JP2005217070A - Pattern collapse measuring method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a pattern collapse measuring method by which the presence or absence of pattern collapse can be found quickly and easily. <P>SOLUTION: The method includes a step wherein a pattern collapse measuring pattern including an evaluation pattern and a fixation pattern is exposed on a resist formed on a wafer, a step to develop the resist, and a step to find the presence or absence of pattern collapse of the evaluation pattern by measuring the change of the position of center of gravity in a pattern collapse measuring pattern developed on the resist. However, the fixation pattern generates no pattern collapse in the developing process. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a pattern collapse measuring method for examining the presence or absence of pattern collapse due to a development process.

  In order to form a resist pattern, first, a pattern is exposed to a resist formed on a wafer using a mask. Next, a development process is performed. That is, the wafer is immersed in a developer, and after the development is completed, the developer is replaced with a rinse, and the rinse is removed by spin drying.

ただし、γはリンスの表面張力、θは接触角度、Ｈはパターンの高さ、Ｄはパターンのピッチ、Ｗはパターンの幅、Ｈ／Ｗはアスペクト比である。 Surface tension is generated between the patterns during the rinsing liquid removal process. This is shown in FIG. In FIG. 7, a rinsing liquid 73 exists between patterns 72 formed on the wafer 71. The maximum stress σ acting on the pattern is expressed by the following formula.

Where γ is the surface tension of the rinse, θ is the contact angle, H is the height of the pattern, D is the pitch of the pattern, W is the width of the pattern, and H / W is the aspect ratio.

  According to this equation, in the case of resist patterns having different left and right space widths, the left and right surface tensions are not equivalent, so that a pulling force is generated, and a pattern collapse occurs when the resist adhesion force cannot withstand it. Further, as the resist pattern becomes finer, the aspect ratio (thickness / width) becomes larger, so that pattern collapse is likely to occur (see, for example, Non-Patent Document 1).

  If a pattern collapse occurs, subsequent device formation cannot be performed. Therefore, it is important to grasp the limit of occurrence of pattern collapse in the process to be used. Conventionally, SEM observation has been used to measure this pattern collapse.

J. Simons, et al. "Image Collapse Issues in Photoresist", Proceeding of SPIE Vol. 4345, 2001

  However, measurement of pattern collapse by SEM observation is not easy to measure and takes a long time. As a result, since a large amount of data cannot be acquired, the distribution of the pattern collapse on the wafer surface cannot be measured, and statistical data processing cannot be performed due to insufficient data.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to obtain a pattern collapse measuring method capable of quickly and easily examining the presence or absence of pattern collapse.

  The pattern collapse measuring method according to the present invention includes exposing a resist formed on a wafer to a pattern collapse measuring pattern including an evaluation pattern and a fixed pattern, performing a development process on the resist, and developing the resist. Measuring the variation of the center of gravity position of the pattern fall measurement pattern, and checking the presence or absence of the pattern fall of the evaluation pattern. However, the fixed pattern does not collapse during the development process. Other features of the present invention will become apparent below.

  According to the present invention, the presence or absence of pattern collapse can be examined quickly and easily.

Embodiment 1 FIG.
The pattern collapse measuring method according to the first embodiment will be described below. First, the reference pattern 11 and the pattern collapse measurement pattern 12 shown in FIG. 1 are exposed to the resist formed on the wafer. However, as the light source, ArF laser (193 nm), F ₂ laser (157 nm), or EB is used as the light source.

  Next, a development process is performed on the exposed resist. That is, the wafer is immersed in a developer, and after the development is completed, the developer is replaced with a rinse, and the rinse is removed by spin drying.

  Here, the reference pattern 11 is a square having a side of 15 μm. The pattern collapse measurement pattern 12 includes a fixed pattern 13 and an evaluation pattern 14. The fixed pattern 13 is formed in a square frame shape with one side surrounding the reference pattern 11 being 30 μm. The fixed pattern 13 has a width of 1 μm and can be said to be a thick pattern in the 100 nm node level process, and pattern collapse does not occur in the above development process. On the other hand, the evaluation pattern 14 is a single line pattern having a width of about 100 nm and arranged in parallel with the fixed pattern 13 at an interval of 1 μm.

  Next, the barycentric positions of the reference pattern 11 and the pattern collapse measurement pattern 12 developed on the resist are measured using an overlay measuring instrument. Here, the overlay measuring device is usually used to observe two patterns formed with different masks and measure the overlay state. When the overlay measuring instrument is used to measure a pattern composed of elements having a size of several μm or less, the barycentric position of the pattern image is measured as the pattern position. Here, since the purpose is not to measure the overlay state between two masks, the reference pattern 11 and the pattern collapse measurement pattern 12 are formed with one mask.

  The position of the center of gravity of the reference pattern 11 is constant regardless of whether the evaluation pattern 14 has fallen. However, the position of the center of gravity of the pattern collapse measurement pattern 12 varies depending on the presence or absence of the pattern collapse of the evaluation pattern 14. Therefore, the fluctuation of the centroid position of the pattern collapse measurement pattern 12 is measured using the centroid position of the reference pattern 11 as a reference, and the presence or absence of the pattern collapse of the evaluation pattern 14 is examined. Thereby, the presence or absence of pattern collapse can be investigated quickly and easily.

  Here, since the evaluation pattern 14 is thin, it is difficult to measure only this pattern with the overlay measuring instrument. Therefore, the fixed pattern 13 is formed, and the center of gravity position of the pattern collapse measurement pattern 12 including both patterns is measured.

  Further, since the interval between the fixed pattern 13 and the evaluation pattern 14 is 1 μm, when the above light source is used, the interval between the patterns is three times or more of the exposure wavelength. It can be considered an isolated pattern.

Embodiment 2. FIG.
A pattern collapse measuring method according to the second embodiment will be described below. First, the pattern shown in FIG. 2 is exposed to the resist formed on the wafer by the same method as in the first embodiment, and a development process is performed.

  Here, the pattern to be exposed is a pattern in which similar patterns are arranged in quadrants as shown in FIG. The patterns in each quadrant are a plurality of vertically long patterns composed of the reference pattern 21 and the pattern collapse measurement pattern 22 arranged at intervals of 1000 nm.

  And the enlarged view of the part enclosed with the dotted line in Fig.2 (a) is shown in FIG.2 (b). The reference pattern 21 is a line pattern having a length of 8 μm and a width of 1500 nm. The pattern collapse measurement pattern 22 includes a fixed pattern 23 and an evaluation pattern 24. The fixed pattern 23 is a line pattern having a length of 8 μm and a width of 500 nm. Since the fixed pattern 23 has a width of 500 nm, pattern collapse does not occur in the above development process. On the other hand, the evaluation pattern 24 is a single line pattern having a width of about 100 nm and arranged in parallel with the fixed pattern 23 at an interval of 800 nm.

  Next, the position of the center of gravity of the reference pattern 21 and the pattern collapse measurement pattern 22 developed on the resist is measured using an overlay measuring instrument. Then, as in the first embodiment, the variation in the center of gravity of the pattern collapse measurement pattern 22 is measured with reference to the center of gravity of the reference pattern 21 to check whether the evaluation pattern 24 has a pattern collapse. Thereby, the presence or absence of pattern collapse can be investigated quickly and easily.

  Here, since the evaluation pattern 24 is thin, it is difficult to measure only this pattern with the overlay measuring instrument. Therefore, the fixed pattern 23 is formed to measure the position of the center of gravity of the pattern collapse measurement pattern 22 including both patterns.

  Further, since the reference pattern width is 1500 nm, the interval between the fixed pattern 23 and the evaluation pattern 24 is at least 800 nm. Therefore, when the above light source is used, the interval between the patterns is three times or more of the exposure wavelength. Therefore, the evaluation pattern 24 can be regarded as an isolated pattern optically.

  If the width of each of the plurality of evaluation patterns 24 is continuously changed, the boundary of the width at which the pattern collapse occurs can be determined. It is also possible to measure the distribution of pattern collapse within a wafer surface and between wafer surfaces with the pattern size fixed.

  The fixed pattern 23 preferably has a width of 500 nm or more, and the evaluation pattern 24 preferably has a width of 200 nm or less.

Embodiment 3 FIG.
A pattern collapse measuring method according to Embodiment 3 will be described below. First, the reference pattern 31 and the pattern collapse measurement pattern 32 shown in FIG. 3 are exposed to the resist formed on the wafer by the same method as in the first embodiment, and a development process is performed.

  Here, the reference pattern 31 is a square having a side of 15 μm. The pattern collapse measurement pattern 32 is formed in a square frame shape with a side of 30 μm surrounding the reference pattern 31, and includes a fixed pattern 33 and an evaluation pattern 34.

  The fixed pattern 33 is a thick line pattern having a width of 500 nm, and pattern collapse does not occur in the above development process. On the other hand, the evaluation pattern 34 is a plurality of line patterns arranged in a width and a pitch for measuring pattern collapse. That is, it is a pattern in which a plurality of patterns are densely packed. Here, the width of each line pattern is about 100 nm.

  Next, the center of gravity positions of the reference pattern 31 and the pattern collapse measurement pattern 32 developed on the resist are respectively measured using an overlay measuring instrument. Then, as in the first embodiment, the variation in the centroid position of the pattern collapse measurement pattern 32 is measured with reference to the centroid position of the reference pattern 31, and the presence or absence of the pattern collapse of the evaluation pattern 34 is examined. Thereby, the presence or absence of pattern collapse can be investigated quickly and easily.

  Here, on the left side and the right side of the pattern collapse measurement pattern 32, a fixed pattern 33 is formed at the right end, and an evaluation pattern 34 is formed so as to be adjacent to the left side of the fixed pattern 33. For this reason, the largest surface tension acts on the leftmost pattern having the largest space among the line patterns constituting the evaluation pattern 34. As a result, the pattern at the left end falls to the right side, and the position of the center of gravity of the pattern fall measurement pattern 32 changes to the right side. Thus, the recognition system can be improved by configuring the patterns on the left side and the right side of the pattern collapse measurement pattern 32 so that the center of gravity position changes in the same direction when the pattern collapse occurs. The same applies to the upper side and the lower side of the pattern collapse measurement pattern 32.

Embodiment 4 FIG.
A pattern collapse measuring method according to Embodiment 4 will be described below. First, the pattern shown in FIG. 4 is exposed to the resist formed on the wafer by the same method as in the first embodiment, and a development process is performed.

  Here, the pattern to be exposed is a pattern in which similar patterns are arranged in quadrants as shown in FIG. The patterns in each quadrant are a plurality of vertically long patterns composed of the reference pattern 41 and the pattern collapse measurement pattern 42, which are arranged at intervals of 1000 nm.

  And the enlarged view of the part enclosed with the dotted line in Fig.4 (a) is shown in FIG.4 (b). The reference pattern 41 is a line pattern having a length of 8 μm and a width of 1500 nm. The pattern collapse measurement pattern 42 includes a fixed pattern 43 and an evaluation pattern 44. The fixed pattern 43 is a line pattern having a length of 8 μm and a width of 500 nm, and pattern collapse does not occur in the above development process. On the other hand, the evaluation pattern 44 is a plurality of line patterns arranged in a width and a pitch for measuring pattern collapse. That is, it is a pattern in which a plurality of patterns are densely packed. Here, the width of each line pattern is about 100 nm.

  Next, the position of the center of gravity of the reference pattern 41 and the pattern collapse measurement pattern 42 developed on the resist is measured using an overlay measuring instrument. Then, as in the first embodiment, the variation in the center of gravity of the pattern collapse measurement pattern 42 is measured with reference to the center of gravity of the reference pattern 41, and the presence or absence of pattern collapse of the evaluation pattern 44 is examined. Thereby, the presence or absence of pattern collapse can be investigated quickly and easily.

  Here, in the pattern collapse measurement pattern 42, a fixed pattern 43 is formed at the right end, and an evaluation pattern 44 is formed adjacent to the left side of the fixed pattern 43. For this reason, among the line patterns constituting the evaluation pattern 44, the largest surface tension is applied to the leftmost pattern having the widest space. As a result, the pattern at the left end falls to the right side, and the position of the center of gravity of the pattern fall measurement pattern 42 changes to the right side. In this way, the recognition system can be improved by configuring the pattern so that the position of the center of gravity changes in the same direction when the pattern collapse occurs.

Embodiment 5 FIG.
The purpose of the pattern collapse measuring method according to the fifth embodiment is to measure not only the pattern collapse but also the focus shift. Here, in each shot by the exposure machine, the focus is not uniform, and a finite focus variation occurs. Due to this focus shift, the size of the isolated line pattern is reduced, and in the case of a dense pattern, the cross-sectional shape of the resist is inversely tapered, and pattern collapse is likely to occur. Therefore, when a pattern collapse occurs, it is necessary to separate whether it is due to a focus shift or a pattern shape. In view of this, a focus deviation measurement pattern capable of measuring the focus deviation with the overlay measuring instrument is formed in the vicinity of the pattern collapse measurement pattern.

  A pattern collapse measuring method according to the fifth embodiment will be described below. First, the pattern shown in FIG. 5 is exposed to the resist formed on the wafer by the same method as in the first embodiment, and a development process is performed.

  Here, the pattern to be exposed is a pattern in which similar patterns are arranged in quadrants as shown in FIG. The pattern in each quadrant is a vertically long pattern composed of a reference pattern 51 and a focus deviation measurement pattern 53 arranged at an interval of 1000 nm.

  And the enlarged view of the part enclosed with the dotted line in Fig.5 (a) is shown in FIG.5 (b). The reference pattern 51 is a line pattern having a length of 8 μm and a width of 1600 nm. The focus shift measurement pattern 53 includes a first pattern 54 disposed on the left side and a second pattern 55 disposed on the right side. The first pattern 54 is a line pattern having a length of 8 μm and a width of 500 nm. On the other hand, the second pattern 55 is formed by arranging a plurality of line patterns that are orthogonal to the first pattern 54 and thinner than the first pattern 54 at intervals of 500 nm. Here, the width of each line pattern of the second pattern 55 is set to any one of 100, 120, 150, and 180 nm, for example.

  Next, the positions of the center of gravity of the reference pattern 51 and the focus deviation measurement pattern 53 developed on the resist are measured using an overlay measuring instrument. Then, the deviation of the center of gravity of the focus deviation measurement pattern 53 is measured with reference to the position of the center of gravity of the reference pattern 51 to measure the focus deviation.

  Here, when the focus is deviated, each line pattern of the second pattern 55 on the right side is thin and the line end is retracted. However, the first pattern 54 on the left side is thick, so that the dimensions hardly change. As a result, the left end of the focus deviation measurement pattern 53 does not move, only the right end moves, and the center of gravity of the focus deviation measurement pattern 53 moves to the left. Thereby, the focus shift can be measured.

  In addition, as shown in FIG. 5C, instead of the reference pattern 51, a defocus measurement pattern 53 with an opposite direction may be arranged. In this case, since the two focus deviation measurement patterns 53 move in the opposite directions, the measurement sensitivity is doubled.

Embodiment 6 FIG.
Similar to the fifth embodiment, the pattern collapse measuring method according to the sixth embodiment aims to measure not only the pattern collapse but also the focus shift. A pattern collapse measuring method according to the sixth embodiment will be described below. First, the reference pattern 61 and the focus shift measurement pattern 62 shown in FIG. 6 are exposed to the resist formed on the wafer by the same method as in the first embodiment, and a development process is performed.

  Here, the focus shift measurement pattern 62 includes a first pattern 63 and a second pattern 64. The reference pattern 61 and the first pattern 63 are the same as the reference pattern 31 and the fixed pattern 33 of the third embodiment, respectively. Further, as shown in FIG. 6, the second pattern 64 is formed by arranging a plurality of line patterns perpendicular to the first pattern 63 and thinner than the first pattern 63 at intervals of 500 nm. Here, the width of each line pattern of the second pattern 64 is, for example, 100, 120, 150, or 180 nm.

  Next, the barycentric positions of the reference pattern 61 and the focus deviation measurement pattern 62 developed on the resist are respectively measured using an overlay measuring instrument. Then, the deviation of the center of gravity of the measurement pattern 62 is measured based on the position of the center of gravity of the reference pattern 61, and the focus deviation is measured.

  Here, when the focus is deviated, each line pattern of the second pattern 64 on the left side is thin and short, but the first pattern 63 on the right side is thick, so the dimensions hardly change. As a result, the center of gravity of the focus shift measurement pattern 62 moves to the right. Thereby, the focus shift can be measured.

It is a figure which shows the pattern exposed to a resist in Embodiment 1 of this invention. It is a figure which shows the pattern exposed to a resist in Embodiment 2 of this invention. It is a figure which shows the pattern exposed to a resist in Embodiment 3 of this invention. It is a figure which shows the pattern exposed to a resist in Embodiment 4 of this invention. It is a figure which shows the pattern exposed to a resist in Embodiment 5 of this invention. It is a figure which shows the pattern exposed to a resist in Embodiment 6 of this invention. It is sectional drawing which shows a mode that surface tension generate | occur | produces between patterns at the time of a rinse liquid removal process.

Explanation of symbols

11, 21, 31, 41, 51, 61 Reference pattern 12, 22, 32, 42, 52 Pattern fall measurement pattern 13, 23, 33, 43 Fixed pattern 14, 24, 34, 44 Evaluation pattern 53, 62 Focus shift measurement Patterns 54 and 63 First pattern 55 and 64 Second pattern

Claims (4)

Exposing a pattern collapse measurement pattern including an evaluation pattern and a fixed pattern to a resist formed on a wafer;
Performing a development process on the resist;
Measuring the variation of the center of gravity position of the pattern collapse measurement pattern developed on the resist and examining the presence or absence of pattern collapse of the evaluation pattern,
A pattern collapse measuring method, wherein the fixed pattern does not cause pattern collapse in the development process. The evaluation pattern is a line pattern,
2. The pattern collapse measuring method according to claim 1, wherein an interval between the fixed pattern and the evaluation pattern is at least three times an exposure wavelength. The evaluation pattern is a pattern in which a plurality of patterns are densely packed,
The pattern collapse measuring method according to claim 1, wherein the fixed pattern and the evaluation pattern are adjacent to each other. Exposing a focus shift measurement pattern including a first pattern and a second pattern in the vicinity of the pattern collapse measurement pattern of the resist;
Measuring the deviation of focus by measuring the variation of the center of gravity position of the defocus measurement pattern developed on the resist;
The pattern collapse measurement method according to claim 1, wherein the second pattern is orthogonal to the first pattern and is thinner than the first pattern.

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