JPS63314402A - Inspection method for mask pattern - Google Patents

Abstract

PURPOSE:To detect and confirm all of a plurality of sizes in a simple arrangement and in a short period of time by comparing the absent time or present time of a passing light with a predetermined time through sweeping of a light spot having smaller width than a fixed width at constant speeds. CONSTITUTION:A light source 4 for generating a light spot 3 is positioned opposite to a light detector 5 which detects the light coming from the light spot 3 and converts the same into signals. A mask pattern is placed between the light source 4 and the light detector 5, so that the mask pattern is irradiated by the slight spot 3 while the light spot is moved in a direction parallel to light shield regions 2 relatively at constant speeds. At this time, the light spot 3 is arranged to be smaller in width than the light shield region 2 of the mask pattern. Then, the light detector 5 detects only the light passing through between the light shield regions 2 and converts the detected light into signals indicating the presence of the passing light. The signals are periodic pulse signals. Therefore, the periodic pulse signals are sent, through a signal discriminator circuit 6, to a comparison circuit 7 in which two among the period, the rest time and the continuous time are compared in every cycle with a reference time generated by a reference setting circuit 8. The result of the comparison is indicated by an acceptance/rejection display circuit 9.

Description

[Detailed Description of the Invention] [Summary] In the inspection of a mask pattern in which a large number of light-shielding areas of a constant width are arranged at regular intervals (equal pitch), a light spot smaller than the above-mentioned constant width is scanned and irradiated at a constant speed, and the presence or absence of transmitted light is detected. By comparing the time with a predetermined time and detecting defective mask patterns, reliable inspection can be easily performed.

[Industrial application field]

The present invention relates to a method for inspecting a mask pattern, which targets a mask pattern in which a large number of light-shielding areas of a constant width are arranged at equal intervals.

2. Description of the Related Art In photolithography technology used in the manufacture of semiconductor devices, a photomask having a mask pattern formed in a light-shielding area is used, and the mask pattern is transferred onto a substrate to process the substrate.

In addition, the mask pattern of this photomask can be formed by direct drawing with a beam such as electron beam exposure, or
It is formed by transferring a mask pattern of a reticle formed in a similar manner.

Therefore, since the mask pattern created on the photomask or reticle becomes the basis for substrate processing, it is desirable to perform reliable inspection to ensure accuracy.

Among the mask patterns, there are mask patterns in which a large number of light-shielding areas of a certain width are lined up at equal intervals for use in memory areas of CCDs (charge-coupled devices), ICs (integrated circuits), etc. The same applies to patterns.

[Prior Art and Problems to be Solved by the Invention] A mask pattern in which a large number of light shielding areas of a constant width are arranged at equal intervals is as shown in the plan view of FIG. 3, for example.

In the figure, the mask pattern is on the glass substrate 1.
N light-shielding regions 2 with a width dimension a are arranged at equal intervals with a pitch dimension b (N is several hundred to several thousand), and the total length l becomes ff = b (N-1) + a, and the light-shielding regions It is formed with the aim of making all the gap dimensions C between the two the same.

The width dimension a, the interval dimension C1, and the overall length dimension β are all required to fall within predetermined tolerances.

Therefore, in order to reliably inspect the quality of this mask pattern, it is necessary to measure all of the above dimensions.

Conventionally, such dimensional inspection has been carried out by measuring dimensions using a microscope.

For this reason, in the above-mentioned mask pattern inspection, there are many measurement points and the measurement time is extremely long.

Therefore, a simplified method is sometimes adopted in which the width dimension a and the interval dimension b (gap dimension C) are measured by sampling, and if the dimensions of the measurement location are good, it is considered to be good from a probabilistic perspective. , cannot be a reliable test.

[Means for solving problems]

The above problem is solved by irradiating a mask pattern with a large number of light-shielding areas of a certain width arranged at equal intervals with a light spot smaller than the certain width while moving relatively at a constant speed in the direction of the arrangement, and detecting the transmitted light. The inspection method of the present invention detects a defective mask pattern by comparing any two of the period, pause time, and duration of the signal with a predetermined time. solved by.

[Effect]

The individual cycles of the above-mentioned signals are proportional to the individual intervals of a large number of light-shielding regions, and change according to changes in the intervals. Then, if the above rest time is assumed to be no transmitted light, each rest time changes according to the change in the width of each light-shielding area, and each of the above-mentioned duration times changes according to the change in the individual gaps between the light-shielding areas. and change.

Therefore, if the method of the present invention is adopted, the width of the shaded areas, the interval between the shaded areas, or the shading time can be determined in advance by determining the pause time for the width of the shaded areas (or the duration for the gap between the shaded areas). It is now possible to judge the quality of all gaps between regions (width dimension a2 interval dimension or gap dimension C shown in Figure 3) much more easily and in a shorter time than in the case of the conventional method. It can be done reliably and easily.

