JP2002266067A - Evaporation source system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an evaporation source system which is capable of preventing a thin film forming material from spilling from a boat. SOLUTION: This evaporation source system has a pair of electrode members 7A and 7B disposed in a vacuum chamber 2, the boat 8 for housing the thin film forming material 9 spanned between the pair of the electrode members 7A and 7B and a power source 30 for heating to supply current I for heating through the pair of the electrode members 7A and 7B to the boat 8. The power source 30 for heating is composed of an inverter 11 which outputs the current I for heating controlled of magnitude by a PWM.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an evaporation source device used in a vacuum film forming apparatus, and more particularly to an evaporation source device of a resistance heating type.

[0002]

2. Description of the Related Art In a vacuum film forming apparatus, a thin film forming material (drug) is evaporated from an evaporation source in a vacuum chamber, and the evaporated thin film forming material is deposited on a substrate placed in the vacuum chamber. Thus, a thin film made of a thin film forming material is formed on the base material.

[0003] In some products, a thin film made of a high melting point metal such as tantalum is deposited on a substrate. In such a case, a method of evaporating a thin film forming material by an electron gun has been adopted as an evaporation source.

However, the use of an electron gun increases the cost of the evaporation source, and in order to reduce the cost of the evaporation source, the resistance heating method, which is low in cost and exclusively used for depositing a low melting point metal, has begun to be adopted. Was.

In the resistance heating method, a thin film forming material is placed on a heating vessel called a boat which is stretched between a pair of electrodes and is open at the top, and the boat is heated by a heating power supply through the electrodes. By doing so, the thin film forming material is evaporated.

However, a large current is required to evaporate a high melting point thin film forming material by a resistance heating method.
Therefore, an alternating current, not a direct current, is used as a heating power supply. Further, the deposition rate in vacuum deposition depends on the evaporation rate of the thin film forming material from the evaporation source. On the other hand, in vacuum film formation, the film formation speed has a great effect on the quality of a thin film formed on a substrate. Therefore, in vacuum film formation, the film formation speed is controlled to be kept constant. The control of the film forming speed is performed by detecting the film thickness of the thin film formed on the base material by a film thickness sensor, and performing feedback control of the boat heating current based on the detected film thickness value.
Therefore, in order to stably perform the feedback control, the heating power supply needs to have a high-speed response in adjusting the current value. From this point of view, the heating power supply does not employ a slow response method of current adjustment, such as the Slidak method, but employs a phase control method using a semiconductor switching element having a fast response time of current adjustment. .

[0007]

However, this phase control method has a problem that the thin film forming material placed on the boat spills. In general, in vacuum film formation, the final thickness of a thin film formed on a substrate is adjusted by the amount of the thin film forming material placed on a boat. Cannot be set to the desired thickness. In particular, when the film thickness is small, the accuracy of the film thickness decreases. Therefore, this problem is significant.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to provide an evaporation source device capable of preventing a thin film forming material from spilling from a boat.

[0009]

Means for Solving the Problems In order to solve the above problems, the present inventor has worked on investigation of the cause of boat vibration. As a result, the following facts became clear.

That is, as shown in FIG.
Is formed of a metal plate-like member having a central portion formed in a boat shape as a storage portion for a thin film forming material, and both end portions formed in a flat plate shape as fixing portions to the electrodes 7A and 7B. Since the boat 8 configured as described above has elasticity, when both ends are fixed to the electrodes 7A and 7B, a vibration system is formed and the boat 8 easily vibrates. According to experiments, the resonance frequencies of the boat were approximately 300 Hz and 600 Hz.

The heating power supply of the phase control system uses a thyristor-based power regulator to control the phase of a sine wave current of a commercial power supply (see FIG. 4A) and chopping the same. Since the current is obtained (see FIG. 4 (b)),
The waveform of the heating current is not smooth. Therefore, vibration is easily generated. In addition, since many harmonics are included, resonance easily occurs.

From the above facts, the inventor of the present invention has presumed that the vibration of the boat is caused by the vibration of the boat caused by the heating current having a non-smooth waveform, and the amplitude thereof is amplified by resonance. Therefore, the waveform of the heating current is
An experiment was conducted to compare the vibration of the boat by changing the current one, the sine wave, and the flat DC, and found that the boat hardly vibrated in the case of the sine wave and the flat DC. This confirmed the above assumption.

However, the power supply for heating is required to have a high responsiveness with respect to the adjustment of the current for heating in order to keep the film forming rate constant.

Therefore, an evaporation source device according to the present invention accommodates a pair of electrode members provided in a chamber for performing vacuum film formation and a thin film forming material which is bridged between the pair of electrode members. A boat, and a heating power supply for supplying a heating current to the boat through the pair of electrode members, the heating power supply including an inverter for outputting the heating current whose size is controlled by PWM. (Claim 1).

According to this configuration, according to the PWM, the signal wave in the gate control circuit of the switching element constituting the inverter is a sine wave, so that the waveform of the heating current to be output becomes a sine wave, and the harmonic wave is reduced. It is almost not included. As a result, it is possible to prevent the boat from vibrating, thereby preventing the thin film forming material from spilling from the boat. Further, since the heating power supply is constituted by an inverter, the heating current can be adjusted in response to the current at high speed.

In this case, the inverter of the heating power supply may be capable of controlling the frequency of the heating current by PWM.

With this configuration, even if the output heating current contains some harmonic components due to distortion or the like, the frequency is adjusted to match the frequency and the harmonics with the boat resonance frequency. By controlling the boat not to vibrate, vibration of the boat can be prevented.

In this case, vibration detection means for detecting the vibration of the boat, frequency analysis means for obtaining a main frequency component of the vibration detected by the vibration detection means, and main frequency information obtained by the frequency analysis means Frequency control means for controlling the frequency of the heating current so that the frequency of the component is not included as the frequencies of the fundamental wave and the harmonics of the heating current output from the inverter may be provided. ).

With this configuration, the resonance of the boat due to the vibration caused by the heating current is avoided by the frequency control means, so that the vibration of the boat can be automatically prevented.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. Embodiment 1 FIG. 1 is a schematic diagram showing a configuration of a vacuum film forming apparatus using an evaporation source device according to Embodiment 1 of the present invention. FIG. It is a diagram showing a control process, (a) is a diagram showing a signal wave and a carrier wave, (b) is a diagram showing the output voltage of the inverter and its average instantaneous value, (c)
FIG. 8 is a diagram showing the signal wave and the carrier wave when the amplitude of the signal wave is small, and FIG. 9D is a diagram showing the output voltage of the inverter and the average instantaneous value thereof when the amplitude of the signal wave is small. Vacuum film formation includes ordinary vapor deposition, sputtering, ion plating, and the like. In this embodiment, an ion plating apparatus is exemplified as a vacuum film formation apparatus.

In FIG. 1, a vacuum film forming apparatus 1 has a vacuum chamber 2 made of a conductive member. In the vacuum chamber 2, a base material holder 3 for holding a base material is provided. The substrate holder 3 is made of a conductive member, and is connected to one end of a rotating shaft 4 made of the conductive member. Rotary axis 4
The other end is connected to the motor 5 and is rotatably held on the wall of the vacuum chamber 2. The rotating shaft 4, the motor 5, and the vacuum chamber 2 are insulated by an insulating member (not shown). A high frequency power supply 22 and a DC power supply 23 are connected in parallel to a portion of the rotary shaft 4 outside the chamber via a slip ring and a brush (not shown). Between the high-frequency power supply 22 and the DC power supply 23 and the rotating shaft 4,
A DC blocking capacitor C0, a matching circuit 21, and an AC blocking choke coil L0 are interposed. The matching circuit 21 automatically performs impedance matching between the high-frequency power supply 22 and the load. The other ends of the high frequency power supply 22 and the DC power supply 23 are connected to the vacuum chamber 2, and the vacuum chamber 2 is grounded. Further, the DC power supply 23 is connected such that the substrate holder 3 side is negative.

On the other hand, an evaporation source 6 is provided in the vacuum chamber 2 so as to face the substrate holder 3. The evaporation source 6 comprises a pair of electrodes 7 erected on the lower wall of the vacuum chamber 2.
A boat 8 is bridged between A and 7B. A thin film forming material 9 is placed on the boat 8. A heating power supply 30 arranged outside the vacuum chamber 2 is connected between the pair of electrodes 7A and 7B. The evaporation source 6 and the heating power supply 30 constitute an evaporation source device 31.

The heating power supply 30 includes a rectifier 12, an inverter 1
1, gate control circuit 13, current sensor 14, and transformer 10
Is a main component.

The rectifier 12 has a known structure, and rectifies a three-phase alternating current of a commercial power supply to output a predetermined DC voltage E. The inverter 11 has a well-known structure, and has a PWM (pulse wid
The DC voltage E output from the rectifier 12 is converted into a predetermined AC voltage e by th modulation) and output. The gate control circuit 13 generates a gate signal of a switching element of the inverter 11. The transformer 10 reduces the AC voltage output from the inverter 11 to a predetermined voltage at a turns ratio a.

Next, the inverter 11 and the gate control circuit 13
Will be described in detail. The inverter 11 includes a rectifier that includes a circuit including a first switching element S1 and a second switching element S2 connected in series and a circuit including a third switching element S3 and a fourth switching element S4 connected in series. Twelve output terminals are connected in parallel, and a connection point between two switching elements of both circuits is connected to a primary terminal of the transformer 10. A diode D for bypassing the delay current is connected in parallel to each of the switching elements S1 to S4. The switching elements S1 to S4 are IGBT (Insulsted Gate) here.
Bipolar Transister), Power MOSFET (Power Meta
l Oxide Semiconductor Field Effect Transister). Control signals g1 to g4 are input from the gate control circuit 13 to the gates of the switching elements S1 to S4.

Referring to FIGS. 1 and 2 (a), the gate control circuit 13 converts the internally generated sine wave signal wave Sc and triangular carrier wave C into a gate control signal g as follows.
Generate 1 to g4.

That is, in the positive half cycle of the signal wave Sc, the first switching element S1 is turned on over the entire period, and the fourth switching element S1 is turned on over the period t1 when the signal wave Sc is larger than the carrier wave C. During a period t2 when S4 is on and the signal wave Sc is smaller than the carrier wave C, the third
Is turned on, and in the negative half cycle of the signal wave Sc, the third switching element S3 is turned on over the entire period, and the signal wave Sc is turned on.
Are switched on over a period t3 during which the signal wave Sc is smaller than the carrier wave C, and the first switching element S1 is turned on over a period t4 when the signal wave Sc is larger than the carrier wave C. Fourth switching element S1 ~
Control signals g1 to g4 are output to the gate of S4. Then
In the period t1, the first and fourth switching elements S1 and S4 are turned on, so that a constant voltage E is output to the primary terminal of the transformer 10. In the period t2, the second and fourth switching elements S2 and S4 are turned on. Since both are turned off, no voltage is output to the primary terminal of the transformer 10. On the other hand, in the period t3, the third and second switching elements S3 and S2 are turned on, so that a negative constant voltage E is output to the primary terminal of the transformer 10, and in the period t4, the second and fourth switching elements S3 and S2 are turned on. Since both S2 and S4 are turned off, no voltage is output to the primary terminal of the transformer 10.

Therefore, as shown in FIG. 2B, an AC voltage e composed of a train of rectangular pulses whose width is approximately proportional to the value of the signal wave Sc is output to the primary terminal of the transformer 10. You. The average instantaneous value V 'of the AC voltage e becomes a sine wave. The AC voltage e is integrated by the electromagnetic induction of the transformer 10, and becomes a sine wave on the secondary side, like the average instantaneous value V '. Accordingly, a sine wave AC voltage V obtained by reducing the average instantaneous value V ′ at a predetermined turns ratio a is output to the secondary side of the transformer 10. The magnitude (amplitude) of the secondary voltage V (and therefore also V ') of the transformer 10 is, as is apparent from FIGS. 2C and 2D, the magnitude (amplitude) of the signal wave Sc. It will be proportional. The frequency is the same as the frequency of the signal wave Sc. Also, transformer 1
Since the secondary load of 0 is a boat which is a resistive load, the heating current I as the secondary current is a sine wave having substantially the same phase as the secondary voltage V. Therefore, by controlling the amplitude and frequency of the signal wave Sc generated by the gate control circuit 13, the magnitude and frequency of the heating current I can be controlled to desired values. A current sensor 14 is interposed on the output side of the inverter 11, and a gate control circuit 13
Is a heating current I based on a current value input from the current sensor 14 and an amplitude command value of a signal wave input from the outside.
(The output current of the inverter 11) is feedback-controlled. In the present embodiment, the frequency of the carrier C is 10 KHz. The effective value of the voltage of the commercial power supply and the output voltage e of the inverter 11 is 200 V, and the secondary voltage V of the transformer 10 is 10 V.
V. Therefore, the turns ratio a of the transformer 10 is 20.
The heating current is set in the range of 500A to 1000A.

