JP4897573B2 - Shape measuring device and shape measuring method - Google Patents

Description

  The present invention relates to a shape measuring apparatus and method for measuring the shape of an end face of a thin sample such as a semiconductor wafer, an aluminum substrate for a hard disk, or a glass substrate.

When manufacturing a semiconductor wafer (hereinafter referred to as a wafer) or manufacturing a device using a wafer, the edge (edge) of the wafer may be damaged or chipped due to contact with other components or a wafer holding member. There is a case. In addition, the wafer may break due to the scratches and chips. It is considered that the ease of occurrence of scratches and chips at the edge of the wafer is related to the shape of the wafer end face (so-called edge profile portion). For this reason, it is important to correctly measure the edge profile of a thin sample (plate-like sample) represented by a wafer. The shape of the end face here is a profile in the thickness direction (one-dimensional direction) of the wafer, that is, the shape of the cross section in the thickness direction, and is hereinafter referred to as an edge profile.
On the other hand, in Non-Patent Document 1, light is irradiated from one side sandwiching the edge of the wafer, a projected image of the wafer is captured by a camera disposed on the other side, and the shape (contour) of the image obtained thereby. ) Shows a technique for measuring the edge profile of a wafer.
Patent Document 1 discloses a telecentric lens that irradiates light toward the surface (mirror surface) of the sample while changing the tilt of the sample and reflects only the reflected light that is reflected coaxially with the irradiation direction. A surface inspection apparatus for measuring the angular distribution of the sample surface, that is, the shape of the sample surface from the obtained image is shown.
JP-A-10-267636 "Wafer Edge / Notch Shape Measuring Device", Electronic Materials, August 1997

However, in the shape measurement of the projection method as shown in Non-Patent Document 1, a shape in which the measurement portion of the edge profile is recessed from the front and back portions in the projection direction (light irradiation direction) (hereinafter referred to as a recessed shape). If it has, there is a problem that the edge profile cannot be measured. For example, a semi-circular cutout called an notch (an example of the depression shape) for indicating the crystal direction of the wafer is formed on the wafer. In the projection type shape measurement disclosed in Non-Patent Document 1, , The edge profile of the notch cannot be measured.
Further, as shown in Patent Document 1, the measurement of detecting reflected light that is reflected in the coaxial direction with the light irradiation direction while changing the tilt of the sample is performed by a distribution of minute surface angles due to slight irregularities on the sample surface. It is applied to the measurement of When the measurement technique disclosed in Patent Document 1 is applied to the measurement of an edge profile, it is necessary to change the inclination of the sample every time light is irradiated to a plurality of measurement points whose surface angles are desired to be obtained. For this reason, applying the measurement technique disclosed in Patent Document 1 to the measurement of an edge profile that measures a shape whose surface angle changes by approximately 180 ° has a hindrance factor such as a complicated support mechanism for the sample. Therefore, there was a problem that it was practically difficult.
Accordingly, the present invention has been made in view of the above circumstances, and its object is to provide a shape measuring apparatus suitable for measuring an edge profile (shape of a cross section in the thickness direction of an end face) of a thin sample such as a semiconductor wafer, and the like. It is to provide such a method.

In order to achieve the above object, a shape measuring apparatus according to the present invention (corresponding to a second invention to be described later) is an apparatus for measuring the shape of an end face of a thin sample such as a semiconductor wafer, for example. It comprises each component shown in (1-6).
(1-1) By turning on a light source at each of a plurality of positions in one plane, light is sequentially emitted at different irradiation angles with respect to a measurement site including the end surface of the thin sample and the surfaces on both sides in the thickness direction in the vicinity thereof. First light irradiation means for irradiation.
(1-2) One-dimensional or two-dimensional luminance of light reflected in the substantially regular reflection direction from the measurement site, which is arranged in different directions with respect to the measurement site and is irradiated with light from the first light irradiation unit. A plurality of light detecting means for detecting the distribution.
(1-3) Reflected light brightness acquisition means for acquiring the brightness distribution of reflected light from the measurement site through the light detection means each time light is sequentially irradiated at different irradiation angles by the first light irradiation means.
(1-4) For each of the plurality of reflected light luminance distributions acquired by each of the plurality of reflected light luminance acquisition units, the luminance distribution of the reflected light and the irradiation of the light irradiated by the first light irradiation unit Surface angle distribution calculating means for calculating the distribution of the surface angle of a partial region of the measurement site based on the angle.
(1-5) Thickness measuring means for measuring the thickness of the thin sample for the portions on both sides in the thickness direction in the measurement site.
(1-6) The surface shape of each of said partial region based on the operation result of the distribution of the surface angle of the partial region by the surface angle distribution calculating means, the relative position thereof in the thickness direction of the thin sample measured by executing the results based on the adjusted and joining process, joining calculation means for calculating a front surface shape of the entire measurement region of the thickness measuring means.
For example, it is conceivable that the plurality of light detection means are two light detection means arranged in a direction of about 90 ° with the measurement site as a base point.

By using the shape measuring apparatus according to the present invention having the above-described configuration, it is possible to measure the surface angle distribution of a thin sample such as a semiconductor wafer, and based on the surface angle distribution, the edge profile (the shape of the cross section in the thickness direction of the end face) Can be measured correctly. Also, the edge profile can be measured for an end surface having the above-described depression shape such as a notch portion of a semiconductor wafer.
That is, in the shape measuring apparatus according to the present invention, the luminance distribution of the reflected light acquired by the reflected light luminance acquisition means is the luminance of the portion where the irradiated light is regularly reflected on the end face of the thin sample and reaches the light detection means. Is the highest. For this reason, the surface angle distribution calculating means can determine the distribution of the surface angle of the measurement site based on the regular reflection characteristic that the incident angle and the reflection angle of light are equal. Details thereof will be described later.
It should be noted that the lighting position of the light source in the first light irradiating means and the arrangement position of the light detecting means may be located in substantially the same plane, or may be located in different planes.

By the way, when a CCD camera or the like is used as the light detection means, the light detection range by one light detection means is limited. This limitation leads to a limitation on the maximum range of surface angles that can be measured in edge profile measurements.
On the other hand, the shape measuring apparatus according to the present invention calculates the distribution of the surface angle of a partial area of the measurement site for each luminance distribution of the reflected light obtained through each of the plurality of light detection means, The distribution of the surface angle of the entire measurement site is calculated by connecting the surface angle distribution or the surface shapes of the partial areas based on the distribution. For this reason, the maximum range of the surface angle that can be measured in the edge profile measurement can be expanded beyond the limit of the light detection range by one light detection means. Moreover, during the joining process, the surface angle distribution or the surface shape of the partial region based thereon is joined by adjusting the relative position in the thickness direction of the thin sample based on the thickness measurement result. Therefore, the surface shape of the entire measurement site can be measured with high accuracy.

When the front and back surfaces of the thin sample irradiated with light are imaged, the position of the light irradiation part (the position of the high brightness portion) in the obtained image is the distance between the imaging means (camera) and the surface of the thin sample. The distance between the imaging means and the thin sample surface can be easily calculated by triangulation processing based on the position of the light irradiation part.
Therefore, when the light detection means includes two image pickup means for picking up two-dimensional images of the surfaces on both sides in the thickness direction of the measurement site, the thickness measurement means includes the following (1-7) and It is conceivable to include the constituent elements shown in (1-8).
(1-7) Second light irradiating means for irradiating light to both surfaces in the thickness direction on the measurement site.
(1-8) Images of each surface on both sides in the thickness direction in the measurement site irradiated with light by the second light irradiation unit are acquired through the two imaging units, and light irradiation is performed based on the acquired images. Thickness calculating means for calculating the thickness of the thin sample by detecting the position.
The surfaces on both sides in the thickness direction of the measurement site are part of the front and back surfaces of the thin sample (for example, flat portions in the vicinity of the edge profile portion of the semiconductor wafer; hereinafter referred to as edges).
Thus, the two imaging means for shape measurement (an example of the light detection means) can be used for thickness measurement, and the thickness of the thin sample can be easily measured with a simple configuration.

By the way, if the change width (change width) of the light irradiation angle by the light irradiation means is made extremely small, a high space can be obtained by obtaining the position where the brightness of the reflected light becomes highest every time the light irradiation angle is changed. The distribution of the surface angle of the measurement site can be calculated with resolution. However, there is a limit to reducing the change width of the light irradiation angle. Further, as the change width of the light irradiation angle is reduced, the number of times the brightness distribution of the reflected light is collected increases and the measurement time becomes longer. Furthermore, the number of data points to be acquired by the reflected light luminance acquisition means increases, leading to an increase in required memory capacity.
Therefore, in the shape measuring apparatus, the surface angle distribution calculating means has the light irradiation angle and the brightness of the reflected light for each of a plurality of positions (hereinafter referred to as calculation target positions) in the light detection range of the light detecting means. It is preferable that the surface angle of each of the calculation target positions is calculated by performing an operation of estimating the irradiation angle of the light when the luminance of the reflected light reaches a peak based on the correspondence relationship with . Here, the estimated value of the irradiation angle of the light when the luminance of the reflected light reaches a peak is obtained by, for example, an interpolation calculation process based on a correspondence relationship between the irradiation angle of the light and the luminance of the reflected light. be able to.
Thereby, even if the change width of the light irradiation angle is relatively large, the distribution of the surface angle of the measurement site can be calculated with high spatial resolution.

Further, as the first light irradiating means, for example, a plurality of light sources arranged at a plurality of positions in one plane are sequentially switched and turned on so that the measurement sites are sequentially irradiated at different irradiation angles. It can be considered that it is a switchable light irradiation means for irradiating light. When this switchable light irradiating means is employed, a plurality of light sources may be arranged on an arc centering on the arrangement position of the measurement site. According to this configuration, it is possible to realize a simple and high position accuracy device without a movable mechanism.
Further, it is conceivable that the switching type light irradiating means simultaneously turns on a plurality of light sources corresponding to each of the plurality of light detecting means in the process of switching on and turning on a plurality of light sources.
Thereby, the measurement time can be shortened.
The first light irradiating means moves the predetermined light source sequentially to each of a plurality of positions in one plane so as to illuminate, so that the measurement site is irradiated with light at different irradiation angles. It can also be considered to be a mold light irradiation means. According to this configuration, the number of light sources can be reduced.
In addition, as will be described later, when the thin sample is a thin plate-like semiconductor wafer, the thickness measuring means is arranged from a boundary position with an edge profile portion (a chamfered end face (side face)) on both the front and back sides of the semiconductor wafer. It is desirable to measure the thickness of the semiconductor wafer in a range up to 5 mm inside, particularly in a position about 1 mm inside from the boundary position.

Further, the present invention (corresponding to a second invention described later) can also be regarded as a measuring method using the shape measuring apparatus described above.
That is, the shape measuring method according to the present invention is a method for measuring the shape of the end face of a thin piece sample, and executes the following steps (2-1) to (2-6).
(2-1) The first light irradiating means for turning on the light source at each of a plurality of positions in one plane sequentially changes with respect to the measurement site including the end face of the thin sample and the surfaces on both sides in the thickness direction in the vicinity thereof. A first light irradiation step of irradiating light at an irradiation angle.
(2-2) One-dimensional reflected light in a substantially regular reflection direction from the measurement site by light irradiation in the first light irradiation step by the light detection means arranged in different directions with respect to the measurement site. Alternatively, a light detection process for detecting a two-dimensional luminance distribution.
(2-3) Reflected light luminance acquisition step of acquiring the luminance distribution of the reflected light from the measurement site by executing the light detection step each time light is sequentially irradiated at different irradiation angles in the first light irradiation step. .
(2-4) For each of the plurality of reflected light luminance distributions acquired in the reflected light luminance acquisition step, based on the luminance distribution of the reflected light and the irradiation angle of the light irradiated in the first light irradiation step. A surface angle distribution calculating step of calculating a surface angle distribution of a partial region of the measurement site.
(2-5) A thickness measuring step of measuring the thickness of the thin piece sample with respect to portions on both sides in the thickness direction in the measurement site by a predetermined thickness measuring means.
(2-6) by a predetermined calculation means, the surface shape of each of said partial region based on the operation result of the distribution of the surface angle of the area of the surface angle distribution portion wherein by calculating step, the thickness of the thin sample by executing the process of joining by adjusting on the basis of the measurement result of their relative positions the thickness measuring step in the direction joining calculating step of calculating a front surface shape of the entire measurement site.

In the case where the light detection means includes two image pickup means for picking up two-dimensional images of the surfaces on both sides in the thickness direction in the measurement site, the following (2-7) and It is more preferable to execute each step shown in (2-8).
(2-7) A second light irradiating step of irradiating the surfaces on both sides in the thickness direction of the measurement site with light by a predetermined second light irradiating means.
(2-8) Images of each surface on both sides in the thickness direction in the measurement site irradiated with light in the second light irradiation step are acquired through the two imaging units, and light irradiation is performed based on the acquired images. A thickness calculating step of executing processing for calculating the thickness of the thin sample by detecting a position by a predetermined calculating means.
According to the shape measuring method for executing the steps described above, the same effects as those of the shape measuring apparatus according to the present invention can be obtained.

  According to the present invention (corresponding to a second invention described later), the edge profile of a thin sample such as a semiconductor wafer can be measured correctly (with high accuracy). Also, the edge profile can be measured for an end surface having the above-described depression shape such as a notch portion of a semiconductor wafer. Further, by having a means or process for measuring the shape of the end face of the thin piece sample by the light cutting method, the shape can be measured at any measurement site (end face) of the glossy surface or the rough surface.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings so that the present invention can be understood. The following embodiment is an example embodying the present invention, and does not limit the technical scope of the present invention.
FIG. 1 is a schematic configuration diagram of the shape measuring apparatus Z1 according to the embodiment of the first invention, FIG. 2 is a diagram showing definitions of the light irradiation angle and the surface angle, and FIG. 3 is a telecentric that can be employed in the shape measuring apparatus Z1. FIG. 4 is a diagram showing the characteristics of a lens-type camera. FIG. 4 is a diagram schematically showing the relationship between the surface angle of the measurement site and the optical path when a telecentric lens-type camera is adopted as the shape measuring device Z1, and FIG. 6 is a graph showing the surface angle distribution and edge profile of the measurement site calculated by the measuring device Z1, FIG. 6 is a diagram showing the characteristics of a non-telecentric lens type camera that can be employed in the shape measuring device Z1, and FIG. 7 is the shape measuring device Z1. Fig. 8 is a diagram schematically showing the relationship between the surface angle of the measurement site and the optical path when a non-telecentric lens type camera is used. Fig. 8 shows the shape and shape measurement of the measurement site. FIG. 9 is a diagram schematically illustrating a first example of an image captured by the camera of the apparatus Z1, FIG. 9 is a diagram schematically illustrating a second example of an image captured by the camera of the shape measurement apparatus Z1 and the shape of the measurement site. Is a diagram showing an example of a photographed image by the shape measuring device Z1, FIG. 11 is a graph showing an example of a correspondence relationship between the light irradiation angle and the reflected light luminance at a predetermined calculation target position, and FIG. 12 is a measurement procedure by the shape measuring device Z1. FIG. 13 is a diagram showing a schematic configuration of the shape measuring device Z2 according to the embodiment of the second invention, FIG. 14 is a conceptual diagram showing the principle of thickness measurement in the shape measuring device Z2, and FIG. 15 is a shape measuring device Z2. FIG. 16 is a diagram showing the surface angle distribution and the state before and after the fitting processing of the edge profile corresponding to each of the two cameras obtained by FIG. Diagram illustrating a schematic configuration of Z2 ', FIG. 17 is a sectional view showing a preferred location in the thickness measurements in the semiconductor wafer that is the subject of the shape measurement.

[First invention]
First, the configuration of the shape measuring apparatus Z1 according to the embodiment of the first invention will be described with reference to FIG. The shape measuring device Z1 is a device that measures the shape (edge profile) of an end surface (so-called edge profile portion) of a semiconductor wafer 1 (hereinafter referred to as a wafer) which is an example of a thin sample. Although the wafer 1 shown in the present embodiment has a substantially circular plate shape, a thin sample having another shape such as a rectangular plate shape can be used as a measurement target. 1A is a plan view (partially block diagram) of the shape measuring device Z1, and FIG. 1B is a side view (partially omitted) of the shape measuring device Z1.
Hereinafter, the region including the end surface of the wafer 1 to be measured for the edge profile and the vicinity thereof (the edge portions of the front and back surfaces of the wafer 1) is referred to as a measurement site P. The measurement site P includes a part (edge) of each of the front and back surfaces of the wafer 1 that are substantially parallel.
As shown in FIG. 1, the shape measuring device Z1 includes a light irradiation device 10, a camera 20, and a computer 30 such as a personal computer.
The light irradiation device 10 is configured as an electronic circuit board, and a plurality of LEDs 12 that are light sources for irradiating the wafer 1 with light and an LED drive circuit 11 that switches blinking of each of the LEDs 12 are mounted on the electronic circuit board. ing. In FIG. 1B, the description of some of the LEDs 12 is omitted.
Here, a predetermined position in a substantially central portion when the light irradiation device 10 (electronic circuit board) is viewed in plan is referred to as a reference position Q.

