JPH05333532A - Pattern inspecting device - Google Patents

Abstract

PURPOSE:To surely detect a pattern defect having intermediate density at the device for detecting the pattern defect by obtaining a pattern signal and comparing this signal with a reference level. CONSTITUTION:This device is composed of a CCD camera 1 to obtain electric signals corresponding to the pattern density formed on a mask film, first binarizing part 21 to compare the level of the obtained signals with the first reference level biased to the high level side, second binarizing part 22 to compare those signals with the second reference level biased to the low level side, first and second feature extraction parts 31 and 32 to extract the features of the obtained binary signals, judge part 4 to judge the defect from the extracted features, and system control part 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pattern inspection apparatus for detecting a pattern formed on a mask film and inspecting the pattern.

[0002]

2. Description of the Related Art Conventionally, an apparatus having a block structure shown in FIG. 4 has been proposed as an apparatus for inspecting a mask film in which a pattern is formed on a transparent film with a light impermeable material. In the figure, 1 is a CCD camera for picking up an image of a pattern, and 2 is a binarization of an electric signal by comparing the level of an electric signal obtained corresponding to the pattern picked up by the CCD camera 1 with a reference level. Quantizer, 3
Is a feature extraction unit that extracts the feature by comparing the obtained binarized signal with an adjacent signal, and 4 is a determination unit that detects whether the target portion is defective based on the extracted feature. Is. Reference numeral 5 is a system control unit. Regarding the reference level in the binarization unit 2, a signal obtained from a transparent (white) portion where a pattern does not exist has a high level, and a signal obtained from a light opaque (black) portion having a pattern has a low level. Sometimes, the intermediate level between them is used as a reference level, and the detected signal is compared with this reference level to perform binarization.

[0003]

In such a conventional inspection method, dust of intermediate density generated in the non-pattern portion,
When inspecting a defective portion such as a density insufficient portion generated in the pattern portion, if the signals obtained from these defective portions do not reach the reference level, respectively, there is a problem of overlooking this. For example, as shown in FIG. 5A, when the non-patterned portion NP and the patterned portion P have intermediate density defect portions X1 and X2, respectively, the signal level SL obtained along the line S for this pattern is as shown in FIG. 5 (b). Even when the signal level SL is compared with the reference level RL, since the displacement amounts of the signal levels of the defective portions X1 and X2 have not reached the reference level RL, this portion is not detected. The binarized signal DS as shown in FIG. 5C is output. Therefore, the inspection result is output as if there is no defect.

Such a defect portion having an intermediate density is used as a resist (photoresist) used in a photolithography process using this mask film in a subsequent process.
If the sensitivity is stable, the sensitivity falls within the latitude range of the resist, so that there is no particular problem. However, in reality, there is a variation in the sensitivity of the resist, so when the exposure amount through the defect portion of intermediate density is outside the latitude range of the resist, a defect occurs in the corresponding portion of the formed pattern. This causes the problem that the correct pattern shape cannot be transferred. An object of the present invention is to provide a pattern inspection device capable of surely detecting an intermediate density pattern defect.

[0005]

According to the present invention, an electric signal obtained according to the pattern density formed on a mask film is biased to a high level side and a first reference level biased to a low level side. Binarization is performed using each of the two reference levels. A pattern inspection is performed based on the obtained binarized signal. The level difference between the first reference level and the second reference level is set according to the amount of variation in the sensitivity of the photoconductor that performs the photolithography process using the mask film.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of an embodiment of the pattern inspection apparatus of the present invention. In the figure, reference numeral 1 denotes a CCD camera for picking up an image of a pattern of a mask film to be inspected, which outputs an electric signal having a level corresponding to the density of the picked-up pattern. Normally, an electric signal obtained from a transparent non-pattern portion is output as a high level (white level) electric signal, and an electric signal obtained from a light-impermeable pattern portion has a low level (black level) close to zero. It is output as an electric signal. The output of the CCD camera 1 is divided into two, and then input to the first binarization unit 21 and the second binarization unit 22, respectively.

As shown in FIG. 2 showing the signal levels in the binarizing units 21 and 22, the first binarizing unit 21 is closer to the high level side than the intermediate level between the high level HL and the low level LL. The level is set to the first reference level RL1, and the input signal is binarized based on the first reference level RL1. Also, the second binarization unit 22 sets a level closer to the low level side than the intermediate level between the high level HL and the low level LL as the second reference level RL2, and the input signal is used as the second reference level RL2. Binarization is performed based on the level RL2.

The outputs of the binarization units 21 and 22 are input to a first feature extraction unit 31 and a second feature extraction unit 32, respectively, where the level of the portion to be inspected and the level of the adjacent portion are checked. By comparing with, it is detected whether the target portion has a level bias with respect to the adjacent portion. Then, when the portion having such a bias is extracted, the extraction results of the feature extraction units 31 and 32 are input to the determination unit 4. The determination unit 4 is configured as an OR circuit, and when the output from at least one of the feature extraction units is input, the determination unit 4 makes a determination based on a required algorithm to determine whether or not the target portion is defective. It outputs the judgment. This judgment output is input to the system control unit 5 to execute various system controls.

FIG. 3 is a diagram showing an inspection method by the inspection apparatus of FIG. Here, for comparison, the case of the same pattern defect as the conventional example shown in FIG. 5 is shown. That is, FIG.
(A) is a plan view of a mask film in which the non-patterned portion NP and the patterned portion P have intermediate-density defective portions X1 and X2, respectively, and the CCD camera 1 performs pattern detection along a line S. The signals obtained from the CCD camera 1 are each divided into two, and the signal levels SL thereof are respectively divided into a first reference level RL1 and a second reference level RL1 by the first binarization unit 21 and the second binarization unit 22. It is compared with the reference level RL2.

At this time, as shown in FIG. 3B, even when the defect portions X1 and X2 have an intermediate density, the defect portion X1 of the non-pattern portion NP is the first reference level RL1 biased toward the high level side. As a result, the value of the defective portion X1 becomes a value DS1 of the binarized signal different from that of the non-patterned portion NP as shown in FIG. 3 (c1), and as a result, the defective portion can be detected. .. Further, the defect portion X2 of the pattern portion P is compared with the second reference level RL2 biased toward the low level side, so that the value of the defect portion X2 is different from that of the pattern portion P as shown in FIG. 3C2. The value of the binarized signal is DS2, and as a result, it is possible to detect a defective portion.

The binarized signal DL thus obtained
1 and DS2, the first feature extraction unit 31 and the second feature extraction unit 32 perform feature extraction, respectively, and the determination unit 4 performs the determination, so that the intermediate density defect portion X1,
Since the signal value of the portion X2 is clearly different from that of the adjacent portion, as shown in FIG. 3 (d), the signal FO which determines that these portions are defective is output. That is, the defect of each intermediate density is detected as the defect of the non-pattern part and the defect of the pattern part.

As described above, even if the defective portions X1 and X2 occurring in the pattern portion P and the non-pattern portion NP have an intermediate density, it is possible to reliably detect the defective portions without overlooking them. Therefore, as shown in parentheses in FIG. 2, the first reference level RL1 and the second reference level RL2
If the level difference between and is set to a level difference corresponding to the amount of variation in the sensitivity of the resist used in the photolithography process that is a post-process, the sensitivity of the resist to the resist is reduced when the photolithography process as described above is performed. Even if there is variation, it is possible to prevent the occurrence of pattern transfer failure due to the intermediate density portion.

[0013]

As described above, according to the present invention, the means for binarizing the electric signal obtained from the pattern includes the first reference level on the high level side and the second reference level on the low level side. Since the comparison is performed using each of them, it is possible to reliably detect the intermediate density defect portion occurring in the pattern portion or the non-pattern portion. In particular, if the level difference between the first and second reference levels is set in correspondence with the sensitivity variation amount of the resist, it is possible to prevent transfer failure when the pattern transfer is performed using the resist. There is an effect that can be done.

[Brief description of drawings]

FIG. 1 is a block configuration diagram of an embodiment of a pattern inspection apparatus of the present invention.

FIG. 2 is a level diagram showing a relationship between high and low levels of a binarizing unit and first and second reference levels in the present invention.

FIG. 3 is a diagram for explaining pattern binarization in the present invention.

FIG. 4 is a block configuration diagram of an example of a conventional pattern inspection apparatus.

FIG. 5 is a diagram for explaining a conventional pattern inspection method.
FIG.

[Explanation of symbols]

 1 CCD camera 2, 21, 22 Binarization unit 3, 31, 32 Feature extraction unit 4 Judgment unit 5 System control unit RL1 First reference level RL2 Second reference level

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical indication H04N 1/40 103 A 9068-5C

Claims (3)

[Claims] 1. An apparatus for detecting a pattern density formed on a mask film as an electric signal level, binarizing the electric signal level with a reference level, and detecting a pattern defect based on the binarized signal. In the above, the means for performing the binarization is configured to perform the binarization by using the first reference level biased to the high level side and the second reference level biased to the low level side, respectively. A pattern inspection device characterized by. 2. The level difference between the first reference level and the second reference level is set in accordance with the amount of variation in the sensitivity of the photoconductor that performs the photolithography process using the mask film. 1 pattern inspection device. 3. An image pickup means for obtaining an electric signal according to a pattern density formed on a mask film, and a first binary value for comparing the level of the obtained signal with a first reference level biased to a high level side. And the second part that biases the same signal to the low level side
The second binarization unit for comparing with the reference level of
A pattern inspection apparatus comprising: a first and a second feature extraction unit for extracting a feature of a binarized signal; a determination unit for determining a defect from the extracted feature; and a system control unit.