JP3121893B2 - Electrostatic chuck - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic chuck used for fixing, straightening or transporting a silicon wafer in a semiconductor manufacturing apparatus or the like.

[0002]

2. Description of the Related Art Conventionally, electrostatic chucks have been used to adsorb and fix a silicon wafer in a semiconductor manufacturing process and to adsorb and fix other plate-like bodies. As shown in FIG. 5, this electrostatic chuck has a structure in which one internal electrode 12 is buried in a dielectric board 11 and a DC voltage is applied from a power supply 16 between the internal electrode 12 and the object 30 to be attracted. Body board 11
A dielectric pole is generated on the surface of the substrate, and the object 30 is attracted and fixed to the attracting surface 11a by this electrostatic force (single-pole type). Alternatively, as shown in FIG. , 12 are buried and these internal electrodes 1
A DC voltage is applied from a power supply 16 between the terminals 2 and 12 to generate dielectric polarization on the surface of the dielectric board 11, and the electrostatic force causes the object 30 to be attracted and fixed to the attracting surface 11a (bipolar type). There are different types and they are used properly according to the application.

For example, in a semiconductor manufacturing process, EB
(Electron beam) Processing of a silicon wafer surface is performed by a drawing apparatus. This EB lithography apparatus is a semiconductor manufacturing processing machine that focuses an electron beam emitted from a cathode on a surface of a silicon wafer with an electromagnetic lens and physically processes the surface. In the processing process using this EB lithography apparatus, an electrostatic chuck was used to adsorb and fix the silicon wafer. In this case, however, due to the structure of the apparatus, an electric current was applied to the object (silicon wafer) in the vacuum processing chamber. Since it is difficult to form a voltage application terminal, a bipolar electrostatic chuck has been used.

[0004]

However, when the electrostatic chuck is attracted and fixed by a bipolar electrostatic chuck, an uneven charge is generated on the processing surface of the silicon wafer which is the object to be sucked, and the electron beam of the EB lithography apparatus causes the uneven electron charge. As a result, the positioning of the electron beam cannot be performed accurately, and as a result, the processing of the silicon wafer cannot be performed with high accuracy.

[0005]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a dielectric board having a plurality of internal electrodes and having an adsorbing surface for adsorbing and fixing an object to be adsorbed, and an electric current flowing between the plurality of internal electrodes. And a power supply for performing the operation between the internal electrodes from the power supply and electrostatically attracting and fixing the object to be attracted to the attracting surface by electrostatic force. When a contact electrode having a detachment mechanism for lifting the object to be adsorbed from the adsorption surface is provided when the object is in contact with the adsorbed object and conducts, and when the electrostatic force is not generated, between the internal electrodes, and the contact electrode A switch for switching application of a voltage between the internal electrodes is provided.

[0006]

With the electrostatic chuck of the present invention, first, a voltage is applied between a plurality of internal electrodes to perform bipolar adsorption, and then when the object contacts the adsorption surface, the object is passed through the contact electrode. If a voltage is applied between the electrode and the internal electrode to perform the monopolar adsorption, the EB lithography apparatus performs monopolar adsorption, so that the charge on the surface of the silicon wafer, which is the object to be adsorbed, is reduced. Thus, the electron beam can be accurately positioned. Further, since it is not necessary to previously form a voltage application terminal on the silicon wafer itself, the processing steps can be simplified.

[0007]

Embodiments of the present invention will be described below.

As shown in FIG. 1 for the overall shape and FIG. 2 for its schematic cross section, the electrostatic chuck 10 of the present invention comprises a ring-shaped internal electrode 12 and a central internal electrode 13 in a dielectric disk 11. The surface is a smooth adsorption surface 11a for adsorbing an object to be adsorbed such as a silicon wafer. Further, the through-hole 1 formed in the dielectric board 11
1b, a contact electrode 14 is provided.
Is urged upward by a spring 15 or the like,
a is in a state protruding from the suction surface 11a. Further, the electrostatic chuck 10 is fixed to the base plate 20 by bolts 21 or the like.

The material of the dielectric board 11 is as follows.
Various materials such as resin, glass, and ceramics can be used, but ceramics are particularly preferable in terms of heat resistance, corrosion resistance, and the like. As the ceramics, generally used alumina (Al ₂ O ₃ ) ceramics may be used, but for example, barium titanate (Ba)
Adsorption power can be increased by using a ceramic having a high dielectric constant containing TiO ₃ ) or calcium titanate (CaTiO ₃ ) as a main component. Further, when ceramics containing silicon nitride (Si ₃ N ₄ ) or aluminum nitride (AlN) as a main component are used, the heat radiation can be increased without affecting the wafer. In this case, the internal electrodes 12 and 13 may be formed of a metal such as silver (Ag), platinum (Pt), or palladium (Pd) and buried in the dielectric board 11.

Further, as shown in FIG. 2, the electrostatic chuck of the present invention has the internal electrodes 12 and 13 and the contact electrodes 14.
A power supply 16 for applying a voltage to the power supply and a switch 17 for switching the power supply are provided. When the switch 17 is connected to the contact 17a side, a DC voltage is applied between the two internal electrodes 12 and 13 from the power supply 16 to perform the bipolar adsorption. On the other hand, switch 17 is set to contact 17b
Side, the contact electrode 14 and the ring-shaped internal electrode 12
DC voltage can be applied during the
1a, the contact electrode 14 is placed.
, A voltage can be applied between the object 30 and the internal electrode 12, and monopolar adsorption can be performed. At this time, since the internal electrodes 12 are ring-shaped, stable adsorption can be performed.

When such an electrostatic chuck 10 of the present invention is used, first, the switch 17 is connected to the contact 17a side, and the object 30 is fixed to the suction surface 11a by bipolar suction. At this time, the to-be-adsorbed object 30 is in contact with the tip 14a of the contact electrode 14, and is adsorbed and fixed to the adsorbing surface 11a while the contact electrode 14 is pressed downward. Next, if the switch 17 is switched to the contact 17b side in this state, the single-pole type adsorption is performed. With this configuration, it is not necessary to form a voltage application terminal on the object 30 in advance,
Monopolar adsorption can be easily performed. Therefore, E
Even when processing is performed by the B drawing apparatus, there is no bias in the charge on the surface of the object 30, so that the electron beam can be accurately positioned. In addition, since the monopolar type generally provides a stronger adsorption force, the fixing force can be increased at a low voltage.

Further, when removing the object 30 to be adsorbed, the switch 17 may be separated from both the contacts 17a and 17b to interrupt the applied voltage.
Therefore, the object 30 is easily separated from the suction surface 11a by the separation mechanism of the contact electrode 14.

In the electrostatic chuck of the present invention, the switching from the bipolar type to the monopolar type is performed, for example, by using the object 3
It is only necessary to detect a drop of the contact electrode 14 due to the pressing of 0 and switch the switch 17 when the contact electrode 14 is lowered so as to be of a single-pole type.

In the above-described embodiment, the contact electrode 14 has a structure in which the rod-shaped electrode moves up and down. However, when the contact electrode 14 adsorbs the object 30, the contact electrode 14 is reliably connected to the object 30. In addition, it is sufficient that the flatness of the suction surface 11a is not impaired, and the position and the shape of the contact electrode 14 can be various structures. For example, as shown in FIG. 3 in another embodiment, the contact electrode 14 attached to the dielectric board 11 protrudes above the suction surface 11a and is elastically deformed downward when the object 30 is sucked. Has become.

Further, in the embodiment shown in FIG. 2, the shape of the internal electrodes 12 and 13 is a central portion and a ring shape surrounding the central portion. And so on. Further, three or more internal electrodes may be provided.

Here, an electrostatic chuck having the structure shown in FIGS. The dielectric disk 11 is formed of ceramics having a dielectric constant of ε _r 100 containing calcium titanate (CaTiO ₃ ) as a main component, and has a suction surface 11a having a diameter of 4 inches and two palladium (Pd) insides. The internal electrodes 12 and 13 were embedded. Further dielectric board 1
1, a through hole 11b is formed, and a spring 1 is formed in the through hole 11b.
5 was provided with a contact electrode 14 urged upward by 5. Using this electrostatic chuck 10, the relationship between the applied voltage and the attraction force was examined for a case where a bipolar voltage was applied and a case where a monopolar voltage was applied. As shown in FIG. 100kg required for normal adsorption
/ Cm ² or more. In addition, since a monopolar type voltage application can obtain a higher adsorption force, for example, by applying a voltage of 500 V, if the adsorption is first performed by the bipolar type and then switched to the monopolar type, a sufficient adsorption force can be obtained. it can. Furthermore, when the silicon wafer was fixed using this electrostatic chuck 10 and processing was performed by an EB lithography apparatus, it was confirmed that the electron beam could be accurately positioned and processing could be performed with high precision.

In the above embodiment, only the one using a silicon wafer as the object 30 is shown, but it goes without saying that the electrostatic chuck 10 of the present invention can be applied to various other uses. .

[0018]

As described above, according to the present invention, a dielectric disk having a plurality of internal electrodes and having an adsorbing surface for adsorbing and fixing an object to be adsorbed is provided. A power supply for supplying power to the internal electrodes, and an electrostatic chuck for attracting and fixing the object to be attracted to the suction surface by electrostatic force by applying a current between the internal electrodes from the power source. A contact electrode having a detachment mechanism for lifting the adsorbed object from the adsorbing surface when the adsorbed object is in contact with the adsorbed object and is not generating the electrostatic force, between the internal electrodes, and By providing a switch that switches the application of voltage between the contact electrode and the internal electrode, a bipolar voltage application is performed at the initial stage of adsorption, and a monopolar voltage application is performed after the adsorption. mark It is not necessary to form a terminal,
A single-pole type adsorption and fixation can be performed easily,
When no voltage is applied, the object to be adsorbed can be easily separated from the adsorption surface. Therefore, it is possible to eliminate the bias of the electric charge on the surface of the silicon wafer during the processing by the EB drawing apparatus, and to perform the processing with high accuracy, and to obtain the high attraction force with a low voltage. An electrostatic chuck can be provided.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an electrostatic chuck according to the present invention.

FIG. 2 is a schematic sectional view taken along line XX in FIG.

FIG. 3 is a schematic sectional view showing another embodiment of the present invention.

FIG. 4 is a graph showing a relationship between an applied voltage and a chucking force in a bipolar type and a monopolar type in the electrostatic chuck of the present invention.

FIG. 5 is a schematic sectional view showing a conventional single-pole type electrostatic chuck.

FIG. 6 is a schematic sectional view showing a conventional bipolar electrostatic chuck.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Electrostatic chuck 11 ... Dielectric board 11a ... Attraction | suction surface 11b ... Through-hole 12 ... Internal electrode 13 ... Internal electrode 14 ... Contact electrode 15 ... Spring 16 ...・ Power supply 17 ・ ・ ・ Switch 20 ・ ・ ・ Base 30 ・ ・ ・ Adsorbed object

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-186863 (JP, A) JP-A-62-125642 (JP, A) JP-A-2-196442 (JP, A) JP-A-58-1983 114437 (JP, A) JP-A-62-287950 (JP, A) JP-A-2-76658 (JP, A) JP-A-63-115223 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) B23Q 3/15 H01L 21/68

Claims (1)

(57) [Claims] 1. A Rutotomoni comprising a plurality of internal electrodes, the adsorption
A dielectric disk having an adsorption surface for adsorbing and fixing an object;
A power supply for supplying current between the internal electrodes.
Then, electricity is supplied between the internal electrodes from the power source to reduce static electricity.
The object is adsorbed and fixed to the adsorption surface by electric force.
In the electrostatic chuck, the dielectric disc is brought into contact with and adheres to the object to be attracted, and generates the electrostatic force.
A contact electrode having a detachment mechanism for lifting the object from the adsorption surface when not in use , and a switch for switching the application of voltage between the internal electrodes and between the contact electrode and the internal electrode. An electrostatic chuck characterized by being provided .