WO2012090430A1

WO2012090430A1 - Electrostatic adsorption apparatus

Info

Publication number: WO2012090430A1
Application number: PCT/JP2011/007094
Authority: WO
Inventors: 栄太郎森本
Original assignee: キヤノンアネルバ株式会社
Priority date: 2010-12-27
Filing date: 2011-12-20
Publication date: 2012-07-05
Also published as: JP2014075372A

Abstract

Provided, with a simple structure, is an electrostatic adsorption apparatus equipped with: sufficient electrostatic adsorption force even when the substrate to be adsorbed is a glass substrate made of insulation material; and an electrostatic adsorption chuck from which a substrate can be removed quickly. The electrostatic adsorption apparatus is equipped with: a dielectric plate on the surface of which is formed a plurality of protruded sections that can support a substrate with the apex faces thereof, and recess sections surrounding the protruded sections; an electrode formed within the dielectric plate; and a first external power supply for applying a substrate adsorption voltage to the electrode. The protruded sections are provided with conductor cover-films on at least the apex faces thereof, and the first external power supply is provided with a substrate-desorption-voltage power supply that can apply, to the electrode, an inverse voltage having a polarity that is inverse with respect to the polarity of the substrate adsorption voltage to be applied to the electrode, upon desorbing the substrate. The conductor cover-films are connected to a second external power supply provided with another substrate-desorption-voltage power supply that can apply, to the conductor cover-films, an inverse voltage having a polarity that is inverse with respect to the polarity of the substrate adsorption voltage to be applied the electrode, upon desorbing the substrate.

Description

Electrostatic adsorption device

The present invention relates to an electrostatic attraction apparatus provided with an electrostatic chuck used for holding a substrate on a support during the processing of the substrate in a manufacturing process of an electronic component such as a magnetic head having a semiconductor manufacturing process or a process similar thereto. About.

As a method for attracting a high-resistance substrate such as a glass substrate, an electrostatic attracting apparatus (hereinafter also referred to as “electrostatic chuck”) is used. Conventionally, a method of adsorbing using a high voltage of 3 kV and 10 kV was taken, but a method of adsorbing at a low voltage of 1 kV is disclosed in Patent Document 1. In Patent Document 1, it is described that the adsorption can be performed by heating the glass substrate to make the volume resistivity below a certain value, but the volume resistivity is 1 × 10 ⁶ Ω · cm to 1 × 10 ¹⁴ Ω · cm. It takes an enormous amount of time for the adsorption force to decrease in the range of. Therefore, there is a problem that the substrate cannot be collected quickly and stably. Although the volume resistivity can be lowered by raising the temperature, there is a problem that it cannot be processed in a temperature environment of 150 ° C. or higher because the heat resistance of the adhesive for attaching Si to the glass substrate is low. Similarly, when the low temperature treatment is necessary due to the film quality problem, there is a problem that the substrate cannot be recovered quickly and stably.

As an electrostatic chuck for solving this problem, one disclosed in Patent Document 2 is known. The electrostatic chuck described in Patent Document 2 includes a dielectric plate having convex and concave portions formed on the surface by embossing, an electrode provided in the dielectric plate, and an external power source that applies a voltage to the electrode. I have. Further, the top surface (substrate support surface) of each convex portion is covered with conductor wiring, and the substrate support surface of each convex portion is electrically connected by this conductor wiring, and the conductor wiring is grounded or floated. A switch is provided. Furthermore, the electrode part close | similar to a convex part is removed corresponding to each convex part. In the electrostatic chuck described in Patent Document 2, the conductor wiring is held in a floating state by a switcher during substrate processing. At the end of the processing of the substrate, the conductor wiring is grounded with a switch, so that the electric charges generated on the embossed protrusions, the back surface of the substrate, and the surface of the dielectric plate are released, and the adsorption power disappears quickly. I am letting.

Further, as a method for detaching the substrate smoothly, for example, a method of applying a reverse voltage as disclosed in Patent Document 3 is known. Further, Patent Document 4 discloses a method for improving the point that it is difficult to adjust the reverse voltage application time with respect to the insulating substrate. In the separation method of Patent Document 4, a voltage is applied to an electrode provided in an electrostatic adsorption device, the insulating substrate is electrostatically adsorbed, processed in a vacuum atmosphere, and then taken out of the insulating substrate. The electrode is separated from the electrostatic chuck while a voltage having a polarity opposite to that at the time of electrostatic chucking is applied to the electrode.

Japanese Patent Laid-Open No. 2005-32858 JP 2004-22889 A JP-A-4-230051 JP 2001-156161 A

However, in Patent Document 2, the Johnson Rabeck force acting between the substrate support surface of each convex portion and the back surface of the substrate in contact with the substrate support surface is a very large adsorption force. For this reason, the electrostatic chuck of Patent Document 2 in which this Johnson Rabeck force does not work has a problem that the attracting force tends to be insufficient. This problem can be solved by removing the conductor wiring covering the substrate support surface of the convex portion so that the Johnson Rabeck force works. However, when the conductor wiring that covers the substrate support surface of the convex portion is removed, it becomes impossible to move the charge quickly by setting the conductor wiring to the ground state with the switch, and until the substrate can be detached due to the residual charge. The problem is that time is delayed. Further, the electrostatic chuck of Patent Document 2 is provided with a conductor wiring that covers and electrically connects the substrate support surface of each convex portion and removes the substrate when removing the substrate, and connects this to the switch. There is also a problem that a special wiring structure has to be constructed, and the structure becomes complicated.

Further, in the separation method of Patent Document 4, when an insulating material different from the material constituting the electrostatic chuck is used as the substrate material, the back surface of the substrate is caused by the difference between the dielectric constant of the electrostatic chuck and the dielectric constant of the substrate. The electric charge loses the escape. As a result, since the residual attracting force remains on the substrate, there is a problem that the separation of the substrate from the electrostatic chuck becomes unstable.

Also, the adsorption method of Patent Document 1 can electrostatically adsorb a glass substrate at a low voltage by raising the temperature of the glass substrate. Further, even when the glass substrate is detached, if the temperature of the glass substrate is increased, the volume resistance of the glass substrate is reduced, so that the glass substrate can be detached more easily than at room temperature. It takes a long time for the volume resistance to depart between 1e + 6 Ω · cm and 1e + 11 Ω · cm, for example, when the temperature is restricted due to device fabrication. For this reason, there is a problem in that the substrate cannot be stably detached because the separation method described in Patent Document 4 in which a reverse voltage at the time of adsorption is applied to the adsorption voltage application electrode when the substrate is detached.

The present invention has been made in view of the above-mentioned conventional problems. With a simple structure, even when the substrate is a glass substrate such as an insulating material, the substrate can be quickly removed from the electrostatic chuck with sufficient electrostatic adsorption force. An object of the present invention is to provide an electrostatic chucking device including an electrostatic chuck that can be removed.

In order to achieve the above object, an electrostatic attraction apparatus according to one aspect of the present invention has a plurality of convex portions capable of supporting a substrate on the top surface and concave portions around the convex portions on the surface. An electrostatic attraction apparatus comprising: a formed dielectric plate; an electrode provided inside the dielectric plate; and a first external power source that applies a substrate attraction voltage to the electrode,
The convex portion is provided with a conductor coating on at least the top surface of the convex portion,
The first external power source includes a substrate desorption voltage power source capable of applying a reverse voltage having a polarity opposite to the substrate adsorption voltage applied to the electrode to the electrode when the substrate is desorbed.
The conductor coating is provided with a second external power supply provided with a substrate desorption voltage power source capable of applying a reverse voltage having a polarity opposite to the substrate adsorption voltage applied to the electrode when the substrate is detached. It is connected to a power source.

In the above electrostatic adsorption device, the plurality of convex portions supporting the substrate on the top surface have a height of 35 μm or less, and the top surface has an Ra (centerline average roughness) of 0.2 μm or less. The total surface area is formed so as to have a ratio of 10% or less with respect to the total planar area of the dielectric plate.

In the above electrostatic chuck, the substrate has a volume resistivity of 10 ¹⁴ Ω · cm or less, and an insulating property whose Ra (center line average roughness) of the contact surface with the convex portion is 0.05 μm or less. It is a substrate.

According to the electrostatic attraction apparatus of the present invention, when adsorbing a substrate, the substrate is adsorbed by a Johnson Rahbek force generated between the convex portion and the substrate and a Coulomb force generated between the concave portion and the substrate. Is possible. When the substrate is detached (detached), a reverse voltage applied to the electrode during substrate adsorption is applied to the first external power source connected to the electrode and the second external power source connected to the conductive film. As a result, the back surface of the substrate and the conductor coating have the same potential. As a result, the residual attracting force of the substrate disappears, and the substrate can be smoothly removed from the electrostatic chuck in a short time.

Other features and advantages of the present invention will become apparent from the following description with reference to the accompanying drawings. In the accompanying drawings, the same or similar components are denoted by the same reference numerals.

The accompanying drawings are included in the specification, constitute a part thereof, show an embodiment of the invention, and are used to explain the principle of the invention together with the description.

The cross-sectional schematic diagram of the sputtering device provided with the electrostatic attraction apparatus which concerns on an example of this invention. The partial expanded sectional schematic diagram of the electrostatic attraction apparatus which concerns on an example of this invention. The top view of the electrostatic chuck of FIG.1 and FIG.2. The figure which shows the state of the electric charge of the surface of the conductor film of the electrostatic chuck shown in FIG. 2, and the back surface of a board | substrate at the time of adsorption | suction of a board | substrate. The figure which shows the state of the electric charge of the surface of the conductor film of the electrostatic chuck shown in FIG. 2, and the back surface of a board | substrate at the time of detachment | leave of a board | substrate. The figure which shows the state of the electric charge of the electrostatic chuck shown by FIG. 2 at the time of adsorption | suction of a board | substrate. The figure which shows the state of the electric charge of the electrostatic chuck shown in FIG. 2 at the time of detachment | leave of a board | substrate. The figure which shows the equivalent circuit at the time of adsorb | sucking a glass substrate using the conventional electrostatic adsorption apparatus. The figure which shows the equivalent circuit at the time of adsorb | sucking a glass substrate using the electrostatic adsorption apparatus of this invention. The figure which shows the relationship between the adsorption | suction voltage of a convex part and a recessed part after turning off an electrode power supply, and time at the time of detachment | leave of a glass substrate. The figure which shows the relationship between the electrostatic attraction force which acts on the convex part and recessed part after turning off the power supply of an electrode at the time of detachment | leave of a glass substrate, and time. The figure which shows the series circuit of the capacitor | condenser C and the resistance R. FIG. The figure which shows the state of the voltage at the time of applying the voltage Vb with the direct-current power supply B to the circuit of FIG. 8A initially, and making it a ground (GND) after that. The figure which shows the state of a voltage at the time of applying the reverse voltage Va of the voltage Vb by DC power supply A after applying the voltage Vb by DC power supply B initially to the circuit of FIG. 8A.

