JPH11251417A - Electrostatic chuck - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the deterioration of attractive force, and foreign matters from sticking to an object to be attracted, by forming an insulator layer on an attraction surface on which the object to be attracted is attracted by can electrostatic force, and dispensedly forming a plurality of conductive layers on the insulator layer. SOLUTION: A substratum 1b which is sintered integrally is arranged on a base substratum 1a composed of ceramics, and an insulating member 1 forming a substratum of an electrostatic chuck S is constituted. Via holes reaching an electrostatic electrode 5 and an electrode 7 are formed in the insulating member 1. Conducting lines such as Cu, Au, Ag, W and Mo are connected with the via holes, and power supplying lines 6, 8 are arranged so that terminals are connected with the conducting lines. An insulator layer 3 is formed on an attraction surface which generates an electrostatic attraction force on the insulating member 1 by inputting power in the power supplying line 6. A plurality of conductive layers 4 are dispersedly formed on the insulator layer 3. Thereby the deterioration of attractive force and sticking of foreign matters on an object to be attracted can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a semiconductor manufacturing apparatus,
The present invention relates to an electrostatic chuck used for fixing and transporting a semiconductor wafer such as silicon or a glass plate for a liquid crystal display device in a liquid crystal display device manufacturing apparatus and the like.

[0002]

2. Description of the Related Art In recent years, an electrostatic chuck has been used instead of a clamp ring for fixing and transporting a semiconductor wafer (hereinafter abbreviated as a wafer) such as a silicon wafer in a semiconductor manufacturing apparatus. An electrostatic chuck is effective for fixing and transporting a silicon wafer in a dry etching apparatus, a CVD apparatus, a PVD apparatus, and the like.

[0003] Such an electrostatic chuck has a structure in which an electrostatic electrode is buried in an insulator.
F = S / 2 × ε0 × εr × (V / d) ²
Here, F is the attraction force, S is the area of the electrostatic electrode, ε0 is the dielectric constant of vacuum, εr is the relative dielectric constant of the insulator, V is the applied voltage, and d is the thickness of the insulating layer.

For example, as shown in FIGS. 4 (a) and 4 (b), a single-pole type electrostatic chuck is shown.
When a voltage is applied from a power supply 13 between the electrostatic electrode 12 and an object 14 such as a wafer,
The object 14 is attracted to the attracting surface 11a of the insulator 11 by electrostatic force (Coulomb force). Further, a through hole 11b is provided in the insulator 11, and a cooling gas or a heating gas is supplied from the through hole 11b,
The object 14 is cooled or heated, or the through-hole 1
A pusher pin for detaching the object 14 from 1b is pushed up. FIG. 2B is a sectional view taken along line AA in FIG.

Further, the electrostatic electrode 12 has a structure that is not exposed to the outside in order to prevent discharge. Therefore, the outer peripheral portion of the insulator 11 and the periphery of the through hole 11b
The electrodeless portion 11c has no electrostatic electrode 12 inside.

FIGS. 7 (a) and 7 (b) show a single-pole type electrostatic chuck. In the case of a bipolar type, a plurality of electrostatic electrodes 12 are provided on an insulator 11 so that the electrostatic electrodes of each other are separated. A voltage is applied between 12.

An insulator 11 forming a base of the electrostatic chuck.
As a material for the material, ceramics such as alumina are frequently used. In recent years, it has been proposed to use an aluminum nitride ceramic having high corrosion resistance to halogen plasma and high thermal conductivity (Japanese Patent Laid-Open No. 6-151332).
Reference). Tungsten (W), molybdenum (Mo), or the like is used as a conductive material for an electrode buried inside the insulator 11 and functioning as a resistance heating element or the like.
The method of manufacturing the insulator 11 is to print a metal paste such as W, Mo, or the like in a predetermined pattern on a green sheet of aluminum nitride, and to laminate and sinter another green sheet of aluminum nitride. General.

As another conventional example, it has been proposed to provide a gas flow path on the adsorption surface of the insulator 11 or to provide a groove on the adsorption surface to reduce the contact area with the object to be adsorbed. (See JP-A-4-304941).

A manufacturing process using a semiconductor manufacturing apparatus in which this electrostatic chuck is incorporated is performed in a high vacuum.
Moreover, it is often performed in a high temperature of 300 ° C. or higher.

