JP2982211B2 - Plasma device and method of using the same - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a plasma device and a method for using the device.
More specifically, the present invention relates to general equipment utilizing plasma, for example, apparatuses for performing a CVD method, an etching method, a surface modification method, a sputtering method, and the like, and a method of using the same.

2. Description of the Related Art Plasma generation methods include direct current discharge, low-frequency discharge, and high-frequency discharge. In these methods, the energy or density of charged particles (electrons and ions) in the plasma is low, and plasma is generated. There was a problem that the effect was small.

On the other hand, a microwave plasma device that generates plasma using microwaves, a magnetic field microwave plasma device that applies a magnetic field to this plasma to move electrons in a cyclotron, or an electron cyclotron resonance excited plasma that uses electron cyclotron resonance (ECR plasma) devices are being actively developed, and these devices are characterized in that ions having high energy or density and particles transported by the impact can be obtained.

In particular, in an ECR plasma apparatus, as disclosed in, for example, an ion processing apparatus of Japanese Patent Application Laid-Open No. 51-71597, plasma can be generated at a low pressure, and the mean free path between ions is smaller than that of neutral molecules. Since the ion beam is sufficiently long in comparison with the ion beam, there is a feature that an ion beam with uniform direction can be obtained. Also,
As disclosed in the plasma attachment apparatus of JP-A-56-155535, an ion beam is applied to a substrate to be processed away from an ECR point by utilizing an ambipolar nucleic acid transport effect by a divergent magnetic field. Therefore, there is a feature that the temperature rise of the substrate to be processed can be suppressed.

Further, in the ECR plasma apparatus (Japanese Patent Application No. 63-330804) previously proposed by the present inventors, for example, a substrate to be processed is irradiated with Ar plasma or a mixed plasma of Ar and H ₂ before forming an epitaxial film. A so-called pretreatment can be performed, which removes the native oxide film on its surface,
There is a feature that the surface of the substrate to be processed can be cleaned. That is, as shown in FIG. 9, the ECR plasma device proposed by the inventor was formed of a microwave permeable material such as quartz in a vacuum vessel 10 comprising a resonance chamber 11 and a sample chamber 12. A plasma discharge tube 13 having an open end is provided, and a waveguide 15 for introducing microwaves into the resonance chamber 11 is connected to the upper part of the resonance chamber 11 through a microwave introduction window 14. ing. An electromagnetic coil 16 connected to a DC power supply is provided around a part of the waveguide 15 and the resonance chamber 11, and a film forming gas or a pretreatment gas is provided on one side wall of the sample chamber 12. A gas supply mechanism 17 for supplying a sample gas into the sample chamber 12 and a vacuum pump 18 for exhausting the inside of the sample chamber 12 are connected.

When performing pretreated with such a device generates a mixed plasma of Ar plasma or Ar and H ₂ to the plasma discharge tube 13, the plasma discharge tube these plasma
When irradiation is performed on a substrate S to be processed, such as a Si substrate, mounted below 13, a natural oxide film on the surface is etched away.

However, in the above-described apparatus proposed by the inventor, high-speed ions in the plasma fly out of the opening of the plasma discharge tube 13, reach the inner wall of the vacuum vessel 10, and sputter this. In some cases, metal atoms, which are components of the vacuum vessel 10, adhere to the surface of the substrate S at a high density of 10 ¹⁴ atoms / cm ² or more, thereby contaminating the substrate S.

In a conventional ECR plasma apparatus, for example, when a substrate to be processed is a Si substrate widely used as a semiconductor industrial material, “Applied Physics, Vol. 57, No. 11, (1988), pp. 172
As shown in "1-1727", the ion energy from the plasma irradiating the substrate to be processed is at least 20 eV, while the mutation energy of the atoms in the Si crystal substrate as the substrate to be processed is 12.1 eV. (G. Carter and JSColli
gon: Ion Bombardment of Solids (Heineman Eductional
Book Ltd., London, 1968). In weight percent, for example, irradiation of Ar plasma having an ion energy of 20 eV or more, the Si single crystal of the substrate to be processed is easily damaged, and high-density crystal defects are generated in the Si single crystal, so that electric power as a semiconductor material is reduced. There is a problem that the characteristic is lost.

