JPS59139626A - Automatic alignment of wafer - Google Patents

Abstract

PURPOSE:To improve accuracy in positioning of mask and wafer when wafer is supplied onto a sample board locating the straight part of wafer to almost the specified position by rotating the wafer and thereafter pressing the straight part of wafer and the edge part of wafer isolated from said straigt part to the stopper. CONSTITUTION:A wafer 2 is placed on a storage 3, the stage is inclined and a motor 19 is driven. Thereby, the rollers 12, 13, 14 rotates through a belt 16. When the orientation flat surface comes to be in contact with the rollers 12, 13, 14 arranged at the cut-away part 11, the roller 13 does not come to be in contact with the orientation flat surface of wafer because the roller 13 is located at the inside by a distance (x) from the rollers 12 and 14 at both sides of it. Accordingly, the wafer stops to rotate. At this time, the orientation flat surface of wafer is supported by the rollers 12 and 14 and other circumference is supported by the roller 15. Therefore, positioning and position of wafer to the mask are determined.

Description

[Detailed description of the invention] The present invention relates to a method for automatic wafer alignment.

In the production of semiconductor devices, thin semiconductor plates (wafers)
is used ℃・ru. This wafer has an orientation flat (orientation flat surface) for positioning in which a part of the circular periphery is cut linearly.

By the way, when forming patterns such as semiconductor element areas and wiring on the wafer, in order to maintain the relationship between the position of the pattern already formed on the wafer and the position of the newly formed notch, the wafer and mask are Accurate alignment (
alignment). Conventionally, in automatic alignment devices (automatic aligners), when aligning the mask and Waeno, the
The position of the wafer is automatically detected and aligned, but since the operating range of the wafer that can be automatically aligned is limited, pre-alignment of the wafer is performed in advance.

The following is known as one of the preliminary alignment mechanisms. That is, after the wafer is placed on a stage maintained in a horizontal state in an automatic wafer alignment apparatus, the stage is tilted and the wafer's own weight is used to shift the wafer to one side. Three rotating rollers are arranged close to each other in a nearly straight line around the edge of the stage where the wafer is offset by its own weight, and one roller is installed on the edge of the stage at a position away from the edge of the stage where these three rollers are arranged. Two rollers are provided. The three rollers are arranged almost in a straight line, but the outer peripheral edge of the center roller near the stage periphery is located slightly farther from the stage periphery than the common tangent line close to the stage periphery of the rollers at both ends. The rollers at both ends rotate at the same speed in different directions, and the center roller rotates in the same direction as one of the rollers at both ends. Orientation When the part other than the flat part, that is, the arc-shaped circumferential surface, comes into contact with the three rollers, the wafer is moved between the center roller and one of the rollers at both ends rotating in the same direction. The wafer is rotated by the rollers in the opposite direction to the rotation direction of the two rollers.When the orientation flat surface reaches these three rollers, the center roller is retracted more than the rollers at both ends, causing the orientation flat surface to do not come in contact with
The rollers at both ends are in contact with the orientation flat surface. However, since these rollers rotate in different directions and at a constant speed, the wafer does not rotate because the rotational forces applied to the wafer circumferential surface cancel out both rollers. In addition, in this state, the periphery of the wafer other than the orientation flat surface comes into contact with the surface of the other rollers, which are arranged independently of these three rollers, only due to the wafer's own weight. The alignment direction and position are determined. Therefore, it is built into the stage.
A holding mechanism consisting of a vacuum suction mechanism operates to attract the wafer to the stage surface, and in this state the stage returns to the horizontal position. After that, stop vacuum suction,
Another suction tool, such as a Bernoulli chuck, is automatically operated to suction the wafer on the stage and transport it onto the sample stage of the automatic aligner.

However, even though an aligner with such a mechanism can detect the wafer's orientation surface sufficiently, the positional accuracy of the wafer relative to the mask is still not sufficient. In other words, when the wafer is suctioned and fixed to the stage due to variations in the inclination angle of the stage on which the wafer is placed or vibrations caused by the rotation of the three grouped rollers, the position of the wafer relative to the mask varies, making it difficult to keep the stage horizontal. When the wafer is returned to its original position, the Bernoulli chuck is used to adsorb the wafer, and the wafer is conveyed and placed on the sample stage, the positional accuracy is low.

Therefore, an object of the present invention is to provide an automatic alignment device that improves the precision of alignment between a mask and a wafer when the wafer is supplied onto a sample stage.

In order to achieve such an object, the present invention provides a method for aligning a wafer having a straight portion on a part of its periphery.
The wafer is rotated to align the linear portion to a substantially predetermined position, and then the linear portion of the wafer and the peripheral edge of the wafer separated from the linear portion are pressed against a stopper by an external force. DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention, which is a wafer alignment method, will be specifically explained below using Examples.

1 to 4 show an embodiment of the automatic wafer alignment method according to the present invention.

FIG. 1 is a plan view of the main parts of the device. As shown in the figure,
Reference numeral 2 denotes a wafer on a disk having an orientation flat (orientation surface) 1 with a portion cut out linearly. Reference numeral 3 denotes a stage on which the wafer 2 is placed, and is a disk-shaped stage larger than the wafer 2. This stage 3
As shown in FIGS. 2 and 3, the support bin 6'' is attached via a bearing 5 to a support block 4 formed integrally with the bottom surface of the support bin 6"!r, and is capable of pivoting and tilting. The support bin 6 is fixed to the mounting base 33.

The tilting operation is performed by a mover 7 disposed on the lower surface side of the stage 3.
This is caused by the vertical movement of the stage 3 and the compression coil spring 8 that acts so that the lower surface of the stage 3 is always in contact with the mover 7. That is, the mover 7 is formed in the air cylinder mechanism 9 and is raised by the injection of air, pushing up the stage 3Y and making the stage 3 horizontal, and the restoring force of the compression coil spring 8 due to the exhaust of air from the air cylinder mechanism 9. tilted by. A stopper 10 is disposed near the mounting portion of the compression coil spring 8 of the stage 3, so that when the stage 3 rises due to the rise of the movable element 7, the stage 3
The lower surface of the stage 3 hits this stopper 1°, and the stage 3 is kept horizontal.

Furthermore, a notch 11 is formed at the peripheral edge of the stage 3. In this notch 11, three rotating rows 21 are installed so as to support the periphery of the wafer 2 that slides down on the stage 3 due to its own weight when the stage 3 is tilted.
2, 13, and 14 are arranged at ℃・ru. These rollers 12, 13-, and 14 are arranged on a curve with a larger curvature than the curvature of the wafer 2 circumference, and the distance between the rollers 12 and 14 on both end sides is shorter than the length of the orientation flat surface 1 of the wafer 2. It is arranged so that it looks like this. Also, the center roller 13 should be retracted by an amount X to the outside of the stage 3 from the common tangent line of the rollers 12 and 14 on both sides. Also,
A roller 15 is integrally arranged on the stage 3 at a different position from these three rollers 12, 13, and 14. The orientation flat surface 1 of the wafer 2 is in contact with the rollers 12 and 14 at both ends, and the peripheral edge of the wafer 2 other than the orientation flat surface is in contact with the rollers]5
By contacting the wafer 2, the alignment direction and position of the wafer 2 with respect to the mask are determined. In addition, one part of the orientation flat surface of the wafer 2 has three rollers 12°, 13.
14, the peripheral edge of the wafer 2 contacts the rollers 12, 13, 14, 15, and at a certain degree, the wafer 2 contacts the roller 15 and the central roller 13.

On the other hand, among the rollers 12, 13.14, roller lj,
The wafers 14 are rotated in the same direction, that is, clockwise, by a single belt 16, thereby rotating the wafer counterclockwise.

Further, the roller 12 is disposed so as to be in contact with the outer circumferential surface of the belt 16, so that it rotates in the opposite direction to the two horn rollers 13, 4, that is, to the left. , the belt 16 is wound around a pulley 17, and this goo IJ 17 is rotated by a drive pulley 21 fixed to a rotating shaft 20 of a motor 19 via a drive heald 18Y.

On the other hand, when stage 3 becomes horizontal, way 7 and 2
Stopper 2 consisting of a bearing for regulating the position of
Two rollers 2 are disposed facing downward on the mounting plate 31. That is, as shown in FIG. In addition, the independent roller 15 is also used as a stopper.A pusher mechanism 23 is also provided on the periphery of the stage opposite to the position where these stoppers 22 are provided so as to bring the periphery of the wafer 2 into contact with these stoppers 22. As shown in detail in FIG. 4, this pusher mechanism 23 swings a block 27 supported by a pin 26 at the tip of a rod 25 of an air cylinder mechanism 24 provided on the underside of the stage 3. A rotatable roller 28 is attached to the upper end of the block 27, and is pushed by the rod 25 to move the stage only when the stage 3 is horizontal and when positioning the wafer. , facing the circumferential surface of the wafer 2. In other words, the pusher mechanism 23 and the cylinder mechanism 24 are both disposed on the underside of the stage 3, and a torsion coil spring 29 moves the roller 28 away from the center of the stage. In this case, the upper end of the roller 28 is below the upper surface of the stage 3.

Furthermore, suction holes 30 for vacuum suctioning the wafer 2 are provided on the upper surface of the stage 3.

Next, the wafer positioning operation will be explained using the second starting point. First, the wafer 2 is placed on the stage 3, the stage 3 is tilted, and the motor 19 is driven. Then, the rollers 12, 13 .
14 rotates. At this time, if the orientation flat surface 1 of the wafer 2 does not face the three rollers, the wafer 2
The peripheral edges other than the orientation flat surface are rollers 12, 13, 14.1
5, or there is (・ contacts the independent roller 15 and the central roller 13. And, if it simply contacts the central roller 13 (・, of course, the three Even when the two rollers 12, 13, 14 are in contact with the rollers 12, 13, 14, the rotation direction is opposite and the speed is constant, so the forces applied to the wafer cancel each other out, so the wafer receives rotation from the central row 213. The roller 12 whose orientation flat surface is disposed in the notch 11 rotates to the left by force.
゜When facing 13 and 14, roller 13 is connected to roller 1 at both ends.
Since it is recessed by X from 2.14, it does not contact the orientation flat surface of the wafer. The wafer then stops rotating. At this time, the orientation flat surface of the wafer is 2
The wafer is supported by one roller 12, 14 and the other peripheral edge is supported by roller 15, thereby determining the alignment and position of the wafer with respect to the mask.

Next, the vacuum suction mechanism of stage 3 operates and the suction hole 3
2 is vacuum-adsorbed onto stage 3 via 0.

After that, the mover 7 rises and the stage 3 returns to the horizontal position. At this time, vacuum adsorb the wafer 2 to the stage 3 (・
Otherwise, a portion of the orientation flat surface of the wafer will slide into the gap 32 (FIG. 3) between the lower surface of the stopper 22 and the upper surface of the roller 12.degree. 14 when the stage moves horizontally. If the stage is further raised with a part of the orientation flat surface of the wafer having slipped into the gap 32, the part of the orientation flat surface will hit the lower end of the positioning stopper 22, and the orientation flat surface will be damaged. Therefore, when returning the stage to the horizontal position without the wafer being attracted to the stage, in order to prevent the damage described above, a mechanism such as °C is used to prevent part of the orientation flat surface from sliding below the stopper even if the wafer is displaced. It is preferable to provide

Next, when the stage 3 returns to the horizontal position, the vacuum suction holding is released. After that, the air cylinder mechanism 24 is activated, and the rod 25 pushes the button mechanism 23, so that the block 27 rotates around the bin 26, and the roller 28 attached to the block 27 moves around the periphery of Ueno-2. Press. As a result, wafer 2 remains horizontal.
The position of the wafer with respect to the mask is determined by pressing its peripheral surface against the stopper 22 and the independent row 215,
Prealignment ends.

After that, the suction tool that suctions the wafer to the stage again through the suction hole 30 and transports the wafer to the sample stage for alignment reaches the stage, and after the wafer is suctioned by the suction tool, the vacuum of the suction hole is released. The wafer is released and transferred onto the sample stage by the suction tool.

According to such an embodiment, after the alignment direction of the wafer with respect to the mask is determined, that is, after the orientation flat surface is detected, the position of the wafer with respect to the mask is corrected when the wafer returns to horizontal. In order to do
The pre-alignment of Ueno becomes more accurate, and the time required for alignment can be shortened.

It should be noted that the present invention is not limited to the embodiment described above.For example, in the embodiment described above, the temperature range from the drive pulley 21 to the drive belt 18.
Although the belt 16 is rotated via the pulley 17, the belt 16 may also be connected directly to the drive boob IJ21.

As described above, according to the wafer alignment method of the present invention, the positional accuracy during wafer feeding can be improved.

[Brief explanation of drawings]

FIG. 1 is a plan view of essential parts of an automatic alignment device for Ueno\ according to an embodiment of the present invention, and this figure shows the relationship between a stage, a positioning stopper, and a pusher mechanism. FIG. 2 is a plan view of a main part of an automatic alignment device according to an embodiment of the present invention, FIG. 3 is a sectional view of a main part of an automatic alignment device according to an embodiment of the present invention, and FIG. FIG. 2 is a sectional view of a main part showing the structure of a button mechanism of an automatic alignment device according to an embodiment. 1...Orientation 7 rails, 2...Wafer, 3...Stage, 4...Support block, 5...Bearing, 6...Support pin, 7...Scillator, 8...Compression coil Spring, 9...Air cylinder mechanism, io...
Stoknock, 11...notch, 12-14...roller,
15...Independent roller, 16...Belt, 17...Pulley, 18...Drive belt, 19...Motor, 20...
...Rotating shaft, 21... Drive pulley, 22... Stopper, 23... Button mechanism, 24... Air cylinder mechanism, 25... O-nod, 26... Pin, 27...
Block, 28...Roller, 29...Torsion coil spring, 30...Adsorption hole, 31...Mounting plate, 32...Gap, 33...Mounting base.

Claims (1)

[Claims] 1° When aligning a wafer having a straight part on a part of its periphery, the straight part of the wafer is aligned approximately at a predetermined position by rotating the wafer, and then the straight part of the wafer and the straight part are aligned by an external force. A wafer alignment method characterized by pressing a peripheral edge of a wafer isolated from a stopper against a stopper.