JPH04372152A - electrostatic chuck device - Google Patents

Abstract

PURPOSE:To realize a strong attraction force by a low voltage and to shorten attaching/detaching time of a material to be attracted. CONSTITUTION:In an electrostatic chuck device for attracting to hold a material 12 to be attracted such as a semiconductor wafer, an inorganic insulating material is so deposited on a polished substrate 1 to a thickness that an uneven part of the surface of the becomes substantially flat thereby to form a first inorganic insulating material layer 6, an electrode material layer 2 is formed on the layer 6 by depositing, and a second inorganic insulating material layer 7 is formed on the layer 2 by depositing.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic chuck device, and particularly to an electrostatic chuck device that electrostatically holds a flat plate member such as a semiconductor wafer.
The present invention relates to a technology that generates a large holding force with a relatively low voltage and shortens the time required to attach and detach a wafer.

0002

[Prior Art] Conventionally, an electrostatic chuck device used in semiconductor exposure equipment or inspection equipment has a metal plate for an electrode placed on a polished substrate, and then polished by machining. It is known that a thin insulating plate covered with a thin plate is used.

Alternatively, conventionally, an electrode is formed by depositing a conductive material directly on a polished ceramic substrate by vapor deposition or sputtering, and an inorganic insulating material such as alumina is deposited on top of this electrode. An electrostatic chuck device has been proposed.

0004

[Problems to be Solved by the Invention] Among such conventional electrostatic chuck devices, the former device in which an insulating thin plate formed by machining is provided on the electrode has a structure made of an insulating thin plate. It was difficult to process the insulating layer to be very thin. Therefore, in order to obtain the electrostatic force necessary to attract the wafer, it was necessary to apply a high attraction voltage of several hundred volts. Furthermore, since the insulating layer is relatively thick, it takes time to accumulate charges in the insulating layer or release charges from the insulating layer, resulting in the inconvenience that it takes a long time, for example, 10-odd seconds, to attach and detach the wafer. was there. In order to shorten the time for attaching and detaching the wafer, the specific resistance of the insulating material constituting the insulating layer is set to 1010 to 1012.
It is also being considered to make it relatively small, on the order of Ω·cm. However, this method has the disadvantage that a minute current flows through the insulating layer into the wafer, destroying the transistors formed on the wafer surface.

In addition, in the latter electrostatic chuck device in which an electrode material is directly deposited on a polished ceramic substrate and an inorganic insulating material is deposited thereon, the polished ceramic substrate has a depth of about 0.5 μm. Since many minute depressions are formed, the electric field strength becomes strong in the vicinity of these depressions, making it easy to cause electric discharge. For this reason, with this type of device, it is not possible to apply a very large adsorption voltage,
It was not possible to obtain large electrostatic forces.

SUMMARY OF THE INVENTION In view of the above-mentioned problems with the conventional apparatus, an object of the present invention is to obtain a large electrostatic force even at a relatively low voltage and to shorten the time required for attaching and detaching an object to be attracted such as a wafer. The object of the present invention is to provide an electrostatic chuck device that is capable of

[0007]

[Means for Solving the Problem] In order to achieve the above object, according to the present invention, an inorganic insulating material is deposited on a polished substrate to a thickness such that unevenness on the surface of the substrate is almost flattened. forming a first inorganic insulating material layer, depositing an electrode material layer on the first inorganic insulating material layer, and depositing a second inorganic insulating material layer on the electrode material layer; An electrostatic chuck device is provided.

[0008] The substrate is preferably a ceramic substrate made of high-purity alumina or alumina containing zirconia (ZrO2).

Further, the first inorganic insulating material layer is made of Ta2.
The second inorganic insulating material layer is formed of O5 and is advantageously formed of Ta2O5 sputtered in a gas mixture of argon and oxygen in which the partial pressure of oxygen is greater than 0.05 Pa.

Furthermore, it is also possible to form the electrode material and the inorganic insulating material layer by sequential deposition directly on a mirror-polished tempered glass or zirconia ceramic substrate.

[0011]

[Function] In the above configuration, when a ceramic substrate made of, for example, high-purity alumina or alumina containing zirconia is polished, a recess of, for example, 0.5 μm or less remaining on the surface of the substrate is removed by applying an inorganic insulating material to the recess. Planarization is achieved by depositing the first inorganic insulating material layer to a thickness of about 10 times or more, that is, 5 μm or more. An electrode material such as metal or semiconductor is deposited on this flattened first inorganic insulating material layer, and the second inorganic insulating material layer is further formed thereon. Therefore, even when a voltage is applied to the electrode material layer, concentration of the electric field due to the depressions in the insulating layer does not occur, and a sufficiently large adsorption voltage can be stably applied as required. Therefore, the wafer can also be held with a large electrostatic force. Further, since the second inorganic insulating material layer is formed by deposition, its thickness can be made sufficiently thin. Therefore, a large adsorption force can be obtained even at a relatively low voltage, and the time required for attaching and detaching the adsorbed object is shortened.

[0012] Furthermore, by using high-purity alumina or alumina mixed with zirconia (ZrO2) as the substrate, the depression on the surface of the polished substrate can be reduced to 0.5 μm.
It has been experimentally shown that it can be made smaller than m.

Furthermore, the dielectric strength of the lower layer, ie, the first inorganic insulating material layer, does not need to be very large. Therefore, by forming the first inorganic insulating material layer from Ta2O5, the deposition rate increases and the film formation is completed in a short time. Further, the upper layer, that is, the second inorganic insulating material layer, is required to have a high dielectric constant and high dielectric strength. Therefore, it has been found that an insulating film having a large dielectric strength can be formed by sputtering in a mixed gas of argon (Ar) and oxygen (O2) with an oxygen partial pressure of 0.05 Pa or higher.

Furthermore, when tempered glass or zirconia is used as the substrate, it is possible to polish the surface to a very smooth surface. Therefore, in this case, unlike in the case of ceramics such as high-purity alumina, there are no minute depressions, so it is possible to form an electrode material layer directly on the substrate by deposition, and then deposit an insulator on top of it. .

[0015]

Embodiments Hereinafter, embodiments of the present invention will be explained with reference to the drawings. FIG. 1 is an enlarged cross-sectional view of the vicinity of the periphery of an electrostatic chuck device according to an embodiment of the present invention, and FIG. 2 is a schematic plan view seen from above.

As shown in these figures, the electrostatic chuck device according to this embodiment has a ceramic substrate 1 made of, for example, high-purity alumina. Indentations 8 of, for example, 0.5 μm or less remain partially on the polished surface of the ceramic substrate 1 . On such a substrate 1, there is provided an insulating layer 6 formed by depositing, for example, Ta2O5 to a thickness of, for example, 10 .mu.m by sputtering. The sputtering conditions for Ta2O5 are, for example, an oxygen partial pressure of 0.
04 Pa and Ar partial pressure of 1.0 Pa, and the film is formed in about 8 hours. Further, in order to gradually reduce the thickness of the insulating layer 6 in the peripheral region, it is convenient to perform film formation with the mask slightly lifted from the substrate.

An electrode material layer 2 is formed on the insulating layer 6. This electrode material layer 2 was formed by sputtering titanium in Ar.

Furthermore, an uppermost insulating layer 7 is formed to cover the electrode material layer 2. This insulating layer 7 is made of, for example, Ta2O5 with an oxygen partial pressure of 0.06 Pa and an Ar partial pressure of 1.0 P.
8 μm by sputtering for 16 hours in the atmosphere of a.
It is formed to a thickness of . By using such a film forming method, an insulating film having high dielectric strength can be formed.

FIG. 2 is a top plan view of the electrostatic chuck device having the layered structure as described above. As shown in the figure, an electrode material layer formed on a substrate 1 via an insulating layer 6 (not shown) has, for example, four sector-shaped electrode parts 2--
It is divided into 1, 2-2, 2-3, and 2-4, and each electrode portion is connected to an attraction voltage source (not shown) through a lead-out lead electrode 3 formed through a central opening 4. In this case, for example, a positive voltage is applied to the electrode parts 2-1 and 2-3, and a negative voltage having the same absolute value as this positive voltage is applied to the other electrode parts 2-2 and 2-4. be done. Note that FIG. 1 is A- in FIG. 2.
This is a partial cross-sectional view taken along line A.

[0020] In the electrostatic chuck device having the above-mentioned configuration, when the adsorption voltage is applied to each electrode portion constituted by the electrode material layer 2 as described above, the electrode material layer 2 and the insulating layer 7 A potential difference is generated between the magnet and the object 12 placed thereon, such as a semiconductor wafer, so that the object 12 is electrostatically attracted. In this case, since the surface of the insulating layer 6 on which the electrode material layer 2 is formed is smooth without any depressions, the adsorption voltage can be increased if necessary compared to the case where the electrode is deposited directly on the ceramic substrate. can be applied stably. Further, since the thickness of the insulating layer 7 can be adjusted to a sufficiently thin desired value, a large adsorption force can be obtained with a low voltage, and the time required for attaching and detaching the object 12 to be adsorbed does not become long. In this example, at a relatively low voltage of about 100V, 3
A large electrostatic force of about 0 gr/cm2 was obtained, and the time required for attaching and detaching the wafers was 2 to 3 seconds each.

