JP3286124B2 - Alignment apparatus and method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alignment apparatus and method for sequentially aligning a plurality of regions on a substrate at desired positions, and more particularly, to a step-and-repeat type exposure apparatus for manufacturing semiconductors. The position or position error related to the above several shot areas is measured, the shot arrangement of each shot area on the wafer is determined from these, and the determined shot arrangement is used to position the shot on the wafer at a position related to the reticle. And an alignment apparatus for sequentially aligning the shot areas.

[0002]

2. Description of the Related Art In a step-and-repeat type exposure apparatus for manufacturing a semiconductor, a so-called stepper, a position or position error relating to several shot areas on a semiconductor wafer is measured, and each shot area on the wafer is measured from these. A technique for determining a shot arrangement and sequentially aligning each shot area on a wafer at a position related to a reticle using the determined shot arrangement is disclosed in, for example, Japanese Patent Application Laid-Open No. 63-232321.

In such an alignment technique, conventionally, the exposure size that can be exposed at one time is smaller than the size of the substrate, so that the number of shots that can be arranged on one substrate can be sufficiently ensured. Therefore, in order to maintain a certain precision, it is easy to secure a certain number of shots to be measured, and it is also possible to select a measurement area without bias.

[0004]

However, in recent years, it has been studied to increase the exposure size and reduce the number of shots in order to increase the throughput, and the number of shots on the substrate is inevitably reduced. . For this reason, it is difficult to secure the number of measurement areas required for alignment measurement, and the measurement areas are also biased.

SUMMARY OF THE INVENTION An object of the present invention is to provide a positioning apparatus or method which can always perform high-precision alignment even when the number of entire regions to be aligned is small. Is to do.

[0006]

According to the present invention, in order to achieve the above object, each area has a plurality of marks which have a fixed positional relationship with the area and respectively correspond to a plurality of alignment directions of the area. Asymmetrically attached regions
Selecting some of the plurality of regions on the substrate formed according to predetermined array position data defining their array position, positioning each selected region sequentially at a predetermined position according to the array position data, By detecting the position of the mark, corrected position data in the respective alignment directions with respect to the array position data is obtained, and the plurality of regions are sequentially aligned to a desired position based on the corrected position data and the array position data. In the apparatus or the method, the area is selected independently for each of the alignment directions to obtain the corrected position data.

[0007]

Conventionally, only one area is selected, and a mark whose position is detected is a mark in each alignment direction attached to each selected area, and a mark of each selected area is asymmetrically attached. Therefore, if the area to be aligned is small, select an area so that a mark at a position suitable for one of the alignment directions can be detected. There are inconveniences such that only a mark at a biased and inappropriate position can be used, or a mark in such a region cannot be used when a part of the region may be missing. However, in the present invention, since the region is selected independently for each alignment direction, for the other alignment direction,
The area is selected so that marks with a distribution suitable for alignment in that direction can be used.

[0008]

FIG. 1 is a block diagram schematically showing a main part of an exposure apparatus to which an alignment apparatus according to one embodiment of the present invention is applied. In FIG. 1, reference numeral 1 denotes a projection optical system that projects a pattern on a reticle R onto a wafer W. 2 is a positioning illuminator for illuminating the alignment mark M on the wafer W via the reticle R and the projection optical system 1, 3 is a beam beam splitter disposed between the illuminator 2 and the reticle R, Reference numeral 4 denotes an image forming optical system that receives light from the mark M reflected by the beam splitter 3 and forms an image of the mark M. These components constitute a positioning optical system S. An imaging device 5 captures an image formed by the imaging optical system 4, an A / D conversion device 6 that A / D converts an image signal from the imaging device 5, and a reference numeral 7 from the A / D conversion device 6. An integrating device 8 integrates a two-dimensional image signal and converts it into a one-dimensional digital signal. An integrating device 8 detects the position of the mark M by pattern matching between the one-dimensional digital signal from the integrating device 7 and a template pattern stored in advance. A XY stage 11 for holding a wafer W;
0 is a stage driving device for driving the XY stage, 13 is a feature amount extracting device, 9 is a CPU for controlling the stage driving device 10, the position detecting device 8, the feature amount extracting device 13 and the like, 12
Is a storage device connected to the CPU 9.

