JP2005019346A - Plasma treatment device, plasma radiation antenna used for this and wave guide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plasma radiation antenna with good radiation efficiency of the microwave, a wave guide and a plasma treatment device using it. <P>SOLUTION: A treatment container storing a substrate to be treated inside, an electromagnetic wave generating part generating an electromagnetic wave for plasma enhancement, an antenna radiating the electromagnetic wave to the treatment container and generating the plasma and a wave guide guiding the electromagnetic wave generated by an electromagnetic wave generator to the antenna are provided. In the antenna, a power feeding part to guide in power from the wave guide and a plurality of slots formed on a surface opposite to the power feeding part are formed. Furthermore, the power feeding part is formed in a position shortening the travelling distance of the electromagnetic wave which is travelled inside the antenna. Then, the electromagnetic wave is radiated inside the treatment container from the slots in the antenna. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a plasma processing apparatus for processing a semiconductor substrate, an LCD glass substrate, or an organic EL substrate using plasma, and more particularly to a structure of a microwave radiation antenna and a waveguide.
[0002]
[Prior art]
In recent years, the development of processing technology for semiconductor substrates using plasma has been remarkable. This is because the use of plasma processing has the advantage that the processing temperature of the semiconductor substrate can be significantly reduced as compared with the conventional case. For plasma processing, it is necessary to introduce microwaves (electromagnetic waves) into the processing container. Microwaves oscillated by a high-frequency electromagnetic wave oscillator are introduced into the processing container via a waveguide, an antenna, and in some cases a dielectric window. In the antenna, for example, a large number of slots arranged at a pitch corresponding to one wavelength of the microwave are formed. The microwave fed from the waveguide to the antenna leaks from the slot while propagating in the outer peripheral direction, and is introduced into the processing container (chamber) through the dielectric window.
[0003]
Although the technical field is different from that of the present invention, there is a research paper (Non-Patent Document 1) on an antenna for satellite broadcasting, which explains the slot shape of the antenna.
[Non-Patent Document 1] Enhancement of Band-Edge Gain
in Radial Line Slot Antenna Using the Power Divider, IEICE TRANS. COMMUN. , VOL. E78-B, NO. 3 MARCH 1995
[0004]
[Problems to be solved by the invention]
A magnetron oscillator or the like used as a device for generating a microwave has poor oscillation frequency stability. Further, when the output power is increased or decreased, the frequency may change. Furthermore, if the oscillation frequency deviates from the design value of the slot, the phase may gradually shift during propagation on the antenna. In particular, the error (phase shift) of the microwave increases as the position is closer to the periphery of the antenna (propagation end). As a result, there has been a problem that electromagnetic waves (microwaves) are not efficiently emitted from the slots. In addition, the radiation efficiency and uniformity of the antenna are also reduced.
[0005]
The present invention has been made in view of the above situation, and provides a plasma processing apparatus capable of efficiently supplying electromagnetic waves (microwaves) into a processing container, and a microwave waveguide and a microwave radiation antenna used therefor. For the purpose.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, a plasma processing apparatus according to the present invention includes: a processing container that contains a substrate to be processed; an electromagnetic wave generating unit that generates an electromagnetic wave for plasma excitation; And an antenna for generating plasma; and a waveguide for guiding the electromagnetic wave generated by the electromagnetic wave generator to the antenna. The antenna is formed with a power feeding part for introducing power from the waveguide and a plurality of slots formed on a surface opposite to the power feeding part. Further, the power feeding unit is formed at a position where the propagation distance of the electromagnetic wave propagating through the antenna becomes short. And electromagnetic waves are radiated | emitted in the said process container from the slot of the said antenna.
[0007]
A microwave radiating antenna according to the present invention is an antenna that is connected to a waveguide that guides an electromagnetic wave for plasma excitation, and that radiates into a processing container that accommodates a substrate to be processed to generate plasma. A power feeding unit for introducing power; and a plurality of slots formed on a surface opposite to the power feeding unit. The power feeding unit is formed at a position where a propagation distance of an electromagnetic wave propagating through the antenna becomes short. And electromagnetic waves are radiated | emitted in the said process container from the slot of the said antenna.
[0008]
The waveguide according to the present invention is a waveguide connected to an antenna that radiates electromagnetic waves into a processing container containing a substrate to be processed, and an end connected to the antenna propagates through the antenna. It is in a position where the propagation distance of electromagnetic waves is shortened.
[0009]
As described above, in the present invention, the microwave for plasma generation is supplied into the antenna not from the center of the microwave radiation antenna but from the portion between the center and the outer periphery thereof. Thereby, it propagates in the center direction and the outer peripheral direction in the antenna, and leaks from the slot of the planar antenna. In other words, since the propagation distance of the microwave is shorter (about half) than the conventional distance, the phase shift due to the difference between the design frequency and the transmission frequency during the propagation can be reduced.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows an example of a schematic configuration of a plasma processing apparatus 10 used in the present invention. The plasma processing apparatus 10 includes a processing container 11 provided with a substrate holder 12 that holds a silicon wafer W as a substrate to be processed. The gas (gas) in the processing container 11 is exhausted from exhaust ports 11A and 11B via an exhaust pump (not shown). The substrate holder 12 has a heater function for heating the silicon wafer W. In the case of an etching apparatus, a cooling function is added.
[0011]
An opening is provided above the processing container 11 so as to correspond to the silicon wafer W on the substrate holder 12. This opening is closed by a dielectric plate 13 made of quartz or Al2O3. A planar antenna 14 is disposed on the top of the dielectric plate 13 (outside the processing container 11). A plurality of slots for transmitting electromagnetic waves supplied from the waveguide are formed on the lower surface of the planar antenna 14. A waveguide 15 is disposed further above (outside) the planar antenna 14. The waveguide 15 is connected to a magnetron 30 that generates a plasma generation microwave (eg, 2.45 GHz).
[0012]
As an antenna for plasma radiation, in addition to the planar antenna 14, a convex antenna protruding to the processing container 11 side (lower side) or an antenna having a concave lower side can be used.
[0013]
FIG. 2 shows an enlarged view of essential parts of the waveguide 15 and the planar antenna 14. The planar antenna 14 includes a waveguide 15a that fills the internal space, and a power feeding unit 15d that is provided above the waveguide 15a. The waveguide 15 propagates an electromagnetic wave through the waveguide 15c and is connected to the power supply 15d of the antenna 14 at the connection 15b. The waveguide portion 15 c guides the microwave generated by the magnetron 30 to the upper part of the processing container 11. It is preferable that the outermost peripheral portion of the antenna 14 be surrounded by a metal body so that electromagnetic waves propagating through the antenna do not leak from the outer peripheral portion to the outside. Moreover, it is preferable to provide a metal body that prevents the propagating electromagnetic wave from propagating across the central portion inside the antenna 14. This metal body can be cylindrical or columnar.
[0014]
The waveguide portion (cylindrical waveguide) 15c is a coaxial waveguide having an inner conductor 15f, and an end portion of the inner conductor 15f is connected to the bottom surface of the connection portion 15b (disk-shaped waveguide). In addition, a metal body having a substantially conical shape protruding toward the waveguide portion (cylindrical waveguide) 15c is provided at the center of the bottom surface of the connection portion 15b (disc-shaped waveguide). In the present embodiment, the coaxial cable 15f is provided. However, a waveguide (15c, 15b) whose inside is constituted by a cavity or a dielectric can also be used.
[0015]
The power feeding unit 15d is an exit of the electromagnetic wave guided by the waveguide unit 15c. The power feeding unit 15d is partitioned by an inner metal plate 15e and an outer metal plate 15g. The power feeding unit 15d is connected to the connection unit 15b at the upper part thereof. Further, the connection portion 15b is connected to the waveguide portion 15c. The inner metal plate 15e is disposed so as to cover the central portion of the planar antenna 14. The metal plate 15e and the outer peripheral metal plate 15g form a power feeding portion 15d so that electromagnetic waves are fed near the center between the center and the outer peripheral portion of the planar antenna 14. That is, the power feeding unit 15d is disposed at a position where the propagation distance of the electromagnetic wave in the antenna 14 is shortened. When the power feeding unit 15d is arranged in this manner, the propagation distance of the microwave in the antenna 14 is about half that of the conventional one, so that the phase shift during propagation can be reduced.
[0016]
The connecting portion 15b has a tapered portion whose cross-sectional area gradually increases from the connecting portion with the waveguide portion 15c to the power feeding portion 15d toward the planar antenna 14. In FIG. 2, the distance from the end of the inner metal plate 15e to the end of the connecting portion 15b (or outer peripheral metal plate 15g) is W1, the width of the tapered portion is W2, and the connecting portion 15b (or outer peripheral metal plate 15g). Let ρ be the radius of.
[0017]
In the present embodiment, for example, the diameter of the antenna 14 is 600 mm, the upper waveguide height 15 h is 15 mm, the lower waveguide height 15 a is 5 mm, the metal plate 15 e is 2 mm thick, and the dielectric in the lower waveguide (15 a). When the relative dielectric constant of the body is 9.4, the width W1 of the power feeding window 15d = 14.6 mm and the taper width W2 = 33.1 mm.
[0018]
Also, under the condition that an antenna having a diameter of 600 mm is used, the height of the upper layer waveguide and the height of the lower layer waveguide are 15 mm, and the thickness of the metal plate 15e is 2 mm, the width W1 of the feeding window 15d is 37.2 mm, and the taper. The width W2 = 12.6 mm and ρ = 182 mm.
[0019]
In addition, when the diameter of the antenna 14 is 780 mm, it can be the same as the case where the antenna 14 with a diameter of 600 mm is used except that ρ = 237 mm.
[0020]
The waveguide 15 a propagates the propagated microwave to the planar antenna 14. If the planar antenna is cylindrical, the waveguide 15a has a disk shape. If the planar antenna 14 is rectangular, the waveguide 15a can be a rectangular parallelepiped (cube). The waveguide 15a and the power feeding portion waveguide 15h are cavities in this embodiment, but may have a structure in which the inside is filled with a dielectric.
[0021]
A cooling plate 16 is disposed outside the processing container 11 so as to cover the waveguide 15a or the connection portion 15b. Inside the cooling plate 16, a refrigerant path 16a through which the refrigerant flows is provided.
[0022]
A gas baffle plate (partition plate) 26 made of aluminum is disposed around the substrate holder 12. A quartz cover 28 is provided on the upper surface of the gas baffle plate 26. A gas nozzle 22 for introducing a gas used for the plasma processing is provided on the inner wall of the processing container 11. Similarly, a coolant channel 24 is formed inside the inner wall of the processing container 11 so as to surround the entire container.
[0023]
FIG. 3 shows a state in which the planar antenna 14 of FIG. 2 is viewed from the object side. A feeding portion 15d is disposed around a radius position that is approximately half the radius of the planar antenna 14. The planar antenna 14 is formed with a “C” -shaped slot pair 14 a in a spiral shape. Here, the slot pair 14a is right-handed inside the antenna 14 and left-handed outside. In addition, as the shape of the slot, an X shape, a straight line shape, an arc shape, or the like can be used depending on the situation.
[0024]
FIG. 4 shows how the microwave propagates in the planar antenna 14. As indicated by the arrows in FIG. 4, the microwave propagates from near the power supply portion 15d toward the central portion and the peripheral portion. As it propagates, microwaves leak from the slots into the processing container 11.
[0025]
When performing processing using the plasma processing apparatus 10, first, after setting the silicon wafer W in the processing container 11 of the plasma processing apparatus 10, the air inside the processing container 11 is exhausted through the exhaust ports 11 </ b> A and 11 </ b> B. Exhaust is performed, and the inside of the processing container 11 is set to a predetermined processing pressure. Thereafter, a predetermined mixed gas (inert gas, oxygen gas, nitrogen gas, etc.) is introduced from the gas nozzle 22 into the processing container 11 in which the silicon wafer W is set (loaded).
[0026]
On the other hand, for example, a microwave having a frequency of 2.45 GHz supplied through the waveguide portion 15c of the waveguide 15 is formed on one surface of the connection portion 15b, the feeding portion 15d, the waveguide 15a, and the planar antenna 14. It is introduced into the processing container 11 through the slot and the dielectric plate 13. This microwave excites the plasma generation gas to generate plasma. The high-density plasma generated by microwave excitation in the processing container 11 performs plasma processing such as forming an oxide film on the surface of the silicon wafer W.
[0027]
FIG. 5 shows another embodiment of the waveguide 15a. The aforementioned waveguide 15a is hollow or made of a dielectric, but in this example, an absorbing material 17 that absorbs electromagnetic waves (microwaves) is disposed at least on the inner peripheral side wall surface portion thereof. The absorber 17 is composed of a radio wave absorber mainly composed of, for example, SiC (silicon carbide). The absorber 17 can prevent the microwaves reaching the inner wall of the waveguide 15a from being reflected and interfering. The absorber 17 can also be disposed in the central portion of the waveguide 15a. Thus, when the microwave radiated from the power supply unit 15d reaches the center of the waveguide 15a, reflection and interference due to the concentrated microwave can be prevented.
[0028]
FIG. 6 shows another example of the slot formed in the planar antenna. The planar antenna 114 shown in FIG. 6 has slots 114a which are microwave introduction paths formed radially. The slot 114a has an interval set according to the wavelength of the introduced electromagnetic wave (microwave). Depending on the design of the slot on the antenna surface, it may be approximately a natural number multiple of half the guide wavelength. In this example, specifically, the pitch is set to one wavelength of electromagnetic waves. In the figure, reference numeral 115d denotes a power feeding unit.
[0029]
FIG. 7 shows another example of the planar antenna 34 of the present invention. The antenna 34 is used in a plasma processing apparatus that processes a rectangular LCD substrate. The planar antenna 34 is formed in a rectangular shape according to the shape of the LCD substrate. The waveguide 36 is connected to the vicinity of the center of the surface opposite to the surface on which the slot of the planar antenna 14 is formed, thereby forming a feeding portion 38. The electromagnetic wave introduced from the power supply unit 38 propagates from the center to the left and right as indicated by arrows. The slot formed in the antenna 34 is preferably arranged at a position that is approximately a natural number times the in-tube wavelength of the antenna. Even in the case of a rectangular planar antenna as in this embodiment, the same effects as those of the circular antenna described above can be obtained.
[0030]
As mentioned above, although the Example (embodiment) of the present invention has been described based on some examples, the present invention is not limited to these Examples at all, and the technical idea shown in the claims. It can be changed in the category.
[0031]
【The invention's effect】
As described above, according to the present invention, the microwave is supplied to the antenna from a portion between the central portion and the outer periphery instead of the center of the antenna. To leak from the slot. For this reason, since the propagation distance of the microwave is about half that of the conventional one, the phase shift during propagation can be greatly reduced.
[0032]
In addition, since the waveguide of the present invention is provided with a tapered portion in the power feeding portion, it is possible to obtain a waveguide with high radiation efficiency with less microwave interference in the waveguide. Further, since the radio wave absorber is disposed on the inner peripheral wall surface portion of the waveguide, when the microwave radiated from the power supply port reaches the inner peripheral wall surface or the central portion in the waveguide, Reflection can be prevented. Further, since the slot of the planar antenna is formed in a square shape, the propagated microwave is uniformly radiated as circularly polarized waves into the processing apparatus.
[0033]
[Brief description of the drawings]
FIG. 1 is a schematic view (cross-sectional view) showing a configuration of a plasma processing apparatus according to an embodiment of the present invention.
FIG. 2 is an enlarged view showing a configuration of a main part in the plasma processing apparatus according to the embodiment of FIG. 1;
FIG. 3 shows a state in which the configuration in the main part enlarged view of FIG. 2 is viewed from the planar antenna side.
FIG. 4 is an explanatory diagram showing how a microwave propagates in the present embodiment.
FIG. 5 is a cross-sectional view showing a configuration of a waveguide of a plasma processing apparatus according to another embodiment of the present invention.
FIG. 6 is a plan view showing a configuration of a planar antenna of a plasma processing apparatus according to another embodiment of the present invention.
FIG. 7 is a plan view showing a configuration of a planar antenna of a plasma processing apparatus (for an LCD glass substrate) according to still another embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Plasma processing apparatus 11 Plasma processing container 14 Planar antenna 14a, 14b Slot 15 Waveguide 15b Connection part 15a Waveguide 15c Waveguide part 15d Feed part 15e, 15g Metal plate 17 Wave absorber W Silicon wafer

Claims (13)

A processing container containing a substrate to be processed inside;
An electromagnetic wave generator for generating electromagnetic waves for plasma excitation;
An antenna that radiates the electromagnetic wave into the processing vessel and generates plasma;
A waveguide for guiding the electromagnetic wave generated by the electromagnetic wave generator to the antenna,
The antenna is formed with a feeding portion for introducing power from the waveguide and a plurality of slots formed on the opposite surface of the feeding portion,
The power feeding unit is formed at a position where the propagation distance of the electromagnetic wave propagating through the antenna becomes short,
An electromagnetic wave is radiated from the slot of the antenna into the processing container. 2. The plasma processing apparatus according to claim 1, wherein in the antenna, an outer peripheral portion of a space in which electromagnetic waves propagate is circular, and a surface on which the slot is formed is substantially flat on the substrate to be processed side. . 3. The plasma processing apparatus according to claim 2, wherein in the antenna, the power feeding unit is disposed near an intermediate portion between a center portion and an outer edge portion of the antenna. The plasma processing apparatus according to claim 2 or 3, wherein the outermost peripheral portion of the antenna is surrounded by a metal body, and electromagnetic waves propagating through the antenna do not leak to the outside from the outer peripheral portion. The plasma processing apparatus according to claim 4, wherein a metal body that prevents a propagating electromagnetic wave from propagating across the central portion is provided at a central portion of the antenna. The plasma processing apparatus according to claim 4, wherein the metal body is cylindrical or columnar. The plasma processing apparatus according to claim 2, 3, 4, 5, or 6, wherein an absorbing material that absorbs electromagnetic waves is disposed on an outermost peripheral portion of the antenna. The plasma processing apparatus according to claim 7, wherein an absorbing material that absorbs electromagnetic waves is disposed in an innermost peripheral portion of the antenna. 6. The waveguide according to claim 2, wherein the waveguide is formed in a taper shape that expands toward the feeding portion in order to optimally match the load between the waveguide and the antenna. , 6, 7 or 8. The antenna is rectangular;
The plasma processing apparatus according to claim 1, wherein the slot is formed on a surface on the processing container side. The plasma processing apparatus according to claim 10, wherein the power feeding unit is disposed near a position that bisects the antenna on a surface opposite to a surface on which the slot is formed. The plasma processing apparatus according to claim 10 or 11, wherein both ends of the antenna are surrounded by a metal body, and electromagnetic waves propagating through the antenna do not leak to the outside from the ends. The plasma processing apparatus according to claim 10, wherein an absorbing material that absorbs electromagnetic waves is disposed at an end portion of the space of the antenna.

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