JPH0258766B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an alignment method and apparatus for performing relative positioning of a reticle (mask) and a wafer in a projection aligner.

In this type of conventional alignment method, a target formed on a mask and a target formed on a wafer are detected respectively, and the two targets are aligned so that they coincide on the wafer surface. In this case, the target on the mask is easy to detect because it can be formed as a light-transmissive or non-transmissive pattern in the same way as other mask patterns, but the target on the wafer is formed by the unevenness of the wafer surface. This poses a problem in that detection becomes difficult. In particular, the wafer target is exposed through a projection optical system for pattern exposure in the same way as the mask target, but the resolution is limited because the numerical aperture (NA) of the optical system is limited by projection characteristics. Moreover, the wafer target is SiO ₂ or Si with a slight step (200
10,000 Å) or with a step smaller than this depending on the process, a sufficient difference in light reflection cannot be obtained, and in some cases, the wafer target may not be detected at all.
Furthermore, since g-rays are normally used for detection, there is a problem that interference fringes are likely to occur and the signal shape becomes complicated.

In addition, when using X-rays or electron beams to project a pattern, the relative positions of the X-ray mask and wafer target, which have a gap of about 10 μm, are detected using the same microscope, while the electron beam is used to expose the target to light. Alignment is performed by irradiating a beam from a beam device onto a wafer pattern and detecting the amount of reflected beam. However, with X-rays, the mask and wafer targets, which are 10 μm apart, are viewed simultaneously, so high NA lenses cannot be used, and with electron beams, the beam for exposure and position detection are the same, so there are design constraints and high precision. There is a problem that position detection over a wide range becomes difficult.

Therefore, an object of the present invention is to provide a pattern position detection device having a high numerical aperture lens adjacent to a mask pattern projection device capable of generating a reference pattern, and to detect the relative position between the pattern projection device and the pattern position detection device. While determining the wafer position using a pattern position detection device,
It is an object of the present invention to provide an alignment method and apparatus that can align a wafer with respect to a pattern projection device and thereby perform highly accurate positioning.

Hereinafter, the present invention will be explained based on embodiments shown in the drawings.

FIG. 1 is a block diagram of one embodiment of the apparatus of the present invention, in which 1 is a mask pattern projection device, and 2 is a position detection device disposed adjacent to this mask pattern projection device 1. In FIG. The mask pattern projection device 1 includes a mercury lamp 3 and a reduction lens 4 for imaging, and is configured to image the pattern of a reticle (mask) 5 at a position near the top surface of an XY table 6. A rectangular position detection mark 7 as shown in FIG. 2A is formed on the reticle 5, and the position detection mark 7 can be imaged simultaneously or separately on the XY table. The position detection device 2 includes a lamp 8 that emits a continuous spectrum, a condenser lens 9, a half mirror 10, a high numerical aperture objective lens 11, a cylindrical lens 12, and a linear image sensor 13. While the light is irradiated onto the object to be inspected above, the position of the object can be detected by detecting the reflected light by the linear image sensor 13.

On the other hand, on the upper surface of the XY table 6, as shown in FIG. 2B, there is a rectangular opening 14 corresponding to the opening forming the position detection mark 7, and an optical sensor 15 provided below this opening. A light amount detector 16 having the following is provided. Further, a wafer 17 as a test object is mounted and supported next to this light amount detector 16, and these light amount detector 16 and wafer 17 are connected to the mask pattern projection device 1 and the position detection device 2. The XY table 6 is operated to move the XY table 6 back and forth. Of course, a target 18 is formed on the wafer 17. Further, the XY table 6 is provided with a length measuring device 19 for detecting the moving position of the XY table, and the output of this length measuring device 19 and the output of the light amount detector 16 are input to the control section 20.

Next, the method of the present invention will be explained together with the operation of the apparatus of the present invention having the above structure. First, the XY table 6 is moved so that the image of the position detection mark 7 of the mask pattern projection device 1 coincides with the aperture 14, and thereby the XY table position at that time is measured by the length measuring device 19.
Find it at In this case, by detecting the change in the output of the light amount detector 16 as the XY table 6 moves, it is possible to accurately determine whether the position detection mark 7 and the aperture 14 match. Next, the XY table 6 is moved to the left in the figure, this time the position detection device 2 recognizes the aperture shape, and the aperture 14 is aligned with the optical axis of the position detection device 2 based on the detection signal of the linear image sensor 13. Find the XY table position when matching. Therefore, by this length measurement, the relative position between the mask pattern projection device 1 and the position detection device 2 can be determined.

On the other hand, in the position detection device 2, the target 18 on the wafer 17 is detected by the high resolution effect of the objective lens 11 with a high numerical aperture, and the position of the wafer 17 can thereby be determined.

As a result, a suitable position of the wafer relative to the mask pattern projection apparatus can be determined from the relative position of the mask pattern projection apparatus 1 and the position detection apparatus 2 and the position of the wafer 17 relative to the position detection apparatus 2, and accurate alignment can be performed. This is possible.

Therefore, in this alignment, the wafer position is detected using the objective lens 11 with high resolution and a high numerical aperture, so that the wafer target can be detected reliably and with high precision, and high precision alignment can be realized. Furthermore, since continuous spectrum light is used for detection, there is an advantage that interference fringes are less likely to occur and the signal shape is simple, making signal processing easier.

Here, as shown in FIG. 1, a first illuminance sensor 21 detects the direct illuminance of the mercury lamp 3, a second illuminance sensor 22 detects the illuminance immediately before the mask 5, and a Third illuminance sensors 23 that detect illuminance are connected to the lamp control unit 24, and the third illuminance sensors 23 are connected to the XY table 6.
Due to the movement of the wafer, the illuminance can be detected just before the wafer is exposed. With this configuration, in addition to the spot illuminance detection performed by the first illuminance sensor 21 and the second illuminance sensor and the control of the exposure amount to the wafer thereby, the third illuminance sensor 23 detects the average illuminance on the wafer surface. By detecting the illuminance of each chip and calculating a correction value using this detected value to correct the control by the first and second illuminance sensors described above, variations in illuminance for each chip on the wafer can be prevented and fine patterns can be improved. High precision can be promoted.

FIG. 3 shows another embodiment of the device of the present invention, in which the same parts as in FIG. 1 are given the same reference numerals. In this embodiment, the light source of the mask pattern projection device 1A is
A radiation source 25 is used, and instead of omitting the imaging lens, a mask 5 having a position detection mark 7 is placed close to the aperture 27 of the X-ray detector 26 (at the same height as the surface of the wafer 17). It is designed to perform pattern projection. Therefore, an X-ray sensor 28 is disposed within the X-ray detector 26.
This embodiment is completely different from the previous example except that X-rays are used to project the mask pattern onto the wafer 17, and an X-ray detector 26 is used to detect the position of the projection device 1A. Highly accurate alignment can be performed in the same way.

FIG. 4 shows yet another embodiment, in which an electron beam is used in the mask pattern projection device 1B. That is, the mask pattern projection device is an electron beam source 2.
9, a pattern generator 30 and an electronic lens 31 are provided, and the pattern generator 31 generates a mask pattern and a mark for position detection. Further, the position detection mark can be detected by an electron beam detector 34 consisting of an aperture 32 provided on the XY table 6 and an electron beam sensor 33. This embodiment is exactly the same as the previous example, except that an electron beam is used to project the mask pattern onto the wafer 17, and an electron beam detector is used to detect the position of this projection device. Highly accurate alignment can be performed.

FIG. 5 shows a modification of the embodiment shown in FIG. 4, in particular a modification of the position detection device. In the figure, the same parts as in FIG. Wafer 17 is installed next to wafer 17.
The wafer 17 is positioned with high precision by detecting one of the targets with the position detecting device 2 as in the previous example, and then detecting the position of the other target extremely finely with the target precision detecting device 37. It is advantageous if the position of the aperture 32 is detected by the target precision detection device 37, since the electron beam detector 36 can be used as is.

According to this embodiment, the position of the wafer 17 and the position of the opening 32 can be minutely detected by the target precision detection device 37, which is a part of the position detection device, so that the alignment precision can be further improved. can.

Here, the position detection mark is not limited to the shape shown in FIG. 2.

As described above, according to the alignment method and device of the present invention, a position detection device having a high numerical aperture lens is provided adjacent to a mask pattern projection device that can generate position detection marks, and the pattern projection device and The wafer is aligned with the pattern projection device by determining the wafer position with the position detection device while determining the relative position with the position detection device.
This has the effect that alignment using a lens with a high numerical aperture can be performed and highly accurate alignment can be performed.

[Brief explanation of drawings]

Figure 1 is an overall configuration diagram of the device of the present invention, Figure 2A,
B is a plan view of the aperture constituting the position detection mark and the detection aperture, and FIGS. 3 to 5 are configuration diagrams of different embodiments of the apparatus of the present invention. 1, 1A, 1B...Mask pattern projection device, 2
...Position detection device, 5...Mask, 6...XY table, 7...Position detection mark, 11...High numerical aperture lens, 13...Linear image sensor, 16...Light amount detector, 17...Wafer, 18...Target, 19
...Laser length measuring machine, 20...Control unit, 21-23...Illuminance sensor, 24...Lamp control unit, 25...X-ray source,
26...X-ray detector, 29...electron beam source, 30...pattern generator, 31...electron lens, 34...electron beam detector, 35...electron scanning source, 36...electron beam detector.

Claims (1)

[Claims] 1. A reticle pattern projection device projects a position detection mark provided on a reticle onto an XY table, and a light intensity detector provided on the XY table measures the result of the projected position detection mark. While detecting the image position, the position of the XY table at the time of detection is determined by a length measuring machine that detects the moving position of the XY table, and then the XY table is moved to
The position of the light intensity detector on the table is detected by a position detection device provided separately from the projection device, and the position of the XY table at the time of detection is determined by a length measuring device, and the XY table is moved to The target position on the wafer is detected by a position detection device, the position of the XY table at the time of detection is determined by a length measuring device, and the wafer is then aligned with respect to the reticle pattern projection device based on the detected position. alignment method. 2. A reticle pattern projection device capable of generating at least a reticle position detection mark, a position detection device provided adjacent to the reticle pattern projection device, and an XY projection device on which the reticle position detection mark is projected. a table; a light amount detector provided on the XY table to enable detection of the position of the position detection mark of the reticle projected on the XY table and the position of the position detection device; and the detector; adjacent to
It is equipped with a wafer placement section provided on an XY table for placing a wafer having a target thereon, and a length measuring device for detecting the amount of movement of the XY table, and the detector on the XY table is , the position where the position detection mark of the reticle is imaged, the position of the position detection device, and the target position on the wafer can be detected in cooperation with the length measuring device, and the detector and the position detection device An alignment device characterized in that it is configured to control an XY table based on the output of the device.