JPH07193049A - Etching apparatus and etching method - Google Patents

Abstract

PURPOSE:To perform etching without charge-up. CONSTITUTION:An AC power supply 28, which is a plasma generating means, is connected to an electrode 22, which is arranged in a reaction tank. A material to be etched 31 is arranged at the electrode. Dry etching is performed with plasma 32 of reaction gas, which is introduced into the reaction tank 20. At this time, a pulse power supply 26 is connected to the electrode, to which the AC power supply is connected. Thus, an etching apparatus and an etching method, which apply the positive voltage pulses in etching, are obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an etching apparatus and an etching method, and more particularly to an etching apparatus and an etching method for etching an object to be etched by plasma.

[0002]

2. Description of the Related Art In recent years, with the increase in the degree of integration of semiconductor elements and the like, the densification by pattern miniaturization has rapidly progressed. Particularly, in the technical field of DRAM and the like, a processing precision of half micron or less is required, and an etching technique capable of coping with high precision processing is required. Therefore, the dry etching technique is widely used.

Generally, this dry etching technique is
A technology that selectively etches the unmasked part of the material to be processed using gas plasma. Among the etching processes, the chemical action of the active gas in the plasma and the physical action of accelerated ions Due to
It is due to both effects. By any method, as compared with the so-called wet etching technique using a chemical solution, it has excellent etching anisotropy,
It is most suitable for processing fine patterns and has become an essential technology in the semiconductor industry.

Apparatuses used in this dry etching technique are roughly classified as shown in FIGS. 5A to 5D due to the difference in electrode arrangement and the difference in plasma generation method. Figure 5
The apparatus of (a) is a "cylindrical plasma etching apparatus", FIG.
The device of (b) is a "reactive etching device", Fig. (c)
The apparatus of (1) is called a "chemical dry etching apparatus", and the apparatus of Fig. (D) is called "a microwave plasma etching apparatus".

In the cylindrical plasma etching apparatus a1 shown in FIG. 5 (a), an electrode c1 is arranged outside a reaction chamber e1, and a wafer substrate w1 to be etched is contained in a cylinder b1 arranged inside the reaction chamber e1. The surface of the wafer substrate w1 is selectively etched by performing RF discharge by an AC power source d1 connected to the electrode c1 to generate plasma.

The reactive etching apparatus a shown in FIG. 5B.
In the second example, a wafer substrate w2 is placed on a cathode electrode c2 provided in a reaction chamber e2, an AC power source d2 connected to the cathode electrode d2 performs RF discharge to generate plasma, and the wafer substrate w2 The surface is selectively etched.

The chemical dry etching apparatus a3 shown in FIG. 5 (c) generates plasma by the microwave g3 introduced from the waveguide f3, and by the active gas in the plasma,
The surface of the wafer substrate w3 placed in the reaction chamber e3 is selectively etched.

In the microwave plasma etching apparatus a4 of FIG. 5 (d), the microwave f4 generated by the magnetron electrode h4 is introduced into the reaction chamber e4 by the waveguide f4 to generate plasma, and the reaction is performed. A magnetic field is applied to the tank e4 by an electromagnet j4 to maintain plasma uniformity, and the surface of the wafer substrate w4 placed on the electrode c4 is selectively etched while an alternating voltage is applied by an AC power source d4.

[0009]

However, when etching is performed by the conventional dry etching apparatus, the material to be etched is charged up during etching.

The degree of this charge-up is, for example, MO
When an S-structure semiconductor element is etched,
Capacitor flat band voltage (Vfb) shift amount ΔV
It can be represented by fb. Specifically, in the cylindrical plasma etching apparatus of FIG. 5A, it is known that ΔVfb of 4.1 V in absolute value occurs near the center of the wafer.

If the charge-up becomes large, the characteristics of the object to be etched such as a semiconductor element are deteriorated, and finally, the object to be etched is damaged by an arc discharge, which causes many problems. Was wanted.

The present invention was created to solve the problems of the prior art described above, and the purpose thereof is to perform etching without causing the object to be etched to be charged up and therefore to damage the object to be etched. An etching device and an etching method are provided.

