JP2011185793A - Hole-roughness quantification device and hole-roughness quantification method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hole-roughness quantification device and a hole-roughness quantification method that can quantify roughness speedily and accurately without the need to artificially designate areas which should be quantified, when quantifying the roughness of the hole pattern formed on a photomask, or the like. <P>SOLUTION: When the roughnesses of measurement target patterns are quantified from a contour line of measurement target patterns and reference patterns, the present invention calculates the difference between positional coordinates of a plurality of points located on the contour line of the measurement target patterns and positional coordinates of a plurality of balls located on the contour line of the reference patterns and calculates the roughness values of the measurement target patterns, based on the difference distance calculated. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a hole roughness quantification apparatus and a hole roughness quantification method for quantitatively measuring the shape of a hole pattern from a mask pattern image of a photomask used in a lithography process of semiconductor manufacturing.

With recent miniaturization of semiconductor LSI (Large Scale Integration) patterns, photomasks as pattern masters are also required to cope with miniaturization, and at the same time, the demand for higher accuracy is very severe. .
Conventionally, three items of defects, dimensional accuracy, and alignment have been especially emphasized as important items in photomask quality, and high-precision photomasks are currently used to measure and evaluate each item as semiconductors become more miniaturized. Dedicated inspection equipment has been developed.

However, the demand for higher precision by miniaturization of photomask patterns is becoming the same in all quality items (pattern shape, pattern data guarantee, durability, cleanliness, etc.) other than the above three items. Since the accuracy of the pattern shape is directly related to the accuracy and performance of the LSI circuit, it has become more important.
Generally, in mask layout design of a semiconductor circuit, it is desired that a pattern according to a design drawing is accurately reproduced on a mask. However, since a fine pattern is actually processed on a metal thin film on glass using lithography technology, the mask pattern and the design pattern are not completely the same shape. There are significant differences.

This difference is almost as large as several tens to several hundreds of nanometers on the mask. However, due to the recent progress in miniaturization of VLSI, there is concern that this may affect the characteristics of semiconductor circuits. I'm starting. That is, the finer the pattern, the greater the difference in the pattern shape with respect to the pattern itself, which affects the characteristic value.
When a pattern shape is used as an inspection item for mask quality, there are several types. For example, items to be checked for each part of the pattern, such as the roundness of the pattern corner part, the roughness (unevenness) of the linear pattern edge part, the pattern position shift at the time of drawing, the shape distortion, and the taper shape.

On the other hand, the accuracy of the pattern shape has become very important even in a pattern exposed and transferred onto a wafer by a lithography process. In particular, in ArF lithography, since the edge roughness of a pattern affects the electrical characteristics, a technique for quantitatively measuring it has been studied.
Usually, the edge roughness used in the pattern of a photomask and a wafer refers to the unevenness | corrugation of the edge in a linear pattern. However, due to the recent miniaturization of semiconductor LSIs, pattern distortion and roughness have become conspicuous even in closed figures such as squares such as hole patterns and dot patterns, which can affect the final electrical characteristics. There are concerns. In other words, it can be said that there is now a need to quantitatively evaluate edge roughness, which has been considered as a concept applied to linear patterns, even for closed figures such as hole patterns and dot patterns. However, unlike the case of the straight line pattern shown in Non-Patent Document 1, there is currently no clear standard for edge roughness for the hole pattern.

Conventionally, roughness evaluation of photomasks and wafer holes or dot patterns has been performed using optical microscopes (including pattern observation devices such as laser microscopes and confocal microscopes for the purpose of observation at high magnifications) and scanning electron microscopes (SEM: Scanning Electron Microscope) was used to acquire images and visually compare the images.
Further, as another method, as described in Patent Document 1, a contour line can be obtained from a hole or dot pattern image by an image processing technique, and a measurer can measure roughness. The edge roughness was calculated from the variation of the contour of the designated part by designating the part.
However, in the hole or dot pattern roughness confirmation method as described above, the pattern shape cannot be quantitatively evaluated only by qualitative judgment by visual observation using an optical microscope or scanning electron microscope.

On the other hand, there are the following three problems in the method of acquiring the contour line by the image processing method and designating the straight line portion of the pattern that allows the measurer to measure the roughness.
The first problem is that if the position of the straight line to measure roughness is changed, the measurement result may change with the change in position. Is a difficult point.
The second problem is that the hole or dot pattern is composed of a straight line part and a corner part, but if the corner part falls within the specified range, the roughness value will be larger than the actual value. It is. It is very difficult to separate the straight line portion from the corner portion, and it is very difficult to accurately specify only the straight line portion.

