JP2008205407A - Method for discharging remaining static electricity of electrostatic chuck, and electrostic chuck - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To definitely discharge static electricity left in a wafer before lifting up the wafer from a block of an electrostatic chuck with a lift pin. <P>SOLUTION: The system is provided with the block 2 that attracts and holds a substrate 1 with static electricity, a lift pin 3 that lifts the substrate 1 after attraction and holding are released from a lower side and removes the same from the block, and a remaining static electricity discharging mechanism (ring 4 and pin 5) that continuously floats one portion of the substrate 1 along a circle with the center of a substrate surface as a center from the block 2. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for removing residual static electricity from an electrostatic chuck, and an electrostatic chuck capable of performing these methods.

  Conventionally, an electrostatic chuck has been used as an apparatus for holding a wafer in a reactive ion etching apparatus or the like used in a semiconductor device manufacturing process. The electrostatic chuck includes a table that holds the substrate (wafer) by static electricity, and lift pins that lift the substrate from the lower side and release it from the table after the suction holding is released. Usually, static electricity present on the back surface of the substrate is removed by the grounded lift pins coming into contact with the substrate. Alternatively, a method of removing static electricity by applying a reverse potential is also employed.

  However, the amount of static electricity is not uniform in the surface due to the degree of contamination on the back surface of the wafer, the surface condition, etc., and the lift pins are usually placed at the center of the wafer instead of the peripheral edge. Therefore, even if the static electricity removing process as described above is performed, static electricity often remains in a part of the surface (especially the peripheral edge). When a wafer with static electricity remaining is lifted from below with lift pins, the wafer may jump if static electricity remains in a wide range. Also, if it remains on a part of the peripheral part, the part does not move away from the table, so the arm that transports the wafer contacts the wafer, or the arm cannot properly hold the wafer and is positioned on the wafer. There is a risk of causing a shift.

In Patent Document 1 below, in order to solve such a problem, it is described that a plurality of detachment pins are provided at positions on the wafer peripheral portion outside the lift pins.
In the wafer detachment method described in this document, for example, four detachment pins are provided at equal intervals on the same circumference, and the two detachment pins facing in the radial direction of the wafer are raised by about 0.1 mm. After that, the other two release pins are raised by about 0.1 mm, and the first two release pins are further raised by 0.1 mm. The dimension within the allowable deformation range). Thus, it is described that the wafer can be reliably removed from the table even when the electric charge remains.

In addition, it is described that by providing a pressure sensor that contacts the wafer and detects the contact pressure on the detachment pin, it is possible to confirm whether the wafer is detached from the table from the pressure value detected by the sensor. Has been.
Japanese Patent Laid-Open No. 11-243137

  An object of the present invention is to make it possible to reliably remove static electricity remaining on a wafer before the wafer is lifted from a stage of an electrostatic chuck by lift pins by a method different from the method of Patent Document 1.

  Invention 1 for solving the above-mentioned problem is an electrostatic chuck comprising a table for attracting and holding a substrate by static electricity and a lift pin for lifting the substrate after the suction and holding release from the lower side and removing it from the table. A method of removing static electricity remaining on a substrate on a table, wherein one part of the substrate is lifted from the table by continuously performing one or more rounds along a circle centering on the center point of the substrate surface This is a method for removing residual static electricity from an electrostatic chuck.

  According to the method of the first aspect of the present invention, since one portion of the substrate is lifted from the base, there is always a portion in contact with the base, so that even if static electricity remains in a wide range on the substrate, the substrate Will not bounce or misalign. In addition, since one part of the substrate is lifted from the table continuously for one or more rounds along the circle, static electricity remaining on the substrate can be reliably removed over the entire circumferential direction.

A second aspect of the present invention provides a base for attracting and holding the substrate by static electricity, a lift pin for lifting the substrate after the suction and holding release from the lower side and removing it from the base, and a portion of the substrate in a circle centered on the center point of the substrate surface An electrostatic chuck comprising: a residual static electricity removing mechanism that continuously floats along the base.
In the invention 3, the residual static electricity removing mechanism of the invention 2 is provided with a circumferential groove provided at a position where the peripheral portion of the substrate on the upper surface of the table is disposed, and a substrate lifting member disposed along a circle of the circumferential groove. And a driving device for continuously raising the substrate elevating member along the circle.

A fourth aspect of the present invention is an electrostatic chuck in which the substrate elevating member of the third aspect is a ring that enters the circumferential groove.
According to the electrostatic chucks of the inventions 2 to 4, since one place of the substrate can be lifted from the table, it can be continuously performed one or more times along a circle centering on the center point of the substrate surface. The methods 1 and 2 can be easily performed.

Hereinafter, embodiments of the present invention will be described.
FIG. 1 is a plan view (a) and a cross-sectional view (b) showing the electrostatic chuck of this embodiment.
FIG.1 (b) is a figure corresponding to each cross section of AA of FIG.1 (a), BB, CC, DD.
This electrostatic chuck includes a base 2 for attracting and holding the circular substrate 1 by static electricity, and lift pins 3 for lifting the substrate 1 after the suction and holding release from the lower side and removing it from the base. The base 2 is provided with a through hole 21 through which the lift pin 3 passes. A circumferential groove 22 is provided on the upper surface of the table 2 at a position where the peripheral edge of the substrate 1 is disposed. The circumferential groove 22 is preferably arranged, for example, at a position 1 cm inside from the outer periphery of the substrate 1.

Eight through holes 23 are provided at equal intervals along the circle of the circumferential groove 22. Each through hole 23 passes through the bottom surface of the circumferential groove 22. In the circumferential groove 22, a ring (substrate elevating member) 4 in which round bars are bent and joined in an annular shape is arranged. In each through hole 23, pins 5 that raise and lower the ring 4 at eight locations along the circle of the circumferential groove 22 are arranged.
Each pin 5 is connected to an elevating mechanism (not shown), and the control device connected to each elevating mechanism causes the eight pins 5 to sequentially descend along a circle of the circumferential groove 22 and then descend. It is configured. These pins 5, the lifting mechanism and the control device constitute the drive device of the present invention. In addition, the drive device, the circumferential groove 22 and the ring 4 constitute the residual static electricity removing mechanism of the present invention.

  For example, the electrostatic chuck is used by being installed in a chamber of a reactive ion etching apparatus. In this case, the wafer (substrate) 1 is adsorbed and held on the table 2 by static electricity, and reactive ion etching is performed in a state where the chamber is sealed, and then the lid of the chamber is opened. Then, when removing the wafer 1 from the table 2, the control device controls the lifting mechanism so that the eight pins 5 are sequentially raised by a predetermined amount along the circle of the circumferential groove 22 and then lowered.

Accordingly, as shown in FIG. 2, the ring 4 has a portion on the upper side of the rising pin 5 protruding above the table 2 and comes into contact with a part of the substrate 1 existing thereon. As a result of this contact, the substrate 1 is elastically deformed and lifted from the table 2 within a range in which the pushing force from the ring 4 acts, and a portion outside this range remains in contact with the table 2.
For example, first, when the AA cross section of FIG. 1A is in this state, the pin 5 existing in the AA cross section is lowered, and at the same time, the pin 5 existing in the BB cross section is raised. Let the state shown in FIG. Next, the pin 5 present in the BB cross section is lowered, and at the same time, the pin 5 present in the CC cross section is raised to the state shown in FIG. Next, the pin 5 existing in the CC cross section is lowered, and at the same time, the pin 5 existing in the DD cross section is raised to the state shown in FIG.

  As a result, the part of the substrate 1 that is lifted from the base 2 is continuously performed around the circle of the circumferential groove 22 (a circle centered on the center point of the substrate surface). This operation is performed after the grounded lift pins 3 are in contact with the substrate 1 as shown in FIG. 1, so that the static electricity remaining on the substrate 1 can be ensured over the entire circumferential direction. Removed. And after finishing this operation, if the board | substrate 1 is lifted from the lower side with the lift pin 3, and it removes from a base, the board | substrate 1 will not jump or a position shift will not arise in the board | substrate 1. FIG.

In this embodiment, the ring 4 is moved up and down by eight pins 5 arranged at equal intervals along the circle of the circumferential groove 22, but the ring is formed by the balls arranged along the circle of the circumferential groove 22. 4 may be raised and lowered.
In addition, the method of the present invention is carried out using an electrostatic chuck in which the ring 4 is used as the substrate elevating member and the circumferential groove 22 into which the ring 4 is inserted is provided in the table 2. Is not limited to this. For example, the method of the present invention may be carried out by using an electrostatic chuck in which a plurality of lift pins are arranged along a circle centered on the center point of the substrate surface and more usually on the peripheral edge side of the substrate. it can.

The top view (a) and sectional drawing (b) which show the electrostatic chuck of embodiment. Sectional drawing which shows the state which raised one place of the board | substrate from the stand.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Wafer (substrate), 2 ... Stand, 21 ... Through-hole, 22 ... Circumferential groove, 23 ... Through-hole, 3 ... Lift pin, 4 ... Ring (substrate raising / lowering member), 5 ... Pin (drive device).

Claims (4)

The electrostatic chuck with a base that holds the substrate by electrostatic suction and a lift pin that lifts the substrate after the suction holding release from the lower side and removes it from the base, removes the static electricity remaining on the substrate on the base after releasing the suction holding. A method,
A method for removing residual static electricity from an electrostatic chuck, comprising: continuously raising one portion of the substrate from the table along a circle centering on a central point of the substrate surface.   A base for attracting and holding the substrate with static electricity, a lift pin for lifting the substrate after the suction and holding release from the lower side to remove it from the base, and one place of the substrate continuously along a circle centering on the center point of the substrate surface And a residual static electricity removing mechanism that floats from the table.   The residual static electricity removing mechanism includes a circumferential groove provided at a position where the peripheral portion of the substrate on the upper surface of the table is disposed, a substrate lifting member disposed along a circle of the circumferential groove, and the substrate lifting member. The electrostatic chuck according to claim 2, comprising: a drive device that continuously raises along the circle.   The electrostatic chuck according to claim 3, wherein the substrate elevating member is a ring that enters the circumferential groove.

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