[0010]

However, when an electrostatic chuck is used in a vacuum and at a high temperature as described above,
There is a problem that conductive foreign matter is easily formed on the surface of the insulator 11.

This is because polycrystalline ceramics have a myriad of surface defects (voids) when viewed microscopically, and the grinding of organic substances, grinding stones, etc., generated during the grinding of ceramics and the like. This is because a cleaning solution such as dirt, acetone, toluene, and methanol remains in voids on the surface, and even after performing cleaning with a detergency, these foreign substances cannot be completely removed.

If heating is performed while the foreign matter is present on the surface of the insulator 11, its components are carbonized, resulting in a conductive thin film or reaction layer. The biggest problem caused by the formation of such a conductive carbonized layer is that there is no electrostatic force for adsorbing an object to be adsorbed such as a semiconductor wafer.

Further, when the object to be adsorbed is adsorbed in the above state, there is a problem that foreign substances on the surface of the insulator 11 adhere to the object to be adsorbed. It was remarkable.

Accordingly, the present invention has been completed in view of the above circumstances, and an object of the present invention is to provide an effect of conductive foreign matters remaining and formed on the surface of a ceramic insulator constituting a base of an electrostatic chuck, that is, An object of the present invention is to solve the problems of deterioration of the attraction force and adhesion of foreign matter to an object to be attracted.

[0015]

According to the present invention, there is provided an electrostatic chuck comprising an insulator provided with an electrostatic electrode and an adsorption surface for adsorbing an object to be adsorbed by an electrostatic force. And a plurality of conductive layers dispersed on the insulator layer.

In the present invention, preferably, the thickness of the insulator layer is 1 to 10 μm, the specific resistance is 1 × 10 ¹⁰ Ωcm or more, and the thickness of the conductive layer is 1 to 10 μm and the specific resistance is 1 to 10 μm. × 10 ³ Ωcm or less.

[0017] Preferably, the insulator is made of a ceramic containing alumina, aluminum nitride or boron carbide as a main component.

The present invention solves the problems of deterioration of the attraction force due to conductive foreign matter remaining on the surface of an insulator for an electrostatic chuck and adhesion of foreign matter to an object to be attracted by the above configuration.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The electrostatic chuck of the present invention will be described in detail below. 1 to 3 show the present invention, and FIG.
Is a cross-sectional view of an insulator 1 which is a flat plate such as a disc and forms a base (main body) of the electrostatic chuck S, FIG. 2 is a plan view of the insulator of FIG. 1 as viewed from above, and FIG. It is a graph which shows a temporal change.

In FIGS. 1 and 2, reference numeral 1 denotes an insulator forming a base (main body) of the electrostatic chuck S, 1a denotes a base base made of ceramic, and 1b is disposed on the base base 1a and integrally sintered. The base 3 is an insulator layer formed on the base 1b by vapor deposition or the like, 4 is a conductive layer formed on the insulator layer 3 by vapor deposition or the like, and 5 is an electrostatic layer for an electrostatic chuck. The electrode, 6 is a power supply line for supplying power to the electrostatic electrode 5, 7 is a heater of a resistance heating type or the like, and 8 is a power supply line for supplying power to the heater 7.

The insulator layer 3 of the present invention comprises an electrostatic chuck 1
When heating is continued at about 500 ° C. for several hours or more in a vacuum of Pa or less, grinding dust and cleaning liquid remaining on surface defects of the ceramic insulator 1 which is a polycrystalline substance become conductive carbides. Prevents the adsorption force from deteriorating due to conductive foreign matter. That is, the insulator layer 3 is formed so as to cover the carbide, and the insulator layer 3 functions as a dielectric polarization layer, so that the attraction force does not deteriorate.

In addition, the conductive layer 4 is made of a material to be adsorbed and the insulator layer 3.
And the conductive layer 4 is in direct contact with the object to be adsorbed. In this case, there is no potential difference between the conductive layer 4 in contact with the object to be adsorbed and the object to be adsorbed, and no electrostatic attraction force is generated in this portion. The amount of foreign substances adsorbed is reduced. In addition, since there is a gap between the object to be adsorbed and the insulator layer 3 where the attraction force is generated, there is almost no foreign matter adsorbed from the insulator layer 3 to the object to be adsorbed. Is extremely small.

