JP2009198396A - Device and method for inspecting surface - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device for inspecting a surface capable of detecting deformation of a pattern shape precisely. <P>SOLUTION: The device 1 for inspecting a surface irradiates the surface of a wafer 10 having a repeated pattern by a lighting system 30 with linear polarization in a plurality of set angles set by use of a stage 20. A light receiving system 40 detects a polarization component of which vibration direction is perpendicular to the linear polarization from the light regularly reflected from the wafer 10. An image process section 50 detects the deformation of the pattern shape from the correlation between the light amount of the polarization component that are detected for each the plurality of set angles and the set angles. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a surface inspection apparatus and surface inspection for detecting a pattern shape collapse in a repetitive pattern based on a polarization component of specularly reflected light generated by irradiating linearly polarized light on a repetitive pattern (line and space pattern) of a test substrate. Regarding the method.

  2. Description of the Related Art Conventionally, an inspection apparatus that uses diffracted light is known as an inspection apparatus that detects a collapse of a pattern shape in a repeated pattern (line and space pattern) formed on the surface of a wafer. In an apparatus using diffracted light, it is necessary to use light having a short wavelength in order to satisfy the Bragg condition when the pattern pitch is shortened. However, the use of short-wavelength light not only makes the apparatus expensive, but also causes a problem that the resist is exposed when a resist pattern is inspected.

On the other hand, an inspection apparatus using structural birefringence of a repetitive pattern has been proposed. This apparatus irradiates a repetitive pattern with linearly polarized light and detects light having a component orthogonal to the polarization component for inspection (see, for example, Patent Document 1). According to such an apparatus, when there is a collapse (that is, a defect) in the resist repetitive pattern, the amount of light (light intensity) of the regularly reflected light (polarized light component) to be detected is compared with the case in which the pattern does not collapse. Therefore, it is possible to detect the collapse of the pattern shape from the amount of specularly reflected light (polarized light component). Thereby, the inspection of the fine repeating pattern which does not emit diffracted light can be carried out without using short wavelength light.
JP 2007-93394 A

  As described above, in the inspection using the structural birefringence of the repetitive pattern, when the repetitive pattern is broken, the amount of light (light intensity) of the regularly reflected light (polarized component) to be detected is not broken. However, the degree of decrease varies depending on the type of the repeated pattern and the angle formed by the repeating direction of the repeating pattern and the vibration direction of the linearly polarized light. However, in the conventional inspection, since the angle formed by the repetition direction of the repeated pattern and the vibration direction of the linearly polarized light is set to only one kind of angle, the ideal light quantity at the set angle is obtained. Without knowing, there is a possibility that the detection accuracy of pattern collapse may be lowered.

  The present invention has been made in view of such a problem, and an object of the present invention is to provide a surface inspection apparatus and a surface inspection method capable of accurately detecting a collapse of a pattern shape.

  In order to achieve such an object, a surface inspection apparatus according to the present invention includes an illumination unit that irradiates a surface of a test substrate having a predetermined repetitive pattern with linearly polarized light, and the test substrate that is irradiated with the linearly polarized light. Based on the polarized light component detected by the detecting unit that detects a polarized light component whose vibration direction is substantially perpendicular to the linearly polarized light from the regular reflected light from the surface, the pattern shape in the repetitive pattern is deformed. An inspection unit for detecting; and an angle setting unit capable of setting an angle formed by a repeating direction of the repeating pattern and a vibration direction of the linearly polarized light on the surface of the substrate to be tested to a predetermined setting angle, The illumination unit irradiates the surface of the substrate to be tested with the linearly polarized light at the plurality of set angles set by: and the detection unit includes the straight line of the regular reflected light. A polarization component whose vibration direction is substantially perpendicular to light is detected, and the inspection unit detects the pattern from the correlation between the light amount of the polarization component detected by the detection unit for each of the plurality of setting angles and the setting angle. The shape collapse is detected.