On the wafer W, as shown in FIG. 2, each shot position has a plurality of marks (M1x) having a fixed positional relationship with the shot position and corresponding to the alignment directions X and Y of the area. , M1y) are preliminarily formed by the main exposure apparatus in accordance with predetermined arrangement position data defining the arrangement positions of the shot areas S1, S2, S3,...

In this configuration, when the wafer W is placed on the XY stage 11 by a wafer transfer device (not shown),
The CPU 9 controls the stage driving device 10 so that the alignment mark M1x formed on the first measurement shot S1 shown in FIG.
, And drives the XY stage 11. Here, positioning illumination means 2 for irradiating non-exposure light
The radiated light beam passes through the beam splitter 3, the reticle R, and the projection optical system 1, and passes through the alignment mark M1.
Illuminate x. The light beam reflected from the wafer mark M1x reaches the beam splitter 3 again via the projection optical system 1 and the reticle R, is reflected there, and is reflected on the imaging surface of the imaging device 5 via the imaging optical system 4. Wafer mark M1x
Is formed.

The image of the mark M1x is photoelectrically converted in the image pickup device 5, and is converted into a two-dimensional digital signal sequence in the A / D converter 6. The integrator 7 sets a processing window Wp for the wafer mark image WM digitized by the A / D converter 6 and performs a moving average process in the y direction in the window to convert the two-dimensional image signal into one. It is converted into a dimensional digital signal sequence S (x).

The position detector 8 performs pattern matching on the one-dimensional digital signal sequence S (x) output from the accumulator 7, and determines the address position of S (x) having the highest degree of matching with the template pattern. Is output to the CPU 9. Since this output signal is a mark position based on the imaging surface of the imaging device 5, the CPU 9 determines whether the imaging device 5 and the reticle R are determined in advance by a method (not shown).
Relative to the reticle R of the wafer mark M1x
Is obtained by calculation. This gives 1
This means that the displacement amount in the x direction of the second measurement shot has been measured.

Next, the CPU 9 drives the XY stage 11 so that the y-direction measurement mark M1y of the first measurement shot falls within the field of view of the y-direction positioning optical system. Here, the displacement amount in the y direction is measured in the same procedure as in the x direction.

Thus, the measurement in the first measurement shot S1 has been completed. Next, the CPU 9 moves the XY stage 11 so that the x-direction measurement mark M2x of the second measurement shot S2 falls within the field of view of the positioning optical system, and moves in the x and y directions in the same procedure as the first. Measure the amount of deviation.

Hereinafter, similarly to S1, S2, S3, S4,
As in S24, the displacements in the x and y directions of the measurement shots formed on the wafer W are measured. The shots shown here may be all shots on the wafer W1, or may be performed only with shots designated in advance.

As shown in FIG. 2, when a large number of shots are present on the wafer, each of the X and Y marks can be measured in most of the measurement shots. A sufficient number of measurement shots can be secured for alignment.

However, when the angle of view increases and the number of shots formed on the wafer decreases, the number of shots that can measure both X and Y marks inevitably decreases, and the shots are not uniformly arranged on the wafer. This is disadvantageous in terms of alignment accuracy.

In view of the above, a measurement shot which conventionally required measurement of marks in both X and Y directions has been separated into a shot for measuring an X mark and a shot for measuring a Y mark. By providing the function, the above-described problem can be solved.
The example is shown in FIG. 3 and FIG.

FIG. 3 shows an example in which a shot using only the X mark for alignment is selected, and FIG. 4 shows an example in which a shot using only the Y mark for alignment is selected. In these figures, 410 is a wafer, 420 is a shot area formed by a low magnification stepper, 430 is a shot area formed by a high magnification stepper, 450 is a virtual circle, 460 is a mark used for X-direction alignment, 47
0 is a mark used for Y-direction alignment. FIG.
In each of FIGS. 4A and 4B, each mark is distributed to some extent uniformly on the wafer. However, considering that the Y mark in FIG. 3 and the X mark in FIG. This not only reduces the number of measurements, but also makes it impossible to distribute the marks uniformly.

Here, the concept of independently selecting the shot for measuring the X or Y mark for each of the X and Y marks will be described. It is generally considered that the exposure accuracy in a certain shot arrangement can be expressed by Expression 1.

[0021]

(Equation 1) However, if we consider this independently in the X and Y directions,
Equation 2 can be defined.

[0022]

(Equation 2) Therefore, the exposure accuracy 3σ exp can be expressed by Expression 3.

[0023]

(Equation 3) This equation shows that the shot array evaluation value obtained from the X mark measurement shot and the X mark correction value are obtained, and the Y correction value is obtained from the shot array evaluation value obtained from the Y mark measurement shot and the Y measurement value. ing. Thus, X,
It can be seen that the conventional correction method may be applied to each of X and Y even when the Y mark is measured independently. In other words, a measurement shot for detecting only the X mark (shaded area in FIG. 3) is selected in the same manner as in the prior art to determine a correction value in the X direction, and a measurement shot for detecting only the Y mark (shaded area in FIG. 4) is selected. What is necessary is just to select in the same way as before and determine the correction value in the Y direction.

According to this concept, since a plurality of alignment marks can exist or be provided in one shot, attention is paid only to the position of the alignment mark without depending on the shot. By selecting a mark, it is also possible to independently select X and Y alignment marks having a more uniform distribution.

[0025]

According to the present invention, high-precision alignment can always be performed even when the number of alignment-symmetric regions is small, for example, when aligning a wafer having a small number of shots.

[Brief description of the drawings]

FIG. 1 is a block diagram schematically showing a main part of an exposure apparatus to which an alignment apparatus according to one embodiment of the present invention is applied.

FIG. 2 is a plan view showing sample positions measured by the apparatus of FIG.

FIG. 3 is a plan view showing sample positions for measuring alignment marks in the X direction when the number of shots is small by the apparatus of FIG. 1;

FIG. 4 is a plan view showing sample positions for measuring alignment marks in the Y direction when the number of shots is small by the apparatus of FIG. 1;

[Explanation of symbols]

1: Projection optical system, 2: Positioning illumination device, 3: Beam splitter, 4: Imaging optical system, 5: Imaging device, 6: A /
D conversion device, 7: integration device, 8: position detection device, 9: C
PU, 10: Stage drive, 11: XY stage,
12: Storage device.

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 21/027 G03F 9/00

Claims (2)

(57) [Claims] 1. A plurality of regions each having a fixed positional relationship with the region and asymmetrically accompanied by a plurality of marks respectively corresponding to a plurality of alignment directions of the region.
Means for driving a substrate formed in accordance with predetermined array position data defining those array positions; means for detecting the position of the mark; selecting some of the plurality of regions; and selecting each selected region The drive unit sequentially positions the mark at a predetermined position in accordance with the arrangement position data, and the position of the mark is detected by the detection unit to obtain corrected position data in the respective alignment directions with respect to the arrangement position data. A control unit for sequentially positioning the plurality of regions at desired positions by the driving unit based on the position data and the array position data, wherein the control unit is separately provided for each of the alignment directions. An alignment apparatus, wherein the correction position data is obtained by independently selecting the area. 2. A plurality of regions each having a fixed positional relationship with the region and asymmetrically associated with a plurality of marks respectively corresponding to a plurality of alignment directions of the region.
Selecting some of the plurality of regions on the substrate formed according to predetermined array position data defining their array position, positioning each selected region sequentially at a predetermined position according to the array position data, By detecting the position of the mark, corrected position data in the respective alignment directions with respect to the array position data is obtained, and the plurality of regions are sequentially aligned to a desired position based on the corrected position data and the array position data. The method according to claim 1, wherein the correction position data is obtained by selecting the area independently for each of the alignment directions.