JP2624103B2 - Magnetron RIE dry etching method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to dry etching using magnetron RIE, and more particularly to a method for performing metal etching.

[0002]

2. Description of the Related Art FIG. 6 shows a conventional metal-based etching apparatus using a magnetron RIE. 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 placed in the cathode 2, in the upper part of the chamber 1 and in the side of the chamber 1.
It is installed in three places. The magnetic field B acts in the direction shown in FIG. 6 and has a strength of about 100 Gauss at the wafer surface.

[0003] Cl ₂ , CF ₄ , and N ₂ are introduced through a gas inlet 7 and exhausted by an exhaust pump 6 so as to maintain the pressure in the chamber 1 at 35 Torr.

[0004] Next, the RF signal from the RF oscillator 5 is applied to the cathode 2.
A microwave of 3.56 MHz is applied. This allows
Cl ₂ , CF ₄ , and N ₂ are converted into plasma by receiving microwave energy, and are activated by receiving energy from a magnetic field.

[0005] Before etching the semiconductor wafer 4, FIG.
It has a shape as shown in FIG. An SiN film 16 is provided on the Si substrate 11 at about 1000 Å,
A Ti film 12 and a Pt film 13 are provided thereon with a thickness of 500 angstroms. Further, an Au film 14 on which selective plating has been performed is provided on about 5000 angstroms.

The plasmanized Cl ₂ and CF ₄ do not react with Au, but react with Ti and Pt to etch away Ti and Pt other than immediately below Au.

[0007]

In the conventional magnetron RIE metal etching apparatus, as shown in FIG. 7 (B), a metal residue 17 is formed on the step portion of the Si substrate 11, thereby causing a short circuit in the device manufactured. There was a disadvantage that it would. This is because if the dry etching has a strong anisotropy, the side portions are hardly 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 the dry etch is weakened and becomes close to isotropic, so that the metal residue 17 does not occur.

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

The deposit is a polymer containing Ti or Pt, and if it adheres, it is difficult to remove the Si substrate 11 without damaging it.

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

Although not a magnetron RIE, there is the following conventional example. That is, JP-A-2-3096
In Japanese Patent Publication No. 31, a high-frequency discharge is generated between parallel plate electrodes, and when etching polycrystalline Si on a semiconductor wafer on one of the electrodes, etching is performed by periodically repeating generation and stop of the high-frequency discharge. 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 for performing dry etching without generating a metal-based deposit or reattachment on a wafer.

[0014]

In order to achieve the above object, a magnetron RIE dry etching method according to the present invention converts a reactive gas into a plasma by applying a microwave, activates the reactive gas by applying a magnetic field, and converts the reactive gas into a plasma. In the magnetron RIE dry etching method for performing etching, microwave input and stop are periodically repeated , and the microwave input time is c.
The metal gas concentration in the space very close to the wafer surface
Set to a time shorter than the critical concentration to start
And the microwave stop time is that the plasma disappears
Time when the gas on the wafer surface can be replaced.
Irrespective of whether the microwave is turned on or off,
Is applied.

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 applying a microwave and activated by applying a magnetic field to etch a metal. the input amount of increase or decrease of the wave be those periodically repeating performed, micro
Reduce the amount of microwave input by increasing the steady-state supply time of the wave.
It is set to be shorter than the supply time.

[0016]

In the etching apparatus of the present invention, the magnetron R
When performing metal etching in IE, RF
The input and stop of the microwave applied from the oscillator to the cathode, or the increase and decrease of the input amount of the microwave are performed at a specific cycle.

[0017]

Embodiments of the present invention will be described below.

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

In FIG. 1, the chamber 1 is evacuated to 5 × 10 ⁻⁷ Torr by an exhaust pump 6. S
The i-wafer 4 is placed on the cathode 2. Magnetic material 3
Are provided at three locations inside the cathode 2, at the top of the chamber 1, and at the side of the chamber 1. The magnetic field B acts in the direction shown in FIG. 1 and has a strength of about 100 Gauss at 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 that the pressure in the chamber 1 is maintained at 35 mTorr.

Next, the cathode 2 receives 1
A microwave of 3.56 MHz is applied. This allows
Cl ₂ , CF ₄ , and N ₂ are turned into plasma by receiving microwave energy. Further, it is activated by receiving energy from a magnetic field. At this time, as shown in FIG.
The control unit 8 turns on / off the power of the RF oscillator 5. When 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 application of the RF power of 600 W is repeated for 600 msec.

Conventionally, as shown in FIG. 3A, when an 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
When N is set (a), the SiN film 16 on the Si substrate 11 is
The upper Pt 13 is etched by Cl ₂ and CF ₄ , which have been turned into plasma and activated immediately below the Au electrode 14.

The etched Pt combines with Cl, C, F and the like to form a gas. At this time, in the space very close to the wafer surface, the concentration of the metal gas containing Pt increases as the etching of Pt proceeds ((a) in FIG. 4A).

Next, when the RF power is cut (FIG. 3)
(B) (b)), the plasma energy of the gas in the chamber is weakened, and the etching of Pt is almost stopped. However, since the energy from the magnetic field is supplied as it is, the plasma is generated in the chamber 1 although weak.

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

Next, when the RF power is applied again, the concentration of the metal gas on the wafer surface increases, but when the RF power is cut off, the concentration of the metal gas on the wafer surface decreases. As described above, the concentration of the gas containing metal in the space very close to the wafer surface is suppressed to a very low concentration due to the intermittent RF. Therefore, etching can be performed without re-adhering the metal-based material to the wafer surface.

At this time, the ON time of the RF power is shorter than the time during which the metal gas concentration in a space very close to the wafer surface reaches the critical concentration for starting the deposition.

The OFF time is a time during which the plasma is not extinguished and the gas on the wafer surface can be replaced.

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

Further, since the 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 a metal is etched by a magnetron RIE dry etch, RF power is turned on / off or power is increased / decreased at a certain cycle, so that the side wall of the step portion of the wafer is formed. Metal deposits (re-adhesion) do not occur on the wafer in a pressure range where no metal residue occurs.

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

[Brief description of the 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.

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

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

FIG. 5 shows the ON / OFF state of RF power according to another embodiment of 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]

 DESCRIPTION OF SYMBOLS 1 Chamber 2 Cathode 3 Magnetic body 4 Si wafer 5 RF oscillator 6 Exhaust pump 7 Gas inlet 8 RF control part 11 Si substrate 12 Ti 13 Pt 14 Au 15 Deposited product 16 SiN film 17 Metal remaining

Claims (2)

(57) [Claims] In a magnetron RIE dry etching method in which a reactive gas is turned into plasma by application of a microwave and activated by the application of a magnetic field to etch a metal, the input and stop of the microwave are periodically repeated. also performed
Therefore , the microwave input time is limited to the space very close to the wafer surface.
Metal gas concentration in the furnace reaches the critical concentration to start depot
The microwave is stopped for a period of time shorter than
Set the time to allow gas replacement on the wafer surface
The magnetic field energy is marked regardless of whether the microwave is input or stopped.
Magnetron RIE dry etching method which is characterized in that pressure. 2. A magnetron RIE dry etching method in which a reactive gas is turned into plasma by application of a microwave and activated by the application of a magnetic field to etch a metal, wherein the input amount of the microwave is periodically increased and decreased. Do
The microwave supply time and the microwave input amount.
A magnetron RIE dry etching method characterized in that the supply time is set shorter than the supply time .