Further, although not shown, a film thickness sensor for detecting the film thickness of the thin film formed on the base material held by the base material holder 3 is provided at an appropriate position, and the detection output is provided by a gate control circuit. The gate control circuit 13 is configured to feedback-control the heating current I based on the detected film thickness value.

Next, the operation of the vacuum film forming apparatus and the evaporation source apparatus configured as described above will be described.

In FIG. 1, it is assumed that the resonance frequency of the boat 8 bridged between the pair of electrodes 7A and 7B is 300 Hz and 600 Hz. In this case, the resonance frequency is equal to the frequency of the fifth harmonic and the tenth harmonic of the distorted wave whose fundamental frequency is 60 Hz. Therefore, the operator sets the frequency command value of the signal wave to the gate control circuit 13 at, for example, 70 Hz. Further, since the thin film forming material is a high melting point metal, the amplitude command value of the signal
The value is set so as to be 00A.

In this state, the substrate is placed on the substrate holder 3 and a required amount of the thin film forming material 9 is placed on the boat 8.

Next, when the vacuum film forming apparatus 1 is started, the plasma rises in the vacuum chamber 2 by the high frequency power applied by the high frequency power supply 22, and a DC electric field from the vacuum chamber 2 to the substrate holder 3 is generated by the DC power supply 23. It is formed. Then, a heating current I is supplied from the heating power supply 30 to the boat 8, and the boat 8 is energized and heated, whereby the high-melting-point thin-film forming material 9 placed on the boat 8 evaporates. Then, the evaporated thin film forming material becomes
It is excited by the plasma and accelerated by the DC electric field, and collides and adheres to the surface of the substrate held by the substrate holder 3. Thereby, a thin film made of the thin film forming material 9 is formed on the base material.

At this time, a sine-wave heating current I is supplied from the heating power supply 30 to the boat 9, so that the heating current I
Have almost no harmonics. Also,
Even if the waveform includes some harmonics due to the distortion of the waveform, the frequency of the harmonic closest to the resonance frequency of the boat 8 is
280Hz and 630Hz, the resonance frequency of boat 8 is 300Hz
And 600Hz. Therefore, even when the heating current I is as large as 1000 A, the boat 8 can be prevented from vibrating. As a result, the thin film forming material 9
Spilling from the boat 8 can be prevented.
Further, since the current control device of the heating power supply 30 is constituted by the inverter 11, the output current is adjusted by feedback control with a high-speed response. Control is performed stably. Embodiment 2 FIG. 3 is a schematic diagram showing a configuration of a vacuum film forming apparatus according to Embodiment 2 of the present invention. In the present embodiment, the evaporation source device 30
Further includes, in addition to the configuration of the first embodiment, a vibration sensor 29 attached to the tip of the electrode 7A, and a frequency analysis device 32 for obtaining a main frequency component of vibration detected by the vibration sensor 29, that is, a resonance frequency. A frequency control device 33 is provided that inputs a frequency command value of a signal wave to the gate control circuit 13 as a control signal based on the main frequency components obtained by the frequency analysis device 32. The vibration sensor 29 includes, for example, an acceleration sensor and a speed sensor. The frequency analyzer 32 is constituted by, for example, an FFT (Fast Fourier Transform) analyzer. The frequency control device 33 is composed of, for example, a CPU. Here, according to the experiment performed by the inventor, the resonance frequency of the boat 8 is approximately in the range of 100 Hz to 700 Hz, and the number thereof is at most about three. A table is created in which a frequency having a certain range is associated with a frequency (hereinafter referred to as a resonance avoidance frequency) that does not include the frequency having the range as a fundamental frequency and a harmonic frequency. It is possible. Therefore, in the present embodiment, the frequency control device 33 stores such a table in the main memory in advance, compares the main frequency obtained by the frequency analysis device 32 with the table, and obtains the table. The generated resonance avoidance frequency is output to the gate control circuit 33 as a frequency command value.

According to such a configuration, even if the boat 8 resonates with the vibration caused by the heating current I, the vibration sensor 29
Detects the vibration, the frequency analysis device 32 determines a main frequency component of the detected vibration, and a frequency that does not include the determined frequency of the main frequency component as the frequency of the fundamental wave and the harmonic. Is output from the frequency control device 33 to the gate control circuit 33 as a frequency command value. Thereby, the frequency of the heating current I changes to such a frequency, and the resonance of the boat 8 is automatically prevented.

Although the voltage type inverter is used in the first and second embodiments, a current type inverter may be used.

