JP2023009788A - Crack detection device and method - Google Patents

Abstract

To provide a crack detection device and method with which it is possible to detect the crack depth of a crack that is formed inside of a wafer with good accuracy.SOLUTION: Provided is a crack detection method for detecting the crack depth of a crack formed along a scheduled cut line of a street (ST) between semiconductor devices on a wafer (W), the method comprising: a step for inclining, with respect to the widthwise direction of the street, an optical path (AR) that is determined by the optical path of detection light (L1) with which the wafer is obliquely illuminated in a diagonal direction from a position off-centered from the main optical axis and the optical path of reflected light (L2) from the wafer; and a step for obliquely illuminating the wafer with detection light while the optical path plane is inclined with respect to the widthwise direction of the street and detecting the crack depth of the crack on the basis of the reflected light from the wafer.SELECTED DRAWING: Figure 9

Description

The present invention relates to a crack detection device and method, and more particularly to a crack detection device and method for detecting cracks formed inside a workpiece.

Conventionally, laser beams are focused on the inside of a silicon wafer, which is the work piece, and are irradiated along the planned cutting lines, and along the planned cutting lines, a laser processing area, which serves as the starting point for cutting, is created inside the wafer. Forming laser dicing machines are known. The wafer on which the laser-processed region is formed is then split along the planned cutting lines by a splitting process such as expanding or breaking to separate individual chips.

When a laser-processed region is formed on a wafer by a laser dicing device, cracks extend from the laser-processed region in the thickness direction of the wafer. If the crack reaches the surface (device surface) of the wafer, it can be properly divided into chips (semiconductor devices) in the breaking process.

Therefore, after forming the laser-processed region by the laser dicing device, before the cleaving process, whether the laser-processed region, which is the starting point for dividing the wafer, was properly formed, that is, the crack formed inside the wafer By detecting the crack depth, it is possible to accurately predict the quality of splitting into chips in the breaking process.

Patent Documents 1 and 2 disclose a crack detection device and method for non-destructively detecting the crack depth of a crack formed inside a wafer.

JP 2017-133997 A JP 2020-076651 A

By the way, since the pattern of the semiconductor device is formed on the wafer, the light quantity of the reflected light from the wafer is affected by the reflectance of the pattern even when the measurement operation is performed in a place where no crack is formed. receive. In the conventional crack detection device, since the reflectance of the pattern is superimposed on the detection result of the reflected light, there is a problem that the detection accuracy of the crack position is lowered.

In order to solve the above problem, the reflectance of the pattern measured in advance before laser processing the wafer is used to detect the crack position by comparing it with the measurement result at the same position after laser processing. can be considered. However, even if the reflectance of the pattern measured in advance is used, there is a problem that the influence of the reflectance of the pattern cannot be sufficiently removed for the following reasons.

First, an outline of crack detection will be described. In the above-described crack detection apparatus, as shown in FIGS. Reflected light L2 from W is detected. The crack depth of the crack formed inside the wafer W is detected by detecting the signal intensity of the reflected light L2.

FIG. 15 is a plan view showing an example of measurement positions on the wafer W, and FIG. 16 shows the relationship between the focal point position (height direction movement amount) of the reflected light L2 from the wafer W and the detection result of the signal intensity. is a graph showing In FIG. 15, the measurement position is shown by superimposing the lens pupil 504A of the condenser lens 504 on the wafer W. As shown in FIG. The measurement positions in (a) and (b) of FIG. 15 correspond to the detection results of (a) and (b) in FIG. 16, respectively.

In the example shown in FIG. 15, the semiconductor devices on the wafer W are partitioned by streets (line to be cut) ST, and a crack is formed along the center of the street ST. When crack detection is performed by the above-described crack detection apparatus, the detection light L1 that illuminates the wafer W in an oblique direction and the reflected light L2 from the wafer W are directed in the direction of the street ST as shown in FIG. (hereinafter referred to as the street direction D1). In the following description, the plane defined by the optical paths of the detected light L1 and the reflected light L2 is called an "optical road surface".

