JPH09102536A - Electrostatic attraction apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrostatic attraction apparatus capable of attracting and detaching a wafer by turning a switch on or off, respectively, regardlessly of the presence of plasma, of controlling temperature, of allowing little foreign matters adhering to a wafer processing target surface and of achieving excellent throughput. SOLUTION: A through hole is provided in a conductive electrode 1. A pin electrode 7 is disposed in the through hole so as to place the surface of the pin electrode 7 at a higher position than that of the surface of the conductive electrode 1. A dielectric film 5 is formed on surfaces of the conductive electrode 1 and the pin electrode 7 to provide a flat surface. DC voltage 8 is applied between the electrode 1 and the pin electrode 7 to thereby electrostatically attract a wafer 6 on the resultant flat surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for attracting an object to be conveyed by using electrostatic force.

[0002]

2. Description of the Related Art A method of holding an object to be transferred by using electrostatic force is used particularly for transferring a wafer for manufacturing a semiconductor device and fixing the wafer during each process. As a holding method for carrying or fixing the wafer, a mechanical holding method using a clamp or the like can be considered. However, using electrostatic force has many advantages in holding the semiconductor wafer. For example, since there is no mechanical contact with the processing surface of the wafer, there is no contamination of the wafer by abrasion powder, etc. In addition, the processing accuracy is ensured, the contact with the adsorption surface becomes more reliable, the thermal conductivity is improved, and the temperature control of the wafer is facilitated.

The circuit configuration of an electrostatic chucking device used for fixing a wafer during processing is such that a DC voltage is applied to a dielectric containing a unipolar electrode, which is usually called a monopole.
The method of grounding the conduction of the voltage applied to the electrodes via the plasma being processed is often used. However, this method has some problems because the wafer cannot be fixed in the absence of plasma. For example, in the dry etching process, the temperature rises because ions, electrons, and radicals enter the wafer. Therefore, in order to improve the etching characteristics, a gas is passed to the back surface of the wafer to cool it. In the above method, the wafer cannot be adsorbed in the absence of plasma, so that cooling cannot be performed immediately after the start of processing and resist burning occurs. In addition, if the plasma is cut off after the processing is completed, the wafer cannot be brought into conduction, and the electric charges accumulated on the wafer remain to generate a residual adsorption force, which causes a problem that the next operation cannot be performed.
Furthermore, if measures such as flowing a gas for static elimination to remove the residual adsorptive power are taken, there is a problem that the time required for this causes a decrease in the throughput of the apparatus.

Therefore, a method has been devised in which an electric circuit is constructed with respect to a DC voltage applied to the wafer to generate an attraction force. Conventionally, the circuit configuration for grounding when a single-pole type electrostatic adsorption device is used for fixing the wafer of the etching device is the method of pressing the conductor to the edge of the wafer to ground it, or the peripheral part of the wafer surface. A method of contacting a ring-shaped ground electrode has been proposed. An example is JP-A-5-183.
It is disclosed in Japanese Patent No. 043.

[0005]

An electrostatic adsorption device for fixing a wafer during a process such as etching is such that a unipolar electrode is embedded inside a dielectric to apply a DC voltage component to a plasma for processing. The method of constructing a circuit by grounding it through electrical conductivity and the chamber is simple and widely used. However, in this method, the wafer cannot be fixed in the absence of plasma, so that the cooling gas cannot be flowed to cool the back surface of the wafer immediately after the processing is started, and the temperature controllability of the processing start is deteriorated. After the etching process, the wafer floats in a circuit-like manner, and the electric charge stored on the wafer cannot escape, and the residual adsorption force is large.If a charge-eliminating gas is introduced to remove the electric charge stored on the wafer after the etching process, However, there is a problem that the time required for that deteriorates the throughput of the apparatus.

Therefore, a chucking method is required irrespective of the presence or absence of plasma. In this method, a conductive member is brought into contact with either the outer periphery of the processing surface of the wafer, an arbitrary back surface of the wafer or the side surface of the wafer. A method of giving the ground potential can be considered.

However, as in the case of Japanese Patent Laid-Open No. 5-183043, in the method of contacting the ground electrode with the outer peripheral portion of the processing surface of the wafer or any of the back surface or side surface, the minute amount generated at the contact portion Wear particles cause element destruction,
There is a problem that causes a decrease in yield.

An object of the present invention is to provide an electrostatic chucking device capable of sucking and holding a wafer irrespective of the presence or absence of plasma and rapidly reducing the residual chucking force during desorption. Another object of the present invention is to provide an electrostatic attraction device in which no foreign matter is generated on the processing surface of the wafer at this time.

[0009]

In order to achieve the above-mentioned object, the present invention provides a second conductive electrode in a state of being electrically insulated in a first electrode having a through hole, the surface of which is a second conductive electrode. It is inserted so as to protrude from the first conductive electrode or be recessed. Then, a dielectric film is formed on these surfaces by a thermal spraying method, a vapor deposition method or the like so that the surface becomes flat, and a voltage is applied between the first electrode and the second electrode. In addition, a through hole is provided on the surface of the first conductive electrode having a dielectric film formed on the surface, and an insulating cylinder made of an insulating material is attached to the through hole. The surface of the insulating cylinder is higher than the surface of the dielectric film. A contact terminal is inserted via a conductive elastic body so that a voltage is applied between the contact terminal and the first conductive electrode. Furthermore, an insulating cylinder is inserted inside the through hole provided in the first conductive electrode made of a conductive material, and the second electrode made of a dielectric material is inserted into the inside of the insulating cylinder to make the surface the first conductive electrode. Insert so that it becomes flat. Then, a voltage is applied between these first and second electrodes.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of a first embodiment of the present invention, which will be described below with reference to the drawings. Reference numeral 1 is an electrode made of aluminum, which is provided with one through hole. A hollow insulating cylinder 2 made of alumina is embedded in the through hole 18.
A pin electrode 7 made of aluminum is inserted inside the insulating cylinder 2. The tip surface 11 of the pin electrode 7 is the electrode 1
So as to project beyond the surface 12. Then, a dielectric film 5 made of alumina containing titanium oxide is formed on the electrode surface 12 and the tip surface 11 of the pin electrode 7 by a thermal spraying method. Of course, the dielectric film formed in such a process does not have a uniform thickness and becomes higher at the pin electrode portion, so that polishing is performed so that the entire surface is finally flat. As a result, the thickness of the dielectric film is thick above the electrode 1 and thin above the pin electrode 7. Next, the electrode 1 is connected to the DC power source 8 whose one end is grounded 9, and the pin electrode 7
Is connected in series with the DC power source 8 via the switch 10. Then, by turning the switch 10 on and off, a potential difference can be applied between the electrode 1 and the pin electrode 7, and the wafer 6 on the dielectric film can be electrostatically adsorbed. If a voltage is applied between the electrode 1 and the pin electrode 7 at this time, the area of the end face of the pin electrode facing the dielectric film is smaller than the area of the electrode 1, but if the thickness of the upper part of the pin electrode is made sufficiently small, The resistance of the film above 7 can be reduced. Therefore, most of the applied voltage is applied to the electrode 1, so that it can be uniformly adsorbed.

In the electrostatic chucking device constructed as described above, the wafer can be arbitrarily attracted and desorbed by turning on and off an external switch, and an electrostatic chucking device which is easy to handle can be provided. . Further, since there is no mechanism for mechanically contacting the wafer processing surface or the wafer outer peripheral portion, foreign matter is less likely to adhere to the processing surface, and a device with higher yield can be provided.

Although aluminum is used as the material of the electrode 1 in this embodiment, any other material may be used as long as it is a conductive material. Further, as the material of the dielectric film 5, alumina containing titanium oxide is used in this embodiment, but other materials may be used as long as they have dielectric properties. For example, ceramics such as silicon carbide, calcium oxide, and aluminum nitride may be used, or a polymer material may be used. Further, although thermal spraying is applied in the present embodiment as a film forming method when ceramic is used as a dielectric film, other methods such as vapor deposition and CVD can also be used. Further, in the present embodiment, the method of electrically insulating the pin electrode 7 from the electrode 1 uses the hollow insulating cylinder 2 made of alumina, but it is not always necessary to have such a structure, and for example, the penetration It is also possible to insulate by a method such as forming an insulative film on the inner wall of the hole.

