JPH1088338A - Arc counting device - Google Patents

Abstract

(57) [Problem] To provide an arc counting device that can be easily attached to a reactive sputtering device and can be realized with a relatively simple configuration. SOLUTION: An arc cutting device 31 for temporarily stopping the cathode current supplied to a target plate 29 abnormally and recovering the cathode current after a predetermined time has elapsed.
And a voltage comparing means for comparing the applied DC voltage applied to the target plate 29 with a settable threshold voltage to detect that the applied DC voltage has exceeded the threshold voltage, wherein the voltage comparing means has the applied DC voltage When it is detected that the voltage has become higher than the voltage, the occurrence of an arc is determined and counted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an arc counting apparatus, and more particularly to an arc counting apparatus for counting arcs generated when a predetermined target material is formed by sputtering on an optical disk surface.

[0002]

2. Description of the Related Art An optical disc is formed by forming a thin film for recording on the surface of a plastic substrate such as glass or polycarbonate resin. In the magneto-optical disk, the recording thin film has a four-layer structure of a dielectric film / magnetic film / dielectric film / reflection film. In a magneto-optical disk having such a structure, the key to manufacturing is to form the first dielectric film at high speed and in a stable manner. As a technique therefor, a method using so-called reactive sputtering is employed. The sputtering method uses a sputtering phenomenon in which when a solid surface is irradiated with accelerated ions, sample atoms near the solid surface obtain part of the energy of the incident ions and are released into a vacuum. In particular, reactive sputtering is a sputtering method in which a kind of chemical reaction is performed together with sputtering to form a compound thin film.

In a reactive sputtering apparatus for performing reactive sputtering, ionized Ar gas is sputtered on a target plate provided on a cathode by glow discharge, and atoms ejected from the target plate react with gas atoms in the sputter gas. This is an apparatus for forming a compound thin film on a substrate provided on an anode. As the reactive sputtering apparatus, two types, a direct current (DC) type and a radio frequency (RF) type, are particularly known depending on the type of voltage for generating a glow discharge. In the DC method, a glow discharge is generated by applying a DC voltage of about several hundred volts between the electrodes. On the other hand, in the RF system, a glow discharge is generated by applying a high frequency voltage of 13.57 MHz between the electrodes. By the way, DC
The method has the advantages that the film formation speed is higher and the internal stress of film formation and the temperature rise of the substrate are small compared to the RF method.

However, the DC method has a problem in that an insulating layer is formed on the surface of the target plate, and this insulating layer causes dielectric breakdown to generate a so-called arc discharge (abnormal discharge). The cause of this arc discharge is that atoms sputtered from the eroded portion on the target to the non-eroded portion and react with the introduced gas to form an insulator. , Positive charges are accumulated by irradiation of positive ions. When a large amount of positive charges are accumulated, dielectric breakdown occurs.

When such dielectric breakdown occurs, the particles emitted from the target become coarse, and so-called spats (coarse particles) having a diameter of several μm are generated on the magneto-optical disk. It is well known that these spats become so-called micro-dropouts, which greatly affect the signal defect characteristics (byte error characteristics) of the magneto-optical disk and deteriorate the quality of the disk.

FIG. 7 shows the relationship between the number of occurrences of arc discharge per unit time during sputtering and the signal defect amount (byte error rate) of the magneto-optical disk. From the figure, it can be seen that the byte error rate has an exponential relationship with the number of occurrences of arc discharge per unit time. For example, Japanese Patent Application No. 6-111260 monitors the abnormal current of the arc discharge in the cathode current, and temporarily detects the occurrence of the abnormal current when the occurrence of the abnormal current is recognized. A method has been adopted in which the peak value of the arc current is reduced so as to prevent the occurrence of spats.

Further, as shown in FIG. 6, there is an arc prevention method called a self-trigger mode method in which a positive pulse voltage of about 2 kHz is superimposed on a cathode voltage which is a negative voltage.
When a positive pulse is superimposed on the cathode voltage in this manner, electrons in the plasma are attracted to the target on the cathode, and the arc can be prevented by neutralizing the positive charges accumulated in the insulating layer in the non-eroded portion of the target. .

However, there are arcs that cannot be completely prevented by such a device. Therefore, in order to manufacture a disk of stable quality, it is essential to efficiently perform maintenance including replacement of a target of a film forming apparatus that can prevent occurrence of arc discharge. It is important to accurately know the number of occurrences of arcs as important information for knowing an appropriate maintenance time such as the target replacement time, and as information for disc quality control. However, conventionally, there is no arc counting device which has a relatively simple structure and can be easily attached to a reactive sputtering device.

[0009]

As described above, it is important to know the number of arc occurrences accurately in order to know the maintenance time for preventing the occurrence of arc discharge, and also to control the quality of the optical disk. However, no arc counting device with a simple configuration that can be easily mounted has not been produced. An object of the present invention is to solve this problem and to realize an arc counting device that can be easily attached to a reactive sputtering device with a relatively simple configuration.

[0010]

To achieve the above object, the present invention relates to an arc counting apparatus used in a DC reactive sputtering apparatus for forming a predetermined target material on a surface of an optical disk by a DC reactive sputtering method. Current control means for temporarily stopping the cathode current when the cathode current supplied to the target plate is abnormally increased and recovering the cathode current after a predetermined time; an applied DC voltage applied to the target plate and a settable threshold value Voltage comparing means for comparing the voltage with the voltage to detect that the applied DC voltage has exceeded the threshold voltage, and detecting the arc when the voltage comparing means detects that the applied DC voltage has exceeded the threshold voltage. It is characterized by occurrence and counting.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an arc counting device according to the present invention will be described in detail with reference to the accompanying drawings. FIG.
1 is a layout diagram showing a configuration of a film forming system for a magneto-optical disk to which the present invention is applied. The operation of the film forming system for a magneto-optical disk and the configuration of the present invention will be described with reference to FIG.
The substrate disk 8 before film formation is transported from the heat treatment chamber 7 to the dry clean room 10 and the inner mask and the outer mask are palletized by the disk attaching / detaching robot 3.
Attached to.

The pallet 4 on which the substrate disk 8 before film formation is mounted moves on a belt and is carried into the vacuum chamber of the charging chamber 11 so that both the pallet 4 and the substrate disk 8 are evacuated. Vacuum degassing of the substrate disk 8 is performed. The substrate disk 8 on the pallet 4 thus degassed is now in a film forming process.

In the film forming process, a dielectric film, a magnetic film and a dielectric film are formed on the substrate disk 8 by sputtering in four independent vacuum chambers 13-1 to 13-4 in the sputtering chamber 13.
The formation of the dielectric film and the reflection film is performed in this order. The film-forming disk 9 on which film formation has been completed through this film-forming step is taken out into the atmosphere in the take-out chamber 14, transported again to the dry clean room 10, removed from the pallet 4 by the disk attaching / detaching robot 3, and going to the next step. It comes to head. It is to be noted that the numeral 15 shown in the figure is the arc counting device of the present invention. This will be described later in detail.

Next, the sputtering performed in the film forming process will be specifically described. In general, the sputtering apparatus has a configuration as shown in FIG. 2 and includes a vacuum chamber 21 and a vacuum controller 2 for controlling a vacuum state in the vacuum chamber 21.
2, a high-voltage power supply 23 for plasma discharge, and a cathode 25 connected to the high-voltage power supply 23 and a power supply line 24.
And an anode 26 arranged opposite to the cathode 25 at a predetermined distance, and a sputtering gas supply unit 27 for supplying Ar gas or the like as a sputtering gas into the vacuum chamber 21. Further, the cathode 25
Has a target plate 29 made of Si or the like functioning as a negative electrode.
And a backing plate 30 for fixing the target plate 29.

