JP2002327276A - Method and device for uniformizing high frequency plasma over large area in plasma cvd apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a device for uniformizing generation of high frequency plasma over a large area in a plasma CVD apparatus using very high frequency(VHF). SOLUTION: This device comprises the first and second power feeding parts in both endpoints of a discharge electrode of the plasma CVD apparatus. The method is characterized by repeating alternately the cycle of feeding the same frequency of high frequency power to the first and the second feeding parts, and the cycle of feeding the different frequency of high frequency power to each of the parts, to uniformize the plasma generating condition per average time over a large area, due to differently generating plasma in each cycle.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the production of amorphous silicon, microcrystalline silicon, polycrystalline thin film silicon, silicon nitride, and other semiconductors used in solar cells and thin film transistors, and the etching of semiconductor films, and the production of these films. Plasma chemical vapor deposition apparatus (Plasma Chem) used for fluorine radical cleaning (self-cleaning) of NF ₃ gas of amorphous silicon (a-Si) deposited in a chamber by plasma.
TECHNICAL FIELD The present invention relates to a method and an apparatus for uniformizing a large area of a high-frequency plasma in an electrical vapor deposition.

[0002]

2. Description of the Related Art The formation of semiconductors such as amorphous silicon (hereinafter referred to as a-Si), microcrystalline silicon, polycrystalline thin film silicon, and silicon nitride used for solar cells and thin film transistors, and etching of semiconductor films, The high frequency plasma generator in the plasma chemical vapor deposition apparatus used for self-cleaning the silicon deposited in the chamber by the NF ₃ gas by these film formation uses a parallel plate type electrode and a ladder type electrode. There are two types of things.

FIG. 6 shows an example of an apparatus using a parallel plate type electrode. A substrate heating and supporting means 6 is installed in a plasma chemical vapor deposition apparatus 1 and is electrically grounded.
The plate electrode 6 is placed at a position, for example, 20 mm away from the plate electrode 6.
Set 0. An external high-frequency power supply 61 is connected to the plate electrode 60 via an impedance matching unit 62 and a coaxial cable 63. Further, the plate electrode 60 is grounded so that unnecessary plasma is not generated on the side opposite to the surface facing the substrate heating and supporting means 6. Install the shield 5.

Then, a substrate 7 for forming an a-Si thin film is placed on the substrate heating and supporting means 6 set at, for example, 200 ° C., and a silane (SiH ₄ ) gas is introduced from the gas introduction pipe 64 at a flow rate of 50 sccm, for example. By adjusting the evacuation speed of a vacuum pump system (not shown) connected to the evacuation pipe 65, the pressure in the plasma
Adjust to 0 mTorr. When the impedance matching unit 62 is adjusted so that the high-frequency power is efficiently supplied to the plasma generating unit and the high-frequency power is supplied from the high-frequency power supply 61, plasma 66 is generated between the substrate 7 and the plate electrode 60. The SiH ₄ is decomposed in the plasma 66 to form an a-Si film on the surface of the substrate 7. Therefore, for example, by forming a film in this state for about 10 minutes, an a-Si film having a required thickness is formed.

FIG. 7 shows an example of the configuration of a device using the ladder-type electrode 70, and FIG. 8 is a diagram drawn from the direction A in FIG. 7 so that the structure of the ladder-type electrode 70 can be clearly understood. The ladder-type electrode is described in detail in, for example, Japanese Patent Application Laid-Open No. Hei 4-236781. As an electrode shape developed from the ladder-type electrode, two electrode groups in which a plurality of electrode rods are arranged in parallel are arranged in a straight line. A structure using a reticulated electrode is reported in JP-A-11-111622.

In the high-frequency plasma generator shown in FIG. 7, a substrate heating and supporting means 6 (not shown in FIG. 8) is installed in the plasma chemical vapor deposition apparatus 1 and is electrically grounded. 20m opposite to 6
A ladder-type electrode 70 is set at a position separated by m. An external high-frequency power supply 61 is connected to the ladder-type electrode 70 via an impedance matching unit 62 and a coaxial cable 63, and an earth shield is provided so that unnecessary plasma is not generated on the side opposite to the surface facing the substrate heating and supporting means 6. 5 are installed.

Then, a substrate 7 for forming an a-Si film is placed on the substrate heating and supporting means 6 set at, for example, 200 ° C., and silane (SiH ₄ ) gas is introduced at a flow rate of 50 sccm from a gas supply pipe. Then, the pressure in the plasma chemical vapor deposition apparatus 1 is adjusted to, for example, 100 mTorr by the exhaust speed of a vacuum pump system connected to a vacuum exhaust pipe (not shown). When high-frequency power is supplied to the ladder-type electrode 70 in this state, the plasma 7 is generated between the substrate 7 and the ladder-type electrode 70.
1 is generated, the high-frequency power is efficiently supplied to the plasma 71.
The impedance matching device 5 is adjusted so as to be supplied to the generating section. Then, in the plasma 71, silane (Si
H ₄ ) is decomposed, and an a-Si film is formed on the substrate 7. For example, by forming the film in this state for about 10 minutes, an a-Si film having a necessary thickness is formed. .

The configuration example of FIG. 7 is different from the configuration example of FIG. 6 in that, first, a ladder-type electrode is used in which electrodes having a circular cross section are assembled in a ladder shape without using a flat electrode. Therefore, the raw material silane (SiH ₄ ) gas flows freely between the electrode rods, and the raw material is supplied uniformly. (4 points), plasma can be generated uniformly.

[0009]

As described above, a high-frequency plasma generator in a plasma chemical vapor deposition apparatus has been constructed. At present, a thin-film semiconductor for a solar cell, a thin-film transistor for a flat panel display, and the like manufactured by using the above-mentioned technology. Requires large area (for example, about 1.5 × 1.2 m), low cost by high-speed film formation, and high quality such as low defect density and high crystallization rate. A- deposited in the chamber by
The self-cleaning by NF ₃ gas of Si is also required to have a large area and a high speed as in the case of film formation.

As a new plasma generation method that satisfies these requirements, a high-frequency power supply (30-80
0 MHz). The fact that high film forming speed and high quality can be achieved at the same time by the high frequency is described in, for example, the document Ma.
t. Res. Soc. Symp. Proc. Vol. 4
24, pp. 9, 1997. In particular, a-
Microcrystalline Si attracts attention as a new thin film replacing Si
It has recently been found that this high frequency is suitable for high-speed, high-quality film formation of thin films.

However, this high-frequency film formation has a drawback that it is difficult to form a uniform large-area film. This is because the high-frequency wavelength is on the order of the size of the electrode, so that a standing wave on the electrode mainly due to a reflected wave generated at the electrode end, etc., and a voltage distribution due to the presence of stray inductance and capacitance. This is because the plasma becomes non-uniform due to the influence, mutual interference between the plasma and the high frequency, and as a result, the film formation becomes non-uniform. As a result, the film thickness distribution in the film formation becomes thin and non-uniform at the central portion. The NF ₃ plasma used for self-cleaning is such that NF ₃ gas is a negative gas (the property that electrons are easily attached).
Therefore, the plasma itself is very unstable, and the distribution becomes non-uniform due to a difference in gas flow (plasma generation on the downstream side) and an electrode interval.

[0012] Of these, in the configuration example of FIG. 6 shown as a typical example in the case of using parallel plate electrodes, the electrode size exceeds 30 cm x 30 cm, or the frequency is 30M.
When the frequency exceeds Hz, the effect of the standing wave becomes remarkable, and it is difficult to achieve the minimum required film thickness uniformity of ± 10% on the semiconductor film.

On the other hand, FIGS. 7 and 8 show typical examples in the case of using a ladder-type electrode. In addition to the use of the ladder-type electrode, standing waves which are remarkably generated by one-point feeding are shown in FIG. It is characterized in that it is reduced by supplying power to four points. However, even in this case, if the electrode size exceeds 30 cm or the frequency exceeds 80 MHz, it becomes difficult to realize uniform film formation.

[0014] The above-mentioned problems have attracted attention in academic societies. Res. Soc. Sym
p. Proc. Vol. 377, pp. 27, 1995
It is proposed to connect a lossless reactance (coil) to the side opposite to the power supply side of the parallel plate as described in (1). This is because, by changing the reflection condition of the standing wave from the electrode end, a relatively flat distribution in the standing wave waveform, for example, the vicinity of the maximum of the sine wave, is generated on the electrode, This is to reduce the generated voltage distribution. However, this method does not eliminate the standing wave from the root but only causes a flat portion of the sine wave to be generated on the electrode, so that a uniform portion can be obtained only about 1/8 of the wavelength. It is impossible in principle to make the range uniform beyond that.

As techniques for generating uniform plasma over a large area, JP-A-2000-3878, JP-A-2000-58465, and JP-A-2000-323.
No. 297, Japanese Patent Application Laid-Open No. 2001-7028 and the like, but these are maximum 80 cm × 80 cm.
It corresponds only to a small number of electrodes, and cannot correspond to a large area of 1.5 m × 1.2 m as aimed by the present invention. Therefore, when plasma is generated using a high frequency in a plasma chemical vapor deposition apparatus, a conventional technique generates a large-area, uniform plasma for a very large substrate exceeding 1 m × 1 m, and performs uniform processing. Could not do.

As a similar technique of the present invention, there is a technique for supplying two different high-frequency waves to two discharge electrodes, respectively. Noisan, J .; Pellet
ier, ed. , "Microwave Excite
d Plasmas ", Technology, 4, s
econd impression, pp. 401, E
lsevier Science B. V. 1999.

However, the purpose of this technique is to use one high frequency for generating plasma and the other high frequency for controlling the surface bias voltage of the insulating substrate, and to detect the amount of active ions and the like flowing into the substrate and the incidence. The purpose of this is to control the energy, which is completely different from the purpose of generating uniform plasma over a large area for a very large substrate exceeding 1 m × 1 m as in the present invention and performing uniform processing.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems. In a plasma chemical vapor deposition apparatus utilizing high frequency (VHF), plasma chemical vapor deposition has a large area and a uniform plasma generation state. It is an object to provide a method and an apparatus for uniformizing a large area of high-frequency plasma in the apparatus.

[0019]

In order to solve the above-mentioned problems, according to the present invention, first and second power supply portions are provided at both ends of a discharge electrode, and the first and second power supply portions have the same frequency. The cycle of supplying high frequency power and the cycle of supplying high frequency power of different frequencies are alternately performed, and the plasma generation status in each cycle is different and the plasma generation status is uniform over a large area when viewed on a time average. It was made to become.

A first aspect of the present invention is a method, which is a method for uniformizing a large area of a high-frequency plasma in a plasma chemical vapor deposition apparatus in which a high frequency is supplied to a discharge electrode of the plasma chemical vapor deposition apparatus to generate plasma. A first cycle in which high-frequency power of the same frequency is supplied to the first and second power-supplying parts, and a high-frequency power of a different frequency is supplied to the first and second power-supplying parts. The second cycle is performed alternately, and the plasma generation state is made uniform over a large area when viewed on a time average with plasma in different generation states in each cycle.

According to a twelfth aspect of the invention, which is an apparatus for practicing this method, a high frequency power is supplied to the first and second power supply portions provided on the discharge electrode to generate plasma. A large-area uniformizing device for high-frequency plasma in a plasma-enhanced chemical vapor deposition apparatus, comprising: a first oscillator that oscillates a high frequency of a first frequency; a second oscillator that oscillates a high frequency of a second frequency; A high-frequency power source A for receiving a high frequency from the oscillator of the first embodiment and supplying a high-frequency power of a first frequency to a first power supply unit of the discharge electrode;
Frequency switching means for receiving a high frequency from the oscillator and switching and outputting in an appropriate cycle, and a high-frequency power supply B for receiving an output from the frequency switching means and supplying power to the second power supply unit of the discharge electrode, By switching the power supply frequency from the high-frequency power supply B to the second power supply unit by the frequency switching unit, the plasma generation status is made different depending on the frequency difference of each switching cycle. It is characterized by being uniform over a large area.

As described above, by alternately performing the cycle of supplying the high frequency of the same frequency and the cycle of supplying the high frequency of the different frequency, when the high frequency of the same frequency is supplied to the discharge electrode, both sides of the electrode are used. The incoming waves resonate in the center and the plasma density increases, while when power of different frequency is supplied, the waves coming from both sides of the electrode cancel each other out in the center and the plasma density decreases. Therefore, when this cycle is performed alternately, when viewed on a time average, the state of plasma generation, that is, the standing wave distribution on the discharge electrode becomes uniform over a large area, and the film thickness distribution uniformity on a large area substrate and self-cleaning The plasma distribution can be made uniform.

According to the method invention described in claim 2 and the invention described in claim 13 for carrying out the method invention, one frequency in the second cycle is temporally changed, and the plasma generation state is changed. Is intentionally changed, and when viewed on a time average, the state of plasma generation is made uniform over a large area, and the second oscillator comprises:
The oscillation frequency is variable.

As described above, when one frequency is varied with time in the second cycle in which high-frequency powers having different frequencies are supplied, the plasma generation state changes in accordance with the variation, so that the plasma density is further averaged. Can be

The one frequency in the cycle of the different frequency is, as described in claim 3, the one frequency in the second cycle is the same as the high frequency in the first cycle, and Preferably, the first and second cycles are performed at a frequency of 1 Hz to 10 MHz, as described in claim 4.

Further, the time ratio between the first cycle and the second cycle is as follows.
The time ratio between the first cycle and the second cycle is changed depending on the pressure of the gas to be used and the type of gas, and the time ratio between the first and second frequencies switched by the frequency switching means is used as the gas to be used. And means for changing the pressure and the type of gas.

As described above, by changing the time ratio between the first cycle and the second cycle depending on the gas pressure and the kind of gas to be used, for example, depending on the gas conditions, even if the duty ratio is the same, the plasma generation state May be different, but even in such a case, it is possible to cope with it without modifying any hardware, and it is possible to make the plasma density uniform.

According to the invention described in claim 6 and claim 15, the high frequency of one of the frequencies to be supplied to the first or second power supply unit in the first cycle is phase-modulated, and the other is subjected to phase modulation. The phase of the high-frequency power supplied to the power supply unit is shifted to change the state of plasma generation, and when viewed on a time average, the state of plasma generation is made uniform over a large area, and from the first oscillator A phase modulating means for modulating a phase of a high frequency supplied to either the high frequency power supply A or the frequency switching means is provided.

As described above, when a high-frequency power of the same frequency is supplied to the power supply unit, the phase of one of the high-frequency waves is shifted from the other, so that the plasma density at the center of the discharge electrode formed when the same frequency is supplied to the discharge electrode. Can be moved, and can be made uniform over time.

According to a seventh aspect of the present invention, a DC bias is applied to a power supply portion of the discharge electrode so that the density of generated plasma is made uniform over a large area. A means for applying a DC bias to the power supply unit.

By applying a DC bias to the power supply portion of the discharge electrode, the sheath capacitance of the discharge electrode can be reduced, and the standing wave wavelength can be increased to average the plasma density.

According to the invention described in claims 8 and 17, the power supply cable to the first and second power supply portions is made to coincide with the discharge electrode axial direction to minimize the current return distance and supply power. The power loss in the section is reduced, the plasma area is enlarged, and the axial direction of the power supply cable to the power supply section of the discharge electrode is attached so as to match the axial direction of the discharge electrode. I do.

As described above, by making the axial direction of the power supply cable to the power supply unit coincide with the axial direction of the discharge electrode, the power supply power smoothly enters the discharge electrode, the current return distance is minimized, and the power loss in the power supply unit is reduced. And the plasma region can be expanded.

According to a ninth aspect of the present invention, in the plasma chemical vapor deposition apparatus, plasma is uniformly formed within a range satisfying conditions such as a film forming speed by plasma chemical vapor deposition and a self-cleaning speed of the plasma chemical vapor deposition apparatus. It is characterized by containing a gas that tends to be easily formed.

By introducing a gas which tends to make the plasma uniform, the state of plasma generation is made more uniform, and this gas is made of N ₂ , A
An inert gas such as r, Kr, or Xe is preferable.

[0036]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, for example, an electrode size of 1.5 mx 1.2 m and a gas pressure of 12 to 20 Pa (90
Aiming at a plasma chemical vapor deposition apparatus with a high frequency power supply frequency of 60 MHz class, as described in Means for Solving the Problems, the first and second power supplies are applied to both ends of the discharge electrode in the plasma chemical vapor deposition apparatus, respectively. A cycle in which high-frequency power of the same frequency is supplied to the power supply section and a cycle in which high-frequency power of a different frequency is supplied to the power supply section are alternately performed. , That is, the distribution of standing waves on the discharge electrode was made uniform over a large area. Further, the present invention is characterized in that the following six things can be performed in order to make the plasma generation state uniform on a time average. 1. Oscillation frequencies of different frequencies are temporally varied. 2. First and second depending on gas conditions such as gas pressure and gas type
The ratio of the time for supplying the same frequency to the power supply unit and the time for supplying a different frequency, that is, the duty ratio is changed. 3. When the same frequency is supplied to the first and second power supply units, the phase of the high frequency power supplied to one of the power supply units is shifted from the phase of the high frequency power supplied to the other power supply unit. 4. A DC bias voltage is applied to a power supply section of the discharge electrode. 5. The axial direction at the outlet of the power supply cable is the same as the direction (axial direction) connecting the first and second power supply units. 6. N ₂ , Ar, K that easily generate uniform plasma within a range that satisfies conditions such as a film forming speed and a self-cleaning speed.
An inert gas such as r or Xe is injected at an appropriate ratio.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention to them unless otherwise specified. This is just an example.

First, an apparatus for uniformizing large-area high-frequency plasma in the plasma chemical vapor deposition apparatus of the present invention will be described, and then a method for uniformizing large-area high-frequency plasma will be described. FIG. 1 is a schematic block diagram of an embodiment of a large-area homogenizing apparatus for high-frequency plasma in a plasma chemical vapor deposition apparatus according to the present invention. FIG. 2 is a view for explaining a case where a discharge electrode is formed in a ladder type. FIG. 4 is a configuration diagram when the axial direction at the outlet of the power supply cable is the same as the direction (axial direction) connecting the first and second power supply units. FIG. FIG. 5 is an explanatory view of a plasma generation situation when high frequencies of different frequencies are supplied at ten different ratios from 0:10 to 9: 1. FIG. 5 shows the phase of one high frequency when the same frequency is supplied to the power supply unit. It is explanatory drawing at the time of deviating from the other phase.

In FIG. 1, reference numeral 1 denotes a plasma-enhanced chemical vapor deposition apparatus in which the inside is hermetically sealed, 2 denotes a discharge electrode, and 3 and 4 denote first and second power supply portions for supplying high frequency to the discharge electrode 2.
Is a ground shield provided so as not to generate unnecessary plasma. 6 is installed at a distance of, for example, about 20 to 34 mm from the discharge electrode 2. A mechanism (not shown) for holding and heating the substrate 7 and a heater for heating are provided. Is connected to a gas supply source (not shown) to introduce a reactive gas 9 such as a silane (SiH ₄ ) gas for film formation or an NF ₃ gas for self-cleaning. , A vacuum pump capable of evacuating the internal pressure of the plasma-enhanced chemical vapor deposition apparatus 1 to about 1 × 10 ⁻⁶ Torr; 12, 13 a first and a second high-frequency power source A; RF amplifier constituting B, for example, 60M
A first high-frequency (RF) oscillator having a phase shifter capable of oscillating and transmitting a high-frequency (RF) of 1 Hz to a high-frequency power supply (RF amplifier) A and a changeover switch 16 and phase-modulating either high-frequency. 15 is 5
A second high-frequency (RF) oscillator configured to oscillate a radio frequency (RF) of 8.5 MHz and to be able to vary this frequency from 58.5 MHz to 59.9 MHz, or from 60.1 MHz to 61.5 MHz, A switch 16 receives the high frequency from the first and second high-frequency oscillators 14 and 15 and switches the same to supply the high-frequency power to the high-frequency power supply B13. A reference numeral 17 denotes the first and second high-frequency oscillators 14 and 15 by the switch 16. When switching the high frequency from the function generator, a function generator that changes the time ratio of these high frequencies, that is, the duty ratio,
Reference numeral 8 denotes a current return path. Also, in FIG.
1 shows one electrode when the discharge electrode 2 in FIG. 1 is constituted by a ladder type electrode, 21 and 22 are power supply cables for supplying high frequency to the discharge electrode 2 (20), and 23 is D
This is a C bias power supply.

The first high-frequency oscillator 14 oscillates a high frequency of, for example, 60 MHz as described above and sends it to the high-frequency power source A12 and the changeover switch 16, and
The high frequency oscillator 15 oscillates a high frequency of, for example, 58.5 MHz and sends it to the changeover switch 16. The changeover switch 16 switches between a high frequency of 60 MHz transmitted from the first high-frequency oscillator 14 and a high frequency of 58.5 MHz transmitted from the second high-frequency oscillator 15 in a fixed cycle, and transmits the high-frequency power to the high-frequency power supply B13. Therefore, high frequency power supply A
Numeral 12 supplies a high frequency of 60 MHz to the first power supply unit 3, and the high frequency power supply B13 switches at a constant cycle.
The high frequency of 0 MHz and 58.5 MHz is supplied to the second power supply unit 4.

Then, 60 MHz transmitted from the first high-frequency oscillator 14 and 58.5 MH transmitted from the second high-frequency oscillator 15 by the changeover switch 16
The switching of the high frequency of z can change the time ratio, that is, the duty ratio, by a signal from the function generator 17 according to gas conditions such as gas pressure and gas type. The first high-frequency oscillator 14 has a phase shifter inside so that the high-frequency wave sent to either the high-frequency power source A12 or the changeover switch 16 can be out of phase with the high-frequency wave sent to the other. The high-frequency oscillator 15 has an oscillation frequency of, for example, 58.5 MHz to 59.9 MHz, or 6
It is configured to be variable from 0.1 MHz to 61.5 MHz.

On the other hand, the discharge electrode 2 of the plasma chemical vapor deposition apparatus 1
Is configured, for example, in a ladder type as shown in FIG. 2, and the first power supply unit 3 and the second power supply unit 4 each have, for example, 8 points indicated by black circles at both ends of the discharge electrode 2 as shown in the figure. It consists of. The power supply cable for supplying high frequency power to the power supply section 3 or 4 of the discharge electrode 2 has an axial direction of the outlet as shown at 21 and 22 in FIG. The ladder-type electrode 20 is connected so as to coincide with the direction (axial direction) connecting the first and second power supply portions 3 and 4, and a DC bias is applied to the discharge electrode 2 (20) from a DC bias power supply 23. I have. In the above description, the discharge electrode 2 is of a ladder type, and
Although the description has been made on the point-by-point basis, the present invention is applicable not only to the ladder-type electrode but also to the flat-plate type electrode.
The number of points can be set as required, such as 6 points.

As described above, when the outlet axes of the power supply cables 21 and 22 for supplying high frequency power to the power supply section 3 or 4 of the discharge electrode 2 are connected so as to coincide with the axial direction of the discharge ladder electrode 20, the power supply is performed. Ladder type electrode 2 with smooth power
As the value approaches 0, the current return distance is minimized, the power loss in the power supply unit is reduced, and the plasma region can be expanded. The power supply cables 21 and 22 may have any shape such as a coaxial cable, a parallel plate, and a parallel wire.

When a DC bias is applied to the discharge electrode 2 from the DC bias power supply 23, the sheath capacitance of the discharge electrode 2 can be reduced, and the standing wave wavelength increases in the direction of uniform voltage distribution. In addition, the plasma density can be averaged. The sheath capacitance means that a collection of electrons called a sheath is formed around the ladder electrode 20 in the process of generating plasma,
This collection of electrons creates a state where a kind of insulation is maintained and no DC current flows, as if a capacitor were around the electrodes, and a negative DC bias was applied. And the electrons are diffused, and this sheath capacitance can be reduced. Therefore, the wavelength interval of the standing wave is increased, and the plasma can be made uniform.

Using the thus-configured plasma chemical vapor deposition apparatus 1 of the present invention, semiconductor films such as a-Si, microcrystalline silicon, polycrystalline thin film silicon, and silicon nitride are formed, and these films are formed in a chamber. N of deposited a-Si
When performing self-cleaning with F ₃ gas, for example, in film formation, the substrate 7 is attached to the heating support means 6 set to 200 ° C., and silane (Si
The reaction gas 9 such as H ₄ ) gas is supplied at a flow rate of 50 scc, for example.
The pressure in the plasma-enhanced chemical vapor deposition apparatus 1 is adjusted to, for example, 100 mTorr by adjusting the evacuation speed of the vacuum pump 11 connected to the evacuation pipe 10.

Then, a high frequency of, for example, 60 MHz is sent from the first high frequency oscillator 14 and a high frequency of, for example, 58.5 MHz is sent from the second high frequency oscillator 15 to the high frequency power supply A12 and the changeover switch 16, respectively. The changeover switch 16 controls the first high-frequency oscillator 14
60MHz and second high-frequency oscillator 15 sent from
The high-frequency power of 58.5 MHz transmitted from the power supply is switched at a constant cycle and transmitted to the high-frequency power source B13. Then, the high-frequency power supply A12 supplies a high-frequency power of 60 MHz to the first power supply unit 3, and the high-frequency power supply B13 supplies a high-frequency power of 60 MHz and 58.5 MHz that is switched in a constant cycle to the second power supply unit 4.

Then, plasma is generated between the discharge electrode 2 and the substrate 7 and silane (Si) introduced from the gas introduction pipe 8 is introduced.
The reaction gas 9 such as H ₄ ) gas is decomposed and a-
Si is formed. Note that self-cleaning of the plasma chemical vapor deposition apparatus 1 according to NF ₃ gas above are also quite similar, NF ₃ gas is fluorine radicals decomposed by the plasma, the cleaning is performed.

The plasma generated at this time is the first plasma.
When the same high frequency of 60 MHz is supplied to the second power supply units 3 and 4, a high frequency of 60 MHz is supplied to the first power supply unit 3 and a high frequency of 58.5 MHz is supplied to the second power supply unit 4. When power is supplied, the state of occurrence differs as shown in FIG. That is, the graph shown in FIG. 4 shows that the reaction gas 9 such as silane (SiH ₄ ) gas is introduced into the plasma chemical vapor deposition apparatus 1 as described above, and the first and second power supply sections 3 and 4 of the discharge electrode 2 are formed. At the same frequency (60 MHz
z) The time during which the high-frequency power was supplied and the high-frequency power of a different frequency were supplied (60 MHz to the first power supply unit 3, the second power supply unit 4).
In this example, the plasma generation status was examined for 10 types of time ratios in which power was supplied to 58.5 MHz from 0:10 to 9: 1.

In FIG. 4, the horizontal axis represents the first power supply unit 3.
(0 cm), and the right end (110 cm) corresponds to the second power supply unit 4. The vertical axis indicates the relative voltage value of the plasma, and the higher the value, the higher the plasma density. A in the figure
The line of (b) shows the plasma generation situation when the time when the supplied frequency is different is 10 and the time when the same frequency is supplied is 0, that is, only when the supplied frequency is different. Is the case where the same frequency is 1, and similarly, the line of n is the case where the same frequency is 9 for the different frequency 1.

As can be seen from this graph, the first and second
In the case of “a” in which different power is supplied to the power supply units 3 and 4, the plasma density is highest at both ends of the discharge electrode 2, that is, near the power supply units 3 and 4, and the plasma density is lowest at the center. On the other hand, when n is the highest when the same frequency is supplied to the first and second power supply units 3 and 4, the plasma density is the highest at the center of the discharge electrode 2, and the power supply units 3 and 4 at both ends from the center. , And slightly higher near the power supply units 3 and 4. Then, when the time for supplying the first and second power supply units 3 and 4 with different frequencies and the time for supplying the same frequency with 5: 5 are the same, f
And n are added together, and the plasma density is slightly higher at both ends of the discharge electrode 2, but is uniform over a wide area at the center.

That is, the graph of FIG.
In the high frequency, the power supply portions 3 at both ends of the discharge electrode 2,
4 shows that when a high frequency of the same frequency is supplied, the plasma density increases in the central portion, and when a high frequency of a different frequency is supplied, the density of the central portion decreases, and this is alternately performed in an appropriate cycle. By doing so, the plasma generation state can be made uniform over a large area. In addition, this power supply unit 3,
In the cycle 4 in which the same frequency and a high frequency of a different frequency were alternately supplied to 4, the same effect was obtained from 1 Hz to 10 MHz.

In the present invention, the oscillation frequency of the second high-frequency oscillator 15 is further increased to, for example, 58.5 MHz.
To 59.9MHz, or 60.1MHz to 6
It is fluctuated with time like 1.5 MHz. Then, the plasma generation state can be intentionally changed by the change in the frequency, and the plasma density can be further averaged over time.

The phase of the high-frequency wave sent to either the high-frequency power supply A12 or the changeover switch 16 is shifted by a phase shifter included in the first high-frequency oscillator 14 with respect to the high-frequency wave sent to the other. Then, as shown by a solid line 50 in FIG. 5, for example, in a power supply state in which the plasma density is high at the center of the discharge electrode 2 when the phase is not shifted, the phase is shifted so that the position where the plasma density is high is shifted. It can be shifted left and right as indicated by the broken line 51 or 52 or the dashed line. Therefore, the plasma density can be made uniform over a wider range when viewed on a time average.

When the gas conditions such as the gas pressure and the gas type change, a signal is sent from the function generator 17 to the changeover switch 16 and the changeover switch 1 is turned on.
FIG. 4 shows a transmission time ratio, that is, a duty ratio (Duty ratio) of each of the high frequency from the first high frequency oscillator 14 and the high frequency from the second high frequency oscillator 15 sent to the high frequency power supply B13. Change as shown. By doing so, the ratio (duty ratio) of the time during which high-frequency power of the same frequency is supplied to the first and second power supply units 3 and 4 of the discharge electrode 2 and the time during which high-frequency power of different frequencies is supplied. Is changed so that the state of plasma generation can be changed in various ways as shown in FIG.

This is to cope with the fact that the plasma generation state differs even at the same duty ratio depending on the gas conditions such as gas pressure and gas type. The power supplied from 3, 4 is discharged before reaching the center of the discharge electrode 2,
Discharge at the center is reduced. Therefore, as shown in the graph a in FIG. 4, the plasma generation density is low at the central portion of the discharge electrode 2. In this case, the time for supplying the high frequency power of the same frequency is lengthened, and conversely, the plasma density at the central portion is reduced. When it becomes higher, the time for supplying the high frequency of the same frequency is shortened. As a result, even if the gas conditions such as the gas pressure and the gas type change, the plasma density at the central portion can be controlled and can be made more uniform.