[0013]

In order to solve the above problems, the invention apparatus according to claim 1 is an etching apparatus for etching an object to be etched arranged in an electrode in a reaction tank by plasma of a reaction gas, wherein the electrode Is characterized by connecting a pulsed power supply for applying a positive voltage pulse to
The invention apparatus according to claim 2 is the etching apparatus according to claim 1, wherein the pulse power source generates the positive voltage pulse at a frequency of 50 Hz or higher, and the invention apparatus according to claim 3 is The etching apparatus according to claim 1 or 2, wherein generation of plasma of the reaction gas is stopped while the positive voltage pulse is applied, and the method of the invention according to claim 4 is characterized in that: An etching method of etching an object to be etched arranged on an electrode by plasma of a reaction gas, wherein a positive voltage pulse is applied to the electrode, and the method of the invention of claim 5 is the etching method of claim 4. The positive voltage pulse is applied at a frequency of 50 Hz or higher, and the invention method according to claim 6 is the method according to claim 4 or claim 5. In the process of etching, the period of the positive voltage pulse is generated is characterized by stopping the generation of the plasma.

[0014]

The principle of the present invention will be described with reference to the drawings by taking the case of generating plasma by a high frequency power source as an example. FIG. 4A is a diagram schematically showing a state in which the object to be etched is dry-etched. 1 is a substrate such as a silicon wafer or a glass substrate, and an insulating film 2 is formed on the surface of the substrate 1.
And a conductive film 3 are sequentially formed, and a patterned resist film 4 is formed on the surface of the conductor 3, and the conductive film 3 is dry-etched by using this as a protective film.

The etching apparatus used for this dry etching has an anode electrode 8 that is a first electrode and a cathode electrode 6 that is a second electrode.
An AC power source 5 is connected between the cathode electrode 6 and the cathode electrode 6, and the anode electrode 8 is connected to the ground 10 to have a ground potential.

The substrate 1 is placed on the cathode electrode 6 and a reaction gas is introduced into a reaction tank (not shown),
When the AC power supply 5 set to the frequency of 56 MHz is activated, plasma 9 of the reaction gas is generated.

Then, the substrate 1 of the plasma 9
Ions of the reaction gas are supplied to the conductive film 3 from the ion sheath 7 located near the ion conductive layer 7, and dry etching is started.

At this time, the frequency of the AC power source 5 is high,
Further, the mobilities of the ions of the reaction gas and the mass of the electrons are significantly different due to the difference between the masses of the ions.
An electron cloud is generated in the vicinity of the conductive film 3 arranged above, whereby the cathode electrode 6 is self-biased, and in many cases the potential shifts to the negative side. At this time, when the substrate 1 is an insulator, since the substrate 1 and the insulating film 2 are present between the conductive film 3 and the cathode electrode 6, the conductive film 3 is charged up to a positive potential. Resulting in. Then,
The resist film 4 and the substrate 1 located on the conductive film 3 are charged up to a positive potential.

Such a charge-up phenomenon occurs when the AC power source has a high frequency of 200 kHz or more, and the charge-up phenomenon is about 1
This is a phenomenon commonly observed in a dry etching apparatus using a frequency of 3.56 MHz.

When this charge-up progresses, discharge may occur between the cathode electrode 6 charged to a negative potential and the substrate 1 charged to a positive potential on the end face of the substrate 1. Further, in the central portion of the substrate 1, a creeping discharge is generated between the resist film 4 charged up to a positive potential and the conductive film 3 charged to a negative potential, which grows to reach an arc discharge. When these discharges occur, the device is often destroyed, resulting in a defective product.

Even when creeping discharge does not occur, a portion with a small impedance locally occurs as the etching progresses, and arc discharge occurs at this portion.
Even if the arc discharge is not reached, the function of the element may deteriorate.

FIG. 4B is a diagram showing an electrical principle by which the present invention can eliminate such a charge-up phenomenon.

Vcathode is the waveform of the AC voltage applied to the cathode electrode 6, and has the magnitude of the voltage indicated by Vp-p. When a positive voltage pulse having a waveform indicated by Vpulse is applied to this Vcathode, a current such as Icathode flows corresponding to the positive voltage pulse. This Icathode
Is a current flowing in a direction that eliminates the charge-up of the object to be etched, so that the charge-up of the substrate 1, the insulating film 2, the conductive film 3, and the resist film 4 is removed.

The principle of such charge-up elimination is as follows.
The same applies when etching is performed by generating plasma with a high frequency power source, when plasma is generated with a direct current power source, and when plasma is generated with a microwave.

[0025]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1A shows a first embodiment of the apparatus of the present invention, which is an etching apparatus for performing reactive etching.

With reference to FIG. 1A, reference numeral 20 is a reaction tank, and in the reaction tank 20, a first electrode 21 and a second electrode 22 are provided.
Is provided, one end of an AC power supply 28 of 13.56 MHz is connected to the second electrode via a blocking capacitor 25, the other end of the AC power supply 28 and the first electrode 21 are connected to the ground 24, and ground potential is established. It is the etching device.