In the present invention, the material of the insulator 1 may be a resin or the like, but preferably a ceramic.
Preferably, ceramics containing alumina (Al ₂ O ₃ ), aluminum nitride (AlN), or boron carbide (B ₄ C) as a main component, which have good mechanical properties at high temperatures and break even at high temperatures Hateful. Further, barium titanate (BaTiO ₃ ) or calcium titanate (Ca
If a high dielectric constant ceramic such as TiO ₃ ) is used, the attraction force can be increased. In addition, a material containing sapphire, which is a single crystal of alumina, as a main component can also improve mechanical properties.

In the case of aluminum nitride, a high-purity product having an AlN content of 99% by weight or more is preferable, and the sintered body has almost no grain boundary phase and has excellent corrosion resistance. More preferably, the content is 99% by weight or more and 99.5% by weight or less. In order to further improve corrosion resistance, Si is added at 1500
ppm or less, preferably 1000 ppm or less. In addition, Na, Ca, Fe and the like may be contained in total as 2000 ppm or less as other impurities.

The specific resistance (volume resistivity) of aluminum nitride is 1 × 10 ¹⁰ Ωcm at a high temperature of about 500 ° C.
The above is good, and in this case, it functions as a good electrical insulator 1.

Then, an insulator layer 3 is formed on the adsorption surface of the insulator 1 by a vapor deposition method such as a sputtering method, and the thickness is preferably 1 to 10 μm. If it is less than 1 μm,
The thickness tends to vary, and it cannot function sufficiently as a coating layer. If the thickness exceeds 10 μm, the strain with the insulator 1 increases, the adsorption power decreases, and the film formation time is too long, resulting in poor productivity. The material of the insulator layer 3 is preferably the same ceramic as the insulator 1 from the viewpoint of the coefficient of thermal expansion and the like, more preferably a ceramic containing aluminum nitride, alumina or boron carbide as a main component. 10 ¹⁰ Ωcm
That is all.

On the adsorption surface of the insulator layer 3, a PVD method,
The conductive layer 4 having a thickness of 1 to 10 μm is formed by a vapor deposition method such as a CVD method, an ion plating method, or a sputtering method, a plating method, or a coating method of applying a conductive paste by a printing method. Is a square, as shown in FIG.
A shape having a symmetry such as a rectangular shape such as a rectangle and a rhombus, a polygonal shape having a pentagon or more, and other shapes such as a circle and an ellipse are preferable. More preferably, it is a square as shown in the figure, and one side of the square is 1 to 10 mm. If it is less than 1 mm, it is difficult to form the conductive layer 4 using a masking of stainless steel or the like, and if it exceeds 10 mm, the non-adsorption area becomes too large, the adsorption power is reduced, and it becomes difficult to adsorb the object to be adsorbed.

If the number of the conductive layers 4 is as small as possible, a high attraction force can be obtained. However, if the number is too small, the object to be adsorbed cannot be floated from the insulator layer 3.
Three to thirty are preferred. Further, the area of the conductive layer 4 in a plane viewed from above is preferably 2 to 10% with respect to the electrostatic electrode 5 for adsorption for the same reason as described above, and more preferably 2 to 10%.
5%. Further. The distribution is not particularly limited since the overall attraction force does not change, but it is preferable to uniformly distribute (disperse) as shown in FIG. 2 in order to make the attraction force uniform without unevenness. .

When the thickness of the conductive layer 4 is less than 1 μm,
The thickness tends to fluctuate, the gap between the insulator 1 and the to-be-adsorbed body is insufficient, and the to-be-adsorbed body is likely to come into contact with portions other than the conductive layer 4. If the thickness of the conductive layer 4 exceeds 10 μm, the attraction force tends to decrease, and the film formation time is too long, resulting in poor productivity and large distortion with the insulator 1, which tends to cause cracks.

The material of the conductive layer 4 is preferably one that reduces the deformation due to the difference in thermal expansion coefficient with the insulator 1.
g, Cu, Ni, etc., plastically deformable soft metals; compounds of the above-mentioned elements, such as Ti, W, Mo, Si, etc., and WC, TiC, TiN, etc., having substantially the same thermal expansion coefficient as the insulator 1; alloys, etc. Conductive ceramics such as SiC and B ₄ C or diamond-like carbon having a specific resistance of 1 × 10 ³ Ωcm or less may be used. In order to prevent deterioration of characteristics such as semiconductivity due to contamination of the semiconductor wafer, Ti, Al, Si, etc. and their compounds, alloys, etc. are more preferable.

The specific resistance of the conductive layer 4 is set to 1 × 10 ³ Ωc in order to exhibit an attraction force by electrostatic force (Coulomb force).
m or less.

As for the power supply lines 6 and 8 in FIG. 1, via holes are formed in the insulator 1 so as to communicate with the electrostatic electrodes 5 and the electrodes 7, and Cu, Au, Ag, W, and Mo are formed in the via holes.
And the like, and a terminal may be connected to the conductor.

The adsorbent used in the present invention is Si, G
e, GaAs, InAs, InGaAs, etc., a semiconductor wafer, a glass plate for a liquid crystal display device, etc., as long as it can be adsorbed by electrostatic force.

In the above embodiment, the description has been given of the monopolar electrostatic chuck in which the object to be attracted is one electrode. However, a bipolar electrostatic chuck in which a plurality of electrodes 2 are formed and a voltage is applied between these electrodes 2 is provided. It is also applicable to chucks.

Thus, the present invention provides a method for removing
This has the effect of preventing adsorption force from deteriorating due to the formed conductive foreign matter and preventing foreign matter from adhering to the object to be attracted.

By the way, in the electrostatic chuck of the present invention, when electric power is input to the power supply line 6 for electrostatic attraction, a potential difference between the attracted object placed on the insulator 1 and the electrostatic electrode 5 is generated. As a result, an electrostatic attraction force based on Coulomb's law is generated between the insulator layer 3 and the object to be attracted. However, since there is no potential difference between the conductive layer 4 in contact with the object and the object, no electrostatic attraction force is generated in this portion.

Further, when the electrostatic chuck is continuously heated to about 500 ° C. for several hours or more in a vacuum of 1 Pa or less, grinding dust and cleaning liquid remaining on the surface defects of the polycrystalline ceramic become conductive carbides. turn into. However, since the insulator layer 3 is formed so as to cover the carbide, the insulator layer 3 functions as a dielectric polarization layer, and the adsorption force does not deteriorate.

It should be noted that the present invention is not limited to the above embodiment, and various changes may be made without departing from the scope of the present invention.

[0039]

Embodiments of the present invention will be described below.

(Embodiment) The electrostatic chuck S shown in FIGS. 1 and 2
Was produced and configured by the following steps (1) to (8).

(1) AlN having an average particle diameter of about 1.2 μm and a purity of 99% containing 900 ppm of Si as an impurity.
After adding a binder and a solvent to the powder and mixing to prepare a slurry, a plurality of green sheets having a thickness of 0.4 mm were obtained by a doctor blade method.

(2) A paste for an electrostatic electrode 5 and a paste for an electrode 7 whose viscosity is adjusted by mixing W powder and AlN powder having a specific surface area of 2 m ² / g or more on ^two green sheets are screen-printed. A conductive layer for each of the electrostatic electrodes 5 and the electrodes 7 was formed.

(3) a green sheet on which the electrodes 7 are formed,
A green sheet on which the electrostatic electrode 5 is formed and a green sheet on which the insulator layer 3 is to be formed are laminated, and are stacked at 80 ° C. and 50 ° C.
Thermocompression bonding was performed at a pressure of kg / cm ² .

(4) Thereafter, a disc is formed by cutting, followed by vacuum degreasing and baking in a vacuum atmosphere of about 2000 ° C., so that the purity is 99% or more and the Si content is 1%.
An aluminum nitride-based sintered body having a thermal conductivity of 100 W / mK or less and 000 ppm or less was obtained.

(5) The method of supplying power to the electrostatic electrodes 5 and the electrodes 7 was performed by using power supply terminal fittings which were metallized and joined to via holes connected to the electrostatic electrodes 5 and the electrodes 7.

(6) The aluminum nitride sintered body was ground to prepare an insulator 1 comprising a base substrate 1a having an outer diameter of about 8 inches and a thickness of 10 mm and a substrate 1b having a thickness of 300 μm. .

(7) The insulator layer 3 made of AlN and having a thickness of 2 μm was formed on the adsorption surface of the insulator 1 by a sputtering method.

(8) When viewed from above, the planar shape is 5 m on a side
An electrically conductive layer 4 having a square shape of m and a thickness of 2 μm was formed on the insulator layer 3 in a state as shown in FIG. The material of the conductive layer 4 is a soft metal that can be plastically deformed and does not cause contamination of the semiconductor wafer.
l. When the conductive layer 4 was formed, a stainless steel mask in which a portion on which the film was to be formed on the insulator layer 3 was hollowed out was used, and a film was formed only on a necessary portion.

First, the state of adhesion of the conductive foreign matter when the Si wafer was sucked using the electrostatic chuck S was investigated. The chamber for the semiconductor manufacturing apparatus in which the electrostatic chuck S was incorporated was evacuated to a predetermined degree of vacuum, and the temperature of the electrostatic chuck S was raised to 500 ° C. and held. Next, a voltage was applied to the electrostatic electrode 5 to attract the Si wafer. At this time, there was no potential difference between the conductive layer 4 in contact with the Si wafer and the Si wafer because no potential difference was generated between them.

As described above, since no attraction force is generated between the conductive layer 4 and the Si wafer and there is a gap at the portion where the attraction force is generated, the number of foreign particles adhering to the Si wafer is as follows. Decreased sharply. Conventionally, when a Si wafer is directly adsorbed on the insulator 1, the average particle diameter of the adsorbed Si wafer is 0.1 mm.
In contrast to 10,000 or more particles of 1 μm or more in total, in the present invention, 10 or less particles of the same size.
When the specific resistance of the conductive layer 4 exceeded 1 × 10 ³ Ωcm, an attraction force was generated in the conductive layer 4 as well, and the number of particles of the same size attached increased to about 8,000. Therefore, the specific resistance of the conductive layer 4 is preferably 1 × 10 ³ Ωcm or less.

Next, the electrostatic chuck S was heated to 500 ° C. and held, and the change with time in the attraction force was examined.
As a comparative example, when a type in which a Si wafer was directly adsorbed on the insulator 1 was used, the electrostatic chuck S of the present invention showed a substantially constant adsorption force, whereas the electrostatic chuck S of the present invention showed a decrease in the adsorption force Was remarkable. The results are shown in FIG. 3, in which circles indicate the present invention and triangles indicate comparative examples.

This is because grinding dust and cleaning liquid remaining on the surface defect of the insulator 1 become a conductive carbonized film upon heating, and the adsorption force of the insulator 1 is reduced in the comparative example. It is considered that in the present invention in which the insulator layer 3 is formed, the attraction force does not decrease.

[0053]

According to the present invention, an insulating layer is formed on an adsorption surface,
By dispersing and laminating a plurality of conductive layers on the insulator layer, conductive foreign matters remaining on and forming on the ceramic insulator surface forming the base of the electrostatic chuck adhere to the object to be attracted. Is greatly reduced, and deterioration of the attraction force due to the presence of foreign matter is suppressed and prevented.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an electrostatic chuck S according to the present invention, and showing an insulator forming a base of the electrostatic chuck S.

FIG. 2 is a plan view of the insulator of FIG. 1;

FIG. 3 is a graph showing the change over time in the attraction force of the electrostatic chuck S of the present invention and the comparative example.

4A and 4B show a conventional electrostatic chuck as a whole, wherein FIG. 4A is a plan view of an insulator, and FIG. 4B is a cross-sectional view of a basic configuration of the entire electrostatic chuck.

[Explanation of symbols]

 1: Insulator 1a: Base substrate 1b: Base 3: Insulator layer 4: Conductive layer 5: Electrostatic electrode 6: Power supply line 7: Electrode 8: Power supply line

Claims (3)

[Claims] 1. An electrostatic chuck comprising an insulator provided with an electrostatic electrode and an adsorption surface for adsorbing an object to be adsorbed by electrostatic force, wherein an insulator layer is formed on the adsorption surface, and the insulator is An electrostatic chuck comprising a plurality of conductive layers dispersedly formed on a layer. 2. The insulator layer has a thickness of 1 to 10 μm and a specific resistance of 1 × 10 ¹⁰ Ωcm or more, and the conductive layer has a thickness of 1 to 10 μm and a specific resistance of 1 × 10 ³ Ωcm or less. The electrostatic chuck according to claim 1, wherein 3. The electrostatic chuck according to claim 1, wherein said insulator is made of a ceramic containing alumina, aluminum nitride, or boron carbide as a main component.