JP3038956B2 - Reticle alignment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of aligning a reticle, and more particularly to a method of aligning a reticle with respect to a stepper in a rotational direction.

[0002]

2. Description of the Related Art In a conventional step-and-repeat type stepper, a method of aligning a stepper body and a reticle set therein in the rotational direction is shown in FIG.
The reticle-side pattern 4 is provided in the X and Y directions on the reticle, and the rectangular stepper-side pattern 3 is provided on the stepper-side wafer stage. The optical signal is read and aligned so that the rectangle of the stepper-side pattern 3 is set at the center position of the stepped portion. That is, the position shown in FIG. 4B is a proper position, and usually, the determination as to whether the position is a proper position is made by detecting the symmetry of the reflected light signal.

[0003]

In this conventional method of aligning the reticle in the rotational direction, the X, Y
Since there is only one positioning pattern on the axis, there is a problem that the detection accuracy is reduced depending on the position of the rotation center. That is, as shown in FIG. 5B, when the alignment is insufficient and the stepper-side pattern 4 and the reticle-side pattern 3 are displaced, it can be clearly distinguished. However, as shown in FIG. It cannot be distinguished from the case where the alignment is performed and the case where the alignment is insufficient but the alignment pattern is almost matched as in the case of FIG. Due to the difficult structure, there were difficulties in positioning in the rotational direction.

[0004]

SUMMARY OF THE INVENTION A reticle positioning method according to the present invention is a method for aligning X and Y on a wafer stage of a stepper.
Two repetitive patterns with a fixed width and spacing are provided on the axis, each two in total, and four or more repetitive patterns that partially match this pattern and differ in spacing are provided near the outer periphery of the reticle. This is a method for performing alignment by detecting interference images from both patterns.

[0005]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. FIG.
1 is a conceptual diagram of a first embodiment of the present invention. That is, a total of four repetitive patterns having a constant width and a total of two spaces are provided on the X and Y axes on the wafer stage 1 and the reticle 2 in FIG. .
This will be described in detail with reference to an enlarged view of FIG. 2. For example, the stepper-side pattern 4 of FIG.
On the reticle, a pattern shown by a reticle-side pattern 3 in FIG.

[0006] These patterns, both patterns when the width L ₁₁ each other in the same, has a repetitive pattern spacing S ₁₁ and S ₁₂ are different, the center portion A-A, consistent along the a-a line The appropriate position can be determined with extremely high positional accuracy by detecting the interference image from the object. Also,
Since four patterns are arranged in the periphery of the reticle, the interval between the patterns is long, and any deviation in the rotation direction can be detected as a deviation of any one of the patterns. It is possible to prevent the setting from being shifted in the rotation direction.

FIG. 3 shows a pattern according to a second embodiment of the present invention. The arrangement of the stepper side pattern 4 in FIG. 3B and the reticle side pattern 3 in FIG. Although these patterns are the same, since these patterns can detect the displacement in both the X and Y directions with one pattern, the positioning can be performed with higher precision. That is, in the X direction, the interval S ₂₁ , S ₂₂
-B, when the central portion is coincident along b-b line, also, Y-direction interference of both patterns when the central portion is coincident along a D-D, d-d line spacing S _31, S ₃₂ An image can be detected. In the above embodiment, the case where four reticle-side patterns are provided near each outer periphery on the reticle has been described. However, four or more reticle-side patterns may be provided to further facilitate alignment.

[0008]

As described above, according to the present invention, two patterns each of which can be detected by an interference image are provided on the wafer stage and the reticle of the stepper on the X and Y axes, that is, a total of four patterns are provided. The positional deviation of the set in the direction of rotation of the reticle can be greatly reduced, and there is an effect that defects in the wafer manufacturing process due to this positional deviation can be significantly reduced.

[Brief description of the drawings]

1A and 1B are conceptual diagrams of a first embodiment of the present invention, wherein FIG. 1A shows a pattern on a wafer stage, and FIG. 1B shows a pattern on a reticle.

FIGS. 2A and 2B are enlarged views showing a shape of a positioning pattern according to the first embodiment of the present invention. FIG. 2A is a diagram showing a reticle side pattern, and FIG. 2B is a diagram showing a stepper side pattern. is there.

FIGS. 3A and 3B are enlarged views showing an alignment pattern shape according to a second embodiment of the present invention. FIG. 3A is a view showing a reticle side pattern, and FIG. 3B is a view showing a stepper side pattern. is there.

4A and 4B are views for explaining a conventional alignment method, wherein FIG. 4A shows a pattern shape before alignment, and FIG. 4B shows a pattern shape after alignment.

5A and 5B are conceptual diagrams of a conventional alignment method. FIG. 5A shows a case where alignment is performed correctly, FIG. 5B shows a case where it is out of alignment, and FIG. FIG.

[Explanation of symbols]

 1 wafer stage 2 reticle 3 reticle side pattern 4 stepper side pattern

Claims (1)

(57) [Claims] 1. A step-and-repeat type stepper reticle alignment method using a reticle as an exposure photomask, a fixed width of two each on the X and Y axes on the wafer stage. And a repeated pattern having an interval, and a pattern completely coincident with the pattern, and at least four repeated patterns having different intervals are provided near each outer periphery on the reticle, and interference images from the both repeated patterns are detected. A reticle positioning method, comprising: