JPS60261133A - Inspection device - Google Patents

Abstract

PURPOSE:To enable even inspection at a time when the size of a pattern to be inspected differs from a design data pattern by providing a means through which the magnification of image formation is varied while the optical path of an optical system image-forming a circuit forming pattern image to a sensor is kept constant. CONSTITUTION:A lens 19 is fitted to the upper section of an objective 9, and the pattern image of a photo-mask 1 image-formed by the objective 9 is image- formed to a pattern sensor 10. The lens 19 is driven by a motor 23 controlled by a magnification variable control section 25 connected to a microprocessor 15. Since data 12 in a magnetic tape and the error of magnification of the photo- mask 1 are determined previously on the manufacture of the photo-mask, the informations are inputted previously to the microprocessor 15. The magnification variable control section 25 drives the motor 23 on the basis of a command from the microprocessor 15, and moves the lens 19 up to a predetermined position.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to horizontal pattern placement, visual inspection, etc. of semiconductor photomasks, wafers, and glass masks for printed substrates.

[Background of the invention]

Taking an LSI visual inspection device as an example, the prior art will be explained with reference to FIG. FIG. 1 is a perspective view of an LSI photomask appearance inspection apparatus with an iliI1m mechanism added.

An X stage 4 is installed on the stage pace 2 via an X stage 3 to constitute an X, Y stage, and a photomask 1, which is an object to be inspected, is placed on the X stage 4. The X stage 3 and the X stage 4 are connected to a Y-axis moving section 5 and an X-axis moving section 6, which are external drive devices, respectively, and can be moved in the Y direction and the X direction, respectively.

The amount of movement of the X stage 4 and the X stage 6 is measured by the X-axis length measuring device s and the Y-axis length measuring device 7, respectively. on the other hand,
The means for automatically detecting the pattern of the photomask 1 is constructed as follows.

An objective lens 9 is provided above the photomask 1, and a pattern sensor 10 is provided on its imaging plane. The output of this pattern sensor f10 is input to the signal comparison circuit 14 via the butter 7 signal binarization circuit 11. A signal read from the magnetic tape 12 on which the photomask 10 circuit pattern design data is stored is also input to the signal comparison circuit 14 via the pattern signal binarization circuit 16. The above magnetic tape 12 is read by the microprocessor 150.
The comparison result in the signal comparison circuit 14 is input to the microprocessor 15 mentioned above.

The Y-axis length measuring device 7 and the X-axis length measuring device 8 are connected to a coordinate length measuring circuit 16, and the coordinate sub-length measuring circuit 16 is connected to a micro brochure.
5. The microprocessor 15 is also connected to the XY drive #J control section 17, and through the XY drive control section 17, the X-axis movement section 6. The Y-axis moving section 5 can be controlled.

In the photomask inspection apparatus described above, the magnetic tape 12 includes:
The design data at the time of photomask creation is stored as an image signal, and the pattern signal binarization circuit 15 converts the logic level Ay.
The pattern on the photomask 1 is converted into an image signal by the pattern sensor f10 on the objective lens 9, and the logic level g011.t1 is converted into the pattern signal 21 by the pattern signal converting circuit 11. '' digital image signal.

The digital image signal of the design data read from the magnetic tape 12 and the image signal detected from the photomask 1 are compared in the signal comparison step @ 14, and if there is a difference, the microgrosses A signal is sent.

Upon receiving the above signal, the microprocessor yf15 determines whether or not the difference is due to a defect in the circuit pattern of the photomask 10, and if so, notifies the printer 18 of this fact. This inspection is carried out by moving the photomask 1 with respect to the objective lens 9 in the direction of the reciprocating arrow and sequentially scanning the entire surface.

The microprocessor f15 moves the photomask 1 in the direction of arrow A through the XY drive control s17.
Y#l drive unit5. Controls the X-axis moving section 6. The coordinate measurement circuit 16 measures the inspection position of the photomask 1, and the coordinates of the photomask where a defect is found are determined by the microprocessor 91.
5 and output to the printer 18. Further, the coordinate measuring circuit 16 accurately measures the inspection start and end coordinates of the photomask 1 and outputs them to the microprocessor f15, and the microprocessor f15 controls the drive of the magnetic tape 12 based on these measurements. With the miniaturization of T and 8 I patterns, it is now necessary for this device to detect defects of 1 μm or less. For this reason, the optical system uses a high-resolution lens, such as NAO19, and a high-resolution lens with a depth of focus α3 μm, and the inspection stage also uses a high nt degree with a yaw error of 1 μm or less. Although the inspection equipment used to compare the sample pattern described above can perform reliable inspection, due to the miniaturization of pattern dimensions, the mask to be inspected has become slightly thinner, for example, by about 0.2 μm, compared to the design data. However, problems are beginning to arise in which even thicker unevenness is judged as a defect. °Explain particularly problematic shortcomings.

The most common photomask manufacturing method is to create an original plate (retek/l/) that is 10 times the size of the t2 pattern created based on the design data, and then step
And 9-peat camera (using photo 9 beatan, 1
A photomask is obtained by repeatedly performing exposure with /1o reduction. In recent LSIs, the line width and minute geowire width have become less than 2 μm. When transferring this fine line width from the mask to the square, the thickness of 2 μm depends on the exposure conditions, resist film thickness, uniformity, etching, etc.
The line width of the mask may not be transferred as is. (For example, 2 μm (1) Line width force, 2.2 μm + ts
To deal with this, recently the dimensions of the photomask have been controlled in advance to obtain the regular line width (2 μm) on the surface of the sea urchin. That is, when manufacturing a photomask, the photomask is made thicker or thinner by about 10 to 20% in advance by controlling the exposure t when VIQm small repeated exposure is performed at photo9 Peter.

Compared to the pattern dimensions created as the design data above, if we compare the master pattern, which has become thinner and thicker, with the design data that generates normal -tg data, we can see that it is a positive f pattern. Naturally, it is easier to judge it as a defect.

Recently, due to the above-mentioned reasons, the number of defect judgments by inspection equipment that compares with this type of model pattern, that is, the number of incorrect judgments, has increased.
A disadvantage has arisen that the performance of the inspection device is significantly reduced.

[Purpose of the invention]

The purpose of the present invention is to convert the pattern size to an arbitrary size with a simple adjustment of the optical system, even if the pattern size of a photomask or the like is enlarged or reduced compared to one method of design data. The goal is to provide inspection equipment that has been tested.

[Summary of the invention]

In order to achieve the above-mentioned object, the present invention provides a lens having means movable in the optical axis direction in the optical path of the optical system for forming a pattern image of a photomask or the like into a centimeter for photoelectric conversion. Furthermore, the optical path length of the optical system is kept constant.

[Embodiments of the invention]

The second example is an embodiment of the present invention. The differences between FIG. 2 and FIG. 1 will be explained. A lens 19 is provided above the objective lens 9, and the pattern image of the photomask 1 formed by the objective lens 9 is imaged on a pattern sensor. lens 1
Numeral 9 is fixed to a nut (21K) engaged with a screw 20, and a gear (1) 22 is fixed to one end of the screw 20. The gear (1) 22 meshes with the gear (2) 24 of the motor 23.

The motor 26 is connected to a variable magnification control section 25, and the variable magnification control section 25 is connected to a microprocessor f15. The structure of the song and the operation of the detector are the same as those shown in FIG. The difference between the data 12 of the magnetic tape and the magnification #4 of the photomask 1 is known in advance at the time of photomask production, so this information is transferred to the microblock 4.
Enter it in f15. The variable magnification control 25 drives the motor 25 based on the command from the microprocessor f15.
Gear (2)24. The lens 19, which is fixed to the nut 21 via the gear (1) 22, is moved to a predetermined position.

FIG. 3 is an explanatory diagram of magnification adjustment. An outline of the optical path will be explained. The pattern 26 of the photomask 1 is projected by the objective lens 9 to create a 100x first image. Here, the objective lens 9 is 1
In order to detect defects of less than .mu.m, we used a high-resolution lens with a poor resolution of up to 0.3 .mu.m, N, AO, 9, and a focal length of 2.1 m. Further, a lens 1 is placed behind the first image in the optical axis direction.
9 is set as a pattern sensor and imaged on flo. The basic imaging magnification in this case is 1*1 ('t''=''+). That is, an image 100 times larger than the mask pattern 26 is projected onto the pattern centimeter 10. The depth of focus of the objective lens 9 used here was ±0.6. Δ in αm2 diagram
m = 0.3, αm. Focal length and magnification α
=2.12131s, A=212.1peng. Here, 6 + 0.3 μm and 18 are 4-3 m, and α
When the value is -0.3 μm, b becomes J+3 parrot.

That is, the depth of focus I on the first image plane is +54, and a clear image can be obtained within this range. The first image is formed by the lens 19 as a pattern sensor f-plane tl-2 image.If the focal length of this lens 19 is 100 mm, then a
When T =: 41, '+'' = 2001a.

Sheath = 200 parrots. FIG. 4 is a diagram showing the relationship between magnification and optical path length. The horizontal axis is the magnification 4'/eL1. The vertical axis indicates the optical path length (cL+-Ml). It can be seen from this figure that the optical path length increases as the magnification changes. However, tX+4 in Figure 6
Optical path length of 1 plus l"++4++JL-+ =403
In the embroidery range, even if the lens 19 is moved back and forth in the optical axis direction, the second solution is 1.4! Approximately 0.
It is possible to vary the magnification from 8 times to 1.2 times. In other words, the range of the depth of focus in the first image (in this example, 3
Even if the lens is moved within the camera, a clear image will be projected on the second image. In reality, since N and A of the lens 19 are also involved in the second mound, the origin depth at the second mound is even deeper.
Even if the lens 19 is moved by about 10 a, the overall optical path length can be kept constant and a clear pattern can be obtained.

That is, by moving the lens 19, the magnification factor can be varied by a factor of 0.7 to 1.6 times, which is 0J.

FIG. 2 shows an embodiment of the present invention.
3 has a step angle of 7.2° and gear (1) 22. gear 12
)24 gear ratio to 2:1. If the screw is 20 mm and the screw is 1 tin, the disassembly distance can be moved by 10 μm, and the magnification can be adjusted.
Since the magnification can be varied while keeping the optical path length constant for defect inspection, the magnification adjustment mechanism is simple and compact, which also has the advantage of making the inspection equipment more compact.

〔Effect of the invention〕

As described above, the inspection apparatus of the present invention has the advantage that even if the pattern to be inspected is reduced or enlarged compared to the design data pattern, it can be inspected without treating a normal pattern as a defect. Yield and productivity can be greatly improved.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of an LSI Gaei inspection device manufactured by Jubei, and Fig. 2 is an explanatory diagram of an LSI visual inspection device of an embodiment of Fu5?3 Mei.
FIG. 3 is an explanatory diagram of the optical path of the present invention, and FIG. 4 is a diagram illustrating the relationship between magnification and optical path length. 1... Photomask, 9... Objective lens 5.10...
・Pattern cm, 19...lens, 20...screw, 21...nut, 22...gear (1), 26...
・Motor, 24...Gear patent attorney Akira Takahashi
Figure 2 Figure 3

Claims (1)

[Claims] 1. The circuit formation pattern of a semiconductor photomask, wafer, or substrate is imaged on a sensor using optical means, photoelectrically converted, and compared with other reference patterns to inspect the circuit formation pattern. An inspection device characterized in that the device is provided with means for making a storage magnification variable while keeping constant an imaging optical path length of an optical system for forming an image of the circuit formation pattern on a sensor.