JPS61102505A - Lighting device - Google Patents

Abstract

PURPOSE:To perform efficiently the lightings of a bright visual field and dark visual field of the light emitted from a light source by using the first parabolic mirror having the light source being arranged around a collector lens as a focus and by the second parabolic mirror having the visual field of a objective lens as a focus. CONSTITUTION:One part of the radiant light from the lamp 8 of a light source is led to an objective lens 4 via a half-mirror 10 by a collector lens 14. The first parabolic mirror 15 is arranged around the collector lens 14 and installed at the position making the lighting point of the lamp 8 as a focus. The second parabolic mirror 16 is arranged around the objective lens 4 and installed at the position making the visual field of the objective lens 4 as a focus. The pattern of a wafer 1 being thus lighted is enlarged with projection by the objective lens 4 and imaged on a pattern sensor 5. In this constitution, the radiant light from the light source can be utilized effectively due to the radiant light in the optical axis direction being used for the bright visual field lighting of the radiant lights from the lamp 8 and the radiant light in vertical direction to the optical axis being used for the dark visual field lighting.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a device that is attached to a photoelectron microscope or the like and illuminates a test food object with bright field or dark field at high illuminance.
In particular, the present invention relates to a lighting device suitable for illuminating a pattern inspection device, a dimension sub-length device, etc. [Background of the Invention] This lighting device is installed in, for example, an external appearance inspection device such as an IC or LSI, a pattern detection device, etc. Illuminate the object under test. The above-mentioned illumination device is generally required to have a function of illuminating a test object with high illuminance.

The problems with the conventional technique will be described with reference to FIG. FIG. 1 is a schematic optical path diagram showing an example of an LSI inspection device equipped with a conventional illumination device.

A sea urchin/N 1, which is an object to be inspected, is placed on an XY stage 3 fixed to a pace 2. Wafer 1
An objective lens 4 is disposed above, and the pattern on the wafer 1 is enlarged and projected, and an image is formed on a pattern sensor 5 disposed above the objective lens 4. On the other hand, the magnetic tape 6 that stores the design data of the circuit pattern of the Eva 1 as an image signal and the output signal of the pattern sensor 5 are electrically connected to be input to the defect determination section 7. There is. For illumination, light emitted from a lamp 8 as a light source is converted into parallel light by a collimator lens 9.

This optical path is bent by a half mirror 10 at 90 degrees, and the light 11 near the center of the optical axis passes through the objective lens 4 and bright-field illuminates the wafer 1 to be inspected. On the other hand, the light 12 at the outer edge of the optical axis passes through the outside of the objective lens 4 and is further reflected @! 13, the field of view of the objective lens 4 is dark-field illuminated.

The above-mentioned bright field and dark field illumination are selected or used in combination as the pattern shape and surface reflectance differ depending on the wafer process.

The entire surface of the wafer 1 is inspected in the order of continuous arrows S in FIG. While scanning X-Y stage 3 for inspection,
The pattern sensor 5 and the output signal of the magnetic tape B are compared in the defect determination section 7, and if a difference is detected, it is determined that it is an abnormal part. This inspection equipment has been developed as
There is a growing need to detect defects smaller than μm.

Therefore, the objective lens 4 also has a high resolving power (for example, N, Ao, 8. Depth of focus o, sitm, field of view 4
00μ77 is required, and bright illumination is required in order to detect the pattern on the wafer with a pattern sensor using the objective lens as described above. In order to speed up the inspection, it is necessary to transfer the charge signal of the pattern image charged and converted by the pattern sensor at high speed, and bright illumination is necessary to shorten the accumulation time in the light receiving section of the pattern sensor. becomes. In particular, the illumination method shown in FIG. 1 has the disadvantage that the illuminance of dark-field illumination is lower than that of bright-field illumination. Figure 1
In the dark field illumination method shown in 1, when there is a minute pattern (convexity) on the wafer 1, light hits the pattern and is scattered, and the scattered light enters the objective lens to detect the pattern.

However, since the amount of this scattered light is extremely small compared to bright-field illumination, dark-field illumination has the problem of being dark. Therefore, the brightness of the dark field illumination must be made as high as possible.

Furthermore, since the objective lens 4 is exposed to illumination light, the temperature of the indicator member (not shown) of the objective lens 4 increases, causing thermal deformation of the objective lens 4, causing the inspection point to gradually shift. , problems such as changes in magnification occurred, and there was also a fatal drawback of reducing inspection accuracy.

Related devices of this type include Japanese Patent Application Laid-open No. 55
Although the present invention is effective as an illumination method for revealing the presence of microparticles, such as foreign matter, on the surface of a sample such as a wafer, The problem is that the shape cannot be made manifest.

[Purpose of the invention]

The purpose of the present invention is to eliminate the drawbacks of the conventional technology, and to provide a bright and dark field of view that can illuminate the inspected object or length measuring section of an inspection device or length measuring device with high brightness, and reduce positional deviation and accuracy deterioration due to heat generation. The purpose of the present invention is to provide lighting devices.

[Summary of the Invention] - In order to achieve the above object, the present invention includes a collector lens that directs light emitted from a light source to an objective lens, and
A first parabolic mirror with the light source as its focal point is arranged around the collector lens, and a second parabolic mirror with the field of view of the objective lens as its focal point efficiently converts the light emitted from the light source into bright field and [Embodiments of the Invention] Hereinafter, embodiments of the present invention are shown in Figs. 3, 4, 5, and 6.
This will be explained using figures.

Figure 3 is an explanatory diagram of the basic principle of the present invention.

A part of the light emitted from the lamp 8 of the light source is guided to the objective lens 4 via the collector lens 14 and the half mirror 10. Although the optical path in the figure is shown as parallel light, the collector lens 14 is connected to the illumination optical axis. By moving in the direction, critical illumination in which the light source image is formed on the object plane (the surface of the wafer 1), or Kohler illumination in which the light source image is formed in the back focus of the objective lens 4, can be achieved.

Further, a first parabolic mirror 15 is arranged around the collector lens 14 with the light emitting point of the lamp 80 as the focal point, and a second parabolic mirror 16 is arranged around the objective lens 4 to focus on the wafer 1. It is installed at a position where the field of view of the objective lens 4 is the focal point. The illuminated pattern on the wafer 1 is projected and magnified by the objective lens 4 and is imaged on the pattern sensor 5 . In the above configuration, among the light emitted from the lamp 8, the light emitted in the optical axis direction is used for bright field illumination, and the light emitted in the direction perpendicular to the optical axis is used for dark field illumination, so that the conventional device (1st
Compared to Figure 1), the emitted light from the light source can be used more effectively.

Regarding bright field illumination, only the effective light flux that can be used for bright field illumination is used (in the conventional method shown in Fig. 1, only the central part of the light incident on the collimator lens 9 is used. ) The NA of the collector lens is the same or higher than that of the conventional illumination method. Furthermore, the dark-field illumination method effectively captures the light emitted from the surroundings of the light source, and since the illumination is performed using two parabolic mirrors, the illumination is extremely bright with little loss. Compared to the method shown in Figure 1, we were able to capture more than 10 times as much light with the illumination NA.

FIG. 4 shows an example of application of the present invention when a high-brightness arc lamp is used as a light source.The first parabolic mirror 15 is connected to the arc lamp 17 with the light source of the arc lamp 17 as the focal point. A second parabolic mirror 16 is placed around the objective lens 4.
around the wafer 1 and set at a position where the field of view of the objective lens 4 of the wafer 1 is the focal point. Further, a collimator lens 17 is arranged below the arc lamp 17. The aperture of the collimator lens 18 is larger than the inner diameter of the ring-shaped light beam guided by the parabolic mirror 15 and smaller than the outer diameter. The collimator lens is arranged so that the ring-shaped light is focused on the back focal position of the objective lens 4. In the middle of the optical path, an optical member 19 (integrator, diffuser, fiber, etc.) may be disposed to make the brightness of the light uniformed by the collimator lens 18. Above the objective lens 4, there is a half mirror. -20 is placed to guide the illuminated pattern of the wafer 1 to the pattern sensor 5. In the above configuration, the light emitted from the high 4[ arc lamp is utilized to the maximum,
Since the loss of dark field illumination due to the half mirror 20 is also removed, brighter dark field illumination can be achieved than in FIG. On the other hand, for inter-field illumination, 1/3 of the angle of capture taken into the parabolic mirror 15 is used, but the angle of intake taken into the collimator lens is 300. It is 360° in the horizontal direction. Conventional device (Figure 1)
The angle of capture of the Lang radiation in this embodiment was about 60 degrees in the vertical direction and 60 degrees in the horizontal direction, but the angle of capture in this embodiment is three times as large. Moreover, since a high-brightness arc lamp is used as the light source, the optical member 19 that makes the brightness uniform in the middle of the optical path
Also, even if a half mirror 20 is arranged, it is possible to provide much brighter illumination than before. Fig. 5 is an example of an illumination device implemented based on the above-mentioned principle.

The arc lamp 17 is supported by the lamp holder 21, and the parabolic mirror 15 is arranged around the arc lamp 17 with the light source of the arc lamp 17 as the focal point, as described above. In the middle of the optical path reflected by the first parabolic mirror 15, a cold filter 22 is arranged to reflect heat rays (generally light with a wavelength of 600 to 700 nm or more). The above parabolic mirror 15, lamp holder 21, and cold filter 22 are connected to the upper support frame 2.
It is held at 3. Further, the collimator lens 18 and the optical member 19 are held in a lens holder 24. Further, the objective lens 4 and the half mirror 20 are held in an objective lens holder 25, and a second parabolic mirror 16 disposed below the lens holder 24 is disposed concave around the objective lens 40, and the field of view of the objective lens 4 is It is placed at the focal point.

The objective lens holder 25 and the parabolic mirror 16 are mounted on the lower support frame 2.
6, and the upper support frame 23 and lens holder 25
, the lower support frame 26 are mutually supported. The objective lens holder 25 and the lower support frame 26 are provided with holes 20α and 26α for reflecting the reflected light detected by the objective lens 4 on the half mirror 20 and guiding it to the pattern sensor 5. Also, the lens holder 24 and the objective As shown in FIG. 6, the lens holder 25 is supported at three places, and has holes 24A and 25h of the same size as the inner and outer peripheries of the ring-shaped parallel light, and the holes 24A and 25H are provided with holes 24A and 25H of the same size as the inner and outer peripheries of the ring-shaped parallel light. It is designed to avoid blocking parallel light.

In the above configuration, the arc lamp 17 has i 100 WH?
Using a lamp, the light emitted from this bright spot becomes ring-shaped parallel light by a first parabolic mirror 15, and the second parabolic mirror 16 focuses the parallel light onto the field of view of the objective lens 4. . The parallel light incident on the collimator lens 18 passes through an optical member 19 that makes the brightness uniform, and forms an image at the back focal point of the objective lens, thereby illuminating the field of view of the objective lens 4. - The heat rays of the ring-shaped parallel light guided by the first parabolic mirror 15 can be removed by the cold filter 22.

The ring-shaped parallel light passes through hole 24b and then through hole 25b. For this purpose, the objective lens holder 250 shown in FIG.
Since the shadows of the three supporting parts of the lens holder 240 are projected on the three supporting parts, all of the supporting parts of the lens holder 25 are originally
It does not hit the parabolic mirror 16, but reaches the parabolic mirror 16. Furthermore, in order to keep the temperature of the lighting device shown in Figure 5 constant, passages for circulating cooling fluid such as water or air may be formed in the upper and lower support frames to cool the lighting device itself. good.

In addition, when it is desired to use only bright field illumination or dark field illumination, it is possible to easily switch between them by inserting a shutter into the lower part of the cold filter 22. [Effects of the Invention] As detailed above. When the lighting device of the present invention is used as a lighting device for an inspection device, a length measuring device, etc., it can illuminate the part to be inspected with high illuminance, and has an excellent practical effect of preventing a decrease in accuracy due to thermal effects, etc. Therefore, if the above-mentioned illumination device is used in a semiconductor LSI inspection device or the like, high-speed and highly reliable inspection is possible, and there is also the ripple effect of improving the yield of LSI.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an LSI inspection device equipped with a conventional illumination device, FIG. 2 is an explanatory diagram of a wafer inspection procedure, FIG. 3 is an explanatory diagram of the basic principle of the illumination method of the present invention, and FIG. 5 is a block diagram showing an application of the illumination method of the present invention, FIG. 5 is a sectional view showing an illumination device according to an embodiment of the present invention, and FIG. 6 is a plan view of the light transmitting section. 1... Wafer 4... Objective lens 8... Light source 14... Collector lens 15... Parabolic mirror 16... ... Parabolic mirror 17 ... Arc lamp 18 ... Collimator lens 19 ... Optical member 20 ... Half mirror 22 ... Cold Filter 24...Lens holder 25...Objective lens holder Fig. 3 Fig. 5

Claims (1)

[Claims] 1. Create an image of the object to be examined using an imaging optical system using a lens, detect this image by photoelectric means, and install it in a device that recognizes the position and shape of the object based on this detection signal. The illumination device includes a light source for illuminating the test object, a collector lens that guides light emitted from the light source to a lens that projects the test object, and a light source that focuses the light source and projects the light around the collector lens. It is characterized by comprising a first installed parabolic mirror and a second parabolic mirror that receives the ring-shaped parallel light from the first parabolic mirror and focuses it on the field of view of the objective lens. lighting equipment.