TW202235195A - Observation device and observation method performing the moving of the condensing position at high speed even if imaging region is larger - Google Patents

Abstract

The laser processing device of this invention is provided with: an imaging unit having a light source, an objective lens, and a light detection unit; a driving unit that moves the imaging unit in a Z direction taken as upper and lower directions; an actuator that moves the objective lens in the Z direction; and a control unit that performs: a first control controlling the driving unit so that the imaging unit to a position where the rear surface becomes a condensing position; and a second control for, after the first control, controlling the actuator such that the objective lens moves to a position as a first region between the rear surface and the front surface that becomes a condensing position, and controlling the actuator such that the objective lens moves to a position as a second region, which is a region that enables the opposite side to be relative to the rear surface, becoming a condensing position.

Description

Observation device and observation method

One aspect of the present invention relates to an observation device and an observation method.

There is known a laser processing apparatus that irradiates laser light from one side of the semiconductor substrate to the wafer in order to cut a wafer including a semiconductor substrate and a functional element layer formed on the semiconductor substrate along a plurality of lines. Multiple rows of modified regions are formed inside the semiconductor substrate along multiple lines, respectively. The laser processing apparatus described in Japanese Patent Application Laid-Open No. 2017-64746 includes an imaging unit (for example, an infrared camera) capable of observing the modified region formed inside the semiconductor substrate and the processing formed on the functional element layer from one side of the semiconductor substrate. damage etc.

In the case of observing information related to the modified region (for example, cracks extending from the modified region) in the above-mentioned laser processing apparatus, for example, for The front end of the crack extending from the surface on the opposite side) cannot be detected by using the front end as a focal point, but can be detected by using a point symmetrical to the front end with respect to the other surface as a focal point. . In this way, even a point that is symmetrical with respect to another plane needs to be a focus point, etc., and the imaging area becomes larger. Usually, the photographing unit is moved in the vertical direction (Z direction) by a control unit that moves the entire photographing unit. However, when the photographing area is large, the focus position cannot be moved at a sufficiently high speed. The time required to move the spotlight position is longer than the shooting speed, and the drop in shooting tact becomes a problem. Also, if the focusing position is moved at high speed, since the entire imaging unit is moved at high speed, it is difficult for the vibration to subside after the movement, and imaging cannot be performed until the vibration subsides. As a result, the imaging tact is reduced.

One aspect of the present invention has been made in view of the above circumstances, and relates to an observation device and an observation method capable of improving the tact time.

An observation device according to one aspect of the present invention is an observation device for observing a wafer having a first surface and a second surface and having a modified region formed inside by irradiating laser light from the first surface side, and is characterized by comprising: : An imaging unit that includes a light source that outputs light that is transparent to the wafer, a condensing lens that condenses the light output from the light source on the condensing position of the wafer, and a light detection unit that detects the light propagating through the wafer a drive unit that supports the photographing unit and moves the photographing unit in the Z direction as an up-down direction; an actuator that is arranged on the condenser lens and moves the condenser lens in the Z direction; and a control unit, the control unit implements: the first One control is to control the driving unit so that the photographing part moves to the position where the second surface becomes the light-condensing position; and the second control is to move the condensing lens to make the second surface and the first surface after the first control. The actuator is controlled in such a way that at least a part of the first area, which is the area between the surfaces, becomes the position of the condensing position, and the condensing lens is moved to the second surface, which is the area on the opposite side of the first surface with respect to the second surface. The actuator is controlled so that at least a part of the area becomes the light-collecting position.

In the observation apparatus according to one aspect of the present invention, in the observation of the wafer on which the modified region is formed, the driving unit that moves the imaging unit in the Z direction is controlled so that the imaging unit moves to the second surface of the wafer. (Back side) becomes the position of the condensing position, and then controls the actuator that moves the condensing lens in the Z direction to move the condensing lens to the area between the second surface and the first surface, that is, the first area becomes position of the condensing position, and the condensing lens is moved to a position where the second area, which is an area on the opposite side of the first surface with respect to the second surface, becomes the condensing position. In this way, by moving the condensing lens so that both the first region and the second region become light-condensing positions, it is possible to appropriately perform cracks from the modified region when the first region is the light-condensing position. Both of direct observation of the light, etc., and observation of cracks and the like in the case of making the second region the light-collecting position by reflection from the back surface (second surface). Furthermore, the movement of the condensing lens that makes the first region and the second region the condensing position is performed by an actuator that moves only the condensing lens of the photographing unit, for example, compared with the case where the entire photographing unit is moved. In this way, the focusing position can be moved at high speed, and vibration after the movement can also be suppressed. Here, an observation device according to one aspect of the present invention includes a drive unit that moves the entire imaging unit in the Z direction, and an actuator that moves the condenser lens of the imaging unit in the Z direction. By arranging both the drive unit and the actuator in this way, for example, rough alignment can be performed by the drive unit, and detailed alignment can be performed by the actuator, etc., and the device cost can be suppressed, and the pursuit of precision can be performed with high precision. Alignment (focus positioning of the shooting range, etc.). In an observation device according to one aspect of the present invention, firstly, the imaging unit is controlled by the driving unit so that the second surface, which is the boundary surface between the first region and the second region, becomes the light-collecting position, and then the second surface The condenser lens is controlled by an actuator in such a manner that the first area and the second area respectively serve as light-condensing positions. Before the control by the actuator starts, the movable range of the actuator can be utilized to the maximum extent by aligning the light-collecting position with the second surface (the boundary surface between the first region and the second region). High-speed movement of the condensing lens is carried out so that the first area and the second area are condensing positions. As described above, according to one aspect of the observation apparatus of the present invention, it is possible to move the focus position at high speed, and to improve the imaging tact.

Before the first control, the control unit may further perform prior control of controlling the actuator so as to fix the actuator at the center position of the movable range of the actuator in the Z direction. Accordingly, the second control can be performed in a state where the actuator is sufficiently movable in two directions (up and down) in the Z direction, and the movable range of the actuator can be utilized to the maximum, and the first region and the first region can be appropriately adjusted. The second area is the high-speed movement of the condensing lens at the condensing position.

In the second control, the control unit may execute the third control of controlling the actuator so that the position of the condensing lens moves in the Z direction in a state where the area near the second surface becomes the condensing position, and based on this state The detailed position of the second surface is specified by the light detection result of the lower photodetection unit, and the condenser lens is controlled to move to a position where the specified detailed position of the second surface becomes the light-condensing position, that is, a reference position. Actuator; And the 4th control, make the condensing lens move to the mode control actuator that makes at least a part of the first area become the condensing position from the reference position, and make the condensing lens move from the reference position to The actuator is controlled so that at least a part of the second area becomes the light-collecting position. Even with the first control, for example, when the actual thickness of the wafer is different from the assumption, it is considered that the focused position deviates from the second surface. In this case, there is a problem that imaging of the first region and the second region which make full use of the above-mentioned movable range of the actuator cannot be realized. Regarding this point, in the second control, the detailed position of the second surface is specified based on the detection result of light as a reference position (third control), and the condenser lens is moved from the reference position to the first position by the actuator. area and the imaging range of the second area (fourth control), so that even if the focus position deviates from the second surface in the first control, the reference position can be set appropriately to realize the maximum utilization Photography of the first area and the second area of the movable range of the actuator.

