JPH03155114A - Positioning of reduction projecting exposure device - Google Patents

Abstract

PURPOSE:To improve positioning accuracy of an exposed body to a reduction projecting exposure device by moving the exposed body in X direction and Y direction at the same time to allow a central position of a mark obtained by detection of scattered light to lap over the central position of a circular orbit of a spot of laser light. CONSTITUTION:Laser light 100 which is scanned to draw a circular orbit 41 on a positioning mark 52 is scattered to produce scattered light when scanned respectively across four step parts 53, 54, 55, 56, which constitute a positioning mark 52 which extends in cross-shaped four directions. Positioning of the positioning mark 52 to an alightment optical system is carried out by moving an X-Y stage in X direction and Y direction simultaneously to allow a central position of the positioning mark 52 which is obtained by detecting scattered light from the positioning mark 52 to lap over the central position of the circular orbit 41; thereby, deviation is not produced in positioning of Y direction during positioning in X direction and accuracy of positioning can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for aligning a reduction projection exposure apparatus used for manufacturing semiconductor devices.

[Prior Art] In the alignment method of a general reduction projection exposure apparatus used for manufacturing semiconductor devices, etc., alignment marks such as a cross or an L-shape extending in two different directions along the exposure surface of the wafer are used. A silicon step or the like is provided at a predetermined position on the exposure surface, and the wafer is placed on an XY stage. Here, first, laser light is scanned linearly in the X direction along the exposure surface at a predetermined part of the wafer including the alignment mark, and the scattered light or diffracted light of the laser light is Detect and mark the positioning mark
The position of the wafer in the X direction is determined, and the position of the wafer is aligned in the X direction with respect to the reduction projection exposure apparatus using the requested position of the alignment mark as a reference by moving the XY stage in the X direction. Next, similarly for the Y direction, the laser beam is scanned linearly in the Y direction along the exposure surface at a predetermined portion on the wafer including the alignment mark,
The position of the alignment mark in the Y direction is determined by detecting the scattered or diffracted light of the laser beam caused by the alignment mark that intersects with the scanning line of the laser beam, and the reduced projection is performed based on the requested position of the alignment mark. The wafer is aligned in the Y direction with respect to the exposure apparatus by moving the X-Y stage in the Y direction.

In addition to the method described above, the following method is also used. That is, in the method described above, instead of scanning the laser beam in the X direction, the wafer is vibrated linearly in the The position in the X direction is determined and the wafer is aligned in the X direction. Similarly, in the Y direction, instead of scanning the laser beam in the Y direction, the wafer is vibrated linearly in the Y direction, and the scattered or diffracted light from the stationary laser beam is detected to mark the alignment mark. The position of the wafer in the Y direction is determined and the wafer is aligned in the Y direction.

[Problems to be Solved by the Invention] In reduction projection exposure apparatuses, it is generally desired to improve the accuracy of alignment.

However, in the above-mentioned alignment method of the conventional reduction projection exposure apparatus, alignment in the X direction and Y direction is first performed separately, so that the alignment is already completed while alignment in one direction is being performed. A deviation occurs in the alignment of the other side, resulting in a decrease in alignment accuracy.

Furthermore, in the alignment method of the conventional reduction projection exposure apparatus described above, alignment in the X direction and Y direction is performed separately. If you do,
Compared to when the laser beam is incident perpendicularly, the position of the detected scattered or diffracted light shifts depending on the inclination of the laser beam,
For this reason, the position of the alignment mark in the X direction and Y direction determined by the detected scattered light or diffracted light will shift accordingly depending on the shift of the scattered light or diffracted light, resulting in a decrease in alignment accuracy. Put it away.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for positioning a reduction projection exposure apparatus that can improve the accuracy of alignment of a display body in the reduction projection exposure apparatus.

