a polymer containing Ti or Pt. If this deposit adheres, it is difficult to remove it without scratching the Si substrate 11.

Since this metal-based depot contains metal, it causes a short circuit, a leak in the circuit, and a reliability problem.

Although not a magnetron RIE, there are the following conventional examples. That is, Japanese Patent Laid-Open No. 2-3096
In Japanese Patent Laid-Open No. 31-31, a high-frequency discharge is generated between parallel plate electrodes, and when polycrystalline Si on a semiconductor wafer is etched on one electrode, the high-frequency discharge is generated and stopped periodically to perform etching. It is disclosed. The purpose is to control the tapered etching cross-sectional shape.

An object of the present invention is to provide a magnetron RIE dry etching method in which dry etching is carried out without producing metal-based deposits or redeposits on a wafer.

[0014]

In order to achieve the above-mentioned object, a magnetron RIE dry etching method according to the present invention is performed by applying a microwave to turn a reactive gas into a plasma and applying a magnetic field to activate the reactive gas. In a magnetron RIE dry etching method for performing etching, microwave input and stop are periodically repeated.

Further, the magnetron RIE dry etching method according to the present invention is a magnetron RIE dry etching method in which a reactive gas is plasmatized by application of microwaves and activated by application of a magnetic field to etch metal. The amount of wave input is increased and decreased periodically.

[0016]

In the etching apparatus of the present invention, the magnetron R
When performing metal etching in IE, RF
The microwave applied to the cathode from the oscillator is input or stopped, or the amount of microwave input is increased or decreased at a specific cycle.

[0017]

EXAMPLES Examples of the present invention will be described below.

(Embodiment 1) FIG. 1 is a block diagram showing Embodiment 1 of the present invention.

In FIG. 1, the chamber 1 is evacuated by an exhaust pump 6 to a vacuum of 5 × 10 ^-7 Torr. S
The i-wafer 4 is placed on the cathode 2. Also magnetic material 3
Are installed at three locations inside the cathode 2, the upper part of the chamber 1, and the side surface of the chamber 1. The magnetic field B acts in the direction shown in FIG. 1 and has a strength of about 100 Gauss on the wafer surface.

Cl ₂ , CF ₄ , and N ₂ are introduced through the gas inlet 7, and the exhaust pump 6 exhausts so that the pressure in the chamber 1 is maintained at 35 mTorr.

Next, the cathode 2 is fed from the RF oscillator 5 to 1
A microwave of 3.56 MHz is applied. This allows
Cl ₂ , CF ₄ , and N ₂ are converted into plasma by receiving the energy of microwaves. Furthermore, it receives energy from the magnetic field and is activated. At this time, as shown in FIG.
The adjusting unit 8 turns on / off the power of the RF oscillator 5. After the RF power of 600 W is applied to the cathode for 600 msec, the RF power is cut off for 400 msec, and the RF power of 600 W is applied again for 600 msec.

Conventionally, as shown in FIG. 3 (A), after RF power of 600 W was applied, the power was kept applied until the end of etching.

As shown in FIG. 2A, the RF power is set to O
When set to N (a), the SiN film 16 on the Si substrate 11
The upper Pt 13 is etched by plasma-activated and activated Cl ₂ and CF ₄ except immediately below the Au electrode 14.

The etched Pt is combined with Cl, C, F, etc. to form a gas. At this time, in a space very close to the wafer surface, the Pt-containing metal gas concentration increases with the progress of Pt etching ((a) in FIG. 4A).

Next, when the RF power is cut off (see FIG.
In (b) of (B), the plasma energy of the gas in the chamber weakens, and etching of Pt almost stops. However, since the energy from the magnetic field is supplied as it is, plasma is still generated in the chamber 1 although it is weak.

Since Pt etching stops on the wafer surface, the Pt gas concentration on the wafer surface decreases (FIG. 2 (A) (b) and FIG. 4 (A) (b)).

Next, when the RF power is turned on again, the wafer surface metal gas concentration rises, but when the RF power is cut off, the wafer surface metal gas concentration decreases. Thus, due to the intermittent RF, the metal-containing gas concentration in the space very close to the wafer surface is suppressed to a very low concentration. Therefore, the etching can be performed without redeposition of the metal-based substance on the wafer surface.

At this time, the ON time of the RF power is shorter than the time when the metal gas concentration in the space very close to the wafer surface reaches the critical concentration at which the deposition starts.

The OFF time is the time during which the plasma on the wafer surface can be replaced without extinguishing the plasma.

(Embodiment 2) In this embodiment, instead of turning on / off the RF power, the power at the time of ON is 600 W.
Then (FIG. 5 (A)), the RF power is set to 300 W instead of being turned off (FIG. 5 (B)), and instead, the ON time is shortened so that the same effect can be obtained. is there.

Further, since plasma is not turned off, there is an advantage that more stable etching can be obtained.

[0032]

As described above, according to the present invention, when the metal is etched by the magnetron RIE dry etching, the RF power is turned on / off at a certain cycle or the power is increased / decreased, so that the side wall of the wafer step portion is etched. The metal-based deposition (re-deposition) does not occur on the wafer within the pressure range where no metal residue occurs.

Further, during the RF power cutting period, the gas on the wafer surface can be replaced, but the plasma is not extinguished, so stable etching can be performed.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a magnetron RIE etching apparatus of the present invention.

FIG. 2A is a diagram showing a metal etching model of the present invention, and FIG. 2B is a diagram showing a conventional metal etching model.

FIG. 3A is an RF power ON / OFF timing chart of the present invention, and FIG. 3B is a conventional RF power ON / OFF timing chart.
It is an OFF timing chart.

FIG. 4A is a diagram showing a relationship between a wafer surface metal gas concentration and time of the present invention, and FIG. 4B is a diagram showing a conventional wafer surface metal gas concentration and time relationship.

FIG. 5 is a diagram illustrating another example of turning on / off of RF power according to the present invention
It is an OFF timing chart.

FIG. 6 is a configuration diagram showing a conventional magnetron RIE etching apparatus.

FIG. 7 is a diagram showing a problem of conventional metal etching.

[Explanation of symbols]

 1 Chamber 2 Cathode 3 Magnetic Material 4 Si Wafer 5 RF Oscillator 6 Exhaust Pump 7 Gas Inlet 8 RF Adjusting Part 11 Si Substrate 12 Ti 13 Pt 14 Au 15 Product Deposit 16 SiN Film 17 Metal Remaining

Claims (2)

[Claims] 1. In a magnetron RIE dry etching method in which a reactive gas is turned into plasma by application of microwaves and activated by application of a magnetic field to perform metal etching, microwave input and stop are periodically repeated. A magnetron RIE dry etching method characterized by being performed. 2. A magnetron RIE dry etching method in which a reactive gas is made into plasma by application of microwaves and activated by application of a magnetic field to perform metal etching, and increase / decrease of microwave input amount is periodically repeated. And a magnetron RIE dry etching method.