KR101911511B1 - Method for aligning wafer - Google Patents

Abstract

According to the present invention, a method for aligning a wafer comprises: a first step of placing a wafer with an aligning pattern on a rotary plate; a second step of photographing the wafer placed on the rotary plate from above; a third step of extracting circumference coordinates of the wafer; a fourth step of calculating a center coordinate and a radius of the wafer; a fifth step of calculating the distance from the center coordinate of the wafer to each circumference coordinate to determine a point where the distance to the center coordinate is different from the radius of the wafer as an aligning pattern; a sixth step of calculating the angle between a virtual line connecting the center coordinate of the wafer and a center point of the aligning pattern and a preset aligning reference line; and a seventh step of rotating the wafer by the angle calculated in the sixth step to position the center point of the aligning pattern on the aligning reference line. If the method for aligning a wafer is used, an aligning pattern formed on a wafer can be quickly sensed without rotating the wafer; the wafer can be accurately aligned within a prescribed period of time regardless of the size of the wafer; and the accuracy of a wafer aligning direction can be improved.

Description

Method for aligning wafer [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of aligning an alignment pattern formed on a wafer in one direction and more particularly to a wafer aligning method capable of minimizing wafer aligning time, .

2. Description of the Related Art In general, a semiconductor wafer is processed by processing several wafers at a time. Such a semiconductor wafer has a certain direction, and must be moved and supplied in accordance with this direction to complete a normal semiconductor wafer.

Therefore, it is essential to align the semiconductor wafers in the semiconductor wafer fabrication process. In order to align such a semiconductor wafer, a flat surface called a flat zone is formed on one side of a circular semiconductor wafer, or a V-shaped or U-shaped wedge-shaped notch is formed on a part thereof, Perform the operation.

The aligning apparatus for aligning a semiconductor wafer has a rotation sensor such as a vacuum chuck for rotating a semiconductor wafer and a detection sensor for detecting a notch or a flat zone (hereinafter, abbreviated as "alignment pattern") formed on a semiconductor wafer , The alignment sensor detects the alignment pattern of the semiconductor wafer rotated by the rotation device and aligns the direction of the semiconductor wafer by stopping the alignment of the aligner in a predetermined direction .

The prior art of such an aligner is a buffer arm apparatus for a semiconductor wafer aligner and an aligning method using it (Korean Patent Registration No. 10-0721567). The above-described conventional technique detects the position of the alignment pattern by irradiating the detection light horizontally toward the edge of the wafer, and then rotates the wafer so that the alignment pattern faces a preset reference direction, As shown in FIG.

However, in the case of aligning the wafers by the above-described method, it is difficult to accurately measure the size and depth of the alignment pattern. In order to sense the positions and the number of the alignment patterns, the wafers must be rotated by 360 ° or more It takes a lot of time to detect the pattern.

Of course, if the wafer is rotated rapidly, the time required to detect the alignment pattern can be shortened. However, in order to accurately detect the alignment pattern by the sensor portion, there is a limit to increase the rotation speed of the wafer. There is a problem that it is difficult to shorten. In particular, there is a disadvantage in that it takes more time to align large wafers whose diameter has been increased from 300 mm to 450 mm.

KR 10-0721567 B1

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above problems, and it is an object of the present invention to provide an apparatus and a method for quickly aligning patterns formed on a wafer without rotating the wafer and accurately aligning wafers within a predetermined time, It is an object of the present invention to provide a wafer alignment method capable of improving the accuracy of wafer alignment.

According to another aspect of the present invention, there is provided a wafer aligning method,

A first step of placing the wafer on which the alignment pattern is formed on the rotating plate;

A second step of photographing the wafer placed on the rotary plate from above;

A third step of extracting a peripheral coordinate of the wafer;

A fourth step of calculating a center coordinate and a radius of the wafer;

A fifth step of calculating a distance from the center coordinates of the wafer to each of the peripheral coordinates to determine a point at which the distance to the center coordinate differs from the radius of the wafer as an alignment pattern;

A sixth step of calculating an angle between a virtual line connecting a center coordinate of the wafer and a center point of the alignment pattern and an alignment reference line set in advance;

A seventh step of rotating the wafer by an angle calculated in the sixth step and positioning a center point of the alignment pattern on the alignment reference line;

.