When performing film formation or self-cleaning by the method described above, N ₂ , Ar, Kr, and N ₂ , which are likely to generate uniform plasma, within a range satisfying conditions such as a film formation speed and a self-cleaning speed. If a gas such as Xe is injected at an appropriate ratio (about 0.1 to 25%), more uniform film formation and self-cleaning can be realized.

As described above, in the present invention, a cycle for supplying high-frequency power of the same frequency to power supply units provided at both ends of the discharge electrode in a plasma chemical vapor deposition apparatus and a cycle for supplying high-frequency power of different frequencies are alternately performed. As a result, when viewed on a time average, the plasma generation state can be made uniform over a large area. Oscillation frequencies of different frequencies are temporally varied. 2. First and second depending on gas conditions such as gas pressure and gas type
The ratio of the time for supplying the same frequency to the power supply unit and the time for supplying a different frequency, that is, the duty ratio is changed. 3. When the same frequency is supplied to the first and second power supply units, the phase of the high frequency power supplied to one of the power supply units is shifted from the phase of the high frequency power supplied to the other power supply unit. 4. A DC bias voltage is applied to the power supply section of the discharge electrode. 5. The axial direction at the outlet of the power supply cable is the same as the direction (axial direction) connecting the first and second power supply units. 6. N ₂ , Ar, K that easily generate uniform plasma within a range that satisfies conditions such as a film forming speed and a self-cleaning speed.
An inert gas such as r or Xe is injected at an appropriate ratio. By performing such things as, for example, the electrode size 1.5m
× 1.2m, gas pressure 12-20Pa (90-150mT
orr), which enables film formation and self-cleaning by a plasma chemical vapor deposition apparatus having a high frequency power supply frequency of 60 MHz class.

[0058]

As described above, according to the plasma chemical vapor deposition apparatus according to the present invention, even when the gas conditions such as the pressure condition and the flow rate condition change, the change of the high frequency power supply frequency and the change of the duty ratio can be performed without touching the hardware. , Phase modulation,
Uniform plasma can always be obtained by only soft adjustment such as application of a DC bias, and high-speed uniform film formation and uniform self-cleaning can be performed. As a result, it is possible to obtain large results such as an improvement in the yield of a film-formed product in large-area film formation and a reduction in cost. To bring.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram of an embodiment of a large-area uniformizing device for high-frequency plasma in a plasma chemical vapor deposition apparatus according to the present invention.

FIG. 2 is a diagram for explaining a case where a discharge electrode is configured in a ladder type.

FIG. 3 is a diagram illustrating a connection configuration between a discharge electrode and a power supply cable according to the present invention.

FIG. 4 shows that a high frequency of the same frequency and a high frequency of a different frequency are applied to the power supply portion of the discharge electrode from 0:10 to 9: 1.
FIG. 4 is an explanatory diagram of a plasma generation situation when power is supplied at ten different ratios up to 10;

FIG. 5 is an explanatory diagram when a phase of one high frequency is shifted from another phase when the same frequency is supplied to the power supply unit.

FIG. 6 is a configuration example of a conventional plasma chemical vapor deposition apparatus using a parallel plate type electrode.

FIG. 7 is a configuration example of a conventional plasma chemical vapor deposition apparatus using a ladder-type electrode.

FIG. 8 is a view for explaining the structure of a conventional ladder-type electrode.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Plasma chemical vapor deposition apparatus 2 Discharge electrode 3 1st electric supply part 4 2nd electric supply part 5 Earth shield 6 Heating support means 7 Substrate 8 Gas introduction pipe 9 Reaction gas 9 10 Exhaust pipe 11 Vacuum pump 12 High frequency power supply A 13 High frequency power supply B 14 First high-frequency oscillator 15 Second high-frequency oscillator 16 Changeover switch 17 Function generator 18 Current return path

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroshi Majima 5-717-1 Fukahori-cho, Nagasaki-shi Inside Nagasaki Research Laboratory, Mitsubishi Heavy Industries, Ltd. (72) Inventor Pan Takatsuka 1-1-1, Akunoura-cho, Nagasaki-shi Nagasaki Shipyard Co., Ltd. (72) Inventor Yasuhiro Yamauchi 1-1, Akunouramachi, Nagasaki City Mitsubishi Heavy Industries, Ltd. In-house (72) Inventor Eshiro Sasakawa 1-1-1, Akunouracho, Nagasaki-shi F-term (reference) in Nagasaki Shipyard, Mitsubishi Heavy Industries, Ltd. EH02 EH13 EH20 5F051 AA05 BA12 CA16 CA21 CA23

Claims (19)

[Claims] 1. A large-area uniformizing method for high-frequency plasma in a plasma-enhanced chemical vapor deposition apparatus in which high-frequency power is supplied to a discharge electrode of the plasma-enhanced chemical vapor deposition apparatus to generate plasma. And a second power supply unit, and the first and second power supply units are supplied with a high-frequency power of the same frequency.
Cycle and the second to supply high frequency of different frequency
High frequency plasma in a plasma chemical vapor deposition apparatus characterized in that the plasma generation status is made uniform over a large area when viewed on a time-averaged basis by the plasma of different generation status in each cycle by alternately performing the above cycle. Large area uniform method. 2. When one frequency in the second cycle is changed over time to intentionally change the plasma generation state and time-averaged, the plasma generation state is uniform over a large area. 2. The method according to claim 1, wherein
4. A method for uniformizing a large area of high-frequency plasma in a plasma chemical vapor deposition apparatus described in 1). 3. The high frequency plasma in the plasma chemical vapor deposition apparatus according to claim 1, wherein one frequency in the second cycle is the same as a high frequency in the first cycle. Large area uniform method. 4. The method according to claim 1, wherein the first and second cycles are performed in a cycle of 1 Hz to 10 MHz. 5. The plasma-enhanced chemical vapor deposition apparatus according to claim 1, wherein a time ratio between the first cycle and the second cycle is changed depending on a pressure of a gas used and a kind of the gas. Large area uniformization method for high frequency plasma. 6. A phase modulation of a high frequency of one of the frequencies supplied to the first and second power supply units in the first cycle, and a phase of the high frequency supplied to the other power supply unit is shifted from the phase of the high frequency power. 3. A large-area high-frequency plasma in a plasma chemical vapor deposition apparatus according to claim 1, wherein the state of generation of the plasma is made uniform over a large area when the state of generation is changed and viewed on a time average. Uniformization method. 7. A high-frequency plasma chemical vapor deposition apparatus according to claim 1, wherein a direct current bias is applied to a power supply portion of the discharge electrode to make the generated plasma density uniform over a large area. A large area uniformizing method for plasma. 8. An axial direction of a power supply cable to the first and second power supply units is made to coincide with an axial direction of a discharge electrode, a current return distance is minimized, a power loss in the power supply unit is reduced, and a plasma region is expanded. 3. The method according to claim 1, wherein the plasma chemical vapor deposition apparatus has a large-area uniform high-frequency plasma. 9. A method in which a gas which tends to make plasma uniform within a range satisfying conditions such as a film forming speed by plasma enhanced chemical vapor deposition and a self-cleaning speed of the plasma enhanced chemical vapor deposition device is introduced into the plasma enhanced chemical vapor deposition apparatus. 3. A method for uniformizing a large area of high-frequency plasma in the plasma chemical vapor deposition apparatus according to claim 1 or 2. 10. The gas comprises N ₂ , Ar, Kr, Xe.
The method of claim 9, wherein the gas is an inert gas such as an inert gas. 11. A large-area uniformity of high-frequency plasma in a plasma-enhanced chemical vapor deposition apparatus, characterized by combining two or more methods for uniformizing large-area high-frequency plasma in the plasma-enhanced chemical vapor deposition apparatus according to claim 4. Method. 12. A large-area homogenizing apparatus for high-frequency plasma in a plasma chemical vapor deposition apparatus for generating high-frequency plasma by supplying high-frequency power to first and second power supply units provided on a discharge electrode, comprising: A first oscillator that oscillates a high frequency;
A second oscillator for oscillating a high frequency having a frequency of
High-frequency power supply A that receives a high frequency from the oscillator of the first embodiment and supplies a high frequency of the first frequency to the first power supply unit of the discharge electrode.
Frequency switching means for receiving high frequencies from the first and second oscillators and switching and outputting the signals in appropriate cycles; and receiving power from the frequency switching means and supplying power to a second power supply portion of the discharge electrode. By switching the power supply frequency from the high-frequency power supply B to the second power supply unit by the frequency switching means, the plasma generation state is made different depending on the frequency difference of each switching cycle, and the time average is obtained. A large-area homogenizing apparatus for high-frequency plasma in a plasma chemical vapor deposition apparatus, characterized in that, when viewed, a plasma generation state is made uniform over a large area. 13. The large-area uniformizing apparatus for high-frequency plasma in a plasma chemical vapor deposition apparatus according to claim 12, wherein the second oscillator has a variable oscillation frequency. 14. The apparatus according to claim 12, further comprising means for changing a time ratio between the first and second frequencies to be switched by said frequency switching means depending on a pressure and a kind of gas to be used. Large-area homogenizer for high-frequency plasma in a plasma-enhanced chemical vapor deposition system. 15. A phase modulating means for modulating a phase of a high frequency power supplied from the first oscillator to either the high frequency power supply A or the frequency switching means. Large-area homogenizing apparatus for high-frequency plasma in the plasma chemical vapor deposition apparatus described in 1 above. 16. A device according to claim 12, further comprising means for applying a DC bias to a power supply section of said discharge electrode.
Or a large-area uniformizing device for high-frequency plasma in the plasma-enhanced chemical vapor deposition apparatus described in 13. 17. The plasma-enhanced chemical vapor deposition apparatus according to claim 12, wherein an axial direction of a power supply cable to a power supply section of the discharge electrode is attached so as to coincide with an axial direction of the discharge electrode. Large area homogenizer for high frequency plasma. 18. The method according to claim 11, wherein the first and second power supply portions are provided at both ends of a discharge electrode.
2. A large-area homogenizing apparatus for high-frequency plasma in the plasma chemical vapor deposition apparatus described in 2. 19. A large-area uniformity of high-frequency plasma in a plasma-enhanced chemical vapor deposition apparatus comprising a combination of two or more high-frequency plasma uniform-area apparatuses in the plasma-enhanced chemical vapor deposition apparatus according to claim 14. Device.