JP2574066B2 - Electrostatic suction device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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. In recent years, in semiconductor manufacturing, a substrate is fixed using an electrostatic suction device,
In many cases, processing such as etching is 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.

[0002]

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 electrodes are 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 used for the electrostatic check is used as alumina ceramics in a state where the insulator is heated to a high temperature by etching or the like.

[0003] Such residual charges are spontaneously discharged when left for a long time, but as a method of forcibly discharging the residual charges, when the substrate is separated from the electrostatic chuck, an alternating voltage is applied after the application of a high voltage is stopped. Attempts have been made to apply the voltage while gradually reducing it.

[0004]

However, spontaneous discharge of the residual charge after being left for a long time is not preferable during the manufacturing process. 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.

[0005] Therefore, when the substrate on the electrostatic chuck is to be separated by lift pins or the like, there is a problem that an excessive stress is applied to the substrate and the substrate may be damaged. Therefore,
SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide an electrostatic attraction device that suppresses generation of residual charges and facilitates substrate separation.

[0006]

The object of the present invention 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, and an electrostatic chuck. A voltage control unit that applies a high voltage from the DC power supply when the substrate is sucked to the electric chuck, and reduces the applied voltage to a voltage value that causes the substrate to be sucked and held after the suction. Will be resolved.

[0007]

As described above, when the substrate is sucked on the electrostatic chuck by the DC power supply, a high voltage is applied by the voltage control unit at the time of suction, and the voltage is reduced to the voltage value held by suction after the suction. As a result, unnecessary chucking force is not generated in the electrostatic chuck, and it is possible to minimize the generation of residual charges when the application of voltage is stopped after predetermined processing. Therefore, it is possible to avoid a situation in which the substrate is broken when the substrate is separated from the electrostatic chuck.

[0008]

FIG. 1 is a block diagram showing an embodiment of the present invention.
In the electrostatic mounting apparatus 1 shown in FIG. 1, an 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 via a high-frequency cut filter 6, and one end of the DC power source 7 is installed. The DC power supply 7 applies one of a positive voltage and a negative voltage to the electrode 4 with an arbitrary voltage value of, for example, ± 1000 V to ± 1500 V by the voltage control unit 8. 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. Then, the voltage control unit 8 applies a voltage to the electrode 4 from the DC power supply 7.
For example, a positive voltage of 1500 V is applied (FIG. 2A)
). In this case, high frequency components are 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
, A negative charge is induced on the surface of the insulating member 3 (electrostatic chuck 2), a positive charge is induced on a lower portion of the substrate 5, and a negative charge is induced on an upper portion thereof. 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 electrostatic chuck 2
The substrate 5 starts to be adsorbed thereon.

Then, a positive voltage of 1500 V is applied for about 10 seconds (FIG. 2A), and thereafter, the voltage is gradually decreased (FIG. 2A), and 1000 V is applied for 15 seconds from the start of voltage application. (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 somewhat proportional to the absolute value of the applied voltage and the time, and the voltage that can hold the substrate 5 until the end of the processing such as etching by heating (time t). Since the adsorption is performed by the value (FIG. 2A), the residual charge generated on the substrate 5 can be minimized.

Therefore, even if the application of the voltage from the DC power supply 7 is stopped, when the substrate 5 is separated from the electrostatic chuck 2,
The substrate 5 can be easily separated without applying excessive stress to the substrate 5 with a lift pin or the like, and a situation in which the substrate 5 is damaged can be avoided. In the above embodiment,
As shown in FIG. 2A, a positive voltage of 1500 V
FIG. 2A shows a case where the voltage is gradually decreased to a positive voltage of 00 V. As shown by a dashed line in FIG.
After a few seconds, the voltage may be reduced to a positive voltage of 1000 V at a time. 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.

[0013]

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. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is a diagram for explaining the operation of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electrostatic adsorption device 2 Electrostatic chuck 3 Insulating member 4 Electrode 5 Substrate 6 High frequency cut filter 7 DC power supply 8 Voltage control part

Claims (1)

(57) [Claims] An electrostatic chuck (2) for adsorbing a substrate (5) on an insulating member (3) containing an electrode (4), and an electrode (4) of the electrostatic chuck (2) having a predetermined value. A DC power supply (7) for applying a voltage; and a high voltage applied from the DC power supply (7) when the substrate (5) is attracted to the electrostatic chuck (2). And a voltage control unit (8) for reducing the applied voltage to a voltage value for holding and holding the electrostatic chuck.