JP4554380B2 - Plasma generating apparatus and plasma generating method - Google Patents

Description

  The present invention relates to a plasma generation apparatus and a plasma generation method used for a process such as CVD, etching, or sputtering used in manufacturing a semiconductor, a liquid crystal display device, a solar cell, or the like.

In semiconductor manufacturing apparatuses such as a CVD (Chemical Vapor Deposition) apparatus using plasma, an electromagnetic wave coupling type apparatus using an antenna element is used for plasma generation.
On the other hand, with the increase in size of liquid crystal display devices and amorphous solar cells, a large-scale device that processes a large-area substrate is also desired for a semiconductor manufacturing device that performs processing using plasma.

  Since the frequency of the high frequency signal used in such a large semiconductor manufacturing apparatus is as high as 10 MHz to 2.5 GHz, the wavelength of the electromagnetic wave radiated from the antenna element is short. For this reason, it is more important to control the plasma density distribution that affects the uniformity of processing such as film formation.

Under such circumstances, it has been proposed to use a large-area plasma generating antenna in the plasma CVD apparatus shown in Patent Document 1.
Specifically, an array antenna in which a plurality of rod-like antenna elements are arranged in a plane is arrayed to make the spatial distribution of electromagnetic waves uniform and used for generating a large-area plasma.

JP 2003-86581 A

  However, in the plasma CVD apparatus disclosed in Patent Document 1, since the load of the antenna element changes due to the influence of the plasma generated by the radiation of the electromagnetic wave of the antenna element, the impedance (usually 50Ω) set in the feeder line It is difficult to consistently match. For this reason, the signal from the feeder line is reflected at the connection with the antenna element, the necessary power is not supplied to the antenna element, the electromagnetic wave radiation from each antenna element becomes uneven, and the density distribution of the generated plasma Is not uniform. As a result, the distribution of generated plasma becomes non-uniform, and problems such as non-uniform film formation by CVD are likely to occur.

  Therefore, in order to solve the above-mentioned problems, the present invention uses an array antenna in which a plurality of antenna elements composed of rod-shaped conductors whose surfaces are covered with a dielectric material are arranged in parallel and in a plane, and plasma is generated. An object of the present invention is to provide a plasma generation apparatus having a simple apparatus configuration capable of easily performing impedance matching so that the plasma is uniform when generated, and a plasma generation method for realizing such plasma generation. .

In order to achieve the above object, the present invention provides a plasma for generating plasma using an array antenna in which a plurality of antenna elements each made of a rod-like conductor whose surface is covered with a dielectric material are arranged in parallel and in a plane. A generator, a common high-frequency power source for generating high-frequency signals to be supplied to the plurality of antenna elements, and one of a capacitive element and an inductive element connected to the plurality of antenna elements, respectively, for impedance matching A plurality of impedance matching units having adjustment elements, a distributor connected between the plurality of impedance matching units and the high-frequency power source, a high-frequency signal supplied from the high-frequency power source to the distributor and a reflected wave thereof A first sensor for detecting current and voltage, and a plurality of impedance matching devices, respectively, Serial high-frequency signal is supplied to a corresponding impedance matching device from the distributor and a plurality of second sensor for sensing the current and voltage due to the reflected waves, the first of said plurality of antenna elements based on the detection signal by the sensor The high frequency power supply is controlled so as to approach the impedance matching state, the frequency of the high frequency signal output from the high frequency power supply is adjusted, and each antenna element is impedance matched based on detection signals from the plurality of second sensors. And a controller for controlling the capacitance of the capacitive element used as the adjustment element of each impedance matching unit or the inductance of the inductive element by controlling each of the plurality of impedance matching units so as to be in the state of A plasma generating apparatus is provided.

The adjustment element of each impedance matching unit includes a first capacitive element having one end connected to the distributor and a second capacitive element having one end connected to the antenna element. both the other end of the capacitive element and the other end of the second capacitor is grounded, the controller preferably controls the capacity of the first capacitor.
Such a plasma generation apparatus is preferably a CVD apparatus used for film formation of a substrate or an etching apparatus used for etching a substrate.

