KR20080069325A - Method of determining abnormality of apparatus for measuring a thickness of pattern - Google Patents

Abstract

A method for determining an error of a pattern thickness measuring device is provided to measure thickness of a pattern accurately by obtaining a step profile of the pattern and comparing a first noise of a maximum peak region to a second noise of a minimum peak region for judging the error of the pattern thickness measuring device. A method for determining an error of a pattern thickness measuring device comprises the steps: moving a tip of the pattern thickness measuring device along a surface of the pattern(S100); measuring atomic force transmitted from the pattern to the tip and obtaining a step profile of the pattern(S200); and comparing a first noise of a maximum peak region with a second noise of a minimum peak region and judging the error of the pattern thickness measuring device(S300).

Description

Method of Determining Abnormality of Apparatus for Measuring A Thickness of Pattern}

1 is a cross-sectional view showing a pattern thickness meter for measuring the thickness of a pattern according to an embodiment of the present invention.

2 is a flowchart illustrating a method of determining an abnormality of a pattern thickness meter according to an exemplary embodiment of the present invention.

3 is a graph showing a step profile of a steady state measured by a pattern thickness meter.

4 and 5 are graphs showing the step profile of the abnormal state measured by the pattern thickness meter.

Figure 6a is a cross-sectional view showing the depth and width of the step profile according to the wear level of the tip of the pattern thickness meter.

Figure 6b is a graph showing the depth and width of the step profile according to the wear level of the tip of the pattern thickness meter.

Explanation of symbols on the main parts of the drawings

10 semiconductor substrate 12 pattern

100: pattern thickness meter 101: tip

105: cantilever 110: stage

115: electrostatic chuck 120: tip head module

The present invention relates to a method for determining abnormality of a pattern thickness meter, and more particularly, to a method for determining abnormality of vibration and horizontality of a pattern thickness meter.

Recent research on semiconductor devices is progressing toward high integration and high performance in order to process more data in a short time. As the semiconductor substrates become more directly and improved in performance, the spacing between the microstructures and the dimensions of the microstructures, such as patterns of line, space, or contact hole types, continue to decrease.

In general, the patterns formed on the semiconductor substrate are characterized by the technique of forming a thin film, and the technique of forming a thin film on a semiconductor substrate is largely classified into a physical vapor deposition (PVD) method and a chemical vapor deposition (CVD) method. Can be classified.

The thin film deposited on the semiconductor substrate is processed into a predetermined pattern through a lithography process. The deposited thin film includes a lower structure and upper structures formed on the lower structure. As the height of the structures increases, a semiconductor device generates step heights, and it is required to accurately measure the steps and to optimize process conditions accordingly.

Since a fine pattern is formed in the semiconductor device, an atomic force microscope such as a profiler is used to measure the step difference of the fine pattern.

The atomic force microscope is a device that analyzes the surface using the force between atoms, and because it uses the force between the local and tip atoms of the sample, almost all conductors, semiconductors, magnetic materials and dielectrics, regardless of the conductivity of the sample, Samples can be easily observed in air.

The atomic force microscope uses a tip formed at one end of a soft elastic body called a cantilever, and the cantilever is formed to be easily bent up and down by a minute force. Approaching the tip to the sample surface causes the attraction and repulsive force to act on the tip, wherein the atomic force microscope converts this force into an electrical signal using a linear variable differential transformer (LVDT). This signal can be used to obtain three-dimensional information about the sample surface.

However, in the conventional atomic force microscope, there is a problem in that the accuracy and precision of the measurement is inferior because the vibration and leveling of the atomic force microscope are not calibrated or the reliability is not evaluated before the sample surface is measured. .

An object of the present invention is to provide a method for determining abnormality in vibration and horizontality of a pattern thickness meter before measuring the pattern thickness of a sample sample.

In order to achieve the object of the present invention, the abnormality determination method of the pattern thickness meter according to the present invention comprises the steps of moving the tip of the pattern thickness meter along the pattern surface, the atomic force transmitted from the pattern to the tip Measuring to obtain a step profile of the pattern, and comparing the first noise in the highest peak region and the second noise in the lowest peak region shown in the step profile to determine the pattern thickness of the pattern thickness meter. And determining whether or not there is an error.

According to an embodiment of the present disclosure, the determining of the abnormality of the pattern thickness meter may include deriving a ratio of the first noise to the second noise;

The method may include determining whether the pattern thickness meter is vibrating by comparing the ratio value with a preset allowable value. In this case, when the ratio value is smaller than the allowable value, the method may further include comparing each of the first and second noises with noise in a steady state.

According to an embodiment of the present disclosure, the determining of the abnormality of the pattern thickness meter may include comparing the values of the second noises adjacent to the start point and the end point of the highest peak area with each other, thereby comparing the horizontality of the pattern thickness meter. It may include determining whether or not (leveling) abnormality.

In addition, before determining whether the pattern thickness meter is abnormal, the method may further include determining a degree of wear of the tip by comparing the depth and the width of the step from the step profile.

According to the abnormality determination method of the pattern thickness meter according to the preferred embodiment of the present invention configured as described above, by contacting the tip of the pattern thickness meter on the pattern formed on the sample to obtain the step profile of the pattern, And comparing the first noise in the highest peak region with the second noise in the lowest peak region in the stepped profile to determine whether the pattern thickness meter is abnormal.

Thus, the thickness of the pattern can be measured accurately and accurately by determining and correcting whether the vibration of the pattern thickness meter and the level of abnormality are corrected before measuring the step difference of the pattern of the sample sample.

Hereinafter, a method of determining an abnormality of a pattern thickness meter according to an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings. As the inventive concept allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to the specific disclosed form, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention. In describing the drawings, similar reference numerals are used for similar elements. In the accompanying drawings, the dimensions of the structures are shown in an enlarged scale than actual for clarity of the invention.

Terms such as first and second may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprise" or "have" are intended to indicate that there is a feature, number, step, action, component, part, or combination thereof described in the specification, and one or more other features. It is to be understood that the present invention does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, parts, or combinations thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art. Terms such as those defined in the commonly used dictionaries should be construed as having meanings consistent with the meanings in the context of the related art and shall not be construed in ideal or excessively formal meanings unless expressly defined in this application. Do not.

1 is a cross-sectional view showing a pattern thickness meter for measuring the thickness of a pattern according to an embodiment of the present invention.

Referring to FIG. 1, the pattern thickness meter 100 measures heights and steps of circuit patterns 12 formed on the semiconductor substrate 10. For example, the pattern thickness meter 100 may be an atomic force microscope such as a profiler.

The semiconductor substrate 10 is mounted on the stage 110 of the pattern thickness meter 100, and the semiconductor substrate 10 is fixed by the electrostatic chuck 115. While moving the stage 110 laterally, while raising and lowering the tip head module 120 to measure the step formed on the surface of the semiconductor substrate.

 The tip 101 is formed at one end of the cantilever 105 of the tip head module 120, wherein the cantilever 105 is easily bent up and down by a fine force. The tip 101 of the pattern thickness meter 100 moves laterally in contact with the surface of the semiconductor substrate 10. At this time, according to the height of the pattern 12 on the semiconductor substrate to detect the nuclear power delivered to the tip to measure the height of the pattern to atomic units.

2 is a flowchart illustrating a method of determining an abnormality of a pattern thickness meter according to an exemplary embodiment of the present invention. 3 is a graph showing a step profile of a steady state measured by a pattern thickness meter. 4 and 5 are graphs showing the step profile of the abnormal state measured by the pattern thickness meter.

2 and 3, first, a reference sample is placed on the stage 100, and the tip 101 of the pattern thickness meter 100 is moved along the pattern surface formed on the reference sample. S100)

For example, a plurality of line type patterns 12 may be formed on the reference sample. In addition, the patterns 12 may be formed in parallel with each other on the reference sample, or may be formed in directions perpendicular to each other.

Thereafter, an atomic force transmitted from the pattern 12 to the tip 101 is measured to obtain a step profile of the pattern 12 (S200).

The tip 101 moves parallel to the stage 110 along the pattern 12 and between the atoms of the tip 101 and the atoms of the pattern 12 are atomic forces such as attraction and repulsive force to each other. This works. The cantilever 120 is bent up and down by the atomic force, and this displacement is converted into an electrical signal using an LVDT or the like. The converted signal is used to obtain a step profile for the pattern 12 as shown in FIG.

FIG. 3 shows a normal step profile having no abnormality in vibration or horizontality of the stage 110 and the tip 101 of the pattern thickness meter. Referring to FIG. 3, the normal step profile for the pattern 12 includes a peak-height region Rp and a valley-height region Rv.

Noise having a predetermined magnitude is measured in the highest peak area and the lowest peak area. In the steady state where there is no abnormality in vibration or horizontality, the magnitude of the noise has a constant reference noise value (Nref). Further, the step difference of the pattern is measured from the difference value H between the highest peak region and the lowest peak region in a steady state.

Next, by comparing the first noise in the highest peak region and the second noise in the lowest peak region shown in the step profile, it is determined whether the pattern thickness meter 100 is abnormal (S300).

Specifically, whether the vibration of the pattern thickness meter and the horizontality is abnormal is determined by using values of the first noise and the second noise shown in the step profile.

4 is a graph showing a step profile of an abnormal state in which vibration occurs in the stage 110 and the tip 101 of the pattern thickness meter. Referring to FIG. 4, when vibration occurs in the pattern thickness meter, the first noise is measured in the highest peak area, and the second noise is measured in the lowest peak area.

According to one embodiment of the present invention, in order to determine whether vibration of the pattern thickness meter is abnormal, a ratio value of the first noise to the second noise may be derived. Specifically, when the magnitudes of the first and second noises are N1 and N2, respectively, the ratio value is N1 / N2.

Thereafter, the ratio value is compared with a preset allowable value to determine whether the pattern thickness meter is vibrating. The preset allowable value is referred to as 1 + α, and α may be determined to be a predetermined value between 0 and 1.

The pattern thickness measuring instrument compares the ratio value with a preset tolerance value when the ratio value exceeds a preset tolerance range (ie, when N1 / N2> 1 + α, or N1 / N2 <1-α). The vibration abnormality is considered to have occurred.

For example, when α = 0.25 and the first and second noise values are respectively measured as N1 = 3 Hz and N2 = 1 Hz, the ratio value N1 / N2 is three. In this case, since the ratio value N1 / N2 exceeds a preset allowable value 1.25, it may be determined that vibration abnormality has occurred in the pattern thickness meter.

When it is determined that the vibration is abnormal, after calibrating the vibration of the pattern thickness meter, the sample sample is disposed on the stage 110 to measure the thickness of the pattern formed on the sample sample.

According to an embodiment of the present invention, when the ratio value is smaller than the allowable value, the first and second noises are compared with the noise values in a normal state to determine whether the pattern thickness meter is vibrating abnormally. can do.

Specifically, the reference noise value Nref is compared with the values of the first and second noises in the highest peak region and the lowest peak region, respectively. For example, when the values of the first and second noises are included in the normal distribution of the reference noise value (for example, less than 5% of reliability), it is determined that there is no vibration abnormality, and the normality of the reference noise values is determined. If the distribution is exceeded, it may be determined that there is a vibration abnormality.

For example, when α = 0.25 and the first and second noise values are measured as N1 = 3 Hz, N2 = 3.5 Hz, the ratio value of the first noise to the second noise (N1 / N2) Is within the tolerance (1.25). As such, when the ratio value is smaller than the allowable value, it is determined whether the value N1 of the first noise and the value N2 of the second noise are within a normal distribution of the reference noise value Nref. Check it.

Since the value N1 of the first noise is within a normal distribution (less than 5% reliability) of the reference noise value Nref, and the second noise value N2 exceeds the normal distribution of the reference noise value, It can be determined that there is a vibration abnormality of the thickness gauge. In this case, the reliability is less than 5%, preferably less than 1%, more preferably less than 0.3%.

FIG. 5 is a graph illustrating a step profile of an abnormal state in which an abnormality in level between the stage 110 and the tip 101 of the pattern thickness meter occurs. Referring to FIG. 5, when more than a horizontal degree occurs in the pattern thickness meter, the first noise is measured in the highest peak area, and the second noise is measured in the lowest peak area.

According to an embodiment of the present invention, in order to determine whether the pattern thickness meter is more than horizontal, the values of the second noises adjacent to the start point and the end point of the highest peak area are compared with each other to determine the pattern thickness meter. It may be determined whether the leveling is abnormal.

Specifically, the value of the second noise adjacent to the start point of the highest peak region (noise value in region _A : N _A ) and the value of the second noise adjacent to the end point of the highest peak region (in region B). Noise value: N _B ) is measured.

When the difference between the noise value N _A in the region _A and the noise value N _B in the region _B is 0 or within an allowable error range, it may be determined that the horizontality of the pattern thickness meter is not abnormal. Can be.

On the contrary, when the difference between the noise value N _A in the area _A and the noise value N _B in the area _B exceeds the tolerance, it is determined that the horizontality of the pattern thickness meter is abnormal. can do.

In addition, when the value N _A of the noise in the region _A is greater than the noise value N _B in the region _B , it may be determined that the shift to the left occurs. When the value N _A of the noise in the region _A is smaller than the noise value N _B in the region _B , it may be determined that the shift to the right occurs.

If the difference exceeds the tolerance, after calibrating the horizontality of the pattern thickness meter, the sample sample is placed on the stage 110 to measure the thickness of the pattern formed on the sample sample. .

Figure 6a is a cross-sectional view showing the depth and width of the step profile according to the wear level of the tip of the pattern thickness meter. Figure 6b is a graph showing the depth and width of the step profile according to the wear of the tip of the pattern thickness meter. In FIG. 6A, the thick lines on the pattern 12 represent the path of travel of the tip 101 moving along the pattern.

The abnormality determination method of the pattern thickness meter according to an embodiment of the present invention, before determining whether the pattern thickness meter is abnormal, comparing the depth and width of the step from the step profile to determine the degree of wear of the tip It may further include.

6A and 6B, when the step of the pattern is repeatedly measured by the pattern thickness meter, the tip of the pattern thickness meter may wear due to the passage of time according to the repeated measurement.

As the time according to the repeated measurement is gradually increased to t1, t2, t3, t4, accurate measurement becomes difficult due to the wear of the tip. Specifically, the depth of the step measured from the step profile can measure the exact depth until the time t1, t2, t3, but the time can not be measured at the correct depth. In addition, the width of the step measured from the step profile is measured to be narrower as time increases due to wear of the tip.

Therefore, before determining whether the pattern thickness meter is vibrating and having an abnormal level, the tip replacement time may be determined by comparing the depth and width of the step from the step profile to determine the wear level of the tip.

As described above, according to the abnormality determination method of the pattern thickness meter according to the preferred embodiment of the present invention, by contacting the tip of the pattern thickness meter on the pattern formed on the sample to obtain the step profile of the pattern, the step profile And comparing the first noise in the highest peak region with the second noise in the lowest peak region to determine whether the pattern thickness meter is abnormal.

Thus, the thickness of the pattern can be measured accurately and accurately by determining and correcting whether the vibration of the pattern thickness meter and the level of the abnormality are abnormal before measuring the step difference of the pattern of the sample sample.

While the foregoing has been described with reference to preferred embodiments of the present invention, those skilled in the art will be able to variously modify and change the present invention without departing from the spirit and scope of the invention as set forth in the claims below. It will be appreciated.

Claims (5)

Moving the tip of the pattern thickness meter along the pattern surface; Measuring the atomic force transmitted from the pattern to the tip to obtain a step profile of the pattern; And And comparing the first noise in the highest peak region with the second noise in the lowest peak region and determining whether the pattern thickness meter is abnormal by determining the abnormality of the pattern thickness meter. The method of claim 1, wherein the determining of the pattern thickness meter is abnormal. Deriving a ratio value of the first noise to the second noise; And And comparing the ratio value with a preset allowable value to determine whether or not the pattern thickness meter is vibrating abnormally. The pattern thickness meter of claim 2, further comprising comparing each of the first and second noises with noise in a steady state when the ratio value is smaller than the allowable value. Judgment method. The method of claim 1, wherein the determining of the pattern thickness meter is abnormal. And comparing the values of the second noises adjacent to the start point and the end point of the highest peak area with each other to determine whether the pattern thickness meter is at least leveling. Judgment method. The pattern thickness meter of claim 1, further comprising: comparing the depth and width of the step from the step profile to determine the degree of wear of the tip before determining whether the pattern thickness meter is abnormal. Abnormality determination method.

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