JPH01181513A - Plasma cvd apparatus - Google Patents

Abstract

PURPOSE:To enable a film of a large area to be formed using a high-frequency power supply by forming a pair of electrodes for discharge by aligning a plurality of column bodied with a circular or elliptic sectional area. CONSTITUTION:With mesh electrodes 12 and 13 for generating glow discharge plasma, two stages of electrodes in parallel mesh shape wherein columns are arranged are piled up and are laid out so that the column part member may not overlap each other when viewed from one surface. It allows the surface area to be extended for several times as compared with the conventional parallel plain plate electrode and electrostatic capacity between opposing electrodes becomes extremely small to allow discharge impedance to be increased. As a result, voltage effect becomes extremely small, voltage distribution is eliminated, an electrode with a length which is several times longer than that of parallel plain plate electrode can be used, and amorphous thin film with a large area can be produced.

Description

[Detailed description of the invention] The present invention relates to solar cells, fuel cells, and thin film semiconductors.

The present invention relates to a plasma CVD apparatus suitable for manufacturing large-area thin films used in various electronic devices such as electrophotographic photoreceptors and optical sensors.

[Prior Art] Fig. 12 is a cross-sectional view showing the configuration of a conventionally used large-area thin film manufacturing apparatus, and its technical means are disclosed, for example, in Japanese Patent Application No. 106314/1983. This is a known technique. In the figure, reference numeral 1 denotes a reaction vessel, in which electrodes 2 and 3 for generating glow discharge plasma are arranged in parallel. 4 is a low frequency power supply, for example 6
Power at a commercial frequency of 0 Hz is supplied to the electrode 2.3. Note that the low frequency power source 4 may be a direct current or high frequency power source. The coil 5 is wound so as to surround the reaction vessel 1, and is supplied with AC power from an AC power source 6. Reference numeral 7 denotes a reaction gas introduction pipe, which communicates with a cylinder (not shown) and supplies a mixed gas of monosilane and argon to the reaction vessel 1. Exhaust hole 8
is in communication with the vacuum pump 9, and is used to exhaust the gas in the reaction vessel 1.

Now, when manufacturing a thin film, the substrate 10 is supported by appropriate means in a posture perpendicular to the plane of the electrode 2.3 and outside the discharge space formed by the electrode 2.3, as shown in the figure. After driving the vacuum pump 9 to exhaust the inside of the reaction vessel 1,
A mixed gas of monosilane and argon is supplied from the reaction gas introduction pipe 7.

[Reaction container] The pressure of the mixed gas filled in the reaction vessel is maintained at 0.05 to 0.5 Torr, and the low frequency power source 4 is connected to the electrode 2,
When voltage is applied to 3, glow discharge plasma is generated. On the other hand, an AC voltage of, for example, 100 Hz is applied to the coil 5 to generate a magnetic field B in a direction perpendicular to the electric field E generated between the electrodes 2 and 3. The magnetic flux density in this magnetic field is 10
Gauss is fine.

Among the gases supplied from the reactive gas introduction tube 7, monosilane gas is decomposed into radicals St by the glow discharge plasma generated between the electrodes 2.3, and adheres to the surface of the substrate 10 to form a thin film. At this time, charged particles such as argon ions are affected by the Coulomb force F due to the electric field E between the electrodes 2.
A so-called E-B drift motion is caused by IWqE and Lorentz force F2-q (VllB). Note that V is the velocity of charged particles.

In this way, the charged particles fly in a direction perpendicular to the electrode 2.3 and fly toward the substrate 10 while being given an initial velocity by the E-B drift. However, in the discharge space where the influence of the electric field generated between the electrodes 2 and 3 is small, the Larm
It flies in an orbit. Therefore, charged particles such as albo ions rarely hit the substrate 10 directly.

On the other hand, radical Si, which is electrically neutral, is not affected by the magnetic field B, deviates from the trajectory of the charged particle group, reaches the substrate 10, and forms an amorphous thin film on the surface thereof. In the above case, radical Si is a charged particle flying in La rmo r orbit.
Because of the collision with the particles, an amorphous thin film is formed not only in front of the electrode 2°3 but also in a form that spreads to the left or right. Furthermore, since the magnetic field B is varied by the AC power source 6, it is possible to uniformly form an amorphous thin film on the surface of the substrate 10. Note that the length of the electrode 2.3 can be made as long as the length of the reaction vessel 1 allows without any problem, so even if the substrate 10 is long, it is possible to form a uniform amorphous thin film on its surface. It becomes possible to form.

