KR20110064665A - Dipole type electrostatic chuck by using electric field gradient - Google Patents

Abstract

PURPOSE: A dipole type electrostatic chuck using an electric field gradient is provided to ununiformly form an electric field on an electrostatic plate by a dipole electrode to generate an electric field gradient, thereby chucking an insulating substrate by strong electrostatic power. CONSTITUTION: A dipole electrode(102) is located in a dielectric plate(101) or one side of the dielectric plate. The dielectric plate is formed of ceramics made of particles whose diameters are shorter than 10 micro meters. Dipole electrodes are separated and have a first electrode(102a) and a second electrode(102b) whose polarities are different. The first electrode and the second electrode are reciprocally arranged.

Description

DIPOLE TYPE ELECTROSTATIC CHUCK BY USING ELECTRIC FIELD GRADIENT}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic chuck, and more particularly, to an electrostatic chuck having an improved electrode structure of an electrostatic plate for adsorbing an adsorbate.

An electrostatic chuck is a mechanism that adsorbs a substance to be adsorbed by using electrostatic force, and is widely used for fixing or moving a semiconductor substrate or a glass substrate for a display by chucking. In addition, the electrostatic chuck is applied to a plasma processing apparatus for forming or etching a thin film using plasma gas to provide wafer temperature control and chucking functions.

1 is a main configuration diagram of a general ceramic electrostatic chuck. As shown in FIG. 1, the electrostatic chuck has an electrostatic plate 10 having a metal electrode 13 in the form of a plate therein.

The electrostatic plate 10 includes a dielectric positioned at the top and bottom of the electrode 13, and the DC power supply 20 is connected to the electrode 13. Here, the upper and lower dielectrics based on the electrode 13 are usually formed of the same ceramic.

Typically, the electrostatic plate 10 is manufactured integrally by inserting the electrode 13 having a high melting point into the dielectric and then sintering the ceramic at a high temperature of 1500 ° C. or higher.

According to the above configuration, when the substrate to be adsorbed is placed on the top surface of the electrostatic plate 10 and a high voltage DC power is supplied, polarization occurs in the dielectric. In this process, the surface of the electrostatic plate 10 and the surface of the substrate are generated. The electrostatic charge is induced in the substrate so that the substrate is tightly absorbed and fixed to the upper surface of the electrostatic plate 10 by the Coulomb force or the Johnsonsen-Rahbek force.

The electrostatic plate 10 is generally used in a form bonded to the metal base member 14. When the electrostatic chuck is applied to the plasma processing apparatus, the DC power supply device 20 and the high frequency power supply device 30 for generating plasma are connected to the electrode 13 and the base member 14 in the electrostatic plate 10, respectively. In this case, the electrostatic chuck may provide an electrostatic attraction force for tightly fixing the substrate and may serve as a bias electrode opposite to the electrode for generating plasma.

According to the above configuration, when the substrate to be adsorbed is placed on the top surface of the electrostatic plate 10 and a high voltage DC power is supplied, polarization occurs in the dielectric. In this process, the surface of the electrostatic plate 10 and the surface of the substrate are generated. The electrostatic charge is induced in the substrate so that the substrate is tightly absorbed and fixed to the upper surface of the electrostatic plate 10 by the Coulomb force or the Johnsonsen-Rahbek force.

The coulomb type electrostatic chuck using the coulomb force fixes the wafer by using electrostatic attraction between particles having different charges on the upper and lower surfaces of the electrostatic plate 10. In general, the coulomb type electrostatic chuck is designed to have a volume resistance value of 10 ¹⁴ Ω · cm or more, and exhibits good desorption performance, but in order to provide a sufficiently large electrostatic attraction force uniformly across the substrate, a high voltage is applied. There is a disadvantage to be authorized. Too high a voltage causes various unexpected problems such as residual charge problem in the plasma apparatus.

Johnson-Label type electrostatic chuck using Johnson Lavec force can provide sufficient adsorption force to chuck the adsorbed material by air gap principle even at relatively low voltage compared to Coulomb type electrostatic chuck. According to the known air gap principle, since the electric current flows at the contact point portion where the low-resistance electrostatic plate and the adsorbed material come into contact with each other, the electric charge is blocked in the space formed between the contact points, thereby generating strong electrostatic attraction. The attraction force can be obtained by using this attraction force. In the Johnson-Lavec type electrostatic chuck, the attraction force is provided depending on the capacitance of the air gap rather than the capacitance of the electrostatic plate itself.

Johnson-Labeck type electrostatic chuck has lower operating voltage than Coulomb type electrostatic chuck, so it has less advantage of interfering with bias voltage generated by high frequency power in plasma device and less likely arcing. . However, Johnson-la bekhyeong electrostatic chuck is the volume resistivity of the electrostatic plate decreases much current flows toward the wafer absorbate complex because it may give an electrical damage to the wafer to the volume resistivity of the electrostatic plate 10 ⁹ ~ 10 ¹³ Ω and about cm It is desirable to design.

Since the principle of the electrostatic chuck having the above structure is based on the capacitance model, the electrostatic force is effectively generated only when the dielectric is placed between the counter electrodes to which the DC voltage is applied. Therefore, the electrostatic chuck can be very usefully applied to a conductive semiconductor wafer or a substrate on which electrodes are deposited on one side.

However, in the case of various insulating substrates such as glass substrates and sapphire substrates used in display or light emitting diode manufacturing processes, electrostatic power is hardly generated due to the nonconductive material having a high volume resistance of 10 ¹⁴ Ω · cm or more. Accordingly, in a general light emitting diode manufacturing process, a method of mechanically pressing an outer surface of a substrate using a predetermined clamp ring is widely used. In this method, a chipping problem is continuously generated at the outer surface of the substrate and mechanically pressed. The part cannot be used as a good product, which causes a decrease in yield.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object thereof is to provide a bipolar electrostatic chuck having an electrode structure capable of forming an electric field gradient on an electrostatic plate to enable chucking of an insulating substrate. .

In order to achieve the above object, the present invention discloses a bipolar electrostatic chuck having a structure having a bipolar electrode on a dielectric plate.

That is, the present invention provides an electrostatic chuck for adsorbing an adsorbate using electrostatic force, comprising: a dielectric plate; And a bipolar electrode disposed on the inside or one surface of the dielectric plate and spaced apart from each other and having a first electrode and a second electrode provided with different electrical polarities.

Preferably, the plurality of bipolar electrodes may be arranged in a width direction of the dielectric plate, and the first electrode and the second electrode may be alternately disposed.

The volume resistance and surface resistance of the dielectric plate is preferably 10 ¹¹ Ω · cm or less.

The thickness of the dielectric plate is 0.8 mm or less, and the electrode width and the electrode spacing of the first electrode and the second electrode are preferably 0.5 mm or more.

The dielectric plate may be formed of a ceramic made of particles of 10 μm or less.

The bipolar electrostatic chuck may further include a metal support bonded to the dielectric plate.

The electrostatic chuck according to the present invention can chuck an insulating substrate such as, for example, a sapphire substrate with a strong electrostatic force by generating an electric field gradient by forming an uneven electric field on an electrostatic plate (dielectric plate) by a bipolar electrode.

Therefore, unlike the prior art, there is no need to mechanically press the insulating substrate by using the ceramic clamp ring, and thus there is an advantage of eliminating the chipping problem that occurred at the outside of the insulating substrate.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, terms or words used in the specification and claims should not be construed as having a conventional or dictionary meaning, and the inventors should properly explain the concept of terms in order to best explain their own invention. Based on the principle that can be defined, it should be interpreted as meaning and concept corresponding to the technical idea of the present invention. Therefore, the embodiments described in the specification and the drawings shown in the drawings are only the most preferred embodiment of the present invention and do not represent all of the technical idea of the present invention, various modifications that can be replaced at the time of the present application It should be understood that there may be equivalents and variations.

2 is a cross-sectional view showing the main configuration of the electrostatic chuck according to an embodiment of the present invention.

Referring to FIG. 2, an electrostatic chuck according to an embodiment of the present invention may include a dielectric plate 101 and a first electrode 102a and a second electrode provided in the dielectric plate 101 and provided with different electrical polarities. And a bipolar electrode 102 composed of 102b).

The dielectric plate 101 is configured in the form of a sintered body of dielectric ceramic. Here, as the dielectric ceramic, alumina (Al ₂ O ₃ ), yttria (Y ₂ O ₃ ), aluminum nitride (AlN), or the like having excellent dielectric properties is preferably used.

The area of contact between the electrostatic chuck and the adsorbate affects the electrostatic force and dechucking time and also affects the flow of cooling gas between the dechuck and the adsorbate, so that the dielectric plate 101 can be It is preferable that this embossing process be carried out.

In order to generate sufficient electrostatic force of about 1 kgf / cm 2 or more even when chucking an insulating substrate such as a glass substrate or a sapphire substrate, the volume resistance and the surface resistance of the dielectric plate 101 preferably have a value of 10 ¹¹ Ω · cm or less. Do. As such, since the ceramic dielectric having a low resistance value may be reduced in electrostatic power due to excessive leakage current, the dielectric plate 101 is preferably composed of particles of 10 μm or less, thereby minimizing leakage current.

The bipolar electrode 102 is composed of a first electrode 102a and a second electrode 102b disposed to be spaced apart from each other inside or on one surface of the dielectric plate 101. The '+' terminal of the DC power supply device 200 is connected to the first electrode 102a, and the '-' terminal of the DC power supply device is connected to the second electrode 102b so that the first electrode 102a and the second electrode are connected. 102b forms an electrode pair with different electrical polarities. According to this structure, since an electric field directed from the first electrode 102a to the second electrode 102b is locally formed, a gradient of the electric field is generated on the dielectric plate 101.

When the plurality of bipolar electrodes 102 are arranged in the dielectric plate 101 in the width direction, as shown in FIG. 3, the first electrode 102a and the second electrode 102b are alternately disposed. desirable. According to such an electrode arrangement structure, an uneven gradient of an electric field is generated over the entire surface of the dielectric plate 101, so that it is possible to chuck an insulating substrate 1 such as a glass substrate or a sapphire substrate with a stable and strong adsorption force.

Referring to FIG. 4, the electrode width W and the electrode gap G of the first electrode 102a and the second electrode 102b are finely designed in a range of 0.5 mm or more, respectively, and the dielectric plate 101 A thin design of 0.8 mm or less is effective in terms of electrostatic power generation. When two bipolar electrodes 102 are arranged as shown in FIG. 4, the electric force lines 150 are distributed as shown in FIG. 5.

As a metal material constituting the bipolar electrode 102, gold (Au), silver (Ag), copper (Cu), tungsten (W), molybdenum (Mo) or an alloy of two or more thereof may be employed.

When the bipolar electrode 102 is configured to be inserted into the dielectric plate 101, the upper and lower dielectric ceramics may be simultaneously sintered based on the bipolar electrode 102. Alternatively, when the upper and lower dielectric ceramics have independent properties, the upper and lower dielectric ceramics may be formed in a hybrid bonded form.

As shown in FIG. 6, the bipolar electrode 102 may be formed in various patterns on the dielectric plate 101. 6 illustrates an electrode structure in which the region of the first electrode 102a and the region of the second electrode 102b are alternately formed with the insulation patterns 103 arranged in a zigzag form as a boundary.

Preferably, the metal support 100 is bonded to the lower portion of the dielectric plate 101. The metal support 100 is preferably made of a metal body having a relatively high thermal conductivity such as aluminum so as to effectively transmit the temperature of the body to the adsorbed material placed on the dielectric plate 101. Alternatively, the metal support 100 may be made of a stainless steel or titanium-based metal body that can be maintained at a thermal expansion coefficient of 13 × 10 ^-6 / ℃ or less.

When the bipolar electrostatic chuck is applied to the plasma processing apparatus, the bipolar electrode 102 and the metal support 100 formed on the dielectric plate 101 are respectively provided with a DC power supply device 200 and a high frequency power supply device 300 for generating plasma. Is connected. In this case, the bipolar electrostatic chuck provides an electrostatic attraction force for tightly fixing the insulating substrate 1, and may serve as a bias electrode opposite to the electrode for generating plasma.

Since the bipolar electrostatic chuck having the above configuration is operated to generate an electric field gradient by the bipolar electrode 102 disposed in the dielectric plate 101, even if the adsorbed material is an insulating substrate, it can be chucked with a strong electrostatic attraction force. . In fact, when 500 V is applied to the bipolar electrode 102 in the DC power supply device 200, it is possible to adsorb a substrate having a volume resistance of 10 ¹⁴ Ω · cm or more like a sapphire substrate.

Although the present invention has been described above by means of limited embodiments and drawings, the present invention is not limited thereto and will be described below by the person skilled in the art to which the present invention pertains. Of course, various modifications and variations are possible within the scope of the claims.

The following drawings, which are attached to this specification, illustrate preferred embodiments of the present invention, and together with the detailed description of the present invention serve to further understand the technical spirit of the present invention, the present invention includes matters described in such drawings. It should not be construed as limited to.

1 is a cross-sectional view showing the main configuration of a ceramic electrostatic chuck according to the prior art,

2 is a cross-sectional view showing the main configuration of a bipolar electrostatic chuck according to an embodiment of the present invention;

3 is a schematic diagram showing an electric field gradient formed on the dielectric plate according to the present invention;

4 is a schematic diagram showing an arrangement structure of a bipolar electrode provided according to the present invention;

FIG. 5 is a schematic diagram showing a distribution of electric force lines in FIG. 4;

6 is a photograph showing the appearance of an electrostatic chuck actually manufactured according to the present invention.

DESCRIPTION OF THE REFERENCE NUMERALS OF THE DRAWINGS

100: metal support 101: dielectric plate

102: bipolar electrode 102a: first electrode

102b: second electrode 150: magnetic field lines

200: DC power supply device 300: high frequency power supply device

Claims (6)

An electrostatic chuck for adsorbing a substance to be adsorbed using electrostatic force, Dielectric plates; And And a bipolar electrode disposed on the inside or one surface of the dielectric plate and spaced apart from each other, the first electrode having a first electrode and a second electrode having different electrical polarities. The method of claim 1, The bipolar electrode is arranged in plurality in the width direction of the dielectric plate, And the first electrode and the second electrode are alternately arranged. The method of claim 1, A volume resistance and a surface resistance of the dielectric plate are 10 ¹¹ Ω · cm or less. The method of claim 1, The thickness of the dielectric plate is 0.8 mm or less, A bipolar electrostatic chuck, wherein the electrode width and the electrode spacing of the first electrode and the second electrode are 0.5 mm or more. The method of claim 1, The dielectric plate is a bipolar electrostatic chuck, characterized in that formed by a ceramic of particles of 10㎛ or less. The method of claim 1, And a metal support joined to the dielectric plate.

Images