JP2002093597A - Plasma-generating antenna, plasma treatment apparatus, plasma treatment method, production method of object to be treated and production method of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To conduct plasma treatment using a plasma-generating antenna conformable to any shape of an object to be treated. SOLUTION: The plasma-generating antenna 10 has a structure of a fixable cable in which a conductor is inserted into the interior of a dielectric. When high-frequency power ranging from a VHF band to a UHF band (for example, 149 MHz) is supplied to the plasma-generating antenna 10, an electric field is concentrated on the surface of the dielectric to propagate the surface wave through the surface of the dielectric, whereby the surface plasma is generated on the outside of the dielectric by the surface wave. The plasma-generating antenna is arranged in a vacuum chamber, a reactive gas is introduced into the vacuum chamber, and electric power is supplied to the plasma-generating antenna, whereby the surface plasma is generated on the outside of the dielectric. An object to be treated can be treated with the reactive gas by the surface plasma.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma generating antenna for generating a surface wave plasma, a plasma processing apparatus having the plasma generating antenna, and an object to be processed by a surface wave plasma generated from the plasma generating antenna. The present invention relates to a plasma processing method for performing plasma processing, a method for manufacturing an object having a step of performing plasma processing on an object, and a method for manufacturing a semiconductor device having a step for performing plasma processing on a semiconductor wafer.

[0002]

2. Description of the Related Art Technologies for performing plasma processing such as formation and etching of a thin film using reactive plasma from a high-density and large-area plasma source have been developed. Among them, surface wave plasma (SWP: Surf) generated by transport of surface wave
ace Waved Produced Plasma) has a feature that it is easy to increase the area of high-density plasma.

Conventionally, as a technique for generating a large area surface wave plasma, for example, as shown in FIG.
, A fluorocarbon polymer sheet 202 is disposed in the waveguide 201, and a dielectric plate 203 such as ceramic is disposed on the bottom surface of the waveguide 201.
In some cases, a surface wave plasma is generated in the vacuum chamber 204 from the dielectric plate 203 by a microwave propagating through the substrate, and an object to be processed disposed in the vacuum chamber 204 is plasma-processed.

[0004]

According to the prior art shown in FIG. 18, it is easy to increase the area of high-density plasma, and if a large-diameter semiconductor wafer is set as an object to be processed in the vacuum chamber 204, The plasma processing can be easily performed. However, this technique can only generate plasma from a certain direction. For this reason, for example, it is not possible to generate plasma of an arbitrary shape in conformity with an object to be processed of an arbitrary shape.

The present invention has been made in view of the above problems, and has as its object to provide a plasma generating antenna having a novel structure.

It is another object of the present invention to provide a plasma generating antenna which can be used for an object having an arbitrary shape.

Another object of the present invention is to provide a plasma processing apparatus, a plasma processing method, a method of manufacturing an object to be processed, and a method of manufacturing a semiconductor device using such a plasma generating antenna.

[0008]

An antenna for plasma generation according to the present invention has a cable structure in which a conductor is buried in a dielectric, and a surface wave is generated by supplying power. Is characterized in that the antenna for plasma generation is configured to propagate on the surface of the substrate and generate plasma outside the dielectric material by surface waves.

This plasma generating antenna has a cable structure in which a conductor is buried inside a dielectric, and has a novel structure which does not exist in the past and generates a surface wave plasma outside.

Further, the present invention has a cable structure in which a conductor is buried inside a dielectric, and the dielectric is exposed at least in a portion of the dielectric which generates surface wave plasma outside the dielectric. It is characterized by the antenna for plasma generation described above.

In this case, the cable may be entirely exposed or partially exposed in the axial direction. Also,
If the exposed portion is exposed in the entire cross-sectional direction of the cable, surface wave plasma can be generated around the cable, but if the exposed portion is partially exposed in the cross-sectional direction, the surface wave can be generated only in that direction. Plasma can be generated.

If the above-mentioned cable structure is made flexible, plasma can be generated according to the shape of the object to be plasma-processed.

Further, the present invention is characterized by a plasma processing apparatus for performing plasma processing on an object to be processed using the above-described antenna for plasma generation.

According to the present invention, the plasma generating antenna and the object to be processed are arranged in a vacuum chamber, a reactive gas is introduced into the vacuum chamber, and power is supplied to the plasma generating antenna. The present invention is characterized by a plasma processing method in which a surface wave plasma is generated outside a dielectric material, and an object to be processed is plasma-processed using a reactive gas by the surface wave plasma.

In this plasma processing, the plasma generating antenna is, for example, as shown in an embodiment described later,
It is arranged in a spiral or hairpin shape so as to face the workpiece. Alternatively, they are arranged three-dimensionally around the workpiece.

The above-described plasma processing method can be used not only as one step of manufacturing an object to be processed, but also as one step of manufacturing a semiconductor device by performing plasma processing on a semiconductor wafer.

[0017]

FIG. 1 shows an external configuration of a plasma generating antenna 10 according to one embodiment of the present invention. FIG. 2 shows a partial cross-sectional configuration in the axial direction.

The antenna 10 for plasma generation has a cable structure in which a conductor 12 is buried as a conductor inside a dielectric (for example, polyethylene) 11, and a connector 13 is provided at one end of the antenna, and is electrically connected to the outside. I can do it. That is, the plasma generating antenna 10 in this embodiment leaves a part of the earth outer conductor of the coaxial cable (the remaining earth outer conductor is denoted by reference numeral 1).
4), the ground outer conductor of the other part is removed and the dielectric 11 is exposed. Since the plasma generating antenna 10 has a flexible cable structure, it can have any shape other than the spiral shape as shown in FIG.

The plasma generating antenna 10 is disposed in a vacuum chamber (shown by a broken line in FIG. 2) 20 as will be described later.
At 4, it is fixed to the vacuum chamber 20. This fixing is performed using a flange or the like with an O-ring interposed.

In the plasma generating antenna 10 configured as described above, the VHF band (for example, 149 MHz) is applied from one end with the one end provided with the connector 13 as a power supply portion and the other end as open (or ground). 3), the electric field is concentrated on the surface of the dielectric 11, and as shown in FIG. 3A, a surface wave (indicated by a solid line in FIG. Propagation in coaxial mode. Note that ± in the figure indicates accumulated charges.
The surface wave generates a surface wave plasma outside the dielectric 11.

Since the surface wave plasma acts as a shield for radio waves, the radio waves are reflected by the surface wave plasma inside the antenna, that is, travel in the axial direction of the antenna using the surface wave plasma as a guide. The radio wave traveling inside the antenna is a TEM mode wave.
As shown in (b), the electric field E _R is directed in the radial direction of the antenna, and the magnetic field Hθ is generated in the circumferential direction of the antenna. As the radio wave travels in the axial direction of the antenna, it attenuates due to surface wave plasma generation loss. For this reason, the density of the surface wave plasma generated outside the plasma generating antenna 10 is higher on the power supply side in the axial direction of the antenna and decreases as the distance from the power supply side decreases.

The plasma generating antenna 1 of this embodiment
0 can be understood from the following description. In the early days of the plasma generating antenna, as shown in FIG. 4A, a dielectric was formed inside a conductor, and a power was supplied to the conductor to generate a surface wave plasma inside the dielectric. I was When this is cut in the axial direction and expanded outward,
As shown in FIG. 4 (b), a dielectric material and a conductor are laminated to form a flat plate, and surface wave plasma is generated on the opposite side of the conductor in the dielectric. This flat type is realized as a plasma generating antenna using the waveguide 201 shown in FIG. On the other hand, as shown in FIG.
The structure shown in (b) is rounded with the conductor inside, that is, the outer periphery of the conductor is covered with a dielectric. In this case, the plasma is generated outside the dielectric. 4A to 4C are cross-sectional views of the antenna for plasma generation.

Next, a description will be given of a study performed for realizing the plasma generating antenna 10 of this embodiment. FIG. 5 shows an outline of the apparatus used for the study.

As shown in the drawing, a plasma generating antenna 10 having the structure shown in FIGS. 1 and 2 is linearly arranged in a vacuum chamber 20 and has a length of 170 mm in the vacuum chamber 20.
cm. Also, three probes 41, 51, 61 are set in the vacuum chamber 20.

The probe 41 detects the ion saturation current flowing through the probe by changing the distance Z from the power supply wall 21 of the vacuum chamber 20 to a radial distance R from the center axis of the plasma generating antenna 10 of 3 cm. The probe 51 has a distance Z of 94 cm and a distance R
Is changed to detect the ion saturation current. The probe 61 is composed of probes for measuring the electric field and the magnetic field, and detects the electric field and the magnetic field by changing the distance R. The ion saturation current is
It is proportional to the density of the plasma. Probe measuring device 4
2 and 52 measure the ion saturation current using the probes 41 and 51, respectively, and the electric and magnetic field measuring device 62 measures the electric and magnetic fields using the probe 61.

Next, in order to perform the measurement, an inert gas (for example, Ar) is introduced into the vacuum chamber 20, the inside of the vacuum chamber 20 is depressurized, and the high-frequency power source 30 supplies 900 W of high-frequency power (frequency: 149 MHz) to the plasma generating antenna 10.

FIG. 6 shows a measurement result of the ion saturation current Ii with respect to the distance Z from the power supply wall 21 (measured by the probe measuring device 42). This measurement is performed by setting the pressure P in the vacuum chamber 20 to 0.4 Torr, 0.2 Torr,
The test was performed for each of 0.13 Torr and 0.06 Torr. From this figure, it can be seen that plasma is generated from the plasma generation antenna 10 and its density is high near the power supply wall 21. Note that the graph is W-shaped because radio waves are reflected by the power supply wall 21 and become standing waves. Further, the pressure P in the vacuum chamber 20 is set to 0.4 Torr, 0.2 Torr, 0.13 T
orr, 0.06 Torr, the wavelength λ _Z of the radio wave propagating on the inner surface of the plasma generating antenna 10 is
1.22m, 1.20m, 1.14m, 1.1 respectively
0 m.

FIG. 7 shows the ion saturation current Ii with respect to the radial distance R from the center axis of the plasma generating antenna 10.
(Measured by the probe measuring device 52). From this figure, it can be seen that the radial distance of the plasma generating antenna 10 increases, that is, the plasma density decreases as the distance from the plasma generating antenna 10 increases.

Next, in order to obtain a theoretical value corresponding to the measured value using the model shown in FIG.
With respect to the radial distribution of z and the radial distribution of the circumferential component Hθ of the magnetic field strength, respective distributions are obtained based on the measured values by the electric field magnetic field measurement device 62, and the respective distributions of the model are obtained using the finite element method. A calculation was made.

FIGS. 8 and 9 show an antenna 1 for plasma generation.
Electric field strength E with respect to radial distance R from the central axis of zero
The measured values of z and the magnetic field strength Hθ are indicated by broken lines. In addition, among the solutions obtained by the finite element method, the solution of the calculated value substantially matching the measured value is shown by a solid line in the figure.

Using the solution obtained in this way, the antenna length through which the surface wave propagates was analyzed. As a result, it was concluded that if the plasma frequency (proportional to the density) of the surface wave plasma is lower than the frequency of the surface wave in the propagation direction where the plasma density gradient exists, that is, in the axial direction of the antenna, the surface wave cannot be propagated. Was. Then, the antenna length was determined using the density gradient and the collision frequency due to the collision of electrons and neutral gas as parameters. Specifically, when the supplied power is 900 W, the antenna length can be 7 m. Note that the antenna length over which the surface wave propagates can be lengthened in proportion to the power supplied to the antenna.

Next, the plasma generating antenna 10 was set in a spiral shape as shown in FIG. 10 in a length of 7 m and placed in the vacuum chamber 20 to conduct an experiment for increasing the area of high-density plasma. In this experiment, the spiral plasma generating antenna 10 is arranged in the vacuum chamber 20, and the probe 71 is positioned above the plasma generating antenna 10 (upward perpendicular to the paper) by a distance Zp. Then, the probe 71 is moved radially from the center of the spiral (for example, in the horizontal direction on the paper), and the ion saturation current at each position is measured by the probe measuring device 72. In this experiment, an inert gas (for example, Ar) was introduced into the vacuum chamber 20, the inside of the vacuum chamber 20 was depressurized, and high-frequency power of 900 W (frequency: 149 MHz) was generated from the high-frequency power supply 30 to generate plasma. To the antenna 10.