Hereinafter, embodiments of the present invention will be described. The components are exemplary. The case where the electrostatic attraction apparatus of the present invention is applied to a sputtering apparatus will be described as an example. FIG. 1 is a schematic cross-sectional view of a sputtering apparatus provided with an electrostatic attraction apparatus according to an example of the present invention, and FIG. 2 is a partially enlarged schematic cross-sectional view of the electrostatic attraction apparatus according to an example of the present invention.

First, the outline of the sputtering apparatus will be described with reference to FIG. The sputtering apparatus shown in FIG. 1 includes a container 1 whose inside can be decompressed by an external exhaust mechanism (not shown), and a target 3 provided on the ceiling of the container 1 via a ring-shaped insulating member 2. Yes. A magnet 5 is provided on the yoke plate 4 on the back side of the target 3. The target 3 is connected to a sputtering power source 6 for applying a voltage.

At the position facing the target 3, an electrostatic chuck 8 is provided on the substrate temperature adjusting unit 7 fixed to the bottom of the container 1, and the substrate 9 is placed on the electrostatic chuck 8. A cylindrical shield member 10 is disposed along the inner surface of the peripheral wall of the container 1 between the target 3 and the electrostatic chuck 8.

The substrate temperature adjusting unit 7 is a member that controls the temperature of the substrate 9 via the electrostatic chuck 8, and includes a thermocouple 12 and a heating / cooling unit 13 connected to the temperature control power supply mechanism 11. In the substrate temperature adjusting unit 7, the temperature control power supply mechanism 11 operates the heating / cooling unit 13 based on the temperature detected by the thermocouple 12 to heat or cool the electrostatic chuck 8.

The electrostatic chuck 8 provided on the substrate temperature adjusting unit 7 includes a dielectric plate 14 whose surface (upper surface) is embossed, an electrode 15 provided inside the dielectric plate 14, and a constant electrode 15. And an external power supply 16b for applying a voltage.

On the surface of the dielectric plate 14, a plurality of convex portions 17a and peripheral concave portions 17b are formed by embossing. In addition, an outer peripheral ridge 18 is formed on the peripheral edge of the front surface side of the dielectric plate 14 so as to surround the formation region of the convex portion 17a and the concave portion 17b. The convex part 17a and the outer peripheral ridge part 18 are those on which the substrate 9 is placed on the top surface, and have substantially the same height.

1 except for the concave portion 17b shown in FIG. 1, a conductor coating 19 is formed on each convex portion 17a so as to cover at least the top surface. Each conductor coating 19 has irregularities that cause a Johnson Rabeck force between the substrate 9 and the conductor coating 19 by applying a voltage to the electrode 15 described below. The unevenness of the conductor coating 19 functions as a Johnson Rabeck force generator. In addition, each conductor coating 19 may cover not only the top surface of each projection 17a but also the side surface of each projection 17a, but the conductor coating 19 is not provided in the recess 17b portion. Each concave portion 17b is electrically independent from the conductor coating 19 formed on each convex portion 17a.

In the illustrated example, a conductor coating 19 is also formed on the top and side surfaces of the outer peripheral ridge 18. The conductor coating 19 formed on the top surface of the outer peripheral ridge portion 18 is preferably provided to facilitate the alignment of the entire height of the outer peripheral ridge portion 18 and the entire height of the convex portion 17a, but may be omitted. it can.

The electrode 15 is a unipolar electrode and is connected to an external power source 16b which is a DC power source via a switch 20b, and a constant negative voltage is applied by turning on the switch 20b. Although the illustrated electrode 15 is a monopolar electrode, it is divided into an inner peripheral side and an outer peripheral side of the dielectric plate 14 to form a bipolar electrode, and a negative voltage is applied to one of them and a positive voltage is applied to the other. You can also Further, the electrode 15 has a smaller diameter than the outer peripheral ridge portion 18, and is positioned only below the region where the convex portions 17 a and the concave portions 17 b are provided, and is not positioned immediately below the outer peripheral ridge portion 18. It has become a thing. Since the electrode 15 is not located below the outer peripheral protrusion 18, the outer peripheral protrusion 18 does not contribute to the adsorption of the substrate 9.

As described above, the substrate 9 is placed on the top surfaces of the convex portion 17a and the outer peripheral ridge portion 18, and the region surrounded by the outer peripheral ridge portion 18 is between the substrate 9 and the dielectric plate 14. In addition, a gap is formed by the recess 17b. A gas supply source 22 is connected to the gap via a gas supply path 21 so that gas (for example, argon gas) can be supplied to the gap. By supplying the gas to the gap, the heat of the substrate temperature adjusting unit 7 is transmitted to the substrate 9 by the heat conduction of the electrostatic chuck 8 and the gas in the gap so that the substrate 9 can be maintained at a predetermined temperature. It has become.