In the second control, the control unit may execute the third control of controlling the actuator so that the position of the condensing lens moves in the Z direction in a state where the area near the second surface becomes the condensing position, and based on this state The detailed position of the second surface is identified by the light detection result of the lower photodetection unit, and the condensing lens is moved to the reference position which is the position of the condensing lens at which the specified detailed position of the second surface becomes the condensing position. The actuator is controlled in the same manner, and the fifth control is also carried out, so that the imaging unit moves to the first area or the area within the second area and is not used as the focus when the detailed position of the second surface is specified in the third control. The area of the light position, that is, at least a part of the unphotographed area, is controlled to be the position of the condensing position; and the sixth control is to use the position of the condensing lens of the imaging unit after the fifth control as a new reference position, so that The actuator is controlled so that the condensing lens moves to a position where the area included in the unphotographed area becomes the condensing position. According to the third control, the vicinity of the second surface can be photographed while specifying the detailed position of the second surface. Therefore, in this observation device, the drive unit is controlled so that the imaging unit moves to a position where the unimagined area that is not imaged in the third control becomes the focus position (fifth control), so that the imaging unit after the fifth control The position of the condensing lens becomes the new reference position, and the actuator is controlled so that the condensing lens moves to a position where the unphotographed area becomes the condensing position (sixth control). According to such a configuration, since the control is performed so that the area not captured by the third control becomes the focus position, it is possible to perform imaging more efficiently without performing useless imaging. In addition, according to such a configuration, even when the area to be imaged is not within the movable range of the actuator at the initial reference position, the area to be imaged can be reliably imaged by changing the reference position. photography.

One type of observation method of the present invention is an observation method for observing a wafer having a first surface and a second surface and having a modified region formed inside by irradiating laser light from the side of the first surface, comprising: : a first step of moving the photographing unit to a position where the second surface becomes the light-focusing position by a drive unit that moves the photographing unit in the Z direction that is the up-and-down direction; The actuator that moves the lens in the Z direction moves the condensing lens to a position where at least a part of the first region, which is a region between the second surface and the first surface, becomes a condensing position, and moves the condensing lens to a position where A second step in which at least a part of the second region, which is a region on the opposite side of the first surface to the second surface, becomes the light-collecting position. According to the observation method of one aspect of the present invention, it is possible to move the focus position at high speed, and to improve the tact time of photography.

The observation method described above may further include, prior to the first step, a pre-step of controlling the actuator so that the actuator is fixed at the center of the movable range of the actuator in the Z direction. According to such a configuration, the movable range of the actuator can be utilized to the maximum, and the high-speed movement of the condensing lens that makes the first region and the second region the condensing positions can be appropriately performed.

According to one aspect of the present invention, even in the case of a large imaging area, it is possible to move the focus position at high speed, and to improve the imaging tact.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the same reference numerals are assigned to the same or corresponding parts in each figure, and overlapping explanations are omitted. [Structure of laser processing device]

As shown in FIG. 1 , the laser processing apparatus 1 includes a mounting table 2 , a laser irradiation unit 3 , a plurality of imaging units 4 , 5 , and 6 , a drive unit 7 , a control unit 8 , and a display 150 . The laser processing apparatus 1 is an apparatus for forming a modified region 12 on an object 11 by irradiating the object 11 with laser light L. In addition, the laser processing apparatus 1 is an observation apparatus for observing the object 11 (wafer 20 described later) on which the modified region 12 is formed.

The stage 2 supports the object 11 by, for example, a film adhered to the object 11 by suction. The mounting table 2 is movable along the X direction and the Y direction, and is rotatable around an axis parallel to the Z direction as a center line. Among them, the X direction and the Y direction are the first horizontal direction and the second horizontal direction perpendicular to each other, and the Z direction is the vertical direction.

The laser irradiation unit 3 condenses the laser light L having transmittance to the object 11 to irradiate the object 11 . When the laser light L is condensed to the inside of the object 11 supported by the stage 2, the laser light L is particularly absorbed at the part corresponding to the condensing point C of the laser light L, and a laser light L can be formed inside the object 11. Modified area 12.

The modified region 12 is a region that differs in density, refractive index, mechanical strength, or other physical properties from the surrounding non-modified region. As the modified region 12, there are, for example, a melt-processed region, a crack region, a dielectric breakdown region, a refractive index change region, and the like. The modified region 12 has a characteristic that cracks easily extend from the modified region 12 to the incident side of the laser light L and the opposite side. Such properties of the modified region 12 are utilized for cutting the object 11 .

As an example, when the stage 2 is moved in the X direction and the focused point C is relatively moved in the X direction with respect to the object 11, a plurality of modified spots are formed in a row along the X direction. 12s. One modified spot 12s is formed by irradiating one pulse of laser light L. One row of modified regions 12 is a collection of a plurality of modified spots 12s arranged in one row. Adjacent modified spots 12s may be connected to each other or may be separated from each other depending on the relative movement speed of the focused spot C with respect to the object 11 and the repetition frequency of the laser light L.

The imaging unit 4 images the modified region 12 formed in the object 11 and the tip of the crack extending from the modified region 12 .

The photographing unit 5 and the photographing unit 6 photograph the object 11 supported by the mounting table 2 by using the light transmitted through the object 11 under the control of the control unit 8 . Images captured by the imaging units 5 and 6 are used, for example, to calibrate the irradiation position of the laser beam L. FIG.

The driving unit 7 supports the laser irradiation unit 3 and the plurality of imaging units 4 , 5 , 6 . The driving unit 7 moves the laser irradiation unit 3 and the plurality of imaging units 4, 5, 6 in the Z direction.

The control unit 8 controls the operations of the mounting table 2 , the laser irradiation unit 3 , the plurality of imaging units 4 , 5 , and 6 , and the driving unit 7 . The control unit 8 is configured as a computer device including a processor, a memory, a storage unit, a communication device, and the like. In the control unit 8, the processor executes software (program) read from the memory or the like, and controls reading or writing of data in the memory and the storage unit, and communication by the communication device.

The display 150 has a function as an input unit that accepts input of information from a user, and a function as a display unit that displays information to the user.

[structure of object] The object 11 of this embodiment is a wafer 20 as shown in FIGS. 2 and 3 . The wafer 20 includes a semiconductor substrate 21 and a functional element layer 22 . In this embodiment, it is described that the wafer 20 has the functional element layer 22 , but the wafer 20 may either have the functional element layer 22 or not have the functional element layer 22 , or may be a bare wafer. The semiconductor substrate 21 has a back surface 21a (second surface) and a surface 21b (first surface). The semiconductor substrate 21 is, for example, a silicon substrate. The functional element layer 22 is formed on the back surface 21 a of the semiconductor substrate 21 . The functional element layer 22 includes a plurality of functional elements 22a arranged two-dimensionally along the rear surface 21a. The functional element 22a is, for example, a light receiving element such as a photodiode, a light emitting element such as a laser diode, or a circuit element such as a memory. The functional element 22a may also be formed three-dimensionally by stacking a plurality of layers. In addition, although the notch 21c showing the crystal orientation is provided in the semiconductor substrate 21, an orientation flat may be provided instead of the notch 21c.

