JPH11257940A - Method and apparatus for evaluating pattern - Google Patents

Abstract

PROBLEM TO BE SOLVED: To evaluate the edge roughness of a pattern quantitatively. SOLUTION: Two reference points are selected from an evaluating pattern. Next, the interval between the selected two reference points is divided into one-hundred equal parts, and a one-hundred measuring points are set. Next, each measuring point is scanned by an electronic beam (S1), and a plurality of secondary electronic waveform data obtained are stored respectively (S2). These two-dimensional electronic waveform data are transformed into position coordinates (S3), and a cumulated waveform is obtained by superposition computation processing (S4). Attension is paid to the position of one out of the two peaks of the cumulated waveform, and a waveform larger than some threshold value of the waveform is approximated by a normal distribution function, and edge roughness evaluation is performed from σ-value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pattern evaluation method and a pattern evaluation apparatus for evaluating the contour of a pattern.

[0002]

2. Description of the Related Art With the progress of pattern miniaturization, edge roughness (variation in contour shape) of a resist pattern becomes a serious problem due to deterioration in contrast of absorbed energy distribution near a limit resolution and variation in development speed of resist resin accompanying the deterioration. ing.

The edge roughness of a resist is transferred to a base pattern at the time of etching, and greatly affects the electrical characteristics of a finally formed wiring. For this reason, in the lithography process, it is important to construct a resist process and an etching process with small edge roughness. In order to construct such a process, a means for quantitatively evaluating edge roughness is required.

However, in the conventional observation with an electron microscope, even if the pattern shape can be evaluated and the pattern dimensions can be measured, the edge roughness of the pattern cannot be quantitatively evaluated.

[0005]

As described above, there has been no method for quantitatively evaluating the contour of a pattern. An object of the present invention is to provide a pattern evaluation method and a pattern evaluation device for quantitatively evaluating the contour shape of a pattern.

[0006]

Means for Solving the Problems [Configuration] The present invention is configured as follows to achieve the above object. (1) The present invention (Claim 1) is a pattern evaluation method for evaluating a contour shape of a pattern on an object on which a predetermined pattern is formed. Scanning energy beams in parallel to detect reflected energy from the object to be measured and obtaining a plurality of reflected signal patterns; superimposing the reflected signal patterns to create a superimposed signal pattern; Obtaining the spread of the peak of the pattern and evaluating the contour shape of the pattern. (2) The present invention (Claim 2) is a pattern evaluation method for evaluating a contour shape of a pattern on an object on which a predetermined pattern is formed. Detecting energy reflected from the object by scanning energy rays in parallel, obtaining a plurality of reflected signal patterns, obtaining peak positions of the respective reflected signal patterns, and obtaining a histogram of the obtained peak positions. It is characterized by including a step of creating, and a step of obtaining the spread of the histogram and evaluating the contour shape of the pattern.

Preferred embodiments of the constitutions (1) and (2) are shown below. A longitudinal direction of the pattern is orthogonal to a scanning direction of the energy beam. The coordinate conversion of the reflection signal patterns is performed so that the center positions of the plurality of reflection signal patterns are aligned. (3) The present invention (Claim 5) is a pattern evaluation method for evaluating a contour shape of a pattern on an object on which a predetermined pattern is formed. Extracting the contour of the pattern and determining the contour position of the pattern at a plurality of positions; creating a histogram of the determined contour positions; determining the spread of the histogram and evaluating the contour shape of the pattern And characterized in that:

A preferred embodiment of the configuration (5) is shown below. The coordinates of the pattern are converted according to the longitudinal direction of the pattern in the two-dimensional image. (4) The present invention (Claim 7) is a pattern evaluation apparatus that evaluates the contour shape of a pattern on a device on which a predetermined pattern is formed. Detecting the reflected energy from the measured object by scanning in parallel, obtaining a plurality of reflected signal patterns, superimposing the reflected signal patterns, and generating a superposed signal pattern; and Means for determining the spread of the peak and evaluating the contour shape of the pattern. (5) The present invention (Claim 8) is a pattern evaluation apparatus that evaluates the contour shape of a pattern on an object on which a predetermined pattern is formed. For detecting reflected energy from the object to be measured to obtain a plurality of reflected signal patterns, for obtaining peak positions of the respective reflected signal patterns, and for creating a histogram of the obtained peak positions. And means for determining the spread of the histogram and evaluating the contour shape of the pattern.

Preferred embodiments of the constitutions (4) and (5) will be described below. Means are provided for making a longitudinal direction of the pattern orthogonal to a scanning direction of the energy ray.

Means are provided for performing coordinate transformation of the reflected signal patterns so that the center positions of the plurality of reflected signal patterns are aligned. (6) The present invention (Claim 9) is a pattern evaluation apparatus that evaluates the contour shape of a pattern on an object on which a predetermined pattern is formed, wherein the pattern is evaluated from a two-dimensional image of the object. Means for extracting a contour and determining the position of the contour at a plurality of positions; means for creating a histogram of the determined contour position; means for determining the spread of the histogram and evaluating the contour shape of the pattern It is characterized by becoming.

A preferred embodiment of the configuration (6) is described below. Means for performing coordinate conversion of the pattern in accordance with a longitudinal direction of the pattern in the two-dimensional image.

[Operation] The present invention has the following operation and effects by the above configuration. By obtaining the waveform data on which the reflection signal pattern is superimposed or the spread of the histogram of the contour position, the contour shape of the pattern can be quantitatively evaluated.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. [First Embodiment] FIG. 1 is a schematic diagram showing a schematic configuration of a dimension measuring SEM according to a first embodiment of the present invention.

An electron beam 12 emitted from an electron gun 11 installed in a lens barrel 10 is applied to a wafer 22 on a stage 21 installed in a sample chamber 20. An MC for detecting secondary electrons and reflected electrons is provided in the sample chamber 20.
A P (Micro Channel Plate) 23 is provided. M
The CP 23 controls the control computer 40 via the signal processing unit 31.
Is connected to the waveform storage unit 41 in FIG. Waveform storage unit 41
Are connected to the waveform calculator 42. The stage 21 is connected to a stage control system 43 in the control computer 40. Further, a substrate potential control unit 32 for applying a voltage is connected to the wafer 22. A transfer robot 51, a notch detector 52, and a wafer carrier 53 are provided adjacent to the sample chamber 20.

The accelerating voltage of this SEM is usually 1-2 kV.
And the substrate potential control unit 32
A voltage (retarding voltage) of 00 to 800 V can be applied. The beam resolution is about 2 nm.

Using this apparatus, the edge roughness of the resist pattern formed on the wafer 22 was evaluated. Photoresist coating, exposure and development were performed on a notch type 8-inch Si wafer 22 to form resist patterns for a plurality of chips.

FIG. 2 is a plan view of a chip formed on the wafer 22. FIG. On the chip 60, a roughness evaluation pattern 62 and a rotation adjustment pattern 63 are formed in a region different from the device region 61 in which elements are formed.

Next, the rotation adjustment procedure before the actual evaluation of the edge roughness will be described with reference to the flowchart of FIG. First, the wafer 22 set on the wafer carrier 53 is placed on the transfer robot 51. And
Before the wafer 22 is carried into the sample chamber 20 by the transfer robot 51, the notch detector 52 performs coarse rotation adjustment of the wafer 22 (Step S1).

Next, the wafer 22 after the coarse rotation adjustment is moved onto the stage in the sample chamber 20 by the transfer robot 51 (step S2). After being carried into the sample chamber 20, normal beam adjustment such as focus / astigmatism adjustment is performed using an appropriate pattern on the wafer 22. Observation at a magnification of 100,000 times confirmed that the beam resolution was about 2 nm. Here, the acceleration voltage was 2 kV, and the retarding voltage was 800 V. The operating distance was 5 nm.

Next, the rotation of the wafer 22 is adjusted. The position coordinates and the shape of a relatively large pattern arranged on the chip 60 are input to the control computer 40 in advance using an input device (not shown). Then, two chips 60 located at separate positions in the wafer 22 are specified. The same pattern on the chip 60 at a position distant from the wafer 22 is observed at two locations, the position coordinates are obtained, and the rotation amount of the wafer 22 is calculated (step S3).

Next, the coordinates of the position of the evaluation pattern 62 in the chip 60 and the coordinates of the chip 60 to be measured are input.
The input coordinates are subjected to coordinate conversion according to the previously calculated rotation amount of the wafer 22. Previously calculated wafer 22
The origin of each chip 60 is determined from the rotation amount of the stage control system 4.
The calculation is performed in step 3 (step S4). In this way, even if the wafer 22 is tilted, the stage 2 is positioned at the designated chip 60 and the position of the evaluation pattern 62 in the chip 60.
1 can be moved.

Then, the stage 21 is moved to the position of the evaluation pattern 62 arranged on the chip 60 in this way.
Is moved (step S5). After the adjustment of the apparatus and the rotation adjustment of the wafer described above were completed, the edge roughness of the evaluation pattern 62 was evaluated.

The edge roughness evaluation pattern 62 is a line & space pattern. Magnification 10 when measuring
If you raise it about ten thousand times, the pattern may be inclined. The following correction was performed for the pattern inclination.

The SEM magnification is increased to about 100,000 times, which is the observation magnification, and two upper and lower measurement points 7 of the evaluation pattern 62 are measured.
An electron beam is scanned with respect to 1a and 1b to measure the position 72a and 72b of the edge of the evaluation pattern 62 (FIG. 4).
(A)). Line segment 7 connecting two edge positions 72a and b
The beam scanning direction is rotated so that 3 is perpendicular to the beam scanning direction (FIG. 4B). As a result, the pattern is perpendicular to the scanning direction of the electron beam.

After the adjustment of the wafer rotation and the adjustment of the beam scanning direction were completed, the edge roughness of the evaluation pattern was evaluated. The edge roughness evaluation method will be described with reference to the flowchart of FIG. 5 and FIG.

First, as shown in FIG. 6A, two reference points 81a and 81b are selected from the evaluation pattern 62. Next, 100 points between the two selected reference points 81a and 81b are set.
Divide equally and set 100 measurement points 82. Next, an electron beam is scanned at each measurement point 82 to obtain a plurality of secondary electron waveform data (FIG. 6B) 83. (Step S
1). The plurality of obtained secondary electron waveform data 83 are stored (step S2). The data of the two-dimensional electronic waveform 83 is converted into position coordinates (step S3), and a superposition calculation process is performed to obtain an integrated waveform 84 (FIG. 6C) (step S4).

Attention is paid to the position of one of the two peaks of the integrated waveform 84, and the spread of the integrated waveform 84 is determined. Here, the spread of the portion of the waveform 84 that is equal to or greater than a certain threshold value 85 was evaluated (FIG. 6D). A waveform having a threshold value of 85 or more is approximated by a normal distribution function, and the edge roughness is evaluated from the σ value (step S5).

A value of 5 nm was obtained as a measurement result of the edge roughness together with a measurement result obtained from a normal SEM for dimension measurement. [Second Embodiment] In the first embodiment, the scanning direction of the electron beam is rotated in accordance with the inclination of the pattern. In the second embodiment, however, the edge roughness is quantitatively corrected without correcting the scanning direction of the electron beam. An evaluation was performed. The device used is the same as in the first embodiment.

First, similarly to the first embodiment, two reference points 91a and 91b are set, and then the two reference points 91a and 91b are equally divided by 100 to set 100 measurement points 92. (FIG. 7A). The electron beam is scanned at each measurement point 92 to obtain secondary electron waveform data 93 at each measurement point 92 (FIG. 7B).

Next, the center position of the pattern 62 in each waveform data 93 is determined, and coordinate conversion is performed on each waveform data 93 using the least squares method so that the center of the pattern 62 is aligned (FIG. 7C). ). Next, a peak position 94 of each waveform is obtained from each waveform data after the coordinate conversion, and a histogram 95 of the peak position is created (FIG. 7).
(D)). As in the first embodiment, only a portion above a certain threshold 96 is extracted from the histogram 95. A fitting waveform 97 approximated by a normal distribution function to the extracted portion is obtained. Attention was paid to one edge position in the fitting waveform, and the spread of the signal waveform was determined (FIG. 7E). As a result, similarly to the first embodiment, the measurement result of the edge roughness can be obtained together with the normal dimension measurement result.

[Third Embodiment] FIG. 8 is a schematic diagram showing a schematic configuration of a dimension measuring SEM according to a third embodiment of the present invention. In FIG. 8, the SE for dimension measurement shown in FIG.
The same parts as those of M are denoted by the same reference numerals and description thereof will be omitted.

The SEM for dimension measurement in FIG. 8 has a data input unit 44 for inputting external SEM image data 45 to the two-dimensional image storage device, as compared with that in FIG. In the present embodiment, the coarse rotation adjustment of the wafer and the adjustment of the beam direction in the sample chamber are performed as in the first embodiment. As the evaluation pattern, the resist pattern shown in FIG. 4 was used as in the first and second embodiments.

Next, a method for evaluating edge roughness in this embodiment will be described with reference to the flowchart of FIG. First, an electron beam is applied to the evaluation pattern for 2 seconds.
A two-dimensional image is captured by two-dimensional scanning (step S1).
Next, a process of extracting the contour of the pattern from the captured two-dimensional image is performed (step S2). Here, utilizing the fact that the two-dimensional electron generation amount at the edge of the pattern is large and the intensity distribution of the image data is large, only pixels on the image data having an intensity equal to or greater than the threshold value are extracted. afterwards,
The longitudinal direction of the pattern in the two-dimensional image is x in the rectangular coordinate system.
The coordinates of the pattern are converted so as to be parallel to the axis or the y-axis.

Next, the positions of the contours at a plurality of locations are determined from the image data after the contour extraction processing. Here, the position of the contour of the pattern is obtained for 500 random positions on the image data (step S3). When obtaining the contour position, it is obtained as a distance from the longitudinal line of the pattern. That is, the position of the contour is obtained as the amount of deviation from the longitudinal direction line of the ideal linear pattern.

Next, a histogram of the determined contour positions is formed (step S4). Then, fitting is performed on the histogram using a normal distribution function to obtain a σ value (step S5).

As a result of the above processing, the edge roughness of the resist pattern can be quantified as in the first and second embodiments. Here, a measurement result of 5 nm in edge roughness was obtained together with a normal measurement result of dimensions.

The above processing was performed by the signal operation unit. In the present embodiment, the processing is performed after the acquisition of the two-dimensional image. However, this process can also be performed in an offline process by capturing images of a plurality of samples. For example, image data 45 output in another size SEM can be input to the signal processing unit 41 through the data input unit 44 to evaluate edge roughness.

The present invention is not limited to the above embodiment. For example, in the first embodiment, a reflected signal pattern is obtained without performing adjustment in the beam scanning direction,
After performing coordinate conversion so that the center positions of the obtained reflected signal patterns are aligned, the superimposed signal pattern may be calculated.

In the second embodiment, the reflected signal pattern may be detected after adjusting the scanning direction of the beam to be perpendicular to the longitudinal direction of the pattern, and the peak position of the obtained reflected signal pattern may be obtained. It is possible.

In the above embodiment, the evaluation is performed by applying a voltage to the wafer using an electron microscope for dimension measurement as an evaluation apparatus. However, the present invention is limited to the accelerating voltage of the electronic boom and the substrate potential. is not. For example, the evaluation can be performed without applying a voltage to the wafer, or the evaluation may be performed at an acceleration voltage of 15 kV using an electron microscope for observing a cross section.

The present invention is not limited by the type of the probe of the evaluation device. That is, what is used as the probe may be an evaluation device using light other than the electron beam, for example, a laser beam or X-ray. As a means for acquiring a two-dimensional image, an atomic force microscope (AFM) or a scanning tunneling microscope (STM) can be used.

In the above embodiment, the measurement point is a position obtained by dividing the two reference transitions into 100, but the present invention is not limited by the method of selecting the measurement point.
For example, the measurement points may be set completely randomly between the reference points.

The present invention is not limited by the pattern rotation adjustment method, and other wafer and pattern rotation adjustment methods can be used. Also,
The present invention is not limited by the pattern arrangement method, and it is also possible to arrange a roughness evaluation pattern in a device area. It is also possible to use a pattern in the device area. The present invention can be applied to similar patterns.

In the above embodiment, the fitting is performed using the normal distribution function, and the σ value is applied as the edge roughness, but other parameters may be used. For example, a half width may be obtained as the spread of the distribution and defined as edge roughness.

In the above embodiment, fitting is performed on a signal waveform or a histogram obtained by superimposition using a normal distribution function, but another function may be used. For example, a waveform obtained by a function defined by a user may be fitted. In addition, the present invention
Various modifications can be made without departing from the scope of the invention.

[0046]

As described above, according to the present invention, the contour shape of a pattern can be quantitatively evaluated by evaluating the spread of the waveform data on which the reflection signal pattern is superimposed or the histogram of the contour position. .

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a schematic configuration of a dimension SEM according to a first embodiment.

FIG. 2 is a plan view showing a configuration of a chip.

FIG. 3 is a view for explaining a procedure of a pattern inclination adjusting method.

FIG. 4 is a view for explaining a method of adjusting the inclination of a pattern.

FIG. 5 is an exemplary view for explaining the procedure of a method for evaluating the edge roughness of a pattern according to the first embodiment;

FIG. 6 is a view for explaining a method for evaluating the edge roughness of a pattern according to the first embodiment.

FIG. 7 is a view for explaining a method for evaluating the edge roughness of a pattern according to the second embodiment.

FIG. 8 is a schematic diagram showing a schematic configuration of a dimension measuring SEM according to a third embodiment.

FIG. 9 is a view for explaining a method for evaluating the edge roughness of a pattern according to the third embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Barrel 11 ... Electron gun 12 ... Electron beam 20 ... Sample chamber 21 ... Stage 22 ... Wafer 23 ... MCP 31 ... Signal processing part 32 ... Substrate potential control part 40 ... Control computer 41 ... Waveform storage part 42 ... Waveform calculation part 43 ... Stage control system 51 ... Transfer robot 52 ... Notch detector 53 ... Wafer carrier 60 ... Chip 61 ... Device area 62 ... Roughness evaluation pattern 63 ... Rotation adjustment pattern 71 ... Measurement point 72 ... Edge position 73 ... Line segment 81: Reference point 82: Measurement point 83: Two-dimensional electronic waveform 84: Integrated waveform 85: Threshold value 91: Reference point 92: Measurement point 93: Two-dimensional electronic waveform data

 ──────────────────────────────────────────────────続 き Continued on front page (72) Inventor Waka Sugihara 33, Shinisogo-cho, Isogo-ku, Yokohama-shi, Kanagawa Inside Toshiba Production Technology Laboratory Co., Ltd.

Claims (9)

[Claims] 1. A pattern evaluation method for evaluating a contour shape of an object on which a predetermined pattern is formed, wherein energy beams are scanned in parallel at a plurality of different positions on the object. Detecting the reflected energy from the object to be measured,
A step of obtaining a plurality of reflected signal patterns; a step of superimposing the plurality of reflected signal patterns to create a superposed signal pattern; and a step of obtaining a peak spread of the superimposed signal pattern and evaluating a contour shape of the pattern. A pattern evaluation method comprising: 2. A pattern evaluation method for evaluating a contour shape of a predetermined object formed with a pattern on an object to be measured, wherein energy beams are scanned in parallel at a plurality of different positions on the object. Detecting the reflected energy from the object to be measured,
Obtaining a plurality of reflected signal patterns; obtaining peak positions of the respective reflected signal patterns; creating a histogram of the obtained peak positions; obtaining a spread of the histogram; and evaluating a contour shape of the pattern. And a step of evaluating the pattern. 3. The apparatus according to claim 1, wherein a longitudinal direction of the pattern is orthogonal to a scanning direction of the energy beam.
Or the pattern evaluation method according to 2. 4. The pattern evaluation method according to claim 1, wherein the coordinate transformation of the reflection signal patterns is performed so that the center positions of the plurality of reflection signal patterns are aligned. 5. A pattern evaluation method for evaluating a contour shape of a pattern on an object on which a predetermined pattern is formed, comprising: extracting a contour of the pattern from a two-dimensional image of the object; Determining a contour position of the pattern at a plurality of positions; forming a histogram of the determined contour positions; determining a spread of the histogram and evaluating a contour shape of the pattern. Pattern evaluation method. 6. The pattern evaluation method according to claim 5, wherein coordinate conversion of the pattern is performed in accordance with a longitudinal direction of the pattern in the two-dimensional image. 7. A pattern evaluation apparatus for evaluating a contour shape of a pattern on an object on which a predetermined pattern is formed, wherein energy beams are scanned in parallel at a plurality of different positions on the object to be measured. Detects the reflected energy from the measured object,
Means for determining a plurality of reflected signal patterns, means for superimposing the plurality of reflected signal patterns to create a superposed signal pattern, means for determining the spread of a peak of the superimposed signal pattern, and means for evaluating the contour shape of the pattern A pattern evaluation device comprising: 8. A pattern evaluation apparatus for evaluating a contour shape of a pattern on an object on which a predetermined pattern is formed, wherein energy beams are scanned in parallel at a plurality of different positions on the object to be measured. Means for detecting reflected energy from the object to be measured to determine a plurality of reflected signal patterns; means for determining peak positions of each reflected signal pattern; means for creating a histogram of the determined peak positions; and Means for obtaining a spread and evaluating a contour shape of the pattern. 9. A pattern evaluation apparatus for evaluating a contour shape of a pattern on an object on which a predetermined pattern is formed, wherein the contour of the pattern is extracted from a two-dimensional image of the object to be measured. At a plurality of positions, a means for creating a histogram of the determined contour positions, and means for determining the spread of the histogram and evaluating the contour shape of the pattern. Pattern evaluation device.