JP2006040993A - Electrostatic chuck - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the contamination by particles by suppressing the formation of an electric field around an electrostatic chuck. <P>SOLUTION: In the electrostatic chuck 100, a conductive film 10 is formed on the surface of the electrostatic chuck 100 except for an attraction surface 5, and is electrically grounded by a grounding portion 11. By applying voltage between an internal electrode 3 and a wafer W to be attracted, there is electrostatic force appearing between them and the wafer W is attracted to the electrostatic chuck 100. At that time, the potential around the electrostatic chuck 100 becomes nearly zero due to the grounded conductive film 10, and so the formation of an electric field which attracts particles is suppressed, resulting in preventing the attachment of particles to the wafer W. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electrostatic chuck for attracting and fixing a substrate such as a semiconductor wafer or a reticle.

  The electrostatic chuck is used for fixing and transporting a substrate in various processing apparatuses such as an exposure apparatus, an etching apparatus, and a CVD apparatus in semiconductor manufacturing. As an electrostatic chuck, for example, an electrode is formed on a base material, and a dielectric layer is formed thereon by thermal spraying, or a dielectric layer is bonded with an adhesive (for example, see Patent Document 1), base material An electrode in which an electrode is embedded and a dielectric layer and a base material are integrated (for example, see Patent Document 2) has been proposed.

  By the way, in recent years, as the degree of integration of a semiconductor integrated circuit is improved, the dimension of a pattern to be formed is also reduced, and pattern formation with higher accuracy has been demanded. In the microfabrication technology for semiconductor devices, the progress of lithography technology for forming a pattern plays a central role. However, under a fine design rule of 100 nm or less, it is becoming difficult to cope with lithography techniques using a conventional KrF excimer laser or ArF excimer laser. Therefore, as a lithography technique that can handle such design rules, an EUV lithography technique using extreme ultraviolet light (Extreme UV: EUV), which has the same image forming principle as conventional optical lithography and has a wavelength shorter by one digit or more, is proposed. Has been.

EUV lithography technology handles very fine designs compared to conventional lithography technology, so it is easily affected by particles that are dust in the processing chamber of exposure equipment, and this is a countermeasure against particle contamination. It has become more important than ever.
JP-A-6-291175 (FIG. 2 etc.) Japanese Patent Laid-Open No. 5-304201 (FIG. 1 etc.)

  Since the electrostatic chuck is a jig that applies a voltage to the electrode to attract the substrate, an electric field is slightly generated around the electrostatic chuck by the application of the voltage. According to the study by the present inventors, it has been found that particles can be attracted to the electrostatic chuck by this electric field, and can be one of the causes of contaminating the substrate. Until now, particle contamination caused by the electric field around the electrostatic chuck has not been regarded as a problem. However, effective measures are taken in a microfabrication technology that is easily affected by even slight particle contamination such as EUV lithography. There is a need.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide an electrostatic chuck capable of reliably reducing particle contamination by suppressing generation of an electric field around the electrostatic chuck.

As a result of intensive studies to solve the above problems, the present inventors can suppress the generation of an electric field around the electrostatic chuck by disposing a conductor on a portion other than the attracting surface of the electrostatic chuck. It was possible to obtain the knowledge that particle contamination can be reduced.
That is, according to the first aspect of the present invention, there is provided a static electricity which has an electrode and a dielectric layer covering the electrode, and electrostatically adsorbs an object to be adsorbed on an adsorption surface formed on the dielectric layer by energization. An electrostatic chuck is provided, wherein an electric conductor is provided on all or a part of the surface excluding the attracting surface, and the electric conductor is electrically grounded.

  In the electrostatic chuck of the present invention, generation of an electric field around the electrostatic chuck is suppressed by a simple means of providing a grounded conductor. Therefore, the particles attracted by the electric field are prevented from adhering to the object to be adsorbed, and particle contamination can be reduced.

In the electrostatic chuck, the conductor may be disposed on a surface opposite to the attracting surface.
The conductor is preferably formed as a film. In this case, the film may be formed in a lattice shape or a stripe shape.

  According to a second aspect of the present invention, an exposure apparatus provided with the electrostatic chuck is provided. In this exposure apparatus, since the formation of the electric field around the electrostatic chuck is suppressed, contamination of the object to be attracted by particles can be reliably reduced.

  By using the electrostatic chuck of the present invention, the generation of an electric field is suppressed, and particle contamination resulting therefrom is prevented. Therefore, this electrostatic chuck can be advantageously used as an electrostatic chuck in EUV lithography technology that handles a very fine design.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a drawing schematically showing a cross-sectional structure of an electrostatic chuck 100 according to an embodiment of the present invention. The electrostatic chuck 100 includes a plate-like body 1 made of a dielectric as main components, an internal electrode 3 embedded in the plate-like body 1, a power supply 4, and a conductive film 10. A dielectric layer 2 is formed on the plate-like body 1 so as to cover the internal electrode 3, and an adsorption surface 5 for adsorbing an adsorbed object is formed on the surface of the dielectric layer 2.

  The electrostatic chuck 100 is supported, for example, from the side by a support member (not shown). Further, the electrostatic chuck 100 is configured so that the wafer W as an object to be attracted can be attracted by the attracting surface 5. In FIG. 1, for convenience of explanation, the wafer W is shown separated from the suction surface 5.

  The plate-like body 1 is formed of a dielectric material. The material of the plate-like body 1 is not particularly limited as long as it is a dielectric. For example, ceramics such as alumina, aluminum nitride, silicon carbide, and glass, and resins such as polyimide and polytetrafluoroethylene are used. Can do.

  The internal electrode 3 embedded in the plate-like body 1 is made of, for example, a metal material such as tungsten and is electrically connected to the power source 4. The space between the internal electrode 3 and the adsorption surface 5 is the dielectric layer 2. In FIG. 1, the thickness of the dielectric layer 2 is drawn exaggerated from the actual thickness.

  The plate-like body 1 having the internal electrode 3 can be manufactured by a known method. For example, the plate-like body 1 having the internal electrode 3 can be manufactured by forming the internal electrode 3 on one surface of the plate-like dielectric ceramic by plating and further laminating a dielectric thereon. In addition, a stack of a plurality of dielectric ceramic green sheets is overlaid with a green sheet on which electrode paste is printed in a predetermined pattern, and a predetermined number of green sheets on which electrode paste is not printed are stacked on top of each other. The internal electrode 3 and the plate-like body 1 can be manufactured at the same time by being integrated and fired by a method such as pressing.

  In the present embodiment, the conductive film 10 as the “conductor” covers the entire surface excluding the suction surface 5 of the electrostatic chuck 100 [that is, the side surface and the surface opposite to the suction surface 5 (back surface)]. A coating is formed. Further, the conductive film 10 is electrically grounded by the grounding part 11. The grounding may be performed via a member that supports or fixes the electrostatic chuck 100 when installed in a processing container such as an exposure apparatus.

The material of the conductive film 10 is not particularly limited as long as it is a conductive material. For example, in addition to metals such as silver, copper, nickel, and aluminum, compounds such as titanium nitride and molybdenum silicide can be used. Here, the volume resistivity of the material constituting the conductive film 10 is preferably 1 × 10 ² Ω · cm or less from the viewpoint of obtaining a sufficient electric field suppression effect.

  As a method for forming the conductive film 10, for example, a method such as plating, application of a metal paste, baking, a method of attaching a metal foil with an adhesive, a vapor phase method represented by CVD or PVD, or the like can be employed. .

  In the electrostatic chuck 100 having the above configuration, when a voltage is applied between the internal electrode 3 and the wafer W as an object to be attracted, an electrostatic force is generated to attract the wafer W. At this time, in the electrostatic chuck 100 of this embodiment, the formation of an electric field is suppressed by the grounded conductive film 10. For this reason, the phenomenon of attracting particles to the electrostatic chuck 100 and the wafer W does not occur, and particle contamination can be reduced.

  In addition, the conductive film 10 has a function of removing charges accumulated in the electrostatic chuck 100 when the application of the voltage to the internal electrode 3 is cancelled, so that the wafer W is detached from the electrostatic chuck 100. The effect that it becomes easy is also acquired. Further, when a capacitance sensor or the like is installed in the vicinity of the electrostatic chuck 100, it functions effectively to ensure its accuracy.

In the embodiment of FIG. 1, the conductive film 10 is formed on all surfaces other than the attracting surface of the electrostatic chuck 100, but the conductive film 10 is formed only on a portion close to a region where the generation of an electric field is desired to be suppressed. Also good.
For example, in the electrostatic chuck 101 of the embodiment shown in FIG. 2, the conductive film 12 is formed only on the surface opposite to the attracting surface 5 (the back surface of the electrostatic chuck 101). In this case, generation of an electric field on the back side of the electrostatic chuck 101 can be suppressed.

In FIGS. 1 and 2, the conductive films 10 and 12 are formed as uniform films, but the conductive films are not necessarily formed uniformly on the surfaces of the electrostatic chucks 100 and 101.
For example, in the electrostatic chuck 102 of the embodiment shown in FIG. 3, the conductive film 13 is formed in a lattice shape (knitting shape) on the surface other than the attracting surface 5. The electric field strength generated by the voltage application depends on the magnitude of the voltage applied to the internal electrode 3. Therefore, when the voltage applied to the internal electrode 3 is low, a sufficient action can be obtained even with the lattice-shaped conductive film 13 having an uncovered portion, like the electrostatic chuck 102 of FIG. The same applies to the case where the conductive film is formed in a stripe shape (stripe shape) or a dotted shape (sea island shape).
2 and 3, the configuration other than the conductive film is the same as that of the electrostatic chuck 100 of FIG. 1. Therefore, the same components are denoted by the same reference numerals and description thereof is omitted.

  In the embodiment shown in FIGS. 1 to 3, the conductor is formed as a film, but the shape of the conductor is not particularly limited. For example, the conductor is provided in an arbitrary shape such as a plate shape or a block shape. Is also possible.

  The present invention can be applied regardless of the type of electrostatic chuck, and for example, can be applied to electrostatic chucks such as JP-A-6-291175 and JP-A-5-304201 cited as conventional techniques. As an attraction force of the electrostatic chuck, there is one using a Coulomb force or a Johnson Rahbek force, but the present invention can be applied to both.

  In an electrostatic chuck that attracts using Coulomb force, the dielectric layer has a high resistance, and in order to obtain a necessary attracting force, a higher voltage is often applied than an electrostatic chuck that uses Johnson-Rahbek force. For this reason, the electric field strength inevitably increases and it becomes easy to collect many particles. Therefore, it is very effective to provide a conductor on the electrostatic chuck using Coulomb force.

Next, the operation of the present invention will be described.
FIG. 4 is a diagram schematically showing the state of the electric field E formed around the electrostatic chuck 103 when a voltage is applied. Conventionally, the formation of the electric field E has not been noticed as a cause of particle contamination. However, the electric field E attracts the particles P toward the electrostatic chuck 103 and attracts and places the electrostatic chuck 103 on the substrate (here, the electrostatic chuck 103). It has been found that it can cause contamination (not shown).

When a conductive substrate such as a semiconductor wafer is attracted to the electrostatic chuck 103, the substrate acts as a shielding plate for the electric field E, so that the potential around the substrate becomes equal to zero. Further, since the electrostatic chuck 103 is often fixed to a metal pedestal (not shown) on the back surface thereof, the electric field E is generated even when a voltage is applied to the electrodes to attract the substrate. 103 occurs only in a small area on the side surface.
However, for example, when the electrostatic chuck 103 is constrained on the side surface and used in a state where the back surface is floating, an electric field E is formed around the back surface, so that particle contamination is likely to occur. In particular, in EUV lithography technology that needs to prevent particle contamination as much as possible, particle contamination caused by the electric field E becomes a serious problem. For this reason, in the present invention, a conductor is provided on the surface of the electrostatic chuck as illustrated in FIGS. Thereby, the electric potential around the electrostatic chuck is lowered to a level substantially equal to zero, and the formation of the electric field is suppressed. Therefore, the particles are not attracted toward the electrostatic chuck, and contamination can be reduced.

Next, an exposure apparatus incorporating the electrostatic chuck of the present invention will be described with reference to FIG.
The exposure apparatus 200 is an exposure apparatus for EUV lithography process. In this exposure apparatus 200, EUV light is used as exposure illumination light, and a reduced image of the pattern of the reflective mask 24 (reticle) is formed using the image optical system 26.

  The EUV light is generated by the light source unit 21 including, for example, a laser source, a xenon gas supply source, and the like. The generated EUV light is condensed in the light source unit 21, then irradiated from the window 22, and reaches the condensing mirror 23. An optical path through which EUV light passes is provided in the vacuum chamber 20.

  The condensing mirror 23 condenses the EUV light and reflects it toward the reflective mask 24. The reflective mask 24 is attracted and held on the lower surface of the first electrostatic chuck 25. The first electrostatic chuck 25 is supported on the side by a support member (not shown).

  When EUV light is reflected by the reflective mask 24, the EUV light is patterned by pattern data from the reflective mask 24. The patterned EUV light reaches the wafer W attracted and held by the second electrostatic chuck 27 through the image optical system 26. The image optical system 26 in FIG. 5 includes four reflecting mirrors, and EUV light reflected by the reflective mask 24 is a concave first mirror 28, a convex second mirror 29, a convex third mirror 30, and a concave surface. Reflected in the order of the fourth mirror 31, an image with a reduced mask pattern is formed.

  Although the detailed illustration is omitted here, the second electrostatic chuck 27 is supported on the side portion by the support member, and, like the electrostatic chuck 100 of FIG. A conductive film is formed, and the conductive film is electrically grounded.

In the exposure apparatus 200 having the above configuration, the second electrostatic chuck 27 includes a grounded conductive film, so that a voltage can be applied between the internal electrode (not shown) and the wafer W. Generation of an electric field is suppressed. Therefore, particle contamination can be prevented in EUV lithography.
In addition to the second electrostatic chuck 27, the present invention can be applied to the first electrostatic chuck 25 for fixing the reflective mask 24 (reticle), for example, and a grounded conductive film can be provided. It is.

  Next, although an Example and a comparative example are given and this invention is demonstrated further in detail, this invention is not restrict | limited by this. In the following examples and the like, tests were performed on two types of electrostatic chucks, one based on Coulomb force and one based on Johnson Rabeck force.

Electrostatic chuck with Coulomb force:
A copper electrode was formed on one surface of an alumina substrate having a diameter of 210 mm and a height of 10 mm by plating. A polyimide film having a thickness of 0.025 mm was pasted thereon to obtain an electrostatic chuck 104 using this as a dielectric layer.

Electrostatic chuck with Johnson Rabeck force:
A tungsten electrode was embedded in aluminum nitride powder, integrally fired, and processed so that the thickness of the dielectric layer was 2 mm, to obtain an electrostatic chuck 105 having a diameter of 210 mm and a height of 10 mm.

(1) Potential measurement:
A voltage was applied to the electrodes of the electrostatic chucks 104 and 105 to attract the silicon wafer, and the potential around the electrostatic chuck at that time was measured.
As shown in FIG. 6, the center of the electrostatic chucks 104 and 105 is the origin, the direction parallel to the flat electrode surface is x and y, and the direction perpendicular to the electrode surface is z and the origin is 0, 0, 0. The following positions A to D were taken as potential measurement points.

A: x, y, z = 0, 0, 15 (position 10 mm from the back surface)
B: x, y, z = 0, 0, 55 (position 50 mm from the back surface)
C: x, y, z = 115, 0, 0 (position 10 mm from the side surface)
D: x, y, z = 155, 0, 0 (position 50 mm from the side surface)

A voltage of 1000 V was applied to each of the electrostatic chucks 104 and 105, and potentials at points A to D were measured.
Similarly to FIG. 1, the potentials at points A to D are also measured in the case where a film (conductive film) is formed by applying a silver paste to a thickness of 0.020 mm on the surface other than the adsorption surface. did.
The test results for the electrostatic chuck 104 are shown in Table 1, and the test results for the electrostatic chuck 105 are shown in Table 2.

  From the measurement result of the electric potential, in the case of the electrostatic chuck without the conductive film, the generation of the electric field was confirmed, whereas in the case where the conductive film was formed, the leakage electric field was measured at any of the measurement points A to D. It was found that the formation of the conductive film is effective for shielding the leakage electric field. Further, the electric field shielding action was confirmed by both the electrostatic chuck 104 by the Coulomb force and the electrostatic chuck 105 by the Johnson-Rahbek force.

(2) Measurement of the number of particles:
Using the electrostatic chuck 104 on which the conductive film was formed, EUV lithography processing was performed in the same exposure apparatus as in FIG. When the number of particles of 0.5 μm or less adhering to the processed wafer W was measured with a particle counter, the number of particles was reduced to about 1/3 compared to a conventional electrostatic chuck without a conductive film. The effect of the conductive film was confirmed.

  The present invention has been described with reference to various embodiments. However, the present invention is not limited to the above-described embodiments, and various modifications can be made.

  The electrostatic chuck of the present invention can be used as a member of a semiconductor manufacturing apparatus such as an exposure apparatus, and is particularly suitable for use in an EUV lithography system capable of forming a very fine pattern using extreme ultraviolet light.

The drawing which shows the outline | summary of the electrostatic chuck of 1st Embodiment of this invention. Drawing which shows the outline | summary of the electrostatic chuck of 2nd Embodiment of this invention. Drawing which shows the outline | summary of the electrostatic chuck of 3rd Embodiment of this invention. The schematic diagram explaining the state of the electric field formed around an electrostatic chuck. The schematic diagram which shows schematic structure of exposure apparatus. Drawing which shows the measurement point of the electric field around an electrostatic chuck.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1; Plate-like body 2; Dielectric layer 3; Internal electrode 4; Power source 5; Adsorption surface 10, 12, 13; Conductive film 11; Grounding part 100, 101, 102, 103, 104, 105; Exposure equipment W wafer

Claims (5)

An electrostatic chuck having an electrode and a dielectric layer covering the electrode and electrostatically adsorbing an object to be adsorbed on an adsorption surface formed on the dielectric layer by energization;
An electrostatic chuck characterized in that a conductor is provided on all or part of the surface excluding the attracting surface and the conductor is electrically grounded.   The electrostatic chuck according to claim 1, wherein the conductor is disposed on a surface opposite to the attracting surface.   The electrostatic chuck according to claim 1, wherein the conductor is formed as a film.   The electrostatic chuck according to claim 3, wherein the coating is formed in a lattice shape or a stripe shape.   An exposure apparatus comprising the electrostatic chuck according to any one of claims 1 to 4.

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