In this experiment, the ion saturation current Ii when the spiral shape of the plasma generating antenna 10 was variously changed was measured.

When the spiral of the plasma generating antenna 10 is densely wound on the outside as shown in FIG.
As shown in (b), the ion saturation current Ii increases in the radial direction from the center of the spiral. The spiral of the plasma generating antenna 10 is shown in FIG.
As shown in FIG. 12A, when the degree of making the outside denser is smaller than that in FIG. 11A, as shown in FIG.
Ion saturation current I from the center of the spiral to its radial direction
The change in i becomes smaller. When the spiral of the plasma generating antenna 10 is uniformly wound as shown in FIG. 13A, the ion saturation current Ii is substantially constant up to a certain distance from the center of the spiral as shown in FIG. , The ion saturation current Ii greatly changes outside the spiral. The spiral of the plasma generating antenna 10 is shown in FIG.
When power is supplied uniformly from the center of the spiral as shown in FIG. 14A, as shown in FIG. 14B, the ion saturation current Ii becomes maximum in the direction in which the feeder is present near the center of the spiral. As the distance increases, the ion saturation current Ii decreases.

From the above results, it is possible to increase the area of the high-density plasma by using the plasma generating antenna 10 and to change the spiral shape of the plasma generating antenna 10 so that the ion saturation current Ii in the radial direction can be increased. It was confirmed that the distribution pattern could be changed.

FIG. 15A shows a schematic configuration in a case where the plasma generating antenna 10 wound in a spiral is disposed in the vacuum chamber 20 and the object 101 is subjected to plasma processing.

The plasma generating antenna 10 is arranged to face the object 101 to be processed. In the drawing, the plasma generating antenna 10 is shown as being inclined with respect to the workpiece 101, but this is to indicate that the plasma generating antenna 10 is spirally wound. In practice, the antenna 10 for plasma generation is
01, that is, two-dimensionally arranged in a direction perpendicular to the paper surface. In this case, the plasma generating antenna 10
The holding member, for example, is fixed to an insulator frame (for example, a ceramic rod) 81 as shown in FIG.
0.

Then, an inert gas (for example, Ar) and a reactive gas are supplied from a gas supply device (not shown) to the vacuum chamber 20.
And the inside of the vacuum chamber 20 is, for example, 10 ^{−4 to} 0.
Maintain at 1 Torr. Also, the high frequency power supply 30 to 90
A high-frequency power of 0 W (frequency is 149 MHz) is supplied to the plasma generating antenna 10. As a result, surface wave plasma is generated from the plasma generation antenna 10,
The object to be processed 101 is subjected to plasma processing.

This plasma processing is used to plasma-etch the object 101 or to form a thin film on the object 101 by supplying a reactive gas according to the purpose. In this case, the plasma processing of the object to be processed 101 can be appropriately performed according to the purpose.
For example, when a product such as a golf head is developed, a plasma process is performed on the product for the development, or a plasma process (for example, an etching process or a thin film forming process) is performed as one of the processes for manufacturing the workpiece 101. Etc.). When a semiconductor chip (semiconductor device) is manufactured, a semiconductor wafer is placed in the vacuum chamber 20 as the object to be processed 101 and plasma processing (for example, etching, ion implantation, thin film formation, etc.) is performed, and finally It can also be used as one step when manufacturing a semiconductor chip.

In the example shown in FIG. 15, since plasma is also generated from the plasma generation antenna 10 on the side opposite to the object 101, the plasma generation antenna 10
It is also possible to simultaneously perform the plasma processing of the object to be processed 101 on both sides.

FIG. 16 shows a schematic configuration in a case where a plasma-generating antenna 10 wound in a hairpin shape is arranged in a vacuum chamber 20 and an object to be processed is subjected to plasma processing.

In this example, as shown in the figure, the plasma generating antenna 10 is fixed to an insulator frame (for example, a ceramic rod) 82 as a holding member and arranged in the vacuum chamber 20. Then, an object to be processed (not shown) is disposed above the plasma generating antenna 10 (upward perpendicular to the paper surface), and an inert gas (for example, Ar) and a reactive gas are supplied from a gas supply device (not shown). The vacuum chamber 2
0, and the inside of the vacuum chamber 20 is, for example, 10 ⁻⁴ to
While maintaining the pressure at 0.1 Torr, high-frequency power (frequency is 149 MHz) of 900 W is supplied from the high-frequency power source 30 to the plasma generating antenna 10 to perform plasma processing on the object to be processed.

In the case of this example, for example, it can be used to deposit silicon (Si) on a glass substrate (workpiece) for a solar cell.

FIG. 17A shows a schematic configuration in a case where the plasma generation antenna 10 is three-dimensionally arranged around the object 102 to perform the plasma processing.

In this example, as shown in the side view of FIG. 17B, the plasma generating antenna 10 is wound in a coil shape around four rods 83 as a holding member. The object to be processed 102 is the plasma generating antenna 1
0 in the coil shape as shown in FIGS. 17 (a) and (b). In this state, an inert gas (for example, Ar) and a reactive gas are introduced into the vacuum chamber 20 from a gas supply device (not shown).
^{-4 to} 0.1 Torr.
High frequency power of 0 to 900 W (frequency is 149 MHz)
Is supplied to the antenna 10 for plasma generation, and
02 is subjected to plasma processing.

In the case of this example, the plasma generating antenna 10 can be arranged so as to surround the object 102 of any shape, so that the outer surface of the object 102 is Can be processed.

In the various embodiments described above,
Although the dielectric 11 of the plasma generating antenna 10 is exposed in all directions in the circumferential direction, only the portion necessary for generating the surface wave plasma may be exposed. For example, only the lower semicircular portion and the upper semicircular portion of the dielectric 11 in the circumferential direction may be exposed.

The dielectric 11 does not need to be made of one material, but may be made of a laminated structure of a plurality of dielectric materials. For example, a structure in which a dielectric material made of polyethylene is coated with a dielectric material resistant to heat, for example, may be used. The dielectric 11 is not limited to a circular cross-section, but may have a triangular cross-section or a quadrangular cross-section.

The plasma generating antenna 10 preferably has a flexible structure in order to generate an arbitrary-shaped plasma. However, as shown in FIGS. 15 and 16, the shape of the object to be processed is constant. In the case of, it may not be flexible and may have a fixed shape. in this case,
Ceramic or the like can be used as the dielectric material.

The power supplied to the plasma generating antenna 10 may be high-frequency power in the VHF band to the UHF band. When such high-frequency power is used, high-density plasma having a relatively low electron temperature can be generated. Further, since the TEM wave basically propagates inside the antenna, there is no limitation on the frequency of the supplied power.

[Brief description of the drawings]

FIG. 1 is a diagram showing an external configuration of a plasma generating antenna 10 according to an embodiment of the present invention.

FIG. 2 is a diagram showing a cross-sectional configuration of the plasma generating antenna 10 shown in FIG.

FIG. 3 is a plasma generating antenna 10 shown in FIGS. 1 and 2;
It is a figure for explaining operation of.

FIG. 4 is a diagram for explaining the structural features of the plasma generating antenna 10 of the present embodiment.

FIG. 5 is a diagram showing an outline of an apparatus used for studying the plasma generation antenna 10 of the present embodiment.

6 is a diagram showing a measurement result of an ion saturation current Ii with respect to a distance Z from a power supply wall 21 in a measurement using the device shown in FIG.

7 is a diagram showing a measurement result of an ion saturation current Ii with respect to a radial distance R from a center axis of the plasma generation antenna 10 in a measurement using the apparatus shown in FIG. 5;

FIG. 8 is a diagram showing measured values and calculated values of the electric field strength Ez with respect to a radial distance R from the central axis of the plasma generating antenna 10.

9 is a diagram showing measured and calculated values of the magnetic field strength Hθ with respect to a radial distance R from the center axis of the plasma generating antenna 10. FIG.

FIG. 10 is a diagram showing an apparatus used in an experiment for increasing the area by the plasma generation antenna 10 of the present embodiment.

11 shows the ion saturation current Ii with respect to the radial distance R from the center of the spiral when the spiral of the plasma generating antenna 10 is densely wound on the outside using the apparatus shown in FIG.
It is a figure showing the measurement result of.

12 is a graph showing the relationship between the radial distance R from the center of the spiral when the spiral of the plasma generating antenna 10 is made smaller in the degree to make the outer side denser than that shown in FIG. 11 using the apparatus shown in FIG. It is a figure showing the measurement result of ion saturation current Ii.

13 is a diagram showing a measurement result of an ion saturation current Ii with respect to a radial distance R from the center of the spiral when the spiral of the plasma generating antenna 10 is uniformly wound using the apparatus shown in FIG. 10;

FIG. 14 is a graph showing the measurement of the ion saturation current Ii with respect to the radial distance R from the center of the spiral when the spiral of the plasma generating antenna 10 is uniformly wound and power is supplied from the center of the spiral using the apparatus shown in FIG. It is a figure showing a result.

FIG. 15 is a spirally wound plasma generating antenna 1.
FIG. 2 is a diagram showing a schematic configuration in a case where an object to be processed 101 is subjected to plasma processing by disposing 0 in a vacuum chamber 20.

FIG. 16 is a diagram showing a schematic configuration in a case where a plasma-generating antenna 10 wound in a hairpin shape is disposed in a vacuum chamber 20 and an object to be processed is subjected to plasma processing.

FIG. 17 is a diagram showing a schematic configuration in a case where a plasma generation antenna 10 is three-dimensionally arranged around a workpiece 102 to perform plasma processing.

FIG. 18 is a diagram showing a configuration of a conventional plasma processing apparatus.

[Explanation of symbols]

10 ... plasma generating antenna, 11 ... dielectric, 12 ...
Conductors, 13 connectors, 20 vacuum chamber, 30 high frequency power supply (power supply means), 101, 102 workpiece.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) H01L 21/3065 H01L 21/302 BF Term (Reference) 4G075 AA24 AA30 BC04 BC05 BC06 BC08 CA47 DA02 EB41 EC30 EE31 FA11 FA20 FC11 FC15 4K030 BA29 CA04 CA06 CA12 FA01 KA30 KA45 LA16 4K057 DA16 DD01 DE14 DM06 DM28 DM40 5F004 AA01 BB11 DA23 5F045 AB02 AC16 BB01 CA13 EH02 EH11

Claims (7)

[Claims] 1. A cable structure in which a conductor is buried in a dielectric, wherein a surface wave propagates on the surface of the dielectric when electric power is supplied, and the dielectric material is caused by the surface wave. An antenna for generating plasma configured to generate plasma outside of the antenna. 2. A cable structure in which a conductor is embedded in a dielectric, wherein the dielectric is exposed at least in a portion of the dielectric that generates surface wave plasma outside the dielectric. An antenna for generating plasma, comprising: 3. The antenna according to claim 1, wherein the cable structure is flexible. 4. A vacuum chamber, the antenna for plasma generation according to claim 1, disposed in the vacuum chamber, and a power supply unit for supplying power to the antenna for plasma generation. An apparatus for introducing a reactive gas into the vacuum chamber. 5. The plasma generating antenna according to claim 1 and an object to be processed are arranged in a vacuum chamber, and a reactive gas is introduced into the vacuum chamber and the plasma is generated. A plasma processing method comprising: supplying power to an antenna for use to generate surface wave plasma outside the dielectric; and performing plasma processing on the object using the reactive gas by the surface wave plasma. 6. A plasma generating antenna according to claim 1 and an object to be processed are arranged in a vacuum chamber, and a reactive gas is introduced into the vacuum chamber and the plasma is generated. Supplying electric power to the antenna for use to generate a surface wave plasma outside the dielectric, and plasma-treating the object using the reactive gas with the surface wave plasma. Manufacturing method of processed material. 7. A method of manufacturing a semiconductor device using a semiconductor wafer, wherein the antenna for plasma generation according to claim 1 and the semiconductor wafer are arranged in a vacuum chamber. And introducing a reactive gas into the vacuum chamber and supplying power to the antenna for plasma generation, generating a surface wave plasma outside the dielectric, and using the reactive gas by the surface wave plasma. A method of manufacturing a semiconductor device, comprising a step of subjecting the semiconductor wafer to plasma processing.