JPH11260898A - Sample to be chucked - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sample to be chucked for evaluation of an electrostatic chuck. SOLUTION: For a body to be chucked 1 by an electrostatic chuck, at least a part of a chucking fast of the body 1 is made of a conductor 2 such as silicon wafers, a means is provided for jetting compressed gas on the chucking face of the electrostatic chuck. As the compressed gas jetting means, a porous body 3 is mounted on the outside of the conductor 2, by constituting the body to be chucked and a gas jetting face of the porous body 3 is exposed on the chucked face, to make it capable of embodying.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an object to be chucked for inspecting the chucking characteristics of an electrostatic chuck used in a semiconductor manufacturing apparatus or the like.

[0002]

2. Description of the Related Art The application of an electrostatic chuck for holding a silicon wafer to many semiconductor manufacturing apparatuses such as an exposure apparatus, an etching apparatus, a sputtering apparatus, and a CVD apparatus has been studied. The exposure apparatus is used at room temperature in an atmospheric environment, and the etching apparatus and the sputtering apparatus are used at low to medium temperatures (0 to 200 ° C.) under reduced pressure. In addition, CVD equipment is used at low to medium temperatures (200 to 600 ° C) under reduced pressure. As a method for evaluating the electrostatic chuck, a method utilizing frictional force is disclosed in Japanese Patent Application Laid-Open No. 02-249935, but it is not suitable for measurement under various environments as described above. Also, when actually inspecting the electrostatic chucking characteristics of a silicon wafer in an etching apparatus or the like, a gas such as He is passed from the back surface of the electrostatic chuck through a gas supply hole, and the gas supply pressure when the wafer is desorbed is measured. Seems to be.

With the recent progress of electrostatic chucks, a type in which a dielectric material on the outermost surface of the electrostatic chuck has a slight conductivity, exhibits a Johnsen-Rahbek effect, and obtains a high attraction force. Has become mainstream. It is known that this type of electrostatic chuck has a high attraction force in a vacuum environment, but has a significantly lower attraction force under a normal atmospheric environment (T. Watanabe et al.
Jpn. J. Appl. Phys. Vol. 31 (1992) pp. 2145-2150).
An appropriate method for measuring the attraction force has not yet been proposed for such environment-dependent characteristics.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a to-be-adsorbed object capable of measuring electrostatic attraction characteristics accurately without depending on the surrounding environment.

[0005]

SUMMARY OF THE INVENTION According to the present invention, there is provided an object to be attracted which is attracted by an electrostatic chuck, wherein at least a part of the surface to be attracted is formed of a conductor such as a silicon wafer, An object to be adsorbed is characterized in that means for ejecting compressed gas is provided. The gist of the means for ejecting the compressed gas is to attach a porous body to the outer periphery of the conductor constituting the object to be adsorbed and to expose the gas ejection surface of the porous body on the surface to be adsorbed.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The electrostatic attraction force can be measured by ejecting a compressed gas from a surface to be attracted and detecting the gas supply pressure when the object to be attracted leaves the electrostatic chuck. Hereinafter, the principle of measuring the electrostatic attraction force using the object to be attracted according to the present invention will be described with reference to FIG.

FIG. 1 shows a to-be-adsorbed body 1 composed of a conductor and a porous body mounted on the outer periphery thereof. The suction surface 10 is
Each of the exposed surfaces of the conductor 2, the porous body 3, and the to-be-adsorbed substrate 6 is formed, and these exposed surfaces are on the same plane. The electrostatic chuck 11 facing the object 1 is a single-pole electrostatic chuck. Attraction is performed by applying a voltage to the conductor 2 and the film-like electrode 13 on the electrostatic chuck side via the respective power supply units 7 and 15 by the DC power supply 17. When providing both positive and negative poles on the electrostatic chuck side to make it a bipolar type,
It is not necessary to apply a voltage to the object to be adsorbed.

The porous body 3 constituting the body 1 to be adsorbed has a frame shape and is arranged so as to surround the conductor 2. The gas is introduced from a gas supply source (not shown) through an air supply unit 8 through a filter and a dryer, and is uniformly supplied to the porous body through a ventilation groove 9 provided along the entire periphery of the back surface of the porous body. The supplied gas passes through the inside of the porous body and is
Jets are ejected from the surface of the porous body exposed to the suction surface 16 of the electrostatic chuck. The dry gas ejected from the frame-shaped porous body of the present invention functions as an air curtain and prevents gas from entering the adsorption surface from the external environment. This makes it possible to measure the electrostatic attraction force in a constant low humidity environment.
As the gas to be supplied, either He or dry air can be used according to the use environment.

In the present invention, the surface from which the gas is ejected and the surface to be attracted are located on the same plane. As a result, gas hardly flows out in the suction state, and the pressure of the gas existing in the gap between the suction surface and the suction surface of the electrostatic chuck is substantially the same as the gas supply pressure inside the porous outer frame 5. The effective area of the gap gas film S _a, the supply pressure of the gas and P _a, electrostatic per unit area acting area of the disposed inside the porous body frame 4 conductors S _e, to the conductor adsorption When the force and F _e, the moment of detachment of the adsorbent from the balance of forces, the _{S a · P a = S e} · F e. Advance, if seeking S _a from the pressure of the gas that can float a known load, S _e is because it is known, the electrostatic adsorption from the above equation by knowing P _a at the time of withdrawal of the adsorbent The force F _e is exactly determined.

When a voltage is applied between the electrostatic chuck and the object to be attracted while the object to be attracted is being floated by the supply of air, the attractor is attracted by the electrostatic attraction force. . If a gap sensor is provided on either side, the response of desorption can be understood. The object to be attracted is a kind of air bearing, and if the relationship between the gap and the load is known, it is possible to measure the electrostatic attraction force with the gap.

It is preferable that the porous body is electrically insulating.
For example, a porous body of alumina ceramics can be used. As the porous body, one having a small pore diameter is preferable from the viewpoint of uniform supply of gas, for example, having a pore diameter of 1 to 3
Those having a porosity of 10 to 30% at μm are suitably used. The conductor is a silicon wafer when applied to a semiconductor manufacturing apparatus. The object to be adsorbed 1 is composed of an electric conductor 2, a porous body 3, a power supply section 7, and an air supply section 8 on a ceramic body 6 to be adsorbed.
Are assembled and assembled. In assembling, an organic adhesive can be used for low-temperature use, and glass fusion bonding or the like is used for high-temperature use.

The flatness of the adsorption surface including the gas ejection surface of the object to be adsorbed must be finished to 5 μm or less, preferably 1 μm or less. Also, it is preferable that the surface roughness is reduced to an average surface roughness of 1 μm or less by polishing or the like. By increasing the shape accuracy, it is possible to measure the electrostatic attraction force with good reproducibility.

The electrostatic chuck 11 is formed by bonding a dielectric 12 having a film electrode 13 to an upper surface of an electrostatic chuck base 14 made of insulating ceramics. The dielectric is selected from alumina, aluminum nitride, silicon carbide, and silicon nitride based on the operating temperature of the electrostatic chuck. In order for the Johnsen-Rahbek effect to be exerted, the volume resistivity is 10 ⁸ to 10 ¹² Ωcm, preferably 10 ¹⁰ to 10 ¹² Ωcm.
It must be adjusted to 10 ¹¹ Ωcm. 10 ¹⁰ to 10 ¹¹ Omega by the alumina-based adding an oxide of a transition metal element such as titania (TiO ₂₎ or chromia (Cr ₂ O ₃₎
It is known that a dielectric having a volume resistivity of cm can be obtained. For the electrodes, ordinary electrode materials such as Cu, Mo, W, and Ag are selected according to the preparation method. As a typical manufacturing method, there is a method of attaching an electrode to a dielectric and joining the electrode to a base using an adhesive. Alternatively, a method in which a high-melting-point material such as W is screen-printed on the dielectric before firing and then fired together with the substrate is also applicable. Typical dielectric thickness is
The thickness is 200-1000 μm, and the electrode thickness is 20-200 μm.

[0014]

EXAMPLE An object to be adsorbed shown in FIG. 1 was experimentally manufactured. The substrate to be adsorbed is alumina that exhibits electrical insulation, and the porous body attached to it is also alumina, with a pore diameter of 1 μm and a porosity of 30%.
Was used. The conductor was a small piece of silicon cut from a silicon wafer. After assembling, the surface to be attracted was ground so as to be on the same plane, and was wrapped with diamond abrasive grains to a flatness of 1 μm or less.

The test electrostatic chuck is one in which electrodes are attached to an alumina-based dielectric and assembled using a base and an adhesive. Dielectric material is alumina (Al ₂ O ₃ )
It is a sintered body to which 5 wt% of titania (TiO ₂ ) is added, and has a volume resistivity of 2 × 10 ¹⁰ Ωcm and a thickness of 300 μm.

The suction force measurement test was performed after supplying dry air to the porous body attached to the object to be suctioned to set the gap between the object to be sucked and the suction surface of the electrostatic chuck to a constant low humidity state. Figure
Fig. 2 shows the electrostatic attraction force when a wafer was attracted by applying a voltage of 500 V under an atmospheric pressure environment of 18 ° C and a relative humidity of 23%. The electrostatic attraction force when the gap was zero was determined from the supply pressure when the object to be adsorbed was detached by adsorbing in advance at a low supply pressure and gradually increasing the supply pressure. The value when the gap is large is obtained by previously floating the object to be adsorbed by air supply and converting the amount of change in the gap when a voltage is applied thereto into a load. The curve in the figure is a theoretical curve of the electrostatic attraction force calculated based on the Johnsen-Rahbek effect with the gap in the close contact state set to 1.3 μm. The agreement between experiment and theory was good. In addition, as a result of providing a gap sensor on the object side and measuring the response, the time required for adsorption and desorption was 0.5 seconds in both cases.

[0017]

According to the present invention, there is provided an object to be inspected for electrostatic chuck, wherein a compressed gas jetting means is provided on the object side. The present suction target can be manufactured from a small size to a large size, but by using a small size suction target, the distribution of the suction force in the electrostatic chuck can be measured.
In the future, as the diameter of the silicon wafer increases, the area of the electrostatic chuck also increases, so that a quick inspection of the distribution of the attraction force in the chuck is required. In the present invention, the object to be adsorbed is placed at an arbitrary position on the electrostatic chuck, the supply pressure of the gas is increased after voltage application, and the supply pressure when the object to be detached is read to measure the electrostatic attraction force. As a result, a more rapid and accurate inspection than before can be performed.

[Brief description of the drawings]

FIGS. 1A and 1B are views showing an object to be adsorbed using a porous body as compressed gas blowing means, wherein FIG. 1A is a plan view of an adsorption surface, FIG. FIG. 3 is a cross-sectional view of an electrostatic chuck facing a surface.

FIG. 2 is an experimental result showing the relationship between the electrostatic attraction force and the gap (○
Mark) and the theoretical curve.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Adsorbed body 2 ... Conductor 3 ... Porous body 4 ... Porous body frame 5 ... Porous body outer frame 6 ... Adsorbed body base 7 ... Adsorbed body power supply part DESCRIPTION OF SYMBOLS 8 ... Air supply part 9 ... Vent groove 10 ... Adsorbed surface 11 ... Electrostatic chuck 12 ... Dielectric 13 ... Film-shaped electrode 14 ... Electrostatic chuck base 15. ..Electrostatic chuck power supply section 16 ... Suction surface 17 ... DC power supply

Claims (3)

[Claims] In an object to be attracted which is attracted by an electrostatic chuck, at least a part of a surface to be attracted is formed of a conductor,
An object to be attracted, characterized in that means for ejecting a compressed gas toward an electrostatic chuck attraction surface is provided in a part of the object to be attracted. 2. A compressed gas ejecting means is characterized in that a porous body is mounted on an outer peripheral portion of a conductor constituting an object to be adsorbed, and a gas ejection surface of the porous body is exposed on the surface to be adsorbed. The object to be adsorbed according to claim 1. 3. The adsorbed body according to claim 1, wherein the conductor constituting the adsorbed body is a silicon wafer.