In this case, as shown in FIGS. 15A and 15B, when the measurement position of the crack shifts, as shown in FIGS. is different. In particular, when the pattern is fine, the change in signal intensity due to the displacement of the measurement position becomes significant. Therefore, even if the reflectance of the pattern measured in advance is used, the influence of the reflectance of the pattern cannot be sufficiently removed.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a crack detection apparatus and method capable of accurately detecting the depth of a crack formed inside a wafer.

To achieve the above object, a crack detection device according to a first aspect of the present invention detects the depth of a crack formed along a planned cutting line of a street between semiconductor devices on a wafer. Crack detection means for illuminating the wafer obliquely with detection light from a position off-center from the main optical axis and detecting the crack depth of the crack based on the reflected light from the wafer; and an optical road surface tilting means for tilting the optical road surface determined by the optical path of the reflected light with respect to the width direction of the street.

A crack detection device according to a second aspect of the present invention is characterized in that, in the first aspect, the optical road surface inclination means is such that when the detection light is scanned in the depth direction of the wafer, the reflection of the detection light from the wafer falls within the range of the street. Tilt the light surface with respect to the width of the street, as is done in .

A crack detection device according to a third aspect of the present invention, in the first or second aspect, has an opening at a position eccentric from the main optical axis, and transmits a part of the light emitted from the light source to the opening. and the optical road surface tilting means includes a limiting member rotating means for tilting the optical road surface with respect to the width direction of the street by rotating the limiting member around the main optical axis. .

A crack detection apparatus according to a fourth aspect of the present invention, in any one of the first to third aspects, comprises a stage on which the wafer is placed, and the optical road surface tilting means moves the stage around the main optical axis. It includes stage rotating means for tilting the optical path with respect to the width direction of the street by rotating it.

A crack detection method according to a fifth aspect of the present invention is a crack detection method for detecting a crack depth of a crack formed along a planned cutting line of a street between semiconductor devices on a wafer, a step of tilting, with respect to the width direction of the street, an optical path defined by the detection light obliquely illuminating the wafer from a position eccentric from the wafer and the optical path of the reflected light from the wafer; and a step of illuminating the wafer with the detection light in an oblique direction with the optical surface inclined with respect to the wafer, and detecting the crack depth of the crack based on the reflected light from the wafer.

ADVANTAGE OF THE INVENTION According to this invention, the crack depth of the crack formed inside the wafer can be accurately detected.

FIG. 1 is a block diagram showing a crack detection device according to a first embodiment of the invention. FIG. 2 is a diagram showing a state when a workpiece is illuminated with polarized detection light. FIG. 3 is a diagram showing a state when polarized illumination of the detection light is performed on the workpiece. FIG. 4 is a diagram showing a state when polarized illumination of the detection light is performed on the workpiece. FIG. 5 is a diagram showing how reflected light is received by the photodetector. FIG. 6 is a diagram showing how reflected light is received by the photodetector. FIG. 7 is a diagram showing how reflected light is received by the photodetector. FIG. 8 is a diagram for explaining a path along which reflected light from a workpiece reaches a condenser lens pupil. FIG. 9 is a plan view showing an optical path. FIG. 10 is a plan view showing an enlarged lens pupil of the condenser lens. FIG. 11 is a front view showing optical paths of detection light and reflected light for crack detection. FIG. 12 is a graph showing the relationship between the position of the focal point of the reflected light from the wafer and the detection result of the signal intensity. FIG. 13 is a block diagram showing a crack detection device according to a second embodiment of the invention. FIG. 14 is a diagram (perspective view and plan view) showing optical paths of detection light and reflected light for crack detection. FIG. 15 is a plan view showing an example of measurement positions on the wafer. FIG. 16 is a graph showing the relationship between the position of the focal point of the reflected light from the wafer and the detection result of the signal intensity.

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a crack detection device and method according to the present invention will be described below with reference to the accompanying drawings.

[First Embodiment]
FIG. 1 is a block diagram showing a crack detection device according to a first embodiment of the invention.

The crack detection device 10 according to the present embodiment irradiates the wafer W with the detection light L1 and detects the reflected light L2 from the wafer W, so that the crack depth of the crack K formed inside the wafer W is to detect The crack detection device 10 is used in combination with a laser dicing device (not shown) that forms a laser processing area inside the wafer W. , the description of the configuration of the laser dicing apparatus is omitted.

In the following description, a three-dimensional orthogonal coordinate system is used in which the stage 510 on which the wafer W is placed is a plane parallel to the XY plane, and the depth direction of the wafer W is the Z direction.

As shown in FIG. 1, the crack detection device 10 according to the present embodiment includes a light source unit 100, an illumination optical system 200, an interface detection optical system 300, a crack detection optical system 400, a control unit 500, a focus adjustment mechanism 502, It includes a condenser lens 504 , an operation section 506 , a display section 508 and a stage 510 . The wafer W to be measured is placed on the stage 510 so that its front surface Wa is in contact with the stage 510, and the reflected light L2 from the wafer W when the detection light L1 from the light source unit 100 is incident from the back side Wb. By detecting , the interface of the wafer W and the crack K formed inside the wafer W are detected.

The light source unit 100 emits detection light L1 used for detecting the interface of the wafer W and detecting the crack K formed inside the wafer W. FIG. Here, when the wafer W is a silicon wafer, it is desirable to use infrared light with a wavelength of 1,000 nm or more as the detection light L1.

The light source section 100 includes a light source 102 , a collimating lens 104 and a limiting member 106 . The light source 102 , collimating lens 104 and limiting member 106 are arranged along the main optical axis AX coaxial with the lens optical axis of the condenser lens 504 .

The light source 102 emits detection light L1 along the main optical axis AX. As the light source 102, for example, an LED (Light Emitting Diode) light source can be used. The light source 102 is connected to the control unit 500 , and the control unit 500 controls emission of the light source 102 .

The collimator lens 104 adjusts the detection light L1 emitted from the light source 102 so that it becomes parallel light.

The restricting member 106 is formed with an opening 106A. The limiting member 106 is a light blocking member that blocks part of the detection light L1 from the collimator lens 104 . The restricting member 106 can be moved in and out of the optical path of the detection light L1 by a drive mechanism (for example, a motor M1). The control unit 500 controls the restricting member moving motor M1 to control appearance and retraction of the restricting member 106 . The control unit 500 can also control the motor M2 for rotating the limiting member to rotate the limiting member 106 around the main optical axis AX. When the crack detection optical system 400 detects the crack K, the limiting member 106 shields part of the detection light L1 and decenters the detection light L1 with respect to the main optical axis AX. The restricting member 106 will be described later.

The illumination optical system 200 guides the detection light L1 emitted from the light source section 100 to the condenser lens 504 . Illumination optics 200 includes relay lenses 202 and 206 and mirror 204 . The detection light L1 emitted from the light source unit 100 passes through the relay lens 202 and is reflected by a mirror (for example, a total reflection mirror) 204 to bend the optical path. The detection light L1 reflected by the mirror 204 is transmitted through the relay lens 206 and emitted toward the condenser lens 504 .

The condenser lens 504 condenses (focuses) the detection light L1 emitted from the illumination optical system 200 onto the wafer W. As shown in FIG. The condenser lens 504 is arranged at a position facing the wafer W and arranged coaxially with the main optical axis AX.

The focus adjustment mechanism 502 adjusts the condensing position of the detection light L1 on the wafer W. FIG. The focus adjustment mechanism 502 includes a driving section that moves at least one of a condenser lens 504 and a stage 510 on which the wafer W is placed. The focus adjustment mechanism 502 adjusts the relative position in the XYZ directions between the condenser lens 504 and the stage 510, thereby moving the condensing position of the detection light L1 in the XYZ directions.

If the condenser lens 504 is movable in the Z direction together with the processing head (not shown) of the laser dicing device, the focus adjustment mechanism 502 may include a driving mechanism for the processing head. In this case, it is possible to combine the position adjustment (coarse adjustment) of the focal point by the drive mechanism of the processing head and the position adjustment (fine adjustment) of the focal point by the piezo actuator.

Reflected light L2 collected by the condenser lens 504 and reflected by the wafer W is guided to the interface detection optical system 300 and the crack detection optical system 400 to detect the interface of the wafer W and crack detection, respectively. Used.

The control unit 500 includes a CPU (Central Processing Unit) that controls the operation of each part of the crack detection device 10, a ROM (Read Only Memory) that stores a control program, and an SDRAM (Synchronous Dynamic Random Access Memory) that can be used as a work area for the CPU. Memory). The control unit 500 receives an operation input by an operator via an operation unit 506 (for example, a keyboard and a pointing device such as a mouse and a touch panel), and transmits a control signal corresponding to the operation input to each unit of the crack detection device 10. to control the operation of each part.

The display unit 508 is a device that displays an operation GUI (Graphical User Interface) and images (for example, crack detection results, etc.). As the display unit 508, for example, a liquid crystal display can be used.

(Interface detection optical system)
Next, detection of the interface of the wafer W will be described. In the following description, a case will be described in which the interface of the surface Wa of the wafer W (the surface in contact with the stage 510) is detected, and the crack depth is detected with the interface position of the surface Wa of the wafer W as a reference. In detecting the crack depth, the back surface Wb of the wafer W may be used as a reference, or both the front and back surfaces of the wafer W may be used as a reference to obtain an average value of crack depths detected.

The interface detection optical system 300 is an optical system for detecting the interface (front surface Wa or rear surface Wb) of the wafer W, and includes a half mirror 302, a relay lens 304, a half mirror 306, and a photodetector 308. .

When detecting the interface of the wafer W, the controller 500 irradiates the wafer W with the detection light L1 while the limiting member 106 is retracted from the optical path of the detection light L1. Here, the controller 500 and the interface detection optical system 300 each function as a part of interface detection means.

The half mirror 302 transmits the detection light L1 from the illumination optical system 200 to the condenser lens 504 side, and reflects the reflected light L2 from the wafer W (first reflected light). The reflected light L2 from the wafer W is reflected by the half mirror 302 to bend the optical path and is guided to the relay lens 304 . Reflected light L2 transmitted through relay lens 304 is reflected by half mirror 306 and guided to photodetector 308 .

The photodetector 308 is a device for receiving reflected light L2 from the wafer W to detect the interface of the wafer W, and includes a detector body 308A and a pinhole panel 308B.

As the detector main body 308A, a photodetector (PD, for example, a photodiode) that converts received light into an electrical signal and outputs the electrical signal to the control unit 500 can be used.

A pinhole is formed in the pinhole panel 308B to allow part of the incident light to pass therethrough. The pinhole panel 308B is arranged on the light receiving surface side of the detector main body 308A so that the pinhole is on the optical axis of the reflected light L2.

The interface detection optical system 300 is an optical system in which the position of the pinhole of the pinhole panel 308B and the position of the condensing point of the condensing lens 504 are in an optically conjugate relationship.

The control unit 500 moves the condensing lens 504 and the stage 510 relatively in the Z direction while retracting the limiting member 106 from the optical path of the detection light L1 and irradiating the wafer W with the detection light L1. The control unit 500 detects the reflected light L2 when the detection light L1 is focused on the interface of the wafer W (the front surface Wa or the rear surface Wb), and shifts the Z direction of the interface of the wafer W from the position of the focal point at that time. Calculate the position.

(optical system for crack detection)
Next, detection of the crack K formed inside the wafer W will be described.

Crack detection optical system 400 includes relay lens 402 , half mirror 404 , and photodetectors 406 and 408 .

When detecting a crack K formed inside the wafer W, the controller 500 inserts the limiting member 106 into the optical path of the detection light L1. Here, the control unit 500, the limiting member 106, and the crack detection optical system 400 each function as a part of crack detection means. The limiting member 106 is provided with an opening 106A at a position shifted from the main optical axis AX, and the wafer W is irradiated with the light transmitted through the opening 106A out of the detection light L1. As a result, the wafer W is irradiated with the detection light L1 eccentric with respect to the main optical axis AX.

Reflected light L<b>2 (second reflected light) from wafer W is reflected by half mirror 302 , then sequentially passes through relay lens 304 and half mirror 306 and enters relay lens 402 . Reflected light L2 transmitted through relay lens 402 is received by photodetectors 406 and 408 via half mirror 404 . Here, the transmittance and reflectance of the light incident on the half mirror 404 are assumed to be approximately 50%, respectively.

The photodetectors 406 and 408 are devices for receiving reflected light L2 from the wafer W and detecting cracks K inside the wafer W. FIG. Photodetector 406 includes detector body 406A and pinhole panel 406B, and photodetector 408 includes detector body 408A and pinhole panel 408B.

As the detector main bodies 406A and 408A, photodetectors (for example, photodiodes) that convert received light into electrical signals and output the electrical signals to the control unit 500 can be used.

Pinhole panels 406B and 408B are formed with pinholes for passing a portion of the incident light. Pinhole panels 406B and 408B are arranged on the light receiving surface side of detector bodies 406A and 408A, respectively. The pinhole panels 406B and 408B are arranged such that the pinholes are positioned off the optical axis of the reflected light L2.

FIGS. 2 to 4 are explanatory diagrams showing the state when the wafer W is illuminated with the detection light L1 in polarized light. 2 shows the case where the crack K exists at the condensing point of the condensing lens 504, FIG. 3 shows the case where the crack K does not exist at the condensing point of the condensing lens 504, and FIG. Each of these shows a case where the crack depth (crack bottom position) of the crack K matches. 5 to 7 are diagrams showing states of the reflected light L2 received by the photodetectors 406 and 408, corresponding to the cases shown in FIGS. 2 to 4, respectively. FIG. 8 is a diagram for explaining the path along which the reflected light L2 from the wafer W reaches the condenser lens pupil 504a. Here, the case where the detection light L1 passes through the first region G1 on one side (the right side in FIG. 8) of the condenser lens pupil 504a and the wafer W is subjected to polarized illumination will be described.

As shown in FIG. 2, when there is a crack K at the condensing point of the condenser lens 504, the detection light L1 is totally reflected by the crack K, and the reflected light L2 is detected with respect to the main optical axis AX. It is a component that follows the path on the same side as the optical path of the light L1 and reaches the area on the same side as the detection light L1 of the condenser lens pupil 504a. That is, as shown in FIG. 8, when the detection light L1 from the light source 102 irradiates the wafer W through the condenser lens 504, the path of the detection light L1 is R1. The reflected light L2 that has been totally reflected at , follows the path R2 on the same side (the right side in FIG. 8) with respect to the main optical axis AX as the path R1 of the detection light L1, and passes through the first region G1 of the condenser lens pupil 504a. do.

As shown in FIG. 3, when there is no crack K at the condensing point of the condensing lens 504, the detection light L1 is reflected by the surface Wa of the wafer W, and the reflected light L2 is detected by the condensing lens pupil 504a. It becomes a component that reaches the area on the opposite side of the light L1. That is, as shown in FIG. 8, the reflected light L2 reflected by the surface Wa of the wafer W follows a path R3 on the opposite side (left side in FIG. 8) of the main optical axis AX from the path R1 of the detection light L1. and passes through the second region G2 of the condenser lens pupil 504a.

As shown in FIG. 4, when the condensing point of the condensing lens 504 and the lower end position of the crack K coincide, the detection light L1 is totally reflected by the crack K, and the detection light L1 of the condensing lens pupil 504a and the reflected light component L2a reaching the area on the same side as the non-reflected light component L2a, which is not totally reflected by the crack K and is reflected by the surface Wa of the wafer W and reaches the area opposite to the detection light L1 of the condenser lens pupil 504a. light component L2b. That is, as shown in FIG. 8, of the reflected light L2, the reflected light component L2a totally reflected by the crack K inside the wafer W is on the same side of the main optical axis AX as the path R1 of the detection light L1 ( The non-reflected light component L2b that passes through the first region G1 of the condenser lens pupil 504a along the route R2 (right side of FIG. 8) and is reflected by the surface Wa of the wafer W without being totally reflected by the crack K is detected. The light L1 passes through the second region G2 of the condenser lens pupil 504a following the path R3 on the opposite side (left side in FIG. 8) with respect to the main optical axis AX.

The pinhole panels 406B and 408B are arranged such that the pinholes are optically conjugate with the first region G1 and the second region G2 of the condenser lens pupil 504a, respectively. As a result, the detector main body 406A and the detector main body 408A can selectively receive light that has passed through the first region G1 and the second region G2 of the condenser lens pupil 504a, respectively.

In the example shown in FIG. 2 (when a crack K exists at the condensing point of the condensing lens 504), as shown in FIG. Reflected light L2 is received by 406C, and the level of the detection signal output from light receiving surface 406C becomes higher than the level of the detection signal output from light receiving surface 408C of detector body 408A.

On the other hand, in the example shown in FIG. 3 (when there is no crack K at the condensing point of the condensing lens 504), as shown in FIG. Reflected light is received by the light receiving surface 408C, and the level of the detection signal output from the light receiving surface 408C becomes higher than the level of the detection signal output from the light receiving surface 406C.

Further, in the example shown in FIG. 4 (when the condensing point of the condensing lens 504 coincides with the lower end position of the crack K), as shown in FIG. , and L2b respectively, and the levels of the detection signals output from the light receiving surfaces 406C and 408C become substantially equal.

Thus, the amount of light received by the light receiving surfaces 406C and 408C changes depending on whether or not there is a crack K at the condensing point of the condensing lens 504. FIG. In the present embodiment, using such properties, the crack depth (crack bottom end position or crack top end position) of the crack K formed inside the wafer W can be detected.

Specifically, when the outputs of the detection signals output from the light receiving surfaces 406C and 408C are D1 and D2, respectively, the evaluation value S that indicates the relationship between the condensing point of the condensing lens 504 and the crack depth of the crack K is , can be expressed by the following equation.

S=(D1-D2)/(D1+D2) (1)
In equation (1), when the condition of S=0 is satisfied, that is, when the amounts of light received by the light receiving surfaces 406C and 408C are the same, the condensing point of the condenser lens 504 and the crack bottom end position (or crack top end position) indicates a match.

The control unit 500 controls the focus adjustment mechanism 502 (condensing point changing means) to shift the condensing point of the condenser lens 504 from the interface position Z(0) on the surface Wa to the thickness direction of the wafer W (Z direction). ), the detection signals output from the light-receiving surfaces 406C and 408C are sequentially acquired, the evaluation value S represented by Equation (1) is calculated based on the detection signals, and the evaluation value S is evaluated. Thus, the crack depth of the crack K (crack bottom end position or crack top end position) can be detected.

In this embodiment, photodetectors are used as the detector main bodies 308A, 406A and 408A, but the present invention is not limited to this. For example, an infrared camera or the like may be used instead of the photodetector.

Further, when detecting the crack K, the half mirror 306 may be retracted from the optical path of the reflected light L2. In this case, the half mirror 306 of the interface detection optical system 300 may be replaced with a total reflection mirror, a dichroic mirror, or the like.

Further, in the present embodiment, the transmittance and reflectance of the light incident on the half mirror 404 are set to approximately 50%, respectively, but the present invention is not limited to this. When the transmittance and reflectance of the half mirror 404 are different, in calculating the evaluation value S, the outputs D1 and D2 of the detection signals from the photodetectors 406 and 408 are used according to the transmittance and reflectance of the half mirror 404. may be multiplied by a weighting factor.

In the present embodiment, when performing crack detection, the method of oblique illumination (hereinafter also referred to as illumination method) is switched, the crack depth is detected a plurality of times, and the average value of the detection results of the plurality of times is calculated. Calculated as crack depth. Here, switching the illumination method means switching the eccentricity of the detection light L1 (for example, the distance and position between the opening through which the detection light L1 is emitted and the main optical axis).

Specifically, by rotating the restricting member 106 to move the position of the opening 106A to the position 106B in FIG. 1, the eccentricity of the detection light L1 is changed, and the crack depth is detected twice. . Then, the average value of the two detection results is calculated as the crack depth.

In this embodiment, the restricting member 106 having one opening 106A is rotated, but the present invention is not limited to this. For example, a plurality of openable and closable openings may be provided in the restricting member 106 .

Further, in each of the above-described embodiments, the limiting member 106 is used to block part of the detection light L1 for polarized illumination, but the present invention is not limited to this. For example, polarized illumination may be performed by displacing the light source 102 of the light source unit 100 from the main optical axis AX. In this case, the optical axis of the light source 102 is preferably parallel to the main optical axis AX.

In each of the above-described embodiments, two photodetectors are provided in the crack detection optical system 400, but the present invention is not limited to this. For example, instead of the half mirror 404 and the photodetectors 406 and 408, one split photodetector whose light receiving surface is divided into two may be provided, and the evaluation value S may be calculated from the output of each light receiving surface. Also, a photodetector having a light receiving surface divided into a number corresponding to the type of illumination method may be used.

Also, the configuration for guiding the detection light L1 and the reflected light L2 is merely an example, and is not limited to the above embodiments. For example, without providing the mirror 204, the light source 102, the condenser lens 504, and the stage 510 on which the wafer W is mounted can be arranged in a straight line.

[Optical road surface]
Next, the optical path AR according to this embodiment will be described. In the crack detection device 10 according to the present embodiment, by adjusting the rotation angle of the restricting member 106 (see FIG. 1), the angle _θm of the optical road surface AR with respect to the street width direction D2 (the direction perpendicular to the street direction D1) is It can be changed within the range of 0°<|θ _m |<90°. Here, the limiting member 106, the control unit 500, and the motor M2 are examples of the optical road surface tilting means, and the motor M2 is an example of the limiting member rotating means. In this embodiment, the crack detection step is performed after the step of inclining the optical road surface AR with respect to the street width direction D2.

9 is a plan view showing the optical path AR, and FIG. 10 is a plan view showing an enlarged lens pupil 504A of the condenser lens 504. As shown in FIG. In the drawing, the symbol DP indicates a device pattern, and the symbol ST indicates a street (to-be-cut line) formed between semiconductor devices on the wafer W. As shown in FIG.

As shown in FIG. 9, by adjusting the rotation angle of the limiting member 106, the angle |θ _m | In this way, by inclining the optical surface AR with respect to the street width direction D2, the street width direction generated when the position of the condensing point of the detection light L1 is scanned in the Z direction. It is possible to suppress the deviation of the reflection position to D2.

When |θ _m |≈90°, the optical paths of the detected light L1 and the reflected light L2 overlap with the street direction D1, making measurement difficult. Therefore, |θ _m | is sufficiently smaller than 90°. A value (eg, 80° or less) is preferable.

A method of determining the angle _θm of the optical road surface AR with respect to the street width direction D2 will be described below with reference to FIGS. 9 to 11. FIG.

Assuming that the incident angle of the detection light L1 with respect to the wafer W is θ, as shown in FIGS. The amount of movement ΔY in the Y direction of the position of the light spot is expressed by the following formula (A).

ΔY=ΔZ×tan θ (A)
In FIG. 11, when the detection light L1 scans the scanning range _ZR in the Z direction, the detection light moving distance (moving distance in the direction perpendicular to the main optical axis AX) Lm of the detection light _L1 is expressed by the following formula (B). is represented by

L _m =Z _R ×tan θ (B)
When the street width _Lst is larger than the detection light movement distance Lm ( _Lst > _Lm ), that is, the detection light movement distance _Lm when the detection light L1 _scans the scanning range _ZR is equal to the optical road surface AR. When it fits within the street ST without being tilted (When the detection light L1 is reflected on the wafer W within the range of the street ST when the focal point position of the detection light L1 is scanned in the depth direction of the wafer W) , θ _m =0°.

On the other hand, when the detection light movement distance L _m is equal to or greater than the street width L _st (L _st ≦L _m ), that is, when the detection light movement distance L _m does not fit within the street ST, the detection light movement distance L _m is The light is arranged so as to be within the streets ST (so that the reflection of the detection light L1 on the wafer W occurs within the range of the streets ST when the focal point position of the detection light L1 is scanned in the depth direction of the wafer W). Determine the inclination angle θ _m of the road surface AR. Specifically, when L _m2 =L _m ×cos θ _{m, θ m is} determined so that L _st >L _m2 . At this time, θ _m is represented by the following formulas (C1) and (C2).

cos θ _m <(L _st /L _m ) (C1)
θ _m <arccos(L _st /L _m ) (C2)
By determining the angle θ _m as described above, the influence of the reflectance of the pattern on the signal intensity can be suppressed, as shown in FIG. As a result, the measurement position can be set at a position where the change in reflectance of the pattern is small, and the influence of fine patterns can be suppressed.

According to the present embodiment, by inclining the optical road surface AR defined by the detection light L1 and the reflected light L2 with respect to the street width direction D2 when crack detection is performed on the wafer W, the pattern can sufficiently remove the influence of the reflectance of , and it becomes possible to detect the crack depth with high accuracy.

[Second embodiment]
Next, a second embodiment of the invention will be described with reference to FIG. In the following description, the same reference numerals are given to the same configurations as in the first embodiment, and the description thereof is omitted.

This embodiment differs from the first embodiment in the optical road surface tilting means for tilting the optical road surface AR with respect to the street width direction D2.

Specifically, as shown in FIG. 13, the crack detection device 10A according to this embodiment includes a rotation mechanism 512 for rotating the stage 510 around the main optical axis (Z-axis). By rotating the stage 510 using this rotating mechanism 512, the angle _θm of the optical surface AR with respect to the street width direction D2 can be changed within the range of 0°<| _θm |<90°. Here, the control unit 500 and the rotating mechanism 512 are an example of the optical road surface tilting means, and the rotating mechanism 512 is an example of the stage rotating means.

Also in this embodiment, as in the first embodiment, by inclining the optical road surface AR with respect to the street width direction D2, the influence of the reflectance of the pattern can be sufficiently removed, and the crack depth can be reduced. Accurate detection becomes possible.

It is also possible to combine the optical road surface inclination means of the first embodiment and the second embodiment.

DESCRIPTION OF SYMBOLS 10, 10A... Crack detection apparatus, 100... Light source part, 102... Light source, 104... Collimate lens, 106... Limiting member, 200... Illumination optical system, 202... Relay lens, 204... Mirror, 206... Relay lens, 300... Interface Detection optical system 302 Half mirror 304 Relay lens 306 Half mirror 308 Photo detector 400 Crack detection optical system 402 Relay lens 404 Half mirror 406, 408 Photo detection Device 500 Control unit 502 Focus adjustment mechanism 504 Collecting lens 506 Operation unit 508 Display unit 510 Stage 512 Rotation mechanism M1, M2 Motor

Claims (5)

A crack detection device for detecting a crack depth of a crack formed along a scheduled cutting line of a street between semiconductor devices on a wafer,
a crack detection means for illuminating the wafer obliquely with detection light from a position off-center from the main optical axis and detecting the crack depth of the crack based on the reflected light from the wafer;
an optical road surface tilting means for tilting an optical road surface determined by the optical paths of the detected light and the reflected light with respect to the width direction of the street;
A crack detection device comprising: The optical road surface inclination means is arranged to tilt the width of the street so that the detection light is reflected on the wafer within the range of the street when the detection light is scanned in the depth direction of the wafer. 2. The crack detector of claim 1, wherein the optical path is tilted. a restricting member having an opening at a position eccentric from the main optical axis, blocking part of the light emitted from the light source unit with the opening and emitting it as the detection light;
3. The optical road surface tilting means according to claim 1, wherein said optical road surface tilting means includes limiting member rotating means for tilting said optical road surface with respect to the width direction of said street by rotating said limiting member about said main optical axis. Crack detector. A stage on which the wafer is placed,
4. The optical road surface tilting means includes stage rotating means for tilting the optical road surface with respect to the width direction of the street by rotating the stage around the main optical axis. The crack detection device according to . A crack detection method for detecting a crack depth of a crack formed along a scheduled cutting line of a street between semiconductor devices on a wafer, comprising:
a step of tilting, with respect to the width direction of the street, an optical path determined by detection light obliquely illuminating the wafer from a position off-center from the main optical axis and an optical path of reflected light from the wafer; ,
a step of obliquely illuminating the wafer with the detection light in a state in which the optical surface is tilted with respect to the width direction of the street, and detecting the crack depth of the crack based on the reflected light from the wafer;
A crack detection method comprising:

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