JPS5855550B2 - Pattern inspection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pattern inspection method for highly accurately detecting black spot defects present in image patterns, particularly near edges.

Conventionally, there are two methods for inspecting exposure mask patterns of integrated circuits (ICs): one method is to detect the pattern part and the additional air area area, and the other is to detect only the pattern part, excluding the air area area. .

What is needed in the air area is the defect state near the pattern edge, and black spot defects and the like in distant areas do not pose much of a problem.

Therefore, it is clear that the former method detects excessive defects because it also detects unnecessary airspace parts.
In the latter method, the length may not be able to be measured with high accuracy due to the shape of the angle or quantization fluctuation near the pattern edge portion.

SUMMARY OF THE INVENTION An object of the present invention is to provide a pattern inspection method for detecting black spot defects existing near the edges of an image pattern with high accuracy.

In order to achieve the above object, the pattern inspection method of the present invention stores an image pattern as a binary signal on a two-dimensional register, and scans the inspection pattern relative to the test pattern on the register. In a pattern inspection method that extracts information from a register and inspects the vicinity of a pattern edge, the inspection pattern includes a black spot detection pattern consisting of a plurality of linear bits and a plurality of guard patterns arranged on both sides of the pattern to prevent false detection in the vicinity of edges. It is characterized by including.

The present invention will be described in detail below with reference to examples.

FIG. 1 is an explanatory diagram showing the configuration of an embodiment of the present invention.

In the figure, a pattern to be inspected 2' formed on an exposure mask 2 is scanned with a laser beam 1, and the transmitted light is sent to a photodetector 3.
A two-dimensional shift register 4 is arranged in n columns x m columns corresponding to scanning.
A binary signal pattern corresponding to the scanning pattern is formed on the surface of the two-dimensional shift register 4 by manually inputting one end of the signal and shifting the signal using the clock from the clock generation circuit 5.

The surface of this two-dimensional shift register 4 has the following 8
Test pattern in direction, i.e. 0°, 90-180°
, 270° test pattern and 45°, 135°.

Inspection patterns of 225° and 315° are set, and when the bit element corresponding to this pattern changes sign with the input of the pattern signal to be inspected, the mutual I/black and white relationship is determined by the logic circuit of the processing circuit 6. The state of the edge of the pattern to be taken out is inspected through the OR circuit 30.

FIGS. 2a and 2b show an example of an inspection pattern formed in advance on the surface of the two-dimensional shift register 4 shown in FIG. 1, and FIG.

Inspection patterns are arranged in directions of 90°, 180°, and 270°, and test patterns are arranged in directions of 45°, 135°, 225°, and 315°.

That is, as shown in FIG. 2A, black spot detection patterns 111 and 112 are formed of a plurality of linear bits in a 90° direction perpendicular to a pattern edge 10 formed in a 0° direction;
The first card pattern 12. consists of 3 bits on both sides of the center. ．． 122 and a second guard pattern 13. ．． Consists of 13°.

The figure shows a pattern edge 10 formed in a 135° direction.
Sunspot detection pattern 1 formed in a 45° direction perpendicular to
14.11□ and the first guard pattern 12. ．． 12□
In addition to the second guard patterns 131 and 132, the third guard patterns 141 and 142 are composed of a plurality of bits in the 0° and 90° directions.

Among these, the black spot detection pattern detects pattern edges and indicates the length of the black spot part of the pattern in the scanning direction, and the guard pattern prevents false detection at pattern bends near the detection pattern edge, and prevents detection in unspecified angular directions. This is to prohibit the detection of

For this reason, a normal test pattern is determined for each detection bit of the test pattern based on the following three detection conditions.

(1) The black spot detection patterns 111 and 112 detect pattern edges to indicate the start of detection, and the length of the black spot pattern in the scanning direction is indicated by black spot detection.

(2) Guard patterns 121, 122 and 141°1
42, each group includes one or more white bits.

(3) Guard patterns 131 and 132 have the same sign.

That is, when detecting a test pattern edge, if there is a bent part or angular direction in the vicinity that may cause erroneous detection, the guard pattern prohibits erroneous detection and prohibits angles other than the designated angle.

FIG. 3 shows the two-dimensional shift register 4 in FIG.
The test pattern shown in b is set.

Then, the following codes are given to the bit elements of each pattern.

Sunspot detection pattern 11t+ 112: S1 to Sn, D
, K guard pattern 12. ．． 12□; GA1~GA
3° GB1 to GB3 guard patterns 134, 132; Gc, GD guard patterns 141, 142; GE, to GEo.

