JPH04367246A - Electrostatic attraction apparatus - Google Patents

Abstract

PURPOSE:To obtain the holding apparatus of a semiconductor wafer, wherein the semiconductor wafer can be flattened and held so as to be kept clean inside a vacuum by means of a large holding force and an electric current flowing in the held wafer and the apparatus is mail at this time by a method wherein a dielectric layer on an electrode is constituted of a plurality of protrusions formed independently on the surface on the side of the holding face of the electrode. CONSTITUTION:A dielectric layer 2 is formed at least on the surface of an electrode 3; the dielectric layer 2 is sandwiched between an object 1 to be held and the electrode 3; a voltage is applied. Thereby, the object 1 is attracted to and held by a holding face 2A on the dielectric layer 2. In such an electrostatic attraction apparatus, the dielectric layer 2 is composed of a plurality of protrusions 2B which have been formed independently on the surface on the side of the holding face 2A of the electrode 3. For example, the protrusions 2B are formed of alpha-type SiC or the like. Thereby, the object such as a wafer or the like can be held by a large holding force inside a vacuum. It is reduced that foreign bodies adhere to the object due to contact with the attraction apparatus, and an electric current flowing in the wafer and the apparatus can be kept small when the wafer is held.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a holding device for a conductor or semiconductor sample, and more particularly to a holding device for holding a semiconductor wafer or the like in a vacuum or reduced pressure atmosphere using electrostatic adsorption force.

0002

2. Description of the Related Art Conventionally, as a device for holding a semiconductor wafer by electrostatic adsorption force, for example, Japanese Patent Laid-Open No. 63-9564
As shown in Publication No. 4 and the technical data of Toto Kiki Co., Ltd., an insulating film is provided on at least the surface of the electrode, and this insulating film is made of an insulating material with high volume resistivity, a conductor, a semiconductor, or a low-resistance material. Some devices are formed of an insulating film containing a mixture of the above, and further have a step formed by a concave part and a convex part on the holding surface on the insulating film.

0003

[Problems to be Solved by the Invention] In recent years, with the miniaturization of circuit patterns of semiconductor devices, a holding device and a heating device are required to prevent foreign matter from adhering to the wafer and flatten and fix it in a vacuum or reduced pressure atmosphere during the manufacturing process. - A holding device that tightly fixes the wafer for cooling and a handling device that can hold the back side of the wafer are required.

[0004] In response to this requirement, in the conventional technology, the holding surface is provided with concavities and convexities, so that it is possible to reduce the adhesion of foreign matter to the held wafer, and even if foreign matter is attached to the holding surface or the wafer surface, flattening is prevented. It has the advantage of being difficult.

However, on the other hand, since the holding force per unit area is originally small, there is a problem in that the holding force is further reduced by providing unevenness on the holding surface.

In addition, in order to increase the holding force, an insulating film whose resistivity is reduced by mixing a low-resistance material is used.
As shown in Section 5-2 of ``Ceramic Electrostatic Chuck for OTO Transfer'', there was a problem in that a large current flows through the wafer and equipment.If a large current flows through the wafer, the element circuits formed on the wafer surface will be destroyed. .Furthermore, in order to pass a large current through the device, a large-sized high voltage generator is required.

An object of the present invention is to be able to hold a semiconductor wafer with a large holding force in a vacuum or reduced pressure atmosphere, to prevent foreign matter from adhering to the wafer during holding, and to prevent foreign matter from adhering to the wafer holding surface or the wafer. It is an object of the present invention to provide a semiconductor wafer holding device which can flatten and hold a wafer even when the wafer is flattened and which requires a small current to flow through the held wafer and the device.

[0008]

[Means for Solving the Problems] An object of the present invention is to provide a dielectric layer on at least the surface of an electrode, and apply a voltage with the dielectric layer sandwiched between the object to be held and the electrode. In an electrostatic adsorption device that attracts and holds an object on a holding surface on a dielectric layer, the dielectric layer is formed of a plurality of protrusions made of, for example, SiC and independently provided on the surface of the electrode on the holding surface side. This is achieved by

[0009]

[Operation] In the electrostatic chuck device of the present invention, the dielectric layer is formed of a dielectric material such as α-type SiC. This α-type Si
Since the dielectric constant of C reaches several hundred to several thousand, it is possible to generate a large adsorption force compared to a conventional device using an insulating film with a dielectric constant of about several tens.

Further, in the electrostatic adsorption device of the present invention, the dielectric layer is formed of a plurality of protrusions. Since the wafer and the device come into contact with each other through a small area of the tips of the protrusions, the transfer (adhesion) of foreign matter to the wafer due to contact with the suction device is reduced. Further, even if foreign matter exists between the wafer and the holding device, most of it will enter the recesses between the plurality of protrusions, so that the wafer will be held flat and fixed.

