JPH04343447A - Electrostatic attraction apparatus - Google Patents

Abstract

PURPOSE:To realize an accurate wafer conveying and to control a temperature of a wafer with high reproducibility in an electrostatic attraction apparatus for holding the wafer by attraction in a semiconductor manufacturing process. CONSTITUTION:In an electrostatic attraction apparatus having A electrodes 24, 25 in which a positive voltage is applied and B electrodes 26, 27 in which a negative voltage is applied to electrostatically attract a wafer 33 by the electrodes 24, 25 and 26, 27, an electrostatic potentiometer probe 22 and an electrostatic potentiometer 34 for measuring a potential of the wafer 33 in a state attracted to the electrodes 24, 25 and 26, 27, are provided. Voltages to be applied to the electrodes 24, 25 and 26, 27 are so controlled that the potential of the wafer 33 becomes zero volt based on the potential of the wafer 33 to be measured by the probe 22 and the potentiometer 34.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic chuck device, and more particularly to an electrostatic chuck device for holding a wafer by suction in a semiconductor manufacturing process.

[0002] Automation has advanced in semiconductor manufacturing processes in recent years, and it has become necessary to accurately transport wafers within manufacturing equipment.

[0003] Therefore, it is important to accurately and quickly attach and detach wafers in wafer suction devices incorporated in semiconductor manufacturing processes.

0004

2. Description of the Related Art FIG. 5 is a block diagram showing an example of a conventional electrostatic chuck device. As shown in the figure, a conventional electrostatic adsorption device 1 generally uses a DC high voltage. This DC high-voltage type electrostatic adsorption device 1 is constructed by applying a DC voltage to a positive electrode 2 and a negative electrode 3, respectively.
, 3 through an insulator 4, causes dielectric polarization in the object (wafer) 5 placed on the surface of the wafer 5, and the electrostatic force of positive and negative charges induced on the surface of the wafer 5 causes the wafer 5 to become an insulator. It has a structure that attracts 4.

FIG. 6 shows an equivalent circuit when the electrostatic adsorption device 1 described above is installed in an RIE device (reactive ion etching device) 6. In the figure, 7 is a chamber, 8 and 9 are DC high voltage power supplies, and 10 is a high frequency generator. When processing the wafer 5 using the RIE device 6, first remove the chamber 7, place the wafer 5 on the electrodes 2 and 3 of the electrostatic chuck device 1, and apply pressure to each electrode 2 and 3 using the DC high voltage power supplies 8 and 9. Apply positive and negative DC voltage. As a result, dielectric polarization occurs in the wafer 5 as described above, and the wafer 5 is electrostatically attracted to the insulator 4. Subsequently, the chamber 7 is installed, the chamber 7 is brought to a predetermined degree of vacuum, the high frequency generator 10 is driven to generate plasma, and the wafer 5 is etched. During this etching process,
The wafer 5 remains attracted to the electrostatic attraction device 1. When the predetermined etching process is completed, the chamber 7 is removed again, the voltage application of the DC high voltage power supplies 8 and 9 is also canceled, and the wafer 5 is removed from the electrostatic chuck device 1.

In the conventional electrostatic chuck device 1, when the wafer 5 is chucked, DC voltages of the same amount and of different signs are applied to each electrode 2, 3.

[0007]

Although the electrodes 2 and 3 are manufactured to have the same area, there is some difference in area due to manufacturing errors and the like. In addition, the wafer 5 and each electrode 2
The capacitance between the wafer 5 and each of the electrodes 2 and 3 differs due to variations in the thickness of the insulator 4 interposed between the wafer 5 and the electrodes 2 and 3, and variations in relative permittivity due to non-uniformity of the insulator 4. For this reason,
Even if equal amounts of DC voltages of different signs are applied to each electrode 2 and 3,
The potential of the wafer 5 is not zero volts, but has some potential.

The wafer 5 electrostatically attracted in this state
When the wafer 5 is exposed to an atmosphere containing valence particles such as plasma, charges are supplied from the plasma to bring the potential of the wafer 5 to zero. After that, when the plasma processing is finished and the DC high voltage power supplies 8 and 9 are turned off, the charge supplied from the plasma remains, and even after the DC high voltage power supplies 8 and 9 are turned off, the remaining charge remains on the wafer. In order to maintain the adsorption power,
The wafer 5 cannot be peeled off from the electrostatic chuck device 1. If an attempt is made to peel off the wafer 5, which maintains the suction force in this way, by applying an auxiliary force, there is a problem that the wafer 5 may be damaged because an unreasonable force is applied to the wafer 5. there were.

[0009] Furthermore, in a state where charges remain on the wafer 5 as described above, the polarity of the wafer 5 can be changed simply by changing the polarity of the voltage applied to each electrode 2, 3. For this reason, when the conventional electrostatic adsorption device 1 is used in a plasma etching device such as an RIE device or an ECR (electron cyclotron resonance) etching device, if the polarity of the voltage applied to each electrode 2 and 3 changes, the adsorption force during etching will increase. changes (
When the potential of the wafer 5 is positive, a potential difference is generated between each electrode 2, 3 and the wafer 5 due to the negative self-bias voltage, and the attraction force of the wafer 5 increases).

As described above, when the adsorption force of the electrostatic adsorption device 1 to the wafer 5 changes due to a change in the polarity of the voltage applied to each electrode 2, 3, the cooling performance of the wafer 5 changes. Therefore, the wafer temperature during etching differs between the wafer 5 before and after the polarity of the applied voltage is changed, causing a change in the etching shape and etching rate, resulting in a problem that stable etching cannot be performed.

The present invention has been made in view of the above points, and an object of the present invention is to provide an electrostatic chuck device that can realize accurate wafer transport and control wafer temperature with good reproducibility.

0012

[Means for Solving the Problems] In order to solve the above problems, the present invention includes a first electrode to which a positive voltage is applied and a second electrode to which a negative voltage is applied, and the first and second electrodes are provided. In an electrostatic attraction device that electrostatically attracts an object to be attracted by a second electrode, the voltage applied to the first and second electrodes is controlled so that the potential of the object to be attracted becomes zero volts. This is a characteristic feature.

[0013] The invention also includes a first electrode to which a positive voltage is applied and a second electrode to which a negative voltage is applied;
An electrostatic adsorption device that electrostatically adsorbs an object to be adsorbed by the electrodes is provided with an electrostatic meter that measures the potential of the object while it is adsorbed to the first and second electrodes. It is characterized by a configuration in which the voltage applied to the first and second electrodes is controlled based on the potential of the attracted object measured by an electrometer so that the potential of the attracted object becomes zero volts. be.

[0014]

[Function] By configuring the electrostatic adsorption device as described above, the area difference between each electrode due to electrode manufacturing error, the variation in the thickness of the insulator interposed between the object to be adsorbed and each electrode, and the difference in the thickness of the insulator are eliminated. Regardless of variations in relative permittivity due to non-uniformity, the potential of the adsorbed object is always zero volts. Therefore, when the voltage applied to each electrode is cut off, the attraction force against the object to be attracted disappears, so that the object to be attracted can be easily removed from the electrostatic attraction device.

Furthermore, even if the polarity of the applied voltage is changed, the adsorption force does not change, the wafer temperature during etching is stabilized, and the etched shape and etching rate can be stabilized.

[0016]

Embodiments Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows an electrostatic adsorption device 20 which is an embodiment of the present invention.
FIG. Electrostatic adsorption device 20 shown in the figure
Roughly speaking, it is composed of an electrostatic chuck 21, an electrostatic meter probe 22, and an electrostatic chuck power source 23.

As shown in FIG. 2, the electrostatic chuck 21 has four electrodes 24 to 27 formed concentrically. Furthermore, the electrodes 24 and 25 and the electrodes 26 and 27 form a pair, respectively, and constitute a bipolar electrostatic chuck. Now, if the electrodes 24 and 25 are A poles (positive electrodes) and the electrodes 26 and 27 are B poles (negative electrodes), the area SA of the A pole and the area SB of the B pole are SA = 61 cm2 and SB = 4, respectively.
It is 3 cm2. Moreover, each electrode 24-27 is formed of copper.

Each of the electrodes 24 to 27 described above is formed on a silicone resin 29 placed on an aluminum pedestal 28 (thickness 15 mm). Furthermore, each electrode 24~
On the top of 27, there is alumina (Al2O3) which is an insulator.
A ceramic 30 made of The thickness of this ceramic 30 is 0.25 mm. Further, a hole 28a is formed in the center of the aluminum pedestal 28, and the lead wires 31 connected to each electrode 24 to 27 are connected to the hole 28a.
It passes through and is pulled out to the back side of the aluminum pedestal 28. Further, this hole 28a is sealed with epoxy resin 32 after the lead wire 31 is drawn out.

Referring back to FIG. 1, the explanation will be made again. The electrostatic meter probe 22 has electrodes 24 to 24 facing the electrostatic chuck 21.
It is arranged on the upper part of 27. This electrostatic meter probe 2
2 measures the potential generated in the wafer 33 attracted to the electrodes 24-27. This electrostatic potential probe 22 is connected to an electrostatic chuck power supply 23.

The electrostatic chuck power supply 23 includes a control section 35 that includes an electrostatic meter 34 that calculates an electrostatic potential from a signal supplied from the electrostatic potential probe 22, and an A electrode (positive electrode) 24, 25.
an applied voltage variable section 36 that varies the voltage applied to the B poles (negative electrodes) 26 and 27; an applied voltage variable section 37 that varies the voltage applied to the B poles (negative electrodes) 26 and 27; A positive voltage power supply 38 applies the voltage to the A poles (positive electrodes) 24 and 25, and a negative voltage power supply 3 applies a voltage of the voltage value set by the applied voltage variable section 37 to the B poles (negative electrodes) 26 and 27.
9.

The control section 35 controls the electrostatic potential meter 34 to
Based on the potential generated at , the voltage values to be applied to the A poles 24 and 25 and the B poles 26 and 27 are calculated in order to set this potential to zero volts. When the voltage values to be applied to the A poles 24, 25 and the B poles 26, 27 for setting the potential of the wafer 33 to zero volts are determined, the control unit 35 controls the applied voltage variable unit 36.
, 37 to transmit this voltage value to the applied voltage variable parts 36, 37.
drives the positive voltage power supply 38 and the negative voltage power supply 39 to generate a DC voltage A with a voltage value that makes the potential of the wafer 33 zero volts.
It is applied to the poles 24 and 25 and the B poles 26 and 27. Thereby, the potential of the wafer 33 can be set to zero volts.

As described above, the electrostatic adsorption device 2 according to the present invention
0, the potential of the wafer 33 can be set to zero volts, so the difference in area between the electrodes 24 to 27 due to electrode manufacturing errors, etc., and the thickness of the ceramic 30 interposed between the wafer 33 and each electrode 24 to 27 Even if there are variations in the dielectric constant due to the non-uniformity of the ceramic 30, the potential of the wafer 33 is always set to zero volts by the electrostatic meter probe 22 and the electrostatic chuck power supply 23. Therefore,
When the voltage applied to each electrode 24 to 27 is cut off, the wafer 33
Since the adsorption force on the electrostatic chuck 21 is eliminated, the wafer 33 can be easily peeled off from the electrostatic chuck 21. Furthermore, since the potential of the wafer 33 is always zero volts, the electrostatic adsorption device 20 can be applied to an RIE device or an ECR etching device, and the adsorption force will not change even if the polarity of the applied voltage is switched. , the wafer temperature during etching is stabilized, and the etching shape and etching rate can be stabilized.

FIGS. 3 and 4 show the results of experiments conducted by the inventor to demonstrate the effects of the electrostatic chuck device 20 according to the present invention.