The wafer 20 is cut along the plurality of lines 15 for each functional element 22a. The plurality of lines 15 pass between each of the plurality of functional elements 22 a when viewed from the thickness direction of the wafer 20 . More specifically, the line 15 passes through the center of the ruled line region 23 (the center in the width direction) when viewed from the thickness direction of the wafer 20 . The ruled line region 23 extends in the functional element layer 22 so as to pass between adjacent functional elements 22a. In the present embodiment, a plurality of functional elements 22a are arranged in a matrix along the back surface 21a, and a plurality of lines 15 are set in a grid. In addition, although the line 15 is an imaginary line, it may be an actually drawn line.

[Structure of laser irradiation unit] As shown in FIG. 4 , the laser irradiation unit 3 has a light source 31 , a spatial light modulator 32 and a condenser lens 33 . The light source 31 outputs laser light L by, for example, pulse oscillation. The spatial light modulator 32 modulates the laser light L output from the light source 31 . The spatial light modulator 32 is, for example, a reflective liquid crystal (LCOS: Liquid Crystal on Silicon) spatial light modulator (SLM: Spatial Light Modulator). The condensing lens 33 condenses the laser light L modulated by the spatial light modulator 32 . Wherein, the condenser lens 33 may also be a correction ring lens.

In this embodiment, the laser irradiation unit 3 irradiates the laser light L to the wafer 20 from the surface 21 b side of the semiconductor substrate 21 along the plurality of lines 15 , thereby forming a laser beam L inside the semiconductor substrate 21 along the plurality of lines 15 . 2 rows of modified regions 12a, 12b. The modified region 12a is the modified region closest to the back surface 21a among the two rows of modified regions 12a and 12b. The modified region 12b is the modified region closest to the modified region 12a among the two rows of modified regions 12a and 12b, and is the modified region closest to the surface 21b.

The two rows of modified regions 12 a and 12 b are adjacent to each other in the thickness direction (Z direction) of the wafer 20 . The two rows of modified regions 12 a and 12 b are formed by relatively moving the two light-converging points C1 and C2 along the line 15 with respect to the semiconductor substrate 21 . The laser light L is modulated by the spatial light modulator 32 , so that, for example, the focal point C2 is located on the rear side of the traveling direction and on the incident side of the laser light L relative to the focal point C1 . Here, regarding the formation of the modified region, it may be single focus or multi focus, and may be one path or multiple paths.

The laser irradiation unit 3 irradiates the wafer 20 with laser light L along each of the plurality of lines 15 from the surface 21 b side of the semiconductor substrate 21 . As an example, with respect to the semiconductor substrate 21 which is a single-crystal silicon <100> substrate with a thickness of 400 μm, the two focusing points C1 and C2 are respectively focused on a position 54 μm away from the back surface 21 a and a position 128 μm away from the back surface 21 a, and along a plurality of lines Each line 15 of 15 irradiates laser light L to the wafer 20 from the surface 21 b side of the semiconductor substrate 21 . At this time, for example, under the condition that the cracks 14 throughout the two rows of modified regions 12a, 12b reach the back surface 21a of the semiconductor substrate 21, the wavelength of the laser light L is 1099nm, the pulse width is 700n seconds, and the repetition frequency is 120kHz. In addition, the output of the laser light L at the converging point C1 is 2.7 W, the output of the laser light L at the converging point C2 is 2.7 W, and the relative movement speed of the two converging points C1 and C2 with respect to the semiconductor substrate 21 is 800mm/sec. Wherein, for example, when the number of processing passes is 5, for the above-mentioned wafer 20, for example, ZH80 (position 328 μm away from the back surface 21a), ZH69 (position 283 μm away from the back surface 21a), ZH57 (position 283 μm away from the back surface 21a), ZH57 (position 283 μm away from the back surface 21a at a distance of 234 μm), ZH26 (a position at a distance of 107 μm from the back surface 21a), and ZH12 (a position at a distance of 49.2 μm from the back surface 21a) are processing positions. In this case, for example, the laser light L may have a wavelength of 1080 nm, a pulse width of 400 nsec, a repetition frequency of 100 kHz, and a moving speed of 490 mm/sec.

Formation of such two rows of modified regions 12a, 12b and fissures 14 is carried out as follows. That is, in subsequent steps, for example, by grinding the surface 21b of the semiconductor substrate 21, the semiconductor substrate 21 is thinned, and the cracks 14 are exposed to the surface 21b, and the wafer 20 is cut along the plurality of lines 15 into The case of multiple semiconductor components.

[Structure of the imaging unit for inspection] As shown in FIG. 5 , the imaging unit 4 (imaging unit) has a light source 41 , a reflection mirror 42 , an objective lens 43 (condensing lens), and a photodetection unit 44 . The photographing unit 4 photographs the wafer 20 . Here, only the outline of the imaging unit 4 will be described, and the more detailed configuration of the imaging unit 4 (specifically, the configuration of the objective lens 43 on which the actuator 70 (see FIG. 13 ) is mounted) will be described later. The light source 41 outputs transmissive light I1 to the semiconductor substrate 21 of the wafer 20 . The light source 41 is composed of, for example, a halogen lamp and a filter, and outputs light I1 in the near-infrared region. The light I1 output from the light source 41 is reflected by the mirror 42 , passes through the objective lens 43 , and is irradiated from the surface 21 b side of the semiconductor substrate 21 to the wafer 20 . The objective lens 43 functions as a condensing lens that condenses the light I1 output from the light source 41 to a condensing position on the wafer 20 . At this time, the stage 2 supports the wafer 20 on which the two rows of modified regions 12 a and 12 b are formed as described above.

The objective lens 43 passes the light I1 reflected by the back surface 21 a of the semiconductor substrate 21 . That is, the objective lens 43 passes the light I1 propagating through the semiconductor substrate 21 . The numerical aperture (NA) of the objective lens 43 is 0.45 or more, for example. The objective lens 43 has a correction ring 43a. The correction ring 43 a corrects the aberration generated by the light I1 in the semiconductor substrate 21 by, for example, adjusting the distance between a plurality of lenses constituting the objective lens 43 . Here, the means for correcting aberrations is not limited to the correction ring 43a, and other correction means such as a spatial light modulator may also be used. The light detection unit 44 detects the light I1 transmitted through the objective lens 43 and the reflection mirror 42 (that is, light propagating through the wafer 20 ). The photodetector 44 is composed of, for example, an InGaAs camera, and detects the light I1 in the near-infrared region. However, the means for detecting (imaging) the light I1 in the near-infrared region is not limited to an InGaAs camera, and other imaging means that perform transmission-type imaging such as a transmission confocal microscope may be used.

The photographing unit 4 can photograph each of the two rows of modified regions 12a, 12b and the front ends of each of the plurality of cracks 14a, 14b, 14c, and 14d (details will be described later). The crack 14a is a crack extending from the modified region 12a toward the rear surface 21a. The crack 14b is a crack extending from the modified region 12a to the surface 21b side. The crack 14c is a crack extending from the modified region 12b to the rear surface 21a side. The crack 14d is a crack extending from the modified region 12b to the surface 21b side.

[Structure of Imaging Unit for Alignment Correction] As shown in FIG. 6 , the imaging unit 5 has a light source 51 , a mirror 52 , a lens 53 , and a photodetector 54 . The light source 51 outputs light I2 that is transparent to the semiconductor substrate 21 of the wafer 20 . The light source 51 is composed of, for example, a halogen lamp and a filter, and outputs light I2 in the near-infrared region. The light source 51 may be shared with the light source 41 of the imaging unit 4 . The light I2 output from the light source 51 is reflected by the mirror 52 , passes through the lens 53 , and is irradiated onto the wafer 20 from the front surface 21 b side of the semiconductor substrate 21 .

