Observation apparatus and observation method

Abstract

The laser processing apparatus of the present invention comprises: a photographic unit having a light source, an objective lens, and a light detection unit; a drive unit for moving the photographic unit in the Z direction, which is a vertical direction; an actuator for moving the objective lens in the Z direction; and a control unit that performs: a first control to control the drive unit to move the photographic unit to a position in which the back surface becomes a focusing position; and a second control, after the first control, to control the actuator to move the objective lens to a position in which a region between the back surface and the surface, i.e., a first region, becomes a focusing position, and to control the actuator to move the objective lens to a position in which a second region, which is a region opposite to the surface relative to the back surface, becomes a focusing position.

Description

Technical Field

[0001] One aspect of the present invention relates to an observation device and an observation method. Prior Technology

[0002] A laser processing apparatus is known to irradiate the wafer with a semiconductor substrate and a functional element layer formed on the semiconductor substrate along multiple lines to form multiple rows of modified regions inside the semiconductor substrate along the multiple lines. The laser processing apparatus described in Japanese Patent Application Publication No. 2017-64746 includes a photographic unit (e.g., an infrared camera) that can observe the modified regions formed inside the semiconductor substrate and processing damage formed on the functional element layer from one side of the semiconductor substrate. Summary of the Invention

[0003] In laser processing apparatuses like those described above, when observing information related to the modified region (e.g., cracks extending from the modified region), for example, the tip of a crack extending from the modified region to another surface (the surface opposite to the surface irradiated by the laser) cannot be detected by using that tip as a focal point. Instead, it can be detected by using a point symmetrical to that tip relative to the other surface as a focal point. Thus, even points symmetrical to the other surface need to be used as focal points, increasing the imaging area. Normally, a control unit that moves the entire imaging unit moves it in the vertical direction (Z-direction), but with a large imaging area, the focal point movement cannot be performed at a sufficiently high speed. The time required for focal point movement is longer than the imaging rate, leading to a decrease in the imaging cycle time. Furthermore, even if high-speed focal point movement is achieved, the vibration after the entire imaging unit moves at high speed is difficult to calm, and imaging cannot be performed until the vibration subsides, resulting in a decrease in the imaging cycle time.

[0004] One aspect of the present invention was made in view of the above circumstances, and it relates to an observation device and observation method capable of improving the photographic pace.

[0005] One aspect of the observation apparatus of the present invention is an observation apparatus 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. The apparatus is characterized by comprising: a photographic unit having a light source that outputs transmissive light to the wafer, a focusing lens that focuses the light output from the light source onto a focusing position on the wafer, and a light detection unit that detects light propagating in the wafer; a drive unit that supports the photographic unit and moves the photographic unit in the Z direction, which is a vertical direction; an actuator disposed on the focusing lens and moves the focusing lens in the Z direction; and a control unit that performs: a first control to control the drive unit to move the photographic unit to a position where the second surface becomes a focusing position; and a second control, after the first control, to control the actuator to move the focusing lens to a position where at least a portion of the region between the second surface and the first surface, i.e., the first region, becomes a focusing position, and to control the actuator to move the focusing lens to a position where at least a portion of the region opposite to the first surface, i.e., the second region, becomes a focusing position.

[0006] In one aspect of the observation apparatus of the present invention, during the observation of a wafer with a modified region, a drive unit that moves the imaging unit in the Z direction is controlled to move the imaging unit to a position where the second surface (back surface) of the wafer becomes a focusing position. Then, an actuator that moves the focusing lens in the Z direction is controlled to move the focusing lens to a position where the region between the second surface and the first surface, i.e., the first region, becomes a focusing position, and the focusing lens is also moved to a position where the region opposite to the first surface, i.e., the second region, becomes a focusing position. In this way, by moving the focusing lens in such a way that both the first and second regions become focusing positions, it is possible to appropriately perform both direct observation of cracks originating from the modified region when the first region is a focusing position, and observation of cracks originating from the back surface (second surface) when the second region is a focusing position. Furthermore, by using an actuator that moves only the condenser lens of the imaging section to move the condenser lens to the focusing position of the first and second regions, the focusing position movement can be performed at high speed compared to moving the entire imaging section, and vibration after movement can be suppressed. Here, an observation device of the present invention includes a drive unit that moves the entire imaging section in the Z direction and an actuator that moves the condenser lens of the imaging section in the Z direction. By arranging the drive unit and the actuator in this way, for example, approximate alignment can be performed by the drive unit and detailed alignment can be performed by the actuator, thereby reducing device costs and performing alignment (focusing position of the imaging range, etc.) with high precision. In an observation device of the present invention, firstly, the imaging section is controlled by the drive unit to make the second surface, which is the boundary between the first and second regions, the focusing position is made, and then the condenser lens is controlled by the actuator to make the first and second regions the focusing positions respectively. Before control by the actuator begins, by aligning the focusing position with the second surface (the boundary between the first and second regions), the actuator's range of motion can be maximized, and high-speed movement of the focusing lens, which positions the first and second regions as focusing points, can be appropriately implemented. As described above, an observation device according to one aspect of the present invention can perform high-speed focusing position movement, thereby improving the photographic cycle time.

