JP2013113650A - Trench depth measuring apparatus and trench depth measuring method and confocal microscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain a trench depth measuring apparatus for measuring the depth of a trench with high aspect ratio, whose trench width is at the same degree as wavelength of illumination light.SOLUTION: An illumination optical system has: light source devices 1-4 which generate line-like illumination beams; and an objective lens 6 which projects the line-like illumination beams toward a sample to form a line-like pupil pattern in parallel with the longitudinal direction of a trench at a pupil position between the light source devices and the objective lens. The line-like pupil pattern forms a line-like illumination area so as to intersect the trench on the sample surface 7 where the trench is formed via the objective lens. In addition, linearly polarized illumination light is used as the illumination light, and a direction of its electric field vector is set approximately in parallel with the longitudinal direction of the trench. By setting the direction of the electric field vector of the linearly polarized illumination light in the longitudinal direction of the trench, optical loss in the trench decreases, the illumination light can be entered inside the trench, and highly accurate depth measurement becomes possible.

Description

  The present invention relates to a trench depth measuring apparatus that measures the depth of a trench formed in various semiconductor substrates, and more particularly to a trench depth measuring apparatus that can measure the depth of a high aspect ratio trench with high accuracy.

  In the semiconductor device manufacturing process, various devices using trench isolation and trench processing have been developed. For example, a MOSFET having a trench gate structure has been developed as a high breakdown voltage MOSFET. In addition, in an image sensor such as a CMOS sensor or a CCD sensor, a trench is formed so as to separate each light receiving element, and crosstalk between adjacent pixels is prevented. On the other hand, the trench depth has a strong influence on device performance and manufacturing yield. For example, in a CMOS sensor, if the trench depth is insufficient, charge leakage between adjacent pixels increases and imaging is performed. Image quality may be adversely affected. Also in a power device, when the trench depth is insufficient, a predetermined withstand voltage performance may not be obtained. Further, with the miniaturization of semiconductor devices, high aspect ratio trenches are widely used. Therefore, in the semiconductor device manufacturing process, there is a strong demand for the development of a trench depth measuring apparatus that can measure the depth of a high aspect ratio trench with high accuracy.

As a measuring device for measuring the depth of a trench, a measuring device using a confocal optical system is known (see, for example, Patent Document 1). In this known trench depth measuring apparatus, the surface of a substrate is two-dimensionally scanned with a laser beam while changing the distance between the stage holding the substrate on which the trench is formed and the objective lens, and reflected light from the substrate surface and Reflected light from the bottom of the trench is detected by a photodetector. Then, the position in the optical axis direction of the objective lens where the intensity of the reflected light from the substrate surface around the trench is maximized and the position in the optical axis direction of the objective lens where the intensity of the reflected light from the bottom of the trench is maximized are specified. The distance between these two positions is determined and the trench depth is measured.
JP 2003-218095 A

  In the known measurement device described above, the pupil pattern of the illumination beam is circular, so when measuring the depth of a high aspect ratio trench, the majority of the illumination beam incident on the trench is shielded at the edge of the trench. As a result, there is a problem that only a small amount of illumination light enters the bottom surface of the trench. That is, the width of the trench formed in the CMOS sensor or power device is at a submicron level. Therefore, when the illumination beam with a circular pupil pattern is used, the illumination light is shielded by the sample surface around the trench and cannot enter the trench, and the reflected light from the bottom of the trench is too weak. was there. For this reason, the signal level of the output signal from the photodetector is too low, causing a problem with accuracy. As a method for solving this problem, it is conceivable to increase the amount of illumination light incident on the bottom surface using an objective lens having a small numerical aperture. However, when an objective lens having a small numerical aperture is used, there arises a problem that the resolution is lowered. For example, when measuring the depth of a trench formed in a CMOS sensor, a resolution of about 0.1 μm is required in the depth direction. Therefore, if an objective lens having a small numerical aperture is used, The resolution is too low, resulting in a failure to meet the depth measurement requirements.

  Further, in the conventional confocal depth measuring apparatus, the surface of the sample including the trench is two-dimensionally scanned with the laser beam while changing the position of the objective lens in the optical axis direction. And the throughput is reduced. That is, in the conventional trench depth measuring apparatus, since the sample surface is two-dimensionally scanned while changing the position of the objective lens in the optical axis direction, a considerable time is required for two-dimensional scanning, and the depth of one trench is measured. It took a long time to measure and there was a problem in terms of throughput.

  Furthermore, in order to measure the depth of the trench with high resolution, it is assumed that measurement light having a short wavelength is used. On the other hand, since many laser light sources that generate ultraviolet or deep ultraviolet (DUV) laser light are pulse oscillation types, multiple laser pulses are emitted to remove or reduce the effect of speckle patterns. It is necessary to obtain and reduce the influence of the speckle pattern by integration. For this reason, the moving speed of the objective lens or the sample stage during the Z-axis scan necessary for depth measurement must be set to be considerably slow. Therefore, when the sample surface is scanned two-dimensionally, there arises a problem that the measurement throughput is considerably slowed down. In this case, it is assumed that only Z-axis scanning is performed without performing two-dimensional scanning of the sample surface. However, when the pupil pattern of the illumination beam is circular, only the bottom surface of the trench is illuminated, so the Z-axis scan for detecting the position of the bottom surface of the trench in the optical axis direction and the position of the sample surface around the trench in the optical axis direction Two Z-axis scans of the Z-axis scan for detecting the image are necessary, and there is still a problem that the throughput is lowered. Accordingly, there is a strong demand for the development of a trench depth measuring apparatus that can obtain a considerably high throughput even when using ultraviolet or deep ultraviolet (DUV) laser light.

An object of the present invention is to realize a trench depth measuring apparatus capable of measuring the depth of a trench having a high aspect ratio with high accuracy.
Furthermore, another object of the present invention is to provide a trench depth measuring apparatus capable of measuring the depth of a high aspect ratio trench with high throughput.
Furthermore, another object of the present invention is to realize a trench depth measuring apparatus capable of measuring the depth of a trench having a trench width comparable to the wavelength of illumination light.

A trench depth measurement apparatus according to the present invention is a trench depth measurement apparatus for measuring the depth of a trench formed in a sample,
A stage for supporting a sample in which a trench to be depth-measured is formed;
A light source device that generates an illumination beam; and an objective lens that projects the illumination beam toward the sample. A linear pupil pattern parallel to the longitudinal direction of the trench is formed at a pupil position between the light source device and the objective lens. An illumination optical system that forms a line-shaped illumination area that intersects the trench on the sample surface where the trench is formed;
Scanning means for performing Z-axis scanning by changing the relative distance in the optical axis direction between the objective lens and the sample;
Sensor means for detecting the position in the optical axis direction of the objective lens or stage during the Z-axis scan or the distance in the optical axis direction between the objective lens and the stage, and outputting the position information or distance information from the sample surface near the trench A light detecting means for receiving the reflected light from the bottom of the trench and the reflected light from the bottom of the trench through the objective lens;
And a signal processing device that outputs trench depth information based on a luminance signal output from the light detection means and position information or distance information output from the sensor means.

  In the present invention, a line-shaped pupil pattern extending in parallel with the longitudinal direction of the trench formed in the sample is formed, and the line-shaped pupil pattern is imaged on the sample surface via the objective lens. A linear illumination area perpendicular to the trench is formed on the surface. As a result, the illumination light that is shielded from the sample surface and does not contribute to depth measurement can be greatly reduced. Furthermore, illumination can be performed using an objective lens having a large numerical aperture, for example, an objective lens having a numerical aperture of about 0.80, thereby enabling highly accurate trench depth measurement. In addition, since the amount of illumination light shielded around the trench is greatly reduced, an output signal having a stable signal level can be obtained from the light detection means without using a high output light source.

  Furthermore, the line-shaped illumination area formed on the sample surface so as to intersect the trench can illuminate both the inside of the trench and the sample surface around the trench at the same time, and only performs one Z-axis scan. Thus, it is possible to detect the position of the bottom surface of the trench and the sample surface around the trench in the optical axis direction. As a result, the advantage is achieved that the measurement throughput is greatly improved. In particular, in order to perform high resolution measurement, it is desirable to use a laser light source that generates an illumination beam with a short wavelength. However, since many excimer lasers that emit ultraviolet or deep ultraviolet (DUV) laser beams are pulse oscillation types, in order to reduce the effect of speckle patterns, the phase distribution of illumination light is modulated. It is necessary to take and accumulate a plurality of images. In this case, in the measuring apparatus that two-dimensionally scans the sample surface, a considerable time is required for the two-dimensional scanning itself, so that the throughput is significantly reduced. In addition, when an illumination beam having a circular pupil pattern is used, if the Z-axis scan is performed while focusing on the bottom surface of the trench, the position of the sample surface in the optical axis direction is not detected. Z-axis scanning is separately required, and at least two Z-axis scannings are required. Therefore, when an illumination beam is generated using a pulse oscillation type excimer laser, a problem that the throughput further decreases occurs. On the other hand, in the present invention, since both the inside of the trench and the peripheral sample surface are illuminated at the same time, a trench depth measuring apparatus that can sufficiently cope with the use of a pulsed excimer laser is realized. .

Another trench depth measuring apparatus according to the present invention is a trench depth measuring apparatus for measuring the depth of a trench formed in a sample,
A stage for supporting a sample in which a trench to be depth-measured is formed;
A light source device that generates a linearly polarized illumination beam, and an objective lens that projects the illumination beam toward the sample, and has a line shape parallel to the longitudinal direction of the trench at the pupil position between the light source device and the objective lens. An illumination optical system that forms a pupil pattern and forms a linear illumination area that intersects the trench on the sample surface on which the trench is formed;
Scanning means for performing Z-axis scanning by changing the relative distance in the optical axis direction between the objective lens and the sample;
Sensor means for detecting the position in the optical axis direction of the objective lens or stage during the Z-axis scan or the distance in the optical axis direction between the objective lens and the stage, and outputting the position information or distance information from the sample surface near the trench A light detecting means for receiving the reflected light from the bottom of the trench and the reflected light from the bottom of the trench through the objective lens;
A signal processing device that outputs the depth information of the trench based on the luminance signal output from the light detection means and the position information or distance information output from the sensor means,
The oscillation direction of the electric field vector of linearly polarized light constituting the illumination beam incident on the sample surface is set substantially parallel to the longitudinal direction of the trench.

  When the illumination light enters the inside of the trench, it is reflected by the side wall of the trench or repeatedly reflected and enters the bottom surface of the trench. The reflected light reflected from the bottom surface of the trench is also reflected from the sidewall of the trench and emitted from the trench. Therefore, the reflectance of the illumination light with respect to the sidewall of the trench is closely related to the light loss in the trench. Therefore, as a result of examining the relationship between the polarization state of illumination light and the reflectance, in the case of illumination light having a wavelength of 193 nm, the reflectance of S-polarized light is considerably higher than that of P-polarized light at a relatively large incident angle. There was found. Moreover, in the case of S-polarized light, it was also confirmed that a reflectance of 80% or more can be obtained in a range where the incident angle exceeds 60 °. If this data is applied to the trench, the optical loss in the trench is considerably reduced by setting the oscillation direction of the electric field vector of the linearly polarized illumination light to be parallel to the longitudinal direction of the trench. According to this examination result, even when the width of the trench is equal to the wavelength of the illumination light, a sufficient amount of reflected light is generated from the bottom surface of the trench. Based on this examination result, in the present invention, linearly polarized light is used as illumination light, and the direction of the electric field vector is set to be parallel to the longitudinal direction of the trench. As a result, an ArF excimer laser that generates laser light having a wavelength of 193 nm is used as the illumination light source, and the electric field vector of the laser light is set parallel to the longitudinal direction of the trench so that the trench width of about 0.2 μm is obtained. It is possible to measure the thickness with high accuracy. In other words, by using an ArF excimer laser as an illumination light source and an objective lens having a large numerical aperture, the depth of a trench having an opening width substantially equal to the wavelength of the illumination light can be measured with high accuracy. .

In the present invention, a line-shaped pupil pattern parallel to the longitudinal direction of the trench is formed at the pupil position between the light source and the objective lens, and the line-shaped pupil pattern is imaged on the sample surface via the objective lens. Therefore, a line-shaped illumination area extending in a direction orthogonal to the trench is formed on the sample surface. As a result, the illumination light that is shielded from the sample surface and does not contribute to the depth measurement can be greatly reduced, and the trench depth can be measured with high accuracy. Furthermore, since the line-shaped illumination area formed on the sample surface illuminates both the trench and the surrounding sample surface, the light on the bottom of the trench and the sample surface around the trench can be obtained by performing only one Z-axis scan. The axial position can be detected and the measurement throughput is greatly improved.
Furthermore, if a linear pupil pattern is formed and the direction of the electric field vector of the illumination light is set parallel to the longitudinal direction of the trench, the depth of the trench is increased even if the trench width is equal to the wavelength of the illumination light. It can be measured with high accuracy.

It is a figure which shows the basic composition of the trench depth measuring apparatus by this invention. It is a figure which shows the relationship of the image formed in the pupil pattern of an illumination beam, an objective lens, and a sample. It is the figure which contrasted the illumination method by this invention, and the conventional illumination method. It is a graph which shows the relationship between the position of the stage in Z-axis scanning, and the luminance value of the output signal output from a photon detection means. It is a figure which shows an example of a signal processing apparatus. It is a figure which shows the modification of the trench depth measuring apparatus by this invention. It is a figure explaining the simulation result with respect to the direction of the electric field vector of the illumination light linearly polarized. It is a figure which shows another modification of the trench depth measuring apparatus by this invention. It is a figure which shows the algorithm of the trench depth measuring method by this invention. It is a figure which shows an example of the confocal microscope by this invention.

  FIG. 1 is a diagram showing a basic configuration of a trench depth measuring apparatus according to the present invention. In the present invention, the depth of the trench is measured using an illumination optical system that illuminates the sample surface with a linear illumination beam. An illumination beam is emitted from the light source 1. A lamp such as a mercury lamp can be used as the light source, or a continuous wave laser such as a semiconductor laser or a He-Ne laser that emits linearly polarized illumination light, or a pulsed laser such as an excimer laser is used. be able to. Moreover, as a wavelength of illumination light, light in various wavelength ranges can be used, and illumination light having a wavelength in the ultraviolet region or deep ultraviolet region (DUV) can be used. The illumination beam emitted from the light source 1 enters the cylindrical lens 2. The cylindrical lens 2 has a focusing property only in the in-plane direction, and converts the incident illumination beam into a linear illumination beam. The slit means 3 is disposed at the focal point of the line-shaped illumination beam. The slit means 3 has a slit-like opening extending in a direction perpendicular to the paper surface, and the width of the slit opening is, for example, 10 μm. The line-shaped illumination beam passes through the slit opening of the slit means 3 and enters the beam splitter 5 through the converging lens 4. The converging lens 4 acts on the incident line-shaped illumination beam so as to focus the beam in the extending direction of the slit opening (direction orthogonal to the paper surface), and is orthogonal to the extending direction of the slit opening. The direction (in-plane direction) acts so that the divergent beam becomes a parallel beam parallel to the optical axis. The beam splitter 5 serves to separate the illumination beam from the illumination light source toward the sample and the reflected light from the sample.

  The line-shaped illumination beam reflected by the beam splitter 5 enters the objective lens 6. In the present invention, the pupil of the illumination beam is formed between the light source 1 and the objective lens 6, and a linear pupil pattern parallel to the longitudinal direction of the trench is formed at the pupil position. The objective lens 6 forms an image of the line-shaped pupil pattern on the surface of the sample 7 where the trench is formed, thereby forming a line-shaped illumination area that intersects the trench. In this example, in order to obtain high resolution, an objective lens having a large numerical aperture can be used, for example, an objective lens having a numerical aperture of about 0.9. As a sample in which a trench is formed, for example, a silicon substrate on which a CMOS sensor is manufactured and various semiconductor substrates on which power devices are formed are used. The optical element included in the optical path from the light source 1 to the objective lens 6 constitutes an illumination optical system that illuminates the sample surface with a linear illumination beam.

  As will be described later, the trench whose depth is to be measured extends in the plane of the paper, and the line-shaped illumination area extends in a direction perpendicular to the trench (a direction perpendicular to the plane of the paper). That is, the line-shaped illumination area is formed so as to intersect with the trench to be depth-measured so as to be orthogonal to the longitudinal direction of the trench in this example. Therefore, a part of the linear illumination beam travels inside the trench and is reflected at the bottom of the trench, and the reflected light is collected by the objective lens 6. The remaining portion of the line-shaped illumination beam is incident on the sample surface where the trench is formed, reflected by the sample surface, and the reflected light is also collected by the objective lens 6. Thus, in the present invention, a linear illumination beam is used to simultaneously illuminate both the inside of the trench and the sample surface where the trench is formed.

  Sample 7 is placed on stage 8. The stage 8 can freely move in the XY plane orthogonal to the optical axis of the objective lens 6 and also moves in the Z direction, which is the optical axis direction of the objective lens. The stage is moved in the XY plane for alignment, and the trench to be measured is positioned in the field of view of the objective lens. Further, the relative distance between the sample 7 and the objective lens 6 is changed by the movement of the stage 8 in the optical axis direction, and Z-axis scanning is performed. As the Z-axis scanning means, not only the stage movement, but also a servo motor can be attached to the objective lens, the stage can be stopped, and the objective lens can be moved in the optical axis direction to perform Z-axis scanning.

  A position sensor 9 for detecting the position in the Z-axis direction is connected to the stage 8. A position sensor 9 as sensor means detects the position of the stage in the optical axis direction during the Z-axis scan, and outputs the detected position information to the signal processing device 10. That is, the position information detected by the position sensor 9 is used as relative position information or relative distance information of the sample surface and the trench bottom with respect to the objective lens during the Z-axis scan, and the focal point of the objective lens is on the sample surface and the bottom of the trench. The positional relationship between the objective lens and the sample when positioned is specified.

  Reflected light from the sample 7, that is, reflected light from the bottom of the trench and reflected light from the sample surface around the trench are collected by the objective lens and enter the light detection means 12 through the beam splitter 5 and the imaging lens 11. To do. As the light detection means, a two-dimensional imaging element in which a plurality of light receiving elements are arranged in a two-dimensional array or a line sensor in which a plurality of light receiving elements are arranged in a line can be used. A two-dimensional imaging device arranged in a two-dimensional array is used. The output signal from the light detection means 12 is sequentially read by the drive signal supplied from the signal processing device 10, amplified by the amplifier 13, and then supplied to the signal processing device 10. The signal processing device 10 calculates the depth of the trench formed in the sample using the output signal from the light detection means 12 and the position information from the position sensor 9.

  In the present invention, the slit means 3, the surface of the sample 7, and the light detection means 12 are arranged at conjugate positions. Accordingly, an image of the opening of the slit means 3 is formed on the sample, and a linear illumination area is formed on the sample. An image of the linear illumination area formed on the sample is formed on the light detection means 12. By forming such an optical arrangement, optical characteristics similar to those of the confocal optical system can be obtained, and in the light receiving element of the light detecting means, depending on the relative displacement of the sample surface and the bottom of the trench with respect to the focal point of the objective lens. The amount of incident reflected light changes. In other words, the light receiving element that receives the reflected light from the bottom of the trench outputs an output signal having the highest luminance value when the focal point of the objective lens is located at the bottom of the trench, and the bottom of the trench is at the focal point of the objective lens. An output signal having a gradually lower luminance value is output as the displacement occurs. Similarly, the light receiving element on which the reflected light from the sample surface near the trench is incident outputs an output signal with the highest luminance value when the focal point of the objective lens is located on the sample surface. As the sample surface is displaced, an output signal having a gradually lower luminance value is output. Therefore, when the light receiving element that receives the reflected light from the bottom of the trench detects the maximum luminance value, and when the light receiving element that receives the reflected light from the sample surface near the trench detects the maximum luminance value. The depth of the trench, which is the difference in the optical axis direction between the bottom of the trench and the sample surface near the trench, can be measured based on the position of the stage.

  FIG. 2 is a diagram showing the illumination pattern on the pupil pattern of the illumination beam, the objective lens, and the sample surface. FIG. 2A shows a state where the focal point of the objective lens is located on the sample surface where the trench is formed, that is, a state where the focal point is focused on the sample surface where the trench is formed, and FIG. A state where the focal point of the lens is located on the bottom surface of the trench, that is, a state where the lens is focused on the bottom surface of the trench is shown. Note that the direction of the electric field vector when linearly polarized illumination light is used as the illumination beam is also displayed.

  The line-shaped illumination beam forms a pupil pattern at the pupil position formed in the optical path between the slit means 3 and the objective lens 6. The pupil pattern has a line shape, and the extending direction is set to be parallel to the extending direction (longitudinal direction) of the trench. The illumination beam emitted from the pupil pattern is focused by the objective lens to form a linear illumination beam 21 extending on the sample surface in a direction orthogonal to the longitudinal direction of the trench 20 and extending on the sample surface in a direction orthogonal to the trench. An existing line-shaped illumination area is formed. Regarding the resolution, in a direction parallel to the trench, illumination light in a wide angle range corresponding to the numerical aperture of the objective lens is focused, so that sufficient resolution can be obtained.

  The beam portion 21a on one side of the line-shaped illumination beam 21 is incident on the sample surface on one side across the trench 20, and the beam portion 21b on the opposite side is incident on the sample surface on the opposite side across the trench. The intermediate beam portion 21c is incident on the opening of the trench.

  FIG. 2A shows a state where the focal point of the objective lens is located on the sample surface. In this case, the beam portions 21a and 21b of the illumination beam 21 form a focal line on the sample surface and generate reflected light with high brightness. Further, the intermediate beam portion 21c enters the inside of the trench 20 and forms a relatively wide illumination area on the bottom surface 20a of the trench as a divergent beam, and generates reflected light with low luminance. FIG. 2B shows a state where the focal point of the objective lens is located on the bottom surface 20a of the trench. In this case, the beam portion 21c in the middle of the illumination beam is focused on the bottom surface 20a of the trench and generates reflected light with high brightness. Further, the beam portions 21a and 21b at both ends illuminate a comparatively wide area of the sample surface and generate reflected light with low luminance. Therefore, by performing Z-axis scanning by moving the stage, the position of the objective lens in the optical axis direction and the focus of the objective lens on the bottom surface 20a of the trench are determined based on the output signal from the light detection means. A position in the optical axis direction located on the surrounding sample surface is detected. Then, using the detected position information, the position of the sample surface and the bottom surface of the trench in the optical axis direction is detected, and the depth of the trench can be detected.

  FIG. 3 is a diagram comparing the illumination method according to the present invention and a conventional illumination method. FIG. 3A illustrates an illumination method according to the present invention, and FIG. 3B illustrates a conventional illumination method. In the present invention, a line-shaped pupil pattern extending in parallel with the trench is formed at the pupil position, and a line-shaped illumination area extending in the direction orthogonal to the trench is formed on the sample surface via the objective lens. Further, a linearly polarized illumination beam is used as illumination light. On the other hand, in the conventional illumination method, a circular pupil pattern is formed at the pupil position, and a circular illumination area is formed on the sample surface.

  As shown in FIG. 3B, in the illumination method for forming a circular pupil pattern, since a circular illumination area is formed on the sample surface, most of the illumination beam is shielded by the sample surface around the trench 20. The amount of illumination light entering the trench 20 is very small. Therefore, there is a limit in measuring the depth of a high aspect ratio trench with a narrow trench width. On the other hand, if a line-shaped illumination area is formed so as to intersect the trench, the amount of illumination light blocked by the sample surface around the trench is greatly reduced, and the amount of illumination light entering the trench is greatly increased. To do.

  Next, Z-axis scanning will be described. In the present invention, Z-axis scanning is performed while changing the relative distance between the sample and the focal point of the objective lens, and the first position when the focal point of the objective lens is located on the sample surface where the trench is formed is detected. At the same time, the second position when the focal point of the objective lens is located on the bottom surface of the trench is detected, the difference between the first position and the second position is obtained and output as the depth information of the trench. That is, when the focal point of the objective lens is located on the sample surface, a focal line is formed on the sample surface, and reflected light with the maximum luminance is generated from the sample surface, and the reflected light is received by the light detection means 12. . Further, when the stage is moved in the optical axis direction and the focal point of the objective lens is located on the bottom surface of the trench, reflected light having the maximum luminance is generated from the bottom surface of the trench, and the reflected light is another light receiving element of the light detecting means 12. Is received. Therefore, by detecting the position of the stage when the light receiving element that receives the reflected light from the sample surface where the trench is formed outputs the maximum luminance value, the focus of the objective lens when the focal point is located on the sample surface is detected. A first position is detected. Further, the second position when the focal point of the objective lens is located on the bottom surface of the trench is detected by detecting the position of the stage when the light receiving element that receives the reflected light from the bottom surface of the trench outputs the maximum luminance value. Is detected.

  In this example, the Z-axis scan is performed by moving the stage supporting the sample in the optical axis direction. In the Z-axis scan, a lower limit position in the optical axis direction of the stage is set. While gradually raising the stage from the lower limit position, the luminance value of the output signal of the light receiving element of the light detecting means is detected. At the same time, the position of the stage in the optical axis direction is also detected by the position sensor. When the stage reaches the upper limit position of the Z-axis scan, the Z-axis scan ends. That is, in the present invention, since both the reflected light from the bottom surface of the trench and the reflected light from the sample surface forming the trench are detected in parallel during the Z-axis scan, the optical axis direction of the sample surface and the bottom surface of the trench is The position can be detected by a single Z-axis scan. FIG. 4 shows the change in the luminance value of the output signal from the light receiving element that receives the reflected light from the sample surface of the light detection means 12 with respect to the position in the optical axis direction of the stage during the Z-axis scan, and the reflected light from the bottom surface of the trench. The change of the luminance value of the output signal from the light receiving element that receives light is shown. The solid line indicates the luminance value of the output signal from the light receiving element that receives the reflected light from the bottom surface of the trench, and the broken line indicates the luminance value of the output signal from the light receiving element that receives the reflected light from the sample surface. As shown in FIG. 4, the light receiving element that receives the reflected light from the bottom surface of the trench and the light receiving element that receives the reflected light from the sample surface output a peak luminance value corresponding to the displacement in the optical axis direction. Therefore, the difference between the positions in the optical axis direction at the time when the two peak luminance values are detected corresponds to the depth of the trench.

  FIG. 5 is a diagram showing an example of an algorithm for calculating the trench depth in the signal processing device. A luminance signal output from each light receiving element of the light detection means 12 is input to the signal processing circuit 10. Further, a position signal output from the position sensor 9 and indicating the position of the stage in the optical axis direction is also input. The luminance signal output from the light detecting means 12 is sequentially amplified by the amplifier 13, converted into a digital signal by the A / D converter 30, and input to the signal processing device 10. The input luminance signal is supplied to the comparator 31 and the selector 32, respectively. The luminance signal selected by the selector 32 is stored in the first frame memory 33. The luminance signal stored in the first frame memory 33 is supplied to the comparator 31 and the selector 32. The comparator 31 compares the luminance value of each newly input pixel with the luminance value of each pixel stored in the frame memory 33. If the luminance value of the newly input luminance signal is large, the comparator 31 A selection signal to be selected is output to the selector 32. When the selector 32 receives the selection signal from the comparator, the selector 32 selects the newly input luminance signal and outputs it to the first frame memory 33. On the other hand, when the selection signal is not supplied from the comparator, the luminance signal stored in the frame memory is output.

  The position signal output from the position sensor 9 is supplied to the second frame memory 34. The second frame memory 34 has memory elements corresponding to the pixels of the light detection means, and stores the position of the stage when the maximum luminance value is generated for each memory element. The second frame memory 34 is also supplied with a selection signal from the comparator. The supplied selection signal acts as a write control signal for the second frame memory 26. Therefore, when the selection signal is supplied from the comparator, the position signal output from the distance sensor is written into the frame memory.

  In the present invention, both the reflected light from the bottom surface of the trench and the reflected light from the sample surface near the trench are detected in parallel. In this case, since the image of the bottom surface of the trench and the image of the sample surface are formed on separate light receiving elements on the light detecting means, the position of the stage is adjusted and the reflected light from the bottom surface of the trench on the light detecting means. It is desirable to identify in advance a light receiving element that receives light and a light receiving element that receives reflected light from the sample surface.

  As the Z-axis scan starts, the stage starts to rise. The light detection means 12 receives reflected light from the sample surface and reflected light from the bottom surface of the trench, and sequentially outputs luminance signals. At the same time, the position sensor 9 also detects the position of the stage in the optical axis direction and sequentially outputs position signals. When a high luminance signal is input during the Z-axis scan, the contents of the first and second frame memories are sequentially updated. When the focal point of the objective lens is positioned on the sample surface, the maximum luminance value is output from the light receiving element that receives the reflected light from the sample surface, and the comparator generates a selection signal. The position of the stage when the maximum luminance value is generated by this selection signal is written into the second frame memory. Further, when the stage is raised and the focal point of the objective lens reaches the bottom surface of the trench, a maximum luminance value is generated from the light receiving element that receives the reflected light from the bottom surface of the trench. At the same time, a selection signal is generated from the comparator, supplied to the second frame memory 34, and the position signal of the stage at that time is written into the second frame memory in response to the input of the selection signal.

  When the Z-axis scan is completed, the difference between the position signal of the memory element corresponding to the light receiving element that receives the reflected light from the sample surface and the position signal of the memory element corresponding to the light receiving element that receives the reflected light from the bottom surface of the trench, respectively. It outputs to the means 35. The difference means 35 forms a difference between the two position signals and outputs the difference as trench depth information. As described above, according to the present invention, it is possible to measure the depth of the trench only by performing one Z-axis scan.

  FIG. 6 is a view showing a modification of the trench depth measuring apparatus according to the present invention. In addition, the same code | symbol is attached | subjected and demonstrated to the component same as the member used in FIG. In this example, linearly polarized laser light is used as illumination light so that S-polarized illumination light is incident on the sidewall of the trench, that is, the oscillation direction of the electric field vector of the laser light is parallel to the longitudinal direction of the trench. The ratio of the illumination light toward the trench and the reflected light emitted from the trench is absorbed by the sidewall of the trench as much as possible. A pulsed excimer laser 40 is used as a light source for generating an illumination beam. The excimer laser 40 emits a linearly polarized laser beam having a wavelength of, for example, 193 nm. When the excimer laser 40 illuminates the sample surface including the trench, the polarization state is adjusted such that S-polarized laser light is incident on the sidewall of the trench. The laser beam emitted from the excimer laser 40 enters the beam reducer 41. In the beam reducer 41, a convex lens 41a and a concave lens 41b are combined to reduce the beam diameter of the incident laser beam. The laser beam emitted from the beam reducer 41 enters the cylindrical lens 2 and is converted into a laser beam having focusing properties in one direction (in-plane direction of the paper). The direction of the electric field vector of the linearly polarized laser beam emitted from the excimer laser 40 is made to coincide with the focusing direction by the cylindrical lens 2. That is, the linearly polarized linear illumination beam emitted from an objective lens described later is set so that the extending direction of the linear beam and the electric field vector are orthogonal to each other. In this case, when the line-shaped illumination beam is illuminated so as to be orthogonal to the longitudinal direction of the trench formed in the sample, the electric field vector of the line-shaped illumination beam is set to be parallel to the longitudinal direction of the trench. . The relationship between the direction of the electric field vector and the pupil pattern is as shown in FIG. 2, and the extending direction of the line-shaped pupil pattern is matched with the direction of the electric field vector.

  The laser beam emitted from the cylindrical lens 2 enters the speckle pattern removing means 42. The speckle pattern removing means 42 has a motor 42a and a rotary diffusion plate 42b connected to the motor 42a, and the incident laser beam is converted into a laser beam whose speckle pattern changes with time. The laser beam emitted from the speckle pattern removing means is incident on a square rod 43 made of synthetic quartz and functioning as a homogenizer. The image captured using the laser beam has a speckle pattern, but the phase distribution is modulated while passing through the rotating diffusion plate, and the laser beam is converted into a laser beam with a substantially uniform luminance distribution while passing through the square rod. The The laser beam emitted from the square rod 43 enters the slit means 3. The slit means 3 has a slit opening extending in the direction orthogonal to the paper surface, that is, the direction orthogonal to the focusing direction of the cylindrical lens, and the incident laser beam passes through the slit opening and is focused as a divergent line beam. Incident on the sexual lens 4. The converging lens 4 acts on the incident laser beam to focus the beam in the direction in which the slit opening extends (perpendicular to the paper surface), and in the direction orthogonal to the extending direction of the slit opening. The component in the (in-plane direction) acts so that the divergent beam becomes a parallel beam parallel to the optical axis.

  The laser beam emitted from the converging lens 4 is reflected by the beam splitter 5 and enters the objective lens 6. In this example, a half mirror is used as a beam splitter, and a linearly polarized laser beam is incident on the objective lens. The objective lens 6 converts the incident laser beam into a focusing line-shaped illumination beam, and illuminates the sample surface on which the trench is formed with a linear linearly polarized illumination beam.

  As in the embodiment shown in FIG. 1, the line-shaped pupil pattern formed at the pupil position is imaged on the sample surface by the objective lens 6, and a line-shaped illumination area perpendicular to the trench is formed on the sample surface. Is done. Therefore, both the inside of the trench and the sample surface where the trench is formed are illuminated simultaneously. The vibration direction of the electric field vector of the illumination beam is set in a direction orthogonal to the extending direction of the line-shaped illumination beam. Therefore, a straight line in which the electric field vector is set in parallel to the longitudinal direction of the trench is formed inside the trench. Polarized illumination light enters.

  The reflected light from the sample 7, that is, the reflected light from the bottom surface of the trench and the reflected light from the sample surface around the trench are collected by the objective lens and passed through the beam splitter 5 and the imaging lens 11 to the light detection means 12. Incident. The output signal from the light detection means 12 is sequentially read by the drive signal supplied from the signal processing device 10, amplified by the amplifier 13, and then supplied to the signal processing device 10.

  In this example, the stage 8 that supports the sample 7 is kept stationary in the optical axis direction, and the Z-axis scan is performed by moving the objective lens 6 in the optical axis direction. The objective lens 6 is supported so as to be movable in the optical axis direction and is connected to a servo motor 44. An encoder 45 is connected to the servo motor 44 to detect the position of the objective lens in the optical axis direction. The detected position information is supplied to the signal processing device 10. As in the above-described embodiment, the signal processing apparatus 10 calculates the depth of the trench formed in the sample using the output signal from the light detection unit 12 and the position information from the encoder 44.

  Next, the effect of the vibration direction of the electric field vector of linearly polarized illumination light will be described. When measuring the depth using the reflected light from the bottom of the trench, if the amount of reflected light from the bottom is small, the signal level output from the light detection means will be low and the detection accuracy of the peak luminance value will be reduced Will occur. In particular, when measuring the depth of a trench with a high aspect ratio, light absorption by the trench sidewall with respect to illumination light traveling from the objective lens into the trench and reflected light from the bottom surface of the trench becomes a problem. Therefore, the relationship between the polarization state of illumination light (vibration direction of the electric field vector) and the reflectance at the sidewall of the trench was examined. That is, when the illumination light enters the inside of the trench, it is reflected on the side wall of the trench or repeatedly reflected and enters the bottom surface of the trench. The reflected light reflected from the bottom surface of the trench is also reflected from the sidewall of the trench and emitted from the trench. Therefore, it is assumed that the amount of reflected light emitted from the trench varies depending on the reflectance of the illumination light with respect to the sidewall of the trench. Then, it examined how the reflectance with respect to the side wall of a trench changes with the polarization states of the linearly polarized illumination light.

  FIG. 7 is a graph showing the intensity reflectance (refractive index: 0.883, extinction coefficient 2.778) of crystalline silicon at a wavelength of 193 nm. This data is the data described in the publication “Handbook of Optical Constance of Solids” (Edard D. Palik, Academic Press, Boston, 1985). The horizontal axis indicates the incident angle (degrees), and the vertical axis indicates the intensity reflectance. In FIG. 7, the solid line indicates the intensity reflectance when S-polarized illumination light is incident on the surface of crystalline silicon, and the broken line indicates the intensity reflectance when P-polarized illumination light is incident. S-polarized light is a direction in which the vibration direction of the electric field vector (electric vector) is perpendicular to the incident surface, and therefore the vibration direction of the electric field vector is parallel to the surface of the silicon crystal. On the other hand, in the P-polarized light, the vibration direction of the electric field vector is parallel to the incident surface, and therefore the vibration direction of the electric field vector is a direction orthogonal to the surface of the silicon crystal.

  Referring to FIG. 7, when the incident angle is around 0 degrees, the reflectance of both S-polarized light and P-polarized light is about 70%. When the illumination light is S-polarized light, the reflectance gradually increases with respect to the incident angle, and when the incident angle exceeds 60 °, the reflectance becomes 80% or more. Further, when the incident angle is 90 °, the reflectance becomes 100%. On the other hand, when the illumination light is P-polarized light, the reflectance gradually decreases as the incident angle increases, reaches a minimum value when the incident angle is around 70 °, and then gradually increases. Similar to the polarization, the reflectance is 100%. The data shows that when the incident angle with respect to the surface of the silicon crystal is relatively large, the reflectance of S-polarized light is higher than that of P-polarized light.

  The above data is applied to the illumination light incident on the trench. When illuminating a trench formed in a silicon substrate with linearly polarized illumination light, the illumination light is diffracted, so that the incident angle with respect to the sidewall of the trench is slightly displaced from 90 °. The illumination light emitted from the light source is incident on the bottom surface of the trench while being reflected by the sidewall of the trench. Reflected light from the bottom surface of the trench is also reflected by the side wall and emitted from the trench. Therefore, the higher the reflectance at the sidewall of the trench, the smaller the loss of illumination light in the trench. Therefore, based on the intensity reflectance data of the crystalline silicon at a wavelength of 193 nm, the light loss in the trench is reduced by using the S-polarized light as the illumination light and projecting the S-polarized light to the trench. Depth measurement is possible. Here, in the case of S-polarized light, the vibration direction of the electric field vector is perpendicular to the incident surface, and therefore when the light enters the trench, the vibration direction of the electric field vector is parallel to the sidewall of the trench, and the length of the trench Set parallel to the direction.

  From the examination result of the intensity reflectance data shown in FIG. 7, the illumination light absorbed and reflected by the trench is obtained by using linearly polarized light whose electric field vector direction is set parallel to the longitudinal direction of the trench as illumination light. It was confirmed that the ratio of light can be greatly reduced. In particular, even when the width of the trench is set to about the wavelength of the illumination light, a sufficient amount of reflected light is ensured. From this examination result, it is possible to measure the depth with high accuracy even for a trench having a high aspect ratio with a slit width substantially equal to the wavelength of the illumination light and an aspect ratio of about 10.

  Furthermore, as a synergistic effect by using a linear illumination beam extending in a direction perpendicular to the longitudinal direction of the trench and setting the direction of the electric field vector of the illumination beam in parallel with the longitudinal direction of the trench, output from the light detection means The signal level of the luminance signal to be generated becomes considerably high, and the depth of the trench having a wavelength level width (about 0.2 μm) can be measured with high accuracy using illumination light in the ultraviolet region or deep ultraviolet region (DUV). It becomes possible. When the trench acts as a waveguide, the measurement result may be corrected in consideration of the group delay according to the waveguide mode.

  FIG. 8 is a view showing another modification of the trench depth measuring apparatus according to the present invention. This example has an imaging mode for capturing a two-dimensional image of the sample surface and a depth measurement mode for measuring the depth of a trench formed in the sample, and can selectively switch between sample observation and depth measurement. A possible trench depth measuring apparatus will be described. That is, a two-dimensional image of the sample surface is picked up in the imaging mode, and the position of the trench whose depth is to be measured is adjusted while viewing the two-dimensional image of the sample surface displayed on the monitor. Then, the mode is switched, and the depth of the trench whose position has been adjusted is measured in the depth measurement mode. In addition, the same code | symbol is attached | subjected to the component same as the member used in FIG. 6, and the description is abbreviate | omitted.

  Referring to FIG. 8, bypass optical path means 60 for bypassing the slit means 3 and first and second relay lenses 61 in the optical path between the square rod 43 functioning as a homogenizer and the converging lens 4. And 62 are arranged. The first and second relay lenses are arranged in the optical path between the square rod 43 and the slit means 3. The bypass optical path means 60 includes a first total reflection mirror 63 disposed between the first and second relay lenses, and a second total reflection mirror 64 that reflects the illumination light reflected by the first total reflection mirror. The converging lens 65 for focusing the illumination light emitted from the second total reflection mirror, the total reflection mirror 66 for reflecting the illumination light emitted from the convergence lens 65, and the illumination light emitted from the total reflection mirror 66. And a fourth total reflection mirror 67 to be incident on the sexual lens 4. The optical elements included in the optical path from the first total reflection mirror 63 to the fourth total reflection mirror 67 are combined together so as to be integrated into and out of the optical path. The bypass optical path means 60 is disposed in the optical path in the imaging mode for observing the sample surface, and is removed from the optical path in the depth measurement mode.

  In the imaging mode for capturing a two-dimensional image of the sample surface, the illumination beam emitted from the square rod 43 is transmitted through the first relay lens 61, the first total reflection mirror 63, the second total reflection mirror 64, and the converging lens 65. The optical path on the illumination side of the objective lens 6 is coupled through a bypass optical path including the third total reflection mirror 66 and the fourth total reflection mirror 67. Then, a two-dimensional area on the sample surface is illuminated through the converging lens 4, the beam splitter 5 and the objective lens 6. Then, the reflected light from the surface of the sample 7 is collected by the objective lens, and enters the light detection means 12 configured by a two-dimensional image sensor through the beam splitter and the imaging lens 11. The output signal from the light detection means is amplified and supplied to the signal processing device 10, and a two-dimensional image signal of the sample surface is output. Therefore, the operator adjusts the position of the stage so that the trench whose depth is to be measured is positioned at a desired position while viewing the two-dimensional image of the sample displayed on the monitor.

After the position adjustment is completed, switch the mode and switch to the depth measurement mode. By this mode switching, the bypass optical path means 60 is removed from the optical path of the illumination optical system, and depth measurement is executed. In the depth measurement mode, the linear illumination beam emitted from the square rod 43 passes through the first and second relay lenses 61 and 62 and enters the slit means 3. Further, the light passes through the slit opening of the slit means 3 and enters the objective lens 6 through the converging lens 4 and the beam splitter 5. Then, the surface of the sample including the trench is illuminated as a linear illumination beam extending in a direction orthogonal to the trench formed in the sample 7. Hereinafter, depth measurement is performed based on the embodiment shown in FIG.

  FIG. 9 is a flowchart showing an example of the algorithm of the trench depth measurement method according to the present invention. In step 1, the mode of the trench depth measurement device is set to an imaging mode, a two-dimensional image of the sample surface is taken, and the position of the trench is adjusted so as to intersect with the linear illumination beam.

  Next, the mode is switched to switch from the imaging mode to the depth measurement mode. Subsequently, the illumination optical system is operated to form a linear illumination area so as to intersect with the trench on the sample surface (step 2).

  Subsequently, a Z-axis scan is executed. At this time, the objective lens is gradually lowered from the upper limit position to the lower limit position (step 3). While the objective lens is descending, the position of the objective lens in the optical axis direction is detected and output as position information. Further, the brightness value of the image of the trench formed on the light detection means and the image of the sample surface around the trench is also detected. Then, the signal processing shown in FIG. 5 is performed to detect the position in the optical axis direction of the objective lens that generates the maximum luminance value.

  During the Z-axis scan, first, when the focal point of the objective lens approaches the sample surface and the focal point is located on the sample surface, a focal line is formed on the sample surface. At this time, the maximum luminance value is output from the light receiving element that receives the reflected light from the sample surface. The position in the optical axis direction of the objective lens where the maximum luminance value is generated is detected as the first position (step 4).

  When the objective lens is further lowered, the focal point of the objective lens approaches the bottom surface of the trench, and when the focal point is located on the bottom surface of the trench, a light intensity signal having the highest luminance is output from the light receiving element that detects the image of the trench. The position of the objective lens in the optical axis direction is detected as the second position (step 5).

  When the objective lens reaches the lower limit position, the depth measurement ends. Then, a difference between the first position indicating the position of the sample surface in the optical axis direction and the second position indicating the position of the bottom surface of the trench in the optical axis direction is formed, and is output as trench depth information.

  FIG. 10 is a diagram showing the configuration of a confocal microscope using the basic principle of the present invention. The confocal microscope of this example functions as a confocal microscope that can be switched between the depth measurement mode and the two-dimensional image capturing mode. In addition, the same code | symbol is attached | subjected to the component same as the component used in FIG. 1, and the description is abbreviate | omitted. The illumination beam emitted from the light source 1 is converted into a line-shaped illumination beam that is focused in one direction by the cylindrical lens 2, and passes through the slit means 3, the converging lens 4, and the beam splitter 5 to form a galvano mirror 70 as a line-shaped illumination beam. Is incident on. The galvanometer mirror functions as a scanning device that periodically deflects the incident line-shaped illumination beam in a direction orthogonal to the extending direction in an imaging mode for capturing a two-dimensional image of the sample surface, and is used in a depth measurement mode. Functions as a stationary mirror maintained in a stationary state.

  The line-shaped illumination beam emitted from the galvanometer mirror 70 forms a line-shaped pupil pattern at the pupil position via the two relay lenses 71 and 72. The line-shaped illumination beam forming the pupil pattern is focused by the objective lens 6 to form a line-shaped illumination area on the sample 7 so as to intersect the trench.

  The stage 8 that supports the sample 7 can move freely in the XY plane orthogonal to the optical axis of the objective lens 6 and also moves in the Z direction, which is the optical axis direction of the objective lens. The stage 8 performs Z-axis scanning in both the imaging mode and the depth measurement mode. Accordingly, in the imaging mode, the sample surface is scanned by the linear illumination beam and also scanned in the Z-axis direction. On the other hand, in the depth measurement mode, since the galvanometer mirror functions as a fixed mirror, the sample surface is scanned one-dimensionally along the Z-axis direction by the line illumination beam. A position sensor 9 for detecting the position in the Z-axis direction is connected to the stage 8. The position sensor 9 detects the position of the stage in the optical axis direction during the Z-axis scan, and outputs the detected position information to the signal processing device 10.

  The reflected light from the sample 7, that is, the reflected light from the bottom of the trench and the reflected light from the sample surface around the trench are collected by the objective lens, and the relay lenses 72 and 71, the galvanometer mirror 70, the beam splitter 5 and the imaging. The light enters the light detection means 12 through the lens 11. In this example, a line sensor in which a plurality of light receiving elements are arranged in a line is used as the light detection means. The output signal from the light detection means is sequentially read by the drive signal supplied from the signal processing device 10, amplified by the amplifier 13, and then supplied to the signal processing device 10. The signal processing device 10 performs processing based on FIG. 5 using the luminance signal output from the light detection means and the position information from the position sensor 9, and for each pixel, the maximum luminance value detected during the Z-axis scan. Is stored in the memory, and the position of the stage in the optical axis direction at the time when the maximum luminance value is generated is detected and stored in the memory.

  In an imaging mode for capturing a two-dimensional image of the sample surface, the position information of the stage that outputs the maximum luminance value and outputs the two-dimensional image of the sample surface in which each pixel is configured with the maximum luminance value, that is, the shape of the sample surface Information is also output. Therefore, a three-dimensional image of the sample surface can be output. On the other hand, in the depth measurement mode, the galvanometer mirror 70 is stationary, and only the Z-axis scan is performed by moving the stage. Therefore, the signal processing apparatus has the first position indicating the position of the sample surface in the optical axis direction and the trench position. The trench depth information is output based on the second position indicating the position of the bottom surface in the optical axis direction.

  The present invention is not limited to the above-described embodiments, and various modifications and changes can be made. For example, in the above-described embodiment, the position of the stage or the objective lens in the optical axis direction is detected by the sensor means and output as the position information. However, the position information can be used by using the movement amount of the stage and the objective lens. is there. Further, a distance sensor may be fixed to the objective lens, the distance between the objective lens and the sample may be measured by the distance sensor, and the displacement amount of the stage or the objective lens in the optical axis direction may be obtained using the measured distance information. Is possible.

  Further, when the trench width affects the measurement value, the depth measurement value can be corrected using the trench width value obtained from the image.

DESCRIPTION OF SYMBOLS 1 Light source 2 Cylindrical lens 3 Slit means 4 Focusing lens 5 Beam splitter 6 Objective lens 7 Sample 8 Stage 9 Position sensor 10 Signal processing apparatus 11 Imaging lens 12 Photodetection means 13 Amplifier 20 Illumination beam 30 A / D converter 31 Comparison Unit 32 Selector 33 First frame memory 34 Second frame memory 35 Difference means 40 Excimer laser 41 Beam reducer 42 Speckle pattern removal means 43 Square rod 44 Servo motor 45 Encoder

Claims (17)

A trench depth measuring device for measuring the depth of a trench formed in a sample,
A stage for supporting a sample in which a trench to be depth-measured is formed;
A light source device that generates an illumination beam; and an objective lens that projects the illumination beam toward the sample. A linear pupil pattern parallel to the longitudinal direction of the trench is formed at a pupil position between the light source device and the objective lens. An illumination optical system that forms a line-shaped illumination area that intersects the trench on the sample surface where the trench is formed;
Scanning means for performing Z-axis scanning by changing the relative distance in the optical axis direction between the objective lens and the sample;
Sensor means for detecting the position in the optical axis direction of the objective lens or stage during the Z-axis scan or the distance in the optical axis direction between the objective lens and the stage, and outputting the position information or distance information from the sample surface near the trench A light detecting means for receiving the reflected light from the bottom of the trench and the reflected light from the bottom of the trench through the objective lens;
A trench depth comprising a signal processing device for outputting trench depth information based on a luminance signal output from the light detection means and position information or distance information output from the sensor means. measuring device. 2. The trench depth measuring apparatus according to claim 1, wherein the light source device includes a light source that emits an illumination beam, a cylindrical lens that converts the illumination beam emitted from the light source into a linear illumination beam, and a line that is emitted from the cylindrical beam. Slit means having a slit-like opening for passing a shaped illumination beam,
The trench depth measuring apparatus, wherein the slit means, the sample, and the light detecting means are arranged at conjugate positions. A trench depth measuring device for measuring the depth of a trench formed in a sample,
A stage for supporting a sample in which a trench to be depth-measured is formed;
A light source device that generates a linearly polarized illumination beam, and an objective lens that projects the illumination beam toward the sample, and has a line shape parallel to the longitudinal direction of the trench at the pupil position between the light source device and the objective lens. An illumination optical system that forms a pupil pattern and forms a linear illumination area that intersects the trench on the sample surface on which the trench is formed;
Scanning means for performing Z-axis scanning by changing the relative distance in the optical axis direction between the objective lens and the sample;
Sensor means for detecting the position in the optical axis direction of the objective lens or stage during the Z-axis scan or the distance in the optical axis direction between the objective lens and the stage, and outputting the position information or distance information from the sample surface near the trench A light detecting means for receiving the reflected light from the bottom of the trench and the reflected light from the bottom of the trench through the objective lens;
A signal processing device that outputs the depth information of the trench based on the luminance signal output from the light detection means and the position information or distance information output from the sensor means,
The trench depth measurement apparatus, wherein the direction of the electric field vector of linearly polarized light constituting the illumination beam incident on the sample surface is set substantially parallel to the longitudinal direction of the trench.   4. The trench depth measurement apparatus according to claim 3, wherein a linear illumination beam composed of linearly polarized light is emitted from the illumination optical system, and the extending direction of the linear illumination beam and the direction of the electric field vector are mutually connected. A trench depth measuring device characterized by being substantially orthogonal. 5. The trench depth measurement apparatus according to claim 1, wherein the light source device emits linearly polarized laser light and a laser beam emitted from the laser light source is linearly illuminated. A cylindrical lens for converting into a beam, and slit means having a slit-like opening for passing a linear illumination beam emitted from the cylindrical,
The trench depth measuring apparatus, wherein the slit means, the sample, and the light detecting means are arranged in a conjugate relationship.   The trench depth measuring apparatus according to claim 2 or 5, wherein the signal processing device is configured based on a luminance signal output from a light detection unit and position information output from the sensor unit during a Z-axis scan. A first position in the optical axis direction of the objective lens or stage when the focal point of the objective lens is located on the sample surface around the trench, and the objective lens or stage when the focal point of the objective lens is located at the bottom of the trench Means for determining the second position in the optical axis direction, and means for calculating the distance between the first position and the second position, and between the first position and the second position Is output as the trench depth.   7. The trench depth measurement apparatus according to claim 6, wherein the signal processing apparatus sets a position in the optical axis direction at which the luminance value of reflected light from the sample surface around the trench is maximized during the Z-axis scan as a first position. And a position in the optical axis direction at which the luminance value of reflected light from the bottom of the trench is maximized is detected as the second position.   6. The trench depth measuring apparatus according to claim 5, wherein a speckle pattern removing apparatus for removing or reducing a speckle pattern contained in the laser beam is disposed in an optical path between the cylindrical lens and the slit means. A trench depth measuring apparatus characterized by comprising:   9. The trench depth measuring apparatus according to claim 5, wherein the laser light source is a semiconductor laser, or a pulse oscillation type or continuous type that generates illumination light in an ultraviolet region or a deep ultraviolet region (DUV). A trench depth measuring device comprising an oscillation type excimer laser.   The trench depth measuring apparatus according to any one of claims 1 to 9, wherein a linear illumination beam directed to the sample and reflected light from the sample are included in an optical path between the objective lens and the light detection means. A trench depth measuring apparatus comprising: a beam splitter configured to separate the first and second beam splitters, wherein the beam splitter is configured by a half mirror, and a linearly polarized linear illumination beam is incident on the sample via the objective lens.   The trench depth measuring apparatus according to any one of claims 1 to 10, wherein the light detecting means includes an area sensor in which a plurality of light receiving elements are arranged in a two-dimensional array, or a plurality of light receiving elements. A trench depth measuring apparatus comprising line sensors arranged in a line. A trench depth measurement device that can be switched between an imaging mode for capturing a two-dimensional image of a sample surface on which a trench is formed and a depth measurement mode for measuring the depth of the trench,
A stage for supporting a sample in which a trench to be depth-measured is formed;
An illumination optical system that illuminates the surface of the sample on which the trench is formed, and includes a light source device that generates an illumination beam and an objective lens that projects the illumination beam toward the sample;
Scanning means for performing Z-axis scanning by changing the relative distance in the optical axis direction between the objective lens and the sample;
Sensor means for detecting the position in the optical axis direction of the objective lens or stage during the Z-axis scan or the distance in the optical axis direction between the objective lens and the stage, and outputting as positional information or distance information from the sample surface around the trench A light detecting means for receiving the reflected light from the bottom of the trench and the reflected light from the bottom of the trench through the objective lens;
In the depth measurement mode, trench depth information is output based on the luminance signal output from the light detection means and the position information or distance information output from the sensor means. In the imaging mode, the light detection is performed. A signal processing device for outputting two-dimensional image information of the sample surface based on the luminance signal output from the means,
In the depth measurement mode, the illumination optical system forms a line-shaped pupil pattern parallel to the longitudinal direction of the trench at the pupil position between the light source device and the objective lens, and on the sample surface where the trench is formed. A trench depth measuring apparatus, wherein a line-shaped illumination area intersecting with a trench is formed and a two-dimensional area on a sample surface is illuminated in an imaging mode. 13. The trench depth measurement apparatus according to claim 12, wherein the light source device includes a light source that emits an illumination beam, a cylindrical lens that converts the illumination beam emitted from the light source into a linear illumination beam, and a line emitted from the cylindrical beam. A slit means having a slit-shaped opening for passing a shaped illumination beam, and a bypass optical path means that is selectively disposed in the optical path and bypasses the slit means,
In the imaging mode, a bypass optical path means is inserted in the optical path, and the illumination beam emitted from the cylindrical lens enters the objective lens through the bypass optical path means,
In the depth measurement mode, the bypass optical path means is removed from the optical path, and the linear illumination beam emitted from the cylindrical lens is incident on the objective lens through the slit means.   14. The trench depth measuring apparatus according to claim 13, wherein a laser that generates a linearly polarized illumination beam is used as the light source, and in the depth measurement mode, the direction of the electric field vector of the illumination beam is a trench whose depth is measured. A trench depth measuring device, which is set substantially parallel to the longitudinal direction of the trench. A trench depth measurement method for measuring the depth of a trench formed in a sample,
Forming a line-shaped pupil pattern parallel to the longitudinal direction of the trench at the pupil position between the light source and the objective lens, and forming a line-shaped illumination area intersecting the trench on the sample surface where the trench is formed When,
Performing a Z-axis scan by changing the relative distance between the sample surface and the objective lens;
During the Z-axis scan, the first position indicating the position of the objective lens or stage in the optical axis direction when the focal point of the objective lens is located on the sample surface around the trench, and the focal point of the objective lens on the bottom surface of the trench A position detection step of detecting a second position indicating the position of the objective lens or the stage in the optical axis direction when positioned;
And a step of outputting the detected distance between the first position and the second position as trench depth information.   16. The trench depth measurement method according to claim 15, wherein in the position detection step, a position in the optical axis direction at which the brightness of reflected light from the sample surface is maximum is detected as a first position, and the position from the bottom surface of the trench is detected. A trench depth measuring method, wherein a position in the optical axis direction where the brightness of reflected light is maximum is detected as a second position. A confocal microscope for observing a trench formed in a sample,
A stage that supports the sample in which the trench to be observed is formed;
A light source device that generates an illumination beam; and an objective lens that projects the illumination beam toward the sample. A linear pupil pattern parallel to the longitudinal direction of the trench is formed at a pupil position between the light source device and the objective lens. An illumination optical system that forms a line-shaped illumination area that intersects the trench on the sample surface where the trench is formed;
Scanning means for relatively scanning the illumination beam within a sample surface including the trench;
Light detection means for receiving reflected light from the trench portion through the objective lens;
A confocal microscope, comprising: a signal processing device that forms a two-dimensional image of a sample surface including a trench based on a luminance signal output from a light detection means.

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