JPH0362013B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an alignment device, for example, when printing a mask pattern on a wafer in a semiconductor printing device, etc. The present invention relates to an alignment method that performs highly accurate alignment by efficiently and accurately measuring intervals.

[Conventional technology]

This alignment between the mask and the wafer is achieved by, for example, scanning alignment marks for automatic alignment drawn in advance on each of the mask and wafer with a laser beam, and using scattered diffraction light from the mark edges as alignment information. . In this case, after optically removing the directly reflected light in the light receiving section, the intensity of the scattered and diffracted light from the edge of each alignment mark is photoelectrically converted into an electrical pulse, and this pulse position is determined by a clock counter. Generally, the distance between the alignment marks, that is, the deviation, is determined by measuring the distance between the alignment marks.

Specifically, using an alignment mark M as shown in FIG. 1a as a mask, a mark W as shown in FIG.
is drawn on the wafer, the alignment marks M and W on the mask 1 and the wafer 2 are scanned with a laser beam L using a device configured as shown in FIG. 2, and the deviation of each mark is determined. Mask 1 according to
Or move either of the wafers 2 and
The mask 1 and the wafer 2 are relatively aligned in the state shown in FIG.

FIG. 2 shows an example of an alignment system in a semiconductor printing apparatus. In the figure, 1 is a mask, 2 is a wafer, 3 is a moving stage, and 4 is a projection lens for transferring the pattern of the mask 1 onto the wafer 2. Further, 7 is a polygon mirror rotated by a motor 6, and the laser light emitted from a laser light source, for example, a laser tube 5, passes through a polygon mirror 7, a mirror 8, a beam splitter 11, an objective lens 10, and a mirror 9, and then passes through a mask. The alignment marks M and W on the wafer 1 and the wafer 2 are scanned. Scattered light from the alignment marks M and W passes through a mirror 9, an objective lens 10, and a beam splitter 11, and enters a photoelectric detector 12.

The output signal of the photoelectric detector 12 is an analog signal as shown in FIG. This is a signal caused by scattered light. These signals are binarized by the comparator 14 in the control circuit 13 and become a pulse train as shown in FIG. 1(f). These pulse intervals are measured by a measurement clock oscillator 15 and a pulse interval measurement counter 16. 17 is the CPU and the counter 1
6 is read out, and from this value, the relative displacement amount between the mask 1 and the wafer 2 is determined, and the motors 15 and 1 are operated so that the mask and the wafer are in the correct positional relationship.
6 to drive the moving stage 13.

At this time, the frequency of the measurement clock generally corresponds to the scanning speed of the laser beam on the wafer surface; for example, one cycle of the clock is set to be the same as the time it takes for the laser beam to scan the wafer surface by 0.1 μm. .

At this time, the resolution for measuring the amount of misalignment between the wafer and the mask is 0.1 μm. However, in reality, an error occurs between the speed of the laser beam actually scanning over the wafer surface and the measurement clock due to an error in the magnification of the optical system in the optical path of the laser beam, such as the objective lens 10, etc.

This error becomes an error in directly measuring the amount of deviation between the mask and the wafer, and reduces the accuracy of alignment between the mask and the wafer.

Therefore, conventional methods have been to measure this error when assembling the equipment, enter the value for each equipment, and use software to correct the error when calculating the amount of misalignment between the wafer and the mask. I was getting used to it.

[Problem to be solved by the invention]

However, this method requires complex and precise adjustment and measurement processes when assembling and adjusting the device, and for some reason, the optical system (e.g. lens) of the device must be replaced or readjusted after completion. In this case, there was a problem in that a process for measuring and inputting the magnification error was always required.

The present invention has been made in view of the problems in the conventional example described above, and provides an alignment method that eliminates the need for precise and complicated measurement steps for magnification errors during assembly and adjustment, and that can also cope with changes in time measurement. The purpose is to provide.

[Means to solve the problem]

In order to achieve this object, the present invention photoelectrically detects a first mark formed on a first object and a second mark formed on a second object through an objective lens using a photoelectric detector. , based on the interval between the first mark signal corresponding to the first mark from the photoelectric detector and the second mark signal corresponding to the second mark.
and the second mark, and relatively move the first and second objects using the moving stage according to the deviation data.
In an alignment method for adjusting the relative positional relationship of objects, a projection lens provided integrally with the lens barrel of a projection lens disposed between the first and second objects;
Alternatively, a reference mark with known dimensions formed on a reference plate on a moving stage is photoelectrically detected by a photoelectric detector through an objective lens, and a reference is determined from a reference mark signal corresponding to the reference mark from the photoelectric detector. The first and second When adjusting the relative positional relationship between the first and second objects by photoelectrically detecting two marks with a photoelectric detector, the first and second marks are adjusted according to the displacement data corrected by the magnification error using the magnification error data. Two objects are moving relative to each other.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. Note that parts common to or corresponding to those of the conventional example are indicated by the same reference numerals.

FIG. 3 shows a schematic configuration of an alignment device according to an embodiment of the present invention. The device shown in the same figure is different from the one shown in FIG. 2 by attaching a glass plate 18 with a reference mark engraved thereon as shown in FIG. The marks on the glass plate 18 can be observed from above the reticle 1 through this transparent portion a. Also, mirror 9
can be moved to any desired position on the reticle 1 by a motor (not shown).

Next, the operation of the alignment device configured in this manner will be explained.

Prior to aligning the reticle 1 and the wafer 2, the control circuit 13 first moves the mirror 9 above the transparent portion a of the reticle 1. In this state, the polygon mirror 7 is rotated to scan the reference mark on the glass plate 18 with a laser beam, and the dimension of the portion c in FIG. 4 is measured using the mark on the glass plate 18. b in FIG. 4 indicates the scanning direction of the laser beam. The dimensions of this reference mark shall be measured at the time of equipment delivery, periodic inspection, or as needed. Alternatively, the process may be performed each time the device is started.

Assuming that the dimension measured in the above manner is, for example, c', the magnification error of this optical system is found to be c/c'.

The control circuit 13 stores this value in the memory of the CPU 17, and thereafter observes it by multiplying the position measurement data of the alignment marks on the wafer 2 and reticle 1 by c/c' when aligning the wafer 2 and reticle 1. The magnification error of the optical system can be automatically corrected.

[Modified example]

In the above embodiment, a mark on the glass plate provided on the side of the lens barrel is used to measure the magnification, but this may also be used, for example, as a mark for aligning the reticle to a predetermined position on the lens. You can also do this. Alternatively, a mark provided on a glass wafer or the like with little dimensional change (clearly within an allowable range) may be used as the reference mark. In the latter case, the magnification of the optical system including the projection lens can be comprehensively corrected. However, in this case, the operator sets the reference wafer in the apparatus and supports it in order to perform magnification measurement, and the apparatus is provided separately from the one for aligning the mask and wafer for this magnification measurement. A special sequence needs to be activated.

〔Effect of the invention〕

Therefore, according to the present invention, precise and complicated measurements of magnification are not required when assembling and adjusting the device, and even if the observation (optical) system is replaced midway through, the magnification error as described above can be measured in advance. If you enter the information manually, you can eliminate the need for the previous steps.

[Brief explanation of drawings]

FIG. 1 is a diagram illustrating alignment marks on masks and wafers, FIG. 2 is a schematic configuration diagram of a conventional alignment device applied to a semiconductor printing device, and FIG.
The figure is a schematic configuration diagram of an alignment device according to the present invention applied to a semiconductor printing apparatus, and FIG. 4 is a diagram showing an example of a reference mark for magnification correction of the present invention. In the figure, 1 is a mask, 2 is a wafer, 3 is a moving stage, 4 is a projection lens, 5 is a laser light source, 6 is a motor, 7 is a polygon mirror, 8 and 9 are mirrors, 1
0 is the objective lens, 11 is the beam splitter, 12
13 is a photoelectric detector, 13 is a control circuit, 15 and 16 are motors, 17 is a CPU, and 18 is a glass plate with marks for measuring magnification.

Claims (1)

[Scope of Claims] 1. A first mark formed on a first object and a second mark formed on a second object are photoelectrically detected through an objective lens by a photoelectric detector, and the photoelectric detector Calculate deviation data between the first and second marks based on an interval between a first mark signal corresponding to the first mark and a second mark signal corresponding to the second mark, and calculate the deviation data based on the deviation data. In the positioning method, the relative positional relationship between the first and second objects is adjusted by relatively moving the first and second objects using a moving stage according to the positioning method. A reference mark of known dimensions that is integrally provided with respect to the lens barrel of a projection lens disposed in is photoelectrically detected by the photoelectric detector through the objective lens, and the reference mark from the photoelectric detector is detected by the photoelectric detector. Determine magnification error data corresponding to the magnification error of the observation system including the objective lens using the measured dimension of the reference mark obtained from the reference mark signal corresponding to the reference mark and the actual dimension of the reference mark, and determine the magnification error data according to the magnification error of the observation system including the objective lens. By storing in the memory, when adjusting the relative positional relationship between the first and second objects by photoelectrically detecting the first and second marks with the photoelectric detector, the magnification error data is stored in the memory. An alignment method characterized in that the first and second objects are relatively moved in accordance with the displacement data corrected by the magnification error using . 2. A first mark formed on a first object and a second mark formed on a second object are photoelectrically detected by a photoelectric detector through an objective lens, and the first mark from the photoelectric detector is detected. The deviation data between the first and second marks is calculated based on the interval between the first mark signal corresponding to the second mark and the second mark signal corresponding to the second mark, and the deviation data between the first and second marks is calculated according to the deviation data. In the positioning method of adjusting the relative positional relationship between the first and second objects by relatively moving the second object using a moving stage, the dimensions formed on the reference plate on the stage are known. The reference mark is photoelectrically detected by the photoelectric detector through the objective lens, and the measured dimension of the reference mark and the actual value of the reference mark are determined from a reference mark signal corresponding to the reference mark from the photoelectric detector. By determining magnification error data according to the magnification error of the observation system including the objective lens using the dimensions and storing the magnification error data in a memory, the first and second marks are detected by the photoelectric detection. When adjusting the relative positional relationship between the first and second objects by photoelectric detection with a device, the first and second objects are adjusted according to the deviation data corrected by the magnification error using the magnification error data. An alignment method characterized by moving two objects relatively.