Solving the above-mentioned problems of damage to the substrate to be processed and metal contamination is a major problem in recent ECR plasma apparatuses. For this purpose, the crystal of the substrate to be processed impairs the ion energy in the plasma applied to the substrate to be processed. It is considered that it is necessary to keep the temperature low enough to prevent the metal contamination and to obtain the effect.

By the way, in an ECR plasma device, microwaves are absorbed by generated plasma. That is, the energy of the microwave is converted into circulating kinetic energy of the electrons, and the accelerated electrons ionize the gas molecules in the device and generate secondary electrons, and the generated secondary electrons circulate by the microwave power. A chain reaction (lighting of plasma) occurs.

However, as described above, if the microwave power density supplied to the plasma discharge tube 13 is reduced in order to reduce the ion energy applied to the substrate S to be processed, the circulating kinetic energy of the electrons is reduced by a sufficient amount of secondary energy from the gas molecules. Since electrons are not generated, the plasma does not light, and there is a problem that even if the light is turned on, the plasma is unstable.

The present invention has been made in view of the above problems, and has as its object to provide a plasma apparatus capable of easily and surely lighting a plasma having a low ion energy and a method of using the apparatus.

Means for Solving the Problems In order to achieve the above-mentioned object, a plasma device according to the present invention is a plasma device including a microwave introduction mechanism, a magnetic field application mechanism, and a plasma discharge tube. A hollow cavity having a cylindrical shape for introducing microwaves is provided concentrically with the plasma discharge tube, and has a variable inner diameter.

The method of using the plasma device, wherein the cavity resonance is performed so that an average surface density of the introduced microwave power is not less than 300 mW / cm ^{2 and not} more than 1800 mW / cm ² with respect to a cross section perpendicular to the axis of the plasma discharge tube. It is characterized by setting the inner diameter of the vessel.

According to the plasma apparatus described above, a cylindrical cavity resonator for introducing microwaves to the outer periphery of the plasma discharge tube is disposed concentrically with the plasma discharge tube, and the inner diameter thereof is variable. It is configured as
Depending on the microwave power supplied to the plasma discharge tube,
The inner diameter of the cavity resonator can be continuously controlled, and plasma is stably generated in the plasma discharge tube. For example, in the step of cleaning the substrate to be processed, that is, in the pretreatment step, when the inside diameter of the cavity resonator is reduced and a low-power microwave is supplied to the plasma device, the microwave is introduced only from the top of the plasma discharge tube. As a result, a constant microwave power density is obtained, and plasma is stably generated in the plasma discharge tube. Then, the generated plasma is reliably turned on stably, and low-energy ions in the plasma are radiated to the substrate to be processed such as the Si substrate by the divergent magnetic field formed in the plasma discharge tube. Therefore, a clean substrate to be processed without damage can be obtained.

Further, in the step of forming a film on the substrate to be processed, when the inside diameter of the cavity resonator is increased and high-power microwaves in a range that does not damage the substrate to be processed are supplied to the plasma apparatus, the microwaves are generated by a plasma discharge tube. Even if there is an upper limit on the microwave power density that can be introduced and introduced from the top and surroundings, the microwave power absorbed by the plasma increases as a whole. Therefore, it is possible to increase the film formation rate, and since the side walls of the vacuum vessel are not easily sputtered by low energy ions in the plasma, a film with less metal contamination is formed on the substrate to be processed.

Furthermore, according to the method of using the plasma device described above,
The average surface density of the introduced microwave power is 300 mW / cm ² or more and 1800 mW / cm for a cross section perpendicular to the axis of the plasma discharge tube.
^Since the inner diameter of the cavity resonator is set to be ² or less,
Even when a low microwave power is supplied to the plasma discharge tube, the plasma is reliably turned on with good reproducibility. In addition, it is possible to prevent the plasma from becoming conductive due to the microwave power density being too high. Therefore, it is possible to efficiently form a good film with little metal contamination on the surface of the substrate to be processed without damage to the crystal.

Embodiments Hereinafter, embodiments of a plasma apparatus according to the present invention and a method of using the apparatus will be described with reference to the drawings.

FIG. 1 shows an EC as an example of a plasma apparatus according to the present invention.
FIG. 2 is a cross-sectional view schematically showing an R plasma device,
Indicates a cylindrical resonance chamber. A waveguide 15 for introducing microwaves into the resonance chamber 11 is provided above the resonance chamber 11.
Are connected via a microwave introduction window 14 made of quartz glass or the like, and an electromagnetic coil 16 as a magnetic field generation source is arranged around the resonance chamber 11. A cylindrical sample chamber 12 having a larger diameter than the resonance chamber 11 is provided below the resonance chamber 11.
Are connected to each other, and a partition plate 21 is hermetically interposed between the sample chamber 12 and the resonance chamber 11. In the sample chamber 12 and the resonance chamber 11, a plasma discharge tube 13 is provided so as to penetrate the partition plate 21.

The plasma discharge tube 13 is formed of a dielectric material such as quartz glass, and has a peruger 13a disposed on the resonance chamber 11 side;
The hood 13b is connected to the peruger 13a.

That is, in the resonance chamber 11, a bell jar 13a having one end formed in an open shape and the other end formed in a hemispherical shape is attached, and a flange-shaped flange 22 is formed around the opening of the bell jar 13a. Are formed. This flange
A metal holding flange 23 fixed to the partition plate 21 is provided on the top of the holding plate 22.
It is crimped to the partition plate 21 by 23. The joining surface between the flange 22 and the partition plate 21 is sealed by an O-ring (not shown) made of fluoro rubber in an O-ring groove (not shown) of the partition plate 21.
a is hermetically connected to the sample chamber 12.

A hood 13b whose tip is expanded in a trumpet shape is screwed to the opening side of the bell jar 13a.

In addition, a gas supply pipe 24 and an exhaust pipe
25 are connected to each other, and a pressure adjusting mechanism (not shown) supplies an inert gas having a pressure of 1.05 kg / cm ² G, for example, an Ar gas to a space between the resonance chamber 11 and the bell jar 13a to replace the same. . This is because the above-mentioned flange 22 and partition plate 21
The seal at the joint surface with the imperfections is not complete, from which 1 × 10 ^-4 Pa
It is because experiments have confirmed that a gas of about l / sec leaks into the sample chamber 12, and the replacement of the Ar gas prevents the air from leaking into the sample chamber 12, and the substrate S Is prevented from being contaminated.

Around the bell jar 13a of the plasma discharge tube 13 thus configured, that is, the side wall of the resonance chamber 11 and the bell jar 13a
Between the plasma discharge and the cylindrical cavity resonator 30
It is arranged concentrically with 13. As shown in FIG. 6, the cavity resonator 30 is formed by bending a strip of a conductive elastic material such as phosphor bronze into a cylindrical shape and stacking its ends 31, 32. The portions are in close contact with each other to such an extent that the microwave in the cavity resonator 30 does not leak out of the gap between the overlapping portions. The inner diameter of the cavity resonator 30 is variable by a driving mechanism 40 described later.

FIG. 3 is a schematic perspective view of the drive mechanism 40, and FIG. 4 is a view of the drive mechanism 40 when the inner diameter of the cavity resonator 30 is minimized.
FIGS. 5 and 7 show the state of the drive mechanism 40 when the inner diameter of the cavity resonator 30 is maximized, in FIGS. 5 and 7, respectively. As shown in FIG. 3, the drive mechanism 40 includes a drive shaft 41,
A shaft 43 connected in parallel to the drive shaft 41 via a support plate 42,
And two pulleys 44 inserted above and below the shaft 43. When the drive shaft 41 rotates, the shaft is
The pulley 43 and the pulley 44 also rotate about the drive shaft 41.

As shown in FIGS. 4 to 7, for example, six drive mechanisms 40 are provided outside the cavity resonator 30, and each of the drive shafts 41 is arranged near the side wall in the resonance chamber 11 or the like. It is rotatably supported by the top plate 11a and the partition plate 21 of the resonance chamber 11 at intervals. Also, a total of 12 pulleys 44 ...
Is in contact with the side wall of the cavity resonator 30 having a force to extend outward, and, of the twelve pulleys 44, around the periphery of two pulleys 44 fitted on the same shaft 43, One end 31 of the cavity resonator 30 is fixed.

At the upper end of the drive shaft 41, spur gears 45 are horizontally mounted, and these spur gears 45 are chained as shown in FIG. 8 so that the rotations of the drive shafts 41 are the same.
Connected by Further, the drive shaft 41 of the drive mechanism 40
Is connected to a rotary power source (not shown), and the drive shaft 41 is rotated by the rotary power source or is maintained at a required rotation angle.

In the resonance chamber 11 in which the drive mechanism 40 is disposed, the drive shaft 41 is rotated by a rotary power source to move the shaft 43 and the pulley 44 as shown in FIG. 4 and FIG.
When it is moved toward the center of 11, the pulley 44 pushes the side wall of the cavity 30 and the inner diameter of the cavity 30 becomes smaller. Further, the drive shaft 41 is rotated by the rotary power source, and the shaft 43 and the pulley are rotated as shown in FIG. 5 and FIG.
When 44 is moved in the peripheral direction of the resonance chamber 11, the cavity resonator 30
The side wall expands outward due to the elastic force of the cavity resonator 30 extending outward, and the inner diameter of the cavity resonator 30 increases.

Therefore, by controlling the driving mechanism 40 using the rotary power source, the inner diameter of the cavity resonator 30 substantially contacts the outer wall of the bell jar 13a of the plasma discharge tube 13, and the peripheral edge of the pulley 44 is The change can be made in the range up to the contact with the 11 side walls.

On the other hand, in the sample chamber 12 below the plasma discharge tube 13, Si
A sample stage 26 on which a substrate S to be processed such as a substrate is mounted is mounted, and a heater (not shown) and a rotation support mechanism for rotating the sample stage 26 are provided in the sample stage 26.

Further, a gas supply pipe 27a is airtightly connected to one side wall 12a of the sample chamber 12 via a shutoff valve 27b, and a gas supply source 27a is provided.
Gases such as an etching gas and a film forming gas whose flow rates are controlled in the above are supplied into the sample chamber 12 and the plasma discharge tube 13 through the gas supply tube 27a.

Further, on one side wall 12a of the sample chamber 12, an exhaust shutoff valve 28a,
A vacuum pump 28, such as a turbo molecular pump, is attached via an exhaust speed control valve 28b, and exhausts the gas in the plasma discharge tube 13 and the sample chamber 12.
The gas pressure inside can be adjusted. For example,
When the maximum diameter of the substrate S to be processed is 200 mm and the flow rate of the gas to be injected into the plasma discharge tube 13 is 50 SCCM, the exhaust speed at the exhaust shutoff valve 28a is set to 500 l / sec or more, and the conductance of the exhaust speed control valve 28b is adjusted. The pressure inside the plasma discharge tube 13 can be set to 1 × 10 ⁻² Pa or more and 5 Pa or less.

On the other side wall 12b of the sample chamber 12, a load lock chamber 29 for mounting and removing the substrate S on the sample table 26 is provided via a load lock chamber valve 29a. A sample loading window 29b for taking in and out the substrate S to be processed is formed in the upper part of 29. Further, a vacuum pump 29d such as a turbo molecular pump is connected to the load lock chamber 29, and a shutoff valve 29c is interposed between the load lock chamber 29 and the vacuum pump 29d.

When plasma is generated in the ECR plasma apparatus configured as described above, first, the vacuum pumps 28 and 29d are respectively driven to evacuate the sample chamber 12, the plasma discharge space 13, and the load lock chamber 29. . Next, the load lock chamber valve 29a is opened, and the susceptor (not shown) on the sample stage 26 is transferred to the load lock chamber 29 by the transfer arm (not shown) attached to the load lock chamber 29. Thereafter, the load lock chamber valve 29a is closed, and an inert gas such as an Ar gas or an N ₂ gas is introduced from a gas introduction pipe (not shown) connected to the load lock chamber 29, and the inside of the load lock chamber 29 is brought to atmospheric pressure. Subsequently, for example, an Si substrate is placed as the substrate S to be processed on the susceptor from the sample loading window 29b of the load lock chamber 29, and the inside of the load lock chamber 29 is evacuated by the vacuum pump 29d. Then, the load lock chamber valve 29a is opened, the susceptor is transported by the transport arm and placed on the sample table 26, and after the transport arm is pulled back to the load lock chamber 29, the load lock chamber valve 29a is closed.

Again, the inside of the sample chamber 12 and the inside of the plasma discharge tube 13 are evacuated by the vacuum pump 28 until a predetermined vacuum pressure is reached.