FIG. 3 shows the experimental results of a peel test on the wafer 33. FIG. 3A shows the experimental results of the electrostatic chuck device 20 according to the present invention, and FIG. 10B shows the experimental results of the conventional electrostatic chuck device. The experimental method involved applying DC voltage to the electrodes to attract the wafer to an electrostatic chuck, exposing the wafer to plasma in this state, then turning off the DC voltage and testing whether the wafer would peel off. . Also, the experimental conditions were self-bias:
300W, Argon gas (Ar) flow rate: 100scc
m, pressure: 0.2 Torr, processing time: 30 seconds. In addition, in the wafer peeling test column of the same figure, indicates that the wafer could be peeled off without applying any force, and × indicates that the wafer could not be peeled off. It shows.

As shown in the figure, in the electrostatic chuck device 20 according to the present invention, the wafer 33 could be peeled off from the electrostatic chuck 21 immediately after the DC voltage was turned off, regardless of the increase or decrease in the electrode voltage. On the other hand, with the conventional apparatus, it was not possible to separate the wafer from the electrostatic chuck at each electrode voltage value.

On the other hand, FIG. 4 shows the experimental results for determining the maximum temperature of the wafer during etching. In this figure, (A) shows the experimental results of the device 20 according to the present invention, and (B) shows the experimental results of the conventional device. In this experiment, in the electrostatic adsorption device 20 according to the present invention, the A pole 2
The voltage value (VA) applied to 4, 25 is 700V, B
The voltage value (VB) applied to poles 26 and 27 is 1000V.
Then, the maximum temperature reached by the wafer during etching was measured when continuous etching was performed by switching between VA and VB for every other wafer. In addition, in the conventional equipment, when VA = VB = 0 (volts), V
The maximum temperature reached by the wafer during etching was measured when continuous etching was performed by switching between A and VB.

From the figure, an electrostatic adsorption device 20 according to the present invention is shown.
The maximum temperature reached by the wafer was 72°C to 79°C (temperature range: 7°C), whereas with the conventional equipment it was 69°C to 82°C (temperature range: 13°C). It can be seen that the temperature difference between wafers is smaller in the electrostatic chuck device 20 according to the above. Therefore, from the figure, it was verified that the electrostatic adsorption device 20 according to the present invention can stabilize the wafer temperature and stabilize the etching shape and etching rate.

In the embodiment described above, the potential generated on the wafer 33 is directly measured by the electrostatic meter probe 22, and the voltage value applied to each electrode 24 to 27 by the electrostatic chuck power supply 23 is determined based on this measured value. By controlling the voltage, the potential of the wafer 33 is set to zero volts.

However, as mentioned above, the reason why the wafer has a potential is due to differences in the area of each electrode caused by manufacturing errors, etc., and variations in the thickness of the insulator (ceramic, etc.) interposed between the wafer and each electrode. , is a quantitative value of the variation in relative dielectric constant due to non-uniformity of the insulator. Therefore, for example, by taking these causes into consideration when shipping an electrostatic adsorption device, and adjusting the voltage value applied to each electrode in advance to a voltage value that makes the wafer potential zero volts, the potential of the wafer can be increased. can be prevented from occurring (this method
(The accuracy is lower than the method of directly measuring the wafer potential as described above.) Below, we will explain how to determine the voltage value of the applied voltage applied to each electrode in this method (
Note that the reference numerals used in FIG. 1 will be used to explain each component.

Now, the amount of charge generated on the wafer due to the above causes when voltage is applied is Q, the capacitance between the A electrodes 24, 25 and the wafer 33 is CA, and the capacitance between the B electrodes 26, 27 and the wafer 33 is If the electrostatic capacitance between them is CB, then the amount of charge Q can be expressed as Q=CA x VA + CB x VB. Therefore, by determining the applied voltages VA and VB so that CA x VA + CB x VB = 0, the wafer charge amount Q can be made zero, and the wafer potential can be made zero volts.

