JPS60110117A - Thin plate substance providing alignment mark and alignment apparatus using such substance - Google Patents

Abstract

PURPOSE:To improve accuracy of alignment by providing a means for exposing the area of alignment mark to be used when a circuit pattern of reticle is printed to the area on the wafer different from the predetermined position on the occasion of printing a circuit pattern of reticle to the determined position on the wafer. CONSTITUTION:A reticle surface 12 is scanned with a laser 1 through an objective lens 11 in accordance with a rotating polygonal mirror 3. Different from the conventional layout of optical system, the right and left optical systems are formed non-symmetrically, the beam scanning position and observation position on the mask 12 are different each other, and the observation positions are set to the positions 27 and 28. The positions indicated by the alignment marks (x), (w) are scanned by the laser beam. This reticle has a base plate 104 and a pattern forming region and the formed circuit pattern is sequentially printed on the wafer along the columns and rows by the projection optical system. The alignment marks (x), (w) are arranged in both sides of pattern forming area 105 and are not positioned so that these are not arranged in a line along the columns or rows.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thin plate-shaped object equipped with an alignment mark used for positioning and an alignment device using this object, and particularly to an alignment device used for positioning during semiconductor device manufacturing. The present invention relates to a reticle, mask, or wafer provided with marks, and an alignment device using the same.

A typical example of an alignment device used to automatically align a plurality of objects is an aligner, which is a manufacturing device for semiconductor devices such as ICs and LSIs. IC,LS
I is fabricated by laminating many layers of complex circuit patterns. As semiconductor elements f become faster and more dense, the line layers of circuit patterns are becoming increasingly finer, and as a result, high overlay accuracy on the order of submicrons is required.

An example of an aligner that supports such high precision and miniaturization is the Step An Repeater 1 called a stepper.
・Method of aligners can be mentioned. The stepper projects and transfers the pattern on the reticle onto a wafer at reduced or equal magnification. At this time, the exposure area is limited due to constraints on the optical system that performs projection transfer. In order to expose the entire surface of the wafer, the pattern is baked, the wafer is moved in steps, and the pattern is baked in a new area of the wafer, and the process is repeated. . As wafers become larger, the number of steps required increases and processing time increases. On the other hand, in order to sequentially print 4-J patterns using a stepper, the reticle and a predetermined section on the wafer must be aligned relative to each other before printing. The alignment is a very important parameter.

The first method of aligning the reticle with a predetermined section of the wafer is the off-axis method, in which positioning is performed in advance at a location away from the printing position, and then the printing is performed by relying on the accuracy of the laser interferometer. There is a way to do it.

However, although this method is fast, it is difficult to directly check the alignment state at the location where the burnout is performed, and it has to deal with nonlinear physical distortion that occurs on the wafer as it progresses through the process, that is, local expansion and contraction. There are drawbacks such as the fact that the precision of the stage movement monitor becomes a source of error.

・There is a TTL method in which the wafer is observed through a projection optical system at the device or the vicinity of the device where printing is actually performed, and alignment between the reticle and the wafer is performed. When the TTL method is used, it is possible to perform a 1-degree view that is free from the effects of the aforementioned wafer distortion and stage accuracy, so it is expected that the alignment accuracy between the reticle and the wafer will improve.

Regarding the TTL method, a method using laser beam scanning is conventionally known as a known technique.

Japanese Patent Application Laid-Open No. 54-53562 filed by the applicant of the present invention is an example thereof. In Figure 1, which briefly shows an example of this method, light from one laser light source l is transmitted through two objective lenses 11 on the left and right.
The positional deviation between the reticle 12 and the wafer 13 is detected at two locations. Misaligned in 2 places, +71. By detecting the parallel movement (χ.

Two types of misalignment, y) and rotation CO), can be corrected by moving one of the reticle or wafer relative to the other. 3 is a rotating polygon mirror, 4 is an f-theta lens, and 5 is a beam splitter. The light emitted from the laser 1 scans according to the rotation of the rotating polygon mirror 3, and enters the optical system below the beam splitter 5. 6 is a field lens, 25 is a field dividing prism, and the prism 25 divides the scanning laser beam into two optical paths. In this respect, prism 25 can be referred to as a field and space dividing prism. 7 is a polarizing beam splitter, 18 is a relay lens, and 9 is a beam splitter. The light reflected or passed through these elements enters the objective lens 11 and forms an image on the object plane, thereby performing scanning. A pupil imaging lens 14. The system extending from the detector 18 to the detector 18 is a photon detection system. 15 is a color filter, and 16 is a spatial frequency filter, which serves to block specularly reflected light and extract scattered light for light intensity detection. 17 is a condenser lens. Light [19, condenser lens 20, color filter 2
1 constitutes an illumination optical system, and an erector 22 and an eyepiece 23 are used to detect observed light. Configure the system. The operation of this optical system is detailed in Japanese Unexamined Patent Publication No. 854-53562, so a description thereof will be omitted here.