FIG. 2 is a sectional view of the second embodiment of the present invention. A dielectric film 19 having a flat surface is formed on the surface of the electrode 1 provided with the through holes 18 by the film forming method similar to that of the first embodiment. A hollow insulating cylinder 14 made of alumina is inserted into the through hole 18. Here, the insulating cylinder 14 is attached to the through hole 18 using an adhesive, but the present invention is not limited to this, and may be performed by fitting or screwing, for example. Alternatively, an insulating cylinder may be attached before attaching the dielectric film 19 to the electrode 1, and the dielectric film 19 may be attached and fixed there. A connector 15 for connecting to an electric circuit is attached to the end of the insulating cylinder 14 on the side opposite to the surface supporting the wafer 6. A stainless steel coil spring 16 is placed inside the insulating cylinder 14. A contact terminal 17 made of aluminum is inserted in the end opposite to the connector 15 while being supported by the coil spring 16 so that the surface thereof is higher than the surface 20 of the dielectric film. Here, the spring constant of the coil spring is such that, when the weight of the contact terminal and the weight of the wafer act, the surface of the contact terminal that contacts the wafer sinks more than the amount higher than the dielectric film surface 20. . When a voltage is applied between the connector 15 and the electrode 1 by the DC power supply 8, a potential difference is generated between the dielectric film 19 and the contact terminal 17, and the wafer 6 can be electrostatically adsorbed. 9 in the figure means grounding as before, and 1
Reference numeral 0 is a switch for turning on / off the DC voltage.

In the electrostatic chucking device thus constructed, the wafer can be arbitrarily sucked and desorbed by turning on / off the external switch, and the electrostatic chucking device which is easy to handle can be provided. . Further, since nothing is in contact with the processing surface or side surface of the wafer, the influence of foreign matter can be minimized.

In this embodiment, the coil spring 16 used to support the contact terminal 17 has conductivity, and the electrode 1
And also serves as a potential difference between the contact terminals. Therefore, the coil spring is not necessarily required as long as it has these functions, and for example, a conductive spring may be used. Although aluminum is used as the material of the contact terminal in order to have conductivity, it is also possible to use a semiconductive material such as silicon carbide having a low resistivity. In this case, since the electric charge can be stored also in the contact terminal, even if the back surface of the wafer is provided with the insulating film, it is possible to suppress the decrease in the attraction force.

FIG. 3 shows a third embodiment of the present invention.
In place of the contact terminal 17 shown in FIG. 1, an electrode 21 made of a conductive material and having a dielectric film 22 attached to the surface thereof is used as the insulating cylinder 14
Has been inserted. Here, the material of the dielectric film 22 is the same as that of the dielectric film 19 on the electrode 1, and the thickness of the dielectric film 22 is smaller than the thickness of the dielectric film 19 attached to the surface of the electrode 1.
This is because when the voltage is applied between the connector 15 and the electrode 1, the dielectric film 22 is applied with a large voltage.
This is to reduce the resistance of. The material of the dielectric film 22 may be different from the material of the dielectric film 19 attached to the electrode 1, but in this case, the resistance value of the dielectric film 22 is smaller than the resistance value of the dielectric film 19 as described above. Is desirable.

In the electrostatic chucking device constructed as described above, in addition to the same effect as the third embodiment, the resistance value of the dielectric film 22 attached to the electrode 21 is higher than that of the dielectric film of the electrode 1. Since it is small, most of the applied voltage is applied to the dielectric film on the electrode 1 and a large attractive force can be obtained. Further, since the electric charge can be stored also in the dielectric film on the electrode 21, it is possible to suppress the decrease of the attraction force even if the wafer has an insulating film.

FIG. 4 is a view showing a fourth embodiment of the present invention. Instead of the contact terminal 17 of the second embodiment of the present invention, a contact terminal 4 with a curvature is used on the surface contacting the back surface of the wafer. It is configured to have continuity. The material of the contact terminal 4 with curvature may be any of a conductive material, a semiconductive material, and a dielectric material, and may be appropriately determined depending on the object of adsorption. Further, a thin dielectric film may be formed on the surface of the conductive terminal having a curvature.

In the electrostatic chucking device constructed as described above, in addition to the same effect as the second embodiment, the repetitiveness of the chucking force is maintained because the contact state, that is, the conducting state is always constant even if the wafer chucking is repeated. It is possible to obtain a better electrostatic adsorption device.

FIG. 5 is a diagram showing a fifth embodiment of the present invention. Instead of the contact terminal 17 of the second embodiment of the present invention,
On the support member 23 made of a conductive material (aluminum in this embodiment), the curvature of the tip 3 is reduced to the extent (5 μm or less) of penetrating the insulating film on the back surface of the wafer by the pressing pressure of the coil spring 13. It is configured to be attached. The material of the conductive needle may be, for example, conductive diamond, but is not limited to this.

In the electrostatic chucking device thus constructed, the third
In addition to the effect similar to that of the above embodiment, since it is possible to break through the insulating film attached to the back surface of the wafer to establish conduction, a stable adsorption force can be obtained regardless of the film type.

FIG. 6 is a diagram showing a sixth embodiment of the present invention. In the second to fifth embodiments of the present invention described above, the electrode rod 25 serving as an electrode is inserted into the insulating cylinder 14. Then, the end face 24 on the side in contact with the wafer is made flat with the surface of the dielectric film. The material of the electrode rod may be any of a conductive material (such as aluminum), a semi-conductive material (such as low resistance ceramics such as silicon carbide), or a dielectric material (such as alumina), and may be appropriately determined.

Even in the electrostatic chucking device constructed as described above, the wafer can be arbitrarily attracted and desorbed by turning on / off the external switch as in the third embodiment of the present invention, and the handling is easy. It is possible to provide a simple electrostatic adsorption device. In addition, since there is no part that makes mechanical contact with the processing surface of the wafer or the outer peripheral portion of the wafer, there is an effect that foreign matter is hard to adhere to the processing surface of the wafer. In particular, when a semi-conductive material or a dielectric material is used as the material of the contact terminal, the contact terminal can also store an electric charge, and even at this portion, it can be adsorbed, so that even if the back surface of the wafer has an insulating film. It is possible to suppress a decrease in adsorption force.

FIG. 7 is a diagram showing a seventh embodiment of the present invention. In this embodiment, instead of the electrode rod 25 shown in the sixth embodiment described above, a dielectric 26 is provided on the end face of the electrode rod 31 which comes into contact with the wafer so that the surface thereof is flat with the surface of the dielectric film. It is configured with the material of. here,
The thickness of the dielectric film is made smaller than the thickness of the dielectric film so that the voltage is effectively applied to the dielectric film when the voltage is applied to the electrode rod 31 and the electrode 27, and the resistance value of the dielectric film of the electrode rod is set to the dielectric value. Although it is made smaller than the resistance value of the film, this thickness may be appropriately determined in actual use.

With the electrostatic chucking device constructed as described above, the same effect as that of the sixth embodiment can be expected.

Up to now, the case where the number of the electrodes 21 which provide an electrical contact to the electrode 27 is one has been described, but the number is not necessarily limited to this, and a plurality of electrodes may be provided.
Further, although the position of the electrode 21 with respect to the electrode 1 is not mentioned, this may be appropriately determined depending on, for example, the relationship with the passage of the cooling medium provided in the electrode 27.

FIG. 8 is a sectional view of an eighth embodiment of the present invention, and FIG. 9 is a view as seen from the wafer support surface direction. 27
Is an electrode 1 made of a conductive material (here, made of aluminum). Unlike the conventional electrode 27, no dielectric film is attached to the surface, and the surface is finished flat to support the wafer. There is. The electrode 27 has a through hole 28.
Are provided on a concentric circle at equal intervals. A hollow insulating cylinder 29 made of an insulating material is inserted into the through hole 28, and an electrode rod 30 made of a dielectric material is placed inside the hollow insulating cylinder 29.
Has been paid. The electrodes 27, the insulating cylinder 29, and the electrode stick 30 are made as flat as possible on the wafer suction surface side. The switch 10 is attached to the electrode 27 and the electrode rod 30.
The DC power supply 8 is connected via. Therefore, the electrode 2
If a potential difference is applied between the electrode 9 and the electrode rod 30, electric charges are stored in the electrode rod 30 and the wafer can be attracted.

In the electrostatic adsorption device having the above-described structure, the adsorption / desorption of the wafer can be controlled by switching the switch regardless of the presence / absence of plasma, as in the above-described embodiment, so that the electrostatic adsorption device has good operability. In addition, since the dielectric film does not exist on most of the contact surface of the wafer, the device has a very good thermal conductivity when the electrode needs to be cooled by a cooling device (not shown). Further, since most of the contact surface of the wafer is conductive, the charge stored on the wafer can be eliminated quickly, and a highly responsive electrostatic adsorption device can be provided.