Further, in the first and second embodiments, the case where the evaporation source device is used for the ion plating device has been described. However, other vacuum film forming devices such as a normal vapor deposition device and a sputtering device are similarly used. Can be used.

[0038]

The present invention is embodied in the form described above and has the following effects. (1) The vibration of the boat can be prevented, whereby the material for forming the thin film can be prevented from spilling from the boat. Further, since the heating power supply is constituted by an inverter, the heating current can be adjusted in response to the current at high speed. (2) Assuming that the inverter of the heating power supply can control the frequency of the heating current by PWM,
Even if the output heating current contains some harmonic components due to distortion or the like, by controlling the frequency so that the frequency and the harmonic do not match the resonance frequency of the boat, The vibration of the boat can be prevented. (3) Vibration detection means for detecting the vibration of the boat, frequency analysis means for obtaining the main frequency components of the vibration detected by the vibration detection means, and the frequency of the main frequency component obtained by the frequency analysis means from the inverter. If a control means for controlling the frequency of the heating current so as not to be included in the frequency of the fundamental wave and the harmonics of the heating current to be output is provided, the vibration of the boat can be automatically prevented.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a configuration of a vacuum film forming apparatus using an evaporation source device according to Embodiment 1 of the present invention.

FIGS. 2A and 2B are diagrams showing a voltage control process by PWM of a heating power supply of the evaporation source device of FIG. 1, wherein FIG. 2A shows a signal wave and a carrier wave, and FIG. (C) is a diagram showing the signal wave and the carrier wave when the amplitude of the signal wave is small, (d) is an output voltage of the inverter when the amplitude of the signal wave is small and its average instantaneous value FIG.

FIG. 3 is a schematic diagram showing a configuration of a vacuum film forming apparatus using an evaporation source device according to Embodiment 2 of the present invention.

4A and 4B are diagrams showing a current control process of a conventional heating power supply of an evaporation source, wherein FIG. 4A is a diagram showing a waveform of an input current, and FIG. 4B is a diagram showing a waveform of an output current.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vacuum film-forming apparatus 2 Vacuum chamber 3 Substrate holder 4 Rotating shaft 5 Motor 6 Evaporation source 7A, 7B electrode 8 Boat 9 Thin film forming material 10 Transformer 11 Inverter 12 Rectifier 13 Gate control circuit 14 Current sensor 21 Matching circuit 22 High frequency power supply 23 DC power supply 29 Vibration sensor 30 Heating power supply 31 Evaporation source device 32 Frequency analysis device 33 Frequency control device C Carrier wave Sc Signal wave C0 AC blocking capacitor E Rectifier output voltage e Inverter output voltage g1 to g4 Gate signal I Heating current L0 DC blocking choke coil S1 to S4 Switching element V Secondary voltage of transformer V 'Average instantaneous value of output voltage of inverter

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Takanori Hori 6-107 Takino-cho, Nishinomiya-shi, Hyogo Inside Shin-Meiwa Industry Development Center (72) Inventor Takeshi Furusuka 6 Takino-cho, Nishinomiya-shi, Hyogo No. 107 Shinmeiwa Industry Co., Ltd. Development Center (72) Inventor Koichi Nose 6 107 Takinocho, Nishinomiya City, Hyogo Prefecture Shinmeiwa Industry Co., Ltd. Development Center F term (reference) 3K058 AA00 BA00 CA04 CA12 CA23 CB07 CB22 4K029 CA01 DB03 DB11 DB18 EA09 4M104 DD34 HH20 5F103 AA01 BB02 RR01 RR02 RR08

Claims (3)

[Claims] 1. A pair of electrode members disposed in a chamber for performing vacuum film formation, a boat that is bridged between the pair of electrode members and stores a thin film forming material, An evaporation source device comprising: a heating power supply that supplies a heating current through an electrode member; and the heating power supply is configured by an inverter that outputs the heating current whose size is controlled by PWM. 2. An inverter for a heating power supply, comprising:
2. The evaporation source device according to claim 1, wherein the frequency of the heating current can be controlled by the heating device. 3. A vibration detecting means for detecting vibration of the boat, a frequency analyzing means for obtaining a main frequency component of the vibration detected by the vibration detecting means, and a main frequency component obtained by the frequency analyzing means. 3. A frequency control means for controlling the frequency of the heating current so that the frequency of the heating current is not included as the fundamental and harmonic frequencies of the heating current output from the inverter.
The evaporation source device as described in the above.