JPS633156Y2 - - Google Patents

Description

[Detailed explanation of the idea] The present invention relates to an LSI inspection device.

The prior art will be explained with reference to FIG. 1, taking an LSI photomask visual inspection apparatus as an example.

An X-Y stage 2 is provided on the base 1, and a transport device 4 that moves in the front, back, right and left directions of the figure and loads or unloads a mask 3 having a circuit pattern on this X-Y stage 2 is installed. has been done. In order to supply the mask 3 to the transport device 4 (or to store the mask 3 from the transport device 4), a cartridge 5 is provided next to the transport device, and it is possible to automatically supply or store the mask 3. It's summery. A mask stand 6 for holding a mask 3 is fixed to the XY stage 2, and the mask 3 is illuminated from below at two locations by left and right illumination lenses 7 and 8. Above the mask 3, an inspection microscope 9 is installed on the base 1 by a column 10, and left and right objective lenses 11, 12 above the illumination section.
The pattern of the mask 3 is enlarged and projected through the left and right sensors 13 and 14 in the inspection microscope 9.
It is electrically input to the defect determination section 15.

In the apparatus configured as described above, when the mask 3 stored in the cartridge 5 is loaded onto the mask stand 6 on the XY stage 2 by the transport device 4, the inspection is automatically performed as follows.

FIG. 2 shows a detailed diagram of the photomask 3. The photomask 3 has the same circuit patterns arranged regularly in a checkerboard pattern. In the initial state of the test,
The left objective lens 11 is positioned on the chip pattern 16 and the right objective lens 12 is positioned on the chip pattern 17, and the X-Y stage 2 is positioned so that the left pattern sensor 13 and the right pattern sensor 14 detect the same location of the LSI circuit pattern. The distance between the left and right objective lenses 11 and 12 is determined. (The positioning mechanism is not shown.) Next, while maintaining the distance between the objective lenses,
The stage is moved and the entire surface of the photomask is inspected in the order of the arrows in FIG. X-Y stage 2 for inspection
While scanning, the output signals of the left and right pattern sensors 13 and 14 are compared by the defect determination section 15, and if there is a difference, it is determined that it is an abnormal part.

In order to detect defects of 1 to 2 μm, this inspection equipment requires a high resolution objective lens and uses a high-magnification objective lens (50x to 100x), and the time it takes to inspect the entire mask surface is 1 to 2 μm. 2μm defect detection
It takes 60-90 minutes. During this inspection, if there is a foreign particle of the same size (1 to 2 μm) on the mask pattern,
Naturally, there is a possibility that it will be judged as a defect. However, with this device, 5 to 10 masks are automatically inspected continuously, so the masks are stored in the cartridge for 5 to 10 hours. Foreign matter adheres. As a countermeasure, we put the equipment itself in a clean room,
We are taking precautions to prevent dust by enclosing it with clean benches. However, in recent years, as LSI patterns have become smaller, it has become necessary to inspect even smaller defects (defects of 1 μm or less), and the above dust prevention measures have become insufficient. For example, even if the equipment is inspected in an extremely clean bench with a class 100 level of cleanliness,
The clean bench is filled with foreign matter of 1 μm or less, and there is a risk that the foreign matter will adhere to the mask pattern surface just by moving the X-Y stage during inspection. The main flow of air inside the clean bench is downflow (air flows from top to bottom). For this reason, if the pattern surface of the mask faces upward, foreign matter within the apparatus (such as foreign matter adhering to the inspection microscope in FIG. 1) is likely to adhere to the mask pattern surface. Furthermore, since the masks are stored and transported with their patterned surfaces facing upward, foreign matter tends to adhere to the patterned surfaces of masks waiting to be inspected, which reduces the reliability of defect inspection and ultimately reduces the yield of semiconductor products.

The purpose of this invention is to prevent foreign matter from adhering to the circuit-forming surface of the photomask until the photomask is stored in a cartridge, transported to a mask stand, inspected, and then returned to the cartridge, and to be transported without damaging the circuit pattern. The object of the present invention is to provide an LSI inspection device that can inspect defects of 1 μm or less with high precision.

That is, in order to achieve the above object, the present invention includes a cartridge in which a large number of semiconductor photomasks are stored with the pattern side facing down, and a cartridge in which the photomasks stored in the cartridge with the pattern side facing down are placed outside the pattern side. A pair of belts is used to load and transport the photomask in contact with both ends of the pattern surface, and to transport the photomask to the inspection position, and to store the photomask in the cartridge after the test. In order to load the photomask brought to the inspection position by the transport means with the pattern side facing down, a mask stand and the mask stand are attached and moved in the X and Y axis directions. In order to image the circuit pattern to be compared formed on the photomask from the lower side of the photomask loaded on the mask stand of the X-Y stage, the A pair of imaging means each having an objective lens and a sensor corresponding thereto, and a defect determination means for comparing circuit patterns imaged by each of the imaging means to determine a defect. This is an LSI inspection device featuring:

An embodiment according to the present invention will be described using FIG. 3. FIG. 3 shows an embodiment of the LSI photomask inspection apparatus of the present invention.

An X-Y stage 19 is provided on the base 18, and a transport device 20 is installed that moves in the front, rear, right and left directions of the figure and loads or unloads the mask 3 having a circuit pattern on the X-Y stage 19. There is. A cartridge 21 is provided next to the transport device to supply the mask 3 to the transport device 20 (or to store the mask 3 from the transport device 20), and it is possible to automatically supply or store the mask 3. It's summery. A mask stand 22 that holds a mask 3 is fixed to the X-Y stage 19, and the mask 3 is attached to left and right illumination lenses 23, 24.
It is illuminated from above in two places. Below the mask 3, an inspection microscope 25 is installed on the base 18 with a flange 26, and illumination lenses 23, 24
The pattern of the mask 3 is enlarged and projected by the lower objective lenses 27 and 28, and is electrically input to the defect determination section 31 through the left and right sensors 29 and 30 in the inspection microscope 25.

In the apparatus configured as described above, when the mask 3 stored in the cartridge 21 is loaded onto the mask stand on the XY stage 19 by the transport device 20, the inspection is automatically performed as in the conventional inspection apparatus.

Since this device inspects the mask pattern surface downward, foreign matter falling from above adheres to the non-pattern surface and is less likely to adhere to the pattern surface. Even if foreign matter adheres to the non-patterned surface, since a high-magnification objective lens is used, the depth of focus is shallow and there is no effect on the detection of defective patterns. Furthermore, when storing the mask 3 in the cartridge 21 shown in FIG. 4, by storing the mask 3 with the mask pattern side facing down, it is possible to reduce the adhesion of foreign matter to the pattern side of the mask waiting for inspection. Furthermore, in the means of conveying the mask 3 by rotating the belt pulley 36 and placing the mask 3 on the belt 37 during conveyance, as shown in FIG.
By conveying the belt without touching it, it is possible to reduce the adhesion of foreign matter during conveyance. In this way, even if this device is used in a clean bench (not shown) and foreign matter due to the air flow (downflow) adheres to the top surface of the mask, it will not affect defect inspection of 1 μm or less, and it will not affect the inspection of defects of 1 μm or less. The negative effects of this can be greatly reduced.

As mentioned above, with conventional equipment, foreign matter easily adheres to the mask pattern surface, which is an obstacle to inspecting defects of 1 μm or less. However, according to the present invention, the pattern between the cartridge and the mask stand is By transporting the circuit pattern face down without damaging it, we can prevent foreign matter from adhering to it, and by imaging the circuit pattern with an imaging device, we can detect defects as small as 1 μm or less. This has the effect of improving yield.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a conventional LSI photomask inspection device, Fig. 2 is a diagram showing the LSI photomask inspection method and inspection order, Fig. 3 is a block diagram of the LSI photomask inspection device of the present invention, and Fig. 4 is a photomask FIG. 5 is a diagram showing the storage and transportation of the photomask. 3...Mask, 18...Base, 19...X-
Y stage, 20...Transfer device, 21...Cartridge, 22...Mask stand, 23...Left illumination lens, 24...Right illumination lens, 25...Inspection microscope, 27...Left objective lens, 28... Right objective lens.

Claims (1)

[Scope of utility model registration request] A cartridge stores a large number of photomasks for semiconductors with the pattern side facing down, and the photomasks stored in the cartridge with the pattern side facing down are loaded and transported with both ends, which are outside the pattern side, in contact with each other. The photomask is brought to the inspection position, and after the inspection, the photomask is loaded and carried in the cartridge in order to be placed in contact with both ends outside the pattern surface. In order to load the photomask brought to the position with the pattern side facing down, a mask stand and an X-Y stage configured to be able to move the mask stand and move in the X and Y axis directions are installed. In order to image the circuit pattern to be compared formed on the photomask from the lower side of the photomask loaded on the mask stand of the X-Y stage, an objective lens and a sensor are provided corresponding to the pitch of the circuit pattern. What is claimed is: 1. An LSI inspection device comprising: a pair of image pickup means; and a defect determination means for comparing circuit patterns imaged by each of the image pickup means to determine a defect.