In this embodiment, the dielectric material is provided in the insulating cylinder, but any other structure may be used as long as it has a structure in which electric charges can be stored on the contact surface with the wafer. For example, a dielectric film may be attached to the end surface of an electrode made of a conductive material. Also,
In the present embodiment, the number of dielectrics is four, but it may be determined according to the attractive force, and the number may be larger or smaller. Further, although the dielectrics are arranged on the concentric circles, they are not particularly limited and may be appropriately determined depending on, for example, the arrangement of cooling grooves (not shown).

Although the embodiments in which a DC power supply is connected between the electrodes 1 and 21 have been described above, an AC power supply may be connected. Further, it may be a power source in which a DC component is placed on an AC power source component. Further, in the present embodiment, an example in which one of the DC power supplies is grounded has been described, but it does not necessarily have to be grounded and may be in a floating state and may be appropriately determined according to actual use.

Further, although not explicitly stated in the above-described embodiments, if the electrodes 1 and 21 are provided with a groove for flowing a coolant for controlling the temperature of the wafer, electrostatic adsorption excellent in temperature controllability is achieved. A device and a device using the same can be provided. Further, a cooling gas flow groove for increasing the cooling efficiency of the wafer is provided on the surface that actually adsorbs the wafer, and if a cooling gas such as helium is flown into this groove, the wafer can be cooled more efficiently. it can.

[0033]

According to the present invention, the wafer can be arbitrarily attracted and desorbed by turning on and off a switch provided outside, so that an electrostatic attraction device which is easy to handle can be provided. Further, according to the electrostatic attraction device of the present invention, the wafer can be attracted and desorbed with good reproducibility even when the insulating film is present on the back surface of the wafer. Further, since there is no mechanical contact with the processing surface of the wafer or the outer peripheral portion of the wafer, foreign matter is unlikely to adhere to the processing surface. In addition, if most of the electrodes supporting the wafer are made of a conductive material having good thermal conductivity, an electrostatic adsorption device having good temperature controllability and responsiveness can be provided.

[Brief description of the drawings]

FIG. 1 is a sectional view of a first embodiment.

FIG. 2 is a sectional view of a second embodiment.

FIG. 3 is a sectional view of a third embodiment.

FIG. 4 is a sectional view of a fourth embodiment.

FIG. 5 is a sectional view of a fifth embodiment.

FIG. 6 is a sectional view of a sixth embodiment.

FIG. 7 is a sectional view of a seventh embodiment.

FIG. 8 is a sectional view of an eighth embodiment.

FIG. 9 is a plan view of a ninth embodiment viewed from the wafer suction surface direction.

[Explanation of symbols]

1 ... Electrode, 2 ... Insulation cylinder, 5 ... Dielectric film, 6 ... Wafer, 7 ...
Pin electrode, 8 ... DC power supply, 9 ... Ground, 10 ... Switch,
11 ... Tip surface of pin electrode, 12 ... Surface of electrode.

Claims (4)

[Claims] 1. A first conductive electrode having at least one through hole, wherein a second conductive electrode is electrically insulated from the first conductive electrode in the through hole. Is inserted so that the end portion is projected while forming a flat dielectric film on the surface of the first conductive electrode and the second conductive electrode, the first conductive electrode and the second conductive electrode. An electrostatic adsorption device characterized by applying a potential difference between conductive electrodes. 2. A first conductive electrode having a flat dielectric film on a surface thereof is provided with a through hole penetrating the dielectric film and the first conductive electrode, and the through hole has a hollow insulating material. A second electrode supported by a conductive elastic member and movable along the through hole is inserted into the through hole, and the first conductive electrode and the second conductive electrode are inserted into the through hole. An electrostatic attraction device characterized in that a potential difference is applied between two conductive electrodes. 3. A first conductive electrode having a flat dielectric film on a surface thereof is provided with a through hole penetrating the dielectric film and the first conductive electrode, and the through hole has a hollow insulating material. Inserting an insulating cylinder made of, and inserting the second electrode inside the through hole so that its end face is flat with the surface of the dielectric film,
An electrostatic adsorption device, characterized in that a potential difference is applied to the first electrode and the second electrode. 4. A through hole is prepared in a first conductive electrode having a flat surface, and a hollow insulating cylinder is inserted into the through hole,
A second electrode made of a dielectric material is inserted into the insulating cylinder so that its end face is flat with the surface of the first electrode, and a voltage is applied to the first electrode and the second electrode. An electrostatic chucking device.