  Further, the surface inspection method according to the present invention includes an illumination step of irradiating the surface of the test substrate having a predetermined repetitive pattern with linearly polarized light, and regular reflection light from the surface of the test substrate irradiated with the linearly polarized light. A detection step for detecting a polarization component whose vibration direction is substantially perpendicular to the linearly polarized light, and an inspection step for detecting a collapse of a pattern shape in the repetitive pattern based on the polarization component detected in the detection step, A setting step of setting an angle formed by a repeating direction of a repeating pattern and a vibration direction of the linearly polarized light on the surface of the test substrate to a predetermined setting angle, and at a plurality of the setting angles set in the setting step In the illumination step, the surface of the substrate to be tested is irradiated with the linearly polarized light, and in the detection step, the linearly polarized light and the vibration direction are substantially perpendicular to the specularly reflected light. A polarization component is detected, and in the inspection step, the collapse of the pattern shape is detected from the correlation between the light amount of the polarization component detected for each of the plurality of set angles in the detection step and the set angle. ing.

  According to the present invention, it is possible to accurately detect the collapse of the pattern shape.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. As shown in FIG. 1, the surface inspection apparatus 1 of the present embodiment includes a stage 20 that supports a semiconductor wafer 10 (hereinafter referred to as a wafer 10) that is a substrate to be tested, an illumination system 30, and a light receiving system 40. It is prepared for. In addition, the surface inspection apparatus 1 includes an image processing unit 50 that performs image processing of an image captured by the light receiving system 40, and a monitor 55 that displays an image captured by the light receiving system 40 and an image processing result by the image processing unit 50. It has. The surface inspection apparatus 1 is an apparatus that automatically inspects the surface of a wafer 10 in a manufacturing process of a semiconductor circuit element. After exposure / development of the uppermost resist film, the wafer 10 is carried from a wafer cassette (not shown) or a developing device by a conveyance system (not shown), and is sucked and held on the stage 20.

  A plurality of chip regions are arranged on the surface of the wafer 10, and each chip region is located between a plurality of line portions 2 </ b> A serving as convex portions and adjacent line portions 2 </ b> A as shown in FIG. 2. A repetitive pattern 12 (line and space pattern) composed of the space portion 2B (which becomes a recess) is formed. The repetitive pattern 12 is a resist pattern (for example, a wiring pattern) in which a plurality of line portions 2A are arranged at a constant repetitive pitch P along the short direction. The arrangement direction of the line portions 2A is referred to as “repetitive direction of the repeated pattern 12”.

  Here, the design value of the line width of the line portion 2A in the repetitive pattern 12 is set to ½ of the pitch P. That is, the repetitive pattern 12 has a concavo-convex shape in which the line portions 2A and the space portions 2B are alternately arranged along the repetitive direction, and when the repetitive pattern 12 is formed according to the design value with an appropriate exposure focus, The line width of 2A and the line width of the space portion 2B are equal, and the volume ratio between the line portion 2A and the space portion 2B is approximately 1: 1. Such a shape is also called an ideal shape.

  In the present embodiment, it is assumed that the pitch P of the repeating pattern 12 is sufficiently small compared to the wavelength of illumination light (linearly polarized light described later) with respect to the repeating pattern 12. For this reason, diffracted light is not generated from the repetitive pattern 12, and the defect inspection of the repetitive pattern 12 cannot be performed by diffracted light.

  The stage 20 of the surface inspection apparatus 1 supports the wafer 10 on the upper surface and fixes and holds the wafer 10 by, for example, vacuum suction. Further, the stage 20 is rotatable about the normal A1 at the center of the upper surface as a central axis. By this rotation mechanism, the repeating direction of the repeating pattern 12 on the wafer 10 can be rotated within the surface of the wafer 10. The stage 20 has a horizontal upper surface, and can always keep the wafer 10 in a horizontal state.

  As shown in FIG. 1, the illumination system 30 includes an illumination device 31, a first polarizing plate 32, and a first concave reflecting mirror 33. The illumination device 31 includes a light source such as a mercury lamp (not shown) and a wavelength selection filter, and can emit light having a specific wavelength. The 1st polarizing plate 32 makes the light inject | emitted from the illuminating device 31 into the linearly polarized light L (refer FIG. 3) according to the direction of a transmission axis. The first concave reflecting mirror 33 converts the light from the first polarizing plate 32 reflected by the first concave reflecting mirror 33 into a parallel light beam and irradiates the wafer 10 as the test substrate. That is, the illumination system 30 is an optical system telecentric with respect to the wafer 10 side.

  In the illumination system 30, the light from the illumination device 31 becomes p-polarized linearly polarized light L via the first polarizing plate 32 and the first concave reflecting mirror 33 and enters the entire surface of the wafer 10. At this time, the incident angle of the linearly polarized light L at each point of the wafer 10 is the same because of the parallel light flux, and corresponds to the angle θ formed by the optical axis and the normal line A1.

  In this embodiment, since the linearly polarized light L incident on the wafer 10 is p-polarized light, the repeating direction of the repeated pattern 12 is the incident surface of the linearly polarized light L (linearly polarized light on the surface of the wafer 10) as shown in FIG. When the angle is set to 45 degrees with respect to the L traveling direction), the angle formed by the vibration direction of the linearly polarized light L on the surface of the wafer 10 and the repeating direction of the repeating pattern 12 is also set to 45 degrees. In other words, the linearly polarized light L changes into the repeated pattern 12 so as to cross the repeated pattern 12 diagonally with the vibration direction of the linearly polarized light L on the surface of the wafer 10 inclined by 45 degrees with respect to the repeated direction of the repeated pattern 12. It will be incident. In FIG. 3, the vibration direction of the linearly polarized light L, which is p-polarized light, represents the vibration direction in a state of being projected onto the surface of the wafer 10 (repeated pattern 12).

  As shown in FIG. 1, the light receiving system 40 includes a second concave reflecting mirror 41, a second polarizing plate 42, and an imaging device 43, and the optical axis passes through the center of the stage 20. It arrange | positions so that only angle (theta) may incline with respect to normal line A1. Therefore, the specularly reflected light from the repeated pattern 12 travels along the optical axis of the light receiving system 40. The second concave reflecting mirror 41 is the same reflecting mirror as the first concave reflecting mirror 33, reflects regular reflection light from the repeated pattern 12 and condenses it on the imaging surface of the imaging device 43.

  However, a second polarizing plate 42 is disposed between the second concave reflecting mirror 41 and the imaging device 43. The direction of the transmission axis of the second polarizing plate 42 is set so as to be orthogonal to the transmission axis of the first polarizing plate 32 of the illumination system 30 described above (crossed Nicol state). Therefore, the second polarizing plate 42 extracts a polarization component (for example, an s-polarized component) whose vibration direction is substantially perpendicular to the linearly polarized light L from the regular reflection light from the repetitive pattern 12 and guides it to the imaging device 43. be able to. As a result, a reflected image of the wafer 10 is formed on the imaging surface of the imaging device 43 by the polarization component of the regular reflection light from the repetitive pattern 12 that is substantially perpendicular to the linearly polarized light L and the vibration direction.

  The imaging device 43 is configured by, for example, a CCD imaging device and the like, photoelectrically converts a reflected image of the wafer 10 formed on the imaging surface, and outputs an image signal to the image processing unit 50. The brightness of the reflected image of the wafer 10 is substantially proportional to the amount of light (light intensity) of the polarization component detected by the imaging device 43 and changes according to the shape of the repeated pattern 12. The reflected image of the wafer 10 becomes brightest when the repeated pattern 12 has an ideal shape (when the pattern does not collapse). The brightness of the reflected image of the wafer 10 appears for each shot area.

  The image processing unit 50 captures a reflected image of the wafer 10 based on the image signal output from the imaging device 43. When the image processing unit 50 captures the reflection image of the wafer 10 that is the test substrate, the image processing unit 50 detects the collapse of the pattern shape in the repeated pattern 12 from the reflection image of the wafer 10. Further, the detection result of pattern collapse by the image processing unit 50 and the reflected image of the wafer 10 at that time are output and displayed on the monitor 55.

  A surface inspection method using the surface inspection apparatus 1 having such a configuration will be described below with reference to the flowchart shown in FIG. First, the stage 20 is rotated, and the setting is performed so that the repeating direction of the repeating pattern 12 is inclined to an initial setting angle (for example, 0 degree) with respect to the vibration direction of the linearly polarized light L on the surface of the wafer 10 (step S101). . In this setting step, the angle formed between the repeating direction of the repeating pattern 12 and the vibration direction of the linearly polarized light L on the surface of the wafer 10 is set in the range of 0 to 180 degrees in increments of 5 degrees (0 degrees, 5 degrees, 10 degrees... 175 degrees and 180 degrees).

  Next, the linearly polarized light L is irradiated onto the surface of the wafer 10 fixedly held on the stage 20 at a predetermined set angle (step S102). In this illumination process, the light emitted from the illumination device 31 is converted into p-polarized linearly polarized light L by the first polarizing plate 32 and becomes a parallel light flux by the first concave reflecting mirror 33 to be reflected on the wafer 10. Irradiate the surface.

  The specularly reflected light reflected by the surface of the wafer 10 is collected by the second concave reflecting mirror 41 and is polarized by the second polarizing plate 42 with a polarization component (for example, substantially perpendicular to the linearly polarized light L of the specularly reflected light). , S-polarized components) are extracted and guided onto the imaging surface of the imaging device 43. Therefore, in the next detection step, the polarization component guided onto the imaging surface of the imaging device 43 is detected by the imaging device 43 (step S103). At this time, the imaging device 43 photoelectrically converts the reflected image of the wafer 10 by the polarization component of the specularly reflected light that is substantially perpendicular to the linearly polarized light L formed on the imaging surface, and performs image processing on the image signal. To the unit 50.

  As described above, when the reflection image (polarization component) of the wafer 10 is detected at the setting angle set in the setting step, whether or not the reflection image (polarization component) of the wafer 10 is detected at all the setting angles in the next step S104. Determine whether. When the determination is Yes, the process proceeds to the next step S105, and when the determination is No, the process returns to step S101, for example, the angle formed by the repetition direction of the repeated pattern 12 and the vibration direction of the linearly polarized light L on the surface of the wafer 10 Until the stage 20 is set to a new setting angle obtained by rotating the stage 20 by 5 degrees with respect to the previous setting angle, until the reflected image (polarized light component) of the wafer 10 is detected at all the setting angles (setting angles of 0 to 180 degrees). The processing from step S102 to step S104 is repeated.

  In the next step S105, the image processing unit 50 detects the collapse of the pattern shape in the repeated pattern 12 based on the polarization component detected in the previous step. By the way, when the surface of the repetitive pattern 12 (line and space pattern) is irradiated with the linearly polarized light L and the polarized light component whose vibration direction is substantially perpendicular to the linearly polarized light L from the regular reflected light from the repetitive pattern 12 is detected. When the angle formed by the repeating direction of 12 and the vibration direction of the linearly polarized light L on the surface of the wafer 10 (hereinafter referred to as the azimuth angle) is 45 degrees, the amount of polarized light component (light intensity) may be maximized. Are known. On the other hand, it is known that when the azimuth angle is 0 degree or 90 degrees, the light amount (light intensity) of the polarization component is minimized.

  For example, the correlation between the light amount (light intensity) of the polarization component (reflected image of the wafer 10) detected at a plurality of set angles in the detection step and the set angle (that is, the azimuth angle) is shown in FIG. It is. In the present embodiment, as shown by a broken line in FIG. 5, the data of the portion of the wafer 10 having the brightest light quantity among the polarization components (reflected images of the wafer 10) detected at a plurality of set angles in the detection process is obtained. Used as “experiment reference data”.

  When the surface of the repeated pattern 12 (line and space pattern) is irradiated with the linearly polarized light L and the polarized light component whose vibration direction is substantially perpendicular to the linearly polarized light L from the regular reflected light from the repeated pattern 12 is detected. The correlation equation showing the correlation between the amount of light (light intensity) and the azimuth angle is theoretically expressed by the following equation (1) from the relationship of structural birefringence.

I (φ) = A × sin ² {2 × (φ + φ ′)} + C (1)

  Here, I (φ) is the intensity of the polarization component, and φ is the azimuth angle. A, C, and φ ′ are constants, A is the maximum intensity of I (φ), C is a correction coefficient for correcting where I (φ) should be 0, and φ ′ is I (φ φ) is the shift amount of the azimuth angle at which the maximum intensity is obtained.

  In the inspection process of step S105, first, as a first step, the wafer having the brightest light quantity among the polarized components (reflected images of the wafer 10) detected for each of a plurality of set angles by the detection process. The data of the portion 10 is extracted as “experiment reference data”, and constants A, C, and φ ′ are obtained so that the extracted “experiment reference data” matches the above-described equation (1). The expression (1) expressed using the constants A, C, and φ ′ obtained from the “experiment reference data” will be referred to as “theoretical reference data”. The “theoretical reference data” and the “experiment reference data” only need to match very well, but may not match as shown in FIG. 6, for example. That is, in the portion of the wafer 10 from which the “experiment reference data” is obtained, for example, as shown in FIG. 8, the pattern shape of the repeated pattern 12 ′ (line and space pattern) is broken.

  When “theoretical reference data” and “experimental reference data” are compared, the difference is small and it is difficult to detect the collapse of the pattern shape. Therefore, in the inspection process, as a second step, the correlation between the light amount of the polarization component (light intensity) and the set angle (azimuth angle) in the portion other than the “experiment reference data” on the wafer 10 is obtained as “ Compared with "theoretical reference data", the pattern shape collapse is detected. Specifically, the image processing unit 50 calculates the change rate (contrast) of the polarization component in the entire portion other than the “experiment reference data” on the wafer 10 with respect to the “theoretical reference data” for each of a plurality of set angles. To calculate.

  As a third step, the image processing unit 50 calculates the correlation between the contrast of the polarization component calculated for each of the plurality of setting angles and the setting angle, and the contrast when the image processing unit 50 is a good product stored in advance in the image processing unit 50. The correlation with the set angle is compared, and when the difference in contrast distribution exceeds a preset threshold value, it is determined that there is a pattern collapse in the repeated pattern 12 (line and space pattern).

  In the case of a non-defective product, the contrast is such that the surface of a repetitive pattern (not shown) of the non-defective wafer is irradiated with linearly polarized light L, and the polarized light component whose vibration direction is substantially perpendicular to the linearly polarized light L of regular reflected light from the repetitive pattern The light quantity change rate (contrast) of the polarization component is calculated for each of a plurality of set angles with respect to the “theoretical reference data” obtained from the polarization component in the non-defective wafer. A non-defective wafer is one in which the repeated pattern 12 is formed on the entire surface in a substantially ideal shape.

  Therefore, when a large pattern collapse has occurred in the repetitive pattern 12, as shown in FIG. 7, there is a large difference in the contrast distribution as compared with a non-defective product. This is because when a large pattern collapse occurs in the repetitive pattern 12, the contrast (the light amount change rate) of the polarization component increases and large unevenness occurs in the contrast distribution.

  As described above, according to the present embodiment, the pattern shape collapse is detected at the plurality of set angles in order to detect the pattern shape collapse from the correlation between the light amount of the polarization component detected at each of the plurality of set angles and the set angle. Since it detects, it becomes possible to detect collapse of a pattern shape accurately.

  At this time, the correlation between the light quantity change rate of the polarization component and the set angle with respect to the “theoretical reference data” based on the formula (1) and the correlation between the light quantity change rate and the set angle in the case of a non-defective standard product are compared. By doing so, since the difference in the light amount change rate is larger than the difference in light amount between the “theoretical reference data” and the “experiment reference data”, it is possible to increase the detection sensitivity of pattern collapse.

  In the above-described embodiment, when it is known in advance that the amount of light of the polarization component greatly changes when the pattern shape collapses, the “theoretical reference data” and the “experiment reference data” are directly compared, and the pattern The collapse of the shape may be detected.

  In the above-described embodiment, the example in which the linearly polarized light L is p-polarized light has been described. However, the present invention is not limited to this. For example, s-polarized light may be used instead of p-polarized light. At this time, the polarization component detected by the imaging device 43 is, for example, a p-polarized component.

  In the above-described embodiment, the linearly polarized light L is generated using the illumination light from the illumination device 31 and the first polarizing plate 32. However, the present invention is not limited to this. If the laser which supplies is used as a light source, the first polarizing plate 32 is not necessary.

It is a figure showing the whole surface inspection device composition concerning the present invention. It is the schematic of a repeating pattern. It is a figure explaining the inclination state of the entrance plane of a linearly polarized light and the repeating direction of a repeating pattern. It is a flowchart of the surface inspection method which concerns on this invention. It is a graph which shows the correlation with the light quantity (light intensity) of a polarization component, and an azimuth angle. It is the graph which compared "theoretical reference data" and "experiment reference data". It is a graph which shows the correlation with contrast and an azimuth angle. It is the schematic of the repetitive pattern which collapsed in the pattern shape.

Explanation of symbols

1 Surface inspection device 10 Wafer (Subject to be tested)
12 Repeat pattern (line and space pattern)
20 stage (angle setting part) 30 illumination system (illumination part)
40 Light receiving system (detection unit) 50 Image processing unit (inspection unit)
L Linearly polarized light

Claims (6)

An illumination unit that irradiates the surface of the test substrate having a predetermined repeating pattern with linearly polarized light;
A detection unit for detecting a polarization component whose vibration direction is substantially perpendicular to the linearly polarized light out of specularly reflected light from the surface of the test substrate irradiated with the linearly polarized light;
Based on the polarization component detected by the detection unit, an inspection unit that detects the collapse of the pattern shape in the repetitive pattern;
An angle setting unit capable of setting an angle formed by the repeating direction of the repeating pattern and the vibration direction of the linearly polarized light on the surface of the test substrate to a predetermined setting angle;
At the plurality of set angles set by the angle setting unit, the illumination unit irradiates the surface of the substrate with the linearly polarized light, and the detection unit includes the linearly polarized light and the vibration direction of the regular reflected light. Detects a polarization component with a substantially right angle,
The surface inspection apparatus, wherein the inspection unit detects a collapse of the pattern shape from a correlation between a light amount of the polarization component detected by the detection unit for each of the plurality of setting angles and the setting angle. . The inspection unit obtains a correlation equation indicating a correlation between the light amount of the polarization component and the set angle from the polarization component detected for each of the plurality of set angles by the detection unit, and is obtained from the correlation equation. A light amount change rate of the polarization component with respect to the light amount to be obtained is calculated for each of the plurality of the setting angles;
The pattern shape collapse is detected by comparing the correlation between the light amount change rate calculated for each of the plurality of set angles and the set angle and the correlation between a reference light amount change rate and the set angle. The surface inspection apparatus according to claim 1.   The surface inspection according to claim 1, wherein the repetitive pattern is a line-and-space pattern including a plurality of line portions and a space portion positioned between the plurality of line portions. apparatus. An illumination step of irradiating the surface of the test substrate having a predetermined repeating pattern with linearly polarized light;
A detection step of detecting a polarization component whose vibration direction is substantially perpendicular to the linearly polarized light out of specularly reflected light from the surface of the test substrate irradiated with the linearly polarized light;
Based on the polarization component detected in the detection step, an inspection step for detecting a collapse of the pattern shape in the repetitive pattern;
A setting step of setting an angle formed by a repeating direction of the repeating pattern and a vibration direction of the linearly polarized light on the surface of the test substrate to a predetermined setting angle;
At the plurality of setting angles set in the setting step, the surface of the substrate to be tested is irradiated with the linearly polarized light in the illumination step, and the linearly polarized light and the vibration direction of the specularly reflected light in the detecting step are substantially the same. Detects right-angle polarization components,
In the inspection step, the pattern inspection is detected from the correlation between the light amount of the polarization component detected for each of the plurality of set angles and the set angle in the detection step. The inspection step includes a first step of obtaining a correlation equation indicating a correlation between a light amount of the polarization component and the set angle from the polarization component detected for each of the plurality of set angles in the detection step;
A second step of calculating, for each of the plurality of set angles, a light amount change rate of the polarization component with respect to a light amount obtained from the correlation equation obtained in the first step;
By comparing the correlation between the light amount change rate calculated for each of the plurality of set angles and the set angle in the second step, and the correlation between the reference light amount change rate and the set angle, the pattern The surface inspection method according to claim 4, further comprising a third step of detecting shape collapse.   6. The surface inspection according to claim 4, wherein the repetitive pattern is a line and space pattern including a plurality of line portions and a space portion positioned between the plurality of line portions. Method.

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