KR101865338B1 - Apparatus for measuring critical dimension of Pattern and method thereof - Google Patents

Abstract

The present invention relates to a linewidth measuring apparatus for measuring a critical dimension of a circuit pattern formed along one surface of a substrate made of a light-transmitting material, and a method of measuring linewidth using the same. The linewidth measuring apparatus of the present invention includes a substrate supporting unit, a first illuminating unit, a reflecting unit, an image acquiring unit, and a control unit. The linewidth measuring method of the present invention includes a horizontal adjusting step, And a line width calculating step. According to the present invention, the light irradiated toward the substrate is regularly reflected by the reflecting portion, the light reflected by the reflecting portion is picked up by the image capturing portion, and an image in which a pair of light and dark boundary lines are formed with reference to both sides of the inclined face of the circuit pattern is obtained And the line width of the circuit pattern is calculated by measuring the distance between the light and dark boundary lines of the pair.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a line width measuring apparatus,

The present invention relates to a line width measuring apparatus and a line width measuring method using the same, and more particularly, to a line width measuring apparatus and a line width measuring method thereof that irradiate light onto a circuit pattern formed on a substrate made of a light transmitting material, And a line width measuring method using the line width measuring apparatus.

Dense integrated circuit patterns are formed on various kinds of adhesive tapes such as display panels, semiconductors and LED chips, and adhesive tapes such as COF (Chip On Film) tape and TAB (Tape Automated Bonding) tape by various processes such as photolithography process and etching process .

It is essential to measure circuit patterns precisely in order to inspect poor substrates where electrical shorts (interconnection), breaks, top notch, etc. occur between circuit patterns. Electrical characteristics are checked or the line width of the circuit pattern is measured to confirm whether a circuit pattern is formed with an accurate dimension before or after the circuit pattern forming process.

1 is a schematic view of a conventional line width measuring apparatus and an image obtained therefrom.

Referring to FIG. 1, a conventional line width measuring apparatus includes a substrate S having a circuit pattern P spaced apart from a lower portion of the substrate S to irradiate light toward the substrate S, (I) obtained by the image acquiring section (20) spaced from the upper part of the image (S) and obtains the distance (R) between the pair of light and dark boundary lines (L) And the line widths W1 and W2 of the circuit pattern P can be calculated. The line widths W1 and W2 of the circuit pattern P corresponding to the distance R between the light and dark boundary lines L are determined by the circuit pattern P attached to the substrate S as shown in an enlarged view in (a) The width W1 of the upper surface of the circuit pattern P or the width W2 of the lower surface of the circuit pattern P.

The conventional linewidth measuring apparatus is configured such that the light irradiated by the illumination unit 10 is blocked on the lower surface of the circuit pattern P and thus the lower surface of the circuit pattern P and the surface of the substrate S on which the circuit pattern P does not exist The difference in contrast between the upper surface of the circuit pattern P and the tilted surface adjacent to the circuit pattern P is not clear on the image I, It is difficult to accurately measure the line width (specifically, the width W1 of the upper surface of the circuit pattern).

That is, whether or not a part of the upper surface of the circuit pattern P is cracked and deleted, whether or not the line width W1 of the upper surface of the circuit pattern P is formed to be smaller than a predetermined reference, ) Could not be confirmed whether or not the top surface was formed with a desired shape along a certain path. As a result, the substrate S of good quality could not be produced.

Korean Registered Patent No. 10-1135241 (Registered on April 04, 2012, entitled Micro Lines Width Measurement Apparatus of Mask)

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a line width measuring apparatus capable of clearly discriminating whether or not a substrate is defective by measuring a line width of a circuit pattern formed on a substrate, Method.

According to an aspect of the present invention, there is provided a linewidth measuring apparatus for measuring a critical dimension of a circuit pattern formed on a surface of a substrate made of a light transmitting material, A substrate support for supporting a back surface of the substrate; A first illumination unit spaced apart from one surface of the substrate and irradiating light toward the substrate; A reflecting portion interposed between the substrate and the substrate supporting portion to reflect light emitted from the first illuminating portion; The direct light that is emitted from the first illumination unit toward the upper surface of the circuit pattern is reflected on the upper surface to exhibit the first brightness and is reflected by the reflection unit to be advanced to the inclined surface of the circuit pattern The second reflected light reflected by the reflective portion and proceeding to the coplanar surface where the circuit pattern does not exist is reflected by the first brightness and the second brightness, An image acquisition unit for acquiring an image representing a third luminance higher than luminance; And a distance between a pair of first light and dark boundary lines caused by a difference in brightness between the first brightness and the second brightness or between a pair of second light and dark boundary lines caused by a difference in brightness between the second and third brightnesses. And a controller for calculating a line width of the circuit pattern by measuring a distance of the circuit pattern.

