JPH0697266A - Wafer chuck - Google Patents

Abstract

PURPOSE:To improve a wafer chuck in structure so as to lessen chips in yield loss caused by a pawl in contact with the surface of a wafer. CONSTITUTION:A wafer chuck is equipped with a stage 11 where a wafer 1 is placed, two or more pawls 12, and moving means 13 of the same number with the pawls 12. A groove 11a is provided to the stage 11 around its circumferential side face. A motor and a vertical moving mechanism are built in each moving means 13, and the pawl 12 is mounted on the moving means 13 through the intermediary of the vertical moving mechanism. The moving means 13 are fitted into the groove 11a and made to travel separately to move the pawls 12 to points on a wafer 1 where effective chips are not located, and the wafer 1 is clamped with the pawls 12 at the above points.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to the construction of wafer chucks, and more particularly to mechanical wafer chucks. In the wafer processing step of the semiconductor device manufacturing process, it is often necessary to fix the wafer in the processing apparatus. There are various types of chucks for fixing a wafer, such as mechanical chucks, vacuum chucks, electrostatic chucks, etc., but mechanical chucks are mainly used in devices that perform processing in vacuum and at high temperature (eg, sputtering devices). .
However, since the claw of this mechanical chuck directly contacts the surface of the wafer, the desired processing is not performed on the wafer at the part where the claw contacts or the part behind the claw, and the chip at that position is defective. There is a problem that becomes. Therefore, it is desired to prevent such defective chips from occurring as much as possible and increase the yield of non-defective chips per wafer.

[0002]

2. Description of the Related Art In a conventional wafer processing apparatus, the number, shape, size, and arrangement of the claws of a mechanical wafer chuck are peculiar to the wafer processing apparatus, and the positions of the claws are fixed.

Generally, when a wafer is clamped in a wafer processing apparatus, the orientation flat of the wafer is aligned in advance. The nails were placed symmetrically with respect to the orientation flat. Therefore, conventionally, at the stage of designing the chip layout of the wafer, by devising a method such as arranging the chips while avoiding the shadow of the nails, the occurrence of defective chips due to the contact of the nails with the wafer surface is avoided. Had been prevented.

[0004]

However, as described above, since the number, shape, size and arrangement of the claws of the wafer chuck are peculiar to the wafer processing apparatus, they are effective for a certain wafer processing apparatus. Even the chip layout is not always effective for other wafer processing apparatuses. Further, depending on the size of the chip, the total number of chips to be accommodated per wafer may be reduced by arranging the chips while avoiding the shadow of the nail.

An object of the present invention is to solve the above problems and provide a wafer chuck capable of reducing the loss of chip yield due to the contact of the claw with the wafer surface.

[0006]

According to the present invention, there is provided a plurality of [1] stages and a plurality of wafers mounted on the stages, which are pressed against the upper surfaces of the peripheral portions of the wafers to clamp the wafers to the stages. By using a wafer chuck having a claw and a moving means for moving the claw along the outer circumference of the wafer, [2] in [1], the moving means is the same number as the plurality of claws. By having the plurality of moving means move the plurality of claws individually, [3] in [1], a rotating ring is provided, and the plurality of claws are fixed to the rotating ring. This is achieved by arranging the moving means to move the plurality of claws by rotating the rotating ring.

[0007]

According to the present invention, since the position of the nail is variable,
By moving and clamping the claws to a portion on the wafer where no chips are arranged, it is possible to prevent the generation of defective chips even in the chip layout in which the total number of chips accommodated is maximized.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a wafer chuck according to the present invention will be described with reference to FIGS.

FIG. 1 is a diagram showing a first embodiment of the present invention. In the figure, 1 is a wafer to be processed, 11 is a stage on which the wafer 1 is placed, 12 is a claw, and 13 is a moving means. There are a plurality of (four in FIG. 1) moving means 13, each of which is a claw 12, an up-and-down moving mechanism (a solenoid or the like is not shown) for moving the claw 12 in the vertical direction, and a rotating mechanism (a motor or the like, not shown). It is equipped with and is fitted to the groove 11a provided along the outer periphery of the stage 11, so that the stage 11 can be self-propelled around the stage 11.

Details of this portion are shown in FIG. FIG. 2 is a view showing a fitting portion between the moving means and the stage. A rack 21 and a magnetic tape 22 storing position information are fixed to the stage 11 in the groove 11a over the entire circumference, and optical parts are provided at positions corresponding to both ends of the moving range of each moving means 13. Read marks 23 are provided. The moving means 13 has a gear 24 rotated by a built-in motor, a magnetic head 25, and an optical sensor 26, and guide rollers 27 are arranged at various places on its upper and lower surfaces and side surfaces. The guide roller 27 is in close contact with the stage 11 by the action of a spring (not shown).

The gear 24 meshes with the rack 21, and when the motor rotates, the gear 24 moves along the rack 21 while rotating, and the moving means 13 moves. Initially, each moving means 13 is located in a region sandwiched by two optical reading marks 23, and when moving, it first moves clockwise and stops at a position where the optical sensor 26 catches the optical reading mark 23. Next, with this position as the origin, it moves counterclockwise, the magnetic head 25 reads the pulses from the magnetic tape 22, and the pulses are counted by a counter (not shown) provided separately. When the movement is stopped at the time when the predetermined number of pulses are counted, the position becomes the desired position. At this position, the claw 12 may be lowered to clamp the wafer 1.

By the way, when processing various kinds of wafers 1 little by little, the position of the claw 12 must be frequently moved. The present inventor performed control of the nail position by the following two methods. The first method is to obtain the optimum clamp position (the position where the generation of defective chips due to the contact of the claw 12 is minimum) according to the type of the wafer 1 in advance, and to perform the claw according to the loading order of the wafers 1 of various types. It is a method of programming 12 to move to each optimum position.

The second method is the wafer 1 immediately before clamping.
Imaged individually, image processing is performed to determine the effective chip area, and the nail 12 is placed at the optimum clamp position calculated based on this.
Is a method of instructing to move. That is, the image signal from the CCD of the TV camera is
A repeated pattern is found by the pattern matching method to specify an effective chip area, and then a clamp area having a predetermined area is searched for from the peripheral area.

According to this method, many kinds of wafers can be continuously flowed regardless of the kinds of wafers.
It should be noted that this method is particularly advantageous because the device can be used in common when the wafer alignment unit (alignment of the orientation flat) of the wafer processing apparatus has a TV camera.

FIG. 3 is a diagram showing a second embodiment of the present invention. In the figure, the same components as those in FIG. 1 are designated by the same reference numerals. Reference numeral 34 is an auxiliary ring, and 35 is a vertical movement mechanism. In this example, the moving means 13 does not have a built-in vertical moving mechanism, but is instead provided with a spring that biases the claw 12 upward. After the movement of each moving means 13 is completed, the vertical movement mechanism 35
To lower the auxiliary ring 34, which
Lower 12 to clamp wafer 1.

FIG. 4 is a diagram showing a third embodiment of the present invention. In the figure, 41 is a stage, 42 is a claw, and 44 is a rotating ring. The claws 42 correspond to the claws 12 in FIG. 1 and are fixed to the rotating ring 44 at equal intervals. Reference numeral 43 is a moving means including a motor and the like, and 45 is a vertical moving mechanism. By operating the moving means 43, the rotary ring 44 moves together with all the pawls 42, and by operating the vertical moving mechanism 45, the rotary ring 44
Moves down with all the pawls 42 to clamp the wafer 1.

The present invention is not limited to the above embodiments, but can be implemented with various modifications.

[0018]

As described above, according to the present invention,
It is possible to provide a wafer chuck capable of reducing the loss of chip yield due to the contact of the claws with the surface of the wafer, which contributes to cost reduction of semiconductor device manufacturing.

[Brief description of drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention.

FIG. 2 is a diagram showing a fitting unit between a moving unit and a stage.

FIG. 3 is a diagram showing a second embodiment of the present invention.

FIG. 4 is a diagram showing a third embodiment of the present invention.

[Explanation of symbols]

 1 Wafer 11, 41 Stage 11a Groove 12, 42 Claw 13, 43 Moving means 21 Rack 22 Magnetic tape 23 Optical reading mark 24 Gear 25 Magnetic head 26 Optical sensor 27 Guide roller 34 Auxiliary ring 35, 45 Vertical moving mechanism 44 Rotating ring

Claims (3)

[Claims] 1. A stage (11, 41) and the stage (11, 4)
1) a plurality of claws (12, 42) for clamping the wafer (1) to the stage (11, 41) by pressing the upper surface of the peripheral edge of the wafer (1) placed on the claw (12, A wafer chuck having a moving means (13, 43) for moving the wafer (42) along the outer periphery of the wafer (1). 2. The moving means (13) has the same number as the plurality of claws (12), and the plurality of moving means (13) is configured to individually move the plurality of claws (12). The wafer chuck according to claim 1, wherein: 3. A rotating ring (44), wherein the plurality of claws (42) are fixed to the rotating ring (44), and the moving means (43) rotates the rotating ring (44). 2. The wafer chuck according to claim 1, wherein the plurality of claws (42) are configured to move.