JPH04350952A - Wafer positioner - Google Patents

Abstract

PURPOSE:To accurately measure and correct the orientation of a wafer in a vacuum atmosphere. CONSTITUTION:The top end of an elevatable and rotatable elevation shaft 14 is fitted with a holder base 2. The holder base 2 consists of a substrate made of dielectric which is inlaid with laterally separated electrode layers in a vicinity of the surface. The elevation shaft 14 has an insert of a three- phase alterating wiring 3 where the core of each phase of the wiring 3 is connected to the terminal of an electrode layer in a hollow region. Any of electrode layers keeps impressed with voltage and can attain strong holding; therefore, the out-of-position or the direction of a wafer W can be measured and corrected by spinning it in a vacuum atmosphere.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wafer positioning apparatus for measuring or even correcting the orientation and position of a wafer in a vacuum atmosphere.

0002

2. Description of the Related Art For example, when processing or inspecting a semiconductor wafer, since the wafer has crystal orientation, it may be necessary to position the wafer in terms of its orientation (orientation flat direction). Furthermore, it is necessary to accurately align the wafer in order to securely fix the wafer to the processing equipment.

For this reason, in the past, for example, in an ion implantation device, the wafer is placed on a rotatable holding table of a positioning device installed in the atmosphere, and then the wafer is moved using, for example, vacuum suction. After suctioning and fixing the wafer to the holding table, the holding table is rotated to measure the orientation and center position of the wafer, and to correct the deviation.Then, the wafer on the holding table is transferred to the vacuum processing chamber through the load lock chamber. It was designed to be transported to a loading section.

0004

[Problem to be Solved by the Invention] In order to improve the efficiency of the system, it may be considered advantageous to measure the orientation of the wafer in a vacuum atmosphere instead of in the atmosphere. .

For example, if the above-mentioned positioning device is brought into the load lock chamber, the number of wafer changes can be reduced, thereby preventing the generation of particles, and the throughput can be improved by performing measurement during evacuation. is obtained. Another advantage is that dummy wafers that are used repeatedly can be stored in the vacuum processing chamber without having to be transported back and forth to the atmosphere.

However, it is actually very difficult to bring the positioning device into a vacuum atmosphere. This is because vacuum suction cannot be used to hold a wafer on a holding table in a vacuum atmosphere, so a method to prevent slipping may be considered, for example, by using rubber with a large friction coefficient, but with this method, Rubber dirt adheres to the wafer, chemical contamination is a problem, and if the rotational speed or acceleration is increased, the wafer may slip and become misaligned, and in some cases it may fall off and be damaged, and vibrations may cause problems. A similar problem occurs when the size is large.

The present invention was made under these circumstances, and its purpose is to reliably measure and correct the orientation and positional deviation of a wafer during load lock or in a vacuum atmosphere. An object of the present invention is to provide a device for positioning a wafer.

[0008]

[Means for Solving the Problems] The invention as claimed in claim 1 provides a wafer positioning device that places a wafer on a rotatable holding table and rotates this holding table to measure the orientation and positional deviation of the wafer. , an adsorption layer provided on the holding table and made of a dielectric material for adsorbing a wafer, a plurality of electrode parts arranged laterally apart from each other, and a power supply part for applying voltage to the electrode parts. , and a control section that controls application and stopping of voltage between the electrode sections.

[0009] In the invention according to claim 2, at least three of the electrode parts are provided, and the power supply part applies a voltage between the electrode parts so that a voltage of zero or more is always applied to one of the electrode parts. It is characterized by

[0010] According to the third aspect of the invention, the holding table is placed in a vacuum atmosphere including a load lock chamber, and the rotating shaft portion for rotating the holding table is made airtight from the vacuum atmosphere and is provided with a vacuum atmosphere. It is characterized in that a region communicating with the outside of the atmosphere is formed, and the electrode portion and a voltage application line from the outside are connected in this region.

[0011]

[Operation] When a DC or AC voltage is applied between the electrode parts, an electrostatic force is generated between the electrode parts and the wafer, which is a conductor, and the electrode parts are attracted to each other. For example, if three electrode sections are provided and a three-phase AC voltage is applied between them, electrostatic force always acts to firmly hold the wafer on the holding table. Furthermore, when the voltage application is stopped, it takes some time to release the retention depending on the degree of dielectric polarization when the drive is driven by a DC voltage, but when the voltage is driven by an AC voltage, the dielectric polarization of the adsorption layer is slight. Therefore, the wafer is quickly released from the holding section.

0012

[Embodiment] Fig. 1 is a diagram showing an embodiment in which the positioning device of the present invention is incorporated into a load lock device. A holding stand 2 is arranged.