In this example, in order to effectively use the light X, the optical path of the scanning laser beam is split into left and right by a field dividing prism 25 placed on the conjugate plane of the reticle and wafer. The scanning lines are orthogonal to the JAjM of the field splitting prism.

In addition to detecting the optical center, one important function of the microscope system for performing the alignment (alignment I-coup) is the observation function. Especially the match between the reticle and the wafer.
It can be said that the observation function, such as monitoring the i and checking the initial settings of the reticle, is an indispensable element for an alignment scope.

What is desirable about an alignment scope as an observation optical system is that the observable image can be seen in a natural and easy-to-see form.
Figure 2 shows the relationship between the image fields observed. In the figure, 31 is the visual field dividing line L, the ridge line 25,
32 is a scanning line of the laser beam, 33 is a field of view corresponding to the right objective lens, and 34 is a field of view corresponding to the left objective lens. In fact, the scanning laser beam scans the object plane in the lateral direction at the positions where the seven alignment marks of the reticle and wafer are placed.

Alignment marks are useful in the process of manufacturing semiconductor devices, but they do not perform actual circuit functions as actual semiconductor devices. At the end of wafer processing, the alignment mark becomes a put space. Therefore, it is desirable that the area occupied by the alignment mark be as small as possible in order to increase the yield of actual devices. - wIJ3 When there is a reticle 12 (or mask) as shown in the figure, align the alignment mark with the scribe line lO3 between each chip 101.
This problem is solved by storing the alignment mark inside the alignment mark itself, which eliminates the dead space caused by the alignment mark itself. In this case, since the alignment scope scans in the lateral direction, the alignment mark may be housed within the lateral risk drive line 103 close to the center line of the reticle.

However, especially in the case of a miniature stepper, there are cases where the entire reticle corresponds to one chip and scribe lines exist only at the periphery. Figure 4 shows reticle 1.
The diagonal line in Figure 6, which shows an example of the case where there is no 1 chip in 2, is alignment mark 1.
This is the 02 part. As can be easily understood from FIG. 4, the pair of alignment marks 102 are arranged in the same position line at a position far away from the center line of the reticle 12. The accuracy of alignment in this area is poorer than in the vicinity of the area where the alignment mark is installed.

The deterioration in alignment accuracy caused by the juxtaposition of the same Clive line 103J near alignment marks 102 that are far from the center line of the reticle 12 is caused by
This is noticeable when the number of chips 101 on the top is one as described above. Also, compared to the case where there is an even number, the case where there is an odd number is because there is no scribe line at the center of the screen.

Furthermore, if the alignment I marks are provided at the same location on opposite peripheries of the pattern area of the reticle and at the same location on the opposite periphery of the pattern area printed in one shot onto the wafer. In this case, when performing the 7-line I in the next shot after completing the burnout and stepping, the alignment mark used in the previous shot will overlap with the alignment mark used in the current shot. A situation arises in which it does not actually function as a 7 line mark for the next shot.

The object of the present invention is to eliminate non-uniformity in alignment accuracy caused by the position of alignment marks, and to provide reticles, masks, wafers, etc. with improved alignment mark placement that can measure the direction of alignment accuracy. The object of the present invention is to provide a thin plate-like object.

An object of the present invention is to provide a thin plate-like object such as a reticle, a mask, or a sea urchin having an improved alignment mark arrangement that can prevent alignment marks from overlapping during alignment at each step. It's about doing.

Yet another object of the present invention is to provide an alignment device in which the scanning positions on the surface of a thin plate-like object are staggered.

By the way, it is not possible to print the pattern on the reticle onto the wafer.
When baking, the alignment marks on the reticle will also be transferred onto the wafer.
When processing such as development and diffusion is performed on the wafer that has completed the first stage,
The alignment marks of the reticle transferred to the wafer leave traces on the wafer (USP
, 3844655). Such marks on the wafer can be removed by changing the 7 alignment mark on the wafer to the 7 alignment mark on the reticle in order to print a new pattern on the same tool.
This becomes an obstacle when aligning with the alignment mark.

Another object of the present invention is to provide a reticle that can prevent traces from being left on the wafer due to alignment marks of the reticle transferred onto the wafer.

Still another object of the present invention is to provide a step-and-repeat type aligner with means for preventing marks on the reticle from leaving marks on the reticle after it has been transferred to the wafer. There is a particular thing.

Embodiments of the present invention will be described below with reference to the drawings.

Referring to FIG. 5, there is shown a preferred embodiment of an alignment apparatus according to the present invention in which a reticle constructed according to the present invention is used. The system of FIG. 5 is a variation of the system of FIG. 1, and identical parts have been given the same reference numerals. That is, there is no change in the fact that the light emitted from the laser l scans the reticle surface 12 through the objective lens II as the rotating polygon mirror 3 rotates. The arrangement of the optical system shown in FIG. 5 is different from the arrangement of the optical system shown in FIG. This is after it has been divided into left and right.

That is, the left and right optical systems are configured asymmetrically, and the mask 12J
The beam scanning position and observation position of , are staggered. In other words, the observed position in the system of Figure 5 is the 6th position.
These are the locations shown at positions 27 and 28 in the figure. The areas scanned by the laser beam are the alignment marks X and W shaded in the figure. That is, the mark can be placed within the scribe line 106. This method has a long span connecting observation points, so it is characterized in that it can best suppress errors in rotational components.

Thus, the optical system of the alignment device according to the invention shown in FIG. ! The staggered configuration shows that a reticle constructed in accordance with the present invention can be used by modifying the conventional optical system shown in Figure wS1. The reticle constructed according to the present invention shown in FIG. 6 has a base plate 104 and a pattern forming section 105. The circuit pattern formed in the pattern forming section 105 is sequentially printed on the wafer along columns and rows by a projection optical system. The alignment marks X and W are arranged to sandwich the pattern forming portion 105, and are positioned in an alternating relationship so as not to be aligned in a straight line along the aforementioned column or row direction.

Figures 7 and 8 show the scribe line lO9 on the wafer.
This is an example in which alignment marks are arranged. 7th
In both figures, the reticle 12 is composed of one chip, which is printed onto the wafer 13 in a step-and-repeat manner. The alignment mark is located within the scribe line 107, which is the boundary between the individual real elements, but the arrangement method is different between FIG. 7 and FIG. 8. As is clear from the example of FIG. 6, the seven alignment marks of the reticle used in this embodiment are a pair of alignment marks x and W arranged at the upper right and lower left. In the wafer 13 shown in FIG. 7, adjacent chips share a scribe line 107.

That is, 3OA, 30B, 30 around the chip 3o
When paying attention to the four marks C and 30D, chip 3
The mark used for the alignment of the o mark is 3.
0B (X) and 30C (W) - 1'A6, 30Aji The upper chip 29 burnt is a mark for the 7th line of time, and 30D is the lower chip 31 burnt is a mark for the 7th line of time. It has become.

On the other hand, FIG. 8 shows an embodiment in which the inside of the scribe line 107 is further divided into two, and the alignment marks are placed adjacent to the corresponding individual chips. It is convenient if you divide the scribe line into two and use the scribe line area on one side, because you can use the scribe line area on the opposite side when performing a new 7 alignment. Another advantage of the method shown in FIG. 7 is that the width of the scribe line 107 can be narrower. In recent years, the width of scribe lines has tended to become narrower and narrower, and in that case, the method shown in Figure i7 can be said to be more advantageous.

Although the case in which the alignment marks are arranged within the scribe line in the horizontal direction has been described above, the staggered arrangement of the marks is also effective when the marks are arranged within the scribe line in the vertical direction.

An example of this is shown in FIG. 9. In FIG. 9(a), a reticle 12 on which four chips A, B, C, and D are formed for the purpose of FIG. 9(b) is transferred to a wafer using a step-and-repeat method. Reticle 12 is formed with a pair of alignment marks P, Q, which are arranged in a staggered relationship on opposite sides of the chip area of the reticle.

The alignment marks of the reticle 12 may be provided at the lower left P° and the upper right Q° of the reticle as explained in FIG.
The case where it is installed in the position will be explained.

The state in which the alignment marks P and Q of the reticle 12 are printed on the wafer 13 by the step-and-repeat method is as shown in FIG. 9(a). Also, this figure 9 (a
) indicates the position of the 7 alignment marks on the wafer 13. That is, in shot 40, chip 40. A,
When 40B, 40C, and 400 are printed, a pair of alignment marks P are formed on the reticle.
The 7 alignment mark on the wafer corresponding to Q is 40F,
40Q, and the wafer alignment marks corresponding to the reticle alignment marks P and Q at the next step 41 are 41P and 4IQ.

Here, the wafer's 7 alignment marks 40Q, 4IP,
Since they are not at the same position, it is possible to avoid a situation where the alignment mark for the sea urchin overlaps the 7-line I mark image on the reticle in one shot and cannot function as the 7-line I mark in the next shot. Note that chips with the same number in FIG. 9 indicate that they were printed with the same shot.

FIG. 1θ shows an embodiment of the alignment device according to the present invention of the type that scans a laser beam in the vertical direction. Here, a combination of mirrors 9 and 9a is used to scan the laser in the vertical direction. As in the embodiment shown in FIG. 5, the left and right scanning optical systems are constructed asymmetrically, so the left and right objective lenses
are positioned alternately corresponding to the positions of the 7 alignment marks in FIG. In the step-and-beat method, the projection optical system is used to print each shot and then the steps are repeated to move on to the next shot, so the connection between each shot becomes a major problem.

In the alignment apparatus shown in FIG. 1θ, a wafer 13 is positioned in the X and Y directions by an x-step device and a Y-step device to form chips and rows on the wafer while being supported by a wafer carrier 110. will be stepped.

Note that the seven alignments between the reticle 12 and the wafer 13 in each step (shot) are X, Y, and Y for moving the reticle holder 111 for holding the reticle.
This is done in the θ drive.

As mentioned above, alternating P and Q in Figure 9 means that when stepping to the next shot, the image of P and Q will not overlap with the 7 alignment mark on the wafer in the next shot. The car is secure.

In order to place marks more efficiently, considering the situation shown in Figure 9(a), print P and Q so that the images do not overlap with the alignment marks on the wafer in the next shot. It is necessary to determine the positional relationship between

In the case of the reticles shown in FIGS. 6 and 9(b), the alignment marks are pattern 2.2 on the reticle. They are placed in contact with the opposing perimeter of the castle, but if the number of chips is large and there are several scribe lines in the vertical or horizontal direction, the scribe lines may be placed in two different positions. .

Now, examples of the shape of the above-mentioned alignment mark include, for example, a conventionally known mark, ie, the one shown in FIG. In the figure, 51 is a mark on the reticle, 52 indicated by a dotted line is a mark on the wafer, and 53 is a scanning line. Since it is a TTL method, the mark on the reticle and the mark on the wafer are simultaneously detected through the reticle, and based on the signals, a drive system (not shown) performs 7-alignment of both. By the way, when marks are arranged as shown in Figure 9, if P and Q are marks of the same shape, there is a possibility that the positions of P and Q may be confused when a shift occurs due to an error in the rotation of the reticle or wafer. . In that case, position confusion can be avoided by making P and Q marks, for example, in opposite directions. FIG. 12 shows an example of applying such a method to a reticle, in which the directions of marks P and Q are reversed. Corresponding alignment marks on the same scribe line on the wafer are constructed as shown in FIG. That is, P and Q
Since the directions are different, it is impossible to confuse the two.

As described above, the alignment mark arrangement according to the present invention can reliably improve the alignment accuracy between a reticle or mask and a wafer.

Furthermore, it is also significant in that it is possible to prevent overlapping of alignment marks during alignment in each step. Further, since the scanning optical system of the alignment device according to the present invention is asymmetrically configured, it can sufficiently cope with improved alignment mark placement.

By the way, when the pattern on the reticle is printed onto the wafer, the 7 alignment marks on the reticle are also transferred onto the wafer [2] at the same time. In this state, an unexposed portion corresponding to the shape of the seven alignment marks on the reticle remains within the IK region of the alignment mark on the wafer. Therefore, when a wafer that has been baked in this state F; is subjected to processing such as development and diffusion, the wafer is To 1-; a good road remains.

