JPS63299137A - Sample holding device - Google Patents

Abstract

PURPOSE:To correct a sample in a desired flatness by equalizing the potential of a part of a sample holding face composed of a conductive substance to a potential of high or low voltage side to increase an attraction force without necessity of altering an electrode area, a permittivity and an applying voltage. CONSTITUTION:An electrode 3 of high (or low) voltage side and an electrode 4 of low (or high) voltage side are disposed on the same flat face of the top of an electrostatic chuck body 6. An insulatively dielectric layer 2 covering the electrode 3, a conductive material 5 covering the electrode 4, a DC power supply 7 connected between the electrodes 3 and 4, and an insulator 8 having sufficiently low permittivity than an insulator for forming the dielectric layer are provided. With this construction, when a voltage V is applied between the electrodes 3 and 4, the potential of a semiconductor wafer 1 becomes 0V, an attraction force F becomes a function of the voltage V, the thickness (d) and the permittivity epsilon1 of the dielectric layer to generate an attraction force as large as twice. That is, it does not receive a force from a sample holding face equi-potential thereto, but the potential difference which contributes to an electrostatic attraction force by square becomes double as large as a conventional one. Thus, a sample having a large warpage can be held in a preferable flatness state by the large attraction force.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention provides a sample holding device that straightens and holds a conductor or semiconductor sample that may be warped in its natural state so that it is in contact with a flat holding surface. Regarding.

[Prior Art] Generally, when an integrated circuit pattern is transferred onto a sample such as a silicon wafer using a semiconductor exposure apparatus, or when the sample is inspected, it is necessary to hold and fix the sample on a flat surface.

Conventionally, mechanical, vacuum, and electric chucks have been used as such holding means. Of these, electric chucks, or electrostatic chucks, are relatively easy to handle and can be used even in a vacuum. Because of this, it is a key technology in the field of semiconductor manufacturing, and much research and development has recently been carried out and it is being put into practical use.

This electrostatic chuck uses the attractive force of two capacitor plates charged with opposite polarities, consisting of an electrode plate and an insulator layer with a strong dielectric constant (referred to as an insulating dielectric layer in this application). Consisting of Conventionally considered electrostatic chucks include: ■The chuck itself has one electrode, and the sample is used as the other electrode.■The chuck itself has electrodes charged with opposite polarities on the same plane. There are two things.

FIG. 2 is a sectional view showing the electrostatic chuck in case (2) above. In the figure, the chuck itself of the electrostatic chuck main body 6 has only one electrode 3, and an insulating dielectric layer 2 is placed on the electrode 3.
is covered. On the other hand, FIG. 3 is a sectional view showing the electrostatic chuck in case (2) above. In the device shown in the figure, two electrodes, an electrode 3 on the high voltage side and an electrode 4 on the low voltage side, are arranged on the same plane. In these figures, 1 is a wafer placed on an insulating dielectric layer 2 .

In the electrostatic chuck shown in FIG. 2, when a voltage V is applied between the electrode 3 and the semiconductor wafer 1 by the DC power supply 7, the attraction force F acting on the semiconductor wafer 1 is F-(1/2)ε0ε
1'(V/d)2S...-(1). However, F: Attractive force ε0: Vacuum permittivity ε,: Dielectric constant of the insulating electrolytic layer ■: Applied voltage d: Thickness of the insulating layer S: Area of the electrode, and the electrostatic chuck shown in Fig. 3 When a voltage V is applied between the electrode 3 on the high (or low) voltage side and the electrode 4 on the low (or high) voltage side, the potential of the semiconductor wafer 1 becomes V/2, and the attractive force acting on the semiconductor wafer 1 F becomes .

In this way, the electrostatic chuck holds the sample by applying a predetermined voltage to generate an attractive force between the electrostatic chuck and the sample, such as a semiconductor wafer.

[Problems to be Solved by the Invention] However, such electrostatic chucks have a lower suction force than the vacuum chucks used in most semiconductor manufacturing equipment, and therefore cannot be used for samples with large warpage. Currently, it is not possible to correct the flatness to .

In order to increase this attractive force, that is, the value of F in equations (1) and (2), it is possible to increase the dielectric constant of the insulating layer, increase the applied voltage, and make the insulating layer thinner. However, when selecting a material with a high dielectric constant in order to increase the dielectric constant of the insulating layer, there are many restrictions, such as the need for no wear and good workability. Further, even in the method of increasing the applied voltage, there are problems of discharge and dielectric breakdown of the dielectric layer. Furthermore, there are limits to the methods for making the insulating layer thinner.

In view of these problems, an object of the present invention is to provide a sample holding device that attracts and holds a sample by electrostatic attraction by applying a potential difference from the sample holding device main body side as shown in FIG.
The object of the present invention is to increase suction force without changing the electrode area, dielectric constant, and applied voltage, and to make it possible to straighten and hold a sample to a desired flatness.

[Means and effects for solving the problem] In order to achieve the above object, the present invention provides two high voltage side and low voltage side
In a sample holder, which is equipped with various types of electrodes on the main body of the sample holder, and which attracts and holds a conductive or semiconductor sample through an insulating dielectric by electrostatic attraction, a part of the sample holding surface is made of a conductive material. The part of the holding surface is made to have a potential equal to the potential of the high voltage side or the low voltage side.

According to this configuration, when the sample is placed on the holding surface, the potential of the sample becomes equal to the high voltage side or the low voltage side due to contact with the conductive substance. That is, although no force is applied from the sample holding surface which has the same potential as this, the potential difference that contributes squarely to the electrostatic attraction is twice as large as in the conventional case.

Therefore, for example, even if the area of the electrode that contributes to the first power of electrostatic attraction is halved compared to the conventional method, twice as much electrostatic force will act on the sample if other conditions remain the same.

[Example] Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 1 is a sectional view showing the structure of an electrostatic chuck (sample holding device) according to an embodiment of the present invention. In the same figure, 6
is an electrostatic chuck main body in which an electrode 3 on the high (or low) voltage side and an electrode 4 on the low (or high) voltage side are arranged on the same plane at the top.

2 is an insulating dielectric layer covering the electrode 3; 5 is the electrode 4;
The electrically conductive material covering the top, 7 is a DC power supply connected between the electrodes 3 and 4, and 8 is an insulator having a sufficiently lower dielectric constant than the insulator forming the insulating dielectric layer.

In this configuration, if a voltage V is applied between the electrodes 3.4,
The potential of the semiconductor wafer 1 is Ov, and the attractive force F is F=(1/2)e:. a, 2 (V/D) 2(S
/2)-(1/4)ε. ε 2 (y 2/D2)
5...(3). Therefore, according to this embodiment, compared to the conventional example shown in FIG. occurs.

However, in this case, although the suction force is twice as large, since no suction force is generated above the negative electrode, differences in suction force occur depending on the location. Therefore, in order to make the attraction as uniform as possible over the entire surface, it is convenient to subdivide the patterns of both the positive and negative electrodes and distribute them uniformly over the entire surface. FIG. 4 shows an example of this in which both the positive and negative electrodes are arranged in a grid pattern with the grid size as small as possible, and FIG. 5 is an enlarged perspective view of a part of FIG. 4. .

[Other Embodiments] FIG. 6 is a partial sectional view showing the structure of an electrostatic chuck according to another embodiment of the present invention.

In this apparatus, as an application example shown in FIG. 4.5, metal with good thermal conductivity is used for the sample and the main body of the holding device. In the figure, 8 is an insulator with a low dielectric constant such as epoxy or alumina ceramics, and 9 is a metal with good thermal conductivity. metal 9
The electrode serves as one electrode and at the same time forms a sample holding surface. With this structure, the heat that enters the sample during exposure can be transferred to the metal body 9 with good thermal conductivity and released. Therefore, it can also be suitably used for the purpose of temperature control.

[Effects of the Invention] As explained above, according to the present invention, the potential of the sample to be held becomes equal to the potential on the low voltage side or the high voltage side,
Since the potential difference related to electrostatic attraction is twice that of the conventional one, for example, even if the area of the electrode related to electrostatic attraction is halved compared to the conventional one, the applied voltage, the thickness of the insulating dielectric layer, and the dielectric constant will be reduced. If they are the same, twice as much suction force can be generated. In other words, a larger suction force makes it possible to hold a highly curved sample in a state of good flatness.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a sample holding device according to an embodiment of the present invention, FIGS. 2 and 3 are sectional views of a conventional sample holding device, and FIG. 4 is a sectional view of a sample holding device according to an embodiment of the present invention. Figure 5 is a cross-sectional view showing a grid pattern of conductive material and insulator coated on the surface of the electrode when the electrode pattern used in the device is in the form of a grid. The perspective view and FIG. 6 are partial cross-sectional views of a sample holding device according to another embodiment of the present invention. 1: Sample, 2: Insulating dielectric layer, 3: High (or low) voltage side electrode, 4: Low (or high) voltage side electrode, 5: Conductive material, 6: Sample holding device main body, 7: Power supply, 8: Insulator, 9: Metal with good thermal conductivity. Patent Applicant Canon Co., Ltd. Representative Patent Attorney Tetsuya Ito Representative Patent Attorney Tatsuo Ito Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1. A sample holding surface including a first surface made of an insulating dielectric and a second surface made of a conductive material; a sample holding device body having a first electrode substantially parallel to the surface of the sample holding surface, on which a conductive or semiconductor sample is adsorbed, and a sample holding device body having a first electrode substantially parallel to the surface of the sample holding surface; A sample holding device comprising a voltage source that generates a potential difference. 2. The insulating dielectric material is a coating on the first electrode, and the conductive material is a coating on a second electrode connected to the voltage source, and the first and second 2. The sample holding device according to claim 1, wherein the electrodes are provided on substantially the same plane. 3. The sample holding device according to claim 1, wherein the first and second surfaces are uniformly distributed in a grid pattern. 4. The sample holding device main body is formed mainly of a metal with good thermal conductivity as the conductive substance, and the insulating dielectric and the first electrode are placed in a recess provided on the sample holding surface side of the metal forming body. 4. A sample holding device according to claim 1 or 3, wherein: