JPH04162443A - Electrostatic chuck device - Google Patents

Abstract

PURPOSE:To detach an article to be treated in a short time, and to decide the propriety of the detachment easily by providing an electrostatic attracting plate, a constant current power supply applying DC voltage at potential reverse to fixed potential to an electrode after application for a fixed time by a constant voltage power supply and a voltage detecting means detecting the voltage of the constant current power supply. CONSTITUTION:The annular electrodes 3 and 4 of an electrostatic attracting plate 1 can be connected to negative potential and positive potential in the constant current power supply 17 of DC voltage through a changeover switch 6 respectively. When the changeover switch 6 is changed over from the constant voltage power supply 5 side to the constant current power supply 17 side, DC voltage at reverse potential is applied to the electrodes 3 and 4. 18 represents the constant current power supply 17-that is, a voltmeter measuring voltage between the annular electrodes 3 and 4 of the electrostatic attracting plate 1. A computer 20 for control controls an ion etching device and an electrostatic chuck device.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention is an electrostatic chuck device, which is used particularly in the manufacturing process of semiconductor devices such as ICs and LSIs, and is suitable for holding objects to be processed by suction. The present invention relates to an electrostatic chuck device.

[Prior Art 1] In the semiconductor field, the performance of elements has been improving year by year, and in particular, there has been tremendous progress in higher integration and higher speed. The circuit pattern width of highly integrated devices is 0.5 μm.
However, on the other hand, the chip area is becoming larger.

In addition, it will be possible to manufacture highly integrated devices at low cost (the wafer area will also increase, and the degree of integration will increase from 4 Mbit to 16 Mbit).
As the height increases, the wafer size also increases from 6 inches to 8 inches.
The shift to inch sizes is progressing. These expansions in chip area, wafer area, and miniaturization of circuit patterns have all led to the ultimate reduction of dust on the wafer surface (
manufacturing equipment is required to do so.

As one of the devices that meet the above-mentioned requirements, an electrostatic chuck device is known that can attract and hold a wafer on the surface of the wafer in a non-contact state.

In this case, a single or plural electrodes are arranged in a dielectric material, and a high voltage of, for example, 100 OV or more is applied between the electrode and the ground of the device in the case of a single electrode, or between the electrodes in the case of a plurality of electrodes. By localizing the electric charge, the wafer is attracted and fixed by electrostatic attraction between the wafer and the wafer (for example, Japanese Patent Publication No. 57-44747).
(see issue).

[Problems to be Solved by the Invention] However, in such a conventional electrostatic chuck device, even if the application of voltage is stopped after processing of the object to be processed,
The problem is that it takes a long time to remove the workpiece from the electrostatic chuck device because the charge and polarization of the workpiece and the dielectric of the electrostatic chuck device do not disappear in a short time and the adsorption force remains. was there. This problem is particularly noticeable in wafers having an insulating film such as an oxide film on the surface. For this reason, for example, in dry etching equipment, productivity is inevitably reduced.

Therefore, in order to quickly dissipate the electrical charge on the object to be treated,
A method of applying a potential opposite to that during adsorption to the electrodes of the electrostatic chuck device after stopping the application of voltage to the electrostatic chuck device (see Japanese Patent Application Laid-Open No. 115226/1983) has been attempted, but
Although this method can achieve a high discharge speed, the reverse potential causes charges to accumulate in the opposite polarity, resulting in the adsorption state again, making it difficult to time the wafer release, and it has not yet achieved sufficient effectiveness. .

The time it takes for the adsorption force to become smaller than the predetermined value that allows the wafer to detach is affected by differences in physical properties depending on the type of wafer, the roughness of the adsorption surface, etc. This is because it is difficult to judge based on time.

SUMMARY OF THE INVENTION An object of the present invention is to provide an electrostatic chuck device that solves these conventional problems, allows a workpiece to be removed within a short period of time, and makes it easy to determine whether or not the workpiece can be removed.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides an electrostatic adsorption plate including an electrode and a dielectric layer covering the electrode, and a method of applying a DC voltage of a predetermined potential to the electrode. a constant voltage power supply that applies a voltage for a predetermined time; a constant current power supply that applies a DC voltage having a potential opposite to the predetermined potential to the electrode after the constant voltage power supply applies the voltage for a predetermined time; and a voltage detection means that detects the voltage of the constant current power supply. It is characterized by having the following.

[Function] According to the present invention, by applying a DC voltage of a predetermined potential to the electrodes of the electrostatic chuck device from a constant voltage power source, electrostatic adsorption force is generated and the object to be processed is adsorbed.

For example, when a predetermined process on a workpiece in a vacuum processing apparatus is completed, a DC voltage having a potential opposite to the above-described predetermined potential is applied to the electrode from a constant current power source. Then, the charge and polarization of the workpiece and the dielectric of the electrostatic chuck device disappear, and the attraction force decreases. On the other hand, since the voltage between the electrodes is proportional to the residual charge, if a constant current power source is used, the voltage will decrease as a linear function of time.

Therefore, by detecting this decreasing voltage,
The decrease in the attraction force can be easily detected, and within the minimum range, the workpiece can be detached from the electrostatic chuck device without damaging the workpiece.

[Example] The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a sectional view showing the basic structure of an electrostatic chuck device according to the present invention applied to a reactive ion etching device.

In FIG. 1, reference numeral 1 indicates an electrostatic adsorption plate, and reference numeral 2 indicates a dielectric layer made of ceramic such as alumina, in which annular electrodes 3 and 4 are provided concentrically. The electrode 3 is connected to the positive potential of a high voltage constant voltage power source 5, which is a DC power source, and the electrode 4 is connected to its negative potential via a changeover switch 6, so that a DC voltage can be applied.

A plurality of concentric refrigerant gas introduction grooves are formed as recesses on the surface of the dielectric layer 2, leaving an appropriate area of the dielectric surface (not shown), and the connecting grooves are communicated by linear grooves in the radial direction. ing.

Reference numeral 8 indicates a cathode block, and an electrostatic adsorption plate 1 is disposed on the upper surface of the cathode block 8. The electrostatic chuck plate 1 is provided with an opening 12 through which an arm 11 of a wafer lifter 10 for loading and unloading a wafer 9, which is a material to be etched, is inserted.

The cathode block 8 is cooled to a predetermined temperature by introducing a refrigerant such as water, brine, or a fluorinated refrigerant (such as Fluorinert manufactured by 3M) from the refrigerant inlet and flowing it through a refrigerant passage provided in the cathode block 8. Ru.

The electrostatic adsorption plate 1 is provided with a through hole (not shown), and this through hole communicates with a refrigerant gas passage provided in the cathode block 8, through which refrigerant gas such as helium is supplied to the back surface of the wafer 9. will be introduced in The introduced refrigerant gas spreads over the entire back surface of the wafer 9 through the linear grooves and the concentric refrigerant gas introduction grooves, radiating and transmitting the heat of the wafer 9 to the surface of the electrostatic chuck plate 1, thereby cooling the wafer 9.

Furthermore, the cathode block 8 on which the electrostatic adsorption plate 1 is arranged,
It is arranged inside the reaction vessel 13. The reaction vessel 13 is at ground potential.

The cathode block 8 is insulated from the reaction container 13 by an insulator 14 which also serves as a support for a wafer lifting device 10 attached to the reaction container 13. By applying high frequency power between the reaction vessel 13 and the cathode block 8 by the high frequency power supply 15, a gas plasma of the reaction gas introduced into the reaction vessel 13 is generated, and reactive species in this gas plasma are Contributes to etching.

In this example, after the inside of the reaction vessel 13 is evacuated to a high vacuum using a turbo pump or a mechanical pump, a reaction gas such as oxygen, or an inert gas together with the reaction gas is injected from the reaction gas inlet 16 through a flow rate control valve. and introduced into the reaction vessel 13.

Furthermore, the annular electrodes 3 and 4 of the electrostatic adsorption plate 1 described above can be connected to a negative potential and a positive potential of a constant current power source 17 of DC voltage, respectively, via a changeover switch 6.

In other words, when the changeover switch 6 is switched from the constant voltage power supply 5 side to the constant current power supply 17 side, the above-mentioned electrode 3
and 4 are applied with a DC voltage of opposite potential.

Further, 18 is a voltmeter that measures the voltage between the constant current power source 17 and the annular electrodes 3 and 4 of the electrostatic adsorption plate 1.

A control computer 20 controls the ion etching device and the electrostatic chuck device.

An example of the procedure for performing ion etching on a wafer 9 as an object to be processed using the ion etching apparatus of this embodiment having the above configuration will be described below with reference to the time chart shown in FIG.

First, the wafer lifting device 10 is operated and the arm 11 of the wafer receiver is lifted. Then, the wafer 9 is introduced into the reaction container 13 using a wafer introducing device (not shown), and the wafer holder is placed on the arm ll.

Now, the wafer holder of this wafer lifting device IO is arm 1.
If LO is the time point at which the loading is completed on 1, this t.

At this point, the constant voltage power supply 5 is turned on and the electrostatic adsorption plate 1
A DC voltage with a positive potential is applied to the electrode 3 via the changeover switch 6, and a DC voltage with a negative potential is applied to the electrode 4. The reason for applying the voltage in advance in this way is that it takes some time for the electrostatic adsorption plate 1 to generate the maximum adsorption force. When a predetermined period of time has elapsed from time to, the wafer lifting device IO is lowered to place the wafer 9 on the electrostatic chuck plate 1.

Then, from the time when a positive voltage is applied to the electrode 3, the contact voltage of 5 is applied for a predetermined time.
At the same time, the reaction gas is introduced at one point in time, and the cathode block 8
High frequency power is applied from the high frequency power source 15 to etching the wafer 9.

In response to detection by an etching end point detection device (not shown) that detects the progress of etching of the wafer 9, a reaction gas is introduced into the reaction vessel 13 and high frequency power is applied to the cathode block 8 at time t2 when etching is completed. At the same time, the changeover switch 6 is switched, and instead of applying a positive voltage to the electrode 3 and a negative voltage to the electrode 4, the constant current power supply 17 applies a negative voltage to the electrode 3 and a positive voltage to the electrode 4. applied.

Therefore, from this point in time t2, the voltage of the constant current power supply 17, and therefore the voltage V between the electrodes 3 and 4, is monitored by the voltmeter 18, and this voltage becomes a predetermined ratio to the output voltage v0 of the constant voltage power supply 5. At time t3, the above-mentioned constant current power supply 17
The application from is stopped.

Here, the voltage V is 0. lV. It is preferably at most 0.0 IVo, more preferably at most 0.0 IVo.

At this time point t3, the electrostatic adsorption force has decreased below a predetermined value, so the arm 11 of the wafer holder can be raised, and the wafer 9 can be easily detached from the electrostatic adsorption plate 1. .

Here, an equivalent circuit of the electrostatic chuck device shown in FIG. 1 is shown in FIG.
The relationship with the electrostatic adsorption force F will be explained using FIG. 4, which shows changes in voltage (2) and current I between

As mentioned above, the constant voltage power supply 5 generates a high voltage, e.g.
When 0OV is applied between the electrodes 3 and 4, a large current ■ flows only immediately after the application, and charges Qe are accumulated on the electrostatic adsorption plate 1 under a predetermined polarity.

Now, if Ce and Re are the equivalent capacitance and equivalent resistance of the electrostatic chuck plate 1, Rv & the internal resistance of the constant voltage power supply 5, and Ri is the internal resistance of the constant current power supply 17, then the internal resistance Ri of the constant current power supply 17 is While the internal resistance Rv of the constant voltage power supply 5 is Rv<ω, Ricf=O.

Therefore, after being switched to the constant current power supply 17 of the opposite potential by the changeover switch 6 as described above, the electrode 3 of the electrostatic adsorption plate 1
and 4 is mainly determined by the equivalent capacitance Ce within the electrostatic chuck plate 1 and the localized residual charge Qe, and from the relationship Qe=CeV, the voltage V is proportional to the residual charge Qe.

Moreover, when the constant current power supply 17 is used, the residual charge Qe is Qe=Qeo-S Idt=Qeo-It
(Qeo is the residual charge immediately before switching to a constant current power source.) Here, t is a time parameter.

From both of the above equations, it can be understood that the voltage V decreases as a linear function of time.

Therefore, as mentioned above, the output voltage of the constant voltage power supply 5 of this voltage V is . By monitoring the rate of decrease with respect to Qe, the amount of residual charge Qe can be determined. For example, when the voltage ■ becomes 0, the residual charge Qe also becomes 0.

Therefore, as mentioned above, the fact that the voltage ■ is less than o, iv means that the electrostatic adsorption force F is equal to the square of the charge Qe (Qe''
), the voltage V. This is nothing less than 1/100 of the electrostatic adsorption force that is sometimes obtained.

Under these conditions, adsorption and desorption experiments were repeated four times for 500 wafers, but no malfunction or damage occurred for a single wafer.

[Effects of the Invention] As explained above, according to the present invention, it is possible to desorb the object to be treated in a short time, and it is possible to determine whether or not desorption is possible using a voltage that changes as a linear function of time. This makes it easier to make decisions. This is extremely easy and accurate compared to the conventional method of simply applying a reverse voltage, which has to judge whether or not desorption is possible based on the current curve.

Furthermore, since the possibility of detachment is determined by voltage measurement instead of current measurement, it is resistant to noise and has high reliability.

[Brief explanation of the drawing]

FIGS. 4 and 5 are time charts showing changes in the voltage (2) and current (2) of the electrode plate of the electrostatic chuck plate of the embodiment of the present invention, respectively. l... Electrostatic adsorption plate, 2... Dielectric layer, 3.4... Electrode, 5... Constant voltage power supply, 6... Changeover switch, 8... Cathode block, 11... - The wafer receiver is an arm, 15...high frequency power supply, 17...constant current power supply, 18...voltmeter, 20...control computer.

Claims (1)

[Scope of Claims] 1) An electrostatic adsorption plate comprising an electrode and a dielectric layer covering the electrode, a constant voltage power supply that applies a DC voltage of a predetermined potential to the electrode for a predetermined period of time, and the constant voltage power supply. An electrostatic chuck device comprising: a constant current power source that applies a DC voltage having an opposite potential to the predetermined potential to the electrode after application for a predetermined period of time; and a voltage detection means that detects the voltage of the constant current power source. .