JPS6122237A - Apparatus for inspecting appearance of object - Google Patents

Abstract

PURPOSE:To enhance the reliability of inspection while making it possible to perform high speed inspection, by comparing pattern information, which formed the basis of the fabrication of a mask pattern, with the mask pattern. CONSTITUTION:The reference pattern from a magnetic tape 18 storing an information signal showing a pattern to be baked to a photomask is two-dimensionally regenerated in memory 9 while converted to a binary signal and, at the same time, a mask pattern to be inspected is regenerated in memory 8 and both signals are compared in a comparing circuit. If the mask pattern to be inspected has a flaw 19, the contents of the memories 8, 9 come to non-coincidence at the part corresponding to the position where the flaw is present to generate a non-coincident signal. Whereupon, a measuring machine detects the coordinates where said flaw is present and the coordinates signal is processed by CPU to be displayed on a recording display part as data. By this method, the confirmation of the flaw existence can be performed rapidly.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for inspecting the appearance of an object, such as an apparatus for inspecting the appearance of a photomask used in photolithography.

As one inspection method for photomasks, a method is generally adopted in which the surface of the photomask is magnified using a projector and the presence or absence of defects is visually inspected.

However, in this visual inspection, defects are often overlooked, the inspection takes a very long time, and
A problem arises in that the criteria for determining a defect differs depending on the individual.

Therefore, a standard pattern is photographed in advance with a television camera, the brightness and darkness of each pixel is converted into a binary signal, and this is stored on, for example, a magnetic tape.On the other hand, a cane test pattern is photographed with a television camera, An inspection method is also being considered in which the brightness and darkness of each pixel is converted into a binary signal, and this is compared with the signal stored on the magnetic tape described in (b), and if there is a discrepancy, it is determined that there is a defect.

However, in this method, there are cases where the standard pattern itself has defects, and there is a problem in that the reliability of the inspection results is low.

Pattern printing on the photomask to be inspected is performed using a barrier pull aperture as shown in Figure 5, and the control memory (generally magnetic tape) for moving the barrier pull aperture in the XY direction is An information signal indicating the pattern to be applied is stored. Therefore, if this pattern information signal is used as a reference signal for detecting defects in reticle patterns, it is possible to compare the pattern information that served as the basis for pattern creation with the pattern of the photomask being inspected, thereby eliminating errors in judgment. It should be possible. The present invention was made based on such an idea, and one of its purposes is an object appearance inspection device capable of inspecting the appearance of an object such as a mask using an absolutely correct reference, thereby increasing the reliability of the inspection. Another object of the present invention is to provide an apparatus for inspecting the appearance of objects that can perform inspections at high speed.

The present invention will be explained below with reference to Examples.

Figure 1 shows the X-Y on which the mask to be inspected is placed on the visual inspection device.
It is a perspective view showing a stage part.

Reference numeral 1 denotes an ultra-high pressure water lamp (250 W), which serves as a light source for irradiating light from the lower surface of the master reticle 3 to be inspected. 2 is an X for accurately sending the reticle 3 at a constant speed in the scanning direction.
-Y stage, 4 is a motor for scanning, 5 is a length measuring device for measuring the XY coordinate position, and 6 is a photodiode play for converting the brightness of the pattern into an air signal.

FIG. 2 shows the system configuration of this device.

2 is an XY stage, 5 is a length measuring device, 6 is a photodiode array, 7 is a circuit that quantizes the output of the photodiode array and converts it into a binary signal of "1" and "O", and 8 is the appearance of the mask to be inspected. 9 is a memory A that stores a signal obtained by binarizing , a memory B that stores a signal indicating a reference pattern,
10 is the signal stored in memory A8 and memo IJ B 9
The purpose is to recognize defects from the signals and features stored in the system.

12 is an error output circuit, which is a comparison circuit 10 or a recognition unit 11;
If there is an error signal from the CPU, an interrupt command signal is issued to the CPU. 13 is a buffer for temporarily storing a signal indicating a reference pattern from the CPU; while the reference pattern signal from the CPU is being sent to one buffer signal, it is previously stored in the other buffer; The stored signal is sent to the memory B9. 15 is the CPU (
16 is an operation console, 17 is a recording unit 51, and 18 is a magnetic tape that stores signals obtained by decomposing the outline of the reference pattern into vectors for controlling the barrier aperture of the pattern generator for printing. be. Let me explain with a specific example.

The pattern shown in Figure 3 (a) is decomposed into vectors a * b and c in the X direction, and each vector has its Y coordinate, the X coordinate of the start point Xs, and the end point Xe as shown in the table below. , and write it on the magnetic tape 18 (
b) Stored sequentially as shown in K.

The signals stored on the magnetic tape 18 are transferred to the buffer memory 13 through the CPU, and at the same time,
The signal from the buffer memory 14 is converted into a '1"60 signal corresponding to the stored content of the buffer memory 14, and the pattern is two-dimensionally reproduced in the memory B9.

Then, as shown in Figure 4, the reference pattern is memorized for month B.
) is converted into a binary signal and reproduced, and the mask pattern to be inspected is also reproduced in the memory A8, and both signals are compared in the comparison circuit 10.

If there is a defect 19 in the mask pattern to be inspected, the contents of memories A and B do not match in the portion corresponding to the position where the defect exists, so a mismatch signal is generated and an interrupt command is issued from the error output circuit 12 to CPUK. It will be done. Then,
The length measuring device 5 detects the coordinates where the defect exists, the CPU processes the coordinate signals, and outputs the data to the recording/display section 17. This allows faster identification of defects.

By the way, according to the present invention, mask pattern creation 1')
Since the base pattern information and the mask pattern are compared, the absolute correct pattern is memorized as a signal, and the mask pattern to be inspected is compared with it. This eliminates false judgments. I can do it.

The present invention is particularly effective for visual inspection of a photomask for photoetching, for example, a master reticle in which a portion corresponding to one beret is enlarged ten times.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an example of an XY stage section on which a mask to be inspected is placed in a visual inspection apparatus used in the present invention. FIG. 2 is a block diagram showing the system configuration of this device. FIG. 3 is an explanatory diagram showing an example of the reference pattern (al is an example of the reference pattern, and bl is an explanatory diagram showing that vectors expressed in a manner similar to the magnetic tape are sequentially stored. FIG. 4 is an explanatory diagram showing the reference pattern and the mask pattern to be inspected. It is an explanatory diagram of a device for comparing and detecting defects. Fig. 5 is a JN view showing a barrier pull aperture for printing a mask pattern to be inspected. 1... Ultra-high pressure mercury lamp, 2... X-Y Stage, 3・
... Master reticle to be inspected, 4... Scanning motor,
5... Length measuring device for coordinate detection, 6... Photodiode array, 7... Quantization circuit, 8... Memory A, 9...
...Memory B, 10... Comparison circuit, 11... Recognition section, 12... Error output circuit % 13.14... Bumper register, 15... CPU, 16... Operation console,
17...recording 9 display section, 18.magnetic tape, 19...
- Defect, 20...Reference mask pattern. (oc″-

Claims (1)

[Claims] 1. An XY table movable in the XY directions, a circuit for creating first information corresponding to a pattern formed on an object placed on the XY table, and used to form a pattern of a fixed shape on the object. a circuit for creating pattern forming information to be used as second information that can be compared with the first information;
An apparatus for inspecting the appearance of an object, comprising a comparison circuit for comparing the first information and the second information, and inspecting the appearance of the object based on an output signal from the comparison circuit.