〔Example〕

Examples of the method of the present invention will be described below with reference to the configuration diagram in FIG. 1 and the waveform diagram in FIG. 2.

In FIG. 1, a light source 4 that emits a light spot 3 and a photodetector 5 that detects the light that becomes the light spot 3 and converts it into a signal are placed facing each other, and a mask as described in FIG. 3 is placed between them. The light spot 3 is caused to irradiate the mask pattern while moving at a relatively constant speed in the direction in which the light shielding areas 2 are lined up through the pattern. Further, at that time, the size of the light spot 3 is made smaller than the width of the light shielding area 20 of the mask pattern.

Here, the width dimension a of the light-shielding region 2 is 5 μm, and the light-shielding region 2
For a mask pattern with an interval dimension of 10 μm (therefore, a gap dimension C between the light-shielding regions 2 of 5 μm), the size of the light spot is 4 μmφ, and the above-mentioned moving speed is 0.5 to 21 cm. /second.

Then, the photodetector 5 detects only the transmitted light that has passed between the light shielding areas 2, and the signal becomes a pulse when the transmitted light is present, and becomes a periodic pulse signal as shown in FIG.

Then, this signal passes through the discrimination circuit 6 and enters the comparison circuit 7, and for each cycle, two of the period, rest time, and duration are compared with the reference time from the reference setting circuit 8, and the result is determined as good or bad. A judgment is made and displayed by the pass/fail display circuit 9.

The discrimination circuit 6 converts the signal shown in FIG.
(shown by a chain line), and for each period, period B,
Two of the pause time A and the duration C are determined. Then, the individual pause times A, the individual periods B, and the individual durations C each correspond to the individual width dimensions a of the light shielding area 2.
, the individual gap dimensions b, and the individual gap dimensions C between the light-shielding regions 2, and the following relationship holds true.

a=k(A+α) Δa=k (ΔA) c=k(C-α) Δc=k (ΔC) b=a+c=k (A+C) =, BΔb=k
(ΔB) However, k is a proportionality constant determined by the above-mentioned moving speed, and α is a constant determined by the level of binarization level 10. Therefore, the above-mentioned moving speed and pause time A for width dimension a (or duration time for gap dimension C) ) by measuring the proportionality constant and the constant α, then by finding two of the pause time A, period B, and duration C for each period,
It becomes possible to determine all of the individual width dimensions a, the individual spacing dimensions b, and the individual gap dimensions C. .

Therefore, by setting the reference time in the reference time setting circuit 8 for determining the quality by comparing two of the rest time A, the period B, and the duration time C, the width dimension a, the interval dimension or the gap can be set. A defective mask pattern can be detected by detecting a defective dimension existing within the dimension C.

However, the detection is performed while the mask pattern passes between the light source 4 and the photodetector 5.

By adding the inspection of the total length l of the mask pattern to the above inspection, the inspection becomes reliable. Even if the inspection of the total length dimension β is performed using a conventional method, it only takes a short time.

(Thus, reliable inspection of a mask pattern in which a large number of light-shielding areas of a certain width are lined up at equal intervals, that is, an inspection that confirms all of the numerous dimensions, can be performed more easily and in a shorter time than with conventional methods. .

〔Effect of the invention〕

As explained above, according to the configuration of the present invention, when inspecting a mask pattern in which a large number of light-shielding areas of a constant width are arranged at equal intervals, reliable inspection that confirms all of a large number of dimensions can be carried out easily and in a short time. It has the effect of making you do so.

[BRIEF DESCRIPTION OF THE DRAWINGS] Fig. 1 is a block diagram illustrating an embodiment of the method of the present invention, Fig. 2 is a waveform diagram of a signal in the embodiment, and Fig. 3 is a plan view showing an example of a mask pattern. . In the figure, ■ is a glass substrate, 2 is a light shielding area, 3 is a light spot, 4 is a light source, 5 is a photodetector, 6 is a discrimination circuit, 7 is a comparison circuit, 8 is a reference setting circuit, 9 is a pass/fail display circuit,
10 is the binarization level, a is the width dimension, b is the interval dimension, C is the gap dimension, β is the total length dimension, A is the pause time, B is the period, and C is the duration time. ML Seidan No. 1 explaining a sister example of the present melting method
Figure 11 → 7 skin shapes of Iba No. 2 in response to the threat of the end of time
Figure square/7 pattern f) 471'J flat national policy 3
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Claims (1)

[Claims] In a method for inspecting a mask pattern in which a large number of light-shielding areas of a certain width are arranged at equal intervals, a light spot smaller than the certain width is irradiated onto the mask pattern while moving relatively at a constant speed in the direction of the arrangement, and its transmission is It detects light and generates a signal indicating the presence or absence of transmitted light, and compares any two of the period, rest time, and duration of the signal with a predetermined time to detect a defective mask pattern. Featured mask pattern inspection method.