JPH0454880A - wafer holding device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an apparatus for holding a wafer with high precision in a vacuum.

[Conventional technology]

Conventionally, this type of equipment has an electrostatic adsorption device on the opposite side (wafer front side) of the wafer from the incident surface (wafer front side) of charged particle beams such as electron beams and ion beams. After that, the wafer surface was brought into contact with the reference surface.

[Problem to be solved by the invention]

In the conventional technology described above, the wafer receives force from the back side due to electrostatic adsorption, and from the front side, force is applied from the reference plane for positioning the wafer, so force is applied from both the front and back sides, leaving distortion in the wafer. There was fear.

Alternatively, instead of adopting a front surface reference in which the front surface of the wafer is brought into contact with the reference surface, it is also possible to adopt a back reference in which the back surface of the wafer is brought into contact with the reference surface. cannot be determined accurately.

The present invention has been made in view of these conventional problems, and it is an object of the present invention to provide a wafer holding device that applies force only to the surface of the wafer.

[Means to solve problems]

In order to solve the above problems, the present invention provides a wafer holding device that holds a wafer that is irradiated with a charged particle beam.
A reference surface was provided for the peripheral edge of the wafer surface onto which the charged particle beam was incident, and an adsorption means including an insulating layer formed of a thin film was provided on the reference surface.

[Effect]

A suction means including an insulating layer formed of a thin film is provided on a reference surface processed to be perpendicular to the axis of the charged particle beam with high precision, and the unevenness of the thickness of the thin film is 10% or less. Since the unevenness of the wafer can be easily suppressed, the axial position of at least the peripheral edge of the wafer in contact with this surface can be determined accurately.

Therefore, the entire surface of the wafer is correctly positioned within its flatness. Whether or not the wafer is properly attracted is determined by the magnitude relationship between the wafer weight and the electrostatic force.

It is sufficient that the latter is sufficiently larger than the former.

Assuming that the wafer weight is 50 gr (8'' wafer), the electrostatic force F should be sufficiently larger than 50 gr.

Therefore, it is sufficient to satisfy F≧100gr weight.

If an electrostatic force of 100gr force/cd is obtained, lc
If the area is larger than j, the wafer can be attracted.

Considering a ring-shaped area with a width of 1 cm at the peripheral edge of the 8-inch way, an area of about 6 d is obtained, which is sufficient for adsorption.

〔Example〕

The present invention will be described below based on embodiments shown in the drawings.

FIG. 1 is a partially enlarged cross-sectional view of an embodiment of the present invention (see FIG. 2).
b) - the part indicated by the dotted chain line B circle), and Fig. 2(a), (
b) is a diagram schematically showing the entirety of the above embodiment;
FIG. 2(a) is a plan view, and FIG. 2(b) is a sectional view taken along the line AA' in FIG. 2(a).

The reference block 1 has an upper plate part 1b having a circular opening 1a formed in the center thereof, and a leg IC having a U-shaped cross section (see FIG. 2(a)) that supports the upper plate part 1b. . The opening 1d of the 11th part IC functions as an insertion/removal hole for the wafer 10, and therefore, the distance and depth between the opposing legs 1c are naturally designed to be larger than the outer diameter of the wafer 10. Also,
The diameter of the opening 1a of the upper plate portion 1b is designed to be slightly smaller than the outer diameter of the wafer 10.

A ring-shaped reference surface 2 with a width of several squares is formed on the lower surface of the upper plate portion 1b adjacent to the opening 1a, and this reference surface 2 functions as a mounting reference surface for the peripheral portion of the surface of the wafer 10. . Therefore, this reference plane 2 is processed as a plane perpendicular to the axis of the charged particle beam with high precision.

A vapor deposited titanium film 3 is formed on almost the entire surface of the reference block 1 other than the reference surface 2 to prevent static electricity.

Further, electrodes 4a and 4 are formed on the surface of the reference surface 2 by vacuum evaporation or the like.
The thin metal film forming b is about 1 inch wide and 0.2 mm thick.
It is formed with a length of about m. As shown in FIG. 2(a) when viewed in a plane perpendicular to the axis of the charged particle beam (plan view), the electrodes 4a and 4b are formed so as to divide the periphery into two.

And these electrodes 4a and 4b are connected to conductive wires 5a and 4b, respectively.
5b is connected, and the conducting wires 5a and 5b are led along the inner surface of the reference block 1, and then lead out from the inside of the reference block 1 to the outside via sealing materials 6a and 6b.

The conductive wire 5a15b led out in this way has
+100V and -100V are applied, respectively.

Furthermore, on the surfaces of the electrodes 4a and 4b and the surface of the reference surface 2,
Insulating film 7 of alumina (Aj!tOs) is formed by vacuum evaporation.
is formed with a thickness of about 3 μm.

The base 90 of the electrostatic chuck device 9 for wafer transfer has a substantially circular planar shape, and an electrode 91 and an insulating film 92 made of alumina or the like are formed on its upper surface. 9 has a well-known configuration.

With such a configuration, the electrostatic adsorption device 9
After being carried into the space surrounded by the upper plate part 1b and the leg part 1c,
Wafer 10 approximately centered on the center of opening 1a
is brought into contact with the deposited film 3 on the reference surface 2 as the electrostatic chuck device 9 rises. When the above-mentioned contact is detected due to an increase in the load on the lifting motor of the electrostatic adsorption device 9, this detection signal causes the electrodes 4a, 4b to receive +100V and -1, respectively.
00V is applied, and then the electrode 91 of the electrostatic adsorption device 9
energization is cut off, and the electrostatic adsorption device 9 descends and stops.

Since +100V and -100V are applied to the electrodes 4a and 4b, respectively, the wafer 10 is statically attached to the reference block 1 (91).

At this time, the thickness of the electrodes 4a, 4b and the insulating film 7 is 3.2
The thickness is on the order of μm, and the thickness unevenness is less than 10%, so at least the peripheral edge of the wafer 10 can be accurately positioned. Therefore, the entire surface of the wafer 10 can be correctly positioned within its flatness range.

Then, the charged particle beam is irradiated onto the wafer lO from the direction of arrow C.

According to the above example, (1) the wafer of about 50 gr is suctioned and fixed with a force of about 500 gr, so it can be suctioned and fixed on the top surface of the Si Milani, (2) the structure is simple, and the electrostatic chuck voltage is is +10
It operates at 0■ and can also be used as a power supply for loading and unloading.
(3) The electrodes and insulating layer for electrostatic chucks can be formed by vapor deposition or sputtering, making them easy and reliable. (4)
Since it is based on the surface, there is no axial variation of the charged particle beam on the wafer surface even if there is uneven thickness of the wafer, etc. (5)
The reference block is not made of expensive ceramics such as SiC, but is made of an inexpensive material such as alumina, so that it is inexpensive.

〔Effect of the invention〕

As described above, according to the present invention, since force is applied only to the surface of the wafer, no distortion remains on the wafer, and accurate positioning is possible.

[Brief explanation of the drawing]

FIG. 1 is a partially enlarged cross-sectional view of an embodiment of the present invention (see FIG. 2).
b) - part of the circle enclosed by the dotted chain line B), Fig. 2(a),
2(b) is a diagram schematically showing the whole of the above-mentioned embodiment, FIG. 2(a) is a plan view, and FIG. 2(b) is a diagram showing FIG.
FIG. [Explanation of symbols of main parts] 2...Reference surface, 4a, 4b...Electrode, 7...Alumina film.

Claims (1)

[Scope of Claims] A wafer holding device that holds a wafer to which a charged particle beam is irradiated, comprising a reference surface relative to the peripheral edge of the wafer surface on which the charged particle beam is incident, and a thin film formed on the reference surface. A wafer holding device comprising a suction means including an insulating layer.