In the fourth step,

A fourth step of arbitrarily selecting three coordinates among the peripheral coordinates of the wafer;

A 4-2 step of calculating a center coordinate and a radius of an imaginary circle passing through the three coordinates selected in the step 4-1;

(4-3) calculating an error between the locus of the imaginary circle and the wafer periphery coordinates;

A fourth step of determining whether the error calculated in the step 4-3 is equal to or less than a preset reference value;

If the error calculated in the step 4-3 is equal to or less than a preset reference value, sets the center coordinates and the radius of the virtual circle as the center coordinates and the radius of the wafer, and if the error calculated in the 4- The method returns to step 4-1;

.

In the fifth step,

A part of the periphery of the wafer which is shorter than the radius of the wafer by a predetermined distance or more is selected as the alignment pattern forming section.

In the fifth step,

A center point of the alignment pattern is selected as a point having a shortest distance to a center coordinate of the wafer.

Wherein the first step is configured to seat the wafer on a rotating plate positioned on the illumination plate,

In the third step, coordinates of a point at which the lightness difference of the photographed wafer image exceeds a preset reference value are extracted as the peripheral coordinates of the wafer.

The first step is configured so that when the wafer is placed on the rotary plate, the wafer is located at a position spaced upward by 5 to 10 mm from the upper surface of the illumination plate.

The first step further includes a step of finely adjusting the position of the wafer so that the center of the wafer is located on the rotation axis of the rotation plate.

According to the wafer alignment method of the present invention, even if the wafer is not rotated, the alignment pattern formed on the wafer can be detected quickly, the wafer can be accurately aligned within a predetermined time regardless of the size of the wafer, It is possible to improve the accuracy of the image.

1 is a flowchart of a wafer aligning method according to the present invention.
FIG. 2 is a flowchart showing the process of calculating the center coordinates and the radius of the wafer in detail.
3 is a side view of an apparatus for implementing a wafer alignment method according to the present invention.
4 to 10 are plan views sequentially illustrating a process of aligning wafers using the wafer aligning method according to the present invention.
11 and 12 show an embodiment in which the alignment pattern is formed in a notch shape.

Hereinafter, embodiments of the wafer aligning method according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a flow chart of a wafer aligning method according to the present invention, FIG. 2 is a flowchart showing a process of calculating a center coordinate and a radius of a wafer, and FIG. Fig. 4 to 10 are plan views sequentially illustrating a process of aligning wafers using the wafer aligning method according to the present invention.

The wafer aligning method according to the present invention is a method for aligning a wafer 10 such that a flat zone or a notch (hereinafter abbreviated as "alignment pattern 12") formed on the edge of the wafer 10 is positioned on a preset reference line Even if the position of the alignment pattern 12 is not searched by the detection sensor while rotating the wafer 10, information on the position and the number of the alignment pattern 12 can be obtained, Feature.

That is, the wafer alignment method according to the present invention includes a first step (S10) of placing a wafer (10) on which an alignment pattern (12) is formed on a rotary plate (200) A third step S30 of extracting a peripheral coordinate of the wafer 10 and a fourth step of calculating a center coordinate and a radius of the wafer 10 A fifth step of calculating a distance from the center coordinates of the wafer 10 to each of the peripheral coordinates and determining a point at which the distance to the center coordinate is different from the radius of the wafer 10 as the alignment pattern 12; A sixth step (S60) of calculating an angle between a virtual line connecting the center coordinates of the wafer (10) and the center point of the alignment pattern (12) and an alignment reference line set in advance, The wafer 10 is rotated by an angle calculated in step S60 so that the center point of the alignment pattern 12 is aligned A seventh step S70 of placing the wafer 10 on the reference line, and an eighth step S80 of picking up and transferring the aligned wafer 10.

As described above, according to the present invention, the upper surface of the wafer 10 placed on the rotary plate 200 is photographed so that the distance from the center coordinate of the wafer 10 is shorter than the radius of the wafer 10 It is advantageous in that the length and position of the alignment pattern 12 can be obtained at one time even if the wafer 10 is rotated or a separate sensing sensor is not operated. Therefore, when the wafer alignment method according to the present invention is used, it is not necessary to rotate the wafer 10 by more than 360 degrees, so that the alignment of the wafer 10 can be completed in a shorter time.

Hereinafter, the process of aligning the wafer 10 using the wafer aligning method according to the present invention will be described in detail with reference to FIGS. 3 to 10. FIG.

In order to align the wafer 10 by the wafer aligning method according to the present invention, first, as shown in FIG. 3, an illumination plate 100 for irradiating upward light, A rotating plate 200 positioned to be spaced upward from the upper surface and rotatable about a central axis in the vertical direction and a wafer 10 positioned on the upper side of the rotating plate 200 and seated on the upper surface of the rotating plate 200 It is essential that an alignment device having a camera 300 is required.

The user seats the wafer 10 on the rotating plate 200 shown in Fig. 4 because the seating plate is smaller than the wafer 10, so that the seating plate is completely separated by the wafer 10 It is obscured. In order for the wafer 10 to rotate when the rotation plate 200 is rotated, the center of the wafer 10 must be precisely positioned on the rotation axis of the rotation plate 200. When the wafer 10 is rotated on the rotation plate 200 The center of the wafer 10 may not be precisely positioned on the rotation axis of the rotary plate 200. Accordingly, after the wafer 10 is placed on the rotary plate 200, A process of finely adjusting the position of the wafer 10 to be positioned on the rotation axis of the rotary plate 200 may be added. Such a position adjustment of the wafer 10 is substantially the same as that of the conventional apparatus for processing a wafer 10, and a detailed description of the process for finely adjusting the position of the wafer 10 is omitted.

5, after the upper surface of the wafer 10 is photographed using the camera 300, the coordinates of the periphery of the wafer 10 are extracted. In the photograph of the wafer 10 photographed by the camera 300, the light and dark sharply change at the edge portions of the wafer 10, and the point at which the light and dark sharply changes in this manner is referred to as the peripheral coordinates of the wafer 10 Respectively. At this time, even if the illumination plate 100 is not provided under the wafer 10, if the bottom plate is coated with a color different from that of the wafer 10, a difference in darkness appears at the edge of the wafer 10, It is preferable that the illumination plate 100 is installed as shown in this embodiment so that the contrast is more rapidly changed.

Although the illumination plate 100 has a rectangular plate shape so that the illumination plate 100 and the rotary plate 200 are clearly distinguished from each other in the present embodiment, Or may be formed in a disc shape having a larger diameter. On the other hand, if the wafer 10 is directly contacted with the upper surface of the illumination plate 100, a kind of diffraction phenomenon that the edges of the wafer 10 are spaced apart may occur and the distance between the wafer 10 and the illumination plate 100 If it is too large, there may be a problem that the contrast difference at the edge of the wafer 10 is reduced. Therefore, when the wafer 10 is placed on the rotary plate 200, the wafer 10 is preferably positioned at a position spaced 5 to 10 mm upward from the upper surface of the illumination plate 100 Do.

As described above, the technical idea of extracting the edge coordinates of the object to be photographed is commercialized in the field of measurement, and a detailed description of the method and principle of extracting the peripheral coordinates will be omitted.

When the extraction of the peripheral coordinates of the wafer 10 is completed, it is determined which of the peripheral coordinates of the wafer 10 is the coordinate of the alignment pattern 12. [ At this time, in order to determine which coordinates are the coordinates of the alignment pattern 12, as shown in Fig. 2, a fourth step (S41) of arbitrarily selecting three coordinates of the peripheral coordinates of the wafer 10, 4-2 step (S42) of calculating the center coordinates and radius of the virtual circle passing through the three coordinates selected in the step 4-1 (S41), and calculating the center coordinates and the radius of the circumference coordinates of the wafer 10 (Step S43) of calculating an error between the reference value and the reference value, a fourth step (S44) of determining whether the error calculated in the step 4-3 is equal to or less than a predetermined reference value, If the error calculated in the step 4-3 is equal to or less than a predetermined reference value, the center coordinates and the radius of the virtual circle are set as the center coordinates and the radius of the wafer 10, and the calculation is performed in the 4-3 step (S43) (S45) when the error exceeds the reference value set in advance, the process returns to the step 4-1 (S41).

6, arbitrary three coordinates (A, B, C) of the peripheral coordinates of the wafer 10 are selected and the center point of the virtual circle passing through the three coordinates A, B, O) and the radius (r). At this time, the center point O of the virtual circle is a point where vertically extending lines meet from the center of a straight line connecting two neighboring coordinates. The central point O of the circle passing through three points and the radius r ) Is already known, a detailed description of the method and principle of calculating the center point O and the radius r of the imaginary circle will be omitted.

When the center point O of the virtual circle is selected, the distance between the respective circumferential coordinates of the wafer 10 and the center point O of the virtual circle is measured. The point where the alignment pattern 12 is formed is the same as the radius r of the imaginary circle but the point at which the alignment pattern 12 is formed is the center point O ) Is a relatively short distance (r _s ). Therefore, a point of each circumferential coordinate which is shorter than the radius r of the imaginary circle to the center point O of the virtual circle is determined as the alignment pattern 12.

8, an imaginary circle (dotted circle in FIG. 8) passing through three coordinates is formed on the surface of the wafer 10 And a large error is generated. Therefore, the center point O 'of the virtual circle is shifted from the center point O of the wafer 10, so that the center point O' of the virtual circle is selected as the center point O of the wafer 10 Can not.

Therefore, if at least one of the three coordinates arbitrarily selected as shown in FIG. 8 is the coordinates of the point where the alignment pattern 12 is formed, a step S40 of calculating the center coordinates and the radius of the wafer 10 is newly performed. That is, an error between the locus of the imaginary circle and the coordinates of the periphery of the wafer 10 is calculated (S43), and it is determined whether the calculated error is equal to or less than a preset reference value (S44). If the calculated error is equal to or less than a predetermined reference value 6, it is determined that the three coordinates are the coordinates of the point where the alignment pattern 12 is not formed, and the center coordinates and the radius of the virtual circle are set as the center coordinates and the radius of the wafer 10. 8, it is determined that at least one of the three coordinates is the coordinates of the point where the alignment pattern 12 is formed, and three of the coordinates of the periphery of the wafer 10 The process returns to step S41 to select coordinates.

A virtual line connecting the center point O of the wafer 10 and the center point S of the alignment pattern 12 and the imaginary line connecting the center point O of the wafer 10 and the wafer 10, The angle? Between the alignment reference line connecting the center coordinate O of the reference point P and the previously set reference point P is calculated. 10, the wafer 10 is rotated by the calculated angle &thetas; so that the alignment pattern 12 is aligned with the alignment reference line 12, Is positioned on the alignment reference line.

As described with reference to FIGS. 4 to 10, the wafer alignment method according to the present invention is used to photograph the wafer 10, perform some calculations, and then rotate the wafer 10, The time required for aligning the wafer 10 can be remarkably shortened.

Even in the process of rotating the wafer 10, the wafer 10 is rotated only by an angle (?) Deviated from the alignment reference line and the wafer 10 is rotated by 360 degrees or more. The driving time of the rotating plate 200 is shorter than that of the driving method. Accordingly, the power for driving the rotating plate 200 can be reduced and the time can be shortened.

11 and 12 show an embodiment in which the alignment pattern 12 is formed in a notch shape.

5 to 10, the distance from the center coordinate (O) of the wafer 10 to the flat zone coordinate is shorter than the radius of the wafer 10. In the case where the alignment pattern 12 is a flat zone shape as shown in Figs. The step S50 of collecting the information such as the position of the alignment pattern 12 is performed so that the distance from the periphery of the wafer 10 to the center coordinate O of the wafer 10 is smaller than the radius r of the wafer 10. [ A length shorter than a preset length may be set as a section for forming the alignment pattern 12.

At this time, the alignment pattern 12 may be formed in a flat zone shape, or may be formed in a notch shape as shown in FIG. 11 and FIG. When the alignment pattern 12 is formed in a notch shape, the distance from the center coordinate O of the wafer 10 to the vertex of the notch is the shortest. The step S50 of collecting the information of the alignment pattern 12 may be performed such that a point at which the distance to the center coordinate of the wafer 10 is the shortest among the sections in which the alignment pattern 12 is formed is the center point of the alignment pattern 12 When the alignment of the wafer 10 is completed, the vertex of the notch can be directed to the alignment reference point P as shown in FIG.

As described above, the wafer alignment method according to the present invention does not directly detect the alignment pattern 12 by the sensor but calculates the position and shape of the alignment pattern 12 by photographing the wafer 10 and calculating the distance between coordinates. Even if the alignment pattern 12 is formed in any shape, there is an advantage that the position and size of the alignment pattern 12 can be accurately obtained.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the scope of the present invention is not limited to the disclosed exemplary embodiments. It will also be appreciated that many modifications and variations will be apparent to those skilled in the art without departing from the scope of the present invention.

10: wafer 12: alignment pattern
100: illumination plate 200: rotating plate
300: camera

Claims (7)

In the method of aligning the wafer (10) on which the alignment pattern (12) is formed,
Placing the wafer (10) on the rotary plate (200);
A second step of photographing the wafer (10) while irradiating the rotating plate (200) with light;
A third step of extracting a peripheral coordinate of the wafer 10 using a difference in light and darkness at an edge of the wafer 10;
Calculating an error between the locus of the imaginary circle and the circumferential coordinate of the wafer after calculating the center coordinates and the radius of the imaginary circle passing through the three selected coordinates among the circumferential coordinates of the wafer 10, A fourth step of setting the center coordinates and the radius of the virtual circle calculated as the center coordinates and the radius of the wafer;
The distance from the center coordinates of the wafer 10 to the respective circumferential coordinates of the wafer 10 is calculated so that the distance from the center coordinate of the wafer 10 to the center coordinates of the wafer 10 is smaller than the preset range of the radius of the wafer 10 A point at which the distance from the center of the wafer 10 to the center of the wafer 10 is the shortest is determined as a point where the alignment pattern 12 is formed, A fifth step of selecting the first step;
A sixth step of calculating an angle between an imaginary line connecting the center coordinate of the wafer 10 and the center point of the alignment pattern 12 and an alignment reference line connecting the center coordinate of the wafer 10 and an alignment reference point set in advance, ; And
A seventh step of rotating the wafer 10 by an angle between the imaginary line and the alignment reference line calculated in the sixth step to place the center point of the alignment pattern 12 on the alignment reference line;
≪ / RTI >
delete delete delete The method according to claim 1,
The first step is configured to seat the wafer 10 on the rotary plate 200 positioned on the illumination plate 100,
Wherein the third step extracts the coordinates of a point at which the darkness difference of the image of the photographed wafer (10) exceeds a predetermined reference value, as the peripheral coordinates of the wafer (10).
The method of claim 5,
The first step is such that when the wafer 10 is placed on the rotary plate 200, the wafer 10 is positioned at a position spaced 5 to 10 mm upward from the upper surface of the illumination plate 100 To the wafer alignment.
The method according to claim 1,
Wherein the first step further comprises finely adjusting the position of the wafer (10) so that the center of the wafer (10) is positioned on the rotation axis of the rotary plate (200).

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