The third problem is that the operation of designating the straight line portion of the pattern is complicated. If there is only one pattern to measure, there is no problem, but usually it is necessary to measure many patterns, so it takes a lot of time to specify a straight line for each pattern. End up.
Thus, with the technique disclosed in Non-Patent Document 1 or Patent Document 1, it is difficult to accurately and quickly measure the roughness shape of a hole or dot pattern.

  Therefore, after inputting the measurement target pattern to the measurement target pattern input unit of the apparatus for quantifying the roughness of the hole pattern and the dot pattern, extracting the outline of the measurement target pattern, calculating the center of gravity of the extracted outline, The distance between the contour line and the center of gravity is calculated by the first distance calculating means, and the distance between the contour line of the reference pattern for comparison with the measurement target pattern and the center of gravity of the contour line of the reference pattern is calculated as the second distance. The difference between the distance calculated by the first distance calculating means and the distance calculated by the second distance calculating means is calculated by the difference calculating means, and the measurement target pattern is calculated from the difference calculated by the difference calculating means. There has been proposed a method for calculating the roughness value (see Patent Document 2).

JP 2001-101414 A JP 2007-263899 A

Proc. SPIE 5038, p. 689 (2003)

  According to such a method, it is possible to quantify the roughness level of the hole pattern or the dot pattern without specifying the roughness measurement location by the measurer. However, while the technique disclosed in Patent Document 2 is effective when there are a plurality of patterns in the same SEM image, it is discussed in the case of an isolated pattern (one hole or dot pattern in the SEM image). Not. Further, since the reference pattern for the measurement target pattern is obtained by performing image processing on the pattern having the same shape in consideration of mask manufacturability, it is considered difficult to quantitatively know the deviation from the design pattern.

  The present invention has been made in view of the above circumstances, and its purpose is to artificially specify a location to be quantified when quantifying the roughness of a hole pattern formed on a photomask or the like. An object of the present invention is to provide a hole roughness quantification apparatus and a hole roughness quantification method capable of quickly and accurately quantifying roughness.

  In order to solve the above-mentioned problem, a hole roughness quantifying device according to claim 1 of the present invention is a device for quantifying the roughness of a hole pattern, comprising: a measurement target pattern input means for inputting a measurement target pattern; First contour line extracting means for extracting a contour line of the measurement target pattern, first coordinate calculation means for calculating position coordinates of a plurality of points on the contour line, and a reference for comparison with the measurement target pattern Second coordinate calculating means for extracting the contour line of the pattern and calculating the position coordinates of a plurality of points on the extracted contour line; the position coordinates calculated by the first coordinate calculating means; and the second coordinate calculating means. Difference distance calculation means for calculating a difference distance from the position coordinates calculated in step (b), and a roughness value calculation means for calculating a roughness value of the measurement target pattern from the difference distance. It is characterized by.

  A hole roughness quantification method according to a second aspect of the present invention is a method for quantifying the roughness of a hole pattern, and includes a measurement target pattern input step for inputting a measurement target pattern, and a contour line of the measurement target pattern. Extracting a contour line of a reference pattern for comparison with the measurement target pattern, a first coordinate calculating step for calculating the position coordinates of a plurality of points on the contour line, A second coordinate calculation step of calculating the position coordinates of a plurality of points on the extracted contour line; and a difference between the position coordinates calculated in the first coordinate calculation step and the position coordinates calculated in the second coordinate calculation step A differential distance calculating step of calculating a distance; and a roughness value calculating step of calculating a roughness value of the measurement target pattern from the differential distance.

The hole roughness quantifying method according to claim 3 of the present invention is the hole roughness quantifying method according to claim 2, wherein the second coordinate calculating step adds roundness to round the corner of the reference pattern. A step of extracting a contour line of a reference pattern with rounded corners in the rounding step, and calculating position coordinates of a plurality of points on the extracted contour line.
The hole roughness quantification method according to claim 4 of the present invention is the hole roughness quantification method according to claim 3, wherein when the difference distance is calculated in the difference distance calculation step, the measurement target pattern The difference distance is calculated using a diagonal intersection of a contour line and a diagonal intersection of a contour line of the reference pattern as a reference point.

  According to the present invention, when the roughness of the measurement target pattern is quantified from the measurement target pattern and the reference pattern outline, the position coordinates of the plurality of points located on the measurement target pattern outline and the reference pattern outline are positioned. Calculating the difference distance from the position coordinates of multiple points to be calculated and calculating the roughness value of the measurement target pattern based on the calculated difference distance to calculate the center of gravity position of the outline of the measurement target pattern or reference pattern Since it is not necessary to calculate the distance between the calculated center of gravity position and the contour line, when the roughness of the hole pattern formed on the photomask or the like is quantified, the part to be quantified is manually specified. Roughness can be quickly quantified without any problems.

In addition, after rounding the corners of the reference pattern, by extracting the contour line of the reference pattern, the contour line of the extracted reference pattern becomes a shape that substantially matches the contour line of the measurement target pattern. Since the difference distance can be calculated by matching the diagonal intersection of the contour line of the measurement target pattern and the diagonal intersection of the reference pattern contour line, the roughness of the hole pattern formed on the photomask can be accurately quantified. .
Furthermore, when calculating the difference distance in the difference distance calculation step, the difference distance is accurately calculated by calculating the difference distance using the diagonal intersection of the contour line of the measurement target pattern and the diagonal intersection of the contour line of the reference pattern as a reference point. Since it can be calculated, the roughness of the hole pattern formed on the photomask or the like can be quantified more accurately.

It is a block diagram which shows the structure of the hole roughness quantification apparatus which concerns on one Embodiment of this invention. It is a figure which shows an example of the outline of the measurement object pattern extracted by the hall | hole roughness quantification apparatus which concerns on one Embodiment of this invention. It is a figure which shows an example of the outline of the reference pattern extracted by the hall | hole roughness quantification apparatus which concerns on one Embodiment of this invention. It is a figure which superimposes and shows the outline of the measurement object pattern extracted by the hall | hole roughness quantification apparatus which concerns on one Embodiment of this invention, and the outline of a reference pattern. It is a figure which shows an example of the difference distance information calculated by the hall | hole roughness quantification apparatus which concerns on one Embodiment of this invention. It is a flowchart for demonstrating the roughness value calculation process of the hall | hole roughness quantification apparatus which concerns on one Embodiment of this invention. It is a flowchart for demonstrating the reference pattern outline extraction process of the hall | hole roughness quantification apparatus which concerns on one Embodiment of this invention.

Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
FIG. 1 shows a schematic configuration of a hole roughness quantification apparatus according to an embodiment of the present invention. In the figure, reference numeral 10 denotes a hole roughness quantification apparatus according to an embodiment of the present invention. The hole roughness quantification apparatus 10 includes a measurement target pattern input unit 11, a contour line extraction unit 12, a coordinate calculation unit 13, and a coordinate calculation. Unit 14, difference distance calculation unit 15, roughness value calculation unit 16, and display unit 17.

  The measurement target pattern input unit 11 serving as a measurement target pattern input unit is, for example, a 256 gradation bitmap image obtained by observing a hole pattern of a photomask with a scanning electron microscope or an optical microscope. It is for inputting as a pattern. The measurement target pattern input to the measurement target pattern input unit 11 is supplied to the contour line extraction unit 12 as a contour line extraction unit.

  The contour extraction unit 12 extracts the contour a1 (see FIG. 2) of the measurement target pattern supplied from the measurement target pattern input unit 11 by, for example, a general image processing method. The contour line a1 of the measured pattern to be measured is supplied to the coordinate calculation unit 13 as the first coordinate calculation means. If the measurement target pattern is an image acquired from a scanning electron microscope or the like, and it is difficult to extract a contour line by a general image processing method due to the influence of noise, shading unevenness, or the like, Japanese Patent Laid-Open No. 2003-216959 The contour line of the measurement target pattern can be extracted by using a method described in the publication.

The coordinate calculation unit 13 calculates the position coordinates of a plurality of points located on the contour line a1 of the measurement target pattern supplied from the contour line extraction unit 12, and the position coordinates calculated by the coordinate calculation unit 13 are the difference. It is supplied to the difference distance calculation part 15 as a distance calculation means.
The coordinate calculation unit 14 extracts the reference pattern outline a2 (see FIG. 3) for comparison with the measurement target pattern, and calculates the position coordinates of a plurality of points located on the extracted outline a2. The position coordinates calculated by the coordinate calculation unit 14 are supplied to a difference distance calculation unit 15 as a difference distance calculation unit.
For example, a design pattern of a hole pattern is used as the reference pattern of the measurement target pattern, and the reference pattern is input to the coordinate calculation unit 14 from a reference pattern input unit (not shown).

  The difference distance calculation unit 15 calculates a difference distance between the position coordinate of the measurement target pattern calculated by the coordinate calculation unit 13 and the position coordinate of the reference pattern calculated by the coordinate calculation unit 14. For example, the diagonal line of the diagonal line intersection (the point b1 shown in FIG. 2) of the outline a1 of the measurement target pattern and the outline a2 of the reference pattern is preset in a plurality of locations c11, c12, c13,. A difference distance (a difference in distance from the reference point b1 to the coordinate points on the contour lines a1 and a2) is calculated using the intersection (the point b1 shown in FIG. 3) as the reference point b1.

Further, as shown in FIG. 4, the difference distance calculation unit 15 sets the intervals of the points c11, c12, c13,... For obtaining the difference distance as a reference point b1, and a constant angle θ11, θ12,. The difference distance is calculated to be as follows.
The roughness value calculation unit 16 calculates the roughness value of the measurement target pattern based on the difference distance calculated by the difference distance calculation unit 15. For example, the roughness value calculation unit 16 calculates 3σ of the standard deviation σ for the difference distance information shown in FIG. It is configured to calculate a roughness value. The difference distance information illustrated in FIG. 5 indicates a case where the number of data supplied from the difference distance calculation unit 15 to the roughness value calculation unit 16 is 90.

The display unit 17 displays the roughness value calculated by the roughness value calculation unit 16, and includes a display device such as an LCD (Liquid Crystal Display).
6 and 7 are flowcharts for explaining the operation of the hole roughness quantifying apparatus according to the embodiment of the present invention, and the hole pattern roughness value is measured using the hole roughness quantifying apparatus 10 described above. In this case, as shown in step S <b> 1 of FIG. 6, first, a measurement target pattern to be subjected to roughness measurement is input to the measurement target pattern input unit 11 of the hole roughness quantification apparatus 10.

  At this time, the measurement target pattern input to the measurement target pattern input unit 11 has its contour a1 extracted by the contour extraction unit 12 of the hole roughness quantification apparatus 10 (step S2) and extracted by the contour extraction unit 12. The position coordinates of a plurality of points on the contour line a1 are calculated by the coordinate calculation unit 13 of the hole roughness quantification apparatus 10 (step S3). At this time, the coordinate calculation unit 13 of the hole roughness quantification apparatus 10 calculates position coordinates in the reference pattern (step S4).

  The calculation of the position coordinates in the coordinate calculation unit 13 uses a design pattern of a measurement target pattern as a reference pattern. Here, the hole design pattern is usually a rectangle with a 90-degree angle, but the actual pattern on the photomask has rounded corners, so the design pattern is rounded as a reference pattern. In step T1 shown in FIG. Then, the contour line a2 of the input reference pattern is extracted in step T2 shown in FIG. 7, and the position coordinates of a plurality of points located on the extracted contour line a2 are calculated in step T3 shown in FIG.

  The roundness of the corners of the design pattern is added using CAD (Computer Aided Design) software. Since the roundness of the corner of the hole varies depending on the size and aspect ratio of the design pattern, the roundness of the pattern for measuring edge roughness is measured in advance to confirm the roundness. The corners of the pattern may have a shape close to a simple circular arc, or may have an elliptical arc shape. When adding roundness to the corner of the design pattern using CAD software, information on the roundness of the corner is used. For example, if the corner of the pattern is close to an arc, enter the radius information of the corner, and if the corner of the pattern is close to the arc of an ellipse, enter the vertical and horizontal lengths of the corner. Generate an ideal reference pattern with the same roundness as the pattern.

  When the position coordinate information of the reference pattern is generated in step S4 shown in FIG. 6, the difference distance calculation unit 15 of the hole roughness quantification apparatus 10 and the position coordinate information of the measurement target pattern generated in step S3 and step S4. The generated position coordinate information of the reference pattern is taken in, and the difference distance between the position coordinate information of the measurement target pattern and the position coordinate information of the reference pattern is calculated (step S5).

At this time, the difference distance calculated by the difference distance calculation unit 15 is supplied to the roughness value calculation unit 16 of the hole roughness quantification device 10 as, for example, difference distance information as shown in FIG. Based on the difference distance information calculated by the difference distance calculation unit 15, a roughness value (variation in the difference distance information shown in FIG. 5) is calculated (step S6).
The difference distance data shown in FIG. 5 is supplied from the difference distance calculation unit 15 to the roughness value calculation unit 16, and as a result, the roughness value calculated by the roughness value calculation unit 16 is 6.05 nm.

  As in the above-described embodiment of the present invention, when quantifying the roughness of the measurement target pattern from the measurement target pattern and the reference pattern outline, the position coordinates of a plurality of points positioned on the measurement target pattern outline and the reference By calculating the difference distance from the position coordinates of multiple points located on the contour line of the pattern, and calculating the roughness value of the measurement target pattern based on the calculated difference distance, the contour line of the measurement target pattern or the reference pattern Since there is no need to calculate the center of gravity position or the distance between the calculated center of gravity position and the contour line, it is necessary to artificially determine the locations that should be quantified when quantifying the roughness of hole patterns formed on photomasks, etc. Roughness can be quickly quantified without specifying it manually.

  Further, as in the embodiment of the present invention described above, the reference pattern outline is extracted after rounding the corners of the reference pattern, so that the extracted reference pattern outline becomes the outline of the measurement target pattern. As shown in FIG. 4, the diagonal intersection point b1 of the contour line of the measurement target pattern and the diagonal intersection point b1 of the reference pattern contour line can be matched to calculate the difference distance. The roughness of the hole pattern formed on the photomask or the like can be accurately quantified.

  Furthermore, when calculating the difference distance between the position coordinates of a plurality of points located on the contour line of the measurement target pattern and the position coordinates of the plurality of points located on the contour line of the reference pattern as in the embodiment of the present invention described above. In addition, by calculating the difference distance using the diagonal intersection of the contour line of the measurement target pattern and the diagonal intersection of the reference pattern contour line as a reference point, the difference distance can be accurately calculated. Pattern roughness can be quantified more accurately.

DESCRIPTION OF SYMBOLS 10 ... Hole roughness quantification apparatus 11 ... Measurement object pattern input part 12 ... Contour extraction part 13 ... Coordinate calculation part 14 ... Coordinate calculation part 15 ... Difference distance calculation part 16 ... Roughness value calculation part 17 ... Display part

Claims (4)

An apparatus for quantifying the roughness of a hole pattern,
A measurement target pattern input means for inputting a measurement target pattern;
First contour line extracting means for extracting a contour line of the measurement target pattern;
First coordinate calculating means for calculating position coordinates of a plurality of points on the contour line;
A second coordinate calculating unit that extracts a contour line of a reference pattern for comparison with the measurement target pattern, and calculates position coordinates of a plurality of points on the extracted contour line;
Difference distance calculation means for calculating a difference distance between the position coordinates calculated by the first coordinate calculation means and the position coordinates calculated by the second coordinate calculation means;
A roughness value calculating means for calculating a roughness value of the measurement target pattern from the difference distance;
A hall roughness quantification apparatus characterized by comprising: A method for quantifying the roughness of a hole pattern,
A measurement target pattern input process for inputting a measurement target pattern;
A first contour line extracting step of extracting a contour line of the measurement target pattern;
A first coordinate calculation step of calculating position coordinates of a plurality of points on the contour line;
Extracting a contour line of a reference pattern for comparison with the measurement target pattern, and calculating a position coordinate of a plurality of points on the extracted contour line; and
A difference distance calculating step of calculating a difference distance between the position coordinates calculated in the first coordinate calculating step and the position coordinates calculated in the second coordinate calculating step;
A roughness value calculating step of calculating a roughness value of the measurement target pattern from the difference distance;
A method for quantifying hole roughness characterized by comprising:   The second coordinate calculation step includes a rounding step for rounding the corners of the reference pattern, and extracts the contour line of the reference pattern with rounded corners in the rounding step, and the extracted contour 3. The hole roughness quantification method according to claim 2, wherein position coordinates of a plurality of points on the line are calculated.   When calculating the difference distance in the difference distance calculation step, the difference distance is calculated using a diagonal intersection of a contour line of the measurement target pattern and a diagonal intersection of a contour line of the reference pattern as a reference point, The hole roughness quantification method according to claim 3.

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