[Means for Solving the Problems] According to the present invention, the object is to provide a position where a predetermined portion of the exposed surface of an exposed object includes a stepped portion extending in at least two different directions along the exposed surface. arranging an alignment mark, scanning the C-laser beam so that the spot of the laser beam draws a circular orbit in the predetermined portion, detecting scattered light of the scanned laser beam by the alignment mark, and detecting the scattered light of the scanned laser beam by the alignment mark; The center position of the alignment mark on the X-Y coordinates along the surface to be exposed is determined by the scattered light, and the center position of the requested alignment mark is determined from the X-Y coordinates along the exposed surface.
- the position of the exposed object relative to the reduced projection exposure apparatus by simultaneously moving the exposed object in the X and Y directions relative to the reduced projection exposure apparatus so as to overlap the center position of the circular orbit on the Y coordinate; This is achieved by an alignment method for a reduction projection exposure apparatus, which is characterized by alignment.

[Function] In the alignment method of the reduction projection exposure apparatus of the present invention, an alignment mark including a stepped portion extending in at least two different directions along the exposed surface is formed on a predetermined portion of the exposed surface of the exposed object. Place. The laser beam is scanned so that the spot of the laser beam traces a circular orbit in a predetermined portion where the alignment mark is arranged. Here, when the scanned laser beam is scanned across the step portion of the alignment mark, it is scattered by the step portion, and scattered light is generated. This scattered light is detected, and the center position of the alignment mark on the X-Y coordinates along the surface exposed by the detected scattered light is determined. On the X-Y coordinates, move the exposed object simultaneously in the X direction and the By doing so, the object to be exposed is aligned with respect to the reduction projection exposure apparatus.

Therefore, according to the positioning method of the reduction projection exposure apparatus of the present invention, since the positioning in the X direction and the There will be no deviation in the alignment of the other side, and the accuracy of alignment can be improved. Furthermore, since the laser beam is scanned so that the spot of the laser beam traces a circular orbit, when the laser beam is incident obliquely, the laser beam is scanned in at least two directions, compared to when the laser beam is incident perpendicularly. The respective positions of the scattered light scattered and detected by each of the extending step portions shift according to the inclination of the laser light, but the respective shifts of the detected scattered light are caused by the position of each detected scattered light being along the circular trajectory of the laser light spot. Since this is a deviation, the center position of the alignment mark found as the center position of the circular orbit will be at the same position as the center position of the alignment mark found when the laser beam is incident perpendicularly. accuracy can be improved.

These effects of the present invention will become clearer from the following examples of the present invention, and other effects of the present invention will become clearer.

[Example] Embodiments of the present invention will be described based on the drawings.

A reduction projection exposure apparatus 1 used in a method for positioning a reduction projection exposure apparatus, which is an embodiment of the present invention, is shown in FIG. A wafer alignment mark 52, which is illustrated in FIG. 2 and applied to the reduction projection exposure apparatus 1, is illustrated in FIG. 3 in an enlarged perspective view.

In FIG. 1, a wafer 50 as an object to be exposed is placed on an XY stage 11 of a reduction projection exposure apparatus 1. When placing the wafer 50 on the XY stage 11, rough positioning is first performed using the orientation flat of the wafer 50. The upper surface 51 of the wafer 50, which is the surface to be exposed, is coated with a photosensitive material such as a suitable photoresist, and the main portion of the upper surface 5I is for forming semiconductor elements. On the side of the portion of the upper surface 51 where the semiconductor element is formed, there is an alignment mark 5 that extends along the upper surface 51 in at least two different directions, the X direction and the X direction, and includes a cross-shaped stepped portion.
2 is provided. The step portion is composed of a silicon step, an oxide film step, or a metal step.

The shape of the stepped portion may be an L-shape or an M-shape in addition to a cross.

In reduction projection exposure using the reduction projection exposure apparatus 1, first, light emitted by the mercury lamp 2 is focused by the condensing mirror 3, mirror 4, lens 5, and inch gray scale. The focused light enters the reticle 9 via the mirror 7 and the lens 8, and the light transmitted through the reticle 9 enters the reduction lens 1.
An image is formed on the wafer 50 through 0, and the wafer 50 is exposed. The movement of the X-Y stage 11 in the X direction and the X direction by the two-direction moving device 18 and the exposure are repeated to form a large number of semiconductor elements of the same type on the wafer 50. Note that a plurality of semiconductor element patterns may be formed on the reticle 9 and the plurality of semiconductor elements may be simultaneously formed by -times of exposure.

In order to perform such reduction projection exposure, it is necessary to accurately align the reticle 9 and the wafer 50 prior to the above-mentioned exposure operation. In the positioning in this embodiment, first, the reticle 9 with respect to the X-Y stage 11 is
, read the position of the alignment optical system 20 of the reduction projection exposure apparatus 1 with respect to the X-Y stage 11, and set the alignment mark 52 for each exposure based on the positions of the reticle 9 and the alignment optical system 20. By aligning the reticle 9 and the alignment optical system 20, the reticle 9 and the wafer 50 are sequentially aligned quickly and accurately.

First, in order to position the reticle 9 with respect to the XY stage 11, a translucent mark 17 is provided on the reticle 9, and a stage target 12 is provided on the XY stage 11. The stage target 12 is monitored by the video monitor 15.
is monitored through mark 17 and via mirror 16. While monitoring in this manner, the reticle 9 is moved by a reticle moving means (not shown) to align the mark 17 with the stage target 12. As described above, the reticle 9 is positioned, and the reticle 9 is fixed at the position.

Next, in order to read the position of the alignment optical system 20 with respect to the X-Y stage 11, the X-Y stage 11 is moved by the two-direction moving device 18, and the stage target 12 is moved below the alignment optical system 2G.

Here, the laser beam 10G of the alignment optical system 20 is scanned to collect the scattered light by the stage target 12 on the CCD.
The X-Y coordinates detected by the area sensor 28 and when the scattered light reaches its maximum are read as the spot position coordinates of the laser beam 10G.

Based on the positions of the reticle 9 and the alignment optical system 20 obtained as above, the alignment mark 52 and the alignment optical system 2 are set as described in detail below.
Perform alignment with G.

In the alignment optical system 20, a laser beam emitted by a laser light source 21 for alignment is expanded by a condenser lens 22 and converted into parallel light via a lens 23.
incident on the rotor 24. As shown in an enlarged perspective view in FIG. 2, the rotor 24 is composed of a disc-shaped main body 3L, and rotates around a rotation center shaft 32 by a drive mechanism (not shown). A hole 33 is provided beside the rotation center shaft 32 and passes through the disc-shaped main body 31 in the direction of the rotation center shaft 32 . Therefore,
The mirror 25 passes through the rotor 24 through the rotating hole 33.
The spot of the laser beam 10G traces a circular orbit on the portion of the wafer 50 where the alignment mark 52 is provided.

As shown in the enlarged perspective view in FIG. 3, the laser beam 100 scanned in a circular orbit 41 on the alignment mark 52 is applied to the four alignment marks 52 that extend in four directions in a cross shape. Step portions 53, 54, 55 and 5
6. Therefore, the circular trajectory 41 of the spot of the laser beam 100 is 4 times with respect to the alignment mark 52 located within an arbitrary range where the alignment mark 52 may exist due to errors caused by the rough alignment caused by the orientation flat 3 mentioned above. Two step portions 53
．． 54. The circular orbit 4 crosses each of 55 and 56.
! The rotor 24 and the like are configured such that the diameter thereof is, for example, about 50 μm to 10 μm in diameter.

The laser beam 10G scanned in this manner is scattered as it is scanned across each of the four step portions 53, 54, 55 and 56, and scattered light is generated. A part of this scattered light is collected by the lens 26 and reflected by the mirror 27, and then the CC
It is detected by the D area sensor 28. The state of the scattered light detected here will be explained using FIGS. 4 and 5.

FIG. 4 shows a plan view of the alignment mark 52 and the circular trajectories 40 and 41 of the spot of the laser beam 100 scanned over the alignment mark 52. In the figure, a circular orbit 40 represents the circular orbit of the spot of the laser beam 100 in a state where ideal alignment has been completed, and the center point of the circular orbit 40 coincides with the center point 0 of the alignment mark 52. There is. In this state, A is a point that crosses the four stepped portions 53, 54, 55 and 56 on the circular orbit 40.
, B, C and D, scattered light is generated. On the other hand, in the figure, a circular orbit 41 represents the circular orbit of the spot of the laser beam 100 in a state where alignment is being performed, and the center point 01 of the circular orbit 41 is shifted from the center point O of the alignment mark 52. ing. In this state, scattered light is generated on the circular orbit 41 at points A1, B1, C1, and Dl that cross the four stepped portions 53, 54, 55, and 56.

FIG. 5(a) shows the circular orbit 4 when the spot of the laser beam 100 is scanned on the circular orbit 40 in FIG.
It shows the intensity P of the detected scattered light with respect to the scanning distance r from the starting point S of arbitrary scanning along 0. Figure 5 (b
) indicates the intensity P of the detected scattered light with respect to the scanning distance r from the starting point S of an arbitrary scan along the circular orbit 41 when the laser beam spot is scanned on the circular orbit 41 in FIG. ing.

In FIG. 5(3), there are four points A and B on the orbit 40.

The peaks of scattered light generated in C and D are arranged at equal intervals with respect to the scanning distance r in the figure. here,
As mentioned above, the size of the circular orbit 41 is, for example, 50μ in diameter.
When the distance is about 100 μm from m, the interval between the four peaks of scattered light is about 50×π μm to 100×π μm. In addition, to be more precise, the peaks of the scattered light corresponding to points A, B, C, and D are at the four step portions 53.
54, 55 and 56 each consist of two adjacent peaks with an interval corresponding to the width of the step crossed by the circular orbit 40. This is because scattered light is generated at both side edges of the stepped portion.

In FIG. 5(b), four points A0, B1,
The peaks of scattered light generated at C1 and Dl are not arranged at equal intervals with respect to the scanning distance r in the same figure,
The peaks of the scattered light corresponding to points A, , B, , C, and Dl are respectively △a1△ compared to the case of
b1 ΔC and Δd are shifted. Therefore, △a1△b1△
From C and Δd, the deviation ΔX in the X direction and the deviation ΔY in the Y direction between the center point 01 and the center point 0 can be easily obtained by calculation.

The geometric mean of △X and △Y obtained in this way (△
Two-direction moving device 1 so as to minimize X+△y)I/2
8, the X-Y stage 11 is moved simultaneously in the X direction and the Y direction. Such irradiation of laser light +00, detection of scattered light, and movement of the X-Y stage 11 are repeated as necessary, and finally, A, B, C as shown in FIG. The peaks of the scattered light generated at and D are arranged at approximately equal intervals with respect to the scanning distance r.

In the manner described above, alignment between the alignment mark 52 and the alignment optical system 20 of the reduction projection exposure apparatus 1 can be achieved, that is, alignment between the reticle 9 and the wafer 50 can be achieved.

After the alignment between the reticle 9 and the wafer 50 is completed in this way, the wafer 50 can be subjected to one reduction projection exposure. And/or by providing a plurality of alignment marks 52 between them and repeating the above alignment method for each alignment mark 52, the two-direction moving device 18 can move one wafer 50 in the X direction and the Y direction. It is preferable to sequentially repeat the movement and positioning of the Y stage 11 and the exposure in order to improve productivity.

