JPH07180053A - Wafer holder - Google Patents

Abstract

PURPOSE:To prevent the electrification on a wafer by irradiation with ions by freely vertically movably disposing electrically conducting pins in contact with the rear surface of this wafer. CONSTITUTION:This wafer holder is composed of a base 4 for supporting the wafer 2, a rubber-like elastic material 6 disposed on the surface of the wafer 2 supporting region of this base and an annular clamper 8 for pressing the circumferential edge of the wafer 2 toward a base 4. This rubber-like elastic material 6 is provided with plural through holes 6a. The pins 22 of which the front ends project to the upper surface of the rubber-like elastic material 6 through the through holes 6a at the time of rising are freely vertically movably disposed in the lower part of the respective through holes 6a of the rubber-like elastic material 6 in the base 4. Further, springs 24 which elastically push up the respective pins 22 and electrically conduct the pins 22 to the base 4 are, fitted. All these pins 22 and springs 24 are formed of electrical conductors.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in an apparatus for irradiating a wafer with an ion beam for processing, such as an ion implantation apparatus, an ion beam etching apparatus, and a thin film forming apparatus which uses ion beam irradiation together. The present invention relates to a wafer holding device that holds a wafer to be processed, and more specifically, to improvement of a means for preventing charging (charge-up) of a wafer due to ion beam irradiation.

[0002]

2. Description of the Related Art A conventional example of this type of wafer holding device is shown in FIGS.

The wafer holding device is provided in a vacuum container (not shown), and has a base 4 for supporting the wafer 2 and a rubber-like elastic body 6 attached to the surface of the wafer supporting region of the base 4. And an annular clamper 8 for pressing the peripheral edge of the wafer 2 toward the base 4. The base 4 and the clamper 8 are made of aluminum, for example. The rubber-like elastic body 6 is made of, for example, silicone rubber.

A coolant passage (not shown) is formed in the base 4, and a coolant such as cooling water for cooling the wafer 2 is flown therein.

A plurality of (in this example, two as shown in FIG. 5) clamper shafts 10 penetrate vertically through the base 4, and the clampers 8 are attached to their tip ends. The lower end of each clamper shaft 10 has a connecting plate 16
Is attached to.

A plurality of guide shafts 12 (in this example, three guide shafts 12 as shown in FIG. 5) are attached to the lower surface of the base 4, and these guide shafts 12 pass through a connecting plate 16 so as to be vertically movable. Around each guide shaft 12, a spring (compression coil spring) 14 that elastically pushes down the connecting plate 16 and the object attached thereto under the base 4 is provided.

Further, this embodiment is used for an apparatus of a type in which the wafer 2 is carried in and out of the base 4 by a transfer arm, and therefore, the upper surface of the connecting plate 16 is
Wafer 2 that can penetrate base 4 vertically
Multiple edges (in this example, as shown in FIG.
A wafer receiver 18 is attached. The tip of each wafer receiver 18 is located below the clamper 8 by a predetermined dimension.

When the connecting plate 16 is pushed up by an unillustrated air cylinder or the like as shown by an arrow A, the clamper 8 and the wafer receiver 18 are pushed up as shown by an arrow B, and as shown by a two-dot chain line in FIG. The wafer 2 can be lifted from the base 4 by 18, and the wafer 2 can be loaded and unloaded in this state.

When the pushing up of the connecting plate 16 is stopped, the spring 1
The connecting plate 16 and the clamper 8 and the wafer receiver 18 attached thereto are pushed down by the elastic force of 4, and the wafer 2 can be pressed (held) by the clamper 8 against the rubber-like elastic body 6 on the base 4, In this state, the wafer 2 can be irradiated with the ion beam 20 through the opening of the clamper 8 to perform a process such as ion implantation.

The rubber-like elastic body 6 serves to compensate for the poor heat conduction due to the small contact area between the two when the wafer 2 is directly pressed against the base 4 when viewed microscopically. The heat generated in the wafer 2 due to the irradiation of 20 is transferred to the base 4 through the rubber-like elastic body 6 and is discharged to the outside by the refrigerant flowing in the base 4, whereby the wafer 2 is cooled. It

By the way, an insulating film usually called a resist or an insulating oxide film is formed on the surface of the wafer 2, and when the wafer 2 is irradiated with the ion beam 20,
The positive charges of the irradiation ions are likely to accumulate on the surface of the wafer 2. Moreover, the rubber-like elastic body 6 is an insulator, and as it is, the positive charge of the irradiation ions does not escape on the wafer 2 and the surface of the wafer 2 is positively charged (charge up).

