JP2633849B2 - Plasma processing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to the manufacture of semiconductor devices using low-temperature plasma, and in particular, plasma processing suitable for high-speed processing of various technologies such as CVD, etching, sputtering, and incineration. Related to the device.

[Conventional technology]

Devices that use low-temperature plasma can be roughly classified into those using a technology that generates a plasma by applying a high-frequency voltage of about 10 KHz to 30 KHz to one of the parallel plate electrodes in a vacuum (Semiconductor Research 18, P121 to P170). , Semiconductor Research 19; P225-P267)
And a technique of introducing a 245 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 the plasma or the temperature of the 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, resulting in 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 and JP-A-56-9684
A system using a microwave as shown in 1 has been proposed.

When plasma is generated by microwaves, even if microwaves generated by the magnetron are radiated to the plasma generation chamber at low pressure, sufficient energy is not supplied to the electrons due to insufficient electric field strength of the microwaves, generating plasma. It is difficult to do that. Therefore, in order to generate plasma by microwaves, there is a method of matching the frequency of the microwave with the cyclotron frequency at which the electrons rotate on a plane perpendicular to the magnetic field and supplying energy to the electrons in a resonance state, and the method of using the microwaves as a cavity resonance There are two methods of supplying energy to electrons by radiating them to a vessel and increasing the amplitude of the microwave to increase the electric field strength. The former is JP-A-56
-13480, magnetic field microwave or E
It is called CR (Electron Cyclotron Resonance) method. The latter is disclosed in JP-A-56-96841.

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

[Problems to be Solved by the Invention] As mentioned earlier, the energy of ions plays an important role in plasma processing.

In the prior art, in the ECR method, 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 inside 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 inside the cavity resonator to control the energy of ions entering the substrate from these plasmas, microwaves will be reflected and the plasma will become more unstable. there were.

An object of the present invention is to provide a plasma processing apparatus capable of stably generating high-density plasma and making the energy of ions incident on the substrate uniform over the entire surface of the substrate.

[Means for solving the problem]

Generally, when a microwave travels in a waveguide or a cavity resonator considered to be a kind of a 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 provide a microwave processing apparatus that generates microwave power and transports the generated microwave power in a plasma processing apparatus that processes a sample by generating plasma by supplying microwave power using the above-described principle. A power supply means, a plasma chamber means for generating plasma by introducing microwave power transported by the microwave power supply means, the inside of which is maintained at a predetermined pressure, and a microwave power supply means and a plasma chamber means. A conductor having a slit-shaped opening between the microwave power supply means and the microwave chamber, which is separated from the microwave power supply means by sealing the plasma chamber means in a vacuum. Separating means provided with a film on the surface and having a plurality of openings on the side of the plasma chamber means, and a gas flow path provided in the separating means It is achieved by constituting a gas supply means for supplying a gas into the plasma chamber means through.

[Action]

The conventional ECR system radiates microwaves directly to the plasma generation chamber from the opening of the waveguide. Therefore, an earth electrode is provided between the plasma generation chamber and the opening of the waveguide. Microwaves are reflected by the ground electrode and cannot be supplied to the plasma generation 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. Also, a sufficient amount of microwaves can be supplied through the slit, and high-density plasma can be generated. At this time, since the slit is formed in a film shape on the surface of the separation means formed of a material such as ceramics having a small coefficient of thermal expansion and transmitting microwaves, the slit is thermally exposed even when exposed to the generated high-density plasma. The amount of deformation due to expansion is small, microwaves can be supplied stably through the slits, and high-density plasma can be stably generated in the plasma processing chamber.

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 emitted to the plasma generation chamber through the slit. Therefore, it is possible to stably supply microwaves through the slits formed in the conductor film as described above, without having the plasma generation chamber have a cavity resonator structure as in the related art. Can be generated stably.

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, an embodiment of the present invention will be described with reference to FIG.

The cavity resonator 1 is an _E01 mode circular cavity resonator,
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. A ceramic plate 4 is fixed to the other side of the circular cavity resonator 1. A resonator is formed on the ceramic plate 4 including a plating pattern in which a slit is formed by gold plating 5. Ceramic plate 4
Below, a plasma generation chamber 6 is connected, and has a structure sealed by a ceramic plate 4 in a vacuum.

The shape of the slit formed by plating 5 is
As shown in the figure, 5b is a portion plated with gold, and 5c is an unplated slit opening. Also with respect to the electric field E ₀₁ mode, 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 generation 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 generation 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 generation chamber can be controlled to 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 microwave energy amplified in the cavity resonator is radiated from the slit of the plating 5 into the plasma generation chamber. Since the amplitude of the microwave radiated into the plasma generation chamber is large in the cavity resonator 1, the plasma is turned on and maintained even if the plasma generation chamber does not have a cavity resonator structure.

The application of this embodiment 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 SiOx,
A film is formed on 12.

In this embodiment, the slit is formed by plating the ceramic plate with gold, but the slit may be formed by processing a slit hole in a flat plate of a conductor.
However, in this case, when a high-power microwave is applied,
There is an inconvenience that the slit plate undergoes thermal deformation due to heating by plasma. However, if the slits are formed by gold plating on the ceramics plate as in the present embodiment, heat escapes to the outside through the ceramics plate, and since the ceramics plate is less deformed by heat, the disadvantage can be solved.

This embodiment has been described microwave mode of the circular waveguide is E ₀₁ mode, the present invention is not limited thereto. However, the efficiency of microwave radiation is good if the slit is perpendicular to the current flowing on the surface of the cavity resonator. Therefore, in the case of _E01 mode, the second
As shown, in the case of H ₀₁ mode as shown in FIG. 3, and the effect is enhanced if you choose a slit shape as shown in FIG. 4 as appropriate in H ₁₁ mode.

FIG. 5 is a cross-sectional view of another example of the plasma processing apparatus shown in FIG. 1 in which a slit is formed by plating 5 above a ceramic plate 4 as another embodiment. In this case, the plating 5 is not exposed to a vacuum atmosphere, so that contamination by the plating material can be prevented.

Next, other embodiments will be described. FIG. 6 shows a detailed view of the vacuum sealing portion of the ceramic plate 4 of the plasma processing apparatus shown in FIG. An O-ring 13 is narrowed between the ceramic plate 4 and the plasma generation chamber 6 and sealed in a vacuum. The slits are formed on the ceramic plate 4 by gold plating 5, and the O-ring sealing surface of the ceramic plate 4 is also plated with gold. For this reason, the periphery of the O-ring 13 is surrounded by a conductor, microwaves do not enter the inside, and heating of the O-ring 13 by the microwave is eliminated.

FIG. 7 is a cross-sectional view of the plasma processing apparatus of FIG. 1 in which gas can be supplied from the ceramic plate 4 in a shower form. Gas supply pipe 9
The plasma processing gas guided by the above flows into a flow path provided inside the ceramic plate 4.

FIG. 8 is a plan perspective view of the ceramic plate 4, and FIG. 9 is a sectional view thereof. The ceramic plate 4 has a structure in which two plates are combined as shown in FIG. As shown in FIG. 8, a gas passage groove 15a is formed in the lower ceramic plate, and an inner wall 15b of the groove is plated with gold as shown in FIG. The diameter of the lower ceramic plate is
A circular gas outlet 14 of about 1 mm is also processed, and the gas supplied to the ceramic plate passes through the groove 15a and is supplied to the plasma processing chamber from this hole. On the other hand, a slit pattern 5b shown in FIG. 8 is gold-plated below the upper ceramic plate. However, the slit hole 5c is not plated. This plated slit pattern 5b is ninth
As shown in the figure, the gas passage groove 15a of the lower ceramics plate
Therefore, there is no problem that the microwave does not enter the groove 15a and the plasma is not generated in the gas passage groove 15a and the gas is decomposed.

Further, in the above embodiment, the slit is formed by plating the ceramic plate 4 with a conductor, but the present invention is not limited to this. A similar effect can be obtained by applying a conductor to the ceramic plate 4 or pasting a foil-like thin plate to form a slit other than plating.

Further, as the conductor material to be used, gold has been mainly described in the above embodiments, but in the present invention, the material is not limited to gold.
Similar effects can be obtained. When a slit is formed on the plasma generation chamber side of the ceramic plate by plating of a conductor, for example, gold, silver, and gold are used as the material for the slit to prevent contamination and heavy metal substances from entering the wafer.
Precious metals such as platinum are suitable.

〔The invention's effect〕

ADVANTAGE OF THE INVENTION According to this invention, even if it is exposed to high-density plasma, since the amount of thermal deformation of the slit part formed by the conductor film is small, it can supply a microwave stably, and, by this, high It is possible to stably generate density plasma.

According to the present invention, there is an effect that the device configuration is not restricted by the connection 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 set 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. Furthermore, there is an effect that uniform film formation can be performed at high speed.

[Brief description of the drawings]

FIG. 1 is a perspective view of one embodiment of the present invention, FIG. 2 is a plan view of a slit used in the embodiment of FIG. 1, FIG. 3 is a plan view of another embodiment of the slit of FIG. FIG. 4 is a plan view of a third embodiment of the slit of FIG. 2, FIG. 5 is a cross-sectional view of an embodiment in which the slit position of FIG. 1 is changed, and FIG. 6 is a vacuum sealing portion of FIG. 7 is a cross-sectional view of another embodiment of the gas supply method of FIG. 1, FIG. 8 is a plan view of the ceramic plate of FIG. 7, and FIG. 9 is a plan view of the ceramic plate of FIG. It is sectional drawing. DESCRIPTION OF SYMBOLS 1 ... Cavity resonator, 4 ... Ceramic plate 5 ... Plating, 6 ... Plasma generating chamber 7 ... Electrode, 11 ... High frequency power supply 13 ... O-ring

Claims (2)

(57) [Claims] 1. A plasma processing apparatus for processing a sample by generating plasma by supplying microwave power, comprising: microwave power supply means for generating microwave power and transporting the generated microwave power; The inside is maintained at a predetermined pressure, a plasma chamber means for generating plasma by introducing the microwave power transported by the microwave power supply means, and between the microwave power supply means and the plasma chamber means. The plasma chamber means was sealed in a vacuum and separated from the microwave power supply means, and the slit-shaped opening was provided by transmitting the microwave power and electrically connected to the microwave power supply means. A separating means provided with a conductor film on the surface and a gas flow path having a plurality of openings on the side of the plasma chamber means, provided on the separating means; And a gas supply means for supplying a gas into the plasma chamber means through the gas flow path. 2. The system according to claim 1, wherein said conductive film is provided on a side of said microwave power supply means.
Item 6. The plasma processing apparatus according to item 1.