Next, the electrostatic adsorption device will be further described with reference to FIG. FIG. 2 is a partial enlarged cross-sectional schematic view of an electrostatic attraction apparatus according to an example of the present invention. An external power source 16a is connected to the conductor film 19 covering at least the top surface of each convex portion 17a via a switch 20a. As described above, the electrode 15 is connected to the external power supply 20b through the switch 20b.

The

external power supplies

16a and 16b are respectively a DC power supply 16a1 and 16b1, a DC power supply 16a2 and 16b2 that generate a reverse voltage having a polarity opposite to that generated by the DC power supplies 16a1 and 16b1, and a ground terminal 16a3 and 16b3. Consists of The voltages output from the

external power supplies

16a and 16b can be switched by the

switches

20a and 20b. In FIG. 1, the ground terminals 16a3 and 16b3 are not shown. For example, when the DC power supplies 16a1 and 16b1 function as substrate adsorption voltage power supplies, the DC power supplies 16a2 and 16b2 function as substrate desorption voltage power supplies.

FIG. 3 is a plan view of the electrostatic chuck 8 shown in FIGS. 1 and 2. As shown in FIG. 3, the convex portion 17 a and the concave portion 17 b are formed radially from the central axis of the electrostatic chucking stage 8 and continuously from the central axis of the electrostatic chucking stage 8. A circumferential portion 272 that extends. The circumferential portion 272 is formed on a part of the radial portion 271. The convex part 17a and the outer peripheral ridge part 18 are those on which the substrate 9 is placed on the top surface, and have substantially the same height. The convex portions 17 a and the concave portions 17 b formed in the radial portion 271 and the circumferential portion 272 are covered with the conductor film 19. The concave portions 17 b formed other than the radial portion 271 and the circumferential portion 272 are not covered with the conductor film 19. The planar shape of the attracting surface of the electrostatic chuck 8 is circular as a whole as shown in FIG. The substrate 9 is also circular, and the diameters of both are substantially the same.

FIG. 4A is a diagram showing a state of charges on the surface of the conductor coating 19 and the back surface of the substrate 9 of the electrostatic chuck shown in FIG. FIG. 4B is a diagram showing the state of electric charges on the surface of the conductor coating 19 and the back surface of the substrate 9 of the electrostatic chuck shown in FIG. The electrostatic chuck 8 will be further described with reference to FIGS. 1 to 4B. The convex portion 17a is usually cylindrical and preferably has a diameter of 2.0 mm or less. The lower limit is determined by the required mechanical strength of the convex portion 17a and processing limitations, but is generally about 0.3 mm. When the diameter of the convex portion 17a is increased, it is difficult to perform rapid charge removal when the substrate 9 is detached. Although the detailed cause is unknown, it is thought that the rapid neutralization is caused by the large number of contact points between the conductor film 19 formed on the top surface of the convex portion 17a and the substrate 9. When the diameter of the convex portion 17a is small, the maximum surface roughness (Ry) in the unevenness of the conductor coating 19 functioning as the Johnson Rabeck force generating portion is stochastically reduced, and the surface smoothness of the conductor coating 19 is increased. It is considered that the contact point between the substrate 9 and the conductor coating 19 increases. Further, since the smoothness of the conductor coating 19 is increased, the interval between the microscopic gaps between the substrate 9 and the conductor coating 19, that is, the gap between the irregularities functioning as the Johnson Rabeck force generator is also reduced. Accordingly, the Johnson Rabeck force acting between the substrate 9 and the conductor coating 19 is also increased.

The surface of the conductor film 19 on the convex portion 17a preferably has a smooth surface in order to obtain a good adsorption action and separation action, and Ry (maximum surface roughness) is 2.5 μm or less, and Ra ( The centerline average roughness is preferably 0.2 μm or less. In reality, a completely smooth surface cannot be formed, so there is no particular lower limit. However, from the practical smoothing limit, Ry is 0.2 μm or more and Ra is 0.02 μm or more. Further, the volume resistivity of the substrate 9 is preferably 10 ¹⁴ Ω · cm or less. Moreover, it is preferable that Ra (centerline average roughness) of the board | substrate 9 of a contact surface with the convex part 17a is 0.05 micrometer or less.

As for the height of the convex part 17a and the outer periphery protrusion part 18, it is preferable that height is 35 micrometers or less in the range in which the adsorbed board | substrate 9 does not contact a recessed part. By reducing the height of the convex portion 17a and the outer peripheral ridge portion 18, the Coulomb force acting between the substrate 9 and the concave portion 17b can be increased. The lower limit of the height is generally about 6.5 μm.

The convex portion 17a has a total area of the top surface of the convex portion 17a of 1% or more and 10% of the total planar area of the electrostatic chuck 8 in order to obtain an appropriate suction force and quick charge removal. It is preferable to be formed so as to have the following ratio.

The conductor coating 19 is made of a metal, metal oxide, metal nitride or the like, which is an electrical conductor having a specific resistance of 10 ⁻⁴ μΩ · cm or less, and has a specific resistance of 400 μΩ · cm or less. preferable. In particular, the specific resistance is preferably 350 μΩ · cm or less. The electrostatic chuck 8 according to the present embodiment is configured as a bulk (plate). For this reason, it is not necessary to use different types of insulating materials as in the case of the separation mask of Patent Document 4 described above. The material of the electrostatic chuck 8 has a volume resistivity capable of exhibiting a Johnson Rahbek force of 10 ⁸ to 10 ¹⁰ Ω · cm. The conductor film 19 accumulates the same charge as the dielectric surface of the electrostatic chuck 8, and when the substrate 9 is detached from the electrostatic chuck 8, the back surface of the substrate 9 and the conductor film 19 are made to have the same potential so that the substrate remains. Eliminates adsorption power. By eliminating the residual attracting force of the substrate 9, it is possible to smoothly remove the substrate from the electrostatic chuck 8, that is, to improve the stability of substrate separation.

In particular, by setting the specific resistance of the conductor coating 19 to 350 μΩ · cm or less, for example, the conductor coating 19 on the back surface of the substrate and the surface of the electrostatic chuck can easily act so as to have the same potential. As a result, it is possible to eliminate the residual attracting force of the discharged substrate and to smoothly remove the substrate from the electrostatic chuck (detachment of the substrate).

Conversely, if the specific resistance is high, the charge on the back surface of the substrate loses its escape field, and as a result, the residual adsorption force remains on the substrate, so that the separation of the substrate from the electrostatic chuck becomes unstable.

Examples of the structure of the conductor coating 19 include metals such as titanium and tungsten, and oxides or nitrides thereof. Titanium, tungsten, and other materials are resistant to thermal distortion among metals, and are excellent in wear resistance and are not easily deformed. Therefore, they are rubbed due to contact between the substrate and the conductive coating 19 of the electrostatic chuck, and differences in linear expansion. Particles resulting from factors such as these can be suppressed, and wear resistance can be improved.

The conductor film 19 can be formed by a film forming method such as sputtering or ion plating. The thickness of the conductor coating 19 is preferably 1.5 μm or less in order to suppress the resistance in the film thickness direction of the conductor coating 19 to about 10Ω. When the thickness of the conductor film 19 exceeds 1.5 μm, the resistance of the conductor film 19 increases and film peeling due to film stress tends to occur. A practical lower limit is about 0.5 μm.

In FIG. 1, a substrate transfer robot, a loading / unloading gate, a lift pin for placing and removing the substrate 9 on the electrostatic chuck 8, a mechanism related to discharge generation, a discharge gas introduction mechanism, and the like are illustrated. It is omitted.

In the sputtering apparatus of FIG. 1, the substrate 9 is loaded and placed on the electrostatic chuck 8 in the container 1 from the loading / unloading gate by the substrate transfer robot. When the inside of the container 1 is put into a predetermined vacuum atmosphere, the switch 20 b is turned on and a voltage is applied to the electrode 15, different charges are accumulated on the surface of the dielectric plate 14 and the conductor coating 19 and the back surface of the substrate 9. FIGS. 4A and 5A show the state of charge on the surface of the conductor film 19 and the back surface of the substrate 9 when the switch 20b is turned on. Thereby, a spatial Coulomb force acts between the concave portion 17b on the surface of the dielectric plate 14 and the back surface of the substrate 9, and a fine gap is formed between the conductor coating 19 on the top surface of the convex portion 17a and the back surface of the substrate 9. The Johnson Rabeck force acts on both sides. The substrate 9 is firmly attracted to the electrostatic chuck 8 by the space Coulomb force and the Johnson Rabeck force.

After adsorbing the substrate 9 to the electrostatic chuck 8, a necessary amount of gas is supplied from the gas supply source 22 to the gap between the electrostatic chuck 8 and the substrate 9. At the same time, the heating / cooling unit 13 is operated by the temperature control power supply mechanism 11 to supply the discharge gas into the vessel 1 while keeping the temperature of the substrate 9 constant, and the sputtering power supply 6 is turned on to perform sputtering.

After the sputtering is completed, the sputtering power source 6 is turned off, and the switch 20b is turned off to stop the voltage application to the electrode 15. Then, the back surface of the substrate 9 and the conductor film 19 try to be at the same potential via the contact points between the conductor film 19 on the top surface of the plurality of convex portions 17a and the back surface of the substrate 9, and the charge is thereby eliminated. In addition, the conductor coating 19 on the top surface of the plurality of convex portions 17 a also tends to have the same potential as the substrate 9. The state of this charge is shown in FIGS. 4B and 5B. However, the substrate 9 cannot be detached from the electrostatic chuck 8 only by turning off the sputtering power source 6 and further turning off the switch 20b.

This point will be described with reference to FIGS. 6A and 6B. FIG. 6A shows an equivalent circuit when a glass substrate (substrate 9) is adsorbed using a conventional electrostatic attraction apparatus. FIG. 6B shows an equivalent circuit when a glass substrate is adsorbed using the electrostatic attraction apparatus of the present invention. Symbols in the equivalent circuits of FIGS. 6A and 6B are as shown below.

C1 and R1 are a capacitor and a resistor under the electrode 15. C2 and R2 are capacitors and resistors above the electrode 15. C3 and R3 are capacitors and resistors of the convex portion 17a. C4 and R4 are a capacitor and a resistance of the conductor film 19 at a portion in contact with the glass substrate (substrate 9). C5 is a capacitor between the dielectric recess 17b and the glass substrate (substrate 9). C6 and R6 are a capacitor and a resistor of the glass substrate (substrate 9) in a portion in contact with the conductor coating 19. C7 and R7 are capacitors and resistors between the glass substrate (substrate 9) and the concave portion 17b. A second external power source 16 b connected to the conductor coating 19 is a first external power source connected to the electrode 15.

