JP5416025B2 - Surface shape measuring device and semiconductor wafer inspection device - Google Patents

Description

  The present invention relates to a surface shape measuring device that measures the surface shape of a semiconductor wafer and a semiconductor wafer inspection device that includes this surface shape measuring device and inspects the quality of the surface shape of a semiconductor wafer.

  In recent years, integrated circuits have been integrated. A process rule, which is a process condition for manufacturing this integrated circuit on a semiconductor wafer, is usually defined by a minimum processing dimension in the line width or interval of the gate wiring. If this process rule is halved, theoretically, four times as many transistors and wirings can be arranged in the same area, so the area is ¼ with the same number of transistors. As a result, not only the number of dies that can be manufactured from a single semiconductor wafer is quadrupled, but also the yield is usually improved, so that more dies can be manufactured. This minimum feature size has reached 45 nm at the forefront of 2007 to produce high density integrated circuits. In such a sub-micron order (1 μm or less) process rule, a semiconductor wafer is required to have high flatness, and the surface shape (change in surface height) of the semiconductor wafer cannot be ignored. For this reason, a surface shape measuring device that measures the surface shape of a semiconductor wafer with high accuracy, for example, in the order of nanometers is desired.

  In addition, the flatness of the surface shape of a semiconductor wafer is generally inferior to the outer edge portion than the center portion because a shape called edge roll-off exists at the outer edge portion. In order to extend the manufacturable area of the die in the semiconductor wafer to the outer edge, the evaluation of this edge roll-off is important, and for this purpose, a surface shape measuring device that measures the surface shape of the semiconductor wafer with high accuracy is desired. .

  As a shape measuring method for measuring the surface shape, an interferometer method and a light cutting method are generally known. This interferometer method is disclosed in, for example, Non-Patent Document 1, and the light emitted from the light source is divided into, for example, two lights by a dividing unit, and after passing through separate optical paths, the two lights are separated. Are overlapped again by the combining means, the interference fringes generated by the optical path difference are detected by the detecting means, and the surface shape of the measurement object is obtained by analyzing the interference fringes. As a method using such an interferometer, a method using a Fizeau interferometer, a Michelson interferometer, an oblique incidence interferometer, or the like is known. Further, a method based on the light cutting method is disclosed in Non-Patent Document 2, for example, a fan-shaped sheet light emitted from a light source is irradiated onto an object to be measured, and the sheet light is photographed by photographing means. The surface shape of the measurement object is obtained by analyzing the bright line caused by the sheet light in the obtained image by the analyzing means.

Fujinon Corporation, “Laser Interferometer Usage Guide”, [online], February 19, 2009 search, Internet, <http: // www. fujinon. co. jp / jp / products / laser / kisotisiki2. htm> Optware Corporation, “High-speed optical cutting method profile measurement system”, [online], search on February 19, 2009, Internet, <http: // www. optware. co. jp / densen. pdf>

  By the way, in the method using an interferometer, the measurement range is about the length of the wavelength, that is, only several hundred nanometers, and the measurement of the surface shape of the semiconductor wafer is restricted. In this interferometer method, if the measurement range is to be expanded in order to eliminate the restriction, it is necessary to phase link the measurement distances. This also complicates information processing and takes time for the information processing. Further, in the measurement of the surface shape of the semiconductor wafer, it is necessary to measure several tens to several hundreds of points only by measuring the edge portion. If time is required for measurement, the entire measurement time becomes long.

  In addition, the optical cutting method generally has a measurement accuracy of about several μm at most because of its principle. On the other hand, since the surface of the semiconductor wafer is required to have a high flatness as described above, it is necessary to measure the surface shape of the semiconductor wafer on the order of nanometers. It is not suitable for the measurement of surface shape.

  The present invention has been made in view of the above-described circumstances, and its purpose is to measure the surface shape of a semiconductor wafer in an accuracy suitable for measuring the surface shape of a semiconductor wafer and in a shorter time. It is to provide a surface shape measuring device and a semiconductor wafer inspection device that can be used.

As a result of various studies, the present inventor has found that the above object is achieved by the present invention described below. That is, the surface shape measuring apparatus according to an aspect of the present invention includes a light irradiation unit that irradiates a surface of a semiconductor wafer that is a measurement target with plane wave measurement light having a plane wavefront whose normal is a traveling direction ; A Shack-Hartmann wavefront sensor that measures the shape of the wavefront in the reflected light of the measurement light reflected from the surface of the semiconductor wafer, and the wavefront sensor based on the shape of the wavefront in the reflected light measured by the wavefront sensor A surface shape calculation unit for obtaining a surface shape of a semiconductor wafer, wherein the Shack-Hartmann wavefront sensor receives the reflected light and includes a plurality of lenses arranged in an array, and the lens array an imaging unit that captures an image of the reflected light having passed through the plurality of lenses in a predetermined threshold value among the image data captured by the imaging unit A data extraction processing unit which extracts the data above, the data extraction processing unit based on the extracted data with a wavefront computing section for obtaining the wavefront shape of the reflected light, of the predetermined in the data extraction processing unit threshold, characterized by values der Rukoto corresponding to the distance from the edge of the semiconductor wafer.

  Since the surface shape measuring apparatus having such a configuration measures the shape of the surface of the semiconductor wafer (surface shape) by using the wavefront sensor, from the measurement principle, with the accuracy suitable for the measurement of the surface shape of the semiconductor wafer, Then, the surface shape of the semiconductor wafer can be measured in a shorter time.

Then, according to this configuration, the surface shape measuring apparatus using the wavefront sensor of the Shack-Hartmann (Shack-Hartmann) scheme is provided to the wavefront sensor.

Further , according to this configuration, in the image picked up by the image pickup unit, the image pickup unit detects the position of each light spot of the reflected light collected by each of the plurality of lenses in the lens array. Since the predetermined threshold value used when extracting data from the captured image data is a value corresponding to the distance from the end portion of the semiconductor wafer, the predetermined threshold value is a surface of a region near the end portion of the semiconductor wafer. Since the position is adaptively changed according to the shape, the position of each light spot of the reflected light can be detected with higher accuracy. As a result, the surface shape measuring apparatus having such a configuration can more accurately measure the surface shape of the semiconductor wafer, particularly the surface shape of the end region of the semiconductor wafer.

  According to another aspect, in the above-described surface shape measuring device, the reflected light is branched into a plurality of branches, and one of the plurality of branched lights is incident on the wavefront sensor; An imaging unit that images the surface of the semiconductor wafer so as to include at least an end of the semiconductor wafer by receiving another one of the branched lights, and a surface of the semiconductor wafer imaged by the imaging unit And a coordinate position calculation unit that obtains the coordinate position of the measurement location based on the image.

  The position of the measurement location can be obtained, for example, according to the amount of movement of the stage on which the semiconductor wafer to be measured is placed. According to this configuration, the reflected light is branched into a plurality of branched lights by the branching unit. One of the plurality of branched lights is received by the wavefront sensor, and the other one of the plurality of branched lights is received by the imaging unit, whereby the surface of the semiconductor wafer is imaged by the imaging unit. The coordinate position calculation unit determines the coordinate position of the measurement location based on the surface image of the semiconductor wafer. For this reason, the surface shape measuring apparatus of such a structure can recognize the position of the measurement location on a semiconductor wafer more correctly.

  In another aspect, the above-described surface shape measurement apparatus further includes a thickness distribution measurement unit that measures the thickness distribution of the semiconductor wafer by using heterodyne interferometry.

  According to this configuration, there is provided a surface shape measuring apparatus capable of measuring not only the surface shape of the semiconductor wafer but also the thickness distribution of the semiconductor wafer.

  According to another aspect, in the above-described surface shape measuring apparatus, the light irradiation unit irradiates measurement light having a predetermined wavefront on one surface of the semiconductor wafer, and the wavefront sensor Measuring the shape of the wavefront in the reflected light of the measurement light reflected on one surface, and the surface shape calculation unit is configured to measure one surface of the semiconductor wafer based on the shape of the wavefront in the reflected light measured by the wavefront sensor. And determining the surface shape of the semiconductor wafer based on the surface shape on one surface of the semiconductor wafer determined by the surface shape calculating unit and the thickness distribution of the semiconductor wafer measured by the thickness distribution measuring unit. It is further characterized by further comprising a second surface shape calculation unit for obtaining a surface shape on the other surface.

  According to this configuration, the other surface shape of the semiconductor wafer is obtained by the second surface shape calculation unit. For this reason, the surface shape measuring apparatus of such a structure can measure each surface shape of both front and back surfaces of a semiconductor wafer.

  The semiconductor wafer inspection apparatus according to another aspect of the present invention includes a surface shape measuring unit that measures a surface shape on the surface of a semiconductor wafer that is a measurement target, and a surface shape measured by the surface shape measuring unit is predetermined. A determination unit that determines whether or not the condition is satisfied and an output unit that outputs a determination result by the determination unit, and the surface shape measurement unit is any one of the above-described surface shape measurement devices.

  According to this configuration, since any one of the above-described surface shape measuring devices is used, the surface shape of the semiconductor wafer can be measured with a precision suitable for measuring the surface shape of the semiconductor wafer in a shorter time. Therefore, the semiconductor wafer inspection apparatus having such a configuration can inspect the quality of the semiconductor wafer more speedily and more accurately. Therefore, the semiconductor wafer inspection apparatus having such a configuration can be suitably used, for example, in a production line of products using semiconductor wafers, and selects semiconductor wafers that do not meet the required specifications (specs) in the manufacturing process. As a result, the yield of the product is improved, and as a result, the cost can be reduced.

  The surface shape measuring device and the semiconductor wafer inspection device according to the present invention can measure the surface shape of the semiconductor wafer in a shorter time with accuracy suitable for measuring the surface shape of the semiconductor wafer.

