JPH03187240A - Electrostatic chuck - Google Patents

Abstract

PURPOSE:To enable quick dismounting operation of an object to be sucked and to improve workability and handling performance of chuck by making a ventilation groove having one open end in the surface of an insulator. CONSTITUTION:A chuck body 21 has C-shaped top view and an arm insertion groove, having one end opened partially to the circumferential face and the other end extending toward the center of the body, is made radially in the chuck body. A plurality of thin grooves 23a-23f having proper width and depth are made radially in the upper face while an organic insulating film 26A composed of polyimide is formed on the upper face of electrodes 24a-24p and between the electrodes, and an inorganic insulating film 26b of alumina or the like is formed thereon. Consequently, mounting/dismounting operation of an object to be sucked can quickly be carried out in the vacuum as well as in the atmosphere, especially dismounting operation in the atmosphere can quickly be carried out, and suction of the object can immediately be released upon application of zero voltage.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an electrostatic chuck that is used in semiconductor manufacturing processes, etc., and which electrostatically holds a substrate such as a silicon wafer with good flatness. The present invention relates to an electrostatic chuck suitable for use in both vacuum regions.

[Prior art] Conventionally, silicon wafers (hereinafter referred to as wafers) were manufactured in the atmosphere.
A vacuum chuck or a mechanical chuck device is used as a device for holding and fixing a substrate with good flatness.

On the other hand, X! When transferring an integrated circuit pattern onto a wafer using an exposure device or observing the surface of a wafer using an electron microscope, the wafer cannot be chucked (held by suction) due to the vacuum environment. Therefore, an electrostatic chuck that utilizes electrostatic force as seen in Japanese Patent Application Laid-Open No. 59-74624 has been used.This electrostatic chuck uses aluminum, titanium, chromium, etc. on a substrate made of an insulating material. Two electrodes are formed using an alloy as the main component, and a thin insulating layer with a thickness of several μm to 30 μm is formed on the surface of these electrodes by oxidation treatment, and furthermore, a thin film insulating layer with a thickness of several μm to 30 μm is formed on the surface of the electrode to prevent a drop in breakdown voltage due to pinholes. Therefore, it is coated with an insulating resin.

In such a configuration, after placing a wafer as an object to be attracted on the electrostatic chuck, if high voltages (±50 volts to ±200 volts) with opposite signs are applied between the two @poles, each of the wafers Charges of opposite polarity to those of the electrodes are induced on the surfaces facing the electrodes, and this causes the electrodes to attract and fix the wafer by electrostatic force, correcting warpage on the wafer surface and achieving high flatness. I have to.

Here, the electrostatic adsorption force (F) by the electrostatic chuck is given by the following equation.

However, ε. is the dielectric constant in vacuum, cl is the dielectric constant of the insulator, S is the surface area of the electrode, ■ is the voltage applied to the electrode, and d is the thickness of the insulator.

Therefore, ε from equation 1. , if S is constant, ``ε1l
V2 Fα d '', and the electrostatic adsorption force F can be increased by changing the applied voltage, in other words, the amount of electric charge induced.Also, as another conventional example of an electrostatic chuck, a single electrode is placed on a ceramic substrate. There is one in which a separately polished ceramic thin plate is fused with glass or the like to ground the object to be attracted.

[Problems to be Solved by the Invention] By the way, as mentioned above, in the wafer manufacturing process, an electrostatic chuck is responsible for transporting and holding the wafer in vacuum.
Since a vacuum chuck is responsible for transporting and holding the wafer in the atmosphere, two types of chucks are required. The handing operation was troublesome when receiving goods between stores.

In particular, in the case of a vacuum chuck, it is necessary to create a gas flow to attach and detach the wafer, and it is also necessary to open and close mechanical valves, making it difficult to attach and detach quickly. However, since an air supply pump is required, the device itself is large-scale and expensive.

Another problem with mechanical chucks is that it takes time to attach and detach the wafer, and that it generates a lot of dust because it requires contact and pressure between multiple surfaces of the wafer, such as the bottom surface, the side surface, or the bottom surface and the periphery of the surface. there were.