The lens 53 passes the light I2 reflected by the back surface 21 a of the semiconductor substrate 21 . That is, the lens 53 passes the light I2 propagating through the semiconductor substrate 21 . The numerical aperture of the lens 53 is 0.3 or less. That is, the numerical aperture of the objective lens 43 of the imaging unit 4 is larger than the numerical aperture of the lens 53 . The light detection unit 54 detects the light I2 passing through the lens 53 and the reflection mirror 52 . The photodetector 54 is composed of, for example, an InGaAs camera, and detects the light I2 in the near-infrared region.

Under the control of the control unit 8 , the imaging unit 5 irradiates the wafer 20 with light I2 from the front surface 21b side, and detects the light I2 returning from the back surface 21a (functional element layer 22 ), thereby imaging the functional element layer 22 . Also, under the control of the control unit 8, the imaging unit 5 irradiates the wafer 20 with light I2 from the surface 21b side, and detects the light I2 returning from the positions where the modified regions 12a, 12b are formed on the semiconductor substrate 21, whereby An image of a region including the modified regions 12a and 12b is acquired. These images are used to calibrate the irradiation position of the laser beam L. FIG. The imaging unit 6 has the same structure as the imaging unit 5 except that it has a lower magnification than the lens 53 (for example, 6 times in the imaging unit 5 and 1.5 times in the imaging unit 6), and has the same structure as the imaging unit 5. 5 is also used for calibration.

[Photographing principle of the camera unit for inspection] Using the imaging unit 4 shown in FIG. 5, as shown in FIG. 7, for the semiconductor substrate 21 where the crack 14 straddling the two rows of modified regions 12a, 12b has reached the back surface 21a, the focal point F (the focal point of the objective lens 43) is moved from the surface to the semiconductor substrate 21. The 21b side moves toward the back 21a side. In this case, when the focal point F is focused on the front end 14e of the crack 14 extending from the modified region 12b to the surface 21b side from the surface 21b side, the front end 14e can be confirmed (image on the right side of FIG. 7 ). Hereinafter, the method of focusing the focal point F on the front end 14e of the crack 14 to observe the front end 14e may be referred to as direct observation. However, even if the focal point F is focused on the fissure 14 itself and the tip 14e of the fissure 14 reaching the back surface 21a from the front surface 21b side, it cannot be confirmed (the image on the left side of FIG. 7 ). In addition, when the focal point F is focused on the back surface 21 a of the semiconductor substrate 21 from the front surface 21 b side, the functional element layer 22 can be confirmed.

And, using the imaging unit 4 shown in FIG. 5, as shown in FIG. 8, for the semiconductor substrate 21 in which the crack 14 straddling the two rows of modified regions 12a, 12b has not reached the back surface 21a, the focal point F is set from the front surface 21b side to the back surface. 21a moves sideways. In this case, even if the focal point F is focused on the front end 14e of the crack 14 extending from the modified region 12a to the rear surface 21a side from the front surface 21b side, the front end 14e cannot be confirmed (the left image in FIG. 8 ). However, if the focal point F is focused from the surface 21b side to a region on the opposite side to the surface 21b with respect to the back surface 21a (that is, a region located on the functional element layer 22 side with respect to the back surface 21a), the focus F is symmetrical with respect to the back surface 21a. If the virtual focal point Fv is located at the front end 14e, the front end 14e can be confirmed by the reflected light of the back surface 21a (the image on the right side of FIG. 8 ). In addition, the virtual focal point Fv is a point symmetrical to the focal point F with respect to the rear surface 21 a in consideration of the refractive index of the semiconductor substrate 21 . Hereinafter, the method of focusing the focal point F on the area on the opposite side of the front surface 21b to the back surface 21a and observing the tip 14e by back reflection may be referred to as back reflection observation.

It is presumed that the crack 14 cannot be confirmed as described above because the width of the crack 14 is smaller than the wavelength of the light I1 which is the illumination light. 9 and 10 are SEM (Scanning Electron Microscope) images of modified regions 12 and cracks 14 formed inside semiconductor substrate 21 which is a silicon substrate. (b) of FIG. 9 is an enlarged image of the region A1 shown in (a) of FIG. 9 , (a) of FIG. 10 is an enlarged image of the region A2 shown in (b) of FIG. 9 , and ( b) is an enlarged image of the area A3 shown in (a) of FIG. 10 . Thus, the width of the fissure 14 is about 120 nm, which is smaller than the wavelength (for example, 1.1 to 1.2 μm) of the light I1 in the near-infrared region.

The principle of photography conceived from the above matters is as follows. As shown in (a) of FIG. 11 , since the light I1 does not return when the focal point F is placed in the air, a pitch-black image (image on the right side of (a) of FIG. 11 ) is obtained. As shown in (b) of FIG. 11 , if the focal point F is located inside the semiconductor substrate 21, the light I1 reflected by the back surface 21a will return, so a clean image (the figure on the right side of (b) of FIG. 11 ) will be obtained. picture). As shown in (c) of FIG. 11 , if the focal point F is focused on the modified region 12 from the surface 21b side, the modified region 12 will absorb, scatter, etc. Therefore, an image (image on the right side of (c) of FIG. 11 ) showing the jet-black modified region 12 against a clean background is obtained.

As shown in (a) and (b) of FIG. 12, if the focal point F is focused on the front end 14e of the crack 14 from the surface 21b side, for example, due to optical specificity (stress concentration, distortion) generated near the front end 14e, , discontinuity of atomic density, etc.), the light is confined near the front end 14e, etc., causing scattering, reflection, interference, absorption, etc., to a part of the light I1 that is reflected and returned by the back surface 21a, so it will be displayed in a white background An image of the jet-black front end 14e (images on the right side of (a) and (b) of FIG. 12 ) is obtained. As shown in (c) of FIG. 12, if the focal point F is focused from the surface 21b side to a part other than the vicinity of the front end 14e of the crack 14, at least a part of the light I1 reflected by the back surface 21a will return, so a clean image will be obtained. image (the image on the right side of (c) in FIG. 12 ).

[Structure of the objective lens equipped with the actuator] Hereinafter, the actuator-mounted objective lens 43 included in the imaging unit 4 will be described with reference to FIGS. 13 and 14 . FIG. 13 is a configuration diagram of the objective lens 43 on which the actuator 70 is mounted.

As shown in FIG. 13 , the imaging unit 4 includes an actuator 70 in addition to the respective structures shown in FIG. 5 . The actuator 70 is provided (attached) to the objective lens 43, and is an actuator which moves the objective lens 43 in Z direction which is an up-down direction. The actuator 70 is configured to be movable in the Z direction, and moves the objective lens 43 in the Z direction by moving in the Z direction. The required movable range of the actuator 70 is determined according to the width of the imaging area, for example. The movable range of the actuator 70 is set so that, for example, the front end of the crack 14 extending from the modified region 12 is photographed in a state where the imaging unit 4 is fixed at a predetermined position by the driving unit 7 (details will be described later).

Now, as shown in FIG. 13, two modified regions 12a, 12b are formed inside the wafer 20, and cracks extend from the two modified regions 12a, 12b to the front 21b side and the back 21a side of the wafer 20. 14. In the example shown in FIG. 13 , the crack 14 does not reach the front surface 21 b and the back surface 21 a of the wafer 20 . In such a case, in order to properly photograph the tip of the crack 14 extending from the modified region 12, it is necessary to be able to directly observe the tip of the crack 14 on the surface 21b side extending from the modified region 12b on the surface 21b side. The front end on the surface 21b side of the crack 14 is the light-collecting position), and the focus can be focused on a point on the opposite side of the front end on the surface 21b side of the crack 14 with respect to the back surface 21a for back reflection observation (can be made The point on the opposite side is the spotlight position). In this case, the required movable range of the actuator 70 becomes the "ACT movable range" shown in FIG. 13 .

In addition, the modified region 12 and the like are formed so that the crack 14 of the wafer 20 reaches the surface 21b and the back surface 21a, that is, the fully cut state, and at least the modified region 12 is formed so that the crack 14 reaches the surface 21b. In this case, as shown in FIG. 14, in order to properly photograph the tip of the crack 14 extending from the modified region 12, it is necessary to be able to directly observe the modification from the outermost surface 21b side in the modified regions 12a, 12b, 12c, and 12d. The front end of the surface 21b side of the fissure 14 extending from the qualitative region 12d (the surface 21b can be used as a light-collecting position), and the focus can be focused on a point on the opposite side of the surface 21b with respect to the back surface 21a for back reflection observation (can be made Let the point on the opposite side be the spotlight position). In this case, the required movable range of the actuator 70 becomes the "ACT movable range" shown in FIG. 14 . For example, when the wafer 20 made of a silicon substrate has a thickness of 400 μm and the wafer 20 is fully cut, the imaging range in the silicon becomes 400 μm+400 μm=800 μm (including the front surface 21 b relative to the back surface 21 a area on the opposite side). In this case, it is preferable to set the movable range of the actuator 70 in air to about 100 μm+100 μm=200 μm in consideration of the difference in refractive index.

[Photography Control Using Drive Unit and Actuator] Hereinafter, imaging control performed by the imaging unit 4 using the drive unit 7 (see FIG. 1 ) and the actuator 70 will be described with reference to FIGS. 15 to 18 . In the laser processing apparatus 1, the drive unit 7 and the actuator 70 are controlled by the control unit 8 (refer to FIG. 1 ), and the inside of the wafer 20 is scanned by the imaging unit 4 while moving the focusing position of the imaging unit 4. photography. In such imaging control, the drive unit 7 performs rough alignment of the focusing position related to imaging, and the actuator 70 performs detailed alignment of the focusing position related to imaging. The driving unit 7 is a structure that supports the entire imaging unit 4 and moves the entire imaging unit 4 in the Z direction. The actuator 70 is attached to the objective lens 43 in the imaging unit 4 and is configured to move the objective lens 43 in the Z direction.

FIG. 15 is a diagram illustrating an overview of movement of the light-converging position using the drive unit 7 and the actuator 70 . The control unit 8 executes the first control (refer to FIG. 15 (a)) to control the drive unit 7 so that the imaging unit 4 moves to a position where the back surface 21a becomes the light-collecting position, and after the first control, the objective lens 43 to move to the position between the surface 21b and the back surface 21a, that is, at least a part of the first region 28, to control the actuator 70 (see (b) of FIG. 15 ) and move the objective lens 43 The second control of the actuator 70 is controlled so that at least a part of the second region 29 , which is a region on the opposite side of the front surface 21b from the rear surface 21a, becomes a light-collecting position (see FIG. 15( c )). In addition, the back surface 21a may serve as the light-collecting position including the vicinity of the back surface 21a (for example, a region within a range of ±10 μm from the back surface 21a ) may be the light-collecting position.

Furthermore, the control unit 8 executes prior control of the actuator 70 so that the actuator 70 is fixed at the center position (fixed center) of the movable range of the actuator 70 in the Z direction before the first control. The center position of the movable range only needs to be near the center position of the movable range, for example, when the movable range of the actuator 70 is 80 μm, it may be a position of 40 μm±10 μm.

In the first control, as shown in (a) of FIG. 15 , the drive unit 7 moves the entire imaging unit 4 so that the focusing position becomes the rear surface 21 a under the control of the control unit 8 . That is, the Z axis falls to the vicinity of the back surface 21a. As described above, the actuator 70 is centered in the Z direction. Since the first area 28 and the second area 29 as the imaging area are symmetrical to each other with respect to the rear surface 21a (that is, the rear surface 21a is the center of the imaging area in the Z direction), light is collected in a state where the actuator 70 is centered. The state where the position is the back surface 21 a can be said to be the state where the photographable area is maximized by the operation of the actuator 70 .

In the second control, as shown in (b) of FIG. 15 , first, the actuator 70 moves only the objective lens 43 so that the focusing position becomes the first area 28 under the control of the control unit 8 . Next, as shown in FIG. 15( c ), under the control of the control unit 8 , the actuator 70 moves only the objective lens 43 so that the focusing position becomes the second area 29 . The control unit 8 may move the objective lens 43 by the actuator 70 in such a manner that the entire area of the first area 28 and the entire area of the second area 29 in the Z direction are sequentially focused positions, or may only make the second area 29 move. The objective lens 43 is moved by the actuator 70 so that a part of the first area 28 and a part of the second area 29 become sequential focusing positions. In addition, the control part 8 may move the objective lens 43 by the actuator 70 so that the 2nd area|region 29 may become a condensing position first, and then the 1st area 28 shall become a condensing position. By performing the second control, imaging of the inside of the wafer 20 in the first area 28 and the second area 29 is performed.

FIG. 16 is a diagram explaining details of movement of the light-converging position using the drive unit 7 and the actuator 70 . As shown in (a) of FIG. 16 , when the thickness of the wafer 20 is different from the assumed thickness, etc., it is considered that the above-mentioned light-collecting position after the first control deviates from the rear surface 21 a. Therefore, the control unit 8 executes the third control, that is, in the second control after the first control, first, the position of the objective lens 43 is moved in the Z direction in a state where the area near the back surface 21a becomes the light-condensing position. The actuator 70 is controlled, and the detailed position of the rear surface 21a is specified based on the detection result of light by the light detection unit 44 in this state, so that the objective lens 43 moves to the specified detailed position of the rear surface 21a to be the light-condensing position. The actuator 70 is controlled in such a manner that the position is the reference position (see (b) of FIG. 16 ). Here, the region near the rear surface 21a may be a region including all the light-collecting positions that can deviate from the rear surface 21a after the first control.

In the third control, the actuator 70 moves only the objective lens 43 so as to move the condensing position after the first control in the Z direction under the control of the control unit 8 . By continuously changing the focusing position in the Z direction in this way, imaging near the rear surface 21a is performed. The control part 8 may detect the element pattern of the back surface 21a based on the signal from the photodetection part 44 as a photographing result, and may specify the detailed position of the back surface 21a based on this element pattern. Alternatively, the control unit 8 may identify the results of direct observation and rear reflection observation of the cracks 14 from the modified region 12 in the vicinity of the back surface 21a based on the signal from the photodetection unit 44, and identify the location of the back surface 21a from the specified information. Detailed location. Then, under the control of the control unit 8 , the actuator 70 moves the objective lens 43 to the reference position where the detailed position of the back surface 21 a becomes the light-condensing position. By moving the objective lens 43 to the reference position in this way, the fourth control described later can be performed starting from the reference position where the condensing position is appropriately located on the back surface 21 a.

The control unit 8 executes the fourth control, that is, in the second control, the actuator 70 is controlled so as to move the objective lens 43 from the above-mentioned reference position to a position where at least a part of the first region 28 becomes the light-converging position ( Referring to (d) of FIG. 16 , and from the reference position, the objective lens 43 is moved to a position where at least a part of the second region 29 becomes the light-condensing position and the actuator 70 is controlled (see (c) of FIG. 16 ). . The control unit 8 may move the objective lens 43 by the actuator 70 in such a manner that the entire area of the first area 28 and the entire area of the second area 29 in the Z direction are sequentially focused positions, or may only make the second area 29 move. The objective lens 43 is moved by the actuator 70 so that a part of the first region 28 and a part of the second region 29 become sequential focusing positions.

In this way, in the form shown in FIG. 16 , the movement of the objective lens 43 to the reference position which is the start position of imaging is carried out by the first control and the third control, and the inside of the wafer 20 is carried out by the subsequent fourth control. The imaging process of imaging is to export information about the modified region 12 (for example, detection of the position of the tip of the crack 14).

FIG. 17 is a flowchart of an example of an observation method implemented by the laser processing apparatus 1 . Hereinafter, an example of the observation method will be described with reference to FIGS. 17 and 16 .

As shown in FIG. 17 , first, the actuator 70 is controlled by the control unit 8 so as to fix the actuator 70 at the center position of the movable range of the actuator 70 in the Z direction (step S1 : pre-process). In addition, such centering of the actuator 70 can also be performed manually.

Next, as shown in (a) of FIG. 16 , the control unit 8 controls the driving unit 7 so that the imaging unit 4 moves to a position where the rear surface 21 a becomes the light-focusing position (step S2 : first step).

Next, the control unit 8 controls the actuator 70 so that the position of the objective lens 43 moves in the Z direction in a state where the area near the back surface 21a becomes the light-collecting position, and based on the light detection unit 44 in this state, The detailed position of the back surface 21a is specified as a result of the detection, and as shown in FIG. actuator 70 . That is, the focusing position is corrected based on the detection result (step S3: second process).

Next, as shown in (c) of FIG. 16 , the control unit 8 controls the actuator 70 so that the objective lens 43 is moved to a position where the second region 29 , which is the region on the rear viewing side, becomes the light-condensing position. (Step S4: second process). Then, as shown in (d) of FIG. 16 , the control unit 8 controls the actuator 70 so that the objective lens 43 moves to a position where the first region 28, which is the region on the surface observation side, becomes the light-converging position. (Step S5: second process). The above is an example of the observation method.

In addition, the observation method implemented by the laser processing apparatus 1 is not limited to the form shown in FIG.16 and FIG.17. FIG. 18 is a diagram illustrating the details of another example of movement of the light-converging position using the drive unit 7 and the actuator 70 . In the mode shown in FIG. 18, the above-mentioned first control (see FIG. 18(a)) is executed in the same manner as the mode shown in FIG. 16, and the above-mentioned first control is executed in the second control after the first control. Three controls (see (b) of FIG. 18 ). That is, the control shown in (a) of FIG. 18 corresponds to the control shown in (a) of FIG. 16 , and the control shown in (b) of FIG. 18 corresponds to the control shown in (b) of FIG. 16 . Here, in the mode shown in FIG. 16 , in the third control (see FIG. 16( b )) to determine the reference position, although the imaging result near the back surface 21a is obtained, the imaging result is only used to determine the reference position. , and is not used as information related to the export of information related to the modified region 12 of the wafer 20 . In this regard, in the form shown in FIG. 18 , the photographing results near the back surface 21 a obtained in the third control (see (b) of FIG. 18 ) are used not only as information related to the export of the reference position, Furthermore, it is also used as information related to the export of information on the modified region 12 of the wafer 20 . In this manner, by effectively utilizing the imaging result of the third control, it is possible to avoid repeated imaging processing for the same area, and to perform imaging more efficiently.

Now, in the third control (see (b) of FIG. 18 ) for specifying the reference position, the imaging result of the area A1 (see (c) of FIG. 18 ) near the back surface 21 a is obtained. In this case, the control unit 8 executes the fifth control, that is, to move the entire imaging unit 4 to the detailed position of the specified rear surface 21a in the first area 28 or the second area 29 and the third control. The driving unit 7 is controlled so that at least a part of an area not serving as the light-collecting position, that is, an area other than the above-mentioned area A1 , which is a non-photographing area, becomes the light-collecting position. In the example shown in FIG. 18 , the unphotographed area of the second area 29 is an area that does not need to be photographed. In this case, the control unit 8 controls the drive unit 7 so that the entire imaging unit 4 moves to a position where the area A2 which is the non-imaging area of the first area 28 becomes the light-collecting position (pulls up). More specifically, the control unit 8 moves the entire imaging unit 4 until the area A2 becomes focused by the sixth control described later in which the actuator 70 moves the objective lens 43 in consideration of the movable range of the actuator 70. The drive unit 7 is controlled in a position-by-position manner.

Then, the control unit 8 executes the sixth control, that is, the position of the objective lens 43 of the imaging unit 4 after the fifth control is used as a new reference position, so that the objective lens 43 is moved to the area A2 which is an area included in the non-imaging area. The actuator 70 is controlled so that the position becomes the focusing position. The control unit 8 may move the objective lens 43 by the actuator 70 so that the entire area A2 in the Z direction is at the sequential focusing position, or may set only a part of the area A2 at the sequential focusing position. In this way, the objective lens 43 is moved by the actuator 70 .

In this way, in the mode shown in FIG. 18 , the imaging results obtained in the third control can be used not only as information related to the export of the reference position but also as a collection of information related to the modified region 12 of the wafer 20 . The fifth control and the sixth control can be executed efficiently by performing the fifth control and the sixth control in such a manner that the relevant information is used and only the area where the imaging result cannot be obtained in the third control is taken. In addition, for example, when the desired imaging area is not all within the movable range of the actuator 70, it is also possible to sequentially expand the imaging area by performing (multiple times as necessary) the fifth control and the sixth control. The entire desired imaging area is accurately captured.

[Effect] Next, the operation and effect of the laser processing apparatus 1 (observation apparatus) and the observation method according to the present embodiment will be described.

The laser processing apparatus 1 of this embodiment is an observation apparatus for observing a wafer 20 having a surface 21b and a back surface 21a and having a modified region 12 formed inside by irradiating laser light from the surface 21b side, and is characterized in that it includes: The unit 4 has a light source 41 that outputs light that is transparent to the wafer 20, an objective lens 43 that condenses the light output from the light source 41 on a light-converging position on the wafer 20, and a device that detects light propagating in the wafer 20. The photodetection section 44; the driving unit 7 that supports the imaging unit 4 and moves the imaging unit 4 in the Z direction that is the up-down direction; the actuator 70 that is provided on the objective lens 43 and moves the objective lens 43 in the Z direction; and the control section 8. The control section 8 executes: the first control to control the driving unit 7 so that the imaging unit 4 moves to the position where the back surface 21a becomes the light-focusing position; and the second control to move the objective lens 43 after the first control The actuator 70 is controlled so that the area between the back surface 21a and the front surface 21b, that is, at least a part of the first area 28 becomes the light-condensing position, and the objective lens 43 is moved to the side opposite to the front surface 21b with respect to the back surface 21a. The actuator 70 is controlled so that at least a part of the second region 29, which is the second region 29, becomes the focusing position.