It is a figure which shows the structure of the surface shape measuring apparatus in 1st Embodiment. It is a figure which shows the wavefront sensor of the 1st aspect in the surface shape measuring apparatus of 1st Embodiment. It is a figure for demonstrating the measurement principle in the wavefront sensor of a 1st aspect. It is a figure for demonstrating the calculation formula of the wavefront angle in the wavefront sensor of a 1st aspect. It is a figure which shows the wavefront sensor of the 2nd aspect in the surface shape measuring apparatus of 1st Embodiment. It is a figure which shows the wavefront sensor of the 3rd aspect in the surface shape measuring apparatus of 1st Embodiment. It is a figure for demonstrating the image image | photographed by the imaging | photography part in the surface shape measuring apparatus of 1st Embodiment. It is a flowchart which shows operation | movement of the surface shape measuring apparatus in 1st Embodiment. In operation | movement of the surface shape measuring apparatus of 1st Embodiment, it is a figure which shows the main process results. It is a figure for demonstrating the predetermined threshold value in the data extraction process of a wavefront sensor. It is a figure for demonstrating the calculation method which calculates | requires the surface shape of a measuring object from the wavefront shape measured with the wavefront sensor. It is a figure which shows the structure of the surface shape measuring apparatus in 2nd Embodiment. It is a figure which shows the structure of the thickness distribution measurement part in the surface shape measuring apparatus of 2nd Embodiment. In the surface shape measuring apparatus of 2nd Embodiment, it is a figure for demonstrating the method of calculating | requiring the other surface shape based on one surface shape and thickness distribution. It is a figure which shows the structure of the semiconductor wafer inspection apparatus in 3rd Embodiment. It is a figure for demonstrating edge roll-off.

  Hereinafter, an embodiment according to the present invention will be described with reference to the drawings. In addition, the structure which attached | subjected the same code | symbol in each figure shows that it is the same structure, The description is abbreviate | omitted suitably. Further, in this specification, when referring generically, it is indicated by a reference symbol without a suffix, and when referring to an individual configuration, it is indicated by a reference symbol with a suffix.

(First embodiment)
FIG. 1 is a diagram illustrating a configuration of a surface shape measuring apparatus according to the first embodiment. FIG. 2 is a diagram illustrating a wavefront sensor according to a first aspect of the surface shape measuring apparatus according to the first embodiment. FIG. 2A shows the configuration of the wavefront sensor of the first aspect, and FIG. 2B shows a plan view of the microlens array. FIG. 3 is a diagram for explaining the measurement principle in the wavefront sensor of the first aspect. 3A shows a case where the wavefront of incident light is not distorted (in the case of a plane wave), and FIG. 3B shows a case where the wavefront of incident light is distorted. FIG. 4 is a diagram for explaining a calculation formula of the wavefront angle in the wavefront sensor of the first aspect. FIG. 5 is a diagram illustrating the wavefront sensor of the second aspect in the surface shape measurement apparatus of the first embodiment. FIG. 6 is a diagram illustrating a wavefront sensor according to a third aspect of the surface shape measuring apparatus according to the first embodiment. FIG. 7 is a diagram for explaining an image photographed by the photographing unit in the surface shape measuring apparatus according to the first embodiment.

  As shown in FIGS. 1 and 2, the surface shape measuring apparatus Sa of the first embodiment includes a light source unit 1, an optical path changing unit 2, an optical branching unit 3, a wavefront sensor 4, and an arithmetic control unit 7a. In the example shown in FIG. 1, the image capturing unit 5 is further provided to obtain the coordinate position of the measurement location MP, and an input unit is provided to input a predetermined command, data, or the like to the surface shape measurement apparatus Sa. 6, an output unit 8 for outputting the predetermined command and data input from the input unit 6 and the measurement result of the surface shape measuring device Sa, and the like to change the measurement point MP A stage 9 is provided.

  The light source unit 1 is a device that emits measurement light having a predetermined wavefront, which is controlled by the arithmetic control unit 7a, and is, for example, a xenon lamp or a laser device. The predetermined wavefront may be known in advance, but is preferably a plane wave having a flat wavefront whose normal is the traveling direction. In the present embodiment, a helium neon laser device (He—Ne laser device) is used for the light source unit 1, and the laser beam from the He—Ne laser device is expanded into parallel light having a beam diameter of 20 mm by a beam expander. Used as measurement light.

  The optical path changing unit 2 receives the measurement light emitted from the light source unit 1 and directs the optical path of the measurement light emitted from the light source unit 1 toward the measurement target SW so as to irradiate the measurement target SW with the measurement light. The optical element to be changed. In the present embodiment, the wavefront sensor 4 is disposed in the normal direction of the measurement surface of the measurement object SW, and the light source unit 1 is disposed on the side surface in the normal direction, for example, from a direction orthogonal to the normal direction. In order to irradiate measurement light, the optical path changing unit 2 includes a half mirror 2. As shown in FIG. 1, the measurement light emitted from the light source unit 1 is incident on the half mirror 2, the optical path thereof is bent by approximately 90 degrees by the half mirror 2, and the measurement target SW is measured from the normal direction of the measurement target SW. The predetermined measurement point MP is irradiated. The measurement light irradiated to the measurement point MP of the measurement object SW is reflected by the measurement object SW, and is incident on the half mirror 2 again and reflected by the measurement light transmitted through the half mirror 2, as shown in FIG. Is incident on the optical branching unit 3.

  The measurement object SW is, for example, a semiconductor wafer SW such as a silicon wafer (for example, a silicon wafer for solar cells).

  The light branching unit 3 is an optical element that splits the reflected light of the measurement light, which is incident on the half mirror 2 and reflected by the surface of the measurement object SW, into two, and includes, for example, a half mirror 3. The The reflected light of the measurement light that has entered through the half mirror 2 and reflected by the surface of the measurement object SW is branched into two by the half mirror 3, one of which is incident on the wavefront sensor 4, and the other is The light enters the imaging unit 5.

  The wavefront sensor 4 is a device that measures the shape of the wavefront in the reflected light of the measurement light that is controlled by the arithmetic control unit 7a and reflected by the surface of the measurement object SW. The shape of the wavefront of the reflected light measured by the wavefront sensor 4 is output to the arithmetic control unit 7a. There are mainly three methods for the wave front sensor 4 for measuring the wavefront of light.

  The first technique is called a Shack-Hartmann wave-front sensor, and in the example shown in FIGS. 1 and 2, this Shack-Hartmann wave-front sensor 4 is used. As shown in FIG. 2, the Shack-Hartmann wavefront sensor is arranged behind the pupil, and a microlens in which a plurality of microlenses 411 (see FIG. 2B) are arranged in an array, for example, in a two-dimensional array. An array 41, an image sensor 42 that captures an image by converting an optical image such as a CCD area sensor (CCD image sensor) or a CMOS area sensor (CMOS image sensor) into an electrical signal, and an image sensor And a wavefront sensor calculation control unit 43 that obtains a wavefront of incident light (the reflected light in the present embodiment) by performing predetermined processing on the output of 42.

  The Shack-Hartmann wavefront sensor 4 having such a configuration receives incident light (reflected light of the measurement light in this embodiment) incident on the sensor 4 by the microlens array 41, and An image of the incident light that has passed through the microlens 411, for example, an image of the incident light that is formed by each microlens 411 in the microlens array 41 is picked up by the image pickup element 42, and the image of the picked up incident light is wavefront sensor. The wavefront of the incident light is obtained by analysis by the arithmetic control unit 43. In the Shack-Hartmann wavefront sensor 4, when the incident light is a plane wave, as shown in FIG. 3A, each microlens 411 corresponds to each optical axis of each microlens 411 in the imaging device 42. In each of the positions (each reference position), an image of the incident light (light spot, spot, dot, represented by “•” in the figure) is formed, while on the other hand, the incident light is not a plane wave but is distorted. As shown in FIG. 3B, in the image sensor 42, the image (•) of the incident light is placed at each position (each observation position) that is shifted from each reference position corresponding to each microlens 411 by each microlens 411. Imaged. The amount of deviation from the reference position at the observation position is generated according to the amount of distortion (wavefront angle) generated in the wavefront of the incident light. For this reason, the wavefront of the incident light is obtained by obtaining the deviation amount.

More specifically, when the distance between the microlens array 41 and the image sensor 42 is F, and the distance between the observation position and its reference position (the shift amount) is L, it is shown in FIG. Thus, from the geometric relationship, the angle of the wavefront of the incident light to be measured with respect to the wavefront of the plane wave perpendicularly incident on the microlens array 41 (the wavefront of the plane wave perpendicularly incident on the microlens array 41 and the incident light to be measured The wavefront angle α, which is the angle formed by the wavefront, is expressed by tan α = L / F and is calculated by α = tan ⁻¹ (L / F).

  The wavefront sensor calculation unit 43 that calculates the wavefront of the incident light by calculating in this way, that is, the reflected wave of the measurement light reflected by the measurement object SW in this embodiment, includes, for example, a microcomputer. As shown in FIG. 2A, for example, the image is functionally captured by the reference position storage unit 434 that stores each reference position corresponding to each microlens 411 of the microlens array 41 and the imaging element 42. Based on an image (image) of the incident light (reflected light in the present embodiment), an observation position calculation unit 431 that obtains each observation position corresponding to each microlens 411, and each observation position obtained by the observation position calculation unit 431 And a wavefront angle calculation unit 432 for determining a wavefront angle α based on a deviation amount L between the observation position and its reference position, and a wavefront angle calculation unit. 32 constituted by a wavefront shape operation unit 433 for obtaining the wavefront shape of the incident light (reflected light in this embodiment) based on the wavefront angle α obtained by the.

  The second technique is called LSI (Lateral Shearing Interferometer), and as shown in FIG. 5, the wavefront φ (r) incident on the wavefront sensor is shifted by a predetermined value s by a shearing device. It is divided into light having φ (r) and light having wavefront φ (r + s), and an optical image of these lights is picked up by an image pickup device, and an interference pattern (interference fringes) shown in the picked-up light image of the light is obtained. The wavefront phase of the incident light is obtained by analysis.

  The third method is called a curvature sensor, and as shown in FIG. 6, incident light incident on the wavefront sensor is received by a lens arranged behind the pupil, The incident light wavefront is obtained by imaging each image of the incident light with two image pickup elements at two positions deviated from the focal position f by an equal distance l, and comparing and analyzing each of the captured images. is there. In the curvature sensor, when the incident light is a plane wave, each image of the incident light is similarly blurred. On the other hand, when the incident light is not a plane wave but is distorted, the incident light Each of the images becomes a different image. The difference between the images of the incident light occurs according to the amount of distortion generated in the wavefront of the incident light. For this reason, the wavefront of the incident light is obtained by obtaining the difference between the images of the incident light.

  The photographing unit 5 is a device that is controlled by the arithmetic control unit 7a and photographs the measurement object SW. When the coordinate position of the measurement point MP is obtained based on the image of the measurement object SW photographed by the photographing unit 5, the measurement object SW includes at least an end portion of the semiconductor wafer SW that is the measurement object SW. The surface is photographed by the photographing unit 5. That is, as shown in FIG. 7, the image PC by the imaging unit 5 is an image of the surface of the semiconductor wafer SW when the measurement object SW is imaged from the normal direction, and the image PC includes the semiconductor wafer SW. End SWEg. The imaging unit 5 performs predetermined processing on, for example, an optical system, an image sensor that captures an image formed by converting the optical image formed by the optical system into an electrical signal, and an output of the image sensor. Thus, the camera includes an image processing unit that generates an image of the optical image. The image photographed by the photographing unit 5 is output to the arithmetic control unit 7a.

  The input unit 6 is connected to the calculation control unit 7a and is a device for inputting commands (commands), data, and the like from the outside to the surface shape measuring device Sa, and is, for example, a touch panel or a keyboard. The output unit 8 is connected to the calculation control unit 7a, and is a device for outputting commands and data input from the input unit 6, calculation results of the calculation control unit 7a, and the like. For example, a CRT display or LCD (liquid crystal display) And a display device such as an organic EL display and a printing device such as a printer.

  The stage 9 is a device that is controlled by the arithmetic control unit 7a and moves the measurement object SW in a horizontal direction orthogonal to the thickness direction of the measurement object SW.

  The arithmetic control unit 7 a is a circuit that controls each part of the surface shape measuring device Sa according to the function, and obtains the surface shape of the measurement object SW based on the output of the wavefront sensor 4. The calculation control unit 7a is, for example, a control program for controlling each part of the surface shape measuring device Sa according to the function or various calculation programs such as a calculation program for obtaining the surface shape of the measurement object SW based on the output of the wavefront sensor 4. ROM (Read Only Memory) which is a non-volatile storage element and rewritable non-volatile storage for storing various predetermined data such as data required for execution of the predetermined program An EEPROM (Electrically Erasable Programmable Read Only Memory) that is an element, a CPU (Central Processing Unit) that performs predetermined arithmetic processing and control processing by reading and executing the predetermined program, and data generated during execution of the predetermined program RAM (Random Access Memory) that serves as the working memory of the CPU for storing It constituted by a microcomputer or the like provided with peripheral circuits al. The calculation control unit 7a functionally includes a first surface shape calculation unit 71, a coordinate position calculation unit 72, an entire surface shape calculation unit 73, and a control unit 74.

  The first surface shape calculation unit 71 obtains the surface shape of the measurement object SW based on the wavefront shape of the reflected light of the incident light measured by the wavefront sensor 4.

  The coordinate position calculation unit 72 obtains the coordinate position of the measurement location MP based on the surface image of the measurement object SW photographed by the photographing unit 5.

  The total surface shape calculation unit 73 calculates the shape of the entire surface (total surface shape) of the measurement object SW in the desired measurement range based on the surface shape calculated by the first surface shape calculation unit 71.

  The control unit 74a controls each of the light source unit 1, the wavefront sensor 4, the imaging unit 5, and the stage 9 according to the function of each unit.

  Note that the surface shape measuring device Sa may further include an external storage device as necessary. This external storage device is an auxiliary storage device that is connected to the arithmetic control unit 7a and reads / writes data from / to a storage medium such as a flexible disk, CD-R (Compact Disc Recordable) and DVD-R (Digital Versatile Disc Recordable), For example, a flexible disk drive, a CD-R drive, a DVD-R drive, and the like. When the predetermined program, the predetermined data, and the like are not stored in the arithmetic control unit 7a, the surface shape measuring device is configured to read the recording medium on which these are recorded into the arithmetic control unit 7a via the external storage device. Sa may be configured.

  Next, operation | movement of the surface shape measuring apparatus Sa in 1st Embodiment is demonstrated. FIG. 8 is a flowchart showing the operation of the surface shape measuring apparatus according to the first embodiment. FIG. 9 is a diagram showing main processing results in the operation of the surface shape measuring apparatus according to the first embodiment. FIG. 9A shows an image (acquired image) acquired by the wavefront sensor 4, and FIG. 9B shows an image (spot data) after the data extraction processing in the wavefront sensor 4, FIG. ) Shows the wavefront shape of the reflected wave in the line AA shown in FIG. 9A obtained by the wavefront sensor 4, and FIG. 9D shows the wavefront shape obtained by the first surface shape calculation unit 71. The surface shape of the measuring object SW based on the wavefront shape of the reflected wave shown in FIG. FIG. 10 is a diagram for explaining a predetermined threshold in the data extraction process of the wavefront sensor. FIG. 10A shows an image before data extraction processing, which is picked up by the image pickup element 42 of the wavefront sensor 4, and FIG. 10B shows the luminance values on the BB line shown in FIG. Each threshold value of the third aspect is shown. In FIG. 10B, the horizontal axis represents the X coordinate, and the vertical axis represents the luminance value at the coordinate position. The X coordinate is set along the radial direction with a predetermined position set to 0 near the end (edge) of the measurement object SW. A broken line indicates a threshold value of the first aspect (when applying an inclination), a one-dot chain line indicates a threshold value of the second aspect (when calculated for each section), and a two-dot chain line indicates a threshold value of the third aspect (Constant case) FIG. 11 is a diagram for explaining a calculation method for obtaining the surface shape of the measurement object from the wavefront shape measured by the wavefront sensor.

  When a power switch (not shown) is turned on, the surface shape measuring device Sa is activated, and necessary parts are initialized by the arithmetic control unit 7a. Then, for example, when the measurement object SW of a plate-like body such as a semiconductor wafer is placed on the stage 9 and receives a command for instructing the start of measurement from the input unit 6, the arithmetic control unit 7a Start measuring.

  First, the control unit 74a of the calculation control unit 7a drives the light source unit 1 to cause the light source unit 1 to emit measurement light.

  As shown in FIG. 1, the measurement light emitted from the light source unit 1 is incident on the half mirror 2, the optical path thereof is bent by approximately 90 degrees by the half mirror 2, and the measurement target SW is measured from the normal direction of the measurement target SW. The predetermined measurement point MP is irradiated. The measurement light irradiated to the measurement point MP of the measurement object SW is reflected by the measurement object SW, and is incident on the half mirror 2 again and reflected by the measurement light transmitted through the half mirror 2, as shown in FIG. Is incident on the half mirror 3. In the half mirror 3, the reflected light of the measurement light is branched into two, one of which is incident on the wavefront sensor 4 and the other is incident on the imaging unit 5.

  Based on the image photographed by the photographing unit 5, the control unit 74a of the arithmetic control unit 7a moves the measurement object SW by the stage 9 so that this image includes at least the end of the measurement object SW. The arithmetic control unit 7a uses, for example, the difference between the luminance of the measurement object SW and the luminance of the external part of the measurement object SW, so that the end of the measurement object SW is based on the image photographed by the photographing unit 5. Part can be detected. An image processing method such as so-called edge detection, which is a well-known conventional means, is used as a method for detecting the end of the measurement object SW. As a result, the initial position of the measurement object SW is determined, and the first measurement point MP is determined.

  When the initial position of the measurement object SW is determined, the measurement of the surface shape of the measurement object SW is disclosed for the first measurement point MP. That is, first, the wavefront sensor 4 receives the reflected light of the measurement light, and acquires an image of the reflected light of the measurement light (S11). More specifically, in the wavefront sensor 4, the reflected light of the measurement light passes through the microlens array 41 and is condensed, and an image of the reflected light of the measurement light is formed on the imaging surface of the image sensor 42. The The image sensor 42 converts the signal into an electrical signal corresponding to the amount of received light, and outputs an electrical signal of an image corresponding to the reflected light image of the measurement light to the wavefront sensor calculation control unit 43. The wavefront sensor calculation control unit 43 takes in the electrical signal of the image from the image sensor 42 and acquires the image through the microlens array 41 in the reflected light of the measurement light. For example, the image shown in FIG. 9A is acquired.

  Subsequently, in the wavefront sensor 4, the observation position calculation unit 431 of the wavefront sensor calculation control unit 43 calculates the luminance value of each pixel of the image so as to obtain each observation position corresponding to each microlens 411 based on the image. Data that is compared with a predetermined threshold value, extracts pixel data whose luminance value is equal to or higher than the predetermined threshold value, and thereby extracts data equal to or higher than the predetermined threshold value from the image data captured by the image sensor 42. An extraction process is performed (S12). By applying such data extraction processing to the image, noise is divided into a non-processing target region and a processing target region, for example, an image shown in FIG. 9A (obtained from the image sensor 42). 9B, the image of the measurement light reflected by each microlens 411 of the microlens array 41 becomes clearer, which causes each microlens 411 to have a clear image. Each corresponding observation position can be detected with higher accuracy.

  Here, the predetermined threshold value in the data extraction process may be a predetermined constant value set in advance as shown by a two-dot chain line in FIG. It may be variable according to the surface shape or surface state of the wafer SW.

  As will be described later, in the semiconductor wafer SW that is the measurement object SW, there is a so-called edge roll-off shape in the vicinity of the end portion. Generally, the end region is in the normal direction of the semiconductor wafer SW. It is curved with respect to the horizontal direction orthogonal to (vertical direction, thickness direction). For this reason, the measurement light incident on the semiconductor wafer SW is reflected in a direction symmetrical with respect to the incident direction with respect to the normal direction of the tangential plane on the surface of the semiconductor wafer SW. The reflected light of the measurement light incident on 4 is light density of the reflected light of the measurement light in the end region compared to the reflected light of the measurement light in the region inside the end region. Drops and darkens.

  For this reason, it is preferable that the predetermined threshold value is set to a value corresponding to the distance from the end of the semiconductor wafer SW. For example, as shown by a broken line in FIG. 10B, the predetermined threshold value is a predetermined constant value in a portion inside the end region, and in the end region, the predetermined threshold value is increased toward the end portion. It may be set in advance so as to gradually change from a predetermined constant value to a small value. By setting the predetermined threshold in this way, the predetermined threshold is adaptively changed according to the surface shape of the end region in the semiconductor wafer SW, so that the reflected light image (light spot) The position can be detected with higher accuracy. As a result, the surface shape measuring apparatus Sa having such a configuration can more accurately measure the surface shape of the semiconductor wafer SW, particularly the surface shape of the end region of the semiconductor wafer SW.

  Alternatively, the predetermined threshold value is preferably a value relating to an average luminance value within a predetermined range area including the measurement location MP. For example, the predetermined threshold value may be an average luminance value obtained by averaging the luminance values of the peripheral pixels of a pixel on which data extraction processing is performed, as indicated by a one-dot chain line in FIG. Peripheral pixels are pixels that exist within a predetermined number of pixels, centering on the pixel that performs data extraction processing. The value relating to the average luminance value may be not only a value obtained by such a simple average but also a value obtained by a weighted average, and the average luminance value is multiplied by a preset coefficient. A look-up table showing the correspondence between the value obtained by this and the average luminance value and the predetermined threshold is prepared in advance, and the value obtained by referring to this look-up table from the average luminance value. Also good. Since the predetermined threshold value is set in this way, the predetermined threshold value is adaptively changed according to, for example, the state of the surface of the semiconductor wafer SW, noise, and the like. Can be detected with higher accuracy. As a result, the surface shape measuring device Sa having such a configuration can measure the surface shape of the semiconductor wafer SW with higher accuracy.

  When such a data extraction process is performed, the observation position calculation unit 431 of the wavefront sensor calculation control unit 43 then identifies and identifies the pixels with high luminance values in the image in order to individually identify them. The spot recognition number as an identifier is numbered (S13). In the case of performing spot recognition numbering, when pixels with high luminance values are adjacent to each other, such pixels are treated as one region having high luminance values. The same spot recognition number is assigned to each pixel. For example, each such pixel is associated with each other, and a single spot recognition number is assigned to it.

  Subsequently, the observation position calculation unit 431 of the wavefront sensor calculation control unit 43 obtains the position of the pixel having a high luminance value for each spot recognition number, and obtains the observation position. Here, as described above, when pixels having a high luminance value are adjacent to each other and one region having a high luminance value is formed by a plurality of pixels, the position of the center of gravity is, for example, geometrical. The obtained center of gravity is set as the observation position (S14). Through such processing, the observation position calculation unit 431 of the wavefront sensor calculation control unit 43 obtains the observation position for each microlens 411 with respect to the reflected light image of the measurement light corresponding to the microlens 411. It is done.

Subsequently, the wavefront angle calculation unit of the wavefront sensor calculation control unit 43 obtains a deviation amount L between the observation position obtained in step S14 and the corresponding reference position for each spot recognition number, and this deviation amount L And the distance F between the microlens array 41 and the image sensor 42, the wavefront angle α is obtained by α = tan ⁻¹ (L / F) (S15). The reference position is stored in advance in the reference position storage unit 434 as described above. The reference position is given, for example, as an intersection between the optical axis of the microlens 411 and the imaging surface of the imaging element 42. Further, for example, the reference position is obtained in advance by measuring the reference portion having a highly flat surface, for example, the central portion of the semiconductor wafer SW with the wavefront sensor 4.

  If the measurement light is not a plane wave but a light having a predetermined wavefront, the deviation L may be corrected according to the difference between the predetermined wavefront and the wavefront of the plane wave.

  Subsequently, the wavefront shape calculation unit 433 of the wavefront sensor calculation control unit 43 obtains the wavefront shape in the reflected light of the measurement light (S16). For example, the wavefront shape calculation unit 433 sequentially couples the wavefront angles α of the respective spot identification numbers along the radial direction of the semiconductor wafer SW, thereby reflecting the reflected light of the measurement light along the radial direction of the semiconductor wafer SW. Find the wavefront shape. By such information processing, for example, from the image after the data extraction processing shown in FIG. 9B, the wavefront shape in the reflected light of the measurement light at the AA line along the radial direction of the semiconductor wafer SW is obtained as shown in FIG. The shape shown in (C) is obtained.

  Thus, in the wavefront sensor 4, the reflected light of the measurement light is incident, the reflected light is received by the microlens array 41, and an image of the reflected light that has passed through the plurality of microlenses 411 in the microlens array 41 is obtained. An image picked up by the image pickup device 42 and an image picked up by the image pickup device 42 is extracted by the observation position calculation unit 431 as an example of a data extraction processing unit based on the predetermined threshold, and based on the extracted data, The wavefront angle calculation unit 432 and the wavefront shape calculation unit 433 as examples of the wavefront calculation unit obtain the shape of the wavefront in the reflected light. Then, the obtained wavefront shape of the reflected light of the measurement light is output from the wavefront sensor 4 to the arithmetic control unit 7a.

  Subsequently, when the calculation control unit 7 a acquires the wavefront shape in the reflected light of the measurement light from the wavefront sensor 4, the wavefront in the reflected light of the measurement light measured by the wavefront sensor 4 by the first surface shape calculation unit 71. Based on the shape, the surface shape of the measuring object SW is obtained (S17). More specifically, as shown in FIG. 11, a coordinate system X is set along a predetermined direction in the measurement object SW, for example, along the radial direction. When the coordinate system of the wavefront sensor 4 is X0, a tangent plane (tangent) to the wavefront of the reflected light at the position x0 in the coordinate system X0 is obtained, and the normal of this tangential plane (tangent) and X0 = x0 An angle θ (x0) formed with the straight line is obtained. Assuming that the distance between the measurement object SW and the light receiving surface of the microlens array 41 in the wavefront sensor 4 is D, the surface angle φ, which is the angle between the tangent plane (tangent line) on the surface of the measurement object SW and the horizontal direction. (X) is obtained by φ (x) = θ (x0) / 2 and x = x0 + Dtanθ (x0). The distance D is usually about 100 mm, while the surface shape is on the order of nanometers (change from about submicron to several microns in the entire measurement range (frame range)), so the object to be measured with respect to the distance D Since the thickness of the object SW can be assumed to be constant, the thickness of the measurement object SW is subtracted from the distance between the mounting surface of the stage 9 and the light receiving surface of the microlens array 41 in the wavefront sensor 4. A distance D is determined. Then, the surface shape Φ of the measurement object SW is obtained by integrating the surface angle φ (x) with respect to x in a predetermined measurement range (Φ (x) = ∫φ (x) dx). By such information processing, for example, the shape shown in FIG. 9D is obtained as the surface shape of the measurement object SW from the wavefront shape of the reflected light of the measurement light shown in FIG.

  When a plurality of X coordinates can be set in the image obtained from the measurement location MP (when there are a plurality of spot rows arranged in the radial direction in the circumferential direction), the step is performed for each of the plurality of X coordinates. The process of S17 is performed, and the surface shape Φ of each measurement object SW is obtained.

  When each process of step S11 thru | or step S17 is performed about the first measurement location MP (0), and the surface shape (PHI) (0) of measurement object SW is measured about the first measurement location MP (0), The control unit 74a of the calculation control unit 7a operates the stage 9 to measure the surface shape Φ (1) of the measurement object SW at the next measurement location MP (1), and moves the measurement object SW by a predetermined distance. The measurement object SW is set at the next measurement location MP (1). And each process of said step S11 thru | or step S17 is performed about this next measurement location MP (1), and surface shape (PHI) (1) of measurement object SW is measured about this next measurement location MP (1). The By such processing, the surface shapes Φ (0), Φ (1),..., Φ (k) in the desired measurement range are obtained for the measurement object SW. The desired measurement range may be the entire surface of the measurement object SW or a partial surface thereof. When observing so-called edge roll-off of the semiconductor wafer SW described later, it may be an annular portion in the outer periphery of the semiconductor wafer SW.

  As described above, when the surface shape Φ in the desired measurement range is obtained, the entire surface shape computation unit 73 of the computation control unit 7a performs the desired measurement based on the surface shape Φ obtained by the first surface shape computation unit 71. The entire surface shape of the measurement object SW in the range is obtained. For example, the total surface shape calculation unit 73 sequentially connects the surface shapes Φ (0), Φ (1),..., Φ (k) obtained as described above, thereby obtaining the desired measurement range. The total surface shape of the measuring object SW at is obtained.

  And the calculation control part 7a outputs the whole surface shape of the measurement object SW calculated in this way to the output part 8 (S18). Thereby, the entire surface shape of the measuring object SW is presented. The surface shape Φ obtained by the first surface shape calculation unit 71 may be output to the output unit 8.

  On the other hand, while the surface shape Φ of the measurement object SW is calculated, the coordinate position calculation unit 72 of the calculation control unit 7a is based on the surface image CP of the measurement object SW photographed by the photographing unit 5. To obtain the coordinate position of the measurement point MP. Since the arrangement position of the imaging unit 5 with respect to the surface of the measurement object SW, the magnification of the optical system of the imaging unit 5, and the like are known, the coordinate position calculation unit 72 recognizes the end of the measurement object SW, The coordinate position of the measurement point MP can be obtained using this end as a reference. Since the reflected light of the measurement light incident on the wavefront sensor 4 and the reflected light of the measurement light incident on the imaging unit 5 are the same, the coordinate position calculation unit 72 is used as a reference for the wavefront sensor 4. The position can be associated with the image of the measurement object SW photographed by the photographing unit 5, and the coordinate position of the reference position can be obtained at the measurement location MP from the coordinate position of the measurement location MP. And the coordinate position of the measurement location MP calculated | required in this way is also output to the output part 8, and is shown. The position of the measurement point MP can be obtained, for example, according to the amount of movement of the stage 9 on which the semiconductor wafer that is the measurement object SW is placed. In this way, the reflection of the measurement light incident on the wavefront sensor 4 is reflected. Since the coordinate position of the measurement location MP is obtained based on the surface image of the measurement object SW obtained by receiving a part of the light, the surface shape measuring device Sa having such a configuration is provided with the position of the measurement location MP. Can be recognized more accurately.

  Thus, since the surface shape measuring apparatus Sa in the first embodiment measures the surface shape of the semiconductor wafer SW that is the measurement object SW by using the wavefront sensor 4, the surface shape of the semiconductor wafer SW is measured based on the measurement principle. It is possible to measure the surface shape of the semiconductor wafer SW with a precision suitable for the above measurement and in a shorter time. For example, a Shack-Hartmann wavefront sensor can measure on the order of nanometers, and can measure a relatively large surface angle range of about several to tens of mrad, so that the semiconductor wafer SW can be measured in a shorter time. Can be measured.

  Next, another embodiment will be described.

(Second Embodiment)
FIG. 12 is a diagram illustrating a configuration of a surface shape measuring apparatus according to the second embodiment. FIG. 13 is a diagram illustrating a configuration of a thickness distribution measuring unit in the surface shape measuring apparatus according to the second embodiment. FIG. 14 is a diagram for explaining a method of obtaining the other surface shape based on the one surface shape and the thickness distribution in the surface shape measuring apparatus of the second embodiment.

  The surface shape measuring device Sa in the first embodiment is a device that measures the surface shape of one main surface of the semiconductor wafer SW that is the measurement object SW, but the surface shape measuring device Sb in the second embodiment is the one described above. In addition to the measurement of the surface shape of the main surface, the thickness distribution of the measurement object SW is measured, and the one main surface is opposed based on the measured surface shape and thickness distribution of the one main surface. It is an apparatus for obtaining the surface shape of the other main surface.

  The surface shape measuring device Sb in the second embodiment is a semiconductor that is a measurement object SW by using heterodyne interferometry to measure the thickness distribution in addition to the surface shape measuring device Sa in the first embodiment. A thickness distribution measuring unit for measuring the thickness distribution of the wafer SW is further provided, and the light source unit 1 is provided on one surface of the measuring object SW via the half mirror 2 in order to obtain the surface shape of the other main surface. Irradiating measurement light having a predetermined wavefront, the wavefront sensor 4 measures the shape of the wavefront in the reflected light of the measurement light reflected by one surface of the measurement object SW, and the first surface shape calculation unit 71 Based on the shape of the wavefront in the reflected light of the measurement light measured by the wavefront sensor 4, the surface shape on one surface of the measurement object SW is obtained and obtained by the first surface shape calculation unit 71. Second surface shape for obtaining a surface shape on the other surface of the measuring object SW based on the surface shape on one surface of the fixed object SW and the thickness distribution of the measuring object SW measured by the thickness distribution measuring unit. A calculation unit 76 is further provided.

  More specifically, as shown in FIG. 12, the surface shape measuring device Sb in the second embodiment includes a surface shape measuring unit S1, a thickness distribution measuring unit S2, and an arithmetic control unit 7b. The example shown in FIG. 12 further includes an input unit 6, an output unit 8, and a stage 9.

  The surface shape measuring unit S1 is controlled by the arithmetic control unit 7b, and when measuring light is irradiated onto the measuring object SW in order to measure one surface shape of the measuring object SW, the reflected wave of the measuring light is reflected. Is configured to include a light source unit 1, a half mirror 2 as an optical path changing unit 2, a half mirror 3 as an optical branching unit 3, a wavefront sensor 4, and an imaging unit 5. Yes. The light source unit 1, the half mirror 2, the half mirror 3, the wavefront sensor 4 and the imaging unit 5 in the surface shape measuring unit S1 are the light source unit 1, the half mirror 2, the half mirror 3 and the wavefront sensor in the surface shape measuring apparatus Sa in the first embodiment. 4 and the imaging unit 5, and thus the description thereof is omitted.

  The thickness distribution measurement unit S2 is controlled by the calculation control unit 7b, and the thickness distribution of the measurement object SW is changed to, for example, a nanometer level or a sub-nanometer level (thickness direction of 1 nm or less) by using the optical heterodyne interferometry. In other words, the measurement object SW is irradiated with measurement light for thickness distribution measurement (second measurement light) and the reflected light is measured. For example, as shown in FIG. 13A, the thickness distribution measuring unit S2 includes the light source unit 10, the one surface side measuring unit 11-1, the other surface side measuring unit 11-2, and the one surface side. The phase detector 12-1 and the other surface side phase detector 12-2 are configured to measure the thickness distribution of the measurement object SW while moving the measurement object SW in the horizontal direction by the stage 9. It is. Note that FIG. 12 shows the one-side measurement unit 11-1 and the other-side measurement unit 11-2 in the thickness distribution measurement unit S.

  Hereinafter, each part of the thickness distribution measurement unit S2 will be described. Here, optical components (optical elements) frequently used in each unit will be described together.

  An optical branching device (non-polarizing beam splitter) is an optical component that divides incident light into two lights in terms of optical power and emits them respectively. The optical branching unit uses, for example, a micro-optical element type optical branching coupler such as the above-mentioned half mirror (half mirror), an optical fiber type optical branching coupler of a molten fiber, an optical waveguide type optical branching coupler, or the like. Can do. In general, the optical branching unit functions as an optical coupling unit that emits two incident lights together when the input terminal and the output terminal are switched (reversely). When a half mirror is used as the light branching portion, usually, one of the distributed lights passes through the half mirror and is emitted in the same direction, and the other distributed light is reflected by the half mirror and is reflected in this direction. Injected in a vertical direction (orthogonal direction).

  A polarization beam splitter is an optical component that takes out S-polarized light and P-polarized light that are orthogonal to each other from incident light and emits them, and usually one of the extracted lights (S-polarized light or P-polarized light) The other light (P-polarized light or S-polarized light) is emitted in a direction (perpendicular to this direction) perpendicular to this direction.

  A polarizer is an optical component that extracts and emits linearly polarized light having a predetermined polarization plane from incident light, and is, for example, a polarization filter.

  A wave plate (phase plate) is an optical component that emits a predetermined phase difference (and thus an optical path difference) between two polarization components in incident light. A four-wave plate, a half-wave plate that gives an optical path difference of λ / 2 between two polarization components in incident light, etc. In a crystal plate that constitutes the wave plate, such as a birefringent muscovite plate When the thickness is d, the refractive indices for the two polarization components in the crystal plate are n1 and n2, respectively, and the wavelength of the incident light is λ, the phase difference due to this waveplate is (2π / λ) (n1 -N2) given by d.

  A reflection mirror is an optical component that changes the traveling direction of light by reflecting incident light with a predetermined reflectivity at a reflection angle corresponding to the incident angle. For example, the reflection mirror is applied to the surface of a glass member. A metal thin film or a dielectric multilayer film is deposited. The reflecting mirror is preferably a total reflecting mirror that totally reflects light in order to reduce light loss.

  The input terminal is a terminal for inputting light to the optical component, and the output terminal is a terminal for emitting light from the optical component. For the connection between the parts, a light guide means composed of optical components such as a mirror and a lens may be used. However, in this embodiment, the polarization holding is used for the connection between the parts as will be described later. Since optical fibers such as optical fibers and multimode optical fibers are used, connectors for connecting optical fibers are used for these input terminals and output terminals.

  Hereinafter, each part of the thickness distribution measurement unit S2 will be described. First, the light source unit 10 will be described. The light source unit 10 is a device that generates predetermined coherent light and generates second measurement light for measuring the thickness of the measurement object SW by optical heterodyne interferometry. The second measurement light is single-wavelength light having a predetermined wavelength λ0 (frequency ω0) set in advance, and is polarized light having a predetermined polarization plane set in advance. The second measurement light includes two one-surface-side measurement light (A-th measurement light) and another-surface-side measurement light (B-th measurement light) in order to measure the measurement object SW from both surfaces by optical heterodyne interferometry. Yes. Such a light source unit 10 includes, for example, a single wavelength laser light source 101, an optical isolator 102, an optical branching unit 103, polarizers 104 and 106, and output terminals 105 and 107, as shown in FIG. And is configured.

  The single-wavelength laser light source 101 is a device that generates a single-wavelength laser beam having a predetermined wavelength λ0 (frequency ω0) set in advance, and various laser devices can be used. A helium neon laser device (He-Ne laser device) that can output laser light having a wavelength of about 632.8 nm. The single wavelength laser light source 101 is preferably a frequency stabilized laser device provided with a wavelength locker or the like. The optical isolator 102 is an optical component that transmits light only in one direction from its input terminal to its output terminal. In the optical isolator 102, in order to stabilize the laser oscillation of the single-wavelength laser light source 101, the reflected light (return light) generated at the connection part of each optical component (optical element) in the thickness distribution measurement unit S2 is a single wavelength. This prevents the light from entering the laser light source 101.

  In such a light source unit 10, the laser light emitted from the single wavelength laser light source 101 enters the optical branching unit 103 via the optical isolator 102 and is distributed to the first laser beam and the second laser beam. The The first laser light is incident on the polarizer 104 and is emitted from the output terminal 105 as measurement light on one side of the laser light having a predetermined polarization plane. The one-surface measurement light is incident on the one-surface measurement unit 11-1. On the other hand, the second laser light is incident on the polarizer 106 and is emitted from the output terminal 107 as measurement light on the other side of the laser light having a predetermined polarization plane. This other side measurement light is incident on the other side measurement unit 11-2.

  Here, for convenience of explanation, one surface of the measurement object SW (upper surface (upper surface) in the example shown in FIG. 13) will be referred to as “A surface”, and the measurement object SW has the A surface and the front and back surfaces. The other surface (the lower surface (lower surface) in the example shown in FIG. 13) is referred to as “B surface”. In the present embodiment, the one-surface-side measurement light is used to measure the A-plane of the measurement object SW by optical heterodyne interferometry, and the other-surface-side measurement light is an optical heterodyne on the B-surface of the measurement object SW. Used to measure by interferometry.

  The optical path length between the light source unit 10 and the one-surface side measuring unit 11-1 is used for the connection between the light source unit 10 and the one-surface side measuring unit 11-1 and the connection between the light source unit 10 and the other-surface-side measuring unit 11-2. From the viewpoint of facilitating the adjustment with the optical path length between the light source unit 10 and the other surface side measurement unit 11-2, in the present embodiment, each of the polarization maintaining units guides light while maintaining its polarization plane. Optical fiber OF (OF-1, OF-2) is used. The polarization maintaining optical fiber is, for example, a PANDA fiber or an elliptical core optical fiber. The one-surface measurement light emitted from the output terminal 105 of the light source unit 10 is guided by the polarization maintaining optical fiber OF-1, enters the one-surface measurement unit 11-1, and exits from the output terminal 107 of the light source unit 10. The other-surface measurement light is guided by the polarization maintaining optical fiber OF-2 and enters the other-surface measurement unit 11-2.

  Next, although the one surface side measurement part 11-1 and the other side measurement part 11-2 are demonstrated, since these are the same structures, here, the one surface side measurement part 11-1 is demonstrated below, and the other The description of the side measurement unit 11-2 is omitted.

  The one-surface measurement unit (A measurement unit) 11-1 receives the one-surface measurement light from the light source unit 10, and beats on the A surface of the measurement object WA by optical heterodyne interferometry using the one-surface measurement light. An apparatus for obtaining an optical signal.

  More specifically, the one-surface-side measuring unit 11-1 is arranged to face the A-surface of the measurement object SW, and the one-surface-side measuring light (A-th measuring light) from the light source unit 10 is used as the first one-surface-side measuring light ( The first A1 measurement light) and the second one-surface measurement light (A2 measurement light) are further divided, and are irradiated onto the A surface of the measurement object SW in the divided first one-side measurement light by optical heterodyne interference. A post-irradiation one-side interference light (interfering light after the A-th irradiation) is generated by causing the reflected post-irradiation one-surface measurement light (post-A-irradiation measurement light) to interfere with the divided second one-surface measurement light. In addition, by the optical heterodyne interference, the divided one-side measurement light before irradiation (measurement light before the A-th irradiation) before being irradiated onto the A surface of the measurement object SW in the divided first one-side measurement light is divided. Pre-irradiation one-side interference light (the A-th irradiation) that interferes with the second one-side measurement light Interference light) is measured optical system for generating. In the other surface side measuring unit 11-1 having such a configuration, each phase in the one surface side interference light after irradiation can be measured on the basis of the one surface side interference light before irradiation.

  More specifically, the one-surface measurement unit 11-1 is disposed opposite to the surface A of the measurement object SW, and two first and second one-surface measurement lights having different frequencies from the one-surface measurement light. An optical heterodyne interferometer that generates a beat optical signal having a frequency of a difference between the first first-surface-side measurement light and the second first-surface-side measurement light (optical heterodyne interference). The first one-side measurement light is measured after the first and second one-side measurement light is generated from the one-side measurement light and before the first one-side measurement light and the second one-side measurement light interfere with each other. This is a measurement optical system including a first one-surface-side optical path that is irradiated and reflected on the A-plane of the object SW and a second one-surface-side optical path that is not irradiated to the A-plane of the measurement object SW.

  For example, as shown in FIG. 13B, the one-surface measurement unit 11-1 includes an input terminal 11a, optical branching units 11b, 11f, 11h, 11i, and 11m, a polarization beam splitter 11l, Wavelength shifters 11d and 11e, reflecting mirrors 11c and 11g, a quarter wavelength plate 11p, a lens 11g, polarizing plates 11j and 11n, and output terminals 11k and 11o are provided.

  In the one-surface measurement unit 11-1 having such a configuration, the one-surface measurement light incident on the input terminal 11a from the light source unit 10 via the polarization maintaining optical fiber OF-1 is incident on the optical branching unit 11b. The first one-side measuring light and the second one-side measuring light are distributed. The first one-surface-side measurement light travels in the same direction (in the light branching section 11b, the traveling direction of the incident light and the traveling direction of the emitted light are the same), while the second one-surface-side measuring light is the first one-surface side. The light travels in a direction (perpendicular direction) perpendicular to the traveling direction of the measurement light. The first one-side measurement light is incident on the optical wavelength shifter 11dc, the wavelength (frequency) is shifted (changed), and the second one-side measurement light is incident on the optical wavelength shifter 11e via the reflecting mirror 11c, The wavelength (frequency) is shifted (changed).

  In addition, the second one-side measurement light emitted from the light branching unit 11b travels in a direction orthogonal to the traveling direction of the first one-side measurement light by the light branching unit 11b in this embodiment, but is reflected by the reflecting mirror 11c. The traveling direction is bent at a right angle, and aligned with the traveling direction of the first one-side measuring light. Thus, the reflecting mirror 11c is provided to align the traveling direction of the first one-side measurement light emitted from the light branching portion 11b with the traveling direction of the second one-side measurement light.

  The first one-surface measurement light (the first one-surface measurement light after the wavelength shift) emitted from the wavelength shifter 11d is incident on the light branching unit 11h, and the eleventh one-surface measurement light (the A11 measurement light) and the twelfth light. It is distributed to two of the one-surface-side measurement light (A12th measurement light). The eleventh one-surface measurement light travels in the same direction, while the twelfth one-surface measurement light travels in a direction orthogonal to the traveling direction of the eleventh one-surface measurement light. In addition, the second one-surface measurement light (the first one-surface measurement light after the wavelength shift) emitted from the wavelength shifter 11e is incident on the optical branching unit 11f, and the twenty-first 21-surface measurement light (the A21 measurement light) and It is distributed to two of the 22nd one side measurement light (A22th measurement light). The twenty-first surface-side measuring light travels in the same direction, while the twenty-first surface-side measuring light travels in a direction orthogonal to the traveling direction of the twenty-first surface-side measuring light.

  The twelfth one-surface measurement light is the pre-irradiation one-surface measurement light and is incident on the light branching portion 11i, and the twenty-first surface-side measurement light is incident on the light branching portion 11i via the reflecting mirror 11g. The twelfth one-side measurement light and the twenty-first one-side measurement light incident on the light branching portion 11i are combined by the light branching portion 11i to cause optical heterodyne interference, and the beat light signal is converted into the polarizing plate 11j. Is emitted from the output terminal 11k as one-side interference light before irradiation. Here, the optical branching unit 11i functions as an optical coupling unit. The pre-irradiation one-side interference light of the beat light signal emitted from the output terminal 11k is incident on the one-side phase detector 12-1.

  The eleventh one-surface measurement light is incident on the quarter-wave plate 11p via the polarization beam splitter 11l, collected by the lens 11q, and irradiated onto the A surface of the measurement object SW. Then, the eleventh one-surface measurement light reflected by the A surface of the measurement object SW is again incident on the lens 11q as one-surface measurement light after irradiation, and then incident on the quarter-wave plate 11p. . Therefore, due to the presence of the quarter-wave plate 11p, the polarization state (for example, P-polarized light or S-polarized light) in the eleventh one-side measurement light irradiated from the polarization beam splitter 11l to the A surface of the measurement object SW, and the measurement object The polarization state (for example, S-polarized light or P-polarized light) in the eleventh one-side measurement light reflected by the A surface of the object SW and incident on the polarization beam splitter 11l is interchanged. Therefore, the eleventh one-surface measurement light incident on the polarization beam splitter 11l from the light branching unit 11h passes through the polarization beam splitter 11l toward the A surface of the measurement object SW, while the A surface of the measurement object SW. The eleventh one-side measurement light (post-irradiation one-side measurement light) incident on the polarization beam splitter 11l through the lens 11q and the quarter-wave plate 11p from a first lens 11q in a predetermined direction, in this embodiment, the eleventh one-side Measurement light (one-surface measurement light after irradiation) is reflected in a direction orthogonal to the direction from the A surface of the measurement object SW toward the polarization beam splitter 11l.

  The eleventh one-side measurement light (post-irradiation one-side measurement light) emitted from the polarization beam splitter 11l enters the light branching unit 11m. The 21st one-side measurement light distributed by the light branching part 11f is also incident on the light branching part 11m. The eleventh one-side measurement light (post-irradiation one-side measurement light) and the twenty-first one-side measurement light incident on the light branching portion 11f are combined in the light branching portion 11m to cause optical heterodyne interference. The beat light signal is emitted from the output terminal 11o as one-side interference light after irradiation through the polarizing plate 11n. Here, the optical branching part 11m functions as an optical coupling part. The one-side interference light after irradiation of the beat light signal emitted from the output terminal 11o is incident on the one-side phase detection unit 12-1.

  And the one surface side measurement part 11-1 and the other surface side measurement part 11-2 are front and back relation between the measurement location (measurement position) in the A surface of the measurement object SW and the measurement location (measurement position) in the B surface. Therefore, they are arranged so as to be in the same position. That is, when setting an orthogonal XYZ coordinate system in which the thickness direction of the measurement object SW is the Z-axis and the two orthogonal directions in the horizontal plane orthogonal to the thickness direction are the X-axis and the Y-axis, respectively, 11 The X coordinate value and the Y coordinate value of the portion where the one-surface measurement light is irradiated on the A surface of the measurement object SW are the X coordinate values of the portion where the eleventh other-surface measurement light is irradiated on the B surface of the measurement object SW. The face-to-face arrangement is made to coincide with the coordinate value and the Y coordinate value.

  Next, the one-side phase detection unit (A-th phase detection unit) 12-1 and the other-side phase detection unit (B-th phase detection unit) 12-2 will be described. The one-side phase detection unit 12-1 will be described below, and the description of the other-side phase detection unit 12-2 will be omitted.

  The one-surface-side phase detection unit 12-1 is a device for detecting each phase difference ΔΦ2 between the post-irradiation one-surface interference light and the pre-irradiation one-surface interference light obtained by the one-surface measurement unit 11-1. . More specifically, such a one-side phase detector 12-1 includes, for example, photoelectric converters 121 and 124, amplifiers 122 and 125, and a phase detector 126 as shown in FIG. And a shield plate 123.

  The photoelectric conversion unit 121 includes a photoelectric conversion element such as a photodiode, for example, and receives pre-irradiation one-side interference light from the one-side measurement unit 11-1 via a multimode optical fiber and an input terminal (not shown). Thus, an electrical signal having a signal level corresponding to the amount of light is output as a one-side reference beat signal (Ath reference beat signal) Ref1. The photoelectric conversion unit 124 includes a photoelectric conversion element such as a photodiode, for example, and receives post-irradiation one-side interference light from the one-side measurement unit 11-1 via a multimode optical fiber and an input terminal (not shown). Thus, an electric signal having a signal level corresponding to the amount of light is output as one-surface measurement beat signal (Ath measurement beat signal) Sig1.

  The amplifier 122 is a signal amplifying amplifier, amplifies the one-side reference beat signal Ref1 from the photoelectric conversion unit 121 with a predetermined gain, and outputs the amplified signal to the phase detector 126. The amplifier 1245 is an amplifier for signal amplification, amplifies the one-surface measurement beat signal Sig1 from the photoelectric conversion unit 124 with a predetermined gain, and outputs the amplified signal to the phase detector 126.

  The shield plate 123 is, for example, a metal plate disposed between a signal transmission path from the photoelectric conversion unit 121 to the phase detector 126 and a signal transmission path from the photoelectric conversion unit 124 to the phase detector 126. This is for reducing the influence of unnecessary radiation of electromagnetic waves generated in one signal transmission path on the other signal transmission path and preventing crosstalk between these signal transmission paths.

  The phase detector 126 is a device that detects the phase between input signals. The one-surface reference beat signal Ref1 is input from the photoelectric conversion unit 121 via the amplifier 122, and the one-surface side from the photoelectric conversion unit 124 via the amplifier 125. The measurement beat signal Sig1 is input, and the phase difference ΔΦ2 between the one-surface reference beat signal Ref1 and the one-surface measurement beat signal Sig1 is detected.