Further, in the electrostatic adsorption device of the present invention, the dielectric layer is formed of projections provided substantially independently on the surface of the electrode. At this time, the cross-sectional area of the flow path of the current flowing through the wafer or device is approximately equal to the holding area of the protrusion tip, and the current value is approximately proportional to the holding area of the protrusion tip, so the present invention has a small total area of the protrusion tip holding surface. The current value of the device becomes a small value. In the case of conventional equipment in which shallow irregularities are formed on the surface of the insulating film, even if the contact area becomes smaller, the cross-sectional area of the flow path through which the current flows does not decrease, so the current value flowing through the wafer or equipment is lower than that when there are no irregularities. remains roughly equal.

0012

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIGS. 1 to 3 show an embodiment of the apparatus of the present invention, and in these figures, reference numeral 1 indicates a conductor or semiconductor object, such as a semiconductor wafer, to be held by suction. Reference numeral 3 denotes an electrode, and a dielectric portion 2 consisting of a projection 2B is provided on the electrode. The tip of the protrusion 2B forming the dielectric portion 2 is provided with a holding surface 2A that attracts and holds the object 1.

Further, a conductive portion 4 is provided which is electrically connected to the wafer, and this conductive portion is grounded to the ground potential of the surrounding environment. The electrode 3 and the conductive portion 4 are connected to both poles of the voltage generator 6 via conductive wires 8 and 9 and a changeover switch 7. When holding the object 1 in the hand main body 2, the changeover switch 7 is connected to a contact 7B on the voltage generator side so that a voltage is applied between the electrode 3 and the conductive part 4, and holds the object 1 in the hand body 2. When released from the main body, the electrode 3 is configured to be connected to the ground side contact 7C so as to have the same potential as the ground potential of the surrounding environment.

Next, the operation of one embodiment of the apparatus of the present invention described above will be explained.

First, the operation when holding the object 1 on the suction device will be explained.

In FIG. 1, when the changeover switch 7A is connected to the contact 7B side, a voltage is applied between the electrode 3 and the conductive portion 4. Since the object 1 is made of a conductor or a semiconductor material, the potential of the object 1 becomes equal to that of the conductive part 4, and a potential difference occurs between the object 1 and the electrode 3, and the following occurs between the object 1 and the electrode 3. The adsorption force F shown works.

[0018]

[Math 1]

The force expressed by equation (1) is exactly equal to the attractive force acting between the electrodes of a parallel plate capacitor. Due to this attraction force F, the object 1 is attracted and held on the electrode 3 via the dielectric part 2. At this time, when the dielectric constituting the dielectric portion 2 is formed of α-type SiC, for example, its relative permittivity (=ε1/ε0) reaches several hundreds to several thousands, so the relative permittivity is several tens of Compared to a conventional device that uses an insulating film of about .

FIG. 3 shows the results of an experimental comparison of the adsorption forces generated between the conventional device and the device of the present invention. d=0.15mm
Compared to a conventional device using an alumina film containing titanium oxide, the device of the present invention was able to generate an adsorption force 5.2 times that of the conventional device on a SiC film with d=5 mm.

Next, the operation of preventing foreign matter from adhering to the object 1 while the object 1 is held in the suction device, and the operation of holding the object 1 while keeping it flat will be explained.

In the semiconductor manufacturing process, adhesion of foreign matter of about 0.1 μm not only to the front side of the wafer but also to the back side becomes a problem. The adhesion of such microscopic foreign matter to the wafer due to contact with the handling device, holding device, etc. is inevitable, and the amount of such adhesion in the current device is roughly proportional to the contact area of the device to the wafer. In the device of the present invention,
Since the contact portion is limited to the small area of the holding surface 2A at the tip of the protrusion 2B, the amount of foreign matter adhering to the object 1 such as a wafer is small.

Furthermore, in the process of exposing circuit patterns onto wafers in the semiconductor manufacturing process, the wafer during light absorption work must be fixed and held at a flatness of 1 μm or less, and in the near future approximately 0.1 μm. There is. At this time, foreign matter caught between the contact surface between the wafer and the suction device causes deterioration of the flatness of the wafer. In the device of the present invention,
Since the holding surface is limited to the small-area holding surface 2A at the tip of the protrusion 2B, there is a small probability that a foreign object will get caught in the gap between the object 1 such as a wafer and the holding surface 2A and the flatness of the object 1 such as a wafer will deteriorate. .

Finally, the operation of reducing the current flowing through the wafer and the device while the object 1 is held in the suction device will be explained.

In conventional equipment in which shallow irregularities are provided on the holding surface of the insulating film, the film resistance of the insulating film is almost the same as when there are no irregularities, and the current value flowing through the wafer and the equipment is approximately the same as when there are no irregularities. . In the device of the present invention, the dielectric portion 2 is formed of projections 2B independently provided on the surface of the electrode 3. At this time, the current flowing through the wafer or device is roughly proportional to the total area of the holding surfaces 2A at the tip of the protrusion, so the current value is small in the case of the present invention where the total area of the holding surfaces 2A is small.

In this embodiment, the semiconductor wafer can be held with a large holding force in a vacuum or reduced pressure atmosphere,
Semiconductor wafers that can prevent foreign matter from adhering to the wafer during holding, and even if there is foreign matter adhering to the wafer holding surface or the wafer, the wafer can be held flat and fixed, and at this time, the current flowing through the held wafer and equipment is small. The object of the present invention is to provide a holding device.

In this embodiment, since the dielectric portion is formed of, for example, α-type SiC, an object such as a wafer can be held with a large holding force in a vacuum or a reduced pressure atmosphere. Furthermore, since the dielectric portion is formed of a plurality of protrusions, the adhesion of foreign matter to the object due to contact with the suction device is reduced, and even if there is foreign matter, the wafer is held and fixed flat. Further, since the dielectric portion is formed of projections provided substantially independently on the electrode surface, the current flowing through the wafer and the device when holding the wafer can be kept small.

FIG. 4 shows a second embodiment of the device according to the invention. In this embodiment, a protrusion 2 is formed on the surface of the electrode 3 on the holding 2 side.
This is the case where the surface not covered with B is covered with the insulating film 23.

According to this embodiment, for example, when holding the object 1, even if a conductive or semiconductive foreign object enters the recess 27 between the protrusions 2B, the electrode 3 will pass through this foreign object.
There is no electrical continuity between the object 1 and the object 1.

FIG. 5 shows a third embodiment of the device according to the invention. In this embodiment, the dielectric portion 2 is made of a dielectric material and includes a plurality of protrusions that are partially or entirely connected to each other on the side that contacts the electrode.

According to this embodiment, since the protrusions 2B are connected to each other, there is an advantage that the protrusions 2B are difficult to separate from the electrode 3. Furthermore, by covering the surface of the electrode 3 on the holding surface 2A side with the part connecting the protrusions 2B, even if conductive or semiconductive foreign matter enters the recess 27, the object 1 and the electrode 3 can be electrically connected. There is no.

FIGS. 6 to 9 show fourth to seventh embodiments of the present invention. This example shows an example of a method for manufacturing the device of the present invention. The dielectric part 2 is made of dielectric ceramic, and the electrode 3 is made of conductive or semiconducting ceramic.
and an electrode 3 made of conductive or semiconductive ceramics 3
are joined as shown in FIG. 7 before sintering and sintered as one piece. Grooving to form the shape shown in FIG. 8 or 9 is performed either before or after sintering. At this time, as shown in FIG. 8, by processing a groove slightly shallower than the thickness of the dielectric portion 2, protrusions 2B connected on the electrode surface side are formed. Conversely, by machining a groove deeper than the thickness of the dielectric portion 2, mutually independent protrusions 2B are formed.

According to this embodiment, since the dielectric part 2 and the electrode 3 are formed of ceramics which are integrally sintered, the bonding strength between the dielectric part 2 and the electrode 3 is high, and the dielectric part 2 has a deep bond. It becomes possible to process grooves. When bonding dielectric ceramics after sintering to metal electrodes or conductive ceramic electrodes, it is difficult to form grooves as shown in FIGS. 8 and 9.

[0034]

According to the present invention, since the dielectric portion is formed of, for example, α-type SiC, an object such as a wafer can be held with a large holding force in a vacuum or a reduced pressure atmosphere. Furthermore, since the dielectric portion is formed of a plurality of protrusions, the adhesion of foreign matter to the object due to contact with the suction device is reduced, and even if there is foreign matter, the wafer is held flat and fixed. Further, since the dielectric portion is formed of projections provided substantially independently on the electrode surface, the current flowing through the wafer and the device when holding the wafer can be kept small.

[Brief explanation of drawings]

FIG. 1 is a plan view showing an embodiment of the device of the present invention.

FIG. 2 is a vertical cross-sectional view of FIG. 1.

FIG. 3 is an explanatory diagram of the effects of the device of the present invention.

FIG. 4 is a longitudinal sectional view showing a second embodiment of the invention.

FIG. 5 is a vertical sectional view showing a third embodiment of the present invention.

FIG. 6 is a longitudinal sectional view showing an example of a method for manufacturing the device of the present invention as a fourth embodiment.

FIG. 7 is a longitudinal sectional view showing an example of the method for manufacturing the device of the present invention as a fifth embodiment.

FIG. 8 is a longitudinal cross-sectional view showing an example of the method for manufacturing the device of the present invention as a sixth embodiment.

FIG. 9 is a longitudinal sectional view showing an example of a method for manufacturing the device of the present invention as a seventh embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1... Object, 2... Dielectric part, 2A... Holding surface, 2B... Protrusion,
3... Electrode, 4... Conductive part, 6... Voltage generator, 7... Changeover switch, 8, 9... Conductive wire, 10... Ground, 11... Insulator, 27... Recessed part.

Claims (1)

[Claims] Claim 1: A dielectric layer is provided on at least the surface of the electrode,
In an electrostatic adsorption device that adsorbs and holds the object on a holding surface on the dielectric layer by applying electric power with the dielectric layer sandwiched between the object and the electrode, the dielectric layer comprises: An electrostatic adsorption device comprising a plurality of protrusions independently provided on the surface of the electrode on the holding surface side.