Thereafter, the gas supply pipe 27a and the shutoff valve 2
The exhaust speed control valve 28b is adjusted while introducing a pretreatment gas such as Ar gas into the plasma discharge tube 13 via 7b, and the inside of the plasma discharge tube 13 is set to a gas pressure at which plasma is generated. Next, the average surface density of the microwave power described later is 30
0 mW / cm ² or more 1,800 mW / cm ² to be less than the drive mechanism 40
To set the inner diameter of the cavity resonator 30. That is, in this pre-processing step, it is necessary to reduce the microwave power in order to prevent damage to the surface of the substrate S to be processed. However, in order to stably generate plasma with low microwave power and turn on the plasma, , The average surface density of the microwave power needs to be in the above range. Therefore, the inner diameter of the cavity resonator 30 is set small so that the plasma is stably generated and lit even at a low microwave power.

Subsequently, a DC voltage was applied to the electromagnetic coil 16 to form a static magnetic field having a magnetic flux density of 8.75 × 10 ⁻² T in the center of the plasma discharge tube 13 in a downward direction in FIG.
The magnetic field lines are diverged toward the substrate to be processed S while satisfying the CR condition, so that a so-called diverging magnetic field is formed. Thereafter, a frequency of 2.45 GH is transmitted from the waveguide 15 through the microwave introduction window 14.
Supply z microwave. Then, a microwave is introduced only from the top of the bell jar 13a and inside the bell jar 13a made of a dielectric material, a desired microwave power density is obtained in the plasma discharge tube 13, and plasma is generated, and a low microwave This plasma generated by the electric power stably lights with good reproducibility.

And the low-energy ions in the lit plasma are
The substrate is transported to the hood 13b side by the diverging magnetic field described above, and further irradiated on the substrate S to be processed. As a result, the substrate S to be processed is pre-processed without being damaged and without being contaminated with metal.

After a further pre-treatment, the gas introduced into the plasma discharge tube 13 is switched from the pre-treatment gas such as Ar film forming gas such as SiH ₄ without stopping the gas flow. When the microwave power supplied into the plasma discharge tube 13 is increased, the average surface density is set to be 300 mW / cm ² or more and 1800 mW / cm ² or less with respect to a cross section perpendicular to the axis of the plasma discharge tube 13. Next, the drive mechanism 40 is controlled again to set the inner diameter of the cavity resonator 30. That is, in this film formation step, in order to increase the film formation rate, it is necessary to increase the microwave power within a range where the substrate to be processed S is not damaged. However, if the microwave power density is too high, the plasma becomes conductive and the microwave becomes conductive. In order to reflect waves, it is necessary to increase the microwave power density within the above range to increase the power. Therefore, the inner diameter of the cavity resonator 30 is set to be larger than that in the pretreatment step so that the microwave power absorbed by the plasma is increased as a whole.

As a result, microwaves are introduced from the top and periphery of the bell jar 13a of the plasma discharge tube 13, and even if the microwave power density has an upper limit, the microwave power absorbed by the plasma increases, and the plasma Lights stably, and a Si thin film is formed on the surface of the substrate S to be processed. At this time, since the plasma discharge tube 13 has a substantially sealed structure, the sample chamber 12 is hardly sputtered by ions in the plasma. Even if the plasma jumps out of the discharge tube 13, the ions have low energy. Therefore, the sample chamber 12 is hardly sputtered. Therefore, a film with little metal contamination is formed on the substrate S to be processed.

After the substrate S to be processed was heated to about 700 ° C. by a heater (not shown) using the apparatus of this embodiment, the vacuum pressure was set to 1.0 × 10 ⁻⁵ Pa, and the microwave power density to the irradiated Ar and SiH ₄ plasmas was increased. When plasma was generated at a pressure of 300 mW / cm ² , it was confirmed that a single crystal Si film having a transition defect density of 50 / cm ² or less was epitaxially grown on the substrate S to be treated with Si crystal.

If a conductive polycrystalline Si film is deposited on the inner surface of the plasma discharge tube 13 and it becomes difficult to introduce microwaves into the plasma discharge tube 13, Cl ₂ (chlorine) gas is introduced into the sample chamber 12. To generate plasma as described above, the polycrystalline Si film on the inner surface of the plasma discharge tube 13 can be removed by etching. In this case, by widening the inner diameter of the cavity resonator 30, it is possible to supply a high-density, microwave power of about surface density 8000 MW / cm ^2, also the microwave is supplied across the upper and lower plasma discharge tube 13 Therefore, it is possible to quickly remove the adhered film. At this time, varying the DC voltage applied to the electromagnetic coil 16 to vary the spatial position within the plasma discharge tube 13 where the ECR condition of the magnetic flux density is satisfied is effective in uniformly removing the adhered film. It is.

FIG. 2 is a cross-sectional view schematically showing an ECR plasma device as another embodiment of the plasma device according to the present invention,
The difference from FIG. 1 is the shape of the plasma discharge tube 13 and the configuration near the lower part of the sample chamber 12. That is, as shown in FIG. 2, the plasma discharge tube 50 includes a bell jar 50a disposed on the resonance chamber 11 side, a hood 50b connected to the bell jar 50a,
And a holder 50c for placing the substrate S to be processed disposed below the hood 50b.

The bell jar 50a has the same configuration as the bell jar 13a shown in FIG. 1 and is hermetically attached to the resonance chamber 11. The opening of the bell jar 50a is formed on the sample chamber 12 side, and its lower end peripheral edge is formed. A trumpet-shaped hood 50b having a flange 51a formed thereon is screwed. A gas supply pipe 27a is connected to a side surface of the hood 50b, and the gas supply pipe 27a
A plurality of gas supply sources 27 such as an etching gas and a film formation gas provided outside the apparatus are connected via a shutoff valve 27b. The gas whose flow rate is controlled by the gas supply source 27 is supplied from the gas supply pipe 27a into the plasma discharge tube 50.

Below the hood 50b, a holder 50c having a bottomed cylindrical shape having substantially the same inner diameter as the inner diameter of the lower end of the hood 50b is provided, and a flange 51b is formed on the periphery of the upper end of the holder 50c. At this time, the holder 50c is installed below the hood 50b so that a predetermined dimension is secured between the flange portion 51b and the flange portion 51a of the hood 50b.
The gap between the flanges 51a and 51b is
An exhaust port 52 for evacuating the gas in 50 is provided. As described above, the plasma discharge tube 50 is configured so that the substrate S to be processed placed on the holder 50c cannot be directly viewed from outside the exhaust port 52, and the plasma generated in the plasma discharge tube 50 is It is difficult to jump out.

On the other hand, a transparent quartz container 54 that is rotatable about a shaft 53 and that can be moved up and down is provided below the holder 50c, and is placed in the holder 50c inside the container 54. A heater 55 for heating the processed substrate S is embedded.

When, for example, an epitaxial film is formed on the substrate to be processed S using the ECR plasma apparatus formed as described above,
First, the vacuum pumps 28 and 29d are driven, respectively, to
2, the plasma discharge tube 40 and the load lock chamber 29 are evacuated. Next, the bellows 57 is extended by pulling out a support rod 56 attached below the container 54, and the container 54 is kept at a predetermined height with respect to the load lock chamber 29 while keeping the inside of the sample chamber 12 under reduced pressure. Go to Then, the holder 50c is transported to the load lock chamber 29 by a transport arm (not shown) attached to the load lock chamber 29. Thereafter, the substrate S to be processed such as a Si substrate is placed on the holder 50c from the sample loading window 29b by the same operation as described above, and the holder 50c is again placed on the container 54 by the transfer arm.
The container 54 is set at a predetermined position using the support shaft 56.

Then, in the same manner as in the embodiment described with reference to FIG. 1, the inside of the sample chamber 12 and the plasma discharge tube 50 are evacuated to a predetermined pressure, and the film forming gas is discharged from the sample chamber 12 and the plasma discharge tube. Feed into tube 50. Next, the driving mechanism 40 is controlled to control the inner surface of the cavity 30 so that the average surface density of the microwave power is 300 mW / cm ² or more and 1800 mW / cm ² or less with respect to a cross section perpendicular to the axis of the plasma discharge tube 50. Set. Subsequently, a voltage is applied to the electromagnetic coil 16 so that the plasma discharge tube 50
A diverging magnetic field is formed therein, and a microwave is supplied from the waveguide 15 to the resonance chamber 11.

Then, plasma is generated in the plasma discharge tube 50, and the lamp is stably lit with good reproducibility even at a low microwave power. Then, low-energy ions in the lit plasma are irradiated to the substrate S to be processed. Further, since the plasma discharge tube 50 has a substantially closed structure, the sample chamber 12 is hardly sputtered by ions in the plasma. Even if the plasma jumps out of the plasma discharge tube 50, the ions have low energy. The sample chamber 12 is hardly sputtered. From the above, a film with very little metal contamination is formed on the substrate S to be processed.

Before forming the above-mentioned epitaxial film,
By introducing a pretreatment gas of Ar gas from the gas supply source 27 into the sample chamber 12 and the plasma discharge tube 50 and setting the inner diameter of the cavity resonator 30 to a predetermined size, under the same conditions as above. In addition, the pretreatment can be performed without damaging the substrate to be processed S and without causing metal contamination.

As described above, according to the above-described embodiment, plasma with low ion energy can be easily and reliably turned on, so that a plasma process with few crystal defects and metal contamination can be efficiently realized. .

Effect of the Invention As is clear from the above description, according to the plasma device of the present invention, the cylindrical cavity resonator for introducing microwaves to the outer periphery of the plasma discharge tube is concentric with the plasma discharge tube. And the inner diameter thereof is variable, so that the inner diameter of the cavity resonator can be continuously controlled in accordance with the microwave power supplied to the plasma discharge tube. The plasma can be stably turned on in the plasma discharge tube. Therefore, for example, when an epitaxial film is formed on a substrate to be processed composed of a Si end blood phase, plasma having a low microwave power density is used in the pretreatment step and the epitaxial film formation step, and the plasma is used in the discharge tube cleaning step. Since a plasma having a high microwave power density can be used only by changing the inner diameter of the cavity resonator, a high-quality epitaxial wafer with few defects can be rapidly manufactured.

Further, according to the method of using the plasma device described above, the average surface density of the introduced microwave power is 300 mW / cm ² or more and 1800 mW / cm ^{2 with} respect to a cross section perpendicular to the axis of the plasma discharge tube.
Since the inner diameter of the cavity resonator is set as follows, even when a low microwave power is supplied to the plasma discharge tube, the plasma is reliably lit with good reproducibility. Also,
The conductorization of the plasma caused by too high a microwave power density is also avoided. Therefore, a good film with little metal contamination can be efficiently formed on the surface of the substrate to be processed without damage to the crystal.

[Brief description of the drawings]

FIG. 1 shows an ECR as an example of a plasma apparatus according to the present invention.
FIG. 2 is a cross-sectional view schematically showing a plasma apparatus, FIG. 2 is a cross-sectional view schematically showing an ECR plasma apparatus as another embodiment of the plasma apparatus according to the present invention, and FIG.
FIGS. 4 and 5 are schematic perspective views showing an example of the drive mechanism provided in the figures, and FIGS. 4 and 5 schematically show the state of the drive mechanism when the inner diameter of the cavity resonator is minimized and maximized, respectively. 6 and 7 are respectively a sectional view taken along the line II in FIG. 4 and a sectional view taken along the line II-II in FIG. 5, FIG. 8 is a schematic plan view of the resonance chamber, and FIG. The figure is a cross-sectional view schematically showing a conventionally proposed ECR plasma device. 13, 50: Plasma discharge tube 14: Microwave introduction window 15: Waveguide 16: Electromagnetic coil 30: Cavity resonator 40: Drive mechanism

──────────────────────────────────────────────────の Continued on front page (51) Int.Cl. ⁶ Identification code FI H05H 1/46 H01L 21/302 B

Claims (2)

(57) [Claims] 1. A plasma apparatus comprising a microwave introducing mechanism, a magnetic field applying mechanism, and a plasma discharge tube, wherein the cylindrical discharge cavity for introducing microwaves to the outer periphery of the plasma discharge tube includes a plasma discharge tube. And a concentric arrangement with the plasma apparatus, wherein the inner diameter of the plasma apparatus is variable. 2. The average surface density of microwave power introduced is 300 mW / cm for a cross section perpendicular to the axis of the plasma discharge tube.
^{2. The} method according to claim 1, wherein the inner diameter of the cavity resonator is set so as to be ² or more and 1800 mW / cm ² or less.