Further, the capacitance between each electrode 24 to 27 and the wafer 33 is determined by the dielectric constant ε of the ceramic 30, the thickness d of the ceramic 30 interposed between the electrode and the wafer 33, and the area SA of the electrode. , SB as variables, so if the thickness d and dielectric constant ε of the ceramic 30 are uniform and homogeneous, the wafer charge Q is equal to the electrode area SA
, SB can be regarded as a linear function with variables. Therefore, the wafer charge amount Q is: Q=k・(SA ×VA +SB ×VB) However, k
can be expressed as a constant. Therefore, by determining the applied voltages VA and VB so that SA x VA + SB x VB = 0, the wafer charge amount Q can be made zero, and the wafer potential can be made zero volts.

[0032]

Effects of the Invention As described above, in the present invention, by applying a voltage to each electrode such that the potential of the target object becomes zero volts, the target object can be easily removed even after being exposed to an atmosphere containing valence particles such as plasma. Since no electric charge is accumulated on the adsorbed object, the adsorbed object can be quickly peeled off from the device after stopping the voltage application to the electrode, and the adsorption force remains constant even if the polarity of the voltage applied to the electrode is changed. It has the advantages of being able to perform wafer temperature control with good reproducibility and being able to perform stable processing on objects to be attracted.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of an electrostatic adsorption device that is an embodiment of the present invention.

FIG. 2 is an enlarged view of an electrostatic chuck.

FIG. 3 is a diagram showing the results of an experiment conducted by the inventor to demonstrate the effects of the device of the present invention.

FIG. 4 is a diagram showing the results of an experiment conducted by the inventor to demonstrate the effects of the device of the present invention.

FIG. 5 is a schematic configuration diagram showing an example of a conventional electrostatic adsorption device.

FIG. 6 is a diagram showing an equivalent circuit when the electrostatic adsorption device of FIG. 5 is installed in an RIE apparatus.

[Explanation of symbols]

20 Electrostatic adsorption device 21 Electrostatic chuck 22 Electrostatic meter probe 23 Electrostatic chuck power supply 24, 25 A electrode 26, 27 B electrode 28 Al pedestal 29 Silicone resin 30 Ceramic (insulator) 32 Epoxy resin 33 Wafer 34 Electrostatic potential meter 35 Control section 36, 37 Applied voltage variable section 38 Positive voltage power supply 38 Negative voltage power supply

Claims (4)

[Claims] Claim 1: A first electrode (24,
25) and a second electrode (26, 27) that applies a negative voltage.
In an electrostatic adsorption device that electrostatically adsorbs an object (33) using the first and second electrodes (24-27), the electric potential of the object (33) is zero volts. An electrostatic chuck device characterized in that the voltage applied to the first and second electrodes (24 to 27) is controlled so that the voltages applied to the first and second electrodes (24 to 27) are controlled. 2. In the electrostatic attraction device according to claim 1, the capacitance between the first electrode (24, 25) and the object to be attracted (33) is C1, and the second electrode ( 26, 27) and the object to be attracted (33) is C2, the voltage applied to the first electrode (24, 25) is V1, and the second electrode When the voltage applied to the electrodes (26, 27) is V2, the voltage applied to the first and second electrodes (24 to 27) is selected so that C1 x V1 = C2 x V2. An electrostatic adsorption device featuring: 3. The electrostatic adsorption device according to claim 1, wherein the first electrode (24, 25) has an electrode area S1, the second electrode (26, 27) has an electrode area S2, and ,
The voltage applied to the first electrodes (24, 25) is V
1, and when the voltage applied to the second electrode (26, 27) is V2, apply it to the first and second electrodes (24 to 27) so that S1 x V1 = S2 x V2. An electrostatic adsorption device characterized in that it is made by selecting a voltage to be used. Claim 4: A first electrode (24, 25) to which a positive voltage is applied.
), and a second electrode (26, 27) to which a negative voltage is applied, and an electrostatic device that electrostatically attracts an object to be attracted (33) by the first and second electrodes (24 to 27). The adsorption device is provided with an electrostatic meter (22, 34) that measures the potential of the adsorbed object (33) in a state of being adsorbed to the first and second electrodes (24-27), and the electrostatic electrometer Based on the potential of the object (33) measured by (22, 34), the first and second electrodes (24 to 27) are connected so that the potential of the object (33) is zero volts. An electrostatic chuck device characterized in that it is configured to control an applied voltage.