  Then, the single-side phase detection unit 12-1 outputs the detected phase difference ΔΦ2 to the calculation control unit 7b. Similarly, in the other surface side phase detection unit 12-2, the other surface side reference beat signal Ref2 is input from the photoelectric conversion unit 121 via the amplifier 122, and the other surface side measurement beat is transmitted from the photoelectric conversion unit 124 via the amplifier 125. The signal Sig2 is input, the phase difference ΔΦ1 between the other-surface-side reference beat signal Ref2 and the other-surface-side measured beat signal Sig2 is detected, and the other-surface-side phase detector 12-2 detects the detected phase difference. ΔΦ1 is output to the calculation control unit 7b.

  As described above, the surface shape measuring apparatus Sb in the second embodiment irradiates the second measuring light from both surfaces of the measuring object SW and measures the reflected light in order to measure the thickness of the measuring object SW. . For this reason, for example, as shown in FIG. 12, the stage 9 is not affected by the vibration of the measurement object SW, and the surface shape and thickness of the measurement point MP of the measurement object SW can be accurately and rapidly increased. In order to be able to measure, three arm members extending in the radial direction from the central member are provided, and a disc-shaped measurement object SW such as a semiconductor wafer SW is provided at the edge (edge region) at the tip of the arm member. 9d, a support portion 9d supporting three points on the circumference, a rotation shaft 9a connected to the central member of the support portion 9d, a rotation drive portion 9b for rotating the rotation shaft 9a, and a rotation drive portion 9b And a linear drive unit 9c that linearly moves within a predetermined movement range. The rotation drive unit 9b and the linear drive unit 9c are configured to include an actuator such as a servo motor and a drive mechanism such as a reduction gear.

  In the stage 9 having such a configuration, the measurement object SW is placed on the tips of the three arm members in the support portion 9d and supported by the support portion 9d at three points. When the measurement object SW is placed on the stage 9 as described above, the A surface and the B surface of the measurement object SW are measured by the one surface side measurement unit 11-1 and the other surface side measurement unit 11-2. The stage 9 is arranged with respect to the arrangement position of the one-surface side measurement unit 11-1 and the other-surface side measurement unit 11-2 so that the measurement can be performed.

  And in the stage 9 of such a structure, the rotation drive part 9b rotates according to control of the calculation control part 7b, the support part 9d rotates via the rotating shaft 9a, and the measuring object SW rotates to the rotating shaft 9a ( The support member 9d rotates around the center member). And the measuring object SW moves along a radial direction because the linear drive part 9c linearly moves the rotational drive part 9b according to control of the calculation control part 7b. By using such a rotational movement of the measurement object SW by the rotation drive unit 9b and a movement of the measurement object SW in the linear direction by the linear drive unit 9c, the measurement object SW is moved within the movement range of the stage 9. A desired measurement point MP can be measured.

  The arithmetic control unit 7b is a circuit that controls each part of the surface shape measuring device Sa according to the function, and uses the surface shape on one surface of the measurement object SW as the output of the wavefront sensor 4 in the wavefront shape measuring unit S1. The thickness distribution of the measurement object SW is obtained based on the output of the thickness distribution measuring unit S2, and the surface shape on the one surface of the measurement object SW and the thickness of the measurement object SW are obtained. The surface shape of the other surface of the measuring object SW is obtained based on the distribution. Similar to the calculation control unit 7a, the calculation control unit 7b is configured by, for example, a microcomputer and functionally includes a first surface shape calculation unit 71, a coordinate position calculation unit 72, and a total surface shape calculation unit 73. , A control unit 74b, a thickness distribution calculation unit 75, and a second surface shape calculation unit 76.

  The first surface shape calculation unit 71, the coordinate position calculation unit 72, and the total surface shape calculation unit 73 in the calculation control unit 7b are the first surface shape calculation unit in the calculation control unit 7a of the surface shape measurement apparatus Sa of the first embodiment. 71, since it is the same as the coordinate position calculation unit 72 and the entire surface shape calculation unit 73, description thereof is omitted.

  The thickness distribution calculation unit 75 is obtained by phase-detecting the pre-irradiation single-side interference light and post-irradiation single-side interference light generated by the single-surface side measurement unit 11-1 by the single-surface phase detection unit 12-1. Obtained by phase detection of the phase difference ΔΦ2 and the pre-irradiation other-side interference light and post-irradiation other-side interference light generated by the other-surface-side measurement unit 11-2 by the other-surface-side phase detection unit 12-2. Based on the difference (ΔΦ2−ΔΦ1) from the obtained phase difference ΔΦ1, the distance from the A surface to the B surface of the measurement object SW is obtained as the thickness of the measurement object WA. This difference (ΔΦ2−ΔΦ1) is a value related to the thickness of the measurement object SW, and is measured on the one side side under the approximation that the wavelength of the one side measurement light and the wavelength of the other side measurement light are equal. When the wavelength of light is λ, the thickness D of the measurement object SW is obtained by, for example, D = (ΔΦ1 + ΔΦ2) × (λ / 2) / (2π). The sign of the above formula (the sign between ΔΦ1 and ΔΦ2) can be positive or negative depending on the optical system. Usually, the one-side measuring unit 11-1 and the other-side measuring unit 11-2 are symmetrical. When made (configured), it is positive (+). In this embodiment, the second measurement light on the one surface side and the other surface side is obtained by branching light from the same light source, and the wavelength of the second measurement light on the one surface side and the other surface side is one. I'm doing it. Then, the one-surface phase detection unit 12-1 on the A side and the other-surface phase detection unit 12-2 on the B surface are synchronized and synchronized according to the control of the control unit 74b in the calculation control unit 7b (at the same timing). ) Perform the phase detection. Thereby, the difference (ΔΦ2−ΔΦ1) can measure the thickness of the measurement object SW without being affected by the vibration of the measurement object SW. Such a measurement of the thickness of the measurement object SW is performed for each measurement point MP of the measurement object SW, whereby the thickness distribution calculation unit 75 obtains the thickness distribution of the measurement object SW.

  As described above, the thickness distribution calculation unit 75, for each measurement point MP, the phase difference ΔΦ2 input from the one-side phase detection unit 12-1 and the phase difference Δ input from the other-side phase detection unit 12-2. Based on [Phi] 1, the thickness of the semiconductor wafer SW that is the measurement object SW is obtained, and the thickness distribution of the semiconductor wafer SW is obtained.

  The second surface shape calculation unit 76 is a semiconductor wafer SW measured by the surface shape and thickness distribution measurement unit 75 on one surface of the semiconductor wafer SW which is the measurement object SW obtained by the first surface shape calculation unit 71. The surface shape of the other surface of the semiconductor wafer SW is obtained on the basis of the thickness distribution. As shown in FIG. 14, the surface shape (the other surface shape h (r)) on the other surface of the semiconductor wafer SW is the thickness from the surface shape (the one surface shape g (r)) on the one surface of the semiconductor wafer SW. It is obtained by subtracting the distribution f (r). Therefore, more specifically, the second surface shape calculation unit 76 is obtained by the thickness distribution measurement unit 75 from the one surface shape g (r) of the semiconductor wafer SW obtained by the first surface shape calculation unit 71. The other surface shape h (r) of the semiconductor wafer SW is obtained by subtracting the thickness distribution f (r) of the semiconductor wafer SW. In addition, r is a coordinate value in the R coordinate set along a predetermined direction in the measurement object SW, for example, along the radial direction.

  The control unit 74b includes the light source unit 1, the wavefront sensor 4, the imaging unit 5, the stage 9, the light source unit 10, the one surface side measuring unit 11-1, the other surface side measuring unit 11-2, the one surface side phase detecting unit 12-1, and the like. Each of the other surface side phase detector 12-2 is controlled in accordance with the function of each part.

  In the example shown in FIG. 12, the one-side phase detection unit 12-1 or the other-side phase detection unit 12-2 in the surface shape measurement unit S <b> 1 and the thickness distribution measurement unit S <b> 2 is a surface shape measurement unit. S1 and the one-surface phase detection unit 12-1 on the thickness distribution measurement unit S2 are spaced apart from each other so that the semiconductor wafer SW that is the measurement target SW can be individually measured. It arrange | positions on the same side, for example, A surface side.

  In the surface shape measuring apparatus Sb having such a configuration, when a power switch (not shown) is turned on, the surface shape measuring apparatus Sb is activated, and necessary parts are initialized by the arithmetic control unit 7b. Then, for example, when the measurement object SW of a plate-like body such as a semiconductor wafer is placed on the stage 9 and receives a command instructing measurement start from the input unit 6, the arithmetic control unit 7b reads the surface shape of the measurement object SW. Start measuring. That is, in the measurement of the one surface shape g (r) of the measurement object SW, the measurement object operates in the same manner as the surface shape measurement device Sa in the first embodiment, and is measured by the first surface shape calculation unit 71 of the calculation control unit 7b. One surface shape g (r) of SW is obtained. In the measurement of the thickness distribution of the measurement object SW, the second measurement light is guided from the light source unit 10 to the one surface side measurement unit 11-1, the A surface side is measured by the one surface side measurement unit 11-1, and the one surface is measured. The phase difference ΔΦ2 is detected by the side phase detector 12-1, the phase difference ΔΦ2 is output to the calculation controller 7b, and the second measurement light from the light source unit 10 is sent to the other surface side measurement unit 11-2. The second surface side measurement unit 11-2 measures the B surface side, the other surface side phase detection unit 12-2 detects the phase difference ΔΦ1, and the phase difference ΔΦ1 is input to the arithmetic control unit 7b. Is output. Then, the thickness distribution calculation unit 75 obtains the thickness of the measurement object SW from these phase differences ΔΦ1 and ΔΦ2. And the thickness distribution calculating part 75 calculates | requires thickness distribution f (r) of the measurement object SW by changing the measurement location MP sequentially by the stage 9. FIG.

  When the one surface shape g (r) of the measurement object SW and the thickness distribution f (r) thereof are obtained, the second surface shape calculation unit 76 calculates the semiconductor wafer SW obtained by the first surface shape calculation unit 71. On the other hand, the other surface shape h (r) of the semiconductor wafer SW is obtained by subtracting the thickness distribution f (r) of the semiconductor wafer SW obtained by the thickness distribution measuring unit 75 from the surface shape g (r). Data synchronization (corresponding to each other) between the one surface shape g (r) of the measurement object SW and its thickness distribution f (r) is performed by the surface shape measurement unit S1 and the one-side measurement unit 11-1. Or it can carry out based on the relationship of the arrangement | positioning position between the other side measurement parts 11-2. Then, the one surface shape g (r), the other surface shape h (r) and the thickness distribution f (r) of the obtained measurement object SW are output to the output unit 8 and presented.

  Thus, the surface shape measuring apparatus Sb in the second embodiment can measure each surface shape on both the front and back surfaces of the semiconductor wafer, and can also measure the thickness distribution.

  In the above description, the one surface shape g (r) and the thickness distribution f (r) of the measurement object SW are performed by one stage 9, but each stage is provided separately and performed by a separate stage. May be. A transport mechanism for transporting the measurement object SW from one stage to the other stage is provided, and the measurement object SW is moved between the stages. In this case, in order to synchronize data between the one surface shape g (r) of the measurement object SW and its thickness distribution f (r), for example, the first measurement points MP are matched.

  Next, another embodiment will be described.

(Third embodiment)
FIG. 15 is a diagram illustrating a configuration of a semiconductor wafer inspection apparatus according to the third embodiment. FIG. 16 is a diagram for explaining edge roll-off. FIG. 16A is a schematic diagram showing a surface profile of a wafer, and FIG. 16B is a schematic vertical sectional view of the wafer. In FIG. 16A, the horizontal axis represents the distance from the edge of the wafer, and the vertical axis represents the height.

  The semiconductor wafer inspection apparatus Sc in the third embodiment includes the surface shape measuring apparatuses Sa and Sb according to the first or second embodiment, and inspects whether or not the surface shape of the semiconductor wafer SW satisfies a predetermined condition. It is. In such a semiconductor wafer inspection apparatus Sc, since any one of the above-described surface shape measuring apparatuses Sa and Sb of the first and second embodiments is used, the semiconductor wafer inspection apparatus Sc has an accuracy suitable for measuring the surface shape of the semiconductor wafer SW. And the surface shape of the semiconductor wafer SW can be measured in a shorter time. For this reason, such a semiconductor wafer inspection apparatus Sc can inspect the quality of the semiconductor wafer SW more speedily and more accurately. Therefore, such a semiconductor wafer inspection apparatus Sc can be suitably used for a product production line using the semiconductor wafer SW, for example. More specifically, the semiconductor wafer inspection apparatus Sc is disposed in the production line, for example, inspects the semiconductor wafer SW during the manufacture of the product, and the surface shape of the semiconductor wafer SW does not satisfy a predetermined condition. In order to remove the semiconductor wafer SW from the production line, the fact that the surface shape of the semiconductor wafer SW does not satisfy a predetermined condition is output. In such a semiconductor wafer inspection apparatus Sc, the yield of products is improved by selecting semiconductor wafers SW that do not reach the required specifications in the manufacturing process, and as a result, cost reduction can also be achieved. it can.

  Such a semiconductor wafer inspection apparatus Sc includes a surface shape measuring unit that measures the surface shape on the surface of the semiconductor wafer SW that is a measurement target, and whether the surface shape measured by the surface shape measuring unit satisfies a predetermined condition. A determination unit that determines whether or not and an output unit that outputs a determination result by the determination unit, wherein the surface shape measurement unit is one of the surface shape measurement devices Sa and Sb of the first and second embodiments. . FIG. 15 shows a semiconductor wafer inspection apparatus Sc when the surface shape measuring device Sa of the first embodiment is used for the surface shape measuring unit. That is, the semiconductor wafer inspection apparatus Sc shown in FIG. 15 includes a light source unit 1, an optical path changing unit 2, an optical branching unit 3, a wavefront sensor 4, an imaging unit 5, an input unit 6, and an arithmetic control unit 7a. , An output unit 8, a stage 9, and a determination unit 21. The surface shape measuring apparatus according to the first embodiment includes the light source unit 1, the optical path changing unit 2, the optical branching unit 3, the wavefront sensor 4, the imaging unit 5, the input unit 6, the calculation control unit 7a, the output unit 8, and the stage 9. Sa is configured, and each of these units includes the light source unit 1, the optical path changing unit 2, the light branching unit 3, the wavefront sensor 4, the imaging unit 5, the input unit 6, and the arithmetic control in the surface shape measuring apparatus Sa of the first embodiment described above. This is the same as the unit 7a, the output unit 8, and the stage 9.

  The determination unit 21 is connected to the calculation control unit 7a and determines whether the surface shape of the semiconductor wafer SW obtained by the calculation control unit 7a satisfies a predetermined condition. The determination unit 21 includes, for example, a microcomputer as in the arithmetic control unit 7a, and is functionally realized by this microcomputer. Then, the determination result of the determination unit 21 is output to the output unit 8.

  The predetermined condition may be set as appropriate according to the product manufactured by the semiconductor wafer SW, and may be, for example, the flatness of the semiconductor wafer SW or may be an index representing edge roll-off. .

  As shown in FIG. 16, the semiconductor wafer has a chamfered portion called “Chamfer” on the outermost side. For example, in a 300 mm wafer, an area of about 0.3 mm to 0.5 mm from the physical tip is the chamfered portion. It hits. Edge roll-off is an area extending from the chamfered portion to several mm inside. This edge roll-off is caused by various factors, and the major factor is in the polishing process of the semiconductor wafer. This edge roll-off usually exhibits a “sag shape” as shown in FIG. 16, but depending on conditions, it may exhibit a “swell shape” instead of a sag.

  As an evaluation method of this edge roll-off, for example, there is an evaluation value called ROA (Roll-off Amount; ROA) proposed by Kimura et al. As shown in FIG. 16A, this evaluation value is based on the shape of the semiconductor wafer at a position (reference area) of about 3 to 6 mm from the physical front end of the semiconductor wafer, which is considered to be flat. A plane is obtained and defined as the distance between the shape of the semiconductor wafer at a position of 1 mm and the reference plane. This evaluation value ROA is an index representing how much the outer edge of the semiconductor wafer is sagging or rising. When obtaining the evaluation value ROA which is an index of such edge roll-off, the determination unit 21 obtains the surface shape of the semiconductor wafer SW along the radial direction from the arithmetic control unit 7a to obtain the evaluation value ROA. The obtained evaluation value ROA is compared with an evaluation value ROA (reference ROA) as a predetermined condition, and it is determined whether or not the surface shape of the semiconductor wafer SW satisfies a predetermined condition.

  In the above description, the semiconductor wafer inspection apparatus Sc in the case where the surface shape measuring device Sa of the first embodiment is used for the surface shape measuring unit has been described with reference to FIG. The same applies to the semiconductor wafer inspection apparatus when the surface shape measuring apparatus Sb is used.

  In order to express the present invention, the present invention has been properly and fully described through the embodiments with reference to the drawings. However, those skilled in the art can easily change and / or improve the above-described embodiments. It should be recognized that this is possible. Therefore, unless the modifications or improvements implemented by those skilled in the art are at a level that departs from the scope of the claims recited in the claims, the modifications or improvements are not covered by the claims. To be construed as inclusive.

Sa, Sb Surface shape measuring device Sc Semiconductor wafer inspection device 1, 10 Light source unit 4 Wavefront sensor 5 Imaging unit 7a, 7b Calculation control unit 41 Micro lens array 42 Imaging element 43 Wavefront sensor calculation control unit 71 First surface shape calculation unit 72 Coordinate position calculation unit 75 Thickness distribution calculation unit 76 Second surface shape calculation unit

Claims (5)

A light irradiation unit that irradiates a surface of a semiconductor wafer to be measured with a plane wave measurement light having a plane wavefront whose normal is a traveling direction ;
A Shack-Hartmann type wavefront sensor that measures the shape of the wavefront in the reflected light of the measurement light reflected from the surface of the semiconductor wafer;
A surface shape calculation unit that obtains the shape of the surface of the semiconductor wafer based on the shape of the wavefront in the reflected light measured by the wavefront sensor;
The Shack-Hartmann wavefront sensor is
A lens array that receives the reflected light and includes a plurality of lenses arranged in an array ;
An imaging unit that captures an image of the reflected light that has passed through a plurality of lenses in the lens array ;
A data extraction processing unit that extracts data of a predetermined threshold value or more from the image data captured by the imaging unit ;
A wavefront calculation unit for obtaining a wavefront shape in the reflected light based on the data extracted by the data extraction processing unit ,
Wherein the predetermined threshold in the data extraction processing unit, the surface shape measuring apparatus, wherein the value der Rukoto corresponding to the distance from the edge of the semiconductor wafer. A branching part for branching the reflected light into a plurality of parts and allowing one of the plurality of branched lights to enter the wavefront sensor;
An imaging unit that images the surface of the semiconductor wafer so as to include at least an end portion of the semiconductor wafer by receiving another one of the plurality of branched lights,
The surface shape measuring apparatus according to claim 1, further comprising a coordinate position calculation unit that obtains a coordinate position of a measurement location based on a surface image of the semiconductor wafer imaged by the imaging unit. Surface-profile measuring instrument according to claim 1 or claim 2, further comprising a thickness profile measurement unit for measuring the thickness distribution of the semiconductor wafer by using the heterodyne interference method. The light irradiation unit irradiates measurement light having a predetermined wavefront on one surface of the semiconductor wafer,
The wavefront sensor measures the shape of the wavefront in the reflected light of the measurement light reflected from one surface of the semiconductor wafer,
The surface shape calculation unit obtains a surface shape on one surface of the semiconductor wafer based on the shape of the wavefront in the reflected light measured by the wavefront sensor,
The surface shape on the other surface of the semiconductor wafer based on the surface shape on the one surface of the semiconductor wafer obtained by the surface shape calculating unit and the thickness distribution of the semiconductor wafer measured by the thickness distribution measuring unit The surface shape measuring device according to claim 3 , further comprising a second surface shape calculating unit for obtaining A surface shape measuring unit for measuring the surface shape of the surface of the semiconductor wafer to be measured;
A determination unit that determines whether the surface shape measured by the surface shape measurement unit satisfies a predetermined condition; and
An output unit that outputs a determination result by the determination unit,
The surface shape measuring section, a semiconductor wafer inspection apparatus which is a surface shape measuring apparatus according to any one of claims 1 to 4.