In the line width measuring apparatus according to the present invention, the first illuminating unit may be a truncated ring illumination arranged along the periphery of the image acquiring unit, and the light irradiated from the first illuminating unit may meet at an arbitrary focus.

The line width measuring apparatus according to the present invention may further include a parallelism adjusting unit interposed between the substrate and the reflecting unit to adjust a parallelism of the substrate and having a surface roughness of a predetermined value or more in contact with the substrate; As shown in FIG.

The line width measuring apparatus according to the present invention may further include a coaxial light source disposed outside the image capturing unit and irradiating the coaxial light toward the image capturing unit, a mirror for converting the coaxial light irradiated from the coaxial light source toward the substrate, And a second illumination unit including the illumination unit.

In the linewidth measuring apparatus according to the present invention, the controller may measure a slope of the circuit pattern by calculating a ratio of a distance between the first and second light-shield boundary lines to a predetermined thickness of the circuit pattern .

According to an aspect of the present invention, there is provided a line width measuring method for measuring a critical dimension of a circuit pattern formed on a surface of a substrate made of a light transmitting material, A light irradiation step of irradiating light toward the substrate so as to meet each other at an arbitrary focal point; Wherein the first reflection light reflected by the slope of the circuit pattern at the reflection portion reflecting the light passing through the substrate is diffusedly reflected on the slope surface Wherein the second reflected light reflected by the reflective surface of the reflective portion has a third brightness higher than the first brightness and the second brightness, An image acquisition step And a distance between a pair of first light and dark boundary lines caused by a difference in brightness between the first brightness and the second brightness or between a pair of second light and dark boundary lines caused by a difference in brightness between the second and third brightnesses. And calculating a line width of the circuit pattern by measuring a distance of the circuit pattern.

In the line width measuring method according to the present invention, when the brightness of the image is less than the reference value, the coaxial light source provided in the image capturing unit irradiates the coaxial light to the substrate, The height may further include a brightness adjusting step.

In the line width measuring method according to the present invention, before the light irradiation step, the parallelism of the substrate disposed on the reflective portion is measured, the upper surface is cut so as to have a parallelism opposite to the measured parallelism, And a horizontal adjustment step of interposing a parallelism adjusting part between the substrate and the reflection part.

According to the line width measuring apparatus of the present invention and the line width measuring method using the same, the line width of the circuit pattern (specifically, the distance between the first and the second boundary lines) can be measured clearly and the inclination degree of the circuit pattern can be measured .

Further, according to the line width measuring apparatus and the line width measuring method using the line width measuring apparatus of the present invention, it is possible to produce a high quality substrate by covering the defective substrate by using the measured line width or slope degree.

Further, according to the linewidth measuring apparatus and the line width measuring method using the same of the present invention, light can be intensively irradiated to a certain region of the substrate to obtain a bright and bright image, and an image obtained by the image acquiring unit is distorted Can be prevented.

In addition, according to the line width measuring apparatus and the line width measuring method using the line width measuring apparatus of the present invention, the image obtained by the image acquiring unit can be prevented from being distorted by correcting the inclination of the substrate.

Also, according to the line width measuring apparatus and the line width measuring method using the line width measuring apparatus of the present invention, the substrate having the line width measured can be smoothly separated by the parallelism adjusting unit.

According to the line width measuring apparatus and the line width measuring method using the same of the present invention, when the line width is difficult to measure due to the darkness of the image, the line width of the circuit pattern is more clearly measured can do.

1 is a schematic view of a conventional line width measuring apparatus and an image obtained therefrom,
FIG. 2 is a schematic view of a line width measuring apparatus according to an embodiment of the present invention and an image obtained therefrom,
3 is an enlarged partial enlarged view of the portion "A" in Fig. 2,
FIG. 4 is a view for explaining that the parallelism of the substrate is adjusted by the parallelism adjusting unit in the line width measuring apparatus of FIG. 2,
5 is a partially enlarged view for explaining the definition of the inclination of the circuit pattern in the linewidth measuring device of FIG. 2,
6 is a block diagram illustrating a process of a linewidth measuring method according to an embodiment of the present invention.