Furthermore, since the edge portion of the electrode material layer 2 is sharp, it is easy to discharge, but in the present invention, since the lower insulating layer 6 is tapered and thinned, the edge portion 11 of the electrode material layer 2 and the semiconductor wafer are The distance to the adsorbed object 12 becomes larger, and there is an air layer in between. Since the air layer has a dielectric constant ε* of 1, and Ta2O5 has an ε* of approximately 25, most of the electric field is applied to the air layer and no high electric field is applied to the edge portion. Therefore, discharge at the edge portion is effectively prevented.

Next, in the electrostatic chuck device according to the second embodiment of the present invention, the substrate 1 is made of tempered glass, Z
Consists of rO2 or Sialon. In this case, unlike in the case of ceramics, minute depressions are not formed on the surface, so the insulating layer 6 is omitted and the electrode material layer 2 is formed directly on the substrate 1. In this manner, by selecting a specific material for the substrate 1, an electrostatic chuck device having excellent performance can be realized. In this example, in order to prevent discharge at the electrode end and apply a higher voltage, a mask used for depositing the electrode material layer is used, and this mask is applied to the surface of the substrate 1. It is also possible to deposit a thin layer of Ta2O5 at a distance from the electrode material layer after depositing a thin layer of Ta2O5. Alternatively, the peripheral portion of the substrate 1 itself may be polished so as to gradually become thinner slightly outward.

[0023]

As described above, according to the present invention, it is possible to realize an electrostatic chuck device having a strong adsorption force at a low voltage even when a ceramic substrate having a high Young's modulus and a large bending strength is used. Further, since the insulating layer is thin, sufficient electrostatic adsorption force can be obtained even at a voltage lower than that of the conventional method, and an object to be adsorbed such as a wafer can be attached and detached extremely quickly.

In addition, there is no need to reduce the specific resistance of the insulating layer, and it can be set to, for example, 1013 Ω·cm or more, so that almost no direct current flows through the wafer, and there is no induced current that charges or discharges the capacitance. Also, since the applied voltage is lower, it is significantly reduced. Therefore, destruction of transistors and the like mounted on the wafer surface can be appropriately prevented.

Furthermore, if there is no risk of a large mechanical impact being applied to the substrate, a low-cost electrostatic chuck device can be manufactured by using tempered glass or the like as the substrate.

[Brief explanation of the drawing]

FIG. 1 is a partially enlarged sectional view showing the layer structure of an electrostatic chuck device according to an embodiment of the present invention.

FIG. 2 is a schematic plan view of the electrostatic chuck device of FIG. 1 seen from above.

[Explanation of symbols]

1 Substrate 2 Electrode material layer 2-1, 2-2, 2-3, 2-4 Electrode part 3 Leading electrode 4 Hole 6 First insulating material layer 7 Second insulating material layer 8 Recess 9 Taper of insulating layer 6 Part 10 Tapered part 11 of electrode material layer 2 Edge part 12 Adsorbed object 13 Air or vacuum layer

Claims (5)

[Claims] 1. A first inorganic insulating material layer is formed by depositing an inorganic insulating material on a polished substrate to a thickness such that unevenness on the surface of the substrate is substantially flattened; An electrostatic chuck device characterized in that an electrode material layer is formed on the inorganic insulating material layer by deposition, and a second inorganic insulating material layer is formed on the electrode material layer by deposition. [Claim 2] The substrate is made of high purity alumina or Z
The electrostatic chuck device according to claim 1, wherein the electrostatic chuck device is a ceramic substrate made of alumina containing rO2. 3. The first inorganic insulating material layer is Ta2O.
5, and the second inorganic insulating material layer is formed by sputtering Ta2O5 in a mixed gas of argon and oxygen in which the partial pressure of oxygen is greater than 0.05 Pa. or the electrostatic chuck device according to 2. 4. An electrode material layer is formed by deposition on a mirror-polished tempered glass, sialon, or ZrO2 substrate, and an inorganic insulating material layer is further formed by deposition on the electrode material layer. Electrostatic chuck device. 5. The method according to claim 1, wherein the thickness of the first inorganic insulating material layer or the substrate gradually decreases toward the outside in a peripheral area of the electrode material layer. The electrostatic chuck device according to any one of the items.