In such a laser processing apparatus 1, during observation of the wafer 20 on which the modified region 12 is formed, the drive unit 7 that moves the imaging unit 4 in the Z direction is controlled so that the imaging unit 4 moves to the point where the wafer 20 The back surface 21a of the back surface 21a becomes the light-condensing position, and then, the actuator 70 that moves the objective lens 43 in the Z direction is controlled to move the objective lens 43 to the area between the back surface 21a and the surface 21b, that is, the first area 28 becomes the light-condensing position. position, and move the objective lens 43 to a position where the second area 29, which is an area on the opposite side of the front surface 21b with respect to the rear surface 21a, becomes the light-collecting position. In this way, by moving the objective lens 43 so that both the first region 28 and the second region 29 become the light-condensing position, it is possible to appropriately implement the process from the modified region 12 when the first region 28 is the light-condensing position. Both direct observation of the cracks 14 and the like and observation of the cracks 14 and the like when the second region 29 is the light-collecting position by back reflection. Moreover, the movement of the objective lens 43 that makes the first area 28 and the second area 29 the focus position is implemented by the actuator 70 that moves only the objective lens 43 of the imaging unit 4, for example, it is the same as the case of moving the entire imaging unit 4. In contrast, the focusing position can be moved at high speed, and vibration after the movement can also be suppressed. Here, the laser processing apparatus 1 of this embodiment has the drive unit 7 which moves the whole imaging unit 4 in Z direction, and the actuator 70 which moves the objective lens 43 of the imaging unit 4 in the Z direction. By arranging both the drive unit 7 and the actuator 70 in this way, for example, rough alignment can be performed by the drive unit 7, detailed alignment can be performed by the actuator 70, and detailed alignment can be realized by Compared with the case where the entire movement of the actuator in the Z direction is performed, the cost of the device can be suppressed, and the alignment (focus alignment of the imaging range, etc.) that requires precision can be performed with high precision. In the laser processing apparatus 1 of the present embodiment, first, the imaging unit 4 is controlled by the drive unit 7 so that the rear surface 21 a, which is the boundary surface between the first region 28 and the second region 29, becomes the light-collecting position, and then, the imaging unit 4 is controlled by the The objective lens 43 is controlled by the actuator 70 so that the first area 28 and the second area 29 respectively become light-converging positions. Before the control by the actuator 70 starts, the movable range of the actuator 70 can be utilized to the maximum by aligning the light-collecting position with the rear surface 21a (the boundary surface between the first region 28 and the second region 29 ). , the high-speed movement of the objective lens 43 that makes the first area 28 and the second area 29 the light-condensing positions is appropriately implemented. As described above, according to the laser processing apparatus 1 of the present embodiment, it is possible to move the focusing position at high speed, and to improve the tact time.

Before the first control, the control unit 8 may further perform prior control of controlling the actuator 70 so as to fix the actuator 70 at the center position of the movable range of the actuator 70 in the Z direction. Thus, the second control can be performed in a state where the actuator 70 is sufficiently movable in two directions (up and down) in the Z direction, and the movable range of the actuator 70 can be utilized to the maximum, and the first control can be appropriately performed. The area 28 and the second area 29 are the high-speed movement of the objective lens 43 at the condensing position.

In the second control, the control unit 8 may also execute the third control to control the actuator 70 so that the position of the objective lens 43 moves in the Z direction in a state where the area near the back surface 21a becomes the light-condensing position, and based on this state The detailed position of the back surface 21a is identified by the light detection result of the lower photodetector 44, and the actuation is controlled so that the objective lens 43 moves to a reference position where the specified detailed position of the back surface 21a becomes the light-condensing position. and a fourth control to control the actuator 70 so that the objective lens 43 moves from the reference position to a position where at least a part of the first area 28 becomes the light-condensing position, and to move the objective lens 43 from the reference position to the position where The actuator 70 is controlled so that at least a part of the second area 29 becomes the light-collecting position. Even with the first control, for example, when the thickness of the actual wafer 20 is different from the assumption, it is considered that the light-collecting position deviates from the rear surface 21a. In this case, there is a problem that imaging of the first region 28 and the second region 29 which utilizes the above-mentioned movable range of the actuator 70 to the maximum cannot be realized. Regarding this point, in the second control, the detailed position of the back surface 21a is specified as a reference position based on the light detection result (third control), and the objective lens 43 is moved from the reference position to the first area by the actuator 70 28 and the imaging range of the second area 29 (fourth control), so that even if the focus position deviates from the back surface 21a in the first control, the reference position can be set appropriately to realize the maximum utilization The imaging of the first area 28 and the second area 29 of the movable range of the actuator 70 is performed.

In the second control, the control unit 8 may also execute the third control to control the actuator 70 so that the position of the objective lens 43 moves in the Z direction in a state where the area near the back surface 21a becomes the light-condensing position, and based on this state The detailed position of the back surface 21a is identified by the light detection result of the lower photodetector 44, and the actuation is controlled so that the objective lens 43 moves to a reference position where the specified detailed position of the back surface 21a becomes the light-condensing position. device 70, and also implement: the fifth control, so that the imaging unit 4 moves to the area within the first area 28 or the second area 29 and is not used as the light-focusing position when it is the detailed position of the specific back 21a in the third control The driving unit 7 is controlled in such a manner that at least a part of the non-photographing region becomes the position of the light-collecting position; and the sixth control is to use the position of the objective lens 43 of the photographing unit 4 after the fifth control as a new reference position, and make the objective lens 43, the actuator 70 is controlled so that the area included in the non-photographing area becomes the focus position. According to the third control, it is possible to photograph the vicinity of the rear surface 21 a while specifying the detailed position of the rear surface 21 a. Therefore, in this observation device 1, the driving unit 7 is controlled so that the imaging unit 4 moves to a position where the unimaging area that is not captured in the third control becomes the focus position (fifth control), so that the fifth control The controlled position of the objective lens 43 becomes a new reference position, and the actuator 70 is controlled so that the objective lens 43 is moved to a position where the unphotographed area becomes the light-converging position (sixth control). According to such a configuration, since the control is performed so that the area not captured by the third control becomes the focus position, it is possible to perform imaging more efficiently without performing useless imaging. In addition, according to such a structure, even if the area to be imaged is not within the movable range of the actuator 70 at the initial reference position, the area to be imaged can be reliably imaged by changing the reference position. for photography.

The observation method of this embodiment is an observation method for observing a wafer 20 having a surface 21b and a back surface 21a and having a modified region 12 formed inside by irradiating laser light from the surface 21b side, and is characterized in that it includes: The first process of moving the photographing unit 4 to a position where the rear surface 21a becomes the light-collecting position by the drive unit 7 that moves the photographing unit 4 in the Z direction as the up-down direction; and by making the objective lens 43 included in the photographing unit 4 The actuator 70 that moves in the Z direction moves the objective lens 43 to a position where at least a part of the first region 28, which is the area between the back surface 21a and the surface 21b, becomes the light-condensing position, and the objective lens 43 is moved to a position where the light is focused relative to the back surface 21a. This is the second step in which at least a part of the second region 29, which is the region on the opposite side of the surface 21b, becomes the light-collecting position. According to the observation method of this embodiment, it is possible to move the focusing position at high speed, and to improve the imaging tact.

The observation method described above may further include a pre-process of controlling the actuator 70 so that the actuator 70 is fixed at the center position of the movable range of the actuator 70 in the Z direction before the first process. According to such a structure, the movable range of the actuator 70 can be fully utilized, and the high-speed movement of the objective lens 43 which makes the 1st area|region 28 and the 2nd area|region 29 into a light-condensing position can be performed suitably.

1: Laser processing device 2: Carrying table 3: Laser irradiation unit 4: Photography unit 5: Photography unit 6: Photography unit 7: Drive unit 8: Control Department 11: object 12:Modified area 12a: Modified area 12b:Modified area 12s: modification point 14: Crack 14a: crack 14b: Crack 14c: Crack 14d: Crack 14e: front end 15: line 20: Wafer 21: Semiconductor substrate 21a: back 21b: Surface 21c: Gap 22: Functional component layer 22a: Functional elements 23: grid area 28: The first area 29:Second area 31: light source 32: Spatial light modulator 33: Concentrating lens 41: light source 42: Mirror 43: objective lens 43a: Calibration ring 44: Light detection unit 51: light source 52: Mirror 53: lens 54: Light detection unit 70: Actuator 150: display A1: area A2: area A3: area C: focus point C1: focus point C2: focus point L: laser light I1: light I2: light F: focus Fv: virtual focus

[ Fig. 1 ] is a configuration diagram of a laser processing apparatus according to an embodiment. [ Fig. 2 ] is a plan view of a wafer according to one embodiment. [ Fig. 3 ] is a cross-sectional view of a part of the wafer shown in Fig. 2 . [ Fig. 4 ] is a configuration diagram of the laser irradiation unit shown in Fig. 1 . [ Fig. 5 ] is a configuration diagram of the imaging unit for inspection shown in Fig. 1 . [FIG. 6] It is a block diagram of the imaging unit for alignment correction shown in FIG. 1. [FIG. [ Fig. 7] Fig. 7 is a cross-sectional view of a wafer for explaining the imaging principle of the inspection imaging unit shown in Fig. 5 , and images of various parts of the inspection imaging unit. [ Fig. 8] Fig. 8 is a cross-sectional view of a wafer for explaining the imaging principle of the inspection imaging unit shown in Fig. 5 , and images of various parts of the inspection imaging unit. [ Fig. 9 ] is an SEM image of a modified region and cracks formed inside a semiconductor substrate. [ Fig. 10 ] is an SEM image of a modified region and cracks formed inside a semiconductor substrate. [ FIG. 11 ] is an optical path diagram for explaining the imaging principle of the imaging unit for inspection shown in FIG. 5 , and a schematic diagram showing an image at a focus of the imaging unit for inspection. [ Fig. 12 ] is an optical path diagram for explaining the imaging principle of the imaging unit for inspection shown in Fig. 5 , and a schematic diagram showing an image at a focus of the imaging unit for inspection. [ Fig. 13 ] is a configuration diagram of an objective lens equipped with an actuator. [ Fig. 14 ] is a configuration diagram of an objective lens equipped with an actuator. [ Fig. 15 ] is a diagram illustrating an outline of movement of a light-converging position by a drive unit and an actuator. [ Fig. 16 ] is a diagram explaining details of movement of a light-converging position by a drive unit and an actuator. [ Fig. 17 ] is a flowchart of an example of the observation method. [ Fig. 18 ] is a diagram explaining details of movement of a light-converging position by a drive unit and an actuator.

1: Laser processing device

2: Carrying table

3: Laser irradiation unit

4: Photography unit

5: Photography unit

6: Photography unit

7: Drive unit

8: Control Department

11: object

12:Modified area

12s: modification point

150: display

C: focus point

L: laser light

Claims (6)

An observation device, characterized in that: An observation device for observing a wafer having a first surface and a second surface and having a modified region formed therein by irradiating laser light from the side of the first surface, have: an imaging unit having a light source that outputs light that is transmissive to the wafer, a condensing lens that condenses the light output from the light source at a condensing position on the wafer, and detects light propagating through the wafer. the light detection unit; a drive unit that supports the imaging unit and moves the imaging unit in a Z direction that is an up-down direction; an actuator, which is provided on the aforementioned condensing lens and moves the aforementioned condensing lens in the aforementioned Z direction; and Control Department, The aforementioned control unit is configured to perform the following controls: The first control is to control the drive unit so that the imaging unit moves to a position where the second surface becomes the light-collecting position; and In the second control, after the first control, the condensing lens is moved to a position where at least a part of the first region, which is the region between the second surface and the first surface, becomes the condensing position. The aforementioned actuator controls the aforementioned condensing lens to move to a position where at least a part of the second area, which is an area on the opposite side of the aforementioned first surface with respect to the aforementioned second surface, becomes the aforementioned condensing position. actuator. The observation device as claimed in claim 1, wherein: Before the first control, the control unit further performs: prior control to control the actuator so that the actuator is fixed at a center position of the movable range of the actuator in the Z direction. The observation device as claimed in claim 1 or 2, wherein: The control unit is configured to execute the following control in the second control: The third control is to control the actuator so that the position of the condensing lens moves in the Z direction when the region near the second surface becomes the condensing position, based on the light detection in this state The method of specifying the detailed position of the second surface based on the detection result of the light of the portion, and moving the condenser lens to a reference position as a position where the specified detailed position of the second surface becomes the light-condensing position controlling the aforementioned actuator; and The fourth control is to control the actuator so that the condensing lens moves from the reference position to a position where at least a part of the first region becomes the condensing position, and to move the condensing lens from the reference position The actuator is controlled so as to move to a position where at least a part of the second region becomes the light-collecting position. The observation device as claimed in claim 1 or 2, wherein: In the second control described above, the control unit, constituted in such a way that the following controls are exercised: The third control is to control the actuator so that the position of the condensing lens moves in the Z direction when the region near the second surface becomes the condensing position, based on the light detection in this state The detailed position of the second surface is identified by the detection result of the light in the portion, and the condensing lens is moved to the position of the condensing lens that makes the detailed position of the specified second surface the condensing position. The reference position is controlled by means of the aforementioned actuator, constituted in such a way that the following controls are also exercised: The fifth control is to control the drive unit so that the imaging unit moves to a position where at least a part of the non-imaging area is the area within the first area or the second area, And when the detailed position of the second surface is specified in the third control, the area that is not used as the light-gathering position; and The sixth control is to use the position of the condensing lens of the imaging unit after the fifth control as the new reference position, and move the condensing lens so that an area included in the non-photographing area becomes the condensing position. The position of the aforementioned actuator is controlled in a manner. A method of observation characterized in that: is an observation method for observing a wafer having a first surface and a second surface in which a modified region is formed by irradiating laser light from the side of the first surface, include: In the first step, the imaging unit is moved to a position where the second surface becomes a light-collecting position by a driving unit that moves the imaging unit in a Z direction that is an up-down direction; and In the second step, the condenser lens included in the imaging unit is moved to the first area between the second surface and the first surface by an actuator that moves the condenser lens included in the imaging unit in the Z direction. At least a part of one area becomes the position of the aforementioned condensing position, and the aforementioned condensing lens is moved to make at least a part of the second area, which is an area on the opposite side of the aforementioned first surface with respect to the aforementioned second surface, become the aforementioned condensing position. location location. The observation method as recited in claim 5, wherein: It also includes a prior step of controlling the actuator so that the actuator is fixed at the center position of the Z-direction movable range of the actuator before the first step.

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