On the other hand, in the conventional electrostatic chuck disclosed in JP-A-59-74624, in which an insulating layer is formed by oxidizing the electrode surface, aluminum, titanium,
Because it uses alloy materials whose main components are chromium etc.
Although the insulating layer itself has the great advantage of being hard and highly wear resistant, impregnation with resin alone cannot sufficiently prevent voltage resistance deterioration due to pinholes formed by oxidation treatment. There was a FIG.

On the other hand, in an electrostatic chuck with an insulating layer made of a ceramic thin plate made of ferroelectric material, there is no problem with the wear resistance of the insulating layer, but the electrostatic adsorption force (F) is an increasing function of the voltage application time. Become. Therefore, the electrostatic adsorption force (F) is small immediately after voltage is applied, and not only does it take some time to wait until the desired adsorption force is obtained, but permanent polarization occurs when -degree voltage is applied, and it is difficult to turn off the voltage. There is a problem in that the wafer cannot be removed solely by the wafer, and in order to quickly perform the wafer attachment/detachment operation, it is necessary to apply a voltage of the opposite sign for a predetermined time rMi (10 seconds or more).

Therefore, the present invention has been made in view of the above-mentioned conventional problems, and its purpose is to make it possible to attach and detach an adsorbed object in the air or in a vacuum by applying a simple device. In particular, the desorption operation in the atmosphere can be performed quickly, and by changing the material of the insulator, a large adsorption force can be obtained with a small voltage. It is an object of the present invention to provide an electrostatic chuck that can be immediately released from suction and fixation, has little deterioration in pressure resistance or decrease in electrostatic suction force due to abrasion of the surface of an insulating layer, and is also excellent in non-hygroscopicity.

[Means for Solving the Problems] The present invention has been made to achieve the above objects, and its first object is to provide an electrostatic chuck in which an insulator is provided on an electrode formed on a substrate. A ventilation groove with at least one end open is formed on the surface of the holder.

In addition, the second invention is constructed of an organic insulating film made of an organic insulating material as the insulating material 1, and an inorganic insulating film made of an inorganic insulating material formed on the organic insulating film.

[Function] When used in the atmosphere, if the entire surface of the chucked object is in close contact with the suction surface of the electrostatic chuck, when the voltage is turned to O to release the chucked state of the chucked object, the atmospheric pressure However, if ventilation grooves are provided on the insulator, atmospheric pressure will also act on the suction surface through these channels. The inorganic insulating film that protects the organic insulating film is harder and more resistant to wear than organic insulating materials, and prevents deterioration of withstand voltage or decrease in suction power. Furthermore, it is not easily affected by humidity in the air, and protects the insulating film from water, moisture, and the like.

An organic insulating film with poor wear resistance is protected by an inorganic insulating film, so when considering polyimide as an organic insulating film and alumina as an inorganic insulating film, the thickness (d) of polyimide is compared to the thickness of alumina. to make it sufficiently small (1/
30~l/300> 0 For example, 1/3
If the thickness is 0, the relative permittivity (ε*) is small (1/3
As is clear from the above formula, in order to obtain the same electrostatic adsorption force (F) even considering the
710.

In addition, organic insulating materials have less dependence of adsorption force on application time, and moreover, when the voltage is set to O, the polarization becomes O, and no permanent polarization or residual polarization occurs.

[Example] Hereinafter, the present invention will be described in detail based on an example shown in the drawings.

1 is a sectional view taken along the line AA' in FIG. 2 showing an embodiment of the electrostatic chuck and transfer arm according to the present invention, and FIG. 2 is a cross-sectional view of FIG. The cross-sectional view taken along line B-B' and FIGS. 3(a) to 3(d) are schematic configuration diagrams showing a wafer transfer/chucking device using an electrostatic chuck and a transfer arm.

First, the configuration of the wafer transfer/chuck device is shown in FIG.
To briefly explain the operation etc., the member l shown in Fig. 3(a)
is a cassette in which a large number of unprocessed wafers 2 are stored horizontally and vertically at predetermined intervals, and the wafers 2 in this cassette 1 are taken out by a transfer arm 3.

When the transfer arm 3 takes out the wafer 2 from the cassette 1, the transfer arm 3 is moved by a predetermined amount in a horizontal plane by the transfer robot 4.
After being rotated by a predetermined angle, the wafer 2 is inserted into the x*g optical device 5 and transferred to the electrostatic chuck 6, as shown in FIG. 3(b).

When the transfer of the wafer 2 is completed and the transfer arm 3 exits, the Xll exposure device 5 is evacuated and maintained at a predetermined degree of vacuum close to atmospheric pressure. The electrostatic chuck 6 electrostatically attracts and holds the lower surface of the wafer 2 with its upper surface having a high degree of flatness, that is, the suction surface, by applying a voltage, thereby correcting the flatness of the wafer 2 . When preparation for exposure is completed,
The resist formed on the surface of the aperture wafer 2 is irradiated with X-rays emitted from the radiation source by the lens system 7 to perform a predetermined exposure. After the exposure, the electrostatic chuck 6 rotates in a horizontal plane and the above-mentioned A transport arm 8 separate from the X-ray exposure device 5
The electrostatic chuck 6 receives the wafer 2 from the electrostatic chuck 6.

At this time, the voltage applied to the electrostatic chuck 6 is set to 0 to release the chucking of the wafer 2.

When the transfer arm 8 receives and picks up the wafer 2, the transfer robot 9
By Xa! The wafer 2 is pulled out from the g-optical device W5 and transported to a developing device (not shown), which is the next step. After the development process, as shown in FIG. 3(C), the wafer 2 is inserted into a dry etching device 10 which is the next step, and the wafer 2 is placed on an electrostatic chuck 11 disposed in the device. Pass the uke.

The dry etching device WlO applies a predetermined voltage to the discharge electrode 13 by the discharge power source 12, and the gas supply device F1
Etching is performed by ionizing the reactive gas such as xenon fluoride supplied by 4 and colliding with the resist on the wafer 2. Therefore, the inside is evacuated and kept in a low-pressure atmosphere that facilitates discharge. There is. Electrostatic chuck 1 holding wafer 2 in a low pressure atmosphere
To pass the receiver to 1, use -degree dry etching equipment 210 (X
The internal pressure of the line exposure equipment (the same applies to the line exposure equipment) can be raised to atmospheric pressure, and after the wafer 2 is transferred, it can be evacuated and returned to low pressure, or a preliminary chamber can be provided and the pressure controlled in this preliminary chamber. .

When the etching process is finished, the transport arm 16 is moved to the dry etching device 21 by a transport robot 15 different from the one described above.
The wafer 2 is removed from the electrostatic chuck 11 and inserted into another cassette 17 for storage, as shown in FIG. 3(d).

Next, the electrostatic chuck 6 (11) and the transport arm 3 are
The configuration etc. of (8, 16) will be explained in detail based on FIGS. 1 and 2. In addition, in FIG. 2, the dimensions in the thickness direction are shown enlarged.

As shown in FIG. 2, the electrostatic chuck 6 has an appropriate thickness of 2
A chuck body 21 made of ceramics is provided. As shown in FIG. The arm insertion groove 22 has an arm insertion groove 22, and a plurality of narrow grooves 23a to 23f having appropriate groove widths and depths are radially formed on the upper surface. On the upper surface of the main body 21, a plurality of fan-shaped electrodes 24a to 24p are formed in parallel in the circumferential direction and insulated from each other by electroless plating of nickel or sputtering of chromium. An organic insulating film 26A made of an organic insulating material such as polyimide is formed between the electrodes, and an inorganic insulating film 26B made of an inorganic insulating material such as alumina is further formed thereon (FIGS. 1 and 2). (see figure).

The narrow groove 23 has a V-shaped cross section, and one end thereof is open to the outer peripheral surface of the chuck body 21, and the other end thereof is open to the arm insertion groove 22. therefore,
The electrodes 24c, 24e, 24h, 24k, 24m, and 240 sputtered onto the grooves 23a to 23f on the main body 21 are deposited following the grooves 23a to 23f, and a V-shaped groove is formed on the surface thereof. A V-shaped groove is also formed on the surface of the inorganic insulating film 26B stacked thereon with the organic insulating film 26A interposed therebetween.

The electrodes 24a to 24P are arranged in pairs (24a to 24P), which face each other across the center line of the arm insertion groove 22.
4p, 24b-24o, 24cm24n, 24d-24
m, 24e-24, &, 24f-24, 24g-24
j, 24h-24i), such an electrode 2
4, a thin tape for separating the electrodes 24 is adhered to the upper surface of the chuck body 21 in advance, electroless nickel plating or chromium sputtering is performed in this state, and the tape is then removed.

Multi-electronic f [! 24a to 24p all have a thickness of about 3 μm, and a lead wire is formed from one end thereof to the peripheral edge of the main body 21, and is connected to a power source (not shown) via the lead wire. As already mentioned, the 1f pole 24
A portion of the surface corresponding to the narrow groove 23 forms a V-shaped groove, and both ends thereof are open to the inner and outer peripheral surfaces of the chuck body 21.

Specifically, as the organic insulating film 26A, polyimide (SEMICOFINE 5P-910 manufactured by Toshi) is coated on the electrode 24, spin coded at a rotation speed of about 1,0 OOr, p, m, and then 80 1 hour at °C (30
By performing baking treatment for 1 hour at 35°C, a durable polyimide layer with a thickness of about 10 μm was obtained.

The inorganic insulating film 26B protects the organic insulating JII 26A, and is specifically made of, for example, alumina (Af120s).
> on the organic insulating film 26A, and its thickness is about 1 μm.

The V-shaped ventilation groove thus formed on the inorganic insulating film 26B allows atmospheric pressure to act on the suction surface of the wafer 2. Since this ventilation groove is also formed by stacking thin films on the narrow groove 23, it is natural that one end thereof is open to the outer peripheral surface of the electrostatic chuck 6, and the other end is open to the arm insertion groove 22. be.

In this case, one ventilation groove (narrow groove 23) was formed radially, and both ends thereof were opened to the inner and outer peripheral surfaces of the electrostatic chuck 6.
Of course, the present invention is not limited to this, and only one end may be opened, or it may be formed in an annular shape and opened to the lower surface side of the chuck body through a through hole formed through the chuck body 21.

However, the radial grooves have the advantage that when forming the film of the organic insulating material 26A using a spin cord, the grooves do not hinder the movement of the organic insulating material in the radial direction, and unevenness does not occur.

The electrostatic chuck 6 having such a configuration is made of inorganic insulation M2.
Place the wafer 2 on the wafer 6B,
It is operated by sequentially applying voltages of opposite signs (for example, ±200 V) to a to 24p, and the organic insulating film 26
As a charge is generated on A, the wafer 2 is electrostatically attracted and fixed.

In this case, the voltage application sequence is performed by operating a switch in response to a control signal from a control device. As an example of the sequence, first, the electrodes 24a and 24p
+200V and -200V are applied to the electrodes 24b,
24o, and then '! X poles 24c, 24n,...
And finally, +200V and -20V to electrodes 24h and 24L.
0V was applied.

Note that to release the suction and holding of the wafer 2, it is sufficient to turn off the voltage to all the electrodes at the same time, but in order to release the electrodes in a shorter time, it is preferable to apply a voltage of the opposite sign for a short time.

The transfer arm 3 that receives and transfers the wafer 2 to the electrostatic chuck 6 or receives and takes the wafer 2 from the electrostatic chuck 6 has a width that allows it to be inserted into the arm insertion groove 22 of the electrostatic chuck 6. It has a main body 31.

The upper surface of the arm body 31 has V-shaped narrow grooves 32a to 32d.
is engraved and electroplated by electroless nickel plating or chromium sputtering.
3b are formed insulated from each other. electrode 33a,
V-shaped narrow grooves that follow the narrow grooves 32a to 32d of the main body 31 are formed on the surface of the main body 33b.

The narrow groove 32 has an appropriate depth and groove width, and both ends are open to the side surfaces of the arm body 31.

The electrodes 133a and 33b are covered with an insulator 34. The insulator 34 is covered with an organic insulating film 34A made of an organic insulating material, and
, 33b are insulated by a film 34A. The organic insulating film 34A is covered and protected by an inorganic insulating film 34B made of an inorganic insulating material.

Therefore, similarly to the electrostatic chuck 6,
Narrow grooves 35a and 35b corresponding to the narrow grooves 32a and 32b are also formed on the surface of the inorganic insulating film 34B. The organic insulating film 34A is made of polyimide and is formed by coating with a spin code and then baking, and has a thickness of about 10 μm. The inorganic insulating film 34B is made of alumina, for example, as the organic insulating film 11134.
It is formed by sputtering on A, and its thickness is about 1 μm.

Incidentally, V-shaped grooves are formed in the portions of the electrodes 33a, 33b, the 11M edge film 34A, and the inorganic insulating film 34B corresponding to the narrow grooves 32a, 32b.
The grooves form ventilation grooves 35 for applying atmospheric pressure to the surface of the wafer 2 to be attracted. And ventilation grooves 35a, 3
Both ends of 5b are open to the sides of the transfer arm 3.

The transport arm 3 having such a configuration has a planar shape and an electric [!] relationship with the electrostatic chuck 6. The only difference is the number of 33a and 33b, and the other configurations and manufacturing methods are completely the same, so that the electrostatic chuck is substantially the same as the electrostatic chuck 6.

When holding the wafer 2 by suction by the transfer arm 3, it is sufficient to apply voltages with opposite signs (for example, ±200 V) to the electrodes 33a and 33b, similar to the electrostatic chuck 6. When transferring the wafer 2 to the electrostatic chuck 6, insert the transfer arm 3 into the arm insertion groove 22, set the voltage of the @ pole 33 to 0 to release the chuck, and transfer the wafer 2 to the electrostatic chuck 6 instead. 24a
The wafer 2 can be electrostatically attracted and held by applying a voltage to ~24P.On the other hand, the electrostatic chuck 6 can be used to hold the wafer 2 on the transfer arm 3
If the receiver is to be passed to the
It is sufficient to set the voltage to O to release the chucking by the electrostatic chuck 6, and then apply the voltage to 1lfi 33a and 33b.

When transferring the wafer 2, the wafer 2 and the electrostatic chuck 6 or the transfer arm 3 may be moved up and down relative to each other using an appropriate lifting mechanism to prevent friction between the chuck 6 and the transfer arm 3. The electrostatic chuck 6 (the same applies to the transfer arm 3) having the above structure has a great advantage in that it is easier to attach and detach the wafer 2 in the atmosphere compared to conventional electrostatic chucks. In other words, if the entire lower surface of the wafer 2 is in close contact with the electrostatic chuck 6, atmospheric pressure is applied only from above, making it difficult to remove the wafer. However, in the present invention, the suction surface of the electrostatic chuck 6 is ventilated. Since the groove 28 is provided so that atmospheric pressure also acts on the lower surface of the wafer 2, the wafer 2 can be easily removed.

In addition, with the vacuum chuck, a large pressure of 1 kg/C112 is applied to the wafer 2, but with the electrostatic chuck 6, a pressure of 1 kg/C112 is applied to the wafer 2.
Since the pressure can be controlled to be sufficient to transport a wafer of about 500 g/cm2, generation of dust due to wear between the wafer 2 and the electrostatic chuck 6 can be significantly suppressed. Furthermore, if the electrostatic chuck 6 alone is used to transport, receive, and hold the wafer 2 in vacuum or in the atmosphere, only electrical wiring and a power source are required, and the structure is simpler than when using a vacuum chuck. It is much more economical.

In addition, the thickness (d) of the polyimide forming the organic insulating lI26A of the electrostatic chuck 6 is 10 μm, which is significantly smaller than the conventional case in which an insulator made of alumina is simply formed on the electrode, as described above. (1,/20~1
/30), so even if we take into account that the relative dielectric constant (ε*) is small (about 1/3), the same adsorption force (
In order to obtain F), the voltage (V) can be reduced to about 1/10. Further, if the voltage is the same, a large adsorption force can be obtained. Furthermore, when the voltage is set to O, the polarization of the organic insulating material becomes O, and no permanent polarization or residual polarization occurs. Therefore, the dependence of the adsorption force on the application time is small, and the attachment and detachment of the wafer 2 can be carried out in a short time. Furthermore, the dielectric strength of polyimide is 15.7Kv/■-
However, it has the advantage of being extremely large at 317 Kv/-■.

However, polyimide has a low surface hardness and tends to lack wear resistance, so if the insulator 26 is made of polyimide alone, the surface will become rough due to friction.
This will cause deterioration of withstand voltage or decrease in electrostatic adsorption force. Furthermore, since polyimide lacks moisture resistance, when adsorption power is required even in the atmosphere, when water vapor in the air is absorbed and the surface resistance decreases, creepage current flows and the electrostatic adsorption power deteriorates.

In this regard, in the present invention, the organic insulating film 26A made of polyimide is covered and protected by an inorganic insulating film 26B made of alumina, which is hard and has excellent wear resistance, as well as non-hygroscopicity, stability, and weather resistance. Therefore, the drawbacks of polyimide mentioned above can be covered. In addition, the organic insulating film 26
Since insulation is achieved by A, the thickness of the inorganic insulating film 26B itself can be made very thin, about 1 μm.

For example, the inorganic insulating film 26B of this embodiment is only about 1/300 of the thickness of a thick insulating film made of alumina alone, so even though it is a ferroelectric material, the dependence on the application time is about 1/300. It can be reduced to

Furthermore, if the thickness can be reduced, the wafer 2 can be attached and detached with a low voltage, so that it can be used in an apparatus where electric discharge is likely to occur, such as inside a dry etching apparatus.

[Effects of the Invention] As explained above, according to the electrostatic chuck according to the present invention, ventilation grooves are formed on the surface of the insulator formed on the electrode,
Since it is configured so that atmospheric pressure acts on the surface of the adsorbed object, it is possible to quickly remove the adsorbed object when used in the atmosphere, improving workability and handling of the chuck. . Therefore, it can be used instead of a vacuum chuck.

In addition, the insulator includes an organic insulating film and a 'f' on this organic insulating film.
Since it is composed of a certified inorganic insulating film, it is highly wear resistant, with little pressure deterioration or decrease in adsorption power, and has excellent non-hygroscopic properties, so it does not deteriorate even in the air due to water, water vapor, etc. , and durability can be improved.

Further, since the insulating film made of an organic insulating material can obtain a predetermined adsorption force without delay even when a voltage is applied, it is possible to quickly attach and detach the object to be adsorbed, thereby improving workability.

Furthermore, since the adsorption force does not increase even if an object to be adsorbed is left adsorbed and fixed for a long time, accidents such as not coming off when attaching and detaching do not occur, and it is an object of the present invention to provide a highly reliable electrostatic chuck. I can do it. In addition, since the organic insulating film and the inorganic insulating film can be formed thinly, there is no adverse effect on the application time dependence, and a large electrostatic adsorption force can be obtained at a low voltage.
It has great effects, such as being able to be used in equipment that easily generates electrical discharges, such as dry etching equipment, and being suitable for use in both the atmosphere and vacuum.

[Brief explanation of drawings]

1 is a sectional view taken along the line AA' in FIG. 2 showing an embodiment of the electrostatic chuck and transfer arm according to the present invention, and FIG. 2 is a cross-sectional view of FIG. A cross-sectional view taken along the line B-B", FIG. 3 is a schematic configuration diagram showing a wafer transfer-chuck device using an electrostatic chuck and a transfer arm. 2... Wafer, 3.8... Transfer arm, 6 .8.1
6... Electrostatic chuck, 21... Chuck body, 22
...Arm insertion groove, 24.24a-24p...electrode, 26...insulator, 26A...organic insulating film 26.2
6B... Inorganic insulating film, 28... Ventilation groove, 33a, 3
3b... Electrode, 34... Insulator, 34A... Organic insulating film, 34B... Inorganic insulating film, 35... Ventilation groove.

Claims (2)

[Claims] (1) An electrostatic chuck in which an insulator is provided on an electrode formed on a substrate, characterized in that a ventilation groove with at least one end open is formed on the surface of the insulator. (2) In the electrostatic chuck according to claim 1, the insulator is composed of an organic insulating film made of an organic insulating material and an inorganic insulating film made of an inorganic insulating material formed on the organic insulating film. An electrostatic chuck featuring: