JP2000100917A - Electrostatic chuck - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent particles such as dusts, etc., deposited to an electrostatic chuck plate from moving to a sample by providing posts piercing the electrostatic chuck plate to form a small clearance to avoid direct contact between the electrostatic chuck plate and the sample. SOLUTION: Eight polyimide-made dielectric posts 4 are provided at equal spacings on the same circle of an electrostatic chuck 2 and a plurality of holes 5 piercing the posts 4 are provided, corresponding to the number and positions of the posts 4, thereby forming a clearance 6 of several tens μm between a wafer sample 1 and electrostatic chuck plate 2, the wafer sample 1 being put over the posts 4 on a sample stage. When a specified voltage is applied to the electrostatic chuck plate 2, the wafer sample 1 receives an electrostatic chucking force while owing to the posts 4 protruding several tens μm from the electrostatic chuck plate 2 surface, the wafer sample 1 never directly contacts the electrostatic chuck plate 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an electrostatic chuck device for electrostatically holding a flat sample such as a wafer. In particular,
The present invention relates to an electrostatic chuck device suitable for a scanning electron microscope for semiconductor wafer inspection and the like.

[0002]

2. Description of the Related Art Conventionally, an electrostatic chuck has been widely used as a means for holding a wafer sample on a sample stage in a scanning electron microscope for semiconductor wafer inspection or the like. FIG. 1 shows a basic example of an electrostatic chuck, and FIG. 2 shows a basic example of a scanning electron microscope equipped with an electrostatic chuck device. 1A is a plan view, and FIG. 1B is a cross-sectional view. 1 is a wafer sample, 2 is an electrostatic chuck plate, and 3 is a holding table. Although not shown, the electrostatic chuck plate 2 is connected to a control power supply for applying a voltage for giving an electrostatic attraction force. In FIG. 2, 10 is a column of an electron microscope kept in a high vacuum, 11 is an electron gun for generating an electron beam, 12 and 13 are a focusing lens and an objective lens for focusing and narrowing the electron beam, and 14 is A scanning coil 15 for scanning the electron beam two-dimensionally, 15 is a sample chamber also maintained in a high vacuum, 1
Reference numeral 6 denotes a sample stage installed in the sample chamber,
X, Y movement, tilt movement, etc. can be performed freely, and a desired position on the sample can be observed with a microscope. The sample stage 16 has the upper surface thereof as the holding table 3, the electrostatic chuck plate 2 is attached, and the wafer sample 1 is placed thereon. The sample 1 is loaded from outside the sample chamber into the sample chamber via an airlock chamber (not shown) and mounted on the electrostatic chuck plate 2 of the sample stage 16. Reference numeral 17 denotes a detector for detecting secondary electrons generated from the sample by the irradiation of the electron beam. Further, although not shown, an electric circuit for controlling these elements is connected to the electron gun 11, the lenses 12, 13, the scanning coil 14, the sample stage 16, and the like, and an electric circuit for amplifying a signal from the detector 17 and the like. A CRT or the like for displaying an electron microscope image is connected. In such an apparatus, it is necessary to minimize the attachment of fine particles such as dust to the wafer sample surface during operation. However, there has been a problem that, when the electrostatic chuck and the wafer sample come into contact with each other, fine particles such as dust adhered to the electrostatic chuck are transferred to the wafer to be adsorbed. For this reason, various measures have been taken to prevent this. For example, in Japanese Patent Application Laid-Open No. 63-95644, a step having a concave portion and a convex portion is provided on an insulating film of an electrostatic chuck to improve the adverse effect of dust adhesion. Further, in Japanese Patent Application Laid-Open No. Hei 5-6933, a concave portion is formed on an adsorption surface to make an area ratio of a contact portion with an adsorption object 10 to 30.
% Makes it difficult to attach garbage.

[0003]

However, as described above, simply applying irregularities or the like to the suction surface has not been able to sufficiently prevent adhesion of dust, and has not been satisfactory.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem, and has as its object to provide an electrostatic chuck device that further prevents dust from adhering.

[0005]

According to the present invention, there is provided an electrostatic chuck apparatus for a sample stage on which a sample such as a wafer is mounted, comprising: an electrostatic chuck plate having a plurality of through holes; By mounting a plurality of posts penetrating through the sample stage on the sample stage and projecting the posts slightly from the surface of the electrostatic chuck plate, a sample such as a wafer does not directly touch the electrostatic chuck plate. It is characterized by doing so.

[0006]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIGS. 3A and 3B show an embodiment of the electrostatic chuck device according to the present invention, wherein FIG. 3A is a plan view and FIG. 3B is a sectional view. In FIG. 3, the same reference numerals as those of the conventional device of FIG. 2 indicate the same components. In the drawing, reference numeral 4 denotes posts, which are made of, for example, a dielectric material made of polyimide, and are provided at eight locations on the same circumference at equal intervals. Reference numeral 5 denotes a plurality of holes formed in the electrostatic chuck plate 2 for penetrating the posts 4, and a plurality of holes 5 are provided in accordance with at least the number and positions of the posts. Numeral 6 denotes a gap formed between the wafer sample 1 and the electrostatic chuck plate 2 by providing the post 4, which is several tens μm of 100 μm or less.

Next, the operation of such a configuration will be described. The wafer sample 1 is loaded into the sample chamber from outside the sample chamber via an air lock chamber (not shown) and the like.
6 on a plurality of posts 4. Subsequently, when a predetermined voltage is applied to the electrostatic chuck plate 2 from a control power supply for electrostatic chuck (not shown), the wafer sample 1
It receives an electrostatic attraction force from the electrostatic chuck plate 2. At this time, the post 4 protrudes slightly (several tens of μm) from the surface of the electrostatic chuck plate 2, and the wafer sample 1 and the electrostatic chuck plate 2 do not directly touch. Moreover, the post 4 is directly attached to the sample stage 16 through the through hole 5 so as not to directly contact the electrostatic chuck plate 2. In the conventional method of providing a step between a concave portion and a convex portion on the insulating film of the electrostatic chuck plate or a method of forming a concave portion on the suction surface to reduce the contact area, a part of the suction portion of the electrostatic chuck plate is directly Although it was in contact with the sample, adhesion of fine particles at this part was unavoidable,
In the system of the present invention, the sample is in contact with a non-adsorbing post, and such is essentially unlikely. on the other hand,
In the conventional method, it was also important to minimize the decrease in the suction force. On the other hand, in the method of the present invention, the post itself did not have the suction force, and the electrostatic chuck plate and the sample were not attached. There is a vacuum gap between them and there is a decrease in the attraction force. Fortunately, however, the performance of the electrostatic chuck device has been greatly improved in recent years, and experiments have shown that a sufficient suction force can be obtained even with the method of the present invention.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments. For example, the material of the post may be fluororesin, or any other material that does not easily contaminate the wafer sample. In addition, eight posts are provided at equal intervals on the same circumference, but the number may be three or more, and of course, the position may be appropriately determined. In short, any arrangement may be used as long as the sample can be held well without warping.

[0010]

As described above, in the present invention, the post penetrating the electrostatic chuck plate is provided,
A slight gap was created to prevent direct contact between the electrostatic chuck plate and the sample. The posts were made of polyimide or fluororesin. As a result, it is possible to prevent fine particles such as dust adhering to the electrostatic chuck plate from being transferred to the sample.

[Brief description of the drawings]

FIG. 1 is a plan view and a sectional view showing an example of a conventional electrostatic chuck device.

FIG. 2 is a diagram showing a basic example of a scanning electron microscope equipped with an electrostatic chuck device.

FIG. 3 is a plan view and a cross-sectional view illustrating an example of an embodiment of the electrostatic chuck device according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Wafer sample, 2 ... Electrostatic chuck plate, 3 ... Holder, 4 ... Post, 5 ... Through hole, 6 ... Void, 10 ... Electron microscope column, 11 ... Electron gun, 12 ... Focusing lens, 13 ... Objective Lens 14 Scan coil 15 Sample chamber 16 Sample stage 17 Detector

Claims (3)

[Claims] 1. An electrostatic chuck device for a sample stage for mounting a flat sample such as a wafer, wherein an electrostatic chuck plate having a plurality of through holes and a plurality of posts penetrating through the through holes are provided on the sample stage. Attachment, the post is made to slightly protrude from the surface of the electrostatic chuck plate to create a gap between the electrostatic chuck plate and the plate sample, and the mounting surface of the plate sample is An electrostatic chuck device characterized in that it does not directly touch the surface of the chuck plate. 2. The electrostatic chuck device according to claim 1, wherein a material of the post is polyimide or fluororesin. 3. The electrostatic chuck device according to claim 1, wherein the gap is 100 μm or less.