First, to briefly describe the parts related to the rotation, lifting and lowering functions, and the parts related to position measurement of the holding table 2, the outer casing part 11 constituting the load lock chamber 1 has a cylindrical part 11a projecting downward. A cylinder portion 13 is inserted into this via a bearing portion 12 with a magnetic seal so as to be rotatable around a vertical axis. Furthermore, an elevating shaft portion 14 is inserted into the cylinder portion 13 so as to be able to rise and fall freely along the central axis of the cylinder portion 13, and a holding base 2 is attached to the top end of the elevating shaft portion 14. It is provided. In addition, in this example, the cylinder part 13 and the lifting shaft part 14
constitutes a rotating shaft portion for rotating the holding table 2.

The lifting shaft portion 14 is hollow inside and forms a communication path communicating with the outside (atmospheric pressure atmosphere), into which a three-phase AC wiring 3, which will be described later, is inserted. .

[0015] At the upper end of the communication path, the core wire portion of the wiring 3 and a terminal on the holding stand 2 side, which will be described later, are connected. The top end of the elevating shaft portion 14 and the lower surface of the holding base 2 are detachably attached to each other with screws or the like, and
For example, it is airtightly sealed by a sealing member such as an O-ring, and between the lifting shaft part 14 and the cylinder part 13, there is a space surrounding the lifting shaft part 14 in order to maintain airtightness in the load lock chamber 1. A bellows 15 is provided as shown in FIG.

[0016] An air cylinder mechanism 13a is provided at the lower part of the cylinder section 13, by which the elevating shaft section 14 is raised and lowered relative to the cylinder section 14.

On the other hand, there is a window 4 on the side wall of the load lock chamber 1.
1 is formed, and on the outside thereof, an optical unit 4 for optically detecting the peripheral edge of the wafer and measuring the orientation flat direction and center position of the wafer.
An optical path is formed between this optical unit 4 and mirrors 42 and 43 arranged above and below the peripheral edge of the wafer, as shown by the arrow.

Next, regarding the holding table 2, as shown in FIG.
As shown in FIG. 3, the holding table 2 is constituted by a base part 20 made of ceramic, which is a dielectric material, for example, and is located at a distance of, for example, 200 μm from the surface at the center of the base part 20.
Electrode layers 5A, 5B, and 5C, each forming a fan-shaped electrode part opened at 120 degrees, are buried at a depth of about A wafer electrostatic adsorption mechanism is configured. Note that in FIG. 3, the cross-sectional structure of the holding table 2 is schematically shown.

Now, to explain the circuit configuration regarding the electrode layers 5A to 5C, each electrode layer 5A to 5C is provided with terminals 51A to 51C, respectively, as shown in FIG. , are connected to the U, V, and W phases of a three-phase AC power supply section 7 via a three-phase switch section 6, respectively. The three-phase switch unit 6 is controlled on and off by a controller 8 that controls the entire ion implantation process, for example, when a wafer is placed on the holding table 2 from a transfer arm (not shown), and when the wafer is lifted by the transfer arm. They are turned on and off respectively when they are used.

As shown in FIG. 3, the terminals 51A to 51C are exposed to the hollow region at the upper end of the lifting shaft portion 14 on the back side of the holding table 2 through the ceramic portions from the electrode layers 5A to 5C, respectively. This exposed portion is connected to the core wire portion of each phase of the three-phase AC wiring 3, which is a voltage application line inserted into the lifting shaft portion 14. In this example, the base portion 20 (dielectric) in the upper portion of the electrode layers 5A to 5C corresponds to the adsorption layer 21.

Next, the operation of the above embodiment will be described. First, when a gate valve (not shown) is opened and the wafer W is carried by the transfer arm to the position shown by the chain line in the load lock chamber 1 shown in FIG. After the table 2 contacts the lower surface of the wafer W (the position indicated by the chain line), it further rises to lift the wafer W and receive it from the transfer arm, and then, after the transfer arm retreats, it descends to the position indicated by the solid line.

When the holding table 2 receives the wafer W, the controller 8 turns on the three-phase switch 6 and connects each phase (U, V, W phase) of the three-phase AC power source 7 to the terminals 51A to 51.
C, a three-phase AC interphase voltage is applied between each electrode layer 5A to 5C, and in response to this interphase voltage, an electrostatic force acts on the wafer, which is a conductor, through the adsorption layer 21, and the wafer is electrostatically attracted to the adsorption layer 21. Here, since a three-phase AC voltage is applied to the electrode layers 5A to 5C,
A voltage is always applied to one of the electrode layers 5A to 5C, so that an electrostatic force always acts on the wafer, and the wafer is firmly held on the holder.

Thereafter, the elevating shaft section 14 is lowered and rotated together with the cylinder section 13 by a drive mechanism (not shown), thereby causing the wafer to rotate, for example, one rotation or more, and the peripheral edge of the wafer is monitored by the optical unit 4. Based on the monitoring results, a data processing unit (not shown) detects the orientation of the wafer (the orientation of the orientation flat) and the center position. Next, the elevating shaft section 14 rises, and the wafer is transferred to the transfer arm on the vacuum processing chamber side in an operation opposite to the above-mentioned wafer receiving operation. Release the electric adsorption. In this case, the voltage applied to the dielectric is an alternating current voltage, so the direction of the electric field changes before the dielectric polarization progresses, and the dielectric polarization is substantially small, so when the voltage application is stopped, the electrostatic force will be canceled instantly. Thereafter, the wafer is transported by a transport arm into a vacuum processing chamber for performing ion implantation, for example, so as to correct the measured positional deviation.

In the above embodiment, the electrode portion 5A
The connection part between the terminals 51A to 51C of ~5C and the three-phase wiring 3 is located on the back side of the holding table 2, outside the vacuum atmosphere,
Moreover, since the holding table 2 is detachably attached to the lifting shaft 14, there is no risk of vacuum discharge occurring at the connection part, and there are advantages in that maintenance such as replacement of the holding table 2 is easy. be.

[0025] Here, the positioning device of the present invention is not limited to being incorporated into a load lock device, but can also be placed inside a vacuum processing chamber, and the positioning device of the present invention can also be placed in a vacuum processing chamber with its electrical connection portion located in a vacuum atmosphere. It is also possible to stop applying voltage to the electrodes of the electrostatic adsorption mechanism within a pressure range that causes vacuum discharge.

Furthermore, in the present invention, a DC voltage may be applied between the electrodes, and in this case, it may take some time to release the wafer from holding the wafer depending on the degree of dielectric polarization after the voltage application is stopped. It can be adapted to systems with sufficient margin.

Furthermore, when applying an AC voltage between the electrodes, 1
Single-phase alternating current may be applied between a set of electrodes, or
Alternatively, single-phase AC voltages whose phases are shifted from each other may be applied between each set of two electrode parts.

Furthermore, the present invention employs a method in which a flexible dielectric film containing a built-in electrode layer is removably attached to a flexible base to form a holding table that can absorb warpage of the wafer. You can also.

Regarding the positional relationship between the adsorption layer and the electrode part, it is easy to manufacture by burying the electrode part in the adsorption layer, but if the structure is such that the wafer can be adsorbed to the holding table by electrostatic force, , but not limited to.

The positioning apparatus of the present invention can also be applied to an apparatus having a function of correcting the orientation and positional deviation of the wafer, and may also be used at atmospheric pressure.

[0031]

According to the invention as claimed in claim 1, since the wafer is held using electrostatic force, it is possible to firmly hold the wafer in a vacuum atmosphere, and therefore the wafer remains in position even when rotated at high speed. Since no misalignment occurs, it is possible to measure and correct wafer orientation and misalignment in vacuum processing chambers and load lock chambers reliably and quickly, and there is no contamination on the wafers, unlike when using rubber. There is no risk of adhesion, etc. Therefore, in the present invention, it is possible to bring a wafer positioning device into a vacuum atmosphere, and therefore, for example, a system can be realized in which the number of handling operations can be reduced by combining with a load lock device as in the embodiment.
Very effective.

According to the invention of claim 2, since a voltage is always applied between at least two electrode parts, such as by applying a three-phase AC voltage, when only a single-phase AC voltage is used, In comparison (in this case, zero voltage exists), the wafer can be held firmly.

According to the third aspect of the invention, a region communicating with the outside of the vacuum atmosphere is formed in the rotating shaft of the holding table, and the terminal of the electrode part and the voltage application line are connected in this region. Therefore, there is no risk of vacuum discharge occurring, and maintenance is easy because, for example, the holding base can be removed and the terminals can be disconnected from the voltage application line.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the entire embodiment of the present invention.

FIG. 2 is an explanatory diagram showing electrical connections of essential parts of the embodiment of the present invention.

FIG. 3 is a sectional view showing the structure of a main part of an embodiment of the present invention.

[Explanation of symbols]

1 Load lock room 13 Cylinder part 14 Lifting shaft part 2 Holding stand 21 Adsorption layer 3 Three-phase wiring 5A-5C Electrode part 51A~51C Terminal 7 Three-phase AC power supply

Claims (3)

[Claims] 1. A wafer positioning device in which a wafer is placed on a rotatable holding table and the holding table is rotated to measure the orientation and positional deviation of the wafer, the device being provided on the holding table to hold the wafer still. A voltage is applied between an adsorption layer made of a dielectric material for electrostatic adsorption, a plurality of electrode parts arranged at positions below the surface of the adsorption layer and spaced apart from each other in the surface direction of the adsorption layer, and the electrode parts. A wafer positioning apparatus comprising: a power supply section that applies a voltage; and a control section that controls application and stopping of voltage between the electrode sections. 2. At least three of the electrode sections are provided, and the power supply section applies a voltage between the electrode sections so that a voltage of zero or more is always applied to one of the electrode sections. equipment for positioning wafers. 3. The holding table is placed in a vacuum atmosphere, and a region is formed in a rotating shaft portion for rotating the holding table that is airtight against the vacuum atmosphere and communicates with the outside of the vacuum atmosphere. 2. The wafer positioning apparatus according to claim 1, wherein the electrode portion and an external voltage application line are connected in this region.