Hereinafter, a linewidth measuring apparatus according to an embodiment of the present invention and a line width measuring method using the same will be described in detail with reference to the accompanying drawings.

3 is a partially enlarged view showing an enlarged portion of the "A" portion of FIG. 2, and FIG. 4 is a cross-sectional view of the line width measuring apparatus according to the embodiment of FIG. FIG. 5 is a partial enlarged view for explaining the definition of the inclination of the circuit pattern in the line width measuring apparatus of FIG. 2; FIG. And FIG. 6 is a block diagram illustrating a process of a linewidth measuring method according to an embodiment of the present invention.

2 to 6, the linewidth measuring apparatus according to an embodiment of the present invention measures a critical dimension of a circuit pattern formed along one surface of a substrate made of a light transmitting material, A first illumination unit 200, a reflection unit 300, an image acquisition unit 400, and a control unit (not shown).

The substrate supporting part 100 supports the back surface of the substrate S on which the circuit pattern P is not formed, as shown in FIG. The substrate support 100 is sufficient for a rigid body having low reactivity and constant rigidity with respect to the substrate S to be contacted, and its material is not particularly limited.

The first illumination unit 200 irradiates light toward the substrate S from the first surface of the substrate S. A variety of light sources such as incandescent lamps, fluorescent lamps, LEDs, sodium lamps, and ceramic metals can be applied to the first illumination unit 200. However, since the first illumination unit 200 has excellent energy efficiency, long life, Suitable.

The first illumination unit 200 is arranged along the periphery of the image acquisition unit 400 described later and is formed of a truncated ring illumination in which light irradiated from the first illumination unit 200 meets each other at an arbitrary focus. This is because the first illumination unit 200 illuminates the field of view of the image acquisition unit 400 in order to acquire a brighter image and a lighter image I by intensively irradiating a certain region of the substrate S with light. This prevents image distortion such as flare (the appearance of the light source on the image) / blooming (the image of the light source appears on the image) / smear (the image appears white on the image) . Thus, the line widths W1 and W2 of the circuit pattern P can be accurately measured and the reliability of the measurement can be increased.

The reflective portion 300 is interposed between the substrate S and the substrate supporting portion 100 to reflect light emitted from the first illumination portion 200. A flat mirror may be used to reflect the light regularly, or a metal film having high reflectivity may be used for the reflection unit 300.

2 or 3, the image capturing unit 400 is spaced apart from the first illumination unit 200 and is disposed on the upper surface P1 of the circuit pattern P in the first illumination unit 200 The direct light M1 is reflected by the upper surface P1 of the circuit pattern P to indicate the first luminance and is reflected by the reflective portion 300 to be incident on the circuit pattern P as the first reflected light M2 Is a second reflected light M3 which is diffused to the sloped surface P2 and exhibits a second luminance different from the first luminance and which is reflected by the reflective portion 300 and proceeds to the coplanar surface A1 in which the circuit pattern P does not exist, (I) representing the third luminance higher than the first luminance and the second luminance.

The third reflected light M4 reflected by the reflecting portion 300 and traveling toward the lower surface of the circuit pattern P is blocked by the lower surface P3 of the circuit pattern P.

The image acquiring unit 400 may be an ordinary electron microscope or an optical microscope having a CCD camera or the like that enlarges the image of the original image I at a constant magnification. Although not shown, the image I generated by the image acquisition unit 400 can output pixel data or vector data of the image I to the control unit through an image output unit (not shown) It can be stored in memory.

For reference, luminance is a measure of the degree of brightness per unit area of light, and is the surface brightness of the light-transmitting surface or the reflecting surface, and the unit is cd / m ^ 2.

The direct light M1 may have a luminance higher than the second luminance in the first luminance of the direct light M1 or vice versa depending on the reflectance of the upper face P1 of the circuit pattern P. [

The first reflected light M2 is reduced in a predetermined ratio in a process of being diffusedly reflected on the inclined plane P2 to appear as a constant brightness (second brightness) on the image I.

The second reflected light M3 passes through the coplanar surface A1 on which the circuit pattern P does not exist and proceeds to the image capturing unit 400 without loss of brightness so that the second reflected light M3 appears brightest (third brightness) on the image I .

2 (b), due to the difference in luminance between the first luminance and the second luminance, a pair of the first and second luminance signals P 1 and P 2, which correspond to the boundary between the upper face Pl and the sloped face P 2 of the circuit pattern P, 1 contrast boundary line L1 appears in the image I and the slope P2 of the circuit pattern P and the circuit pattern P do not exist due to the luminance difference between the second luminance and the third luminance A pair of second light-shielding boundary lines L2 corresponding to the boundary of the coplanar surface A1 of the first and second light-shielding surfaces S are formed in the image.

The controller measures the line widths W1 and W2 of the circuit pattern P shown in Fig. 5 by measuring the distance R1 between the pair of first light-shielding boundary lines or the distance R2 between the pair of second light- . The control unit compares the distance R1 between a pair of first light and dark boundary lines displayed on the image I or the distance R2 between a pair of second light and dark boundary lines displayed on the image I using the pixel data or vector data transmitted from the image output unit, And the line widths W1 and W2 of the circuit pattern P are calculated.

At this time, the controller calculates the ratio of the distances d1 and d2 between the first and second light-shielding boundary lines L1 and L2 and the thickness t of the predetermined circuit pattern to calculate the inclination degree of the circuit pattern P &thetas;).

As described above, in the line width measuring apparatus of the present invention, since the contrast of the circuit pattern P is clearly contrasted with respect to the first and second boundary lines L1 and L2, the line width of the circuit pattern P W1) between the first and second light boundary lines of the pair can be clearly measured and can be measured up to the inclination (?) Of the circuit pattern (P).

When the value of the measured line width W1 or W2 or inclination degree is out of the reference range, a part of the upper surface P1 of the circuit pattern P is broken and lost or the upper surface P1 of the circuit pattern P The line width W1 of the circuit pattern P does not satisfy the minimum reference width or the line width W2 of the lower surface P3 of the circuit pattern P exceeds the maximum reference width or the upper surface P1 of the circuit pattern P Is not formed in a desired shape along a predetermined path, it is possible to determine whether the circuit pattern P is defective or not, so that it is possible to detect a defective substrate S and to produce a substrate S of good quality do.

The line width measuring apparatus of the present invention may further include a parallelism adjusting unit 500 and a second illumination unit 600.

The parallelism adjusting unit 500 is interposed between the substrate S and the reflecting unit 300 to adjust the parallelism? 'Of the substrate S as shown in FIG. 3 or 4, Is made of a light-transmitting material having a surface roughness of at least a certain value.

The parallelism adjusting unit 500 measures the parallelism (specifically, the slope with respect to the X, Y, and Z axes,? ') Of the substrate S disposed on the reflecting unit 300 with respect to the reference plane B1 , And a surface is cut or cut so as to have a parallelism (-θ ') opposite to the measured parallelism (θ'), and is interposed between the substrate S and the reflective portion 300.

When the substrate S is tilted to one side due to the machining tolerance and the assembly tolerance, the parallelism? Of the substrate S is corrected to be parallel to the reference plane B1 by the wedge- It is possible to prevent the image I obtained by the image acquisition unit 400 from being distorted.

The surface of the parallelism adjusting part 500 has a surface roughness equal to or greater than a certain value, which can provide the following additional effects.

If the surface of the parallelism adjusting part 500 on which the substrate S is placed is smoothly processed, a vacuum state is established between the parallelism adjusting part 500 and the substrate S, and the substrate S is adjusted in parallel As shown in FIG. Therefore, it is difficult to separate the substrate S having the line widths W1 and W2 measured by the parallelism adjusting unit 500, and the substrate S having a small thickness may be damaged by the external force during the separation process. In addition, a difference in charge distribution, that is, a force due to static electricity acts between the parallelism adjusting unit 500 and the substrate S. Even if the size of the static electricity is large, the substrate may be broken during the process of separating the substrate.

In contrast, in the present invention, since the plurality of grooves 501 are formed so that the surface of the parallelism adjusting part 500 has a surface roughness, even if the substrate S is placed on the surface of the parallelism adjusting part 500, The vacuum is not formed between the parallelism adjusting part 500 and the substrate S. Since the contact area between the parallelism adjusting part 500 and the substrate S is greatly reduced, the size of the static electricity acting between the parallelism adjusting part 500 and the substrate S is also reduced. Therefore, the above-described problems can be solved.

2, the second illuminating unit 600 includes a coaxial light source 610 disposed outside the image capturing unit 400 to emit the coaxial light M5 toward the image capturing unit 400, And a mirror 620 for converting the coaxial light M5 emitted from the light source 610 to be directed toward the substrate S.

When the brightness of the image I acquired by the image acquisition unit 400 is less than the reference value, the coaxial light source 610 provided in the image acquisition unit 400 irradiates the coaxial light M5 toward the substrate S. Thus, The brightness of the image I is increased by the brightness capable of measuring the line widths W1 and W2. Thus, the line widths W1 and W2 of the circuit pattern P can be measured more clearly.

The linewidth measuring apparatus according to an embodiment of the present invention configured as described above measures line widths W1 and W2 of the circuit pattern P through the following process, that is, a linewidth measuring method. Referring to FIG. 6,

(S2: light irradiation step)

The light irradiation step S2 is a step of irradiating light toward the substrate S so as to meet each other at an arbitrary focus using a ring-shaped ring illumination.

(S1: leveling step)

The horizontal adjustment step S1 may be further included before the light irradiation step S2.

The horizontal adjustment step S1 measures the parallelism? 'Of the substrate S disposed on the reflective portion 300 that reflects light, and calculates a parallelism?' 'Opposite to the measured parallelism?' ), Or a step of providing a parallelism adjusting part (500) in a cut shape and interposing the parallelism adjusting part (500) between the substrate (S) and the reflecting part (300) to be.

The parallelism? 'Of the substrate S can be measured by a physical measurement method such as a horizontal system or an optical measurement method of irradiating a beam such as infrared rays toward a target object and calculating a phase difference of a reflected beam .

(S3: image acquisition step)

In the image capturing step S3, the direct light M1 proceeding to the upper surface P1 of the circuit pattern P is reflected on the upper surface P1 to exhibit the first luminance, reflected by the reflector 300, The first reflected light M2 proceeding to the sloped surface P2 of the reflective portion 300 is irregularly reflected on the inclined surface P2 to show the second luminance different from the first luminance, The second reflected light M3 reflected by the coplanar surface A1 is a step of obtaining an image I representing a first brightness and a third brightness higher than the second brightness.

When the brightness of the obtained image I is less than the reference value in the process of performing the image acquisition step S3, the coaxial light source 610 provided in the image acquisition unit 400 moves the coaxial light M5 toward the substrate S. [ And a brightness adjusting step S3a for increasing the brightness of the image I so that the brightness of the image I is increased. That is, when it is difficult to discriminate the line widths W1 and W2 due to darkness of the image I, the image I is brightened through the brightness adjustment step S3a.

(S4: line width calculating step)

The line width calculating step S4 calculates the line width of each of the pair of first light-shielding boundary lines R1 and / or the pair of first and second brightness / And the line widths W1 and W2 of the circuit pattern P are calculated by measuring the distance R2 between the second light and dark boundary lines of the circuit pattern P. [

At this time, the ratio of the distance (d1, d2) between the first and second light-shielding boundary lines to the thickness t of the predetermined circuit pattern P is calculated and measured simultaneously to the inclination degree of the circuit pattern P can do. The apparatus may further include a failure determination step of determining whether the calculated line widths W1 and W2 and the inclination degrees are out of the reference range and determining the failure of the substrate S according to the deviation.

The line width measuring apparatus of the present invention constructed as described above and the line width measuring method using the line width measuring apparatus of the present invention clearly compares the lightness and darkness of each circuit pattern region with respect to the first and second boundary lines, The distance between the light and dark boundary lines) can be clearly measured, and the effect of measuring the inclination degree of the circuit pattern can be obtained.

In addition, the line width measuring apparatus of the present invention constructed as described above and the line width measuring method using the same can judge whether the measured line width or slope value deviates from the reference range, The effect can be obtained.

In addition, the line width measuring apparatus of the present invention constructed as described above and the linewidth measuring method using the same are capable of concentrating the light on a certain region of the substrate by using a ring- It is possible to obtain a clear and bright image and prevent the image obtained by the image acquiring unit from being distorted by preventing the illumination from being directly exposed to the field of view of the image acquiring unit.

In addition, the line width measuring apparatus of the present invention configured as described above and the line width measuring method using the same can obtain the effect of preventing the image obtained by the image obtaining unit from being distorted by correcting the inclination of the substrate through the parallelism adjusting unit have.

Further, the line width measuring apparatus of the present invention constructed as described above and the line width measuring method using the apparatus have the surface roughness of the upper surface of the parallelism adjusting unit, so that the substrate having the line width measured can be smoothly separated from the parallel- Effect can be obtained.

Further, in the line width measuring apparatus and the line width measuring method using the same according to the present invention, when the line width is difficult to measure due to the darkness of the image, the line width of the circuit pattern is increased It is possible to obtain an effect that can be more clearly measured.

The scope of the present invention is not limited to the above-described embodiments and modifications, but can be implemented in various forms of embodiments within the scope of the appended claims. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the appended claims.

100:
200: first illumination unit
300:
400:
500: parallelism adjusting section
600: second illumination unit

Claims (8)

A line width measuring apparatus for measuring a critical dimension of a circuit pattern formed along one surface of a substrate made of a light transmitting material,
A substrate supporting part for supporting a back surface of the substrate on which the circuit pattern is not formed;
A first illumination unit spaced apart from one surface of the substrate and irradiating light toward the substrate;
A reflecting portion interposed between the substrate and the substrate supporting portion to reflect light emitted from the first illuminating portion;
The direct light that is emitted from the first illumination unit toward the upper surface of the circuit pattern is reflected on the upper surface to exhibit the first brightness and is reflected by the reflection unit to be advanced to the inclined surface of the circuit pattern The second reflected light reflected by the reflective portion and proceeding to the coplanar surface where the circuit pattern does not exist is reflected by the first brightness and the second brightness, An image acquisition unit for acquiring an image representing a third luminance higher than luminance; And
A distance between a pair of first light and dark boundary lines caused by a difference in brightness between the first brightness and the second brightness or a distance between a pair of second light and dark boundary lines caused by a difference in brightness between the second brightness and the third brightness And a control unit for calculating a line width of the circuit pattern by measuring a distance. The method according to claim 1,
Wherein the first illumination unit is arranged along the periphery of the image acquisition unit and is a truncated ring illumination in which the light emitted from the first illumination unit meets at an arbitrary focus. The method according to claim 1,
And a parallelism adjusting unit formed of a light transmitting material interposed between the substrate and the reflector to adjust a degree of parallelism of the substrate and having a surface roughness equal to or greater than a predetermined value in contact with the substrate. Device. The method according to claim 1,
And a second illuminating unit disposed on the outside of the image acquiring unit and coaxially illuminating the coaxial light toward the image acquiring unit and a mirror for converting the coaxial light irradiated from the coaxial light source toward the substrate Wherein the line width measuring device is a line width measuring device. The method according to claim 1,
Wherein the control unit measures the inclination of the circuit pattern by calculating a ratio of a distance between the first light-shield boundary line and the second light-darkness boundary line to a predetermined thickness of the circuit pattern. A line width measuring method for measuring a critical dimension of a circuit pattern formed along one surface of a substrate made of a light transmitting material,
A light irradiation step of irradiating light toward the substrate so as to meet each other at an arbitrary focal point by using a first illumination unit which is a ring-shaped ring illumination;
Wherein the first reflection light reflected by the slope of the circuit pattern at the reflection portion reflecting the light passing through the substrate is diffusedly reflected on the slope surface Wherein the second reflected light reflected by the reflective surface of the reflective portion has a third brightness higher than the first brightness and the second brightness, An image acquiring step of acquiring an image using an image acquiring unit spaced apart from the first illuminating unit; And
A distance between a pair of first light and dark boundary lines caused by a difference in brightness between the first brightness and the second brightness or a distance between a pair of second light and dark boundary lines caused by a difference in brightness between the second brightness and the third brightness And a line width calculation step of calculating a line width of the circuit pattern by measuring a distance. The method according to claim 6,
In the image acquisition step,
Further comprising: a brightness adjustment step of increasing the brightness of the image by causing the coaxial light source provided in the image acquisition unit to irradiate the coaxial light toward the substrate when the brightness of the image is less than the reference value. The method according to claim 6,
Prior to the light irradiation step,
A horizontal adjustment step of measuring a degree of parallelism of the substrate disposed on the reflective part, cutting the upper surface to have a parallelism opposite to the measured parallelism, and interposing a parallelism adjusting part made of a light transmitting material between the substrate and the reflecting part The method further comprising the step of:

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