JPH0458623B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to a method for inspecting a mask, and more particularly to a method for detecting defects on a patterned surface of a photomask or a wafer chip.

(b) Background of the technology In recent years, as semiconductor devices and semiconductor integrated circuits have become more sophisticated and highly integrated, patterns have become more precise, and the masks and wafer chips used in these devices also need to be more precise. be done.

Particularly in the case of semiconductor devices, photolithography technology, in which patterning is performed using light, is used in many manufacturing steps, and there are many types of photomasks used for this.

If the pattern surface of this photomask is scratched for some reason, or if there is a white defect in a black positive pattern, the defective portion of the photomask will appear directly on the patterned semiconductor wafer surface. Particular care must be taken in the inspection of

However, due to the higher performance and higher integration of semiconductor integrated circuits, the patterns patterned on photomasks are becoming more precise, so inspection using only a conventional microscope is time-consuming and can overlook defects on the surface of the pattern. There is a need for improvement of the inspection method.

(c) Prior art and problems The conventional photomask inspection method inspects a mask called a reticle. If the original plate is about 10 times the size and the reticle is perfect and free of defects, it will be reduced in size and used to produce a practical photomask.

There are mainly two types of inspection methods for defects on the patterned surface of this reticle.The first method is to inspect multiple patterns using the fact that the pattern on the reticle surface is repeated. This is a method of inspecting patterning figures by superimposing identical reticle and comparing them.

In this case, the surface of the reticle is scanned with a magnifying glass, the image is converted into an electrical signal by an image sensor, and the signal is input to an imaging device to create a graphic.The inspection is performed by visually observing the patterning of this graphic surface. be exposed.

The second method is to compare data patterns input into a computer.

In this method, the reticle to be inspected is scanned with a video camera, the video signal is converted to a digital signal, and then input to a magnetic tape MT, and this data is compared with the designed MT.

However, both of these methods have drawbacks; in the first comparison method that utilizes the repeatability of patterning, when a common defect exists on the pattern surfaces of multiple overlapping retakes, the defect is The method of comparing with the second data pattern has the drawbacks of the complexity of creating the data pattern and the difficulty of creating data exactly the same on the actual pattern surface.

(d) Purpose of the Invention In view of the above-mentioned conventional drawbacks, the present invention provides a method for detecting defects on the pattern surface of a photomask used for semiconductor devices, etc. A new inspection method that detects negative parts as defects when there is a negative part with dimensions smaller than the minimum pattern figure that makes up the mask improves the accuracy of photomasks and makes it easier to inspect the pattern surface of the reticle. The purpose is to provide a method.

(e) Structure of the Invention According to the present invention, it is an object of the present invention to inspect a positive pattern composed of a minimum design rectangle, which is a unit of minimum pattern design, using a mask inspection device;
In a pattern inspection method for detecting negative defects existing within the positive pattern, the dimensions of the minimum design rectangle are registered in advance in the mask inspection device, and the dimensions of the negative portion existing within the positive pattern are registered. This can be achieved by providing a mask inspection method characterized in that a negative portion having a size smaller than the size of the minimum design rectangle is detected as a negative defect when compared with the size of the minimum design rectangle.

(f) Embodiments of the Invention The present invention is a method for detecting a defective portion by inspecting a defective portion included in a positive pattern figure of a reticle mask. exists as a negative white, so by inputting a predetermined rectangle that can determine this defect into the inspection device, the negative white defect in the positive pattern figure of the mask to be inspected can be determined as described above. When it is larger than a predetermined rectangle, it is determined that there is no defective part, and conversely, when it is smaller than a predetermined rectangle, it is determined that there is a defective part.

This is because the mask pattern is generally a combination of minimum pattern figures, such as minimum rectangles, that is, repetition, so if the minimum rectangle is the prescribed rectangle above, it is normal for there to be a white part within that rectangle. This is based on the idea that it cannot occur in a certain pattern.

FIG. 1 is a block diagram of a mask inspection apparatus according to the present invention, in which 1 is a reticle mask for an object to be inspected, 2 is an identification system for illuminating the object to be inspected, and 3 is an optical system that displays the pattern of the mask. 4 is a light receiving system that is converted into an optical signal by an image sensor or the like.

This optical signal is received by the light receiving signal device 5, and the A of 6
- The waveform is shaped by the D converter, converted to the bit memory 7, and input to the image processing device 8. For this image processing, a signal from a predetermined rectangular image signal device 9 is input in advance. In order to
These two are compared and the comparison result is sent to the detection device 10.
will be displayed.

FIG. 2 is a block diagram of a detection method in an image processing device, in which a scanning signal 11, a reference signal 12,
The block including the AND circuit 13 and the counter 14 is a block showing the function of the A-D converter 6, and the block including the first memory circuit 15 and the second memory circuit 17 is a block showing the function of the bit memory 7, and a comparison circuit. 18 is a block showing the function of the image processing device 8, a block including a predetermined rectangular pattern register 16 is a block showing the function of the image signal device 9, and an abnormal value detection device 1.
9, a block including X-Y stage position information 20, XY overlapping coordinate information 21, an AND circuit 22, and a margin setting signal 23 is a block indicating the function of the detection device 10. Reference numeral 11 denotes a scanning signal that scans the reticle mask with a plurality of scanning lines, and the negative portion is at a high level and the positive portion is at a zero level. 12 is a constant pulse wave reference signal, and 11 scanning signals are converted into pulses by 13 AND circuits.

14 is a counter which counts the number of scanned pulses for each scanning line and outputs the number of scanned pulses to the first memory circuit 1.
At the same time, pulses at the start of scanning and at the end of scanning are input to this memory by a trigger from the scanning signal.

Reference numeral 16 denotes a predetermined rectangular pattern figure register that is initially set, and a signal is pulsed corresponding to a predetermined dimension (for example, the minimum rectangular dimension).

17 is a second memory circuit, in which only the initial value from the counter 14 is written.

18 is a comparison circuit that compares information from the first memory circuit 15 and information from the second memory circuit 17, and compares information from the first memory circuit 15 and a predetermined rectangular pattern figure register 16.
The abnormal value detection device 1 compares the information from
9, but at the same time, the X-Y stage position information 20 and the XY overlap coordinate information 21 are ANDed.
It is input via circuit 22.

Also, in this case, it is necessary to have a certain margin in order to judge it as an abnormal value, so 2.
The margin setting signal No. 3 is input, and the test result with the margin added is detected as an output.

FIGS. 3A to 3E are waveforms of the above example,
In the block diagram of FIG. 2, these parts are indicated by corresponding symbols.

FIG. 4 shows a specific example of scanning when it is assumed that there is a negative defect portion 26 in the positive pattern figure of the reticle mask 25, and the defect portion is smaller than a predetermined square 27.

In scanning, the reticle mask is divided into multiple areas as shown in the figure, and each area is scanned. For example, if the scanning area is divided into a, b, c, d, and e and scanned, the scanning signal (the (corresponding to A in Figure 3) is the fourth
It will look like Figure 2. The signals of the scanning signal are represented by the signals corresponding to the scanning area of FIG. 41.

Each of the scanning signals a, b, c, d, and e is continuous because there is no defect in the length direction of the reticle mask, but the scanning signal c is continuous at zero level in the positive pattern part because there is no negative defect. However, since there is a negative defect in the scanning signal c, the level becomes high only by the length of the defect area.

The reference signal (corresponding to B in FIG. 3) is shown in FIG. 5, and by ANDing it with the waveform shown in FIG. 4, the signal of the negative defect portion can be made into a pulse.

(g) Effects of the Invention As explained in detail above, by employing the reticle mask inspection apparatus of the present invention, a method for easily and reliably detecting negative defects in positive pattern figures can be provided. There is something. There are some things that are very effective. Although the present invention relates to negative defects within a positive pattern, it is clear that the present invention can be similarly applied to positive defects within a negative pattern by reversing the positive and negative patterns.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an inspection apparatus according to the present invention. Second
The figure is a block diagram of the image processing detection method. FIG. 3 is a waveform diagram of the above embodiment. Figure 4 is a waveform signal diagram. Fifth
The figure shows a reference signal diagram. In the figure, 1 is the reticle mask, 2 is the illumination, and 3 is the reticle mask.
is an optical system, 4 is a light receiving system, 5 is a light receiving signal, 6 is A-
D converter, 7 is a bit memory, 8 is an image processing device, 9 is an image signal device, 10 is a detection device, 11 is a scanning signal, 12 is a reference signal, 13 is an AND circuit,
14 is a counter, 15 is a first memory circuit,
16 is a predetermined rectangular pattern figure register;
17 is a second memory circuit, 18 is a comparison circuit, 1
9 is an abnormal value detection device, 20 is X-Y stage position information, 21 is XY overlapping coordinate information, 22
is an AND circuit, 23 is a margin setting signal, 25 is a reticle mask, 26 is a negative defect area, 2
7 is a rectangle with predetermined dimensions.

Claims (1)

[Claims] 1 In a pattern inspection method in which a positive pattern consisting of a minimum design rectangle, which is the unit of minimum pattern design, is inspected by a mask inspection device and negative defects existing in the positive pattern are detected, the dimensions of the minimum design rectangle are It is registered in the mask inspection device in advance, and the dimensions of the negative portion existing in the positive pattern are compared with the registered dimensions of the minimum design rectangle, and the negative portions having dimensions smaller than the dimensions of the minimum design rectangle are detected. A mask inspection method characterized by detecting as a negative defect.