JP3377773B2 - Power supply method to discharge electrode, high-frequency plasma generation method, and semiconductor manufacturing method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to film formation of semiconductors such as amorphous silicon, microcrystalline silicon, polycrystalline thin film silicon and silicon nitride used for solar cells and thin film transistors, and high frequency plasma used for etching semiconductor films. The present invention relates to a method for supplying power to a discharge electrode of a generator, a plasma generation method and a semiconductor manufacturing method using the same. It can also be used for various surface treatments using discharge.

[0002]

2. Description of the Related Art As an example of the structure of the above high-frequency plasma generator and the method of manufacturing a semiconductor using the same, an amorphous silicon semiconductor thin film (hereinafter referred to as a-Si) is used in a plasma chemical vapor deposition device (hereinafter referred to as PCVD device). Regarding the case of manufacturing, when using parallel plate type electrodes,
A typical example of two cases using a ladder electrode will be described.

FIG. 8 shows an example of the construction of an apparatus using parallel plate type electrodes, which are generally used for a-Si film formation. The substrate heater 2 is installed in the reaction container 1 and electrically grounded. The plate electrode 3 is installed at a position facing the substrate heater 2 at a distance of, for example, 20 mm from the substrate heater 2.
An external high frequency power supply 4 is connected to the plate electrode 3 via an impedance matching device 5 and a coaxial cable 6. An earth shield 8 is installed on the plate electrode 3 on the side opposite to the surface facing the substrate heater 2 so that unnecessary plasma is not generated.

The a-Si film is formed by the following procedure. First,
For example, on the substrate heater 2 set to 200 ° C., a-Si
A substrate 16 for forming a thin film is installed. SiH ₄ gas is introduced at a flow rate of 50 sccm from the gas supply pipe 17,
The pressure in the reaction vessel 1 is adjusted to, for example, 100 mTorr by adjusting the exhaust speed of a vacuum pump system (not shown) connected to the vacuum exhaust pipe 18. High-frequency power is supplied to generate plasma between the substrate 16 and the plate electrode 3. The impedance matching device 5 is adjusted so that the high frequency power is efficiently supplied to the plasma generating unit. SiH ₄ is decomposed in the plasma 19 to form an aS model on the surface of the substrate 16. For example, by performing film formation in this state for about 10 minutes, an a-Si film having a required thickness is formed.

FIG. 9 shows a structural example of an apparatus using the ladder electrode 303 shown in FIG. Details of the ladder electrode are reported in, for example, Japanese Patent Application Laid-Open No. 4-236781. FIG. 10 is a view drawn from the direction A in FIG. 9 so that the structure of the ladder electrode 303 can be seen clearly. Further, as an electrode shape obtained by developing a ladder electrode, a mesh electrode in which two electrode groups in which a plurality of electrode rods are arranged in parallel, such as a ladder electrode, are arranged orthogonally is, for example, JP-A-11-111622.
This is also considered to be a kind of ladder electrode, and can be used similarly.

A substrate heater 2 (not shown in FIG. 10) is installed in the reaction vessel 1 and electrically grounded. At a position facing the substrate heater 2, from the substrate heater 2 to, for example, 2
The ladder electrode 303 is installed at a distance of 0 mm. An external high frequency power source 4 is connected to the ladder electrode 303 via an impedance matching device 5 and a coaxial cable 6. An earth shield 308 is installed on the ladder electrode 303 on the side opposite to the surface facing the substrate heater 2 so that unnecessary plasma is not generated.

The a-Si film is formed by the following procedure. First,
For example, on the substrate heater 2 set to 200 ° C., a-Si
A substrate 16 for forming a film is installed. SiH ₄ gas is introduced from the gas supply pipe 17 at a flow rate of, for example, 50 sccm, and the evacuation speed of a vacuum pump system (not shown) connected to the evacuation pipe 18 is adjusted to adjust the pressure in the reaction vessel 1 to 1
Adjust to 00 mTorr. High-frequency power is supplied to generate plasma between the substrate 16 and the ladder electrode 303.
The impedance matching device 5 is adjusted so that the high frequency power is efficiently supplied to the plasma 319 generation unit. SiH ₄ is decomposed in the plasma 319, and an a-Si film is formed on the substrate 16. For example, by performing film formation in this state for about 10 minutes, an a-Si film having a necessary thickness is formed.

This configuration example has the following two features as compared with the configuration example of FIG. The first feature is that instead of using a flat plate electrode as an electrode, an electrode called a ladder type in which electrode members having a circular cross section are assembled into a ladder type is used. This electrode has a feature that the raw material SiH ₄ gas freely flows between the electrode rods, so that the raw material can be uniformly supplied. The second feature is that the power is not supplied to one place of the electrode, but to a plurality of (here, four) places.

[0009]

Currently, thin-film semiconductors for solar cells, thin-film transistors for flat panel displays, etc., which are manufactured by using the above-mentioned technique, are manufactured at a high speed to reduce costs, and have a low defect density and high crystallization. Higher quality such as rate is required. As a new plasma generation method that meets these requirements, high frequency power supply (30
~ 800 MHz). The fact that both high film formation speed and high quality can be achieved by increasing the frequency is described in, for example, Document Mat.
Res. Soc. Symp. Proc. Vol. 424, pp. 9, 1997. In particular, it has recently been found that this high frequency is suitable for high-speed and high-quality film formation of a microcrystalline Si thin film, which is attracting attention as a new thin film replacing a-Si.

However, the high-frequency film formation has a drawback that uniform large-area film formation is difficult. This is because the high-high frequency wavelength is of the same order as the electrode size, so the standing wave on the electrode mainly caused by the reflected wave generated at the electrode end, etc., the influence on the voltage distribution due to the presence of stray inductance, This is because the plasma becomes non-uniform due to mutual interference between the plasma and the high frequency, and as a result, the film formation becomes non-uniform.

In the above-mentioned constitutional example given as a typical example using parallel plate electrodes, the electrode size is 30 cm ×
When it exceeds 30 cm or the frequency exceeds 30 MHz, the influence of the standing wave becomes remarkable, and it becomes difficult to achieve the minimum required film thickness uniformity ± 10% for semiconductor film formation.

FIG. 11 shows an example of voltage distribution due to a standing wave at 100 MHz. FIG. 11 also shows the ion saturation current distribution at the same time. Since the ion saturation current distribution is almost equal to the electron density distribution and is easy to measure, it is generally used as an index of plasma distribution. It can be seen from the voltage distribution that a standing wave is generated on the electrode, and the ion saturation current distribution, that is, the plasma distribution is correspondingly non-uniform.

On the other hand, FIG. 9 and FIG. 10 given as typical examples of the case where the ladder electrode is used, in addition to the case where the ladder electrode is used, four standing waves which are remarkably generated by one-point feeding are provided. It is characterized by being reduced by supplying power to the. 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.

FIG. 12 shows the voltage distribution generated on the ladder electrode when four points of power are fed at 60 MHz and 100 MHz. At 60 MHz, a relatively uniform voltage distribution is shown, but at 100 MHz, it becomes non-uniform. Further, it is necessary to find the optimum positions of the four feeding points by trial and error, which is very time-consuming. Further, if the film forming conditions such as gas pressure and high frequency power are changed, there is a problem that the optimum position is changed.

The above-mentioned problems have attracted attention at academic societies, and so far, for example, the document Mat. Res. Soc. Symp. Proc. Vol. 3
77, pp.27, 1995, it has been proposed to connect a lossless reactance (coil) to the opposite side of the parallel plate from the feeding side. This is because by changing the reflection condition from the electrode end of the standing wave, a part of the standing wave waveform with a relatively flat distribution, for example, the vicinity of the maximum of a sine wave, is generated on the electrode and It is intended to reduce the generated voltage distribution. However, this method is not eliminate the standing waves fundamentally, since the flat portion of the sine wave is only to be generated on the electrode, the uniform portion is obtained in the wavelength of the high frequency 1 / It is up to about 8 and it is impossible in principle to make the range beyond that uniform. FIG. 13 shows a voltage distribution when one end of the parallel plate electrode is terminated with a lossless reactance (coil) at 100 MHz. In this way, the voltage component in the region about 30 cm away from the terminal end
Although the cloth is uniform, the voltage distribution in the area further apart is not uniform, and the portion corresponding to this area cannot be used for film formation.

As described above, in plasma generation using high frequency, in the conventional technique, a very large substrate having a size of 1 m × 1 m or more is generated, a uniform plasma is generated in a large area, and uniform treatment is performed. I couldn't do it.

As a technique similar to the present invention, there is a technique for supplying two different high frequencies to two discharge electrodes, for example, M. Noisan, J. Pelletier, ed., "M.
icrowave Excited Plasmas ", Technology, 4, second i
mpression, pp. 401, Elsevier Science BV 1999.

However, the purpose of this technique is to use one high frequency wave for plasma generation and the other high frequency wave for controlling the surface bias voltage of the insulating substrate, and to determine the inflow amount of active ions and the like into the substrate. This is to control the incident energy, which is completely different from the object of the present invention to generate a uniform plasma in a large area and perform a uniform treatment for a very large substrate exceeding 1 m × 1 m.

The present invention has been made in order to solve the above problems, and in plasma CVD utilizing high frequency (VHF), a large substrate is used to generate a uniform plasma over a large area for uniform treatment. It is an object of the present invention to provide a method for supplying power to a discharge electrode, a high-frequency plasma generation device, and a semiconductor thin film manufacturing method that can perform the above.

[0020]

The first aspect of the invention of a high-frequency discharge electrode for solving the above-mentioned problems is to eliminate the standing wave generated on the electrode in principle and to make the voltage distribution uniform in consideration of such circumstances. By doing so, it was devised to form a uniform film even on a substrate having a very large size exceeding 1 m × 1 m.

The causes of non-uniformity of the plasma density at high frequencies are, as described above, the generation of standing waves on the electrodes, the influence on the voltage distribution due to the presence of stray inductance, and the mutual interference between plasma and high frequencies. Although it has been considered, the inventors of the present invention have diligently studied this, and as a result of the problems to be solved by the invention, found that the main cause is standing wave generation on the electrode. Therefore, as a means for eliminating the generation of standing waves in principle, it was considered to supply two frequencies to the electrodes to generate peat.

Below, for simplification, the explanation will be simplified. That is, considering the case of simplifying to one dimension and supplying two frequencies from both ends of one electrode,
If the attenuation of each high frequency wave is negligible, each amplitude is 1 and the phase constant is equal, and the reflection at the electrode end is small and negligible, the high frequency waves supplied from both ends are It is given by equations (1) and (2).

Φ ₁ = cos (ω ₁ t−k ₁ z) (1) φ ₂ = cos (ω ₂ t + k ₂ z) (2) where ω is the angular frequency (rad) of each wave. / S),
k is the wave number (rad / m), t is the time (s), and z is the position (m).

The wave number k is expressed by the following equation (3) using the phase velocity v (m / s) and the angular frequency ω.

K ₁ = ω ₁ / v ₁ , k ₂ = ω ₂ / v ₂ (3) The voltage distribution φ on the electrode is represented by the sum of these waves, that is, the following equation (4).

Φ = φ ₁ + φ ₂ = cos (ω ₁ t−k ₁ z) + cos (ω ₂ t + k ₂ z) = ₂ cos (ω _ave t−k _mod z) cos (ω _mod t−k _ave z) ... (4) _{where, ω ave = ω 1 + ω} 2/2, ω mod = ω 1 -ω 2/2, k ave = k 1 + k 2/2, k mod = k 1 -k 2/2 first, Consider the case where ω ₁ = ω ₂ , that is, the case where high frequencies of the same frequency are supplied from both ends. This is equivalent to, for example, the case where high frequency power is distributed and supplied from a single power source to the two, or a case where a plurality of high frequency power sources are operated in synchronization with the high frequency from a single oscillator and the output is supplied. To do. In this case, the voltage distribution φ is expressed by the following equation (5).

[0027] _{φ = 2cos (ω 1 t)} cos (-ω 1 / v 1 · z) ...... (5) from the above equation (5), the angular frequency ω ₁ of the carrier wave cos (ω ₁
It can be seen that a standing wave composed of t) and the envelope cos (−ω ₁ / v ₁ · z) is generated.

On the other hand, when ω ₁ ≠ ω _{2 with} different frequencies,
The voltage distribution φ is obtained by the following equation (6).

Φ = 2 cos (ω _ave t−k _mod z) cos (ω _mod t−k _ave z) (6) From the above equation (6), the carrier wave cos of the angular frequency ω _ave
(Ω _ave t−k _mod z) and a modulation wave cos of an angular frequency ω _mod generally called “beat” or “beat”
(Ω _mod t-k _ave z), the modulated wave moves spatially and does not become a standing wave.

The present invention has been made based on this principle, and as described in claim 1, the substrate to be processed held by the single holding electrode and the single discharge electrode are separated from each other in the discharge vessel. A method of supplying power to a discharge electrode, which is arranged in a face-to-face relationship and generates a substantially uniform discharge state between the discharge electrode and a substrate to be processed in a wide range, wherein the single discharge electrode is a ladder.
-Shaped or mesh-shaped, and the single
Discharge electrode was supplied with a plurality of high-frequency power source for independent frequency different oscillation frequencies from each other, said plurality of
The oscillation frequency oscillated from the high frequency power source of 20 to 200
Oscillation between multiple high frequency power supplies in the MHz range
The frequency difference should be within 20% of the oscillation frequency of each high frequency power supply.
And causes a modulated wave component by the difference of the oscillation frequency, thereby the envelope component of the voltage distribution caused on the single discharge electrode is displaced along said single discharge electrodes, wherein the single
The generation of a standing wave as a voltage distribution generated in the discharge electrode is suppressed. In addition, it is stated in claim 2.
As such, the present invention provides a single discharge electrode in a ladder or mesh.
A set of multiple high-frequency power sources that have an eye shape and are independent of each other.
Multiple feeds that are branched and connected from each
Power is supplied to each of the single discharge electrodes via a group of electric points.
At this time, a different one from each of the plurality of feeding points
Supply high frequency of oscillation frequency,
From the oscillation frequency of 20 to 200 MHz
And the difference in oscillation frequency between the plurality of high frequency power sources
Within 20% of the oscillation frequency of the high frequency power supply,
The difference in number causes a modulated wave component, which
The envelope component of the voltage distribution generated at one discharge electrode is
Displace along the discharge electrode of the
To suppress the generation of standing waves as a voltage distribution that occurs
Characterize. In this way, by supplying two or more high frequencies of different frequencies to a single discharge electrode,
High-speed and high-quality films can be obtained by using a high- frequency wave (VHF) having a frequency of 20 to 200 MHz , for example, 1 m × 1 m.
Even for a device with a very large substrate size that exceeds the limit, generation of standing waves in the discharge area between the discharge electrode and the substrate to be processed can be suppressed, and uniform plasma and uniform processing can be performed. become.

The second aspect of the present invention is to provide a method for protecting the power supply necessary for supplying high frequency to the electrodes from two or more power supplies.

The third aspect of the present invention provides a method for improving the processing efficiency by setting the cycle of plasma generation to a cycle in which active molecules in plasma necessary for the plasma processing are efficiently generated. It is a thing.

The fourth aspect of the present invention is to make the period of plasma generation effective for suppressing the generation of particles or discharging the particles from the discharge region.
It is intended to provide a method for reducing particles, improving film quality, and making the film pressure distribution uniform.

Details will be described below for each claim.

In order to solve the above-mentioned problems , claim 1 or
Invention of the feeding method of the second discharge electrodes, the two frequencies (omega
_As a concrete means for supplying ₁ ≠ ω ₂ ) to the electrodes, the aim is to obtain the effect of preventing the occurrence of standing waves by using a plurality of independent high frequency power supplies. Usually, when two power supplies of 60 MHz are prepared, for example, there are inherent differences in the configuration of the oscillators incorporated in each power supply, and therefore there is usually a difference in oscillation frequency of several hundreds of kHz. On the other hand, the frequency difference between each high frequency power source
The frequency of one of the
If they are misaligned, the performance of film formation and etching will not be optimal.
Prevents this because it significantly decreases from the wave number performance
Therefore, the frequency difference between multiple high frequency
It is within 20% of the oscillation frequency of the wave power source. Therefore, ω ₁ ≠ ω ₂ is automatically established due to the difference in oscillation frequency between the two independent power supplies, and the modulated wave component co
s (ω _mod t−k _ave z) is generated, which can suppress the generation of a standing wave composed of the envelope cos (−ω ₁ / v ₁ · z) component, and solve the problem with a very simple system. Can be achieved.

[0036]

[0037]

[0038] Claim 4 is, when suppressing the standing wave by using a plurality of high-frequency power source, it is necessary one-dimensional modeling of the apply, a plurality of the discharge electrode as one specific conditions It is characterized in that the feeding points are arranged at positions symmetrical to each other.

According to a fifth aspect of the present invention, when suppressing a standing wave by using a plurality of high frequency power supplies, high frequency power supplies of high frequencies having different frequencies and phases from other high frequency power supplies are damaged. For the purpose of preventing, a matching device that performs impedance matching between the discharge electrode and the high frequency power source is provided, and between this matching device and the coughing high frequency power source, an isolator having a circulator and a dummy load load is inserted, This isolator protects the high frequency power source by reducing the incident high frequency power from the other high frequency power source to the high frequency power source.

In the sixth aspect , the frequency bandwidth of the isolator that can be actually easily manufactured is about 4% at a high frequency power of 1 kW or less. Therefore, considering the system construction within this range, The difference is within 4% of the average frequency. In addition,
Since the frequency bandwidth of the isolator that can be actually manufactured is about 1% when the high frequency power is about 2 kW, it is preferable that the difference between the frequencies of the high frequency power supplies is within 1% of the average frequency.

According to a seventh aspect of the present invention, when suppressing a standing wave using a plurality of power supplies, it is possible to prevent the power supplies from being damaged by high frequencies having different frequencies and phases from other power supplies. For the purpose, the output from other high frequency power supplies except the high frequency power supply is limited according to the magnitude of the high frequency power incident on the high frequency power supply from the discharge electrode side, and the high frequency power incident from the other high frequency power supply to the high frequency power supply is limited. By protecting the high frequency power source, the high frequency power source is protected.

[0042]

In claim 8 , the plasma is turned on when the cycle is slow.
Since the ON / OFF cycle is repeated, which adversely affects the film quality and other results. To prevent this, the condition necessary to continue the pseudo ON state is the period that is the reciprocal of the frequency difference. Is shorter than the annihilation life of the active atoms in the plasma generated at the discharge electrode, shorter than the annihilation life of the active molecules, or shorter than the annihilation life of the ions. In order to more effectively prevent the generation of standing waves, it is preferable to set the period to 1/2 or less of the annihilation life of active atoms.

In the ninth aspect , the plasma is turned on when the cycle is slow.
Since the ON / OFF cycle is repeated, which adversely affects the film quality and other results. To prevent this, the condition necessary to continue the pseudo ON state is the period that is the reciprocal of the frequency difference. Is to shorten. For example, specifically for a silicon thin film formation using silane, the period which is the reciprocal of the frequency difference is calculated by the following equation (7): SiH ₃ active molecule life τ: τ = (Δx) ² / (2D) (7) where D is the diffusion coefficient D = 2.5 × 10 ³ (cm
² s ⁻¹ ), Δx is characterized by being shorter than either the distance (cm) from the electrode to the substrate or the lifetime of the hydrogen atom radical of 1.1 × 10 ⁻⁴ seconds. In order to prevent the effect of ON / OFF more effectively, the cycle should be 1/2 of the lifetime τ of the SiH ₃ active molecule.
Or less, or the life of hydrogen atom radical 1.1 ×
It is preferably 1/2 or less of 10 ⁻⁴ seconds.

According to a tenth aspect , active atoms, active molecules, or ions in the plasma are turned off after the plasma is generated.
For applications that start to occur in time, for example, for applications such as etching, the cycle is purposely slowed to intentionally create a plasma OFF time and sufficient OFF to generate active atoms or molecules or ions in the plasma. Hold the time and generate the next plasma before the number of active atoms, active molecules or ions in the plasma increases once and finally it almost disappears because there is no plasma and then turn it off again. As a condition for efficiently continuously generating the active atom or active molecule or ion, the period which is the reciprocal of the frequency difference is 1 time or more than the generation time of the active atom in the plasma generated at the discharge electrode. Or less than 1 time, or 1 time to 10 times less than the generation time of the active molecule,
Alternatively, it is characterized in that the time is 1 to 10 times the ion generation time. In order to prevent the generation of active atoms or active molecules more effectively, it is preferable that the period is 2 times or more and 4 times or less the generation time of active atoms or the like.

The eleventh aspect of the present invention is characterized in that the period, which is the reciprocal of the frequency difference, is set to 1 second or less. When the period is shorter than this, the particle generation time is limited, and as a result, the particle generation amount is reduced. In addition, in order to substantially eliminate the generation of particles, the period is preferably set to 1 millisecond or less.

A twelfth aspect of the invention is characterized in that the period, which is the reciprocal of the frequency difference, is made longer than the discharge region residence time t (second) of the raw material gas calculated from the following equation (8). . When the cycle is longer than this, dissociation of the source gas molecules is promoted and the generation of active atoms (active species, ions) is facilitated, so that the amount of particles generated is reduced. In addition, in order to substantially eliminate the generation of particles, it is preferable to set the cycle to be twice or more as long as the source gas residence time t in the discharge region.

T = (S · Δx) / Q (8) Q = (M · R · T) / P where S is the substrate area (cm ² ) Δx is the distance from the discharge electrode to the substrate (cm) Q Is the volumetric flow rate (cm ³ / sec) M is the mass flow rate (mol / sec) R is the gas constant ((atm · sec) / (K · cm ³ )) T is the absolute temperature of the gas (K) P is the discharge space Pressure (atm)

[0049]

[0050]

According to a thirteenth aspect , discharge gas plasma is generated by using the above-mentioned power feeding method, and the discharge gas plasma is moved spatially and temporally to enhance generation of active molecules in the discharge gas plasma. It is a plasma generation method characterized by increasing efficiency.

According to a fourteenth aspect of the present invention, the discharge gas plasma is moved spatially and temporally by using the above-described plasma generation method, so that the process of forming a semiconductor thin film or the process of etching can be made uniform or speeded up. It is a characteristic semiconductor manufacturing method.

[0053]

According to a fifteenth aspect of the present invention, the discharge gas plasma is moved spatially and temporally by using the above-described plasma generation method, so that the surface treatment on the object to be treated such as a semiconductor substrate is made uniform or accelerated. The surface treatment method is characterized in that

[0055]

[0056]

Various preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

(First Embodiment) A high-frequency plasma generating apparatus according to a first embodiment of the present invention will be described with reference to FIG. The device 1A is a high-frequency plasma generator used for forming a Si semiconductor thin film for a solar cell, and a ladder electrode 3 as a discharge electrode is provided in a reaction vessel 2 of the device.
03 and the earth electrode 3. The reaction vessel 2 is made airtight, and a gas supply pipe 17 and an exhaust pipe 18 are opened at appropriate places. The gas supply pipe 17 communicates with a gas supply source (not shown), and the film forming gas is introduced into the reaction container 17 through the gas supply source. The exhaust pipe 18 communicates with the suction side of a vacuum pump (not shown). By the way, the internal pressure of the reaction vessel 2 is 1 × 10 ⁻⁶ To by the vacuum pump.
It can be evacuated to about rr.

The earth electrode 3 as a holding electrode and the ladder electrode 303 as a discharge electrode are separated by a predetermined distance (for example, 20).
They are arranged face-to-face with a spacing of mm). The ground electrode 3 has a mechanism (not shown) for holding the glass substrate 16 as the object to be processed, and has a built-in heater (not shown) for heating the substrate 16. The ground electrode 3 is
When the substrate 16 to be processed has a 2.0 m × 2.0 m square size, it has a 2.1 m × 2.1 m square size and is grounded. Such a large substrate 1 without causing standing waves
In order to generate discharge plasma between the earth electrode 3 holding 6 and the earth electrode 3, the ladder electrode 303 has an oscillation frequency of 20 to
A plurality of high frequencies having a frequency difference within 20% of the oscillation frequency in the range of 200 MHz are applied to generate the modulated wave component cos (ω _mod t-k _ave z) represented by the above equation (6). The gas outlet of the gas supply pipe 17 is preferably opened rearward of the ladder electrode 303, and the gas is preferably supplied in parallel from a plurality of locations.

The ladder electrode 303 is formed by assembling a plurality of parallel vertical electrode rods 304 and a pair of horizontal electrode rods 305 in a grid pattern, and is parallel to the substrate 16 held by the ground electrode 3. It is arranged face-to-face.

On the ladder electrode 303, four feeding points 9a,
9b ₁ is provided. Two of these first feeding point 9a is provided on one lateral electrode rod 305, a second feeding point 9b ₁ of the two is provided on the other lateral electrode rods 305. The feeding points 9a and 9b ₁ are located at positions where the lateral electrode rod 305 is divided into three substantially equal parts.

A matching device 7a, a power meter 6a, and a power meter 6a are connected to the two first feeding points 9a through a branching coaxial cable 8a.
The first high frequency power supply 5a is connected in this order. First
The high-frequency power source 5a has a built-in high-frequency oscillator that oscillates a high-frequency wave (VHF) having a frequency of 60.0 MHz.
High-frequency (VHF) power having a frequency of 60.0 MHz is supplied to the ladder electrode 303 via one of the first feeding points 9a. The coaxial cable 8a on the electrode side from the matching unit 7a was branched using a T-branch plug.

On the other hand, the matching unit 7b and the power meter 6 are connected to the second feeding point 9b ₁ via the branched coaxial cable 8b.
b, the second high frequency power source 5b are connected in this order.
The second high frequency power supply 5b is independent of the first high frequency power supply 5a and has a high frequency (VHF) of 60.3 MHz.
And a high-frequency oscillator that oscillates, and the frequency of 60. is applied to the ladder electrode 303 via the two second feeding points 9b ₁ .
High-frequency (VHF) power of 3 MHz is supplied. The coaxial cable 8b on the electrode side from the matching unit 7b was branched using a T-branch plug.

When supplying the high and high frequency waves (VHF) of different frequencies to the ladder electrode 303 through the feeding points 9a and 9b ₁ facing each other in this way, two high and high frequency waves (VH) are supplied.
The frequency difference between F) (0.3 MHz in this embodiment) is important. The effect will be described later.

In the present embodiment, the feeding points 9a and 9b ₁ are provided on the two opposing lateral electrodes 305 of the ladder electrode 303 at symmetrical positions with the center of the entire electrode as the middle point.
Is arranged so that a one-dimensional voltage distribution is generated in each of the vertical electrode rods 304. As a result, a phenomenon in which a standing wave, which will be described later, is moved at high speed is observed, and the plasma generation distribution in the vertical direction on each vertical electrode rod 304 becomes uniform, and the plasma between each vertical electrode rod 304 is also increased. The generation distribution (plasma distribution in the lateral direction) could also be made uniform.

The latter plasma generation distribution is provided for each of a plurality of high-frequency power supplies that are independent of each other.
Multiple power feeds branched from each power feed path and connected
By increasing the point group from two points each above and below (total 4 points) to 4 points above and below each (total 8 points) and 8 points above and below each (total 16 points), the plasma generation distribution can be made more uniform. Can be planned.

Further, in this embodiment, two power sources 5a and 5b are used.
Therefore, the power is supplied from each of the two upper and lower power supply points, but by increasing the number of power supplies, the plasma generation distribution can be made more uniform. For example, high frequency (VH) of different frequency from four power sources to each of four feeding points
F) By supplying power respectively, it is possible to further improve the uniformity of plasma generation distribution.

In FIG. 2, the abscissa represents the position on the ladder electrode (arbitrary value) and the ordinate represents the emission intensity (arbitrary value), and the emission intensity of the plasma generated using the apparatus 1A of the present embodiment. It is a characteristic diagram which shows the result of having measured with CCD camera. In the figure, the three low values inside the size of the substrate are the locations where plasma cannot be seen due to the shadow of the vertical electrode rod due to the structure of the device, and are independent of the actual emission intensity distribution. is there. As is clear from this figure, in the generation of high-frequency plasma using the apparatus 1A, the uniformity of the light emission distribution, that is, the plasma distribution ± 7% (maximum value 127 / minimum value 11
It turns out that 1) can be achieved.

[0068] This is, of high-frequency power source 1 and the high-frequency power supply 2 issued
It is considered that the standing wave could be prevented from standing on the discharge electrode due to the "beat" due to the frequency difference of 0.3 MHz within 20% of the vibration frequency, that is, 300 kHz. Or, the standing wave that may have occurred on the discharge electrode is
It can be interpreted that it was possible to move at high speed for 300,000 wavelengths per second. That is, the standing wave distribution is generated when viewed at a very short moment, but it is considered that the distribution is uniform when viewed on a time average because the standing wave distribution is moving at high speed.

On the other hand, the larger the frequency difference is, the faster the moving speed of the standing wave should be, but the high frequency (V
HF) In order to obtain the film-forming speed and film-forming quality by making the most of the original characteristics, the high-frequency oscillation frequency required to obtain the film-forming speed and film-forming quality is in the range of 20 to 200 MHz. > It is not preferable to use a frequency difference that differs by more than 20% from the number. Further, in order for the impedance matching device used for preventing the high frequency power from entering the power source to function, it is more preferable that the difference between the oscillation frequencies is within 1%. Since the difference in the oscillation frequency is about 0.5% in this example, the quality of the film deposition rate was good and the incidence of high frequency on the power supply could be suppressed to a low value of about 100 W, as will be described later. .

Next, the a-Si film formation and the microcrystalline Si film formation were performed by the following procedure.

First, a 2 m × 2 m square substrate 16 for forming a Si thin film was placed on the substrate heater 3 set at 200 ° C., for example. SiH ₄ gas is introduced from the gas supply pipe 17 at a flow rate of 2000 sccm, and the fine crystal S
In the case of i film formation, hydrogen gas, for example, was flowed at about 50,000 sccm in addition to SiH ₄ gas. The pressure in the reaction vessel 1 was adjusted to, for example, 200 mTorr by adjusting the exhaust speed of a vacuum pump system (not shown) connected to the vacuum exhaust pipe.

While adjusting the first and second matching units 7a and 7b so that the high frequency power is efficiently supplied to the plasma, the frequency of 60.0M from the first high frequency power source 5a.
High-frequency (VHF) power of Hz and high-frequency (VHF) power of frequency 60.3 MHz are supplied from the second high-frequency power source 5b, and the total power from both power sources 5a and 5b is 3000 W, for example. To supply the high frequency (VHF) power to the substrate 16 and the ladder electrode 30.
Plasma was generated between 3 and 3. Si in plasma
H ₄ was decomposed and an a-Si film or a microcrystalline Si film was formed on the substrate surface. For example, by performing film formation in this state for about 10 minutes, a film having a required thickness was formed. The film thickness distribution of the formed sample was measured and the feeding point position was finely adjusted so that the optimum distribution could be obtained. The film forming speed can be as high as 1.0 nm / sec in microcrystalline film forming,
The uniformity was ± 10%, and the uniformity required for Si thin film semiconductors for solar cells was achieved.

Further, when the quality of the formed film was measured, the quality was high, for example, the Raman peak ratio exceeded 9: 1, and the refractive index, spectral characteristics, defect density, etc. were also about 5 cm × 5 cm. Same as small sample 60MHz
There was almost no difference from the case where the film was formed using.

This is because the ON / OFF of the plasma generated by the high-speed movement of the standing wave is sufficiently fast, that is, the frequency difference is 300 KHz, and therefore the ON / OFF is repeated 300,000 times × 2 times per second. One OF
F time becomes 2 × 10- ⁶ seconds or less, annihilation lifetime of SiH ₃ active molecule ((τ = (2 (cm )) 2 /(2×2.5×1
0 ³ (cm ² / sec)) = 8 × 10 ⁻⁴ sec) and the annihilation lifetime of hydrogen atom radicals 1.1 × 10 ⁻⁴
It is considered that the plasma ON / OFF can be substantially ignored in the film formation phenomenon because it is sufficiently shorter than the second).

Further, another effect obtained in this embodiment is that the number of particles generated during film formation is very small. As described in the prior document (S. Watanabe, S. Shiraishi, “Silane Gas Decomposition by High Frequency Modulation Discharge”, Discharge Research No.138, P27-36, 1992),
When the N time is 1 second or less, particle growth is suppressed, and preferably, when the ON / OFF frequency is 1 kHz or more, that is, when the ON time is 1 millisecond or less, substantially no particles are generated. Conceivable. That is, in the method of the present invention, the ON time is 2 × 1.
Since it is set to 0 ^-6 seconds or less, it can be inferred that particles are hardly generated.

Although detailed description and illustration are omitted, conversely, the OFF time can be lengthened to allow sufficient time for the particles to be discharged, and the particles can be discharged to prevent the increase. That is, the substrate area S is 200 × 200
cm ² , the distance Δx from the discharge electrode to the substrate is 2 cm, and the volume flow rate Q is 4 × 10 ⁵ cm ³ / sec, these values are substituted into the following formula (8) to discharge the source gas. The area residence time t is 0.2 seconds. Therefore, by setting the OFF time to a time longer than the time t, that is, 0.2 seconds or longer, preferably doubled 0.4 seconds or longer, particles are discharged from the plasma generation region, and the particles in the reaction container are discharged. It was also confirmed that the increase in γ was suppressed.

T = (S · Δx) / Q (8) In this embodiment, the case where a ladder electrode is used as an electrode is shown. Instead, it is a kind of ladder electrode.
In the case of using the mesh-shaped electrode reported in JP-A-11-11622, it took a lot of time to optimize the position of the feeding point,
A film thickness (plasma) uniformity of 10% could be obtained. It
In addition, even when using parallel plate electrodes, the feed point is optimized
It took more time and effort, but the power supply method of the present invention
12% film thickness (plasma) uniformity is obtained by using
It is possible to use without complicated electrodes such as ladder electrodes
Within the target film thickness (plasma) uniformity of 10%
Although it was not, a uniform film thickness (plasma) uniformity was obtained.
It was

Further, in this embodiment, the case where the frequency is around 60 MHz is shown, but it was confirmed that the same effect was obtained near 20 MHz and around 200 MHz.

(Second Embodiment) An apparatus according to a second embodiment of the present invention will be described with reference to FIG.
FIG. 3 is a diagram showing a power supply circuit of a device 1B according to a second embodiment obtained by modifying the high frequency (VHF) power supply circuit of the device 1A of the first embodiment shown in FIG. This change of the power supply circuit has an advantage that the operating condition range can be expanded in the device 1B of the present embodiment as compared with the device 1A of the first embodiment. This example is also used to perform uniform film formation on a 2 m × 2 m square substrate with high frequency, and the structure of the reaction container other than the power supply system is the same as that of the first embodiment. The explanation of the points common to both is omitted.

The device 1B of this embodiment is different from the device 1A of the first embodiment in the following five points.

Regarding the oscillating frequency of the high frequency power source, in the device 1A of the first embodiment, each high frequency power source 5
Two different frequencies are generated by utilizing the uncertainty of the crystal oscillators built in a and 5b. On the other hand, in the device 1B of the present embodiment, the frequency difference is controlled by the two-wave signal generator 20 to be a constant value. In the former (apparatus 1A), the frequency difference cannot be arbitrarily selected, and therefore, for example, the frequency difference is only 10 Hz.
If the two are combined, the standing wave is 10Hz
It moves only at this point, and the plasma turns on and off at that cycle, giving a bad influence to the film formation. Further, the oscillation frequency difference is not stable in time, and as a result, the reproducibility may be low. On the other hand, in the latter case (device 1B), the operation can be performed while fixing the optimum frequency difference.

In the device 1A of the first embodiment, the protection circuits (not shown) for the high frequency power supplies 5a and 5b are also independent. On the other hand, the device 1B of the present embodiment has only one protection circuit 22 and has the respective power supplies 5a and 5b.
The incident power to the power meters 6a ₁ and 6b ₂ was measured, and if either of the magnitudes exceeded the limit value, the output of both power sources was limited. In the case of the former (apparatus 1A), for example, the incident power to the first power supply 5a (the sum of the reflected power and the incident power from the second power supply 5b) exceeds the allowable amount of the first power supply 5a and becomes large for some reason. If it happens, the protection circuit of the first power supply 5a functions to suppress the output of the first power supply 5a, but excessive incidence from the second power supply 5b cannot be suppressed at all and remains as it is. In some cases, the first power supply 5a may be damaged.

On the other hand, if the same phenomenon occurs in the latter (device 1B), the protection circuit 22 operates due to excessive input to the first power supply 5a, and the outputs of both the first and second power supplies 5a and 5b are suppressed. Since the incident power on the first power supply 5a is suppressed, the first power supply 5a is not damaged. If the cause of the excessive input from the second power source 5b is removed by adjusting the matching device 7b with the incident power suppressed,
The outputs of both power supplies 5a and 5b can be raised again, and desired power can be supplied.

In this embodiment, the isolator 24
Since a and 24b are respectively inserted in the first and second power feeding circuits to prevent excessive power from entering the power supplies 5a and 5b, no special protection circuit is required. However, when the reflected power exceeds the allowable power of the isolators 24a and 24b and the isolators 24a and 24b do not operate, the protection operation by the protection circuit 22 is necessary. In the device 1A of the first embodiment, the means for suppressing the electric power (sum of reflected electric power and incident electric power from the second electric power source 5b) incident on the first electric power source 5a is a matching unit 7.
It was only a. On the other hand, in the device 1B of the present embodiment, an isolator 24a including a circulator and a load,
By inserting 24b, the power source 5 is supplied from the electrode 303 side.
It is configured to eliminate the electric power incident on a and 5b.

In the former (apparatus 1A), even if the output of the first power source 5a reflected from the electrode 303 can be completely reduced to zero by the matching unit 7a, the other power source, that is, the second power source 5b, outputs the electrode 303. Through the matching unit 7a and the first power source 5
Since the phase and frequency of the electric power incident on a are different,
It cannot be zero at the same time. Therefore, when this electric power is large (the electric power passing through the electrode 303 changes depending on the plasma generation state or the like), the large electric power is incident on the first power source 5a, and the first power source 5a. The first power supply 5a may be broken due to excessive input in the worst case. Especially, when there is no plasma load before plasma is generated, such a situation is likely to occur.

On the other hand, since the isolators 24a and 24b are inserted in the latter (device 1B) power supply circuit,
All of the incident power to the power supplies 5a and 5b can be absorbed by the load, and destruction of the power supplies 5a and 5b due to excessive input can be prevented.

When the isolators 24a and 24b are used, the frequency bandwidth of the isolator having the rated value of the high frequency power of kilowatt class as in this embodiment is very narrow. That is, the frequency bandwidth at a high frequency power of 1 kW or less is about 4% of the used frequency, and the high frequency power 2
Since it is about 1% at about kW,
It is necessary to suppress the frequency difference between the power source 5a and the second power source 5b to these values. In the present embodiment, the oscillation frequency of the first power supply 5a is set to 60.2 MHz, and the oscillation frequency of the second power supply 5b is set to 59.8 MHz.
The difference in the oscillating frequency of 5b was kept within 0.6 MHz, which corresponds to a frequency bandwidth of 1% in the case of the 2 kW rating.

In the apparatus 1A of the first embodiment, one power meter 6a, 6b is provided in each system (two in total), whereas in the apparatus 1B of this embodiment, two power meters are provided in each system. Power meters 6a ₁ , 6a ₂ , 6b ₁ and 6b ₂ were provided respectively (four units in total). Isolators 24a, 2 in the power supply circuit
Since 4b is inserted, the incident power to the power supplies 5a and 5b, that is, the power meter 6a, is normally provided in any matching state.
The reflected power at ₁ , 6a ₂ is zero. Therefore, in order to optimize the matching state, it is necessary to install power meters 6a ₂ and 6b ₂ on the matching device side with respect to the isolators 24a and 24b and measure the return power from the matching devices 7a and 7b.

In the device 1A of the first embodiment, the matching device 7
Although a T-branch plug is used to branch the coaxial cables 8a and 8b on the electrode side from a and 7b, the apparatus 1B of the present embodiment, on the other hand, has uneven plasma loads and changes over time. The distributors 26a and 26b are used so that stable power distribution can be achieved.

With the above improvements, the total input power is 4 kW
Is input, and the film forming speed is 1.
A high speed of 5 nm / sec was obtained. The film thickness uniformity was ± 10%. This clears the film thickness uniformity required for Si thin film semiconductors for solar cells.

(Third Embodiment) An apparatus according to a third embodiment of the present invention will be described with reference to FIG.
FIG. 4 is a diagram showing a power supply circuit of a device 1C according to a third embodiment obtained by modifying the high frequency (VHF) power supply circuit of the device 1B of the second embodiment shown in FIG.

The device 1C has two independent power supplies 5a and 5b.
The oscillator 20, the phase detectors 30a and 30b, the phase shifter 33, and the function generator 34. The two power supplies 5a and 5b have the same frequency of 60M.
High-frequency (VHF) power of Hz is independently supplied to the electrodes 303. Phase shifter 33
Is inserted between the oscillator 20 and the second power source 5b,
The phase of the high frequency power supplied from the power source 5b is shifted. As a result, the second power source 5b is connected to the electrode 30.
The high frequency power supplied to the power source 3 is not synchronized with the high frequency power supplied to the electrode 303 from the first power source 5a, and both power sources 5a and 5b
The power supplied from is shifted. The function generator 34 is for transmitting an arbitrary waveform signal to the phase shifter 33 and controlling the time change of the phase difference.

When a high frequency (VHF) with a frequency of 60 MHz is oscillated from the oscillator 20, the one system is amplified as it is by the first power source 5a and passes through the power meter 6a ₁ , the isolator 24a, the power meter 6a ₂ and the matching unit 7a. Is sent to the first phase detector 30a, the phase is detected by the phase detector 30a, and then supplied to the electrode 303 via the distributor 26a.

Another system of oscillation high frequency (VHF) is
The phase is shifted by the phase shifter 33, and thereafter the second phase is similarly set.
Power supply 5b, power meter 6b ₁ , isolator 24b,
The signal is sent to the second phase detector 30b via the power meter 6b ₂ and the matching device 7b, the phase is detected by the phase detector 30b, and then supplied to the electrode 303 via the distributor 26b.
In this case, the function generator 34 controls the phase shifter 33 so that the phase difference between the system a and the system b changes with time. That is, the time change of the phase difference was controlled by inputting the arbitrary waveform signal generated by the function generator 34 to the phase shifter 33. Regarding the phase difference, the phases of the systems a and b were detected by the phase detectors 26a and 26b immediately before the distributors 30a and 30b, and the detected phase signal was sent to the phase shifter 33 to perform feed hack control.

In this embodiment, when the fixed phase difference is fixed and the operation is performed, a standing wave occurs and the plasma becomes non-uniform. However, by changing the phase difference with time, the standing phase is changed. Waves can be moved, and uniform plasma generation and film thickness distribution can be obtained by time averaging during film formation time. The isolator 24a, 24b and the protection circuit 22 used in the third embodiment are
As in the case of the device 1B of the second embodiment, the power source 5
It contributes to the stabilization of the power supplies 5a and 5b when the a and 5b are operated.

At this time, if the phase difference is modulated too fast, the high frequency band widens and the isolator 24
The frequency bandwidth of a and 24b may be exceeded, and the isolators 24a and 24b may be damaged. Therefore, a spectrum analyzer (not shown) was connected to the phase detectors 30a and 30b, and the modulation speed was determined within a range where the bandwidth was within 1% of the rated frequency.

In this embodiment, when the frequency of the phase control signal from the function generator 34 is modulated at 10 kHz, the bandwidth does not exceed 1%.

(Fourth Embodiment) An apparatus according to a fourth embodiment of the present invention will be described with reference to FIG.
FIG. 5: is a figure which shows the electric power feeding circuit of the apparatus 1D which concerns on 4th Embodiment which changed the high frequency (VHF) electric power feeding circuit of the apparatus 1A shown in FIG.

The device 1D has two independent power supplies 5a and 5b.
And two independent power meters 6a and 6b, a mixer 40, a matching unit 7, and a distributor 26. In the fourth embodiment, first, two independent high frequency power supplies 5a,
High frequency (VHF) power of different frequency is output from 5b. This high frequency power is mixed by the mixer 40, and the ladder electrode 30 is passed through the matching unit 7 and the distributor 26.
3 was supplied.

In this embodiment, the film thickness uniformity within ± 10% can be obtained, and the intended purpose can be achieved with a simple power supply circuit. By the way, in the present embodiment, it takes time and effort to optimize the arrangement of the feeding points, and the maximum power value is limited to 2 kW by the rating of the mixer 40.

(Fifth Embodiment) An apparatus according to a fifth embodiment of the present invention will be described with reference to FIG.
FIG. 6 is a diagram showing a power supply circuit of a device 1E according to a fifth embodiment obtained by modifying the high frequency (VHF) power supply circuit of the device 1A of the first embodiment shown in FIG.

The device 1E includes an AM modulation oscillator 50, a high frequency power supply 5, a power meter 6, a matching unit 7 and a distributor 2.
6 and. The high frequency power of the high frequency power supply 5 was amplified by the AM modulation oscillator 50 to obtain an AM modulation high frequency having a carrier frequency of 60 MHz and a modulation frequency of 30 MHz. The power meter 6, matching unit 7, distributor 26
Power was supplied to the ladder electrode 303 via the.

According to this embodiment, a relatively uniform film thickness distribution of ± 15% can be obtained with a simple circuit.

(Sixth Embodiment) S. Samukawa, "Role
of Negative Ions in High-Performance Etching Usin
gPulse-Time-Modulated Plasma ", Extended Abstract o
f 4th International Conference on Reactive Plasma
s, SR 1.04, pp.415, 1998. As described in s, SR 1.04, pp.415, 1998., a halogen-based gas, for example, a chlorine-based gas is used to generate plasma, and chlorine negative ions (Cl ⁻ ) are generated to etch semiconductors. When used, conventionally, by turning on / off the power generated from a high frequency power source, a large amount of chlorine negative ions are generated by the electron attachment effect when plasma is generated and extinguished, and the plasma is extinguished, and the substrate surface is The effect of eliminating the generated wall charges is used to speed up the etching and improve the quality. In the present embodiment, this effect is aimed to be produced by moving the standing wave. Using the device 1B of the second embodiment shown in FIG.
The difference between the two different frequencies was set to 4 kHz, and plasma was generated using a halogen-based gas, for example, a chlorine-based gas to generate chlorine negative ions (Cl ⁻ ), and the semiconductor was etched. At this time, the plasma is in the ON state at the standing wave film and is in the OFF state at the node part. Therefore, by moving the standing wave at a high speed, a large amount of chlorine negative ions can be easily generated with high efficiency. Can be generated and etching can be performed at high speed.

The speed at which the standing wave is moved, that is, the phase change period, is longer than the generation time of chlorine negative ions of about 100 μsec shown in the above-mentioned reference paper so that it becomes 2 times or more and 4 times or less. It was set to about 250 μsec. At this time, the plasma OFF time is about 125 μsec, and sufficient negative ion generation can be obtained. This can be realized by setting the frequency difference to 4 kHz.

Furthermore, by using 60 MHz for the high frequency, 13.56 MHz used in the conventional method
Compared with the higher plasma density, the plasma sheath thickness becomes thinner, so that a large amount of chlorine negative ions generated in the plasma can efficiently flow into the substrate surface, and the etching rate can be further increased. As a result, an etching rate about 4 times that of the conventional single frequency of 13.56 MHz was obtained. In this embodiment,
It can also be applied to a surface treatment method such as plasma cleaning of a reaction container used for film formation of a silicon thin film or the like, so-called self-cleaning.

(Seventh Embodiment) An apparatus according to the seventh embodiment of the present invention will be described with reference to FIG.
FIG. 7: is a figure which shows the electric power feeding circuit of the apparatus 1F which concerns on 7th Embodiment which changed the electric power feeding point and high frequency of the apparatus 1A shown in FIG.

The device 1F comprises a first power source 5a for supplying a high frequency of 60.00 MHz and a frequency of 13.56 MH.
A second power source 5b for supplying a high frequency wave of z and two feeding points 9b ₂ and 9b ₂ attached to the ground electrode 3 are provided.

When this embodiment is applied to the etching of the silicon film by the halogen type gas NF ₃ , it is 60 MHz.
Due to the high density due to the high frequency, the substrate bias effect due to 13.56 MHz, and the effect of suppressing the standing wave due to the difference in frequency between the two, a large area of 1 m × 1 m can be obtained.
In addition, a high etching rate (about 10 nm / sec) was obtained.

The present embodiment can also be applied to a surface treatment method such as plasma cleaning of a reaction container used for forming a film such as a silicon thin film, so-called self-cleaning.

In the above-described first to seventh embodiments, the example of the four-point power feeding system has been mainly described, but the present invention is not limited to this, and the two-point power feeding system, the six-point power feeding system, and the eight-point power feeding system. The present invention can also be applied to other multi-point power feeding systems such as the system, 10-point power feeding system and 12-point power feeding system.

[0112]

According to the present invention, for a single discharge electrode
High frequency power of different frequency via multiple feeding points
The oscillating frequency oscillated from multiple high frequency power supplies
Multiple high frequency power supplies in the range of 20 to 200 MHz
The difference in the oscillating frequency between the
%, And a modulated wave component is generated due to the difference in the oscillation frequency.
This causes the envelope of the voltage distribution generated on a single discharge electrode.
Displaces the tangential component along a single discharge electrode to create a single discharge.
Suppresses the generation of standing waves in the voltage distribution inside the electrode
Therefore, it is possible to perform uniform processing on a very large substrate or thin film surface exceeding 1 m × 1 m by using high frequency (VHF) for large area film formation and etching processing. In plasma CVD film formation or the like, the plasma density can be made uniform over a wide range despite the high frequency. For example, in a very large area range of 2 m × 2 m square, the plasma distribution can be suppressed within a range of ± 7% by using the method of the present invention, and the uniformity required in the silicon thin film semiconductor for solar cells can be obtained. Can be substantially achieved.

[Brief description of drawings]

FIG. 1 is a configuration block diagram showing a high frequency power supply circuit and a reaction container of an apparatus used in a method for supplying power to a discharge electrode according to a first embodiment of the present invention.

FIG. 2 is a characteristic diagram showing the result of measuring the uniformity of plasma emission intensity distribution for the purpose of processing the 2 m × 2 m size substrate obtained according to the first embodiment.

FIG. 3 is a configuration block diagram showing a high frequency power supply circuit of an apparatus used for a method of supplying power to a discharge electrode according to a second embodiment of the present invention.

FIG. 4 is a configuration block diagram showing a high frequency power supply circuit of an apparatus used in a method for supplying power to a discharge electrode according to a third embodiment of the present invention.

FIG. 5 is a configuration block diagram showing a high frequency power supply circuit of an apparatus used for a method of supplying power to a discharge electrode according to a fourth embodiment of the present invention.

FIG. 6 is a configuration block diagram showing a high frequency power supply circuit of an apparatus used in a method for supplying power to a discharge electrode according to a fifth embodiment of the present invention.

FIG. 7 is a configuration block diagram showing a high frequency power supply circuit of an apparatus used in a method for supplying power to a discharge electrode according to a seventh embodiment of the present invention.

FIG. 8 is a cross-sectional block diagram showing a conventional PCVD apparatus that feeds power to one point in the center of the back side of a conventional parallel plate electrode.

FIG. 9 is a conventional PC in which power is supplied to four points of a ladder electrode.
Sectional block diagram showing a VD device.

FIG. 10 is a view of the conventional device of FIG. 9 seen from another direction.

FIG. 11 is a characteristic diagram showing a voltage distribution and an ion saturation current distribution when power is supplied to one point of an electrode at 100 MHz.

FIG. 12 is a characteristic diagram showing a voltage distribution when four points are fed to a ladder electrode at 60 MHz and 100 MHz.

FIG. 13 is a characteristic diagram showing a voltage distribution when one end of a parallel plate electrode is terminated with a reactance at 100 MHz.

[Explanation of symbols]

1A, 1B, 1C, 1D, 1E, 1F ... Plasma CVD
Apparatus, 2 ... reaction vessel, 3 ... ground electrode (substrate heater), 5a, 5b ... high-frequency power _{source, 6a, 6a 1, 6a 2} , 6b, 6b 1, 6b 2 ... power meter, 7a, 7b ... matcher, 8a , 8b ... coaxial cable, 9, 9a, 9b _1, 9b ₂ ... feeding point, 16 ... substrate, 17 ... gas supply pipe, 18 ... exhaust pipe, 20 ... transmitter, 22 ... protection circuit, 24a, 24b ... isolator, 26, 26a, 26b ... Distributor, 30a, 30b ... Phase detector, 33 ... Phase shifter, 34 ... Function generator, 40 ... Mixer, 50 ... AM modulation oscillator, 100 ... Parallel plate electrode type plasma CVD apparatus, 110 ... Ladder electrode type plasma CVD device, 303 ... Ladder electrode, 304 ... Vertical electrode rod, 305 ... Horizontal electrode rod.

(72) Inventor Yoshiaki Takeuchi 5-717-1, Fukahori-cho, Nagasaki-shi, Nagasaki Mitsubishi Heavy Industries, Ltd. Nagasaki Research Institute (72) Inventor Hiroshi Majima 5-717-1, Fukahori-cho, Nagasaki-shi, Nagasaki Mitsubishi Heavy Industry Co., Ltd. Nagasaki Research Institute (72) Inventor Tatsufumi Aoi 1-1, Atunoura-cho, Nagasaki-shi, Nagasaki Mitsubishi Heavy Industries Ltd. Nagasaki Shipyard (72) Inventor Masayoshi Murata 5-717, Fukahori-cho, Nagasaki-shi, Nagasaki Prefecture (56) References JP-A-7-14769 (JP, A) JP-A-57-131374 (JP, A) JP-A-5-156451 (JP, A) JP-A-7-142400 (JP, A) JP 10-326698 (JP, A) JP 2000-164578 (JP, A) JP 10-303188 (JP, A) JP 2000-150196 (JP, A) JP 1-149965 (JP, A) JP 5-291155 (JP, A) JP 1-195273 (JP, A) JP 6-204178 (JP, A) JP 7 -74162 (JP, A) JP 7-288196 (JP, A) JP 6-302588 (JP, A) JP 56-33839 (JP, A) JP 60-86831 (JP, A) ) JP-A-58-186937 (JP, A) JP-A-58-125830 (JP, A) JP-A-11-126698 (JP, A) JP-B-5-70930 (JP, B2) (58) Field (Int.Cl. ⁷ , DB name) H01L 21/205 C23C 16/505 H01L 21/3065 H05H 1/46

Claims (15)

(57) [Claims] 1. A substrate to be processed held by a single holding electrode and a single discharge electrode are arranged face-to-face in a discharge vessel with a space therebetween, and substantially between the discharge electrode and the substrate to be processed. A method of supplying power to a discharge electrode for generating a uniform discharge state in a wide range, wherein the single discharge electrode has a ladder shape or a mesh shape,
Oscillation frequency supplied by using a plurality of high-frequency power source, is oscillated from the plurality of high-frequency power source for independent high frequency respectively different <br/> Ru oscillation frequency to the single discharge electrode via the feeding point number with one another 20
To 200 MHz, and the plurality of high frequency power supplies
The difference in the oscillating frequency between the
% Within the then causes a modulated wave component by the difference of the oscillation frequency, thereby the envelope component of the voltage distribution caused on the single discharge electrode is displaced along said single discharge electrodes,
A method for supplying power to a discharge electrode, characterized in that the generation of a standing wave as a voltage distribution generated in the single discharge electrode is suppressed. 2. A substrate to be processed held by a single holding electrode.
And a single discharge electrode are placed facing each other in the discharge vessel.
The discharge electrode and the substrate to be processed,
It is a method of supplying power to the discharge electrode that generates a wide range of electrical states.
Therefore, the single discharge electrodes have a ladder shape or a mesh shape, and
Is it a power supply path provided for each independent high-frequency power source?
Via multiple feed points that are branched and connected
When supplying power to each of the single discharge electrodes,
Of one oscillation frequency that is different from each other
Frequency and supplies an oscillation frequency of 20 from the plurality of high frequency power supplies.
To 200 MHz, and the plurality of high frequency power supplies
The difference in the oscillating frequency between the
%, And a modulated wave component is generated due to the difference in the oscillation frequency.
The resulting voltage distribution on the single discharge electrode.
Displacing the envelope component of along the single discharge electrode,
Standing wave as a voltage distribution generated in the single discharge electrode
Of power supply to discharge electrode characterized by suppressing the generation of electricity
Law. 3. At least cos as the modulated wave component
A component represented by (ω _mod t−k _ave z) is generated.
And the envelope of the voltage distribution generated in the single discharge electrode
Express as at least cos (-ω ₁ / v ₁ · z) as a line component
Displace the component passed along the single discharge electrode
The method according to claim 1 or 2, characterized in that
Method. 4. The plurality of high frequency power supplies are respectively
The oscillation frequency is different, or the time difference of each phase difference is changed.
Different from each other, in a symmetrical position with respect to the single discharge electrode.
Powering the single discharge electrode from multiple installed power feed points
Either claim 1 or 2 characterized by the above
How to list. 5. The plurality of high frequency power supplies are provided in the single discharge.
Impedance matching between the electrode and the high frequency power source
A circulator and a
And an isolator with a dummy load load
An isolator is used to
By reducing the incident high frequency power, the high frequency power source
Either of claim 1 or 2 which protects
Or the method described in 1. 6. The difference between the frequencies of the respective high frequency power supplies is calculated by
6. The number is within 4% of the average of the numbers.
How to list. 7. The single discharge electrode side for each high frequency power source
High frequency power source depending on the size of high frequency power
Limits the output from other high frequency power supplies except
Reduce the incident high frequency power from the power source to the high frequency power source
It is characterized by protecting the high frequency power supply
The method according to claim 1, wherein 8. A cycle, which is the reciprocal of the difference between the oscillation frequencies, is
Extinction lifetime of active atoms in plasma generated at the discharge electrode
Shorter than life or shorter than the annihilation life of the active molecule
Or shorter than the annihilation life of ions
The method according to claim 1, wherein 9. A period, which is the reciprocal of the difference between oscillation frequencies, calculated from the following equation : SiH ₃ active molecule lifetime τ: τ = (Δx) ² / (2D) where D is a diffusion coefficient and D = 2.5 × 10 ³ (cm ² / sec), Δx is shorter than either the distance (cm) from the electrode to the substrate or the life of the hydrogen atom radical of 1.1 × 10 ⁻⁴ sec. Claim 1
Alternatively, the method according to any one of 2 above. 10. A cycle, which is the reciprocal of the difference between the oscillation frequencies,
Generation of active atoms in plasma generated at the discharge electrode
1 to 10 times the time, or the active molecule
It is more than 1 time and less than 10 times the growth time, or
A contract characterized by being 1 time or more and 10 times or less of the completion time
The method according to any one of claim 1 or 2. 11. A period, which is the reciprocal of the difference between oscillation frequencies, is set to 1
It is less than or equal to a second, and either of claim 1 or 2 is characterized.
The method according to Reka 1. 12. A cycle, which is the reciprocal of the difference between oscillation frequencies,
Source gas residence time t in discharge region calculated from the following equation
It is set to be longer than (seconds).
The method according to any one of 2 above. t = (S · Δx) / Q Q = (M · R · T) / P where S is the substrate area (cm ² ) Δx is the distance from the discharge electrode to the substrate (cm) Q is the volume flow rate (cm ³ / Sec) M is mass flow rate (mol / sec) R is gas constant ((atm · sec) / (K · cm ³ )) T is absolute temperature of gas (K) P is pressure of discharge space (atm) 13. The method according to any one of claims 1 to 12.
A discharge gas plasma is generated using the method described in
To move gas plasma spatially and temporally
Highly efficient generation of active molecules in the discharge gas plasma
A method of generating plasma, characterized by: 14. A plasma generating method according to claim 13.
Generating a discharge gas plasma using the discharge gas plasma
The semiconductor is moved by moving the space and time.
Uniform or high degree of body thin film formation or etching process
A method for manufacturing a semiconductor, characterized by accelerating speed. 15. A plasma generation method according to claim 14.
Generating a discharge gas plasma using the discharge gas plasma
By moving the robot spatially and temporally
To make the surface treatment of the body surface uniform or faster
A characteristic surface treatment method.