In order to prevent this, one of the three wafer receivers 18 is conventionally formed of a conductive material (more specifically, aluminum) (by the way, the remaining two wafers are coated with resin on aluminum). Wafer support 1 made of this conductive material when supporting the wafer 2.
8 is brought into contact with the back surface of the wafer 2 so that electric charges accumulated on the front surface of the wafer 2 pass through the side surface and the back surface of the wafer 2 on which the resist is not formed, and via the wafer receiver 18 made of a conductive material. The structure is such that the wafer 2 is allowed to escape from the back surface to the base 4 or the like to prevent charging on the wafer 2.

[0013]

However, in the above wafer holding device, when the wafer 2 is being lifted by the wafer receiver 18 as shown by the two-dot chain line in FIG. 4, the wafer holder 18 made of the conductive material is used. Although the charge can be released from the back surface of the wafer 2, the wafer 2 is clamped by the clamper 8 and the ion beam 20
As shown by the solid line in FIG. 4, since the wafer receiver 18 is lowered and is not in contact with the wafer 2, a conductive object is not in contact with the wafer 2. There is no path for the positive charges to flow out from the wafer 2 due to the above, and the positive charges are accumulated on the wafer 2, which in turn causes a discharge due to dielectric breakdown with the clamper 8 that holds the peripheral edge of the wafer 2. .

By the way, even if the peripheral edge of the wafer 2 is clamped by the clamper 8, since the resist of the insulating material or the insulating oxide film is formed on the surface of the wafer 2 as described above, the clamper 8 is used as the resist. Only in contact with each other, and in such a state, it is almost impossible to expect the action of letting the charges on the wafer 2 escape to the base 4 through the clamper 8.

When a discharge is generated between the wafer 2 and the clamper 8 as described above, the resist that is normally formed on the surface of the wafer 2 is peeled off by the discharge, and the peeled product is the surface of the wafer 2. Attached to the wafer 2
However, there is a problem that the processing of the portion where the resist is peeled off or the portion where the peeled resist is attached becomes incomplete, which causes a decrease in device yield and the like.

Therefore, it is a primary object of the present invention to provide a wafer holding device capable of preventing charges from being accumulated on a wafer due to ion beam irradiation.

[0017]

In order to achieve the above object, the wafer holding device of the present invention is provided with a plurality of through holes in the rubber-like elastic body, and each of the rubber-like elastic bodies is in the base. In the lower part of the through hole, which is made of a conductive material, is vertically movable, and when the tip of the pin rises up through the through hole on the rubber-like elastic body, each pin made of a conductive material is pushed up elastically. A spring for electrically connecting each pin to the base is provided, respectively.

[0018]

According to the above construction, when the wafer is clamped on the rubber-like elastic body on the base by the clamper, the pins are elastically pushed up by the springs.
Press contact with the back surface of the wafer. In addition, since each pin is electrically connected to the base by the spring, the path formed by the pin and the spring forms a discharge path for electric charges from the back surface of the wafer to the base.

Therefore, the positive charges on the wafer at the time of ion beam irradiation can be released from the back surface of the wafer to the base through the side surface and the back surface of the wafer where the resist is not formed and through each pin and spring. It is possible to prevent accumulation of electric charges due to ion beam irradiation on the top.

[0020]

1 is a sectional view showing a wafer holding device according to an embodiment of the present invention. FIG. 2 is a plan view showing the wafer holding device of FIG. 1 excluding the wafer. Figure 3
[Fig. 2] is an enlarged cross-sectional view showing the periphery of one pin in Fig. 1. The same or corresponding portions as those of the conventional example shown in FIGS. 4 and 5 are designated by the same reference numerals, and the differences from the conventional example will be mainly described below.

In this embodiment, the rubber elastic body 6 is provided with a plurality of through holes 6a, more specifically, four through holes 6a as shown in FIG. The through holes 6a are provided at equal intervals on the same circumference in this embodiment.

Then, the recesses 4a are provided in the base 4 and in the lower portions of the through holes 6a of the rubber-like elastic body 6, respectively. Inside each recess 4a, a pin 22 made of a conductive material and movable up and down, and each pin 2 made of a conductive material.
A spring (more specifically, a compression coil spring) 24 that elastically pushes up 2 is housed, and a lid 26 covers the spring.

Each pin 22 is so constructed that, when pushed up by a spring 24, its tip projects over the rubber-like elastic body 6 through its through hole 6a by several mm in this example.

More specifically, each pin 22 is made of carbon in this embodiment. Carbon is preferable because it is electrically conductive, generates less particles (dust) when it comes into contact with the wafer 2, and does not damage the wafer 2.

The lid 26 is made of metal, more specifically, the base 4
Like aluminum. Each spring 24 is also made of metal, and each spring 24 also functions to electrically connect each pin 22 to the base 4 via the lid 26.

In this wafer holding device, when the wafer 2 is clamped on the rubber-like elastic body 6 on the base 4 by the clamper 8, the pins 22 are elastically pushed up by the springs 24. Press on the back side. Moreover, each pin 22 has a spring 24 and a lid 2
Since it is electrically connected to the base 4 by 6, the path of each pin 22, the spring 24, and the lid 26 forms a discharge path of electric charges from the back surface of the wafer 2 to the base 4.

Therefore, when the wafer 2 is irradiated with the ion beam 20, the positive charges on the wafer 2 given by the irradiation ions pass through the side surface and the back surface of the wafer 2 where the resist is not formed, and each pin 22 Since it is possible to let the back surface of the wafer 2 escape to the base 4 through the spring 24 and the lid 26, it is possible to prevent the electric charge from being accumulated on the wafer 2 due to the ion beam irradiation.

In this way, since the wafer 2 can be prevented from being charged with the ion beam irradiation, the wafer 2 can be prevented from being charged.
The discharge between the clamper 8 and the clamper 8 can also be prevented, whereby the wafer 2 can be normally subjected to a process such as ion implantation.

Even when the wafer 2 is simply placed on the rubber-like elastic body 6 without being clamped by the clamper 8,
The tip of each pin 22 projects above the rubber-like elastic body 6 and supports the wafer 2, so that each pin 22 contacts the back surface of the wafer 2. Therefore, also at this time, a discharge path of electric charges from the back surface of the wafer 2 to the base 4 is formed.

Further, when the wafer 2 is supported by the wafer receiver 18 (see the chain double-dashed line in FIG. 4), the wafer receiver 18 made of a conductive material therein causes the back surface of the wafer 2 to move to the base 4 or the like. The discharge path for the charges is formed as in the case of the conventional example.

Thus, in this embodiment, the clamper 8
A discharge path of charge is formed from the backside of the wafer 2 to the base 4 whenever the wafer 2 is clamped or not.

The pin 22 and the spring 2 as described above are used.
The number such as 4 is arbitrary as long as it is plural, but it is preferable that the number is large, and therefore, 6 or 8 may be used. Further, it is preferable that the places where they are provided are arranged in the plane of the wafer 2 as evenly as possible.

Although the above description shows an example in which the spring 14 is provided around the guide shaft 12, the spring 14 may be provided around each clamper shaft 10 without providing the guide shaft 12.

[0034]

As described above, according to the present invention, the charge on the wafer can be released from the back surface of the wafer to the base through each pin and the spring, so that the charge due to the ion beam irradiation is not accumulated on the wafer. That is, the wafer can be prevented from being charged. As a result, it is possible to prevent discharge and the like due to charging and perform normal processing on the wafer.

[Brief description of drawings]

FIG. 1 is a sectional view showing a wafer holding device according to an embodiment of the present invention.

FIG. 2 is a plan view showing the wafer holding device of FIG. 1 excluding a wafer.

FIG. 3 is an enlarged cross-sectional view showing the periphery of one pin in FIG.

FIG. 4 is a cross-sectional view showing an example of a conventional wafer holding device.

5 is a plan view showing the wafer holding device of FIG. 4 with a wafer removed.

[Explanation of symbols]

 2 wafer 4 base 6 rubber-like elastic body 6a through hole 8 clamper 22 pin 24 spring 26 lid

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H01L 21/3065 21/68 N

Claims (1)

[Claims] 1. A wafer comprising a base for supporting a wafer, a rubber-like elastic body provided on a surface of a wafer supporting region of the base, and an annular clamper for pressing a peripheral portion of the wafer toward the base. In the holding device, a plurality of through holes are provided in the rubber-like elastic body, and in the base, below the through-holes of the rubber-like elastic body,
A pin made of a conductive material that can move up and down and its tip protrudes through the through hole on the rubber-like elastic body when it rises, and a pin made of a conductive material that elastically pushes up each pin and electrically connects each pin to the base. And a spring for electrically conducting the wafer, respectively.