JP2569019B2 - Etching method and apparatus - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the manufacture of a semiconductor device using low-temperature plasma, and more particularly to an etching method suitable for performing an etching process at high speed and uniformly, and an etching method thereof. Related to the device.

[Conventional technology]

Devices that use low-temperature plasma can be roughly classified into those using a technique of generating a plasma by applying a high-frequency voltage of about 10 KHz to 30 MHz to one of the parallel plate electrodes in a vacuum (Semiconductor Research 18, P121 to P170). , Semiconductor Research 19; P225-P267)
And a technique using a technique of introducing a 2.45 GHz microwave into a vacuum chamber to generate plasma. Conventionally, the technique using parallel plate electrodes has been mainly used among them.

On the other hand, with the miniaturization of semiconductor devices, there has been a problem that the device characteristics are affected by the impact of ions generated during plasma processing. Further, it is required to increase the processing speed in order to improve the processing capacity.

When increasing the processing speed, simply increasing the density of plasma or the concentration of radicals (active particles immediately before ionization) is not sufficient. In dry etching by plasma treatment and plasma CVD, ion energy plays an important role. In the case of dry etching, if the energy of the ions is too large, the underlying film is shaved or affects the crystal structure, and the device characteristics are degraded. On the other hand, if it is too small, the polymer formed on the etched surface will not be sufficiently removed, and the etching rate will decrease. Or, conversely, a protective film made of a polymer is not formed, and the side surface of the pattern is etched, which causes a problem that the dimensional accuracy of the pattern deteriorates.

In plasma CVD, too, the ion energy affects the film formation such that the film composition becomes coarse when the energy of the ions is weak, and becomes dense when the energy is strong.

Therefore, increasing the density of the plasma and appropriately controlling the ion energy are indispensable for future plasma processing. As known examples, JP-A-56-13480, JP-A-56-96841
A method using a microwave as shown in FIG.

When generating microwave plasma, even if the microwave generated by the magnetron is radiated to the low pressure plasma processing chamber, sufficient energy is not supplied to the electrons due to the insufficient electric field strength of the microwave, and the plasma is generated. It is difficult to generate. Therefore, in order to generate plasma by microwaves, there is a method of supplying energy to electrons by matching the frequency of the microwave with the frequency of the cyclotron, which rotates the plane perpendicular to the magnetic field, and supplying energy to the electrons. There are two methods of supplying the energy to the electrons by radiating the microwaves to the resonator to increase the amplitude of the microwave and increasing the electric field strength. The former is disclosed in JP-A-56-13480, and is called a microwave with magnetic field or an ECR (Electron Cyclotron Resonance) method. The latter is disclosed in JP-A-56-96841.

Since the plasma generated by the microwave is supplied with energy directly to the electrons from the microwave, the voltage between the sheaths formed between the plasma and the substrate hardly changes. Therefore, by applying a high-frequency voltage to the electrode on which the substrate is mounted and arbitrarily controlling the inter-sheath voltage, it is possible to control the plasma density and the appropriate ion energy necessary for high-speed operation.

[Problems to be solved by the invention]

I mentioned earlier that the energy of ions plays an important role in plasma processing such as etching.

In the prior art, in the ECR system, as shown in JP-A-56-13480, when a high-frequency voltage is applied to an electrode on which a substrate is mounted, there is no ground electrode on the opposite side of this electrode,
The high-frequency current flows between the surrounding processing chambers, and the effect of ion energy on the substrate is strong around the substrate and weak at the central portion, so that the entire substrate cannot be processed under uniform conditions.

In the method using a cavity resonator, plasma is generated in the resonator, so when plasma is generated,
Since the wavelength of the microwave changes depending on the density of the plasma, there is a problem that the resonance condition is not satisfied and the plasma becomes unstable. That is, since the resonance condition is satisfied until the plasma is generated, the electric field strength of the microwave is increased and the plasma is generated. However, when plasma is generated and the plasma density is increased, the wavelength of the microwave changes and the resonance condition is no longer satisfied, and the electric field intensity decreases. Then, the supply of energy to the electrons decreases, and the plasma density decreases. When the plasma density decreases, the resonance condition is satisfied, and the plasma density increases again. Due to such a phenomenon, it has been difficult to generate plasma stably.

In addition, if a high-frequency voltage application electrode is provided in the cavity resonator to control the energy of ions incident on the substrate from the plasma, microwave reflection occurs and the plasma becomes more unstable. was there.

An object of the present invention is to generate stable and high-density plasma and to make the energy of ions incident on the substrate uniform over the entire substrate.

[Means for solving the problem]

Generally, when a microwave travels in a waveguide or a cavity that is considered to be a kind of waveguide, a current corresponding to an electric field and a magnetic field flows on the surface of the waveguide.

Therefore, if a slit is provided in a part of the waveguide so as to cross this current, charges accumulate at both ends of the slit, and this changes with the progress of microwaves. Is radiated to the outside of the device.

The object is to supply microwaves to the plasma processing chamber through slits provided in the waveguide according to this principle, or to connect the waveguide to a cavity resonator and apply microwaves to the cavity resonator. This is achieved by providing a slit for emitting light and supplying microwaves to the plasma processing chamber.

[Action]

In the conventional ECR method, microwaves are directly radiated from the opening of the waveguide to the plasma processing chamber. Therefore, if an earth electrode is provided between the plasma processing chamber and the opening of the waveguide, the microwave is reflected by the arm electrode and cannot be supplied to the plasma processing chamber.

According to the present invention, the end face of the waveguide is closed, and a slit for radiating microwaves is provided on this end face. If necessary, the end face of the waveguide was set to the ground potential.

The opening area of the slit can be reduced to about 1/3 of the entire end face of the waveguide. Therefore, when a high-frequency voltage is applied to the electrode on which the substrate is mounted, the high-frequency current flows evenly between the end face of the waveguide and the electrode, and the effect of ions can be generated uniformly over the entire surface of the substrate. In addition, a sufficient amount of microwaves can be supplied through the slit, and high-density plasma can be generated.

On the other hand, when a cavity resonator is connected to the waveguide, a microwave whose amplitude is increased by resonance in the cavity resonator is radiated to the plasma processing chamber through the slit. Therefore, high-density plasma can be generated without having a plasma processing chamber having a cavity resonator structure as in the related art.

For this reason, the electrode structure according to the present invention is not restricted by the relationship with the cavity resonator as in the related art. Further, since no plasma is generated in the cavity resonator, there is no change in the resonance state, and the plasma can be generated stably. Further, by connecting the cavity resonator to the ground potential, a counter electrode parallel to the electrode can be formed as in the case of the ECR method, and the effect of ions can be uniformly generated on the entire substrate.

〔Example〕

Hereinafter, the first of the etching method and the apparatus according to the present invention will be described.
1 will be described with reference to FIG.

The cavity resonator 1 is a circular cavity resonator of _E01 mode,
Microwaves are supplied from the magnetron 3 through the waveguide 2. The waveguide 2 is mounted eccentrically with respect to the circular cavity resonator 1 in order to improve the coupling with the _E01 mode. On the other side of the circular cavity resonator 1, a ceramics plate 4 and a slit plate 5 are fixed. A plasma processing chamber 6 is connected underneath. In addition, it has a structure sealed in a vacuum by the ceramic plate 4.

Planar structure of the slit plate 5 whereas electric field E ₀₁ modes as shown in the second FIG. 5b, there is a slit opening annular perpendicularly. When a microwave of 2.45 GHz is used, each slit 5c has a length of 60 mm or more, which corresponds to a half wavelength of the microwave, in order to improve the radiation of the microwave from the slit.

The plasma processing chamber 6 (FIG. 1) has an electrode 7, a gas supply pipe 9,
A gas exhaust pipe 10 is provided. The electrode 7 is fixed to the plasma processing chamber 6 via an insulating material 8, and further includes a high-frequency power supply.
11 is connected.

The gas supply pipe 9 can be supplied with a set amount of plasma processing gas from a gas source (not shown).

A vacuum exhaust pump (not shown) is connected to the gas exhaust pipe 10 so that the pressure in the plasma processing chamber can be controlled at 1 to 10 ^-3 Torr.

The magnetron 3 is operated to oscillate a microwave, which is supplied to the cavity resonator 1 by the waveguide 2. The energy of the microwave whose amplitude is increased in the cavity resonator is radiated from the slit of the slit plate 5 to the plasma processing chamber. The amplitude of the microwave radiated into the plasma generation chamber is
Therefore, even if the plasma processing chamber 6 does not have the cavity resonator structure, the plasma is turned on and maintained.

A case where an etching process is performed using the above apparatus will be described. An etching gas is supplied from a gas supply pipe 9,
The gas is exhausted from the gas exhaust pipe 10 and a microwave is supplied at a constant pressure to generate plasma between the slit plate 5 and the electrode 7 by the microwave. Since the microwave acts directly on the electrons in the plasma, the potential difference between the plasma and the electrode 7 is at a level of 20 to 30V. Process wafer 1 on electrode 7
2 is placed, and a high frequency voltage is applied to the electrode 7 from the high frequency power supply 11. The electrode 7 and the slit plate 5 are installed in parallel,
The high-frequency current flows evenly between the electrode 7 and the slit 5.
Therefore, the electric field generated between the electrode and the plasma becomes uniform, and the ions of the etching gas having uniform energy on the entire surface are controlled and applied to the wafer 12 by applying a high-frequency voltage.

The ions of the etching gas and the active species (radicals) of the etching gas excited in the plasma react with the film to be processed on the wafer 12, and the etching proceeds.

At this time, since the energy of the incident ions is uniform, uniform etching can be performed on the entire surface of the wafer.

Next, in order to explain the principle of the present invention, a case where the present apparatus is applied to plasma CVD will be described. A mixed gas of SiH ₄ and N ₂ , N ₂ O is supplied from a gas supply pipe 9, N ₂ O, SiH ₄ is decomposed by plasma to generate SiO ₄ , and a film is formed on the wafer 12. Further, the film quality is controlled by the incidence of ions from the plasma. At this time, since the incident energy of ions can be equalized, a uniform film can be formed on the entire surface of the wafer.

In principle the description of the first embodiment and the present invention described above has been described microwave mode of the circular waveguide is E ₀₁ mode, the generator is not limited thereto. However slit for better efficiency is the microwave radiation in the direction perpendicular to the current flowing through the surface of the cavity resonator, in the case of H ₀₁ mode becomes the structure shown in FIG. 3, H ₁₁
In the case of the mode, the structure is as shown in FIG.

As described above, according to the present invention, the effects of ions indispensable for plasma processing can be equalized, and there is an effect that stable plasma can be generated.

Next, the principle of a method for further improving the plasma density using the present invention will be described.

In the embodiment shown in FIG. 1, since only microwaves are radiated to the plasma processing material, the density of the generated plasma is 10%.
^{If it} exceeds ¹¹ cm ^-3 , microwaves are reflected and the plasma density cannot be further increased. Plasma density of 10
If more than ¹¹ cm ^{-3 is} required, as shown in FIG.
The coil 14 generates a magnetic field 15 parallel to the microwave radiation direction.
Is provided.

In the case described in the principle of the present invention, since the amplitude of the microwave is increased by the cavity resonator 1, it is not necessary to set the state of the electron cyclotron resonance, and the magnetic field intensity is selected according to the required plasma density. be able to. Further, since the amplitude of the microwave becomes larger than that of the conventional resonance method, there is also an effect that a stable discharge can be established in a region with a higher degree of vacuum.

In FIG. 6, a case where the present invention is applied to an ashing process will be described to further explain the principle of the present invention.

In the description of the present principle, the portions having the same numbers as those shown in FIG. 1 are the same, and therefore only different portions will be described.

A mesh plate 20 is provided inside the plasma processing chamber 6, and the wafer 12 is placed on a table 21.

Oxygen gas is supplied from the gas supply pipe 9 and the magnetron 3
Is operated to supply microwaves to generate plasma between the slit plate 5 and the mesh plate 20.

Since the mesh plate 20 is sized not to transmit microwaves, plasma is trapped between the mesh plate 5 and the slit. The oxygen gas is turned into a radical state by the plasma, and is supplied onto the wafer 12 through the mesh plate 20. The resist film on the wafer is ashed by the oxygen radicals.

In the embodiments and the principle explained above, the combination of the circular cavity resonator and the slit plate has been described.
The present invention is not limited to this.

FIG. 7 shows a case where the present invention is applied to a sputtering apparatus in order to further explain the principle of the present invention.

The processing chamber 33 is made of ceramics, and the pressure in the processing chamber can be controlled to 10 ⁻⁴ Torr to 10 ⁻² Torr by a gas supply port and a gas exhaust port (not shown).

In the processing chamber 33, there are a target 34 and a wafer table 36. A high frequency power supply 35 is connected to the target, and the wafer table 36 is connected to ground. Outside the processing chamber 33, a shield chamber 40 and a rectangular ring-shaped resonator 31a are provided.

A ring resonator is a rectangular waveguide formed into a ring.
The circumference of the ring is set to an integral multiple of 1/2 of the guide wavelength. A terminal wall is provided in a part of the ring-shaped waveguide so that the phase of the resonating microwave does not shift.

FIG. 8 shows the planar structure of the ring resonator 31a. Microwaves are supplied to the resonator 31 from the magnetron 32 and the waveguide 30. Coil 3 outside shield room 40 (Fig. 7)
7. There is a coil 38, which generates a caps field 42. The shield chamber is made of aluminum or stainless steel and does not emit microwaves, but uses a material that allows magnetic fields to pass through.

An entire circumference slit 43 is provided inside the ring-shaped resonator. When the microwave is supplied to the ring-shaped resonator, the amplitude of the microwave is amplified in the resonator, and the microwave having a large amplitude is radiated into the processing chamber 33 from the slit 43.

When argon gas is introduced into the processing chamber 33 and maintained at a level of 10 ⁻³ Torr, plasma trapped in the caps magnetic field 42 is generated between the target 34 and the wafer table 36. Next, a high-frequency voltage is applied from a high-frequency power supply 35, ions of argon gas are made incident on the target, and the target material is sputtered to form a film on the wafer 39. In this method, as described in the embodiment shown in FIG. 5, stable plasma can be generated even under conditions of a higher degree of vacuum by a microwave having a large amplitude, and there is an effect that the film quality can be improved.

The system combining the ring resonator and the slit can be used not only for sputtering but also for etching and plasma CVD.

FIG. 9 shows a second embodiment of the etching method and apparatus according to the present invention. Since the basic configuration is the same as that of the sputtering apparatus shown in FIG. 7 in the description of the principle of the present invention, only different points will be described.

A lower electrode 46 and an upper electrode 45 are provided in the processing chamber 33, and the lower electrode is fixed to the processing chamber via an insulator 41, and a high-frequency power supply 47 is provided.
A higher frequency voltage can be applied. The upper electrode 45 is connected to the ground.

An etching gas is introduced, the inside of the processing chamber 33 is maintained at a pressure of 10 ⁻² Torr, and microwaves are supplied to the ring-shaped resonator 31. The amplitude of the microwave is amplified and radiated into the processing chamber from the slit 43, and a plasma is generated between the upper electrode 45 and the lower electrode 46 by the microwave.

When a high-frequency voltage is applied to the lower electrode 46, a high-frequency current flows evenly between the parallel electrodes, ions incident on the wafer 39 are accelerated by a uniform potential difference between the sheaths, and uniform etching characteristics can be obtained over the entire surface of the wafer. .

As described above, according to the present invention, when plasma is generated using microwaves, electrodes can be provided on a surface facing an electrode for processing a wafer. Therefore, uniform plasma processing can be performed. Furthermore, since the plasma processing chamber does not need to have a cavity resonator structure, there is an effect that there is no restriction on the electrode structure and the structure of the plasma processing chamber.

〔The invention's effect〕

The present invention has the effect of stabilizing the generation of plasma using microwaves.

According to the present invention, there is an effect that the apparatus configuration is not restricted by the relation with the cavity resonator. Therefore, by connecting the cavity resonator to the ground potential, a counter electrode parallel to the electrode on which the object to be processed is placed can be formed. As a result, the energy of the microwave can be propagated through the slit provided in the counter electrode, and the effect of ions and radicals generated by this energy can be uniformly applied to the object to be processed.

In addition, the effects of ions and radicals can be generated uniformly. As a result, plasma processing can be performed at a high speed with an optimum ion energy. Furthermore, a fine pattern of a semiconductor wafer can be formed with high accuracy, at high speed, and with low damage.

[Brief description of the drawings]

FIG. 1 is a perspective view of a first embodiment of the present invention, and FIG.
FIG. 3 is a plan view of a slit used in the embodiment of FIG. 2, FIG. 3 is a plan view of another embodiment of the slit of FIG. 2, FIG. 4 is a plan view of a third embodiment of the slit of FIG. FIG. 5 is a view for explaining the principle of the present invention, FIG. 6 is a sectional view of an ashing apparatus for explaining the principle when applied to an ashing apparatus for further explaining the principle of the present invention, and FIG. FIG. 8 is a cross-sectional view of a sputtering apparatus for explaining the principle when the principle of the present invention is applied to a sputtering apparatus, and FIG. 8 is a plan view of a resonator used in the sputtering apparatus of FIG.
FIG. 5 is a sectional view showing a second embodiment of the etching apparatus according to the present invention. 1 ... cavity resonator, 5 ... slit plate, 6 ... plasma processing chamber, 7 ... electrode, 11 ... high frequency power supply, 31 ... ring-shaped resonator, 33 ... processing chamber, 34 ... target , 36 ... wafer table, 35 ... high frequency power supply.

Claims (6)

(57) [Claims] 1. A microwave source, a cavity resonator for resonating a microwave supplied from the microwave source,
Slit means for radiating microwaves in the cavity resonator, and microwaves emitted from the slit means are also received in a state in which the substrate is also received and maintained at a predetermined pressure, to generate plasma, and the substrate is formed. A plasma processing chamber for processing; separating means for separating the plasma processing chamber and the cavity resonator; and high-frequency power applying means for applying high-frequency power to the substrate in the plasma processing chamber; An etching apparatus, wherein the substrate is subjected to an etching process in a state where the substrate is not provided. 2. An etching apparatus according to claim 1, wherein said substrate is installed in said plasma processing chamber so as to face said slit means. 3. The etching apparatus according to claim 1, wherein said separation means transmits said microwave. 4. The etching apparatus according to claim 1, wherein said cavity resonator has a cylindrical shape, and said slit means is provided at a bottom of said cylindrical shape. 5. A microwave generated by a microwave generation source and resonated in a cavity resonator is radiated to a plasma processing chamber maintained at a predetermined pressure by setting a substrate through a slit of the cavity resonator and irradiating a plasma. And applying a high-frequency power to the substrate to generate etching, thereby performing an etching process on the substrate without providing a magnetic field on the substrate. 6. The etching method according to claim 5, wherein a predetermined pressure in said plasma processing chamber is set to a level of 10 ⁻² Torr in said etching process.