A cutout portion 13 into which the wafer 1 is inserted is formed on the electronic circuit board constituting the light irradiation device 10 so that the measurement site P of the wafer 1 can be arranged at the reference position Q. That is, the reference position Q is the arrangement position of the measurement site P. FIG. 1B shows an example in which the notch portion (semicircular cutout portion) of the wafer 1 is arranged as the measurement site P at the reference position Q, but this is not restrictive. Further, the measurement site P can be easily changed by rotating the wafer 1. Thereby, the edge profile of the whole circumference | surroundings of the wafer 1 or several places in the whole circumference | surroundings can be measured easily.
Further, all the LEDs 12 are arranged so that their light emitting portions are located in one plane including the reference position Q and on an arc centered on the reference position Q (along the arc). It is mounted on an electronic circuit board. Here, the LEDs 12 are arranged at regular intervals (equal angular intervals) so that the directions viewed from the reference position Q are different by about 2 °, for example, except for the position where they interfere with the camera 20. In addition, the distance from the reference position Q (measurement site P) of each LED 12 is a sufficiently long distance (for example, about 150 mm) with respect to the depth dimension of the measurement site P.
Further, the surface of the wafer 1 (the front surface and the back surface) is substantially orthogonal to one plane on which the light emitting portion of the LED 12 is arranged, and the center portion (the center of the disk) of the surface is The LED 12 is inserted into the notch 13 in a state where the light emitting part of the LED 12 is disposed, and measurement is performed in that state.
In accordance with a control command from the computer 30, the LED drive circuit 11 sequentially switches and blinks the plurality of LEDs 12 arranged at each of a plurality of positions in one plane. Thereby, the light irradiation apparatus 10 sequentially irradiates the measurement site P of the wafer 1 arranged at the reference position Q with light at different irradiation angles (an example of the first light irradiation unit and the switching type light irradiation unit). .
The end surface (side surface) which is the measurement site P of the wafer 1 is processed smoothly and has a mirror surface or a glossy surface close to it. For this reason, the light output from the LED 12 is almost regularly reflected at the measurement site P, and hardly diffusely reflected.

The camera 20 (the same applies to two cameras 20R and 20L described later) is fixed at a position (for example, about 50 mm to 100 mm) spaced from the reference position Q and receives reflected light from the measurement site P of the wafer 1. The two-dimensional luminance distribution of the reflected light in the regular reflection direction of the light emitted from each LED 12 to the measurement site P is detected by performing photoelectric conversion (imaging means).
In the example shown in FIG. 1, the camera 20 is arranged in one plane (a plane including the reference position Q) on which the light emitting unit of the LED 12 is arranged, and the front direction thereof is directed to the center of the surface of the wafer 1. It is installed as follows. That is, the camera 20 is installed such that the front direction thereof is a direction along a plane cross section at the center of the thickness direction of the wafer 1 (so that the wafer 1 is viewed from the side). Thereby, the camera 20 can observe the end face of the wafer 1 over the entire thickness direction of the wafer 1.
The focal point of the camera 20 is set at the reference position Q (that is, the measurement site P).
The computer 30 controls the LED drive circuit 11 in the light irradiating device 10 (flashing control of the LED 12), and controls the shutter of the camera 20 and captures a photographed image by the camera 20. The specific operation will be described later. Here, although not shown in FIG. 1, the computer 30 includes an interface for transmitting and receiving signals and acquiring image data with the LED drive circuit 11 and the camera 20.
The processing of the computer 30 shown below is realized by the MPU included in the computer 30 executing a program stored in advance in storage means such as a hard disk drive included in the computer 30.

Next, the principle of edge profile measurement by the shape measuring apparatus Z1 will be described.
When the measurement site P is irradiated with light, the light is regularly reflected at the glossy measurement site P. The image captured by the camera 20 is an image representing the luminance distribution of the reflected light.
FIG. 8 is a diagram schematically illustrating an example (a) of the shape of the measurement site P and an example (b) of an image captured by the camera 20 of the measurement site P.
FIG. 8A shows the shape of the measurement site P where the surface angle simply increases (or simply decreases). The vertical direction in FIG. 8A is the thickness direction of the wafer 1.
When such a measurement site P is imaged by the camera 20 while irradiating light with only one LED 12, an image as shown in FIG. 8B is obtained. In the image, the position Xpeak where the luminance peak occurs (the position in the X coordinate direction, hereinafter referred to as the peak luminance position) corresponds to the position where the light beam emitted from the LED 12 is specularly reflected at the measurement site P (regular reflection position). .
In addition, on the surface of the regular reflection position in the measurement site P, the incident angle and the outgoing angle (angle in the reflection direction) of light with respect to the normal direction are the same (symmetrical). Therefore, the light is regularly reflected at the measurement site P based on the peak luminance position Xpeak in the captured image of the camera 20 and the irradiation direction of the light to the measurement site P (the direction from the lit LED 12 toward the measurement site P). It is possible to uniquely calculate the position (regular reflection position) and the surface angle of the regular reflection position.
Here, before describing the measurement principle of the shape measuring apparatus Z1, reference will be made to symbols representing the light irradiation direction and the like with reference to FIG. 2A is a diagram schematically showing a state of the shape measuring device Z1 in plan view, and FIG. 2B is a diagram showing an enlarged portion of the reference position P. FIG. .
As shown in FIG. 2, the light irradiation angle when the direction of a straight line connecting the measurement site P and the camera 20 (hereinafter referred to as the camera front direction) is used as a reference is φ. Further, the surface angle with respect to a plane orthogonal to the camera front direction (hereinafter referred to as a plane corresponding to the XY plane in the captured image) in the regular reflection Px of the light at the measurement site P. Is θ.

Next, the principle of edge profile measurement by the shape measuring apparatus Z1 will be described in more detail with reference to FIG. Here, a case where the camera 20 is a telecentric lens type camera will be described.
A telecentric lens type camera forms an image on a CCD in a manner as shown in FIG.
When the camera 20 that detects the luminance distribution of the reflected light is a telecentric lens type camera as shown in FIG. 3, the direction of the reflected light reaching the CCD (light receiving unit) of the camera 20 as shown in FIG. The peak luminance position Xpeak where the front direction of the camera 20 is substantially parallel and where a bright peak exists in the captured image represents the regular reflection position Px of the light at the measurement site P as it is. Further, since the light irradiation direction and the reflection direction are symmetric with respect to the normal of the surface of the regular reflection position Px, (90−θ−φ / 2) = (90−φ), and the following ( 1) Formula is materialized.
θ = φ / 2 (1)
Therefore, the specular reflection position Px can be specified by specifying the peak luminance position Xpeak in the captured image by image processing. Furthermore, the surface angle θ at the regular reflection position Px can be specified from the light irradiation angle φ (known angle) determined according to the position (known position) of the lit LED 12.

Next, edge profile measurement by the shape measuring device Z1 employing a camera 20 that is not a telecentric lens system (hereinafter referred to as a non-telecentric lens system) will be described with reference to FIG.
A non-telecentric lens type camera forms an image on a CCD in the manner shown in FIG.
When the non-telecentric lens type camera 20 is employed, as shown in FIG. 7, the angle (direction) of the reflected light that reflects at the regular reflection position Px at the measurement site P and reaches the CCD of the camera 20 to form an image is determined. When expressed as an angle ψx with the camera front direction as a reference, 2θ + ψx = φ, and the following equation (2) is established. However, ψx is obtained in advance for each position in the coordinate system of the camera 20 (position in the X-axis direction).
θ = (φ−ψx) / 2 (2)
Therefore, by specifying the peak luminance position Xpeak in the photographed image by image processing, the regular reflection position Px at the measurement site P is determined based on the peak luminance position Xpeak, the angle ψx, and the distance from the camera 20 to the measurement site P. Can be identified. Further, the surface angle θ at the regular reflection position Px can be specified from the light irradiation angle φ (known angle) determined according to the position (known position) of the lit LED 12 based on the equation (2).

Further, whenever the LED 12 to be turned on is sequentially switched (that is, every time the light irradiation angle φ is switched), the image data of the measurement site P is acquired through the camera 20, and the light irradiation angle φ and the surface angle θ at that time are obtained. The surface angle θ for each of the plurality of regular reflection positions Px, that is, the distribution of the surface angle θ at the measurement site P can be obtained.
FIG. 10 illustrates an example of an image (image of the camera 20) representing image data obtained for each light irradiation angle φ with respect to the measurement site P having the same shape as that illustrated in FIG. The right direction toward FIG. 10 is the X-axis direction of the camera 20 coordinate system (that is, the thickness direction of the wafer 1).
As shown in FIG. 10, the high-luminance position Xpeak (position in the X direction) corresponding to the regular reflection Px at the measurement site P changes according to the change in the light irradiation angle φ. This high luminance position Xpeak corresponds to the regular reflection position Px at the measurement site P.
The regular reflection position Px has a slightly different distance from the LED 12 depending on the position. Therefore, the surface angle θ obtained by the above method includes an error corresponding to the distance difference. However, the error can be suppressed to a negligible level by sufficiently increasing the distance between the LED 12 and the measurement site P with respect to the surface displacement of the measurement site P.
In FIG. 10, the luminance distribution existing in the band-like high luminance portion is caused by the surface roughness of the measurement site P and the effective F number of the camera 20. Further, when a telecentric lens type camera is employed, part of the reflected light other than the reflected light parallel to the front direction of the camera also reaches the CCD of the camera 20.

On the other hand, FIG. 9 is a diagram schematically showing another example (a) of the shape of the measurement site P and an example (b) of an image captured by the camera 20 of the measurement site P.
FIG. 9A shows the measurement site P having the above-described depression shape. The vertical direction in FIG. 9A is the thickness direction of the wafer 1.
When such a measurement site P is imaged by the camera 20 while irradiating light with only one LED 12, as shown in FIG. 9B, an image having a plurality of peak luminance positions Xpeak is obtained. This phenomenon occurs when there are a plurality of regular reflection positions Px having the same surface angle φ. The method for obtaining the surface angle is when the measurement site P has a shape as shown in FIG. It is the same.
If the shape measuring device Z1 is used, the distribution of the surface angle can be measured even when the measurement site P has a hollow shape.

Next, a procedure for measuring the measurement site P of the wafer 1 by the shape measuring apparatus Z1 will be described with reference to the flowchart shown in FIG. Hereinafter, S1, S2,... Represent identification codes of processing procedures (steps). It is assumed that the process shown in FIG. 12 is started in a state where the measurement site P of the wafer 1 is arranged at the reference position Q.
[Steps S1 to S5]
First, the computer 30 initializes a number i for identifying each LED 12 (i = 1) (S1).
Then, the computer 30 controls lighting of the i-th LED 12 by controlling the LED driving circuit 11 (S2), imaging of the measurement site P by the camera 20 in the lighting state (shutter ON), and storage of the captured image (S3). The number i is sequentially counted up (S5), and the process is repeated until lighting and imaging of all the LEDs 12 are completed (S4). An image captured by the camera 20 is stored in a storage unit such as a hard disk included in the computer 30.
Through the processing of steps S1 to S4, the light irradiation device 10 sequentially irradiates the measurement site P with light at different irradiation angles φ (S2). Furthermore, image data (photographed image) representing the luminance distribution of reflected light from the measurement site P is acquired by the computer 30 through the camera 20 every time light is irradiated at different irradiation angles.

[Steps S6 to S11]
Next, the computer 30 executes the processes of steps S6 to S11 described below, and measures the image data (the brightness distribution of reflected light) corresponding to each LED 12 acquired by the process of step S3 and the LED 12 Based on the irradiation angle φ of the light applied to the part P, the distribution of the surface angle and the edge profile of the measurement part P are calculated (S11).
By the way, if the change width of the light irradiation angle φ by the light irradiation device 10 (here, the interval between the LEDs 12) is made extremely small, the position where the brightness of the reflected light becomes the highest every time the light irradiation angle φ is changed. By calculating, the distribution of the surface angle of the measurement site P can be calculated with high spatial resolution.
However, there is a limit to reducing the change width of the light irradiation angle φ. Further, as the change width of the light irradiation angle φ is reduced, the number of times of imaging by the camera 20 (number of times of collecting the luminance distribution of the reflected light) increases and the measurement time becomes longer. Further, the number of image data to be acquired by the computer 30 increases, leading to an increase in the required memory capacity in the computer 30.
Therefore, the computer 30 in the present embodiment obtains the distribution of the surface angle and the edge profile of the measurement site P by the following processing.

First, the computer 30 sets a number j for identifying each of a plurality of predetermined positions in the X coordinate direction (hereinafter referred to as a calculation target position Xj) in the imaging range of the camera 20 (an example of the light detection range of the light detection means). Initialization (j = 1) is performed (S6).
Then, for each calculation target position Xj, a correspondence relationship between the light irradiation angle φ and the luminance E of the reflected light (hereinafter referred to as φ-E correspondence relationship) is derived (S7).
FIG. 11 is an example of a graph showing the correspondence between the light irradiation angle φ (horizontal axis) and the reflected light luminance E (vertical axis) at a certain calculation target position Xj.
Further, the computer 30 performs a predetermined calculation based on the φ-E correspondence obtained in step S7, so that the light irradiation angle φpeak (hereinafter referred to as an estimated peak irradiation) when the luminance E of the reflected light peaks. The surface angle θj at the calculation target position Xj is calculated and stored (S8).

As shown in FIG. 11, the φ-E correspondence is based on discrete data. Here, except for the case where the LEDs 12 in the light irradiation device 10 are arranged at extremely wide intervals, the estimated peak is obtained by the interpolation calculation processing based on the φ-E correspondence relationship as shown in FIG. The hourly irradiation angle φpeak can be estimated. As specific examples of the interpolation calculation process, an interpolation calculation process based on the barycentric method and an interpolation calculation process based on a fitting process that regresses to a quadratic function or a Gaussian distribution function can be considered. It is also conceivable that the light irradiation angle φ when merely showing the maximum luminance without performing the interpolation calculation processing is set to the estimated peak irradiation angle φpeak. However, in this case, it should be noted that the error increases depending on the interval between the LEDs 12.
The method for calculating the surface angle θj based on the estimated peak irradiation angle φpeak is the same as the method for calculating the surface angle θ of the regular reflection position Px based on the light irradiation angle φ described above.
Then, the computer 30 repeats the processing of steps S7 to S8 until it is performed for all predetermined calculation target positions Xj while sequentially incrementing the number j (S10) (S9). The surface angle θj of each calculation target position Xj calculated in step S8 is stored in a storage unit such as a hard disk included in the computer 30.
The distribution of the surface angle θ of the measurement site P (information indicating the correspondence relationship between the calculation target position Xj and the surface angle θj) is obtained by the processes in steps S1 to S10 described above.
As described above, the computer 30 estimates the estimated peak for each of the plurality of calculation target positions Xj in the imaging range (that is, the light detection range) of the camera 20 based on the correspondence relationship between the light irradiation angle φ and the luminance E of the reflected light. The surface angle θj of each calculation target position Xj is calculated by performing an operation for estimating the hour irradiation angle φpeak (light irradiation angle when the reflected light has a peak luminance) (S7 to S10). As a result, the distribution of the surface angle θj can be measured with the same high spatial resolution as when the LEDs 12 in the light irradiation device 10 are arranged very densely. Theoretically, the spatial resolution of the surface angle distribution can be increased to the level of the resolution (pixel resolution) of the camera 20.
Note that a computer 30 ′ to be described later also executes the same processing as steps S7 to S10 described above (an example of the surface angle distribution calculating means).

Finally, the computer 30 calculates and stores the edge profile (surface shape) of the measurement site P based on the distribution of the surface angle θj obtained by the processes of steps S6 to S10 (S11), and ends the measurement process. Let At this time, the computer 30 displays the edge profile of the measurement site P on the display unit as necessary.
Here, the difference Δhj between the surface height of a certain calculation target position Xj and the surface height of the adjacent calculation target position Xj + 1 in the measurement site P can be calculated by the following equation (3).
Δhj = d · tanθj (3)
However, d is the distance (distance in the X-axis direction) between adjacent calculation target positions Xj in the measurement site P. Here, the distance between the pixels in the X-axis direction of the camera 20 is a distance converted into a real space.
By applying the formula (3) sequentially from the base point of the calculation target position Xj, the height distribution of the measurement site P, that is, the edge profile can be calculated.
FIG. 5 is a graph showing an example of the distribution and edge profile of the surface angle φ (x) obtained by measuring the measurement site P of a certain wafer 1 with the shape measuring device Z1. The horizontal axis represents the position in the thickness direction of the wafer 1, the left vertical axis represents the surface position of the measurement site (ie, edge profile), the right vertical axis represents the surface angle θ, and the surface angle θ represented by a thin solid line graph in FIG. (x) is obtained by replacing each calculation target position Xj with a position in the real space in the measurement site P. An edge profile represented by a thick solid line graph is calculated based on the equation (3).
Thus, if the shape measuring apparatus Z1 is used, the edge profile of the thin sample such as the wafer 1 can be measured with high accuracy.

[Second invention]
Next, the shape measuring apparatus Z2 according to the embodiment of the second invention will be described with reference to FIG. Hereinafter, only the difference between the shape measuring device Z2 and the shape measuring device Z1 will be described. In FIG. 13, the same components as those shown in FIG. 1 are denoted by the same reference numerals. FIG. 13A is a plan view (partially block diagram) of the shape measuring device Z2, and FIG. 13B is a side view (partially omitted) of the shape measuring device Z2.
As shown in FIG. 13, the shape measuring device Z2 includes two cameras 20R and 20L as the camera 20 that detects the luminance distribution of the reflected light from the measurement site P, which are different from each other with respect to the measurement site P. Arranged in the direction. Hereinafter, they are referred to as a first camera 20R and a second camera 20L, respectively. These two cameras 20R and 20L are cameras that capture a two-dimensional image of each of the surfaces on both sides in the thickness direction (edges of the front and back surfaces of the wafer 1) in the vicinity of the end surface of the measurement site P (see 2 above). Example of two imaging means).
In the example shown in FIG. 13, the two cameras 20R and 20L are in the direction of 90 ° with respect to the reference position Q (that is, the measurement site P) (direction of ± 45 ° with respect to the surface direction of the wafer 1). Has been placed. Thereby, each of the cameras 20R and 20L detects the brightness of the reflected light reflected in a part of the entire region (entire surface) of the measurement site P (region visible from each arrangement position).

By the way, as shown in FIG. 1, in the shape measuring apparatus Z1, the light emitting portions of all the LEDs 12 include the reference position Q and are in one plane orthogonal to the surface of the wafer 1 (thin sample), that is, , The wafer 1 (thin sample) at the reference position Q (measurement site P) is disposed so as to be located in a plane including a cross section in the thickness direction.
On the other hand, as shown in FIG. 13B, in the shape measuring apparatus Z2, on one of both sides of the plane 50 including the cross section in the thickness direction of the wafer 1 (thin sample) at the reference position Q (measurement site P). The lighting position of each LED 12 is located on the other side, and the arrangement position of the camera 20 (an example of the light detection means) is located on the other side. The plane 50 is a plane that includes the reference position Q (measurement site P) and is substantially orthogonal to the front and back surfaces of the wafer 1 (thin sample).
In the shape measuring device Z2, the positional relationship between the LEDs 12 and the camera 20 when viewed from the direction orthogonal to the plane in which the lighting positions of the LEDs 12 are arranged (FIG. 15A) is the same as those in the shape measuring device Z. This is the same as the positional relationship (FIG. 1A).
In the shape measuring device Z2, even if the LEDs 12 are continuously arranged in the front direction of the measurement site P, the LEDs 12 can be arranged so as not to interfere with the camera 20, so The spatial resolution of surface shape measurement can be further increased.

Furthermore, the shape measuring apparatus Z2 includes a computer 30 ′ that is different from the computer 30 described above and that has a part of the program to be executed.
The computer 30 ′ uses both the two cameras 20R and 20L (an example of the light detection unit and the imaging unit) every time the light irradiation angle φ is changed in the above-described step S3 (see FIG. 12). Control is performed so that image data is captured (detection of a two-dimensional luminance distribution) and stored.
Further, the computer 30 ′ obtains the image data for each of the image data (data representing the luminance distribution of the reflected light) obtained through the two cameras 20R and 20L in steps S7 and S8 (see FIG. 12). The distribution of the surface angle θj of a partial region of the measurement site P is calculated based on the irradiation angle of light (estimated peak irradiation angle φpeak). In the example shown in FIG. 13, the computer 30 ′ calculates the surface angle θj of the region close to the right surface (one surface) of the wafer 1 shown in FIG. 13 based on the image data obtained through the first camera 20R. Calculate the distribution. Similarly, the computer 30 ′ calculates the distribution of the surface angle θj of the region near the left surface (the other surface) of the wafer 1 based on the image data obtained through the second camera 20L. Here, some of these areas overlap.
Therefore, in the shape measuring apparatus Z2, light is irradiated sequentially on the measurement site P at different irradiation angles φ by the processing of steps S1 to S4, and further, light is irradiated at different irradiation angles. Furthermore, image data (captured image) representing the luminance distribution of the reflected light from the measurement site P is acquired by the computer 30 ′ through the camera 20 (an example of the reflected light luminance acquisition means).

Furthermore, the shape measuring apparatus Z2 includes a thickness measuring system that measures the thickness of the wafer 1 at the vicinity of the end face at the measurement site P (the edges of the front and back surfaces of the wafer 1).
The thickness measurement system is realized by two thickness measurement light sources 40 (40R and 40L) arranged on both front and back sides of the wafer 1, the two cameras 20 (20R and 20L), and the computer 30 ′. ing.
The light source 40 for thickness measurement is sufficient for the spot light collimated sufficiently thinly on each surface on both sides in the thickness direction (edges of the front and back surfaces of the wafer 1) in the vicinity of the end surface of the measurement site P, or on the surface of the wafer 1 It is a light source that irradiates finely condensed spot light. Although not shown in FIG. 13, a collimator lens and a condenser lens are arranged between the light source and the wafer as needed (an example of the second light irradiation means).
Further, the computer 30 ′ functioning as a component of the thickness measuring system has each surface on both sides in the thickness direction (wafer 1) in the vicinity of the end face of the measurement site P irradiated with the light from the thickness measuring light sources 40R and 40L. The image data of the images of the front and back surfaces of each of the two surfaces are acquired through the two cameras 20R and 20L, and based on the acquired image data, the irradiation positions of the light irradiated by the respective thickness measurement light sources 40R and 40L ( (Coordinate) is detected, and triangulation calculation based on the detected position is executed to calculate the thickness D of the wafer 1, and the calculation result is recorded in the storage unit (an example of the thickness calculation means).
In the example shown in FIG. 13, the thickness measurement light sources 40R and 40L respectively irradiate the surfaces on both sides in the thickness direction in the vicinity of the end face of the measurement site P substantially perpendicularly, and the scattered reflected light is emitted to the 2 This is an example of a thickness measurement system that obtains an image of an optical cutting line on the surface of the wafer 1 (the image of the line light) by receiving light with each of two cameras 20R and 20L.

FIG. 14 is a conceptual diagram showing the principle of thickness measurement in the shape measuring apparatus Z2.
In the shape measuring device Z2, the computer 30 ′ extracts an image of a light section line (line light image) from an image captured by the camera 20 provided with a telecentric lens, and the image with respect to a predetermined reference position (reference coordinates). A shift amount hccd (for example, a shift amount in the X-axis direction) in a predetermined direction (for example, the X-axis direction) of the position (coordinates) of the image of the light section line is detected. The reference position is an imaging position of the position Ps0 of the optical cutting line on the wafer 1 when the surface height of the wafer 1 is a predetermined reference height h0. Further, in FIG. 14, the actual position of the optical cutting line on the wafer 1 is expressed as Ps1.
Here, the difference between the actual height h1 of the surface of the wafer 1 and the reference height h0 is Δh01, the angle between the optical cutting line and the optical axis of the camera 20 is θ _L , and the measurement site P to the image sensor of the camera 20 Assuming that the magnification of the optical system along the path is M, Δh01 can be calculated based on the following equation (4).
Δh01 = hccd / (M · sin θ _L ) (4)
The computer 30 ′ calculates the heights Δh01R and Δh01L of the both surfaces of the wafer 1 based on the captured images of the two cameras 20R and 20L using the equation (4).

By the way, it is difficult to match the reference height h0 with high accuracy for each of the two cameras 20R and 20L (that is, for the front and back surfaces of the wafer 1).
Therefore, the calculator 30 ′ calculates the thickness D (measured value of the thickness) of the wafer 1 by the following equation (5) using a preset calibration value α.
D = Δh01R−Δh01L + α (5)
The calibration value α is set in advance by measuring the thickness of a calibration sample with a known thickness D by the thickness measurement system.
That is, the calculator 30 ′ calculates Δh01R and Δh01L based on a captured image of a calibration sample whose thickness D is known in advance, and applies the calculated values to the equation (5) to obtain the calibration value α. The calculated value is recorded in the storage unit.

Furthermore, the computer 30 ′ executes the same processing as in the above-described steps S6 to S11, whereby the image data (luminance distribution of reflected light) corresponding to each LED 12 obtained by the processing in step S3 and the LED 12 are used. Based on the irradiation angle φ of the light irradiated to the measurement site P, the surface angle distribution and the edge profile of the measurement site P are calculated (S11, an example of the surface angle distribution calculation means).
Further, in step S11 described above, the computer 30 ′ determines one of the distributions of the surface angles θj of the partial areas corresponding to the two cameras 20R and 20L (calculation results in the process of step S8). An edge profile (surface shape) is calculated for each region of the part, and the edge profile of the entire measurement site P is calculated by performing a process of connecting them (an example of a connection calculation unit).
Alternatively, the computer 30 ′ connects the distributions of the surface angles θj of the partial areas corresponding to the two cameras 20R and 20L (calculation results in the process of step S8) in the above-described step S11 (hereinafter referred to as “step S11”). The surface angle distribution θj of the entire measurement site P is calculated by performing a joining process), and the edge profile of the entire measurement site P is calculated based on the calculation result (an example of the joining calculation means).
At that time, the computer 30 ′ calculates the calculation result of the distribution of the surface angle θj of the partial area or the edge profile (surface shape) of each partial area based on the calculation result in the thickness direction of the wafer 1. The joining process is executed while adjusting their relative positions based on the measurement result (thickness D) of the thickness measurement system.
In this way, two methods are conceivable: a method in which the edge profiles of each region are obtained and then connected to each other, or a method in which the distribution of the surface angle θj of each region is joined and the edge profile of the entire region is obtained. .
According to the shape measuring apparatus Z2, for example, even if the field of view range (light detection range) of one camera is about ± 60 °, ± 90 ° (total 180 ° required for general edge profile measurement) ) Surface angle distribution measurement in the range of.

Hereinafter, the joining process by the computer 30 ′ will be described.
In the joining process, the computer 30 ′ minimizes the difference in the distribution of the edge profiles or surface angles θj corresponding to the cameras 20R and 20L with respect to the overlapping portions of the partial areas corresponding to the cameras 20R and 20L. A known fitting process is executed so that
In the fitting process, the thickness profile of the wafer 1 (here, the X-axis direction of the captured images of the cameras 20R and 20L) is used as an adjustment parameter for the relative position of the distribution of the edge profile or surface angle θj corresponding to each camera 20R and 20L. And the offset in the direction orthogonal to the thickness direction (here, the Y-axis direction of the captured images of the cameras 20R and 20L) can be considered as adjustment parameters.
In the shape measuring apparatus X, the thickness D of the wafer 1 is measured in advance by the thickness measuring system, and the offset in the thickness direction is adjusted based on the thickness D (measured value).
Further, in addition to the offset in the thickness direction (X-axis coordinate) and the offset in the direction orthogonal to the adjustment parameter (Y-axis coordinate) in the fitting process, the edge profile or surface angle θj corresponding to each camera 20R, 20L It is also conceivable to add a relative slope (angle) of the distribution.

FIG. 15 is a diagram illustrating the state before and after the fitting process of the surface angle distribution and the edge profile corresponding to each of the two cameras obtained by the shape measuring apparatus Z2. FIG. 15A shows before the fitting process, and FIG. 15B shows the after the fitting process.
Further, in the figure, the notations “surface angle distribution R” and “edge profile R” represent the distribution and edge profile of the surface angle θj corresponding to the first camera 20R. Similarly, “surface angle distribution L” and “edge profile L” represent the distribution and edge profile of the surface angle θj corresponding to the second camera 20L.
As shown in FIG. 15A, the surface angle distribution R of the region corresponding to the first camera 20R and the edge profile R based thereon, and the surface angle distribution L of the region corresponding to the second camera 20L and the edge based thereon There may be a deviation from the profile L.
If these results are connected by performing a fitting process on the overlapping region, as shown in FIG. 15B, the surface angle distribution (entire) or edge profile (entire) of the entire region of the measurement site P is obtained. Is obtained.

Hereinafter, a specific example of the fitting process using the thickness direction offset, the offset in the direction orthogonal thereto, and the relative inclination (angle) as adjustment parameters will be described. The adjustment amount of the thickness direction offset is ΔXc, the adjustment amount of the offset in the direction orthogonal to the thickness direction is ΔYc, and the adjustment amount of the relative inclination (angle) is Δψ (hereinafter referred to as a relative angle adjustment amount). . In the following, the joining of the edge profile R and the edge profile L will be described, but the joining of the surface angle distribution R and the surface angle distribution L can also be realized by the same processing.
The computer 30 ′ sets the relative angle adjustment amount ΔYc to sequentially different values within a predetermined range, and fixes the angle of one edge profile R while the angle of the other edge profile L is set. Correction (correction) is made by the amount ΔYc. The relative angle adjustment amount ΔYc is, for example, a value that is sequentially set in increments of 0.01 ° within a range of −1 ° to + 1 °.
Further, every time the computer 30 ′ performs the angle correction according to the relative angle adjustment amount ΔYc, the computer calculates the thickness Dx (hereinafter referred to as the thickness on the profile) based on the edge profile R and the edge profile L after the angle correction. ) Is adjusted so that the thickness direction offset ΔXc matches the thickness D measured in advance by the thickness measurement system.
In FIG. 15, the thickness on the profile before adjustment of the thickness direction offset ΔXc is expressed as Dx1 (= D + ΔXc), and the thickness on the profile after the adjustment is expressed as Dx2 (= D).

Then, every time the offset ΔXc is adjusted, the computer 30 ′ adjusts the offset ΔYc so that the difference between the edge profile R and the edge profile L after adjusting the offset ΔXc is minimized. The difference ΔPfmin between the two edge profiles is recorded in the storage unit.
Here, the index value representing the difference between both edge profiles is, for example, from each coordinate position on one edge profile R to the other edge profile L in the overlapping range of both edge profiles in the wafer thickness direction (X-axis direction). The average value of the distance (the distance to the portion closest to the coordinate position on the edge profile R) or the like.
Finally, the computer 30 ′ corrects the edge profile L according to the relative angle adjustment amount ΔYc and the offsets ΔXc and ΔYc when the difference ΔPfmin between the two edge profiles recorded as described above is the minimum, and after the correction The edge profile obtained by integrating the edge profile L and the edge profile R is used as the edge profile of the entire measurement site P, and is recorded in the storage unit.
By the joining process (fitting process) described above, offset adjustment in the thickness direction can be performed with high accuracy, and as a result, the entire surface shape of the measurement site P can be measured with high accuracy.
The calibration value α and the relative angle adjustment amount Δψ are mainly caused by installation errors of the cameras 20R and 20L. Therefore, after the position adjustment of the cameras 20R and 20L is performed, the relative angle adjustment amount ΔYc when the calibration value α and the difference ΔPfmin between the two edge profiles is minimized is calculated and stored only once. Then, the joining process (fitting process) can be performed using these values thereafter.

By the way, as the wafer 1 is closer to the edge profile part (the chamfered end face), the individual difference in thickness is larger, and as the wafer 1 is closer to the center (away from the edge profile part), the individual difference in thickness is smaller. When the measurement result (thickness D) of one time (of a certain wafer 1) by the thickness measurement system is shared in the shape measurement of a plurality of wafers 1, it is desirable to measure the thickness at a position where individual differences are small.
On the other hand, at a position close to the center of the wafer 1 (position away from the end face), shape measurement according to the present invention (shape measurement based on an image of regular reflection light) becomes difficult.
FIG. 17 is a cross-sectional view showing a position suitable for thickness measurement in the wafer 1 (semiconductor wafer) that is the object of shape measurement. Note that the protrusion dimension (0.5 mm) of the edge profile portion and the thickness (0.7 mm) of the wafer 1 shown in FIG. 17 represent an example.
From experience, as shown in FIG. 17, edge profile portions (front and back surfaces) on the front and back surfaces (“front surface” and “back surface” in the figure) of the wafer 1 having a thin plate shape (for example, a thickness of about 0.7 mm). A position Qd that is about 1 mm inside from the boundary position with the bevel portion of each surface) is a position where the individual difference in thickness is relatively small and the shape measurement according to the present invention is also possible.
Therefore, when the object to be measured (thin sample) is a thin semiconductor wafer 1, the thickness measurement system moves the wafer 1 to a position Qd about 1 mm inside from the boundary position with the edge profile portions (end faces) on both the front and back surfaces. It is desirable to measure the thickness of the wafer 1 at the position Qd by irradiating the light of the thickness measuring light source 40. Depending on the size of the semiconductor wafer 1, even if the thickness of the wafer 1 is measured at a position about 3 mm to about 5 mm inside from the boundary position, a measurement value effective for the offset adjustment can be obtained.

FIG. 16 is a diagram illustrating a schematic configuration of a shape measuring device Z2 ′ (an example of a shape measuring device according to the embodiment of the second invention) which is an application example of the shape measuring device Z2 described above.
Hereinafter, only the difference between the shape measuring device Z2 ′ and the shape measuring device Z2 will be described. In FIG. 16, the same components as those shown in FIGS. 1 and 13 are denoted by the same reference numerals. 16A is a plan view (partially block diagram) of the shape measuring device Z2 ′, and FIG. 16B is a side view (partially omitted) of the shape measuring device Z2 ′.
The shape measuring device Z2 ′ has the same configuration as the shape measuring device Z2 except that the position of the thickness measuring light source 40 (40R, 40L) is different.
As shown in FIG. 16, the thickness measuring system in the shape measuring apparatus Z2 ′ uses line light to each of the surfaces on both sides in the thickness direction in the vicinity of the end surface of the measurement site P by the thickness measuring light sources 40R and 40L. Is irradiated from an oblique direction, and the specularly reflected light is received by the two cameras 20R and 20L, respectively, to obtain an image of the light cutting line on the surface of the wafer 1 (image of the line light).
In such a shape measuring apparatus Z2 ′, similarly to the shape measuring apparatus Z2, the computer 30 ′ executes simple triangulation calculation based on the images taken by the two cameras 20R and 20L, thereby obtaining the wafer 1 Thickness D can be calculated.

Further, in the process of sequentially turning on and turning on the plurality of LEDs 12 through the LED drive circuit 11 (steps S1 to S5), the computer 30 ′ simultaneously turns on the plurality of LEDs 12 corresponding to the cameras 20R and 20L for some of the LEDs 12. Control to turn on (an example of a switching type light irradiation means).
As shown in FIG. 13, among the plurality of LEDs 12 arranged on the arc, a part of the LED 12R (for example, LED 12Ra) disposed on the opposite side of the second camera 20L with respect to the first camera 20R is as follows. The output light is blocked by the wafer 1 and does not reach the second camera 20L (not detected).
Similarly, with respect to a part of the LED 12L (for example, the LED 12La) disposed on the opposite side to the first camera 20R with respect to the second camera 20L, the output light is blocked by the wafer 1 and the second camera 20L. Will not reach.
Therefore, in step S2, the computer 30 ′ causes the LEDs corresponding to the first camera 20R (LED12Ra, etc.) and the LEDs corresponding to the second camera 20L (LED12La, etc.) to light up simultaneously. The drive circuit 11 is controlled.
Thereby, the measurement time can be shortened.
The shape measuring apparatus Z2 shown in FIG. 13 includes two cameras 20, but the same operation and effect can be obtained even with a configuration including three or more cameras 20.

In the embodiment described above, the LED 12 that is a diffused light source is directly used as a light source. The reason why such a configuration can be adopted is that each LED 12 is arranged at a distance far enough from the size (depth length) of the measurement site P, and the light from each LED 12 is parallel light at the measurement site P. It is because it can be considered.
On the other hand, when a light source such as the LED 12 is disposed close to the measurement site P, it is desirable to irradiate the measurement site P with the light from the light source as parallel light using a lens.
In the above-described embodiment, the LED 12 is used as the light source. However, other types of light sources such as a laser diode, an incandescent bulb, and a fluorescent lamp may be used.
It is also conceivable that the camera 20 is installed at a position and orientation different from those of the above-described embodiment according to the purpose.
In general edge profile measurement, it is sufficient if the surface angle distribution in the one-dimensional direction (the thickness direction of the wafer 1) can be measured for each measurement site P. For this reason, as a means for detecting the brightness of the reflected light from the measurement site P, it is conceivable to use a one-dimensional light receiver in which a plurality of photoelectric conversion elements are arranged in a line (in a one-dimensional direction). However, in that case, in the shape measuring apparatus Z2, it is necessary to separately provide a camera (imaging means) constituting the thickness measuring system.
The shape measuring apparatus X2 includes the thickness measuring system that optically measures the thickness of the wafer 1 using the thickness measuring light source 40 and the two cameras 20R and 20L. A shape measuring device equipped with a non-contact type thickness gauge using the above can also be considered.
In addition, the shape measuring apparatus according to the present invention can measure the edge profile in the same manner for a thin sample such as an aluminum substrate or a glass substrate.

In the above-described embodiment, the configuration in which the reflected light from the measurement site P is directly incident on the camera 20 has been described. However, a configuration in which an optical device (such as a mirror) that changes the reflected light from the measurement site P is provided and the reflected light that is changed by the optical device is incident on the camera 20 is also conceivable. Thereby, when it is desired to detect reflected light in a direction along a plane on which the light source (LED 12) is arranged, interference between the camera 20 and the light source having a relatively large installation space can be avoided. Thereby, the range of the light irradiation angle can be expanded, and the measurement range of the surface angle of the measurement site P can be further expanded.
In addition, the light irradiation device 10 in the above-described embodiment is a switching type light irradiation device that sequentially turns on and turns on a plurality of light sources (LEDs 12). However, as a light irradiation device, one or a relatively small number of light sources (LEDs, etc.) are sequentially moved to a plurality of positions in one plane (for example, positions where the LEDs 12 are arranged in the light irradiation device 10). A moving light irradiation device that includes a light source moving mechanism and lights the light source at each position of the moving destination is also conceivable. Even with such a moving light irradiation device, similarly to the light irradiation device 10, it is possible to configure a device that sequentially irradiates the measurement site P with different irradiation angles φ.
As this movable illumination device, for example, a rail in an arc shape centered on the reference position Q, a moving mechanism for moving a light source such as an LED along the rail, and an LED is predetermined by this moving mechanism It is conceivable to include a position sensor that detects arrival at each of a plurality of positions and a control device that controls the moving mechanism so that the light source sequentially moves to each position detected by the position sensor.

By the way, when using the light irradiation device 10 that switches a plurality of light sources (the LEDs 12 in the above-described embodiment) and irradiates the measurement site P with light, the individual light sources change from each light source to the measurement site P at the reference position Q. There may be variations in the amount (intensity) of the irradiated light. Therefore, it is important to adjust in advance so that the variation becomes as small as possible.
Specifically, when a light sensor is disposed at the reference position Q where the measurement site P is disposed, and each light source is sequentially switched and turned on, the light intensity detected by the light sensor becomes a substantially constant level. Thus, the power (voltage or current) supplied to each light source, that is, the light emission amount (light emission intensity) of each light source is adjusted in advance.
For example, when the light source is an LED, a variable resistor is provided on the power supply line for each LED, and the supply current to each LED is adjusted in advance by adjusting the resistance value of the variable resistor. Alternatively, a pulse width modulation device that can control the power supply to each LED by pulse width modulation (PWM) is provided, thereby adjusting the power supplied to each LED in advance.
In addition, the light intensity detected by the camera 20 when a reflecting member (mirror, etc.) having a known reflection direction and reflectance is arranged at the reference position Q where the measurement site P is arranged, and each light source is sequentially switched on. It is also conceivable to calculate and store a light intensity correction coefficient for each light source in advance based on the variation of the light intensity. In actual measurement, measurement is performed using the corrected measurement value (light intensity distribution) based on the correction coefficient.
By performing the adjustment as described above, it is possible to avoid occurrence of a measurement error due to variations in the characteristics of the light source.

  The present invention can be applied to a shape measuring apparatus for a thin sample such as an aluminum substrate or a glass substrate for semiconductor wafers and hard disks.

The schematic block diagram of the shape measuring apparatus Z1 which concerns on embodiment of 1st invention. The figure showing the definition of a light irradiation angle and a surface angle. The figure showing the characteristic of the camera of the telecentric lens system which can be employ | adopted for the shape measuring apparatus Z1. The figure which represented typically the relationship between the surface angle of a measurement site | part at the time of employ | adopting the camera of a telecentric lens system for the shape measuring apparatus Z1, and an optical path. The graph showing the surface angle distribution and edge profile of the measurement site | part calculated by the shape measuring apparatus Z1. The figure showing the characteristic of the camera of a non-telecentric lens system which can be employ | adopted for the shape measuring apparatus Z1. The figure which represented typically the relationship between the surface angle of a measurement site | part at the time of employ | adopting the camera of a non-telecentric lens system for the shape measuring apparatus Z1, and an optical path. The figure which represented typically the 1st example of the shape of a measurement part, and the picked-up image by the camera of shape measuring apparatus Z1. The figure which represented typically the 2nd example of the shape of a measurement site | part, and the picked-up image by the camera of shape measuring apparatus Z1. The figure showing an example of the picked-up image by shape measuring apparatus Z1. The graph showing an example of the correspondence of the light irradiation angle in a predetermined calculation target position, and reflected light brightness | luminance. The flowchart showing the measurement procedure by the shape measuring apparatus Z1. The figure showing schematic structure of the shape measuring apparatus Z2 which concerns on embodiment of 2nd invention. The conceptual diagram showing the principle of the thickness measurement in the shape measuring apparatus Z2. The figure showing the state before and after the fitting process of the surface angle distribution and edge profile corresponding to each of two cameras obtained by the shape measuring apparatus Z2. The figure showing schematic structure of shape measuring apparatus Z2 'which is an application example of shape measuring apparatus Z2. Sectional drawing showing the position suitable for the thickness measurement in the semiconductor wafer which is the object of shape measurement.

Explanation of symbols

Z1, Z2, Z2 ': Shape measuring device 1: Wafer 10: Light irradiation device 11: LED drive circuit 12: LED
13: Notches 20, 20R, 20L: Cameras 30, 30 ′: Computer 40 (40R, 40L): Light source for thickness measurement 50: a plane including a cross section in the thickness direction of the wafer at the measurement site

Claims (9)

A shape measuring device for measuring the shape of the end face of a thin sample,
By illuminating the light source at each of a plurality of positions in one plane, light is sequentially irradiated at different irradiation angles to the measurement site including the end surface of the thin sample and the surfaces on both sides in the thickness direction in the vicinity thereof. Light irradiation means;
A plurality of one-dimensional or two-dimensional luminance distributions that are arranged in different directions with respect to the measurement part and detect reflected light in a substantially regular reflection direction from the measurement part by light irradiation of the first light irradiation means. Light detection means,
Reflected light luminance acquisition means for acquiring the luminance distribution of the reflected light from the measurement site through the light detection means each time light is sequentially irradiated at different irradiation angles by the first light irradiation means;
For each of the plurality of reflected light luminance distributions acquired by each of the plurality of reflected light luminance acquisition means, based on the luminance distribution of the reflected light and the irradiation angle of the light emitted by the first light irradiation means, Surface angle distribution calculating means for calculating the distribution of the surface angle of a partial region of the measurement site;
A thickness measuring means for measuring the thickness of the thin sample with respect to the portions on both sides in the thickness direction in the measurement site;
The surface angle distribution of the surface shape of each of said partial region based on the operation result of the distribution of the surface angle of the partial region said by the computing means, the thickness measuring means and their relative positions in the thickness direction of the thin sample by performing the measurements on the basis of the adjustment to piece together process, and joining means for calculating a front surface shape of the entire measurement site,
A shape measuring apparatus comprising: The light detection means includes two imaging means for capturing a two-dimensional image of each surface on both sides in the thickness direction of the measurement site;
The thickness measuring means is
Second light irradiating means for irradiating each of the surfaces on both sides in the thickness direction of the measurement site;
Acquiring images of the surfaces on both sides in the thickness direction of the measurement site irradiated with light by the second light irradiation means through the two imaging means, and detecting a light irradiation position based on the acquired images; Thickness calculating means for calculating the thickness of the flake sample by
The shape measuring apparatus according to claim 1, comprising:   The surface angle distribution calculating unit has a peak luminance of the reflected light based on a correspondence relationship between the irradiation angle of the light and the luminance of the reflected light for each of a plurality of calculation target positions in the light detection range of the light detecting unit. The shape measuring apparatus according to claim 1, wherein a surface angle at each of the calculation target positions is calculated by performing an operation for estimating an irradiation angle of the light when   The first light irradiating means sequentially illuminates the measurement site with different irradiation angles by sequentially switching and lighting a plurality of light sources arranged at a plurality of positions in the one plane. The shape measuring device according to any one of claims 1 to 3, wherein the shape measuring device is a switching type light irradiation means.   The shape measuring apparatus according to claim 4, wherein the plurality of light sources in the switchable light irradiating means are arranged on an arc centered at the arrangement position of the measurement site.   The shape measuring apparatus according to claim 1, wherein the plurality of light detecting means are two light detecting means arranged in a direction of about 90 ° with the measurement site as a base point. The thin sample is a thin semiconductor wafer,
The shape measuring apparatus according to claim 1, wherein the thickness measuring unit measures the thickness of the semiconductor wafer at a position approximately 1 mm inside from a boundary position between the front and back surfaces of the semiconductor wafer and a bevel portion. . A shape measuring method for measuring the shape of an end face of a thin sample,
The first light irradiation means for turning on the light source at each of a plurality of positions in one plane emits light at different irradiation angles sequentially with respect to the measurement site including the end surface of the thin sample and the surfaces on both sides in the thickness direction in the vicinity thereof. A first light irradiation step of irradiating;
One-dimensional or two-dimensional luminance of reflected light from the measurement site in a substantially regular reflection direction by light irradiation in the first light irradiation step by light detection means arranged in different directions with respect to the measurement site. A light detection process for detecting the distribution;
A reflected light luminance acquisition step of acquiring a luminance distribution of reflected light from the measurement site by execution of the light detection step each time light is irradiated at sequentially different irradiation angles in the first light irradiation step;
For each of the plurality of reflected light luminance distributions acquired by the reflected light luminance acquisition step, the measurement site is based on the luminance distribution of the reflected light and the irradiation angle of the light irradiated by the first light irradiation step. A surface angle distribution calculating step for calculating the distribution of the surface angle of a part of the area,
A thickness measuring step of measuring the thickness of the thin sample with respect to portions on both sides in the thickness direction in the measurement site by a predetermined thickness measuring means;
By a predetermined calculation means, the said surface shape of each of the partial region based on the operation result of the distribution of the surface angle of the partial region by the surface angle distribution calculating step, thereof in the thickness direction of the thin sample relative by executing the processing position joining adjusted based on the measurement result of the thickness measuring step, and joining calculating step of calculating a front surface shape of the entire measurement site,
The shape measuring method characterized by performing. The light detection means includes two imaging means for capturing a two-dimensional image of each surface on both sides in the thickness direction of the measurement site;
In the thickness measurement step,
A second light irradiating step of irradiating each surface on both sides in the thickness direction of the measurement site with a predetermined second light irradiating means;
Acquiring images of the surfaces on both sides in the thickness direction of the measurement site irradiated with light in the second light irradiation step through the two imaging means, and detecting a light irradiation position based on the acquired images; A thickness calculating step of performing a process of calculating the thickness of the flake sample by a predetermined calculating means;
The shape measuring method according to claim 8, wherein:

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