[Problem to be solved by the invention]

In the conventional apparatus described above, by generating a magnetic field B in a direction perpendicular to a discharge electric field E between electrodes that generates glow discharge plasma, it is possible to easily form a film over a large area. However, there are the following problems.

■When forming a film over a large area, it is necessary to use a long electrode. In order to generate stable plasma using a long electrode, it is easier to keep the frequency of the power source as low as possible, so it is easier to generate stable plasma using a power source with a frequency of several tens of Hz to several hundred kilograms.
A Hz power source is used.

However, under conditions where the frequency is low and the ion travel distance during a half cycle exceeds the electrode spacing, secondary electrons are emitted from the cathode by ion collisions to maintain the plasma, just as in the case of DC discharge. will play an essential role. Therefore, when a film is attached to the electrode and insulated,
No discharge will occur in that area. Therefore, in this case, it is necessary to keep the electrode surface clean at all times. Therefore, complicated operations such as frequent replacement of the electrodes or frequent cleaning of the electrodes are required, which is one of the causes of high costs.

■If a high frequency power source of, for example, 13.56 MHz is used as the plasma generation power source to compensate for the drawback of (■) above, the secondary electrons emitted from the electrodes will no longer be essential for sustaining the discharge.
Even if an insulating material such as a film is present on the electrodes, a glow discharge is formed between the electrodes.

However, when using long electrodes, most of the current is transferred to the surface (approximately 0.0111I) due to the skin effect caused by high frequency.
I), the electrical resistance will increase. For example, when the length of the electrode is about 1 m or more, a potential distribution appears on the electrode and -like plasma is no longer generated. In other words, when considered in terms of a distributed constant circuit, it becomes as shown in FIG. That is, when the resistance R per unit length of the electrode becomes so large that it cannot be ignored compared to the impedance ZI+Z2..., Zn of the discharge portion, a potential distribution appears within the electrode. Note that X indicates the distance in the length direction of the electrode. Therefore, when using a high frequency power source, it is extremely difficult to form a film over a large area, and this has not been practically possible until now.

[Means for Solving the Problems] In order to solve the above problems and achieve the objects, the present invention takes the following measures. That is, a reaction vessel, a means for introducing a reaction gas into the reaction vessel under reduced pressure, a pair of discharge electrodes housed opposite each other in the reaction vessel, and a glow discharge to the discharge electrode. a coil that surrounds the discharge electrode and generates a magnetic field in a direction perpendicular to the electric field generated between the discharge electrodes; and an AC power supply that supplies current for generating the magnetic field to the coil. Has the above release? ! In a method for forming an amorphous thin film on a substrate supported outside the electric field space in parallel with the electric field, each of the pair of discharge electrodes is formed by arranging a plurality of columnar bodies each having a circular or elliptical cross section. I made it.

[Effect] By taking the above measures, the following effects are achieved.

In other words, each discharge electrode is formed by arranging one or more columnar bodies with circular or elliptical cross sections, so the surface area is several times larger than that of conventional parallel plate electrodes.
In addition, the capacitance between the opposing electrodes becomes significantly smaller, and the discharge impedance increases. As a result, the voltage effect is significantly reduced, voltage distribution is eliminated, electrodes several times as long as parallel plate electrodes can be used, and amorphous thin films with large areas can be manufactured.

Embodiment (1) FIG. 1 is a sectional view showing the structure of a first embodiment of the present invention. Note that the same parts as in FIG. 12 are given the same numbers. 1 is a reaction vessel in which mesh electrodes 12 and 13 for generating glow discharge plasma are arranged in parallel. The electrodes 12 and 13 are formed by stacking parallel mesh electrodes in which cylinders are arranged in two stages as shown in FIG. 3, as shown in FIG. In this case, the cylindrical members are arranged so as not to overlap each other when viewed from one side. Reference numeral 14 denotes a high frequency power source, which is connected to supply a power source with a frequency of, for example, 13.56 M7 to the mesh electrodes 12 and 13. The coil 5 is wound so as to surround the reaction vessel 1, and is supplied with AC power from an AC power source 6.

Reference numeral 7 denotes a reaction gas introduction pipe, which communicates with a cylinder (not shown) and supplies a mixed gas of monosilane and argon to the reaction vessel 1. The exhaust hole 8 communicates with a vacuum pump 9 to exhaust the gas inside the reaction vessel 1.

When manufacturing a thin film, the substrate 10 is supported by appropriate means in a position parallel to the planes of the mesh electrodes 12, 13, as shown in FIG. After the vacuum pump 9 is driven to evacuate the inside of the reaction vessel 1, a mixed gas of monosilane and argon is supplied from the reaction gas introduction pipe 7. The reaction vessel 1 is filled with the above mixed gas and its pressure is set to 0.05 to 0.
．． Maintain the temperature at 5 Torr, and connect the electrode 12°1 from the high frequency power source 14.
When a voltage is applied to the mesh electrodes 12 and 13, glow discharge plasma is generated between the mesh electrodes 12 and 13. On the other hand, an AC voltage of, for example, 100 Hz is applied to the coil 5 to generate a magnetic field B in a direction parallel to the electric field E generated between the electrodes 12 and 13.

The magnetic flux density in this magnetic field may be about 10 Gauss.

Among the gases supplied from the reaction gas introduction pipe 7, monosilane gas is decomposed into radical Si by the glow discharge plasma generated between the mesh electrodes 12 and 13, and the monosilane gas is decomposed into radical Si.
It adheres to the surface of and forms a thin film. At this time, charged particles such as argon ions are generated between the mesh electrodes 12 and 13 by a Coulomb force F, -qE due to the electric field E and a low force F.
2 q(V - B) causes a so-called EXB drift movement. Note that ■ is the speed of charged particles.

The charged particles thus move in a direction parallel to the mesh electrodes 12, 13 by the EXBX lid, and serve to stir the reaction gas. Outside the discharge space, where the influence of the electric field generated between the mesh electrodes 12 and 13 is small, the Larmo
It flies in an r orbit. Therefore, charged particles such as argon ions rarely hit the substrate 10 directly.

On the other hand, the electrically neutral radicals Si are not affected by the magnetic field B, deviate from the trajectory of the charged particle group, reach the substrate 10, and form an amorphous film on its surface. At this time, the radical Si collides with the charged particles traveling in the Larmor orbit, so that an amorphous thin film is formed not only in front of the electrodes 12 and 13 but also spread to the left or right. Moreover, since the magnetic field B is varied, it is possible to uniformly form an amorphous thin film on the surface of the substrate 10.

As described above, according to this embodiment, a high frequency power source (for example, IM)1z to 50 MHz is used as the plasma generation power source, and parallel mesh-like electrodes in which cylinders are arranged as shown in FIG. 2 are used as the electrodes, as shown in FIG. 3. It is used over and over again. Therefore, the surface area becomes about 3.14 times larger than that of parallel plate electrodes, the capacitance becomes significantly smaller, and the discharge impedance Z shown in FIG. 13 becomes larger. As a result, the voltage drop is significantly reduced, voltage distribution is eliminated, and electrodes approximately three times as long as parallel plate electrodes can be used.
It becomes possible to manufacture large-area amorphous thin films.

(2) FIG. 5 is a sectional view showing the configuration of a second embodiment of the present invention. Note that the same parts as in the first embodiment shown in FIG. 1 are denoted by the same reference numerals, and explanations thereof will be omitted.

The difference between this embodiment and the first embodiment is that, as shown in detail in FIG. 10
These points are arranged at right angles to the Thus, in this embodiment, two stages of electrodes 22.2 are used compared to parallel plate electrodes.
3, when viewed from the side, the surface area becomes approximately 3614 times larger, the capacitance becomes significantly smaller, and the discharge impedance Z shown in FIG. 13 increases. Therefore, as in the first embodiment, the voltage drop is significantly smaller than that of conventional parallel plate electrodes, there is no voltage distribution, and electrodes approximately three times as long as parallel plate electrodes can be used, resulting in a large surface area. Amorphous and thin films can be manufactured.

(3) FIG. 7 is a sectional view showing the configuration of a third embodiment of the present invention. The difference between this embodiment and the first embodiment is that the electrodes have a structure of low electrical resistance and small capacitance between opposing electrodes, that is, electrodes having the structures shown in FIGS. 8 and 9 are used on the substrate 10. This is a point placed parallel to the 8th
As shown in the figure, the electrode 32 is connected at one end to a power supply plate 30a and supported by insulating supports 31a and 31b, and the electrode 33 is connected at one end to a power supply plate 30b and at the other end. is supported by insulating support stands 31a and 31b. Note that FIG. 9 is a sectional view of FIG. 8. Note that the electrodes 32 and 33 are both rod-shaped bodies with circular cross sections.

In this embodiment, since the electric resistance in the length direction of the electrodes 32, 33 is significantly smaller than the discharge impedance, even if the substrate 10 is long, it can be uniformly distributed on its surface compared to conventional means. It becomes possible to form an amorphous thin film.

(4) FIG. 10 is a sectional view showing a fourth embodiment of the present invention. This embodiment differs from the first embodiment in that electrodes 42 and 43 having low electric resistance and low capacitance between opposing electrodes are used instead of the conventional parallel plate electrodes. As shown in Fig. 11, the electrodes 42 and 43 are composed of a plurality of rod-shaped electrodes with a circular or elliptical cross section.Compared with a parallel plate electrode, the surface area of an electrode with a substrate-shaped cross section is larger than that of a parallel plate electrode when the capacitance is the same. is about 3.14 times wider, so the electrical resistance of the high-frequency power is about 3 times less, and the potential distribution appearing in the electrode is significantly reduced. Therefore, this embodiment can also achieve the same effects as those of the first embodiment.

Note that the present invention is not limited to the above-mentioned embodiments,
Of course, various modifications can be made without departing from the spirit of the invention.

[Effects of the Invention] According to the present invention, each of the discharge electrodes is formed by arranging a plurality of columnar bodies with a circular or elliptical cross section, so the surface area is several times larger than that of a conventional parallel plate electrode. The capacitance between the opposing electrodes becomes significantly smaller, and the ni impedance increases due to the crawling. As a result, the voltage drop is significantly reduced, voltage distribution is eliminated, electrodes several times as long as parallel plate electrodes can be used, and a plasma CVD apparatus capable of producing a large-area amorphous thin film can be provided. .

[Brief explanation of the drawing]

1 to 4 are diagrams showing a first embodiment according to the present invention,
FIG. 1 is a sectional view of the device, FIG. 2 is a plan view of the electrode, FIG. 3 is a sectional view taken along the line ■--■ in FIG. 2, and FIG. 4 is an enlarged view of the electrode portion in FIG. 1. FIG. 5 is a sectional view of a device showing a second embodiment of the present invention, and FIG. 6 is an enlarged view of the electrode portion of the same embodiment. FIG. 7 is a sectional view of a device showing a third embodiment of the present invention, FIG. 8 is a perspective view of an electrode of the same embodiment, and FIG. 9 is an enlarged view of an electrode portion of the same embodiment. FIG. 10 is a sectional view of a device showing a fourth embodiment of the present invention, and FIG. 11 is an enlarged view of the electrode portion of the same embodiment. FIG. 12 is a sectional view of a conventional device, and FIG. 13 is a diagram for explaining the drawbacks of the conventional device. DESCRIPTION OF SYMBOLS 1... Reaction container, 2.3... Electrode, 4... Low frequency power supply, 5... Coil, 6... AC m[, 7... Reaction gas introduction tube, 8... Exhaust hole, 9...vacuum pump,
10... Substrate, 12°13.22.23,32,33
．． 42.43...Electrode for discharge, 14...High frequency power supply. Applicant's agent Patent attorney Takehiko Suzue Figure 1 ooooooooo~12 (13) ooooooooooo. 3rd cause 4th ward Figure 5 1゜ Figure 6 ■ ~ 9 Figure 7 Figure 8 O ■ 9! l Figure 10■B Figure 11

Claims (1)

[Claims] A reaction vessel, a means for introducing a reaction gas into the reaction vessel under reduced pressure, a pair of discharge electrodes housed opposite each other in the reaction vessel, and supplying a glow discharge voltage to the discharge electrodes. A power supply, a coil that surrounds the discharge electrode and generates a magnetic field in a direction perpendicular to the electric field generated between the discharge electrodes, and an AC power supply that supplies a current for generating the magnetic field to the coil, For forming an amorphous thin film on a substrate supported outside the discharge electric field space in parallel with the electric field, each of the pair of discharge electrodes is formed by arranging a plurality of columnar bodies each having a circular or elliptical cross section. A plasma CVD apparatus characterized by: