JP3814266B2 - Plasma processing equipment - Google Patents

Description

  The present invention relates to an apparatus for performing an etching process using plasma, and more particularly to a plasma processing apparatus suitable for etching a substrate having a large diameter.

  A plasma processing apparatus is an apparatus that etches an object to be processed such as a semiconductor substrate with an etching gas that has been turned into plasma by an electromagnetic wave such as a microwave. At this time, an etching process in which the electromagnetic wave such as a microwave is formed into a substantially cylindrical shape. Conventionally, a coaxial line is used for introduction into the chamber (see, for example, Patent Document 1).

In this prior art, an electromagnetic wave to be supplied from the coaxial line into the processing chamber is introduced into the processing chamber from the periphery of the disk-shaped antenna in the processing chamber, and the slot line provided in the disk-shaped antenna is provided. Also, the electromagnetic field distribution in the processing chamber is adjusted by radiating electromagnetic waves and introducing the electromagnetic field into the processing chamber, so that a plasma distribution with good uniformity can be obtained.
Japanese Patent Laid-Open No. 11-260594

  The above prior art cannot be said to be concerned about the concentration of the electromagnetic field in the vicinity of the center of the processing chamber, and has a problem that the uniformity of the plasma density distribution is impaired depending on the process conditions.

  In addition, the prior art cannot be said to be considered that a relatively high density plasma is formed near the upper part of the cylindrical portion of the processing chamber, and there is a problem in plasma generation efficiency.

  Since the plasma formed near the upper part of the cylindrical part of the processing chamber is lost on the inner wall surface of the processing chamber having a substantially cylindrical shape, it contributes little to improving the plasma density near the substrate to be processed. do not do.

  For this reason, the generation efficiency of the plasma with respect to the electric power supplied as the electromagnetic wave is suppressed, and thus a problem occurs in the plasma generation efficiency.

  An object of the present invention is to provide a plasma processing apparatus in which uniformity of plasma density distribution and improvement in plasma generation efficiency can be obtained.

  The above problem can be solved by using an antenna structure that is adjusted so that the electric field component on the central axis of the etching chamber is significantly reduced and electromagnetic waves are not distributed near the wall of the etching chamber.

  And as an electromagnetic wave having such a distribution, there is an electromagnetic field distribution adjusted so that the electric field component is practically only the circumferential component. By using the electromagnetic field distribution adjusted in this way, Electric field concentration and plasma concentration near the upper part of the inner wall surface of the etching chamber can be prevented.

  Here, if an electric field distribution in which the electric field component is practically only the circumferential component is used, the circumferential electric field component cannot exist on the central axis, so that problems such as electric field concentration at the center do not occur.

  Similarly, the electromagnetic field distribution having only the circumferential component has no electric field component on the inner wall surface of the etching chamber made of a material having high conductivity. It does not form plasma.

  At this time, in order to realize an electric field distribution in which the electric field component is substantially only the circumferential component, a slot line extending in the radial direction with respect to the central axis is used. Here, in the slot line, when two flat plates having high conductivity are installed so as to face each other, electromagnetic waves are propagated between the flat plates, and this is used as a line.

  The electric field on the slot line is perpendicular to the longitudinal direction of the slot line and faces in the direction from one flat plate to the other flat plate. By arranging a plurality of excited slot lines in the radial direction with respect to the central axis using this property, an electric field distribution having only a circumferential component as a whole can be realized.

Therefore, the above-described object is to provide a plasma processing apparatus that radiates electromagnetic waves from a disk-shaped antenna that is substantially in contact with an electromagnetic wave introduction window of the etching processing chamber into the etching processing chamber having a substantially cylindrical shape, and converts the etching gas into plasma. The disk-shaped antenna includes a plurality of slot lines, and the plurality of slot lines are arranged radially on the surface of the disk-shaped antenna on the electromagnetic wave introduction window side, and the electromagnetic wave introduction of the disk-shaped antenna is introduced. The surface opposite to the window side is arranged in the circumferential direction, and the radially arranged slot lines and the circumferentially arranged slot lines are formed on the side end surface portion of the disc-shaped antenna. This is achieved by being connected by a slot line .

  At this time, there may be provided means for applying a static magnetic field substantially vertically to the object to be processed in the etching chamber, and the frequency of the electromagnetic wave may be 200 MHz or more and 5 GHz or less.

  Hereinafter, a plasma processing apparatus according to the present invention will be described in detail with reference to embodiments shown in the drawings.

  FIG. 1 shows an embodiment of an etching processing apparatus according to the present invention. In this case, the processing chamber 1 is formed of a bottomed container having a substantially cylindrical shape, on which a dielectric plate 2 made of, for example, quartz or the like. The antenna room 3 is provided in a form separated by.

  The processing chamber 1 is provided with a substrate electrode 4 serving as a substrate mounting base, on which a substrate to be etched, that is, a substrate W to be processed, is mounted. For example, after being electrostatically adsorbed, the etching process is performed.

  Further, a circular disk-shaped antenna 5 is provided in the antenna chamber 3, and electromagnetic waves in a microwave band with a frequency of 450 MHz, for example, are radiated from the disk-shaped antenna 5 and processed through the dielectric plate 2. The plasma is supplied into the chamber 1 and etching gas in the processing chamber 1 is generated.

  For this reason, the disk-shaped antenna 5 is supplied with high-frequency power having a frequency of 450 MHz that has been impedance-matched by the automatic matching unit 7 from the high-frequency power source 6 via the coaxial line 8. Is functioning as a window for introducing electromagnetic waves from the antenna chamber 3 into the processing chamber 1, that is, an electromagnetic wave introducing window.

  Here, a nozzle plate 10 is provided with a narrow gap on the dielectric chamber 2 on the processing chamber 1 side, and a predetermined etching gas is supplied to the gap from a gas supply system (not shown). Yes.

  At this time, the nozzle plate 10 is formed with a large number of gas nozzles 11 made of fine holes. As a result, when the etching gas is supplied to the gaps, the etching gas is showered from the gas nozzles 11. Are ejected in a shape and supplied into the processing chamber 1.

  A vacuum exhaust system (not shown) is connected to the processing chamber 1, and the gas from the gas supply system can be exhausted to maintain the processing chamber 1 at a predetermined pressure suitable for processing.

  Therefore, by adjusting the distribution of the gas nozzles 11 in the nozzle plate 10, the gas flow in the processing chamber 1 can be controlled, and the etching process can be optimized. Here, in this embodiment, quartz is used as the material of the nozzle plate 10 as with the dielectric plate 2.

  In addition, coils 12, 13, and 14 are provided around the processing chamber 1 as static magnetic field generating devices, whereby a static magnetic field in a predetermined direction, for example, a direction substantially perpendicular to the substrate to be processed, is provided in the processing chamber 1. In addition, the diffusion of the plasma generated in the processing chamber 1 is controlled, and the density distribution of the plasma can be adjusted.

  At this time, by matching the electron cyclotron frequency with the frequency of the electromagnetic wave, an electron cyclotron resonance phenomenon in which the electromagnetic wave is resonantly absorbed by the plasma can be caused in the processing chamber 1.

  Here, in the case of the above-described microwave having a frequency of 450 MHz, the strength of the static magnetic field necessary for causing electron cyclotron resonance is 0.016 Tesla.

  In this way, by causing electron cyclotron resonance, plasma generation and maintenance can be facilitated, and plasma processing can be made even under a low pressure that is normally difficult to generate plasma.

  At this time, the location where electron cyclotron resonance occurs can be controlled by adjusting the static magnetic field. By controlling the plasma generation region in this way, the plasma distribution can be adjusted, and therefore an optimum plasma treatment can be performed.

  However, the static magnetic field generator using these coils 12, 13, and 14 is not necessarily an essential requirement for carrying out the present invention, and may be omitted if it is not necessary to finely control the plasma.

  By the way, in this embodiment, the case where the to-be-processed substrate W is 300 mm in diameter is assumed, For this reason, the substrate electrode 4 is also dimensioned so that the to-be-processed substrate W with a diameter of 300 mm can be mounted.

  A high frequency bias power source 16 is connected to the substrate electrode 4 via an automatic matching unit 15 so that a high frequency bias potential can be applied to the substrate W to be processed.

  In this way, by applying a bias potential, ions in the plasma can be attracted to the substrate W to be processed, and as a result, the etching process can be speeded up and the quality can be improved.

  The frequency of the high-frequency bias potential at this time is generally 400 kHz, 800 kHz, 2 MHz, or the like. In this embodiment, a frequency of 400 kHz is used.

  Next, the disk-shaped antenna 5 which is a feature of the present invention will be described in detail with reference to FIGS. Here, first, FIG. 2 is a front view of the disk-shaped antenna 5, FIG. 1 is a view from above, FIG. 3 is a side view, and is also a view from the front, and FIG. It is the figure similarly seen from the bottom.

  Here, first, the disc-shaped antenna 5 is a kind of array antenna used in the microwave band, and is configured by a so-called slot antenna using a slot line as an antenna element.

  The slot line is an elongated gap formed in the conductor plate and functions as a waveguide (electromagnetic wave path) .For example, `` Electronic Information Communication Handbook (Electrical Information Communication Society, Ohm, 1988) '' The slot antenna is also described in the same manner.

  For this reason, a disk-shaped dielectric plate 51 provided with a conductor plate 50 on the surface is used as a base material, and a gap, that is, a slot is provided in the conductor plate 50 in a predetermined pattern to form a slot line. The disk-shaped antenna 5 is arranged in a pattern.

  More specifically, as shown in FIGS. 2 to 4, the conductor plate 50 is roughly divided into an upper surface center portion 50A and a connecting portion 50B, an upper surface sector portion 50C, a side end surface portion 50D, a lower surface sector portion 50E, and a lower surface center portion 50F. The dielectric plate 51 is disposed from the front surface to the back surface including the side end surfaces.

  In addition, although the thin copper plate is normally used as this conductor plate 50, a copper foil and a copper plating layer may be used, and an aluminum material may be used at this time.

  Here, first, on the upper surface of the dielectric plate 51, as shown in FIG. 2, there is a substantially circular upper surface center portion 50A at the center, and the coaxial line 8 is connected thereto. And eight short connection parts 50B are radially extended from this upper surface center part 50A, and are continuing to each of the eight upper surface fan-shaped parts 50C in the periphery.

  Next, as shown in FIG. 3, these eight upper surface fan-shaped portions 50 </ b> C extend to the peripheral surface of the side end of the dielectric plate 51 to form a side end surface portion 50 </ b> D. As shown in FIG. 4, eight lower surface fan-shaped portions 50 </ b> E are formed and are collectively collected in the lower surface central portion 50 </ b> F.

  As a result, first, on the upper surface of the disk-shaped antenna 5, the arc-shaped first slot line S1 and the linear second slot line S2 extending in the radial direction are formed around the upper surface center portion 50A. Each of the eight dielectric plates 51 is formed on the surface.

  Next, eight third slot lines S3 extending in the vertical direction are formed on the peripheral surface of the side end of the disk-shaped antenna 5, and the fourth linear line extending relatively long in the central direction is formed on the lower surface. The eight slot lines S4 are also formed.

  Here, such an electric field on the slot line appears from one end portion of the conductor plate facing at the slot portion to the other end portion. That is, the electric field appears at right angles to the longitudinal direction of the slot. The direction of the electric field at this time follows the boundary condition.

  Therefore, the electric field appearing in the first slot line S1 facing the circumferential direction in FIG. 2 is directed in the radiation direction and the electric field appearing in the second slot line S2 facing the radiation direction as shown by the arrows is Also, as indicated by the arrow, face in the circumferential direction.

  Similarly, the electric field appearing in the third slot line S3 facing in the up-and-down direction in FIG. 3 is directed to the circumferential direction as shown by the arrow, and is directed to the radial direction in FIG. The electric field appearing at S4 is also directed in the circumferential direction as indicated by the arrow.

  On the other hand, in this embodiment, in order to excite the slot line, a method of blocking the surface current by the slot line is used. Therefore, as shown in FIG. 2, the inner conductor of the coaxial line 8 is formed at the center of the upper surface center portion 50A. Is connected.

  In this case, the surface current due to the high frequency of 450 MHz flows radially from the center of the upper surface center portion 50A. Therefore, in order to block this surface current, it is necessary to orient the direction of the slot line in the circumferential direction. Here, when the slot line is directed in the radial direction, the slot line is not excited.

  Therefore, in this embodiment, the slot line is excited only at the portion of the first slot line S1 shown in FIG. 2, and electromagnetic waves (450 MHz microwaves) are radiated. Then, this electromagnetic wave is transmitted along the slot line, and finally, the electric field in the circumferential direction indicated by the arrow is excited in the fourth slot line S4 in FIG.

  Here, FIG. 5 shows an electric field having a frequency of 450 MHz in the embodiment described above, and a surface electric field vector of plasma generated in the processing chamber 1 is calculated and indicated by an arrow. No static magnetic field is generated and no magnetic field is generated.

  In this calculation, Maxwell's equation, which is the governing equation of electromagnetic waves, is used, and the electric field vector is calculated by solving this equation. As is apparent from FIG. It turns out that the electric field of the radial direction does not generate | occur | produce in the circumferential direction.

  Therefore, according to this embodiment, the electric field concentration of the electromagnetic wave in the processing chamber 1 does not occur, and the plasma can be generated uniformly in the processing chamber 1, so that the uniformity of the plasma density distribution may be deteriorated. As a result, uniform plasma treatment can be obtained regardless of the type of etching gas.

  Further, according to this embodiment, since an electric field in the radial direction is not generated, the loss of plasma on the wall surface of the processing chamber 1 can be suppressed, and as a result, the plasma generation efficiency can be improved.

  By the way, at this time, it is desirable that the total length of the slot lines S1 to S4 is an integral multiple of a half wavelength of the electromagnetic wave radiated from the disc-shaped antenna 5. This is because by setting the length of the slot line in this way, electromagnetic waves resonate in the slot line and radiation efficiency can be increased.

  Here, in order to realize such a resonance state, the total length of the slot line itself of the disk-shaped antenna 5 may be adjusted. Instead, the dielectric constant of the dielectric plate 51 is adjusted. Alternatively, a dielectric other than air may be loaded in the gap forming the slot line, and the dielectric constant of this dielectric may be adjusted.

  At this time, the wavelength of the electromagnetic wave propagating through the slot line qualitatively becomes shorter when the dielectric constant around the slot line is increased and becomes longer when the dielectric constant is lowered. Accordingly, when a plurality of dielectrics exist around the slot line as in this embodiment, an effective dielectric constant is determined between the highest dielectric constant and the lowest dielectric constant.

  By the way, in the said embodiment, the circumferential end of the disk shaped antenna 5 is hold | maintained by the short circuit board 17 to the container which comprises the antenna chamber 3, and a circumferential end is electrically connected to circumference | surroundings except a slot line part. Thus, the electromagnetic wave introduced from the coaxial line 8 is prevented from being radiated into the processing chamber 1 from other than the slot line portion.

  However, when the plasma is generated only by the electromagnetic field due to the circumferential electric field component formed by the slot line, when the plasma density near the central axis becomes insufficient, the short-circuit plate 176 is not provided, Similarly, electromagnetic waves that circulate from the periphery of the disk-shaped antenna 5 may be actively used.

  In this case, the electromagnetic wave introduced into the processing chamber 1 is a mixture of an electromagnetic field having a circumferential electric field component excited by a slot line and an electromagnetic field having a radial electric field that wraps around the disk-shaped antenna 5. In this case, the electromagnetic wave that has passed through the disk-shaped antenna 5 has an electric field component even near the central axis, so that the plasma density near the central axis can be compensated.

  In the above embodiment, the case where the frequency of the plasma generating electromagnetic wave is 450 MHz has been described as an example. However, the frequency in the embodiment of the present invention is not limited to this.

  Here, the elements that limit the lower limit of the frequency include the size (diameter dimension) of the substrate to be processed W and the size of the processing chamber 1. At this time, the diameter of the substrate W to be processed has recently been From the standpoint of improving the performance, the size has increased, and now 300 mm is becoming mainstream.

  On the other hand, while the apparatus is required to be downsized, it is desired that the size of the processing chamber be a minimum size that can ensure uniformity of plasma processing.

  At this time, in order to ensure the uniformity of the plasma processing within the surface of the substrate W to be processed, it is necessary to generate plasma uniformly within a range equal to or larger than the diameter of the substrate W to be processed. For this, the disk-shaped antenna 5 also needs to have a size of about 300 mm in diameter, which is about the same as the substrate W to be processed.

  Therefore, in order to meet this requirement, a dielectric plate 51 having a diameter of about 300 mm, which is about the same as the substrate to be processed W, is prepared, and a slot line whose length is an integral multiple of a half wavelength. Must be placed.

  Here, in order to arrange the slot line from the upper surface to the lower surface of the disk having a diameter of about 300 mm, the total length of the slot line needs to be approximately 300 mm or less. However, from the standpoint of wavelength reduction, the dielectric plate 51 Even if alumina ceramics with a relative dielectric constant of 9.8 is used, the half wavelength of free space has already reached 239 mm at a frequency of 200 MHz.

  Accordingly, in the case of the embodiment of the present invention, it can be said that the lower limit of the frequency of the plasma generating electromagnetic wave is appropriately about 200 MHz. As a result, according to the present invention, it is easy to increase the diameter of the substrate W to be processed. It can correspond to.

  On the other hand, regarding the upper limit of the frequency of the plasma generating electromagnetic wave, the higher the frequency, the shorter the wavelength. Therefore, it is desirable because the degree of freedom in arranging the slot line on the same size disk is increased.

  However, if the frequency of the electromagnetic wave is increased, the high frequency power supply becomes expensive, and if a high output is required, it becomes more expensive, and if the frequency is increased, the transmission loss increases, and the degree of freedom of electromagnetic field distribution near the processing chamber. This increases the number of problems such as difficulty in controlling the electromagnetic field distribution.

  Therefore, in the case of the above embodiment, from the viewpoint of practicality, it can be said that the upper limit is a frequency of about 5 GHz where the half wavelength is about 30 mm. As a result, according to this embodiment, the processing target is processed. Similarly, it is possible to easily cope with an increase in the diameter of the substrate W.

  As described above, according to the above embodiment, electric field concentration near the center of the processing chamber can be prevented, and more uniform plasma can be generated in a wide range of conditions.

  In addition, since the input electric power can be effectively used for generating plasma in the vicinity of the substrate to be processed, it can also contribute to effective use of energy.

It is sectional drawing which shows one Embodiment of the plasma processing apparatus by this invention. It is a top view which shows one Embodiment of the planar antenna in this invention. It is a side view which shows one Embodiment of the planar antenna in this invention. It is a bottom view which shows one Embodiment of the planar antenna in this invention. It is a characteristic view by one Embodiment of the planar antenna in this invention.

Explanation of symbols

W: Substrate to be processed 1: Processing chamber 2: Dielectric plate 3: Antenna chamber 4: Substrate electrode (substrate mounting base)
5: Disc antenna 6: High frequency power supply 7: Automatic matching device 8: Coaxial line 10: Nozzle plate 11: Gas nozzle (gas ejection hole)
12, 13, 14: Coil (coil that works as a static magnetic field generator)
15: Automatic matching device 16: High frequency bias power supply 17: Short-circuit plate 50: Conductor plate 50A: Upper surface center portion 50B: Connection portion 50C: Upper surface fan portion 50D: Side end surface portion 50E: Lower surface fan portion 50F: Lower surface center portion 51: Dielectric Body plates S1 to S4: Slot lines

Claims (3)

In a plasma processing apparatus of a system that radiates electromagnetic waves from a disk-shaped antenna that is substantially in contact with an electromagnetic wave introduction window of the etching processing chamber, and converts the etching gas into plasma in an etching processing chamber having a substantially cylindrical shape,
The disk-shaped antenna comprises a plurality of slot lines;
The plurality of slot lines are arranged radially on the surface of the disk-shaped antenna on the side of the electromagnetic wave introduction window, and are arranged in the circumferential direction on the surface of the disk-shaped antenna opposite to the electromagnetic wave introduction window side. And
The plasma processing apparatus, wherein the radially arranged slot lines and the circumferentially arranged slot lines are connected by a slot line formed on a side end surface portion of the disc-shaped antenna . The plasma processing apparatus according to claim 1 ,
Means for applying a static magnetic field substantially perpendicularly to an object to be processed in the etching chamber is provided. The plasma processing apparatus according to claim 1,
A plasma processing apparatus, wherein the electromagnetic wave has a frequency of 200 MHz to 5 GHz.

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