As described above, according to this embodiment, the laser beam 10G is scanned at the alignment mark 52 so that the spot of the laser beam 10G draws a circular orbit 41, and the scattered light from the alignment mark 52 is detected. Alignment mark 5
2 so that the center position overlaps the center position of the circular orbit 41
- Since the alignment mark 52 is aligned with the alignment optical system 20 by moving the Y stage 11 in the X and Y directions simultaneously, the alignment in the Y direction is performed while the alignment in the No deviation occurs, and the accuracy of alignment can be improved.

Here, using FIG. 6, FIG. 7, FIG. 8, and FIG. A case where the light is incident not perpendicularly to the Y plane (obliquely) will be explained.

FIG. 6(a) shows each of the four step portions 53, 54, 55 and 56 according to the embodiment described above, as well as the step portions provided on the wafer 63 similar to those used for the step portions in conventional alignment marks. A cross-sectional view of one stepped portion 62 constituting the alignment mark is shown. This figure shows a case where the laser beam 60 is perpendicularly incident on the wafer 63. In FIG. 6(b), the intensity P of the scattered light due to the stepped portion 62 is shown with the scanning distance X along the X direction as the horizontal axis.

The intensity P of the scattered light is strongest at the edges 64 and 65 of the stepped portion 62, and scattered light having two peaks is generated at these edges 64 and 65. Therefore, in this case, Figure 6 (
As shown in b), the light scattered by the stepped portion 62 is detected as a signal of intensity P of the scattered light having two peaks that are symmetrical with respect to the center of the stepped portion 62. Therefore, the center line 61 of the stepped portion 62 and the weighted average center position 65 of the detected signal coincide, that is, the X coordinate of the center of the detected scattered light corresponds precisely to the center of the stepped portion 62. Become.

Figure 7 shows a cross-sectional view and the intensity P of scattered light as in Figure 6.
is schematically shown, which shows the case where the laser beam 60 is obliquely incident on the wafer 63. In this case, scattered light having two peaks is generated at the edges 64 and 65, but the intensity of the scattered light due to the edge 64 on the side where the laser beam is inclined is greater than the intensity P of the scattered light due to the edge 65 on the opposite side. It also becomes stronger. Therefore, in this case, as shown in FIG. 7(b), the light scattered by the stepped portion 62 is detected as a signal of intensity P of scattered light having two peaks that are not symmetrical with respect to the center of the stepped portion 62. That will happen. Therefore, the center line 61 of the stepped portion 62 and the weighted average center position 65 of the detected signal are shifted by ΔX.

Therefore, as shown in the plan view in FIG. 8, when using the conventional method of linearly scanning the stepped portions 81 that constitute alignment marks separately in the X direction or the Y direction along the scanning line 80, If this stepped portion 81 is a stepped portion for the X direction, the stepped portion 81 determined by the scattered light will be
The apparent step part +81 indicated by the broken line in the same figure shows
The step portion 81 deviates from its true position in the direction. For this reason,
The center position Ox8 of the alignment mark in the X direction is shown in Fig. 7 (
X of the true alignment mark by △X1 shown in b)
The direction center position will deviate from the O machining. Similarly, the Y-direction center position of the alignment mark also deviates from the true Y-direction center position of the alignment mark along the Y direction. As a result, when aligning separately in the X direction or Y direction as in the past, if the laser beam is incident obliquely,
There is a drawback that the center position of the detected alignment mark deviates from the center position of the true alignment mark.

On the other hand, when using the method of scanning the spot of the laser beam 100 on a circular orbit according to the above-described embodiment as shown in FIG. 9, four portions 53.
The alignment mark 52 consisting of 54, 55 and 56 is
When the laser beam 60 is incident on the wafer 63 obliquely, four apparent portions 153 . t
4 parts 5354.5 like 54.155 and 156
5 and 56 are respectively shifted from their true positions. however,
These deviations are the deviations of the spot of the laser beam 100 along the circular trajectory 41, so the center point 01 of the alignment mark 52, which is determined as the center point of the circular trajectory 41, is the true center point O of the alignment mark 52. will match.