An object to be etched 31 is placed on the second electrode, a reaction gas is introduced into the reaction tank 20, a plasma 32 is generated by starting the AC power supply 28, and dry etching is performed by the plasma.

One end of the pulse power supply 26 is connected to the filter 27.
The second end is connected to the second electrode 22 through the other end, the other end is connected to the ground 24, and a positive voltage pulse is applied to the second electrode.

FIG. 1B shows an etching apparatus according to the second embodiment of the present invention.

As shown in FIG. 1 (b), a reaction tank 40 is provided with a first electrode 41 and a second electrode 42, and a blocking capacitor 45 is provided to the second electrode for 13.56M.
Connect one end of the AC power supply 48 of
And the other end of the first electrode 41 to the ground 44 to connect them to the ground potential.
Is an etching apparatus in which a reaction gas is introduced into the reaction tank 40, plasma 52 is generated by activation of the AC power supply 48, and dry etching is performed by the plasma, which is shown in FIG. 1A. The difference from the apparatus is that the object to be etched 5 is placed on the first electrode at ground potential.
1 is located.

Similar to the first embodiment, the pulse power source 4
6 through one end of the second electrode 42 through the filter 47.
And the other end is connected to the ground 44, and a positive voltage pulse is applied to the second electrode.

FIG. 1C shows an etching apparatus according to the third embodiment of the present invention. The etching apparatus shown in FIG. 1C is a case where the present invention is applied to a magnetron RIE type apparatus.

With reference to FIG. 1C, 61 is a magnetron which is a plasma generating means, and the microwave 62 generated by the magnetron 61 is guided into the reaction tank 70 by the waveguide 63. At this time, since a magnetic field orthogonal to the electric field is given by the solenoid coil 64, the electrons can perform a cycloid motion and generate a high density plasma 82 even under a low pressure of about 1 Pa.

A third electrode 73 is provided in the reaction tank 70, and the object to be etched 8 is placed on the third electrode 73.
1 is arranged and the reaction gas 7 introduced from the gas introduction hole 75
The plasma 82 of No. 6 performs reactive ion etching of the etching object 81.

One end of a 13.56 MHz AC power supply 88 is connected to the third electrode 73 through a blocking capacitor 85, and the other end is connected to the ground 84 and is at ground potential.

Further, one end of a pulse power supply 86 is connected to the third electrode 73 through a filter 87, the other end is connected to the ground 84, and a positive voltage pulse is applied to the third electrode. Is configured.

Specific examples of the setting conditions of the pulse power supplies 26, 46 and 86 include a pulse frequency of 10 kHz, a pulse application time of 10 μsec, and an applied voltage of 10 to 30 V.

FIG. 2 shows the pulse power supplies 26, 46, 86.
Frequency and the flat band voltage of the MNOS capacitors arranged in the objects 31, 51, 81 to be etched.
The relationship between (Vfb) and the shift amount ΔVfb is shown. Frequency is 50
It can be seen that ΔVfb can be reduced above Hz. Therefore, when the positive voltage pulse is applied at a frequency of 50 Hz or higher, the charge-up is eliminated and no damage is seen on the etching target.

The reaction gas at this time was a mixture of CF ₄ gas and O ₂ gas, the flow rate was 300 SCCM, and the pressure was 20 mTorr.
And the rf power (rf-Power density)
y) was 1 W / cm ² .

The relationship between the rf power and the shift amount ΔVfb of the flat band voltage is shown in FIG. 3 (a). The curves L1 and L2 are the case of the conventional etching in which the positive voltage pulse is not applied, and when the rf power becomes large, Δ
The absolute value of Vfb also becomes large.

The curves L3 and L4 are the case of etching by the device of the present invention, and it can be seen that when the positive voltage pulse is applied, ΔVfb does not increase even if the rf power is increased.

The curves L1 and L3 have a pressure of 20 mTor.
r, the curve L2 and the curve L4 are measured values at a pressure of 50 mTorr, and the reaction gas at this time is CF ₄ gas and O ₂ gas.
A mixture of (10%) was used. Further, the pulse frequency of the pulse power supplies 26, 46, 86 for applying the positive voltage pulse is 10
Etching was performed with the kHz and pulse peak value set to 20V.

As described above, as a result of preventing the charge-up of the object to be etched, the number of particles adhering to the object to be etched 31, 51, 81 due to static electricity is drastically reduced. In FIG. 3B, the number of etching executions (number of Runs) and
The relationship with the number of particles of φ0.3 μ or more attached to the object to be etched is shown.

Curve L11 is for the prior art etching and curve L12 is for the etching according to the device of the invention. According to the present invention, it can be seen that the number of particles can be reduced. The measured area of the object to be etched is 7
It was 00 cm ² , and at this time, the measurement was performed after opening to the atmosphere in a class 1000 clean room.

It has been confirmed that when the generation of plasma is stopped when a positive voltage pulse is applied, charge-up can be eliminated particularly effectively.

In the above embodiments, the pulse power supply and the AC power supply are connected to the ground to set the ground potential, but this ground potential is a relative one that can be changed depending on where the reference potential is set. For example, it may be the earth potential which is the potential of the earth, or a potential obtained by applying a DC bias voltage to the potential. Further, the present invention is not limited to the case where the AC power source and the pulse power source are connected to the same potential, and an etching apparatus and an etching method for applying a DC bias voltage to either one or both are also included in the present invention. Be done.

FIG. 6A shows a TCP (transformer coupled p).
An example in which the present invention is applied to a laser device is shown.

With reference to FIG. 6A, reference numeral 109 is a high frequency power source which is a plasma generating means and generates high density plasma 102 through the dielectric plate 100. Etching object 1
01 is placed on the third electrode 103, and the high frequency power supply 108 is connected to the third electrode 103. A pulse power supply 106 is connected to the third electrode via a filter 107.

FIG. 6B shows an embodiment in which the present invention is applied to a helicon plasma etching apparatus. Figure 6 (b)
With reference to, 119 is a coil that is a plasma generating means and generates high density plasma 112. The object to be etched 111 is placed on the third electrode 113.
A high frequency power supply 118 is connected to the electrodes. This third
A pulse power supply 116 is connected to the electrodes via a filter 117.

In both cases of FIGS. 6 (a) and 6 (b), it is possible to eliminate the charge-up of the objects to be etched 101, 111 by applying a pulse by the pulse power supplies 106, 116.

It is needless to say that the present invention is not limited to the case where plasma is generated by a high frequency power supply or microwaves, but can be applied to a plasma excitation means such as induction excitation or an etching apparatus which generates plasma by a DC power supply. Yes.

[0052]

According to the present invention, the charge-up of the object to be etched can be eliminated during etching, so that the object to be etched is not damaged or damaged.

Further, since the adhesion of particles can be prevented, the product yield can be improved.

[Brief description of drawings]

FIG. 1 (a) is a first embodiment of the device of the present invention, (b) is a second embodiment, and (c) is a third embodiment.

FIG. 2 is a graph showing the relationship between the frequency of the pulse power supply of the present invention and the shift amount of the flat band voltage.

3A is a graph showing a relationship between an rf power and a flat band voltage shift amount, and FIG. 3B is a graph showing a relationship between the number of Runs and the number of adhered particles.

FIG. 4A is a diagram showing a principle that charge-up occurs in an object to be etched, and FIG. 4B is a diagram showing a principle of eliminating charge-up according to the present invention with a current waveform.

FIG. 5 is a diagram showing various etching apparatuses according to the prior art.

6A is a fourth embodiment of the present invention, and FIG. 6B is a fifth embodiment.

[Explanation of symbols]

21, 51 ... First electrode 22, 52 ... Second electrode 73, 103, 113 ... Third electrode 20, 40, 7
0 ... Reactor 26, 46, 86, 106, 116 ... Pulse power supply 28, 48, 88 ... AC power supply 31, 51, 81 ...
... Etching object 32, 52, 82, 102, 112 ... Plasma of reaction gas 61, 109, 119 ... Plasma generating means

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hisami Nakamura 523 Yokota, Yamatake-cho, Sanmu-gun, Chiba Japan Vacuum Technology Co., Ltd. Chiba Institute for Super Materials (72) Inventor Kafumi Ota 523 Yokota, Yamatake-cho, Sanmu-gun, Chiba Prefecture Japan Vacuum Technology Co., Ltd. Chiba Institute for Super Materials

Claims (6)

[Claims] 1. An etching apparatus for etching an object to be etched placed in an electrode in a reaction tank by plasma of a reaction gas, wherein a pulse power source for applying a positive voltage pulse is connected to the electrode. 2. The etching apparatus according to claim 1, wherein the pulse power supply generates the positive voltage pulse at a frequency of 50 Hz or higher. 3. The etching apparatus according to claim 1, wherein the plasma generation of the reaction gas is stopped while the positive voltage pulse is being applied. 4. An etching method for etching an object to be etched arranged in an electrode in a reaction tank by plasma of a reaction gas, wherein a positive voltage pulse is applied to the electrode. 5. The etching method according to claim 4, wherein the positive voltage pulse is applied at a frequency of 50 Hz or higher. 6. The etching method according to claim 4, wherein the generation of the plasma is stopped while the positive voltage pulse is being generated.