JP2574066C - - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic attraction device for attracting a substrate by electrostatic attraction. 2. Description of the Related Art In recent years, in semiconductor manufacturing, a substrate is often fixed using an electrostatic suction device, and a process such as etching is often performed. That is, since the fixing of the substrate is performed by the electrostatic attraction force, it may be difficult to separate the substrate from the electrode due to the residual charge, and it is required to quickly separate the substrate. Therefore, it is necessary to reduce the residual charge on the substrate. 2. Description of the Related Art Conventionally, an electrostatic chuck in a semiconductor manufacturing method applies a high voltage from a DC power supply to an electrode of an electrostatic chuck in which an electrode is included in an insulator, and a substrate mounted on the electrostatic chuck. The substrate is electrostatically attracted by the Coulomb force generated between them. By the way, when a high voltage is applied to the electrode for a long time and the electric charge accumulates on the substrate, even if the application of the voltage to the electrode is stopped, the induced electric charge remains in the substrate, and the substrate is absorbed only by the residual electric charge. Maintain state. In particular, this phenomenon is likely to occur when the insulator for the electrostatic check is used as an alumina cerax and heated to a high temperature by etching or the like. Such a residual charge is spontaneously discharged by leaving it for a long time, but as a method of forcibly discharging the residual charge, when the substrate is separated from the electrostatic chuck, the alternating voltage is gradually reduced after the application of the high voltage is stopped. It has been attempted to apply the voltage while reducing it. However, it is not preferable during the manufacturing process to allow the residual charge to be spontaneously discharged after being left for a long time, and even when an alternating voltage is applied, a large amount of charge is generated by applying a high voltage. Since the residual charge is stored in the substrate, it is difficult to discharge the residual charge, and it is difficult to separate the substrate. Therefore, when the substrate on the electrostatic chuck is to be separated by lift pins or the like, there is a problem that the substrate may be subjected to excessive stress and may be damaged. In view of the above, an object of the present invention is to provide an electrostatic attraction device that suppresses generation of residual charges and facilitates substrate separation. Means for Solving the Problems The object is to provide an electrostatic chuck for adsorbing a substrate on an insulating member containing electrodes,
A DC power supply for applying a predetermined voltage to the electrodes of the electrostatic chuck; a first voltage for applying a first voltage from the DC power supply when the substrate is attracted to the electrostatic chuck; And a voltage control unit for applying a second voltage lower than the voltage of the DC power supply from the DC power supply and stopping the voltage application from the DC power supply when the substrate is separated from the electrostatic chuck. Is done. As described above, when the substrate is sucked on the electrostatic chuck by the DC power supply, a high voltage is applied at the time of suction by the voltage control unit, and after the suction, the voltage is reduced to the voltage value held and held. As a result, unnecessary chucking force is not generated in the electrostatic chuck,
When the application of the voltage is stopped after the predetermined processing, it is possible to minimize the generation of residual charges. Therefore, it is possible to avoid a situation in which the substrate is broken when the substrate is separated from the electrostatic chuck. FIG. 1 shows a configuration diagram of an embodiment of the present invention. In the electrostatic mounting device 1 of FIG.
The electrostatic chuck 2 includes an insulating member 3 and an electrode 4 included therein. This insulating member has a thickness of, for example, 200 to 300 μm and is formed of alumina ceramics. A substrate 5 such as a silicon wafer is attracted onto the electrostatic chuck 2. On the other hand, the electrode 4 of the electrostatic chuck 2 is connected to a DC power source 7 through a high-frequency cut filter 6.
And one end of the DC power supply 7 is installed. The DC power supply 7 controls the voltage control unit 8 to change one of a positive voltage and a negative voltage to, for example,
An arbitrary voltage value of 0 V is applied to the electrode 4. Next, FIG. 2 shows a diagram for explaining the operation of the present invention. First, when no voltage is applied to the electrode 4, no charge exists on the surface of the electrostatic chuck 2. Therefore,
The voltage control unit 8 applies a positive voltage of, for example, 1500 V to the electrode 4 from the DC power supply 7 (FIG. 2A). In this case, the high frequency component is removed from the applied voltage by the high frequency cut filter 6. When a positive voltage is applied to the electrode 4, the electrode 4 is charged with a positive charge, and a negative charge is applied to the surface of the insulating member 3 (electrostatic chuck 2) and a positive charge is applied to the lower portion of the substrate 5 by electrostatic induction. A negative charge is induced at the top. At this time, a Coulomb force corresponding to the product of the charge amount of the negative charge on the surface of the insulating member 3 and the positive charge on the lower part of the substrate 5 is generated, and the substrate 5 starts to be attracted to the electrostatic chuck 2. Then, a positive voltage of 1500 V is applied for about 10 seconds (FIG. 2 (A)), and then the voltage is gradually decreased (FIG. 2 (A).
The voltage is reduced to a positive voltage of 00 V (FIG. 2A). These are controlled by the voltage control unit 8. That is, the positive voltage of 1000 V is a voltage value for holding the substrate 5 by suction, and prevents an unnecessary suction force (Coulomb force) from starting to the electrostatic chuck 2. Generally, as shown in FIG. 2B, the residual charge is proportional to the absolute value of the applied voltage and the time to some extent.
Since the substrate 5 is held at a voltage value that can hold the substrate 5 until (2), the residual charge generated on the substrate 5 (FIG. 2A) can be minimized. Therefore, even if the application of the voltage from the DC power supply 7 is stopped, the substrate 5 is
In the case of further separation, the substrate 5 can be easily separated without applying excessive stress to the substrate 5 with a lift pin or the like, and the situation that the substrate 5 is damaged can be avoided. Note that, in the above embodiment, as shown in FIG.
Although the case where the voltage is gradually lowered to the positive voltage of 000 V is shown, the voltage may be lowered to the positive voltage of 1000 V at a time 15 seconds after the start of adsorption as shown by the dashed line in FIG. In the above example, a case where a positive voltage is applied is shown, but the same effect is obtained even when a negative voltage is applied. Further, the voltage application time to the electrode 4 of the electrostatic chuck 2 is appropriately set in consideration of the size of the substrate and the amount of remaining charge. As described above, according to the present invention, the generation of residual charges is suppressed by applying a high voltage when the substrate is attracted to the electrostatic chuck and reducing the voltage to a predetermined voltage after the attraction. As a result, the processed substrate can be easily separated without being damaged, and the yield in manufacturing can be improved.

[Brief description of the drawings]     FIG.   FIG. 2 is a configuration diagram of one embodiment of the present invention.     FIG. 2   FIG. 4 is a diagram for explaining the operation of the present invention.     [Explanation of symbols]   1 Electrostatic adsorption device   2 Electrostatic chuck   3 Insulation members   4 electrodes   5 Substrate   6 High frequency cut filter   7 DC power supply   8 Voltage control unit

Claims (1)

1. An electrostatic chuck (2) for adsorbing a substrate (5) on an insulating member (3) containing an electrode (4), and an electrode (2) of the electrostatic chuck (2). And 4) applying a first voltage from the DC power supply (7) when adsorbing the substrate (5) to the electrostatic chuck (2); When the substrate (5) is processed, a second voltage lower than the first voltage is applied from the DC power supply (7) so as to attract and hold the substrate (5), and the substrate (5) is statically held. A voltage control unit (8) for stopping application of a voltage from the DC power supply (7) when separating from the electric chuck;
And an electrostatic chuck.