GF1″GFn Normal pattern edge direction is 0°, 45″′, 9
0'.

Since the directions are limited to 8 directions: 135°, 180°, 225°, 270°, and 315°, the same pattern as in Figure 2 a can be used at 0°.
.

900.180°, 270°, 45 patterns of the same figure
°.

If set to 135°, 225°, and 315°, it can be applied to all pattern edges.

FIG. 4 shows an example of a detection circuit that realizes the detection conditions explained in FIGS. 2a and 2b.

That is, D belonging to the black spot detection pattern 112 of the inspection pattern is detected directly, K is detected via the NOT circuit 21,
Next, since the guard patterns 121 and 122 have the same sign when normal, Go and GD are manually input to the EXNOR 22, and if normal, it will be ``1''; if abnormal, it will be ``O''.

Guard pattern (GA1-GA3)13. .

(GBt'''B3)132, (GEt~GEn)1
4tt (Gp1 to GFn) 142 contains one or more white bits in normal operation, so NAND circuits 23, 24, 26°2
7 is detected, and if it is normal, it will be 1", and if it is abnormal, it will be 0".

Sunspot detection pattern 11. S1 to Sn are the outputs of the OR circuit 25 because they are black point detections.

Among the above logic circuits, the logical product of the group A satisfies the detection condition for the test pattern shown in Figure 2a, and the logical product of the group A+B satisfies the detection condition for the test pattern shown in Figure 2a. So, if this result is 1'', is it normal? T
If it is Of+, it is determined to be defective.

Further, by logically ORing the outputs of each inspection pattern using the OR circuit 30 using the processing circuit 6 shown in FIG. 1, it can be seen that there is a defect in one or more of the eight directions.

FIGS. 5a to 5c are drawings showing the effect of the guard pattern, which is a feature of the inspection pattern used in the present invention.

FIGS. 2A and 2B show an example in which the inspection pattern of FIGS. 2A and 2B was used to inspect a case where the test pattern had an uneven portion in a part of a right-angled bent corner, as indicated by a bold line.

As shown in figure a, for the thick line test pattern 10,
When the test pattern shown in FIG. 2a is set, the guard pattern 122 becomes completely black, so the detection circuit shown in FIG.
0'', indicating a defect.

If these guard patterns 121 and 122 are not present, there is a risk of false detection.

The figure shows the case where the test pattern in Figure 2 outside the specified angle is applied to the test pattern indicated by the thick line.As the guard pattern 14□ becomes completely black, the detection circuit in Figure 4 is similarly 09', indicating a defect or detection prohibited.

Without this, false detection will occur.

Figure C is an example in which the exposed pattern has a recess in a part of the right-angled bent protrusion, and when the inspection pattern in Figure 2a is applied to this part, the guard patterns 13□ and 13□ have different signs. This indicates that the detection circuit of FIG. 4 has a °00 par defect.

As explained above, according to the present invention, the combination of the linear black spot detection pattern and the guard patterns arranged on both sides allows the detection of curved parts near the pattern edge that may cause false detection, and in directions other than the specified angle. Since it is possible to automatically exclude normal pattern edges, it is possible to detect only normal pattern edges with high precision.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram showing the configuration of an embodiment of the present invention, Fig. 2a
, b is an explanatory diagram of a test pattern used in the present invention, FIG. 3 is a detailed explanatory diagram of the shift register of FIG. 1, FIG. 4 is an explanatory diagram of a detection circuit for detecting the test pattern of the present invention, and FIG. 5 a-
c is an explanatory diagram of the effect of the guard pattern of the inspection pattern of the present invention, in which 1 is the laser beam, 2 is the test pattern,
3 is a photodetector, 4 is a shift register, 5 is a clock generation circuit, 6 is a processing circuit, 11. ．． 112 is a black spot detection pattern; 124, 12°, 13. ．． 13□, 14° 142 is guard pattern, 21 is NOT circuit, 22 is EXNOR
The circuits 23, 24, 26, and 27 are NAND AND circuits and OR circuits, and 28 is an AND circuit.

Claims (1)

[Scope of Claims] 1. An image pattern is stored as a binary signal on a two-dimensional register, and information is taken out from the register so as to scan the test pattern relative to the test pattern on the register. A pattern inspection method for inspecting the vicinity, characterized in that the inspection pattern includes a black spot detection pattern formed by a plurality of linear bits and a plurality of guard patterns arranged on both sides of the pattern to prevent erroneous detection near edges. pattern inspection method. 2. The pattern inspection method according to claim 1, wherein the inspection pattern is set in eight directions at 45° intervals with respect to the scanning direction of the pattern to be inspected.