Such marks on the wafer impair the function of alignment marks on the wafer when a new pattern is printed on the same wafer L, making it impossible to align the reticle and the wafer.

According to one advantageous aspect of the present invention, the above-mentioned problems are conveniently solved. In the reticle according to the present invention shown in FIG. 12, light transmitting portions R and S are formed adjacent to alignment marks P and Q arranged at different positions across a pattern forming portion 113. There is. This light transmitting portion R,
According to the arrangement of S, the unexposed portion of the reticle by the alignment mark Q transferred onto the 7 alignment marks Q on the wafer in shot 40 is simultaneously exposed by the light transmitted through the light transmitting portion R when exposed in shot 41. It is exposed to light (see Figure 9).

Therefore, it is possible to prevent the occurrence of a situation where traces remain on the wafer due to the unexposed portions corresponding to the alignment marks of the reticle.

The reticle according to the present invention shown in FIG. 4 has a light transmitting portion Y at a position corresponding to the alignment mark arrangement shown in FIG.
, Z are formed. According to the arrangement of the light transmitting portions Y and Z, the unexposed portion due to the alignment mark W of the reticle transferred onto the 7 alignment mark 109G on the wafer in shot 109 will pass through the light transmitting portion Z when exposed in shot 108. It is exposed by the transmitted light.

As mentioned above, according to the present invention, in each shot, L't%
Since the alignment mark area used in the adjacent shot can also be exposed to light, protection of the alignment mark can be achieved without a separate special exposure process.

In particular, in steppers where alignment accuracy is strictly required, the same 7 alignment marks can be used at all times, making it difficult for errors to occur because there is only one standard.
Eliminates the need to provide multiple pairs of alignment marks, etc.
There are many benefits.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the optical system of a conventional alignment device, Fig. 2 is a diagram showing the relationship between the scanning beam and the field of view, and Fig. 3 is a diagram showing a mask or reticle on which a plurality of chips are formed on the surface. . FIG. 4 is a diagram showing the arrangement of conventional alignment marks in the case of an l-chip reticle. FIG. 5 is an optical system layout diagram of an alignment device in which a reticle constructed according to the present invention is used; FIG. 6 is a diagram showing a reticle with alignment marks arranged according to the present invention; FIGS. 7 and 8; Figures 9(a) and 9(b) show the alignment marks on the wafer when using the reticle shown in tJ and Figure 5, respectively, and Figures 9(a) and (b) show alignment marks arranged according to the vertical scribe line area of the wafer and reticle, respectively. Figure 1θ is a diagram showing the optical system layout of the alignment device using the alignment marks in Figure 9, Figure 11 is a diagram showing the relationship between the alignment marks on the reticle and wafer, and the scanning line, and Figure 12 is Figure 13 shows the alignment marks and light-transmitting parts on the reticle. Figure 13 shows the 7 alignment marks on the wafer's scribe line. Figure i14 shows the light-transmitting parts corresponding to the alignment mark arrangement shown in Figure 8. FIG. 3 is a diagram showing a reticle having a 11 Momme I week alignment mark: P, Q, X, Y Light transmission part: R
,S 6th layer ldo/7th Fig. 8 Fig. 14 area

Claims (2)

[Claims] (1) A step configured to sequentially project the circuit pattern of the reticle 1- onto the wafer 1- by a projection optical system, and print a plurality of the circuit patterns on the urchin/\- along columns and rows. A reticle for use with and repeat type 7-liner, base play 1.
and a circuit pattern formed on the pattern forming part of the base plate, and a pair arranged so as to sandwich the pattern forming part and positioned so as not to be aligned in a straight line along the direction of the column or row. Alignment mark and area of alignment mark used when printing the circuit pattern of the reticle at a position different from the predetermined position when printing the circuit pattern of the reticle at a predetermined position on the wafer. A reticle consisting of a means for exposing light. (2) a reticle holder for holding a reticle having a circuit pattern and an alignment mark arranged in a predetermined positional relationship with respect to the circuit pattern;
a projection optical system for projecting an image of the reticle, a universal carrier for holding a wafer positioned on a surface on which the reticle image is formed, and a reticle for sequentially forming the reticle image on the wafer. stepping means for intermittently changing the relative position of the image and the wafer; stepping means for intermittently changing the relative position of the image of the reticle on the wafer; Step-and-repeat aligner-0 characterized by having a lower stage that exposes a portion on which an alignment mark is projected.