It is assumed that the glass substrate (substrate 9) is connected to the ground via plasma. The glass substrate (substrate 9) is an insulating material on which an insulating thin film such as a SiN film (for example, a volume resistivity of 10 ¹⁴ Ω · cm or less) having a larger volume resistivity than that of a normal glass substrate is formed. Assume a substrate.

As described above, the Johnson Rabeck force is considered to be generated by microscopic irregularities on the surfaces of the conductor coating 19 and the substrate 9. When this is shown by the equivalent circuit shown in FIGS. 6A and 6B, the substrate 9 and the conductor coating 19 are approximately Ra (center line average roughness) formed by unevenness on both surfaces of the conductor coating 19 and the substrate 9. It is considered that the electrodes are connected by a capacitor C4 having a distance between the electrodes. That is, as shown in FIGS. 6A and 6B, the conductor film 19 and the substrate 9 are equivalent to the parallel circuits C6 and R6, the parallel circuits C4 and R4, and the parallel circuits C3 and R3 connected in series. It is considered a circuit.

On the other hand, a gap is formed between the substrate 9 and the recess 17b, and the substrate 9 is attracted to the electrostatic chuck 8 by a Coulomb force generated between the substrate 9 and the recess 17b. In this state, the portion of the substrate 9 and the recess 17b can be considered as an equivalent circuit in which the parallel circuits C7, R7, C5 and the parallel circuits C2, R2 are connected in series. One end of the parallel circuits C2 and R2 and the other end of the parallel circuits C3 and R3 are connected by a terminal VB, and the other end VA of the parallel circuits C2 and R2 is connected to the ground via the parallel circuits C1 and R1. It can be considered as an equivalent circuit.

FIG. 7A shows the relationship between the attracting voltage of the convex portion 17a and the concave portion 17b and time when the switch 20b is connected to the ground terminal 16b3 after the power of the electrode 15 is turned off when the glass substrate (substrate 9) is detached. Show. In FIG. 7A, the dotted line indicates the convex voltage, and the solid line indicates the concave voltage. FIG. 7B shows the electrostatic attraction force and time acting on the convex portions 17a and the concave portions 17b when the switch 20b is connected to the ground terminal 16b3 after the power of the electrode 15 is turned off when the glass substrate (substrate 9) is detached. The relationship is shown. In FIG. 7B, the dotted line (broken line) indicates the convex portion adsorption force, the solid line indicates the concave portion adsorption force, and the alternate long and short dash line indicates the total wafer adsorption force (substrate adsorption force) of the concave portion and the convex portion.

The parameter values used for the calculations in FIGS. 7A and 7B were set as follows. Assuming that the capacitance of the glass substrate (substrate 9) is 4 × 10 ⁻⁷ F, which is larger than the actual capacitance, the height of the convex portion is 8.5 μm, and the resistivity of the glass substrate (substrate 9) is 1 × 10 ⁺¹¹ Ω The resistivity of the electrostatic chuck 8 is 1 × 10 ⁺¹¹ Ω · cm, the relative dielectric constant of the electrostatic chuck 8 is 9, the distance from the electrode 15 of the electrostatic chuck to the surface of the substrate 9 is 1 mm, and the protrusion 17a Was 1.5% of the entire surface of the electrostatic chuck 8 and the area of the electrostatic chuck 8 was 65411 mm ² .

At this time, the equilibrium voltage applied to the concave portion is 0.85 V and the equilibrium voltage acting on the convex portion is 60 mV from the calculation. Further, the contact resistance at the convex portion was 6.5 × 10 ⁺⁷ Ω · cm, and the electrode distance was d = 0.05 μm. Johnson Rabeck (JR) force works between these electrodes,
F = 1/2 × ε ₀ × (V / d) ² × S
When calculated by the above formula, F = 6 × 10 ⁻³ N. A force of 3 × 10 ⁻³ N works in the recess. From this state, FIG. 7B shows changes in each voltage and changes in the suction force when the suction voltage is set to 0V.

As shown in FIG. 7A, immediately after the adsorption voltage was set to 0V, the “recess voltage” was 0.85V and the “convex voltage” was 0.06V. That is, the “convex voltage” was about 1/10 of the “concave voltage”. Further, the suction voltage of the recess 17b becomes 0 V after a predetermined time (1 sec). However, the adsorption voltage of the convex portion 17a does not become 0 V even after a predetermined time has elapsed (about 24 hours). That is, the attracting voltage of the convex portion 17a does not become 0V unless one day or more elapses, and the glass substrate cannot be detached from the electrostatic chuck during this period.

As shown in FIG. 7B, immediately after the adsorption voltage is set to 0 V, the electrostatic adsorption force of the convex portion 17a is 6 × 10 ⁻³ (Pa · m ² ), and the electrostatic adsorption force of the concave portion 17b is 3 × 10 ⁻³ ( Pa · m ² ). That is, the electrostatic attraction force of the convex portion 17a was about twice the electrostatic attraction force of the concave portion 17b. Immediately after the suction voltage is set to 0 V, the total wafer suction force of the concave portion and the convex portion indicated by the one-dot chain line in FIG. 7B is 9 × 10 ⁻³ (Pa · m ² ). Further, the electrostatic attraction force of the concave portion 17b becomes 0 (Pa · m ² ) when a predetermined time elapses (about 1 sec). However, the electrostatic attraction force of the convex portion 17a does not become 0 (Pa · m ² ) even when a predetermined time has elapsed (about 24 hours). Therefore, the total electrostatic attraction force of the convex portion 17a and the concave portion 17b does not become 0 (Pa · m ² ) even when a predetermined time elapses (about 24 hours). As time elapses, the value of the convex portion adsorption force becomes dominant among the total wafer adsorption force of the concave portion and the convex portion. Because of this electrostatic attraction force, the glass substrate cannot be detached simply by connecting the switch 20b to the ground terminal 16b3 after the electrode 15 is turned off. Since the volume resistance value of the glass substrate changes in a large range of 10 ¹⁰ to 10 ¹⁴ Ω · cm, FIGS. 7A and 7B are examples of calculation. Moreover, the value of 0V includes the meaning of a voltage that can be ignored as the attractive force.

This point will be described with reference to FIGS. 8A to 8C. FIG. 8A shows a series circuit of a capacitor C and a resistor R. FIG. 8B shows a voltage state when the voltage Vb is initially applied to the series circuit of the capacitor C and the resistor R shown in FIG. 8A by the direct-current power source B and then is grounded (GND). As shown in FIG. 8B, the voltage V does not quickly become zero simply by using the ground (GND). This is presumably because a transient phenomenon determined by the time constant of CR continues. In FIG. 8C, a voltage Vb is first applied by the DC power supply B to the series circuit of the capacitor C and the resistor R shown in FIG. 8A, and then a voltage Va having a polarity opposite to that of the voltage Vb is applied by the DC power supply A. Shows the state of the voltage V. Compared to the ground (GND) in FIG. 8B, in the case of FIG. 8C, the voltage V quickly approaches zero.

From the above, the relaxation time is expected to be much slower in the part where the Johnson Rabeck (JR) force is applied because of the high resistance in parallel. Further, since a different adsorption force of Johnson Rabeck (JR) force and Coulomb force acts on the substrate, a slight voltage remains in the case of Johnson Rabeck (JR) force in which the residual charge effectively acts as the adsorption force. It is assumed that the influence is great when the substrate 9 is detached.

As described above, the substrate 9 is firmly electrostatically caused by the Coulomb force generated between the concave portion 17 b and the substrate 9 and the Johnson Rahbek force generated between the convex portion 17 a (unevenness of the conductor coating 19) and the substrate 9. It is to be adsorbed by the chuck. As shown in FIGS. 7A and 7B, since the Coulomb force generated in the concave portion 17b is a force inversely proportional to the square of the distance, the Johnson Rabeck force generated in the convex portion 17a can obtain a large adsorption force with a smaller voltage. . However, the time constant between the substrate 9 and the convex portion 17a is larger than the time constant between the substrate 9 and the concave portion 17b. For this reason, the time when the residual charge of the convex portion 17a becomes zero takes much time compared with the time when the residual charge of the concave portion 17b becomes zero. For this reason, when the same reverse voltage is applied to the concave part 17b and the convex part 17a, the relaxation of the attracting force is slower in the convex part 17a than in the concave part 17b. Accordingly, the external power supply 16b connected to the electrode 15 when the substrate 9 is detached is switched to a voltage (16b2) opposite to the voltage (16b1) when the substrate 9 is attracted by the switch 20b, and the reverse voltage is supplied to the electrode 15. In the method disclosed in Patent Document 4, a voltage having a reverse polarity is applied to the same electrode 15 as the electrode 15 for generating the attraction force of the substrate 9, so that the residual voltage generated in the convex portion 17a and the concave portion 17b is eliminated at the same time. It is difficult to apply an appropriate reverse voltage to In addition, in order to eliminate the residual voltage generated in the convex portion 17a and the concave portion 17b, when the remaining charge in the concave portion 17b disappears by applying a larger reverse voltage to the electrode 15 for a certain time, the residual charge remains in the convex portion 17a. End up. On the contrary, when a reverse voltage is applied to the electrode 15 for a certain period of time so as to eliminate the residual charge in the convex portion 17a, the residual charge remains in the concave portion 17b. For this reason, only by applying a reverse voltage to the electrode 15 for a certain period of time, the residual charges on the convex portions 17a and the concave portions 17b of the substrate cannot be eliminated simultaneously.

This point will be described with reference to the equivalent circuit of FIG. 6A. When a reverse voltage is applied to the electrode 15 in order to relax the voltage between the terminal VB and the terminal VD, the voltage of the capacitor C5 between the recess 17b and the substrate 9 is quickly increased. When a reverse voltage is applied for a certain period of time or less, an attracting force is generated again between the recess 17b and the substrate 9 due to the applied reverse voltage. By adjusting the reverse voltage application time, the voltage between the terminal VB and the terminal VE can be reduced. At that time, the voltage between the terminal VC and the terminal VD remains to some extent because of the parallel connection with a large time constant, and the adsorption power remains. ing. If the time for applying the reverse voltage is adjusted until the voltage between the terminal VC and the terminal VD becomes extremely small, a voltage having a reverse voltage polarity is generated between the terminal VB and the terminal VE. End up. Thus, it is difficult to eliminate the voltage between the terminal VC and the terminal VD and the voltage between the terminal VB and the terminal VE at the same time.

On the other hand, when the substrate 9 is attracted, the voltage (16b1) is supplied to the electrode 15 by the external power supply 16b. When the substrate is detached, when the substrate 9 is detached, the switch 20b is turned off to stop the voltage application to the electrode 15. In the method of Patent Document 2 in which the conductor coating 19 is connected to the ground terminal (16a3) via the switch 20a, when the resistance of the substrate 9 is large, a large adsorbing force is generated at the substrate contact portion due to the Johnson Rabeck force. There is a problem in that it takes time to eliminate the convex portion adsorption force because current does not flow to the substrate 9 side simply by dropping to the ground.

This point will be described with reference to the equivalent circuit of FIG. 6A. When R6 is large, the charge of C4 and C6 is easily released by dropping from the terminal VC to the ground, but when C4, C6, R4 and R6 are large, Because it is a constant, it takes a long time for the charge to escape. On the other hand, as in the present invention, the voltage (16b1) is supplied to the electrode 15 by the external power supply 16b when the substrate 9 is attracted, and the external power supply 16b connected to the electrode 15 is removed by the switch 20b when the substrate 9 is detached. If the voltage (16b1) at the time of adsorption of the substrate 9 is switched from the reverse voltage (16b2), the reverse voltage is supplied to the electrode 15, and the conductor coating 19 is connected to the terminal 16a2 of the external power source 16a via the switch 20a. Since the reverse voltage opposite to that when the substrate 9 is attracted is supplied to the convex portion 17a, the substrate 9 can be detached more quickly than in the prior art. Since the state of this charge is as shown in FIG. 5B, no problem occurs in terms of separation from the high-resistance glass substrate (substrate 9).

This point will be described with reference to the equivalent circuit of FIG. 6B. In the case of the equivalent circuit of FIG. 6B, when the substrate 9 is attracted, the substrate 9 is attracted by applying the voltage Va to the electrode 15 from the external power source 16b. When the substrate 9 is detached, the reverse voltage Vb at the time of adsorption can be applied not only to the terminal VA but also to the terminal VC by the external power source 16a. Thereby, the time for which the residual charge in the recess 17b is zero is determined by the reverse voltage Vb applied to the terminal VA between the terminals VA and VB and between the terminals VB and VE. Further, the time during which the residual charge of the convex portion 17a becomes zero is determined by the reverse voltage Vb applied to the terminal VC between the terminal VC and the terminal VD. Thus, in the present invention, the residual charge in the concave portion 17b is made zero by the reverse voltage Vb applied to the terminal VA, and the residual charge in the convex portion 17a is made zero by the reverse voltage Vb applied to the terminal VC. It is possible.

Next, as a substrate 9, an electrostatic chuck having a glass substrate (substrate 9) having a volume resistivity of 10 ¹² Ω · cm at room temperature, a conductor coating (specific resistance 10 ⁻⁴ μΩ · cm, Ra 0.2 μm), and TiN Assuming 8 (volume resistivity 10 ⁸ Ω · cm, ceramic), how to operate the electrostatic chuck shown in FIGS. 1, 2, and 6B will be described.

When the substrate 9 is attracted, a voltage 16b1 (10 V to 10 kV) is supplied to the electrode 15 from the external power source 16b for about 1 to 10 minutes to attract the substrate 9. When the substrate is detached, a voltage 16b2 (10 V to 10 kV) is supplied to the electrode 15 by the external power supply 16b for about 1 to 10 minutes, and a voltage 16a2 (10 V to 10 kV) is supplied to the terminal VC and the external power supply 16a for about 1 to 10 minutes. After the supply to the extent, the substrate 9 was detached.

The present invention is not limited to the above embodiment, and various changes and modifications can be made without departing from the spirit and scope of the present invention. Therefore, in order to make the scope of the present invention public, the following claims are attached.

This application claims priority on the basis of Japanese Patent Application No. 2010-289263 filed on Dec. 27, 2010, the entire contents of which are incorporated herein by reference.

Claims

A plurality of convex portions capable of supporting the substrate on the top surface, a dielectric plate formed on the surface with concave portions around the convex portions, electrodes provided inside the dielectric plate, and An electrostatic attraction apparatus comprising a first external power source for applying a substrate attraction voltage to the electrode,
The convex portion is provided with a conductor coating on at least the top surface of the convex portion,
The first external power source includes a substrate desorption voltage power source capable of applying a reverse voltage having a polarity opposite to the substrate adsorption voltage applied to the electrode to the electrode when the substrate is desorbed.
The conductor coating is provided with a second external power supply provided with a substrate desorption voltage power source capable of applying a reverse voltage having a polarity opposite to the substrate adsorption voltage applied to the electrode when the substrate is detached. An electrostatic adsorption device characterized by being connected to a power source.
The plurality of convex portions that support the substrate on the top surface have a height of 35 μm or less, the top surface Ra (centerline average roughness) is 0.2 μm or less, and the total area of the top surfaces is 2. The electrostatic attraction apparatus according to claim 1, wherein the electrostatic attraction apparatus is formed so as to have a ratio of 10% or less with respect to a total plane area of the dielectric plate.
The substrate is an insulating substrate having a volume resistivity of 10 14 Ω · cm or less and an Ra (centerline average roughness) of a contact surface with the convex portion of 0.05 μm or less. The electrostatic attraction apparatus according to claim 1.