According to this embodiment, even when the laser beam is incident obliquely, the determined center position of the alignment mark is the same as the center position of the alignment mark determined when the laser beam is incident perpendicularly. It has the advantage of being the same. Therefore, in this embodiment, the laser beam may be incident on the wafer vertically or obliquely, and the degree of freedom in designing the reduction projection exposure apparatus 1 can be increased.

[Effects of the Invention] In the positioning method of the reduction projection exposure apparatus of the present invention, the laser beam is applied so that the spot of the laser beam traces a circular orbit on a predetermined portion of the surface to be exposed of the exposed object on which the positioning mark is arranged. The object to be exposed is positioned so that the center position of the alignment mark on the X-Y coordinates, which is determined by scanning the light and detecting the scattered light from the alignment mark, overlaps with the center position of the circular orbit of the laser beam spot. The object to be exposed is aligned with respect to the reduction projection exposure apparatus by simultaneously moving it in the X direction and the Y direction relative to the reduction projection exposure apparatus. Therefore, while positioning in one direction is being performed, there will be no deviation in the already completed positioning in the other direction, and the accuracy of positioning can be improved. Furthermore, since the laser beam is scanned so that the laser beam spot traces a circular orbit, even if the laser beam is incident obliquely, the center position of the determined alignment mark will be determined by the laser beam being perpendicular to the laser beam. The center position of the alignment mark is the same as that determined when the light is incident, that is, the accuracy of alignment can be improved.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing a reduction projection exposure apparatus used in an embodiment of the present invention, FIG. 2 is an enlarged perspective view of a rotor of the reduction projection exposure apparatus shown in FIG. An enlarged perspective view of a wafer alignment mark used in one embodiment;
FIG. 4 is a plan view showing the trajectory of a laser beam spot scanned on an alignment mark in an embodiment of the present invention;
FIG. 5 is a diagram showing a signal when scattered light from an alignment mark is detected by a sensor of a reduction projection exposure apparatus in an embodiment of the present invention, and FIG. A diagram showing the distribution of scattered light when the light is incident and a cross-sectional view of the alignment mark with the X axis aligned. Figure 7 shows the scattered light when the laser beam is incident obliquely on the X-Y plane in the conventional technology. Figure 8 shows the distribution of the alignment mark and a cross-sectional view of the alignment mark with the X-axis aligned. FIG. 9 is a plan view showing the deviation of the alignment mark required when a laser beam is obliquely incident on the X-Y plane in an embodiment of the present invention. 1... Reduction projection exposure device, 2... Mercury lamp, 3... Condensing mirror, 4.7.25.2
7...Reflection mirror, 5.23.26...
Lens, 6...Integrator, 8.22...
...Condenser lens, 9...Reticle,
10...Reducing lens, 1F...X-Y
Stage, 12...Stage target, 18
...Two-direction moving device, 20... Alignment optical system, 21... Laser light source, 24.
...Rotor, 28...CCD area sensor, 50, 63, ...Wafer, 51...
... Upper surface, 52.62, ... Positioning mark, 40141.80, ... Trajectory of laser light spot, 60.70.100 ... Incident laser light. Sat 1 Negative (504) Sharp Law Company

Claims (1)

[Claims] A positioning mark including a stepped portion extending in at least two different directions is arranged along the exposed surface at a predetermined portion of the surface to be exposed of the object to be exposed, and the spot of the laser beam follows a circular orbit in the predetermined portion. The laser beam is scanned in a drawing pattern, the scattered light of the scanned laser beam by the alignment mark is detected, and the detected scattered light is used to determine the direction on the X-Y coordinates along the surface to be exposed. The center position of the alignment mark is determined, and the object to be exposed is placed relative to the reduction projection exposure apparatus so that the center position of the alignment mark thus determined overlaps with the center position of the circular orbit on the XY coordinates. A method for positioning a reduction projection exposure apparatus, characterized in that the object to be exposed is aligned with respect to the reduction projection exposure apparatus by simultaneously moving in the X direction and the Y direction.