Further, the present invention is a plasma generation method for generating plasma using an array antenna in which a plurality of antenna elements each made of a rod-shaped conductor whose surface is covered with a dielectric material are arranged in parallel and in a plane, A high-frequency signal is generated, and the generated high-frequency signal is distributed and supplied to the plurality of antenna elements via a plurality of impedance matching units each having one of a capacitance element and an induction element for impedance matching. The high-frequency signal before distribution and the current and voltage due to the reflected wave are detected and the high-frequency signal distributed and supplied to the plurality of impedance matching units and the current and voltage due to the reflected wave are respectively detected and distributed. the high frequency signal and the plurality of antenna elements impedance based on a detection signal for the reflected wave The high frequency signal and the plurality of antenna elements based on a detection signal for the reflected wave is distributed and supplied to the plurality of impedance matching as well as adjust the frequency of the high frequency signal so as to approach the state of engagement of each of impedance matching A plasma generation method is provided, wherein the capacitance of the capacitive element used as the adjustment element of each impedance matching device or the inductance of the inductive element is controlled so as to be in a state.

When generating the plasma by using an array antenna arranged in mutually parallel and planar multiple antenna elements made of a conductor rod-shaped surface is covered with a respective dielectric, the frequency of the common frequency signals fed to each antenna element By controlling the above, impedance matching of each antenna element can be performed in common. For this reason, the configuration of the impedance matching device can be simplified, the followability of automatic control is improved, and the control time is shortened.

Hereinafter, the plasma generation apparatus and the plasma generation method of the present invention will be described in detail.
FIG. 1 is a schematic configuration diagram illustrating a configuration of a plasma CVD apparatus 10 which is an embodiment of the plasma generation apparatus of the present invention. FIG. 2 is a diagram for explaining the arrangement of the antenna elements of the CVD apparatus 10. In FIG. 2, a feeder line for transmitting a high-frequency signal is illustrated, and a controller and a control line for performing impedance matching described later are not illustrated.

The CVD apparatus 10 is an apparatus that performs a film forming process using plasma CVD on a processing substrate 12 such as a glass substrate or a silicon wafer.
The CVD apparatus 10 is provided on the reaction vessel 14, the substrate stage 16 on which the processing substrate 12 is placed, the wall surface of the reaction vessel 14, the inlet 18 for introducing the raw material gas, and the wall surface of the reaction vessel 14 for decompression. An exhaust port 20 for exhausting the source gas and the like, a gas radiation plate 24 for releasing the source gas into the reaction chamber, a plurality of antenna elements 22 provided in the reaction vessel 14, and the outside of the reaction vessel 14 An impedance matching unit 26, a high-frequency power source 28 that feeds power to the antenna element 22, a controller 30 that controls the high-frequency power source 28 and the impedance matching unit 26, and a current and voltage of a high-frequency signal fed to the antenna element 22 are detected. A first current / voltage sensor 32, a second current / voltage sensor 34 for detecting current and voltage in order to individually adjust the impedance matching unit 26, a first power - having a voltage sensor 32 and the distributor 33 provided between the second current-voltage sensor 34.

The reaction vessel 14 is a metal vessel, and the wall surface of the reaction vessel 14 is grounded.
The substrate table 16 is a table on which the processing substrate 12 is placed so that the processing substrate 12 faces the antenna element 22, and a heating element (not shown) for heating the processing substrate 12 is provided inside the substrate table 12. Furthermore, a grounded electrode plate (not shown) is provided. The electrode plate may be connected to a bias power source and applied with a bias voltage.

  The introduction port 18 is provided on the upper surface side of the reaction vessel 14 and is connected to a supply pipe 19 that supplies a source gas. The supply pipe 19 is connected to a source gas source (not shown). The source gas supplied from the introduction port 18 varies depending on the type of film formation. For example, in the case of a low-temperature polysilicon TFT liquid crystal, a silane gas is suitable for the production of a silicon film, and TEOS is suitable for the production of a gate insulating film. Used.

On the upper side of the reaction vessel 14, a raw material gas dispersion chamber 23 is configured to be partitioned from a lower reaction chamber 25 by a gas radiation plate 24.
The gas radiation plate 24 has a plurality of through holes of about 0.5 mm formed in a plate-shaped member made of SiC, and the source gas is radiated to the lower reaction chamber 25 at a constant flow rate. The gas radiation plate 24 may be made of a ceramic material or a plate-like member formed by CVD. A metal film is formed on the gas radiation plate 24 and is grounded.
The exhaust port 20 is connected to an exhaust pipe 21 connected to a vacuum pump (not shown) in order to make the atmosphere of the raw material gas whose pressure inside the reaction vessel 14 is reduced to a predetermined pressure.

In the upper part of the reaction chamber 22 below the gas radiation plate 24, a plurality of antenna elements 22 provided in an array are provided so as to face the gas radiation plate 24.
As shown in FIG. 2, the plurality of antenna elements 22 are arranged parallel to each other and in a planar shape to form an array antenna composed of monopole antennas. This array antenna is provided in parallel to the gas radiation plate 24 and the processing substrate 12 mounted on the substrate table 16.
As shown in FIG. 2, the antenna element 22 which is a monopole antenna protrudes from the wall surface in the reaction vessel 12 in the opposite direction to the adjacent antenna element 22, and the feeding direction is opposite. Each of these antenna elements 22 is connected to an impedance matching unit 26 that is a matching box.

Each antenna element 22 has a rod shape (may be a pipe) made of a conductor having high electrical conductivity, and is (2n + 1) / 4 times the wavelength of the high frequency used (n is 0 or a positive integer). Is the radiation length of the antenna element which is a monopole antenna. The surface of each antenna element 22 is covered with a dielectric such as a quartz tube. By covering the rod-shaped conductor with a dielectric, the capacity and inductance of the antenna element 22 are adjusted, whereby a high-frequency current can be efficiently propagated along the protruding direction of the antenna element 22, and electromagnetic waves can be transmitted. Can be efficiently radiated.
The antenna element 22 thus covered with the dielectric is electrically insulated and attached to the opening opened in the inner wall of the reaction vessel 14, and the high frequency current supply end side of the antenna element 22 is connected to the impedance matching unit 26. It is connected to the.

  Since the antenna element 22 is provided in the vicinity of the gas radiation plate 24, the electromagnetic wave radiated from the antenna element 22 is not grounded between the adjacent antenna elements 22 without causing the electromagnetic waves to influence each other. It acts on the electromagnetic wave formed in a mirror image relationship by the action of the metal film, and forms a predetermined electromagnetic wave for each antenna element. Furthermore, since the antenna elements 22 constituting the array antenna have a feeding direction opposite to that of the adjacent antenna elements 22, electromagnetic waves are uniformly formed in the reaction chamber 25.

The impedance matching unit 26 is provided with a capacitive element 26a whose one side is connected to the end of the antenna element 22, and a capacitive element 26b whose one side is connected to the feeder line 27. The capacitive element 26a and the capacitive element 26b The other side is grounded to each other.
The capacitance element 26b is configured such that the electrodes constituting the capacitance element are variably configured so that the capacitance (characteristic parameter) can be freely adjusted. The adjustment of the capacity is adjusted by a servo motor 26c that moves the electrode. The adjustment of the capacitance of the capacitive element 26b is used together with the adjustment of the frequency of a high-frequency signal generated by a high-frequency power source 28, which will be described later, to correct impedance mismatch caused by a change in the load of the antenna element 22 during plasma generation. Used.

The high frequency power supply 28 is configured by a high frequency oscillation circuit and an amplifier (not shown), and is configured such that the oscillation frequency is variable in accordance with a signal from the controller 30.
The controller 30 is a control part that changes the oscillation frequency of the high-frequency power supply 28 and adjusts the impedance matching unit 26 in accordance with detection signals from a first current / voltage sensor 32 and a second current / voltage sensor 34 described later. .

The first current / voltage sensor 32 detects the current and voltage in the vicinity of the output terminal of the high frequency power supply 28 in order to detect whether or not the high frequency signal from the high frequency power supply 28 is fed to the antenna element 22 with impedance matched. This is the part that detects the voltage. The first current / voltage sensor 32 is connected to the impedance matching unit 26 via the distributor 33. The second current / voltage sensor 34 is provided separately in the vicinity of the input end of each impedance matching unit 26 and is a part that detects current and voltage in order to adjust each impedance matching unit 26. When impedance matching is not performed, a reflected wave of a high-frequency signal is generated at a connection portion between the feeder line 27 and the antenna element 22, thereby causing a phase difference between current and voltage. Therefore, by detecting the current and voltage in the first current / voltage sensor 32 and the second current / voltage sensor 34, it is possible to detect whether the impedance is matched or mismatched.
Detection signals of the first current / voltage sensor 32 and the second current / voltage sensor 34 are supplied to the controller 30.

Based on the detection signals from the first current / voltage sensor 32 and the second current / voltage sensor 34, the controller 30 determines whether or not the impedance is in a matching state. This is a part that generates a control signal for controlling the servo motor 26c of the impedance matching unit 26 and supplies it to the high frequency power supply 28 and the servo motor 26c.
For example, when it is determined that each antenna element 22 is mismatched, the high frequency power supply 28 is controlled to adjust the frequency of the high frequency signal so that the plurality of antenna elements 22 are in an impedance matched state. . Thereafter, a control signal is generated so that impedance matching is individually performed for the servo motor 26c of the impedance matching unit 26 of the antenna element 22 that is still determined to be mismatched.
As described above, the controller 30 controls the frequency of the high-frequency signal common to the antenna elements 22 to bring all the antenna elements 22 close to the impedance matching state, and thereafter individually adjusts them by the servo motor 26c.
In the present embodiment, both the first current / voltage sensor 32 and the second current / voltage sensor 34 are provided. However, in the present invention, either one of the current / voltage sensors may be provided. However, in order to perform more accurate control, it is preferable that both the first current / voltage sensor 32 and the second current / voltage sensor 34 be provided.

In such a CVD apparatus 10, a raw material gas is fed into the reaction vessel 14 from the introduction port 18, and on the other hand, a vacuum pump (not shown) connected to the discharge port 20 is operated to set a vacuum atmosphere of about 1 Pa to several hundreds Pa normally. 14 in. By feeding a high frequency signal to the antenna element 22 in this state, electromagnetic waves are radiated around the antenna element 22. Thereby, plasma is generated in the reaction vessel 14 and the source gas radiated from the gas radiation plate 24 is excited to generate radicals. At that time, since the generated plasma has conductivity, the electromagnetic wave radiated from the antenna element 22 is easily reflected by the plasma. For this reason, the electromagnetic wave is localized in a local region around the antenna element 22.
Thereby, the plasma is localized and formed in the vicinity of the antenna element 22.

At this time, localized plasma is generated around the antenna element 22 that emits electromagnetic waves, so the load of the antenna element 22 also changes. For this reason, the antenna element 22 changes from the impedance matching state to the mismatching state, and the reflectance of the high-frequency signal supplied from the high-frequency power supply 28 at the connection portion with the antenna element 22 is high, so that the power feeding is sufficiently performed. No longer done. At that time, since the load variation of each antenna element 22 is also different, the state of mismatch in each antenna element 22 is also different. For this reason, the electromagnetic waves radiated from the antenna element 22 also have a distribution, and as a result, the density distribution of the generated plasma varies in space.
Such a spatial variation in the plasma density distribution is not preferable for the film forming process of the processing substrate 12 or the like. For this reason, the impedance matching of each antenna element 22 must be performed so that the radiation of electromagnetic waves from each antenna element 22 becomes constant and uniform plasma is generated.

Specifically, the impedance matching of the antenna element 22 is such that the phase difference between the current and voltage of the supplied high-frequency signal is zero, and the impedance of the antenna element 22 and the impedance of the feeder line 27 (for example, 50 ohms) are capacitive elements 26a. , 26b, the frequency of the high-frequency signal and the capacitance of the capacitive element 26b are adjusted.
In such adjustment, information on the current and voltage detected by the first current / voltage sensor 32 and the second current / voltage sensor 34 is supplied to the controller 30 as a detection signal.
The controller 30 sets the frequency of the high frequency signal and further the capacity of the capacitive element 26b based on the detection signal, and generates a control signal for controlling the high frequency power supply 28 and the servo motor 26c.
In this way, the control signal is supplied to the high-frequency power supply 28 and the servo motor 26c, and impedance matching between the antenna element 22 and the signal line 27 is performed.

FIG. 3A is a diagram showing a connection relationship between the antenna element 22 and the capacitive elements 26a and 26b in the impedance matching unit 26 of the CVD apparatus 10 shown in FIG.
In addition to FIG. 3A, the impedance matching unit 26 includes a capacitive element 26a and a capacitive element 26d connected in series to the antenna element 22 as shown in FIG. 3B, and the capacitive element 26a and the capacitive element. It may be configured to provide a high-frequency signal feeding point between 26d.
Also in this case, impedance matching between the antenna element 22 and the signal line 27 can be performed by controlling the frequency of the high frequency signal and controlling the capacitance of the capacitive element 26d.

In this embodiment, a capacitive element (capacitor) is used for impedance matching of the antenna element 22, but an inductance (characteristic parameter) may be controlled using an inductive element (inductor).
As described above, in the CVD apparatus 10, the capacitive element 26 b is provided for impedance matching for each of the plurality of antenna elements 22 provided in an array, and the capacitance (characteristic parameter) of the element and the high-frequency signal Control the frequency.

On the other hand, when the capacitive element 26a is to be controlled instead of controlling the frequency of the high frequency signal, in each impedance matching unit 26 provided corresponding to the antenna element 22, other than the servo motor 26c of the capacitive element 26b. In addition, it is necessary to provide a servo motor for the capacitive element 26a. For this reason, an impedance matching device becomes a complicated structure. For example, 32 expensive servo motors need to be provided for 16 antenna elements 22, and the number of controlled objects increases. For this reason, the cost of the entire CVD apparatus increases, and the followability of impedance matching also deteriorates as the number of controlled objects increases.
On the other hand, the high-frequency signal to be controlled in the CVD apparatus 10 according to the present invention is a signal common to each antenna element 22, and thus one impedance element (capacitance element 26 b) is provided in the impedance matching unit provided corresponding to each antenna element 22. May be controlled. For this reason, in each impedance matching device 26, it is only necessary to provide one servo motor 26c of the capacitive element 26b. Further, since the frequency of the common high-frequency signal fed to the antenna element 22 is controlled, fine adjustment for each antenna element 22 is performed by the capacitive element 26b while performing impedance matching in common for each antenna element 22. Can do. For this reason, the followability of the automatic control in the impedance matching unit 26 is improved, and the control time is shortened.

In the above embodiment, the frequency of the high frequency signal and the capacitance of the capacitive element are controlled. However, in the present invention, either the frequency of the high frequency signal or the capacitance of the capacitive element may be controlled. For example, when this device is in an impedance matching state before plasma generation, impedance matching can be roughly achieved by adjusting either the frequency of the high frequency signal or the capacitance of the capacitive element. is there.
However, in order to accurately perform impedance matching, it is preferable to control the frequency of the high-frequency signal and the capacitance of the capacitive element.
In addition, the CVD apparatus 10 of the above embodiment includes an array antenna in which a plurality of antenna elements are arranged in parallel and in a planar shape, but the plasma generation apparatus in the present invention is an apparatus that generates plasma using one antenna element. There may be.

  The plasma generation apparatus and the plasma generation method of the present invention have been described in detail above. However, the present invention is not limited to the above-described embodiment, and various improvements and modifications may be made without departing from the gist of the present invention. Of course. For example, the plasma generation apparatus of the present invention can be suitably used for an etching apparatus in addition to a CVD apparatus.

It is a schematic block diagram explaining the structure of the plasma CVD apparatus which is one Embodiment of the plasma production apparatus of this invention. It is a figure explaining arrangement | positioning of the antenna element of the CVD apparatus shown in FIG. (A), (b) is a figure which shows typically the structure of the impedance matching device used for this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Plasma CVD apparatus 12 Processing board | substrate 14 Reaction container 16 Substrate stand 18 Inlet 19 Introducing pipe 20 Exhaust outlet 21 Exhausting pipe
22 Antenna Element 23 Raw Material Gas Dispersion Chamber 24 Gas Radiation Plate 25 Reaction Chamber 26 Impedance Matching Device 28 High Frequency Power Supply 30 Controller 32 First Current / Voltage Sensor 34 Second Current / Voltage Sensor

Claims (4)

A plasma generation apparatus that generates plasma using an array antenna in which a plurality of antenna elements each formed of a rod-shaped conductor whose surface is covered with a dielectric material are arranged in parallel and in a plane,
A common high-frequency power source for generating a high-frequency signal to be supplied to the plurality of antenna elements;
A plurality of impedance matching units each connected to the plurality of antenna elements and having an adjustment element of any one of a capacitive element and an inductive element for impedance matching;
A distributor connected between the plurality of impedance matching units and the high-frequency power source;
A first sensor that detects a high-frequency signal supplied from the high-frequency power source to the distributor and a current and a voltage due to a reflected wave thereof ;
A plurality of second sensors that are respectively arranged corresponding to the plurality of impedance matching units and that detect a high-frequency signal supplied from the distributor to the corresponding impedance matching unit and a current and a voltage due to a reflected wave thereof ;
Based on the detection signal from the first sensor, the frequency of the high-frequency signal output from the high-frequency power source is adjusted by controlling the high-frequency power source so that the plurality of antenna elements approach an impedance matching state. The capacitance of the capacitive element used as the adjustment element of each impedance matching unit by controlling each of the plurality of impedance matching units so that each antenna element is in an impedance matching state based on a detection signal from the second sensor And a controller for controlling the inductance of the inductive element . The adjustment element of each impedance matching unit includes a first capacitive element having one end connected to the distributor and a second capacitive element having one end connected to the antenna element.
The other end of the first capacitive element and the other end of the second capacitive element are both grounded,
Wherein the controller, the plasma generating apparatus according to claim 1 for controlling the capacitance of the first capacitor.   The plasma generation apparatus according to claim 1, wherein the generated plasma is used for film formation of a substrate or etching of a substrate. A plasma generation method for generating plasma using an array antenna in which a plurality of antenna elements each made of a rod-shaped conductor whose surface is covered with a dielectric material are arranged in parallel and in a plane,
Generate high-frequency signals,
The generated high-frequency signal is distributed and supplied to the plurality of antenna elements via a plurality of impedance matching units each having one of a capacitance element and an inductive element for impedance matching,
Detecting the high-frequency signal before distribution and the current and voltage due to the reflected wave ,
Detecting the high-frequency signal distributed and supplied to the plurality of impedance matching units and the current and voltage due to the reflected wave , respectively;
Based on the high-frequency signal before distribution and the detection signal for the reflected wave , the frequency of the high-frequency signal is adjusted so that the plurality of antenna elements approach the impedance matching state and distributed to the plurality of impedance matching units. The capacitance of the capacitive element used as the adjustment element of each impedance matching unit or the induction element so that the plurality of antenna elements are in an impedance matching state based on the high-frequency signal and the detection signal for the reflected wave . A plasma generation method characterized by controlling inductance .

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