To use this sputtering apparatus,
First, the inside of the vacuum chamber 21 is set to a sufficiently good vacuum state, for example, about 1 × 10 −4 Pa by the vacuum controller 22. Next, a sputtering gas, for example, Ar + N2 is introduced into the vacuum chamber 21 from the sputtering gas supply unit 27 until a predetermined pressure is reached. In this state, the target plate 29 is
Is applied with a predetermined negative potential. Then, an electric field is generated between the target plate 29 and the anode 26 constituting a pair of electrodes, and a glow discharge occurs, whereby the ionized Ar gas collides with the target plate 29. As a result, the target material Si is sputtered out of the target plate 29 in an atomic state, and the target material is deposited on the transparent substrate 28 of the magneto-optical disk provided on the anode disposed opposite to the target plate 29. Accumulate while reacting with N2,
A dielectric thin film made of SiN is formed on the transparent substrate 28.

By the way, as shown in FIG. 3, an insulating layer made of SiN is also formed on the edge portion of the target plate 29 and the like during the sputtering, and this insulating layer causes dielectric breakdown to generate a so-called arc (abnormal discharge). May be. As described above, by observing the number of occurrences of the arc, the quality of the magneto-optical disk can be controlled, and the necessity of maintenance of the apparatus including replacement of the target plate 29 can be determined.

The arc counting device of the present invention counts the number of times such an arc is generated. First, the operation principle of the arc counting device will be described. In the present invention, as shown in FIG. 2, an arc cutting device 31 is provided on a power supply line 24 connecting a high-voltage power supply 23 and a cathode 25. FIG. 4 shows the potential of the cathode 25 during sputtering. When no arc is generated due to good sputtering, a constant cathode current of about 7 A flows,
The cathode voltage is kept at about -550 V in the case of a Si target. However, when arc discharge occurs, the cathode current increases to about 100 A at the peak value. The arc cut device 31 detects the abnormality of the current, and when detecting an increase in the current, temporarily shuts off the cathode current, returns the cathode current after a predetermined time, and stops the continuation of the arc. At this time, the cathode voltage stops the application of the negative voltage to the cathode 25 by the operation of the arc cut device 31, so that the cathode potential rapidly rises to near 0V. The arc counting device of the present invention monitors this cathode potential, determines that an arc discharge has occurred when the cathode potential rises above a certain set voltage, and counts this time.

FIG. 5 is a block diagram showing the configuration of the arc counting device of the present invention. In FIG. 5, 101 is a cathode electrode of a sputtering apparatus, 102 is a connector, 103
Is an amplifier, 104 is an arc detection circuit, 105 is an arc detection level adjustment volume, 106 is a self-trigger mask circuit, 107 is a self-trigger mask changeover switch, 108 is a trigger adjustment volume, 109 is a low-pass filter, and 110 is a high-pass filter. Filtering filter, 111 is an arc width adjustment volume, 112 is a filter selection circuit, 11
3 is an arc changeover switch, 114 is a cumulative counter, 1
15 is a rate counter, 116 is a counter selection circuit, 1
17 is a display changeover switch, 118 is a display, and 119 is a counter reset switch.

The potential signal of the cathode electrode 101 is amplified by an amplifier 103 via a connector 102 and is input to an arc detection circuit 104. The arc detection circuit 104 has a comparison circuit, compares the cathode potential with a certain threshold voltage as needed, and generates a pulse signal while the cathode potential exceeds the threshold voltage. The threshold voltage used at this time can be arbitrarily adjusted by the arc detection level adjustment volume 105. The pulse signal generated by the arc detection circuit 104 is input to the self-trigger mask circuit 106. Here, the operation of the self-trigger mask circuit 106 will be described.

The sputtering apparatus according to the present invention employs an arc prevention method in which a positive pulse voltage of about 2 kHz is superimposed on a cathode voltage as shown in FIG. 6 as a self-trigger mode. This causes electrons in the plasma to be attracted to the target on the cathode by superimposing a positive pulse on the cathode voltage,
The arc is prevented by neutralizing the electrons with the positive charges accumulated in the insulating layer in the non-eroded portion of the target.

However, when the sputtering operation is performed in the self-trigger mode, the cathode voltage is reduced as shown in FIG.
Therefore, the positive pulse portion may be detected as an arc and counted. The self-trigger mask circuit 106 has a function of masking the positive pulse to prevent counting as an arc. Self trigger function changeover switch 10
7 controls the selection of the self-trigger mode and the operation of the self-trigger mask circuit 106 at the same time. The trigger adjustment volume 108 has a function of adjusting the mask area in accordance with the trigger width.

The output signal of the self-trigger mask circuit 106 is directly or after passing through the low-pass filter 109 or the high-pass filter 110,
12 is selected by switching of the arc switch 113. The filters 109 and 110, the filter selection circuit 112, and the arc switch 11
The function of 3 is to select the arc to be counted.

That is, whether to count when a pulse corresponding to the time width set by the arc width adjustment volume 111 arrives or to count all the pulses regardless of the time width of the pulse is selected by the arc switch 113. By selecting this function, a large arc (hard arc), a small arc (micro arc), and the like can be selected and counted. The method of selecting the time width of the pulse is performed by changing the time constant of the low-pass filter 109 or the high-pass filter 110 using the arc width adjustment volume 111.

By distinguishing the hard arc and the micro arc in this manner, the quality of the formed magneto-optical disk can be known more accurately. If a hard arc is generated even once during film formation, the quality of the disc is determined to be poor. However, if a micro arc is generated a plurality of times, the quality is not significantly affected. Therefore, the process feedback on the disc quality becomes quicker, for example, if hard arc occurs frequently, a method of stopping the production and responding to it is adopted, and the micro arc is gradually increasing with time. In such a case, it is determined that the film formation state has deteriorated, and a countermeasure is taken. The contents of the correspondence may be replacement of the target plate, change of the film forming conditions, and the like.

The output signal of the selection circuit 112 is input to the accumulation counter 114 and the rate counter 115. The accumulation counter 114 indicates the number of arcs (or time width).
, And the rate counter 115 counts the number of arcs (or time widths) per unit time.
Whether the output of the accumulation counter 114 is selected and displayed or the output of the rate counter 115 is selected and displayed is determined by the designation of the display changeover switch 117.
6 is performed, and the counter output of the selected side is displayed on the display 11.
8 is displayed. Also, the counter reset switch 11
By turning on 9, the arc count number can be set to 0 at any time.

With the arc counting apparatus described above, the arc discharge generated in the sputtering process during the production of the magneto-optical disk can be accurately counted. The arc counting apparatus according to the present invention comprises vacuum chambers 13-1 and 1 for sputtering a dielectric film in which an arc is generated.
It is desirable to attach them as shown in FIG. 1 as 15-1 and 15-2 in 3-3, respectively. This is to separately grasp the state of arc generation in each vacuum chamber. Also, in order to avoid signal attenuation and the influence of noise, the length of the cable connecting the cathode electrode and the arc counting device of the present invention should be within 1 m, as close as possible to the respective vacuum chambers 13-1 and 13-3. It is desirable to be installed. In the vacuum chamber 13-2 for forming a magnetic film and the vacuum chamber 13-4 for forming a reflective film, an insulating layer is not formed on the target plate and, therefore, no arc is generated.

As described above, according to the present invention, when the arc cut device 31 detects an abnormality of the cathode current, the cathode current is temporarily cut off, and the increase in the cathode voltage caused by the cathode current is counted by the arc counting device of the present invention. I have. Therefore, since the circuit can be easily connected to an existing device and a circuit can be formed only by comparing and detecting the voltage, the device configuration is relatively simple, and an arc counting device capable of accurately detecting the number of arc occurrences is realized. be able to.

[0028]

As described above, the invention of claim 1 of the present invention relates to an arc counting apparatus used in a DC reactive sputtering apparatus for forming a predetermined target material on an optical disk surface by a DC reactive sputtering method. Current control means for temporarily stopping the cathode current supplied to the target plate when the cathode current is abnormally increased and recovering the cathode current after a predetermined time; an applied DC voltage applied to the target plate and a settable threshold voltage And a voltage comparing means for detecting that the applied DC voltage has exceeded the threshold voltage.When the voltage comparing means detects that the applied DC voltage has exceeded the threshold voltage, it is determined that an arc has occurred. Counting. As a result, an arc counting device that can be easily connected to an existing reactive sputtering device, has a relatively simple device configuration, and can accurately detect the number of arc occurrences can be realized at low cost.

According to a second aspect of the present invention, there is provided an arc time width measuring means for measuring, as an arc time width, a detection time width in which the voltage comparing means detects that the applied DC voltage has exceeded the threshold voltage. The method is characterized in that arcs are classified according to the arc time width measured by the time width measuring means.
Thus, arcs can be classified based on the duration of the arcs, and the number of arcs can be counted for each classified arc type. Based on this, it is possible to know the tendency and the cause of arc generation, which can be used for maintenance work such as disc quality judgment and target plate replacement.

The invention according to a third aspect of the present invention is characterized in that the invention comprises mask circuit means for removing the effect of a low-frequency pulse superimposed on the applied DC voltage from the output of the voltage comparison means. Thus, even when a pulse is automatically generated in the self-trigger mode to prevent the occurrence of an arc, the pulse can be prevented from being mistakenly regarded as an arc and counted.

[Brief description of the drawings]

FIG. 1 is a layout diagram showing a configuration of a film forming system for a magneto-optical disk to which the present invention is applied.

FIG. 2 is a configuration diagram of a sputtering apparatus in which the present invention is used.

FIG. 3 is an explanatory diagram showing a deposition state of an insulating layer generated at an edge portion of a target plate.

FIG. 4 is an explanatory diagram showing a potential of a cathode during sputtering.

FIG. 5 is a block diagram showing a configuration of an embodiment of an arc counting device of the present invention.

FIG. 6 is an explanatory diagram showing a cathode voltage and a cathode current in a self-trigger mode.

FIG. 7 is an explanatory diagram showing the relationship between the number of occurrences of arc discharge per unit time during sputtering and the amount of signal defects in a magneto-optical disk.

[Explanation of symbols]

3 ... Disk loading / unloading robot, 4 ... Pallet, 7 ...
Heat treatment room, 8: substrate disk, 10: dry clean room, 11: preparation room, 12: degassing room, 13 ...
... Sputter chamber, 13-1 to 13-4 ... Vacuum chamber, 14
...... Removal chamber, 15-1, 15-2 ... Arc counting device, 21 ... Vacuum chamber, 22 ... Vacuum controller,
23 high-voltage power supply, 24 power supply line, 25 cathode, 26 anode, 27 sputtering gas supply unit, 28 transparent substrate 29 target plate 30,
... backing plate, 31 ... arc cutting device, 1
01 ... cathode electrode, 102 ... connector, 103 ...
·················································································································
…… Low-pass filter, 110 …… High-pass filter,
111: Arc width adjustment volume 112: Filter selection circuit 113: Arc changeover switch 114
... Cumulative counter, 115 ... Rate counter, 116
... Counter selection circuit, 117, display changeover switch, 118, display, 119, counter reset switch.

Claims (3)

[Claims] 1. An arc counting device used in a DC reactive sputtering apparatus for forming a predetermined target material on a surface of an optical disk by a DC reactive sputtering method, when an abnormal increase in a cathode current supplied to a target plate occurs. Current control means for temporarily stopping the cathode current and recovering it after a predetermined time; and comparing the applied DC voltage applied to the target plate with a settable threshold voltage, wherein the applied DC voltage exceeds the threshold voltage. An arc counting device, comprising: a voltage comparing means for detecting that the applied DC voltage has exceeded the threshold voltage; determining that an arc has occurred; and counting the arc. . 2. An arc time width measuring means for measuring, as an arc time width, a detection time width in which the voltage comparing means detects that the applied DC voltage exceeds the threshold voltage, wherein the arc time width measuring means 2. The arc counting device according to claim 1, wherein arcs are classified according to the arc time width measured by the counter. 3. An arc counting apparatus according to claim 1, further comprising a mask circuit for removing an influence of a low-frequency pulse superimposed on the applied DC voltage from an output of the voltage comparison means. .