[0007] The control unit can also perform pre-control of the actuator by fixing it at the center of its movable range in the Z direction before the first control. As a result, the second control can be implemented while the actuator is fully movable in both directions (up and down) in the Z direction, making the maximum use of the actuator's movable range and appropriately implementing high-speed movement of the focusing lens that focuses the light in the first and second regions.

[0008] The control unit can also implement the following in the second control: a third control, which controls the actuator to move the position of the condenser lens in the Z direction when the region near the second surface becomes a focusing position, based on the light detection result of the light detection unit in this state, to determine the detailed position of the second surface, and controls the actuator to move the condenser lens to a position where the specified detailed position of the second surface becomes a focusing position, i.e., a reference position; and a fourth control, which controls the actuator to move the condenser lens from the reference position to a position where at least a portion of the first region becomes a focusing position, and controls the actuator to move the condenser lens from the reference position to a position where at least a portion of the second region becomes a focusing position. Even with the first control, for example, in cases where the actual wafer thickness differs from the intended thickness, the focusing position is still considered to deviate from the second surface. In this case, there is a problem that the imaging of the first and second regions, which utilize the aforementioned actuator's range of motion, cannot be maximized. In this regard, in the second control, the detailed position of the specific second surface is used as a reference position based on the light detection result (third control). The condenser lens is moved from the reference position to the imaging range of the first and second regions by the actuator (fourth control). Thus, even if the condenser position deviates from the second surface in the first control, the reference position can be set appropriately to achieve imaging of the first and second regions with maximum utilization of the actuator's movable range.

[0009] The control unit can also perform the following in the second control: a third control, which controls the actuator to move the position of the condenser lens in the Z direction when the region near the second surface becomes a focusing position, and controls the actuator to move the condenser lens to a reference position where the specific detailed position of the second surface becomes a focusing position based on the light detection result of the light detection unit in this state, and further performs: a fifth control, which controls the drive unit to move the imaging unit to a position where at least a portion of the un-photographed region, which is a region within the first or second region and is not a focusing position when the specific detailed position of the second surface is determined in the third control, becomes a focusing position; and a sixth control, which controls the actuator to move the condenser lens of the imaging unit after the fifth control to a position where the region included in the un-photographed region becomes a focusing position, using the position of the condenser lens of the imaging unit after the fifth control as a new reference position. According to the third control, imaging of the region near the second surface can be performed during the process of determining the specific detailed position of the second surface. Therefore, in this observation device, the drive unit is controlled (fifth control) to move the imaging unit to a position where the un-imaged area not imaged in the third control becomes the focusing position, and the actuator is controlled (sixth control) to make the position of the focusing lens after the fifth control a new reference position and move the focusing lens to a position where the unimaged area becomes the focusing position. With this structure, because control is performed to make the area not imaged in the third control the focusing position, invalid imaging is avoided, thus enabling more efficient imaging. Furthermore, with this structure, even if the area to be imaged is not within the actuator's range of motion at the initial reference position, the area to be imaged can be reliably imaged by changing the reference position.

[0010] One aspect of the observation method of the present invention is a method for observing a wafer having a first surface and a second surface, and having a modified region formed internally by irradiating laser light from the first surface side. The method is characterized by comprising: a first step of moving the imaging unit to a position where the second surface becomes a focusing position by a drive unit that moves the imaging unit in the Z direction (vertical direction); and a second step of moving the focusing lens included in the imaging unit to a position where at least a portion of the region between the second surface and the first surface (i.e., the first region) becomes a focusing position by an actuator that moves the focusing lens in the Z direction; and a third step of moving the focusing lens to a position where at least a portion of the region opposite to the first surface (i.e., the second region) becomes a focusing position. According to one aspect of the observation method of the present invention, the focusing position movement can be performed at high speed, thereby improving the imaging cycle time.

[0011] The aforementioned observation method can also be further enhanced by controlling the actuator's pre-process before the first process, in a manner that fixes the actuator at the center of its movable range in the Z direction. With this structure, the movable range of the actuator can be maximized, and high-speed movement of the focusing lens, which positions the first and second regions as focusing points, can be appropriately implemented.

[0012] According to one embodiment of the present invention, even when the photographic area is large, the focus position can be moved at high speed, thereby improving the photographic pace. Simple Explanation of the Diagram

[0013] [Figure 1] is a structural diagram of a laser processing apparatus according to one embodiment. [Figure 2] is a top view of a wafer in one embodiment. [Figure 3] is a cross-sectional view of a portion of the wafer shown in Figure 2. [Figure 4] is a structural diagram of the laser irradiation unit shown in Figure 1. [Figure 5] is a structural diagram of the inspection camera unit shown in Figure 1. [Figure 6] is a structural diagram of the photographic unit for alignment correction shown in Figure 1. [Figure 7] is a cross-sectional view of a wafer used to illustrate the photographic principle of the inspection photographic unit shown in Figure 5, and images of the inspection photographic unit at various locations. [Figure 8] is a cross-sectional view of a wafer used to illustrate the photographic principle of the inspection photographic unit shown in Figure 5, and images of the inspection photographic unit at various locations. [Figure 9] is a SEM image of the modified region and cracks formed inside the semiconductor substrate. [Figure 10] is a SEM image of the modified region and cracks formed inside the semiconductor substrate. [Figure 11] is an optical path diagram illustrating the photographic principle of the inspection photographic unit shown in Figure 5, and a schematic diagram showing the image at the focal point of the inspection photographic unit. [Figure 12] is an optical path diagram illustrating the photographic principle of the inspection photographic unit shown in Figure 5, and a schematic diagram showing the image at the focal point of the inspection photographic unit. [Figure 13] is a structural diagram of the objective lens equipped with an actuator. [Figure 14] is a structural diagram of the objective lens equipped with an actuator. [Figure 15] is a diagram illustrating the general layout of the focusing position movement using a drive unit and an actuator. [Figure 16] is a diagram illustrating the details of the focusing position movement using the drive unit and actuator. [Figure 17] is a flowchart of an example of the observation method. [Figure 18] is a diagram illustrating the details of the focusing position movement using the drive unit and actuator. Implementation

[0014] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In these drawings, identical or equivalent parts are labeled with the same symbols, and repeated descriptions are omitted. [Structure of laser processing equipment]

[0015] As shown in Figure 1, the laser processing apparatus 1 includes a stage 2, a laser irradiation unit 3, multiple imaging units 4, 5, and 6, a drive unit 7, a control unit 8, and a display 150. The laser processing apparatus 1 is a device that forms a modified region 12 on a workpiece 11 by irradiating it with laser light L. Furthermore, the laser processing apparatus 1 is an observation device for observing the workpiece 11 (wafer 20 described later) on which the modified region 12 is formed.

[0016] The stage 2 supports the object 11, for example, by adsorbing and adhering a film to the object 11. The stage 2 is movable along the X and Y directions respectively, and can rotate about an axis parallel to the Z direction as its center line. Here, the X and Y directions are mutually perpendicular first and second horizontal directions, and the Z direction is the vertical direction.

[0017] The laser irradiation unit 3 focuses a laser light L that is transmissive to the object 11 to irradiate the object 11. When the laser light L is focused into the interior of the object 11 supported by the stage 2, the laser light L is particularly absorbed in the part corresponding to the focusing point C of the laser light L, and a modified region 12 can be formed inside the object 11.

[0018] The modified region 12 is a region whose density, refractive index, mechanical strength, or other physical properties differ from those of the surrounding unmodified region. Examples of modified regions 12 include melt-processed regions, cracked regions, regions with insulation failure, and regions with refractive index changes. The modified region 12 has the characteristic that cracks easily extend from the modified region 12 to the side where the laser beam L is incident and to the opposite side. This characteristic of the modified region 12 is utilized in the cutting of the object 11.

[0019] As an example, when the stage 2 is moved along the X direction and the focusing point C is moved relative to the object 11 along the X direction, multiple modified particles 12s are formed in a row along the X direction. Each modified particle 12s is formed by irradiation with a single pulse of laser light L. A row of modified regions 12 is a collection of multiple modified particles 12s arranged in a row. Adjacent modified particles 12s may be connected to each other or separated from each other, depending on the relative movement speed of the focusing point C relative to the object 11 and the repetition frequency of the laser light L.

[0020] The photography unit 4 photographs the modified region 12 formed in the object 11, and the front end of the crack extending from the modified region 12.

[0021] Under the control of the control unit 8, the imaging units 5 and 6 photograph the object 11 supported by the platform 2 by transmitting light through the object 11. The images obtained by the imaging units 5 and 6 are used, as an example, for calibrating the irradiation position of the laser light L.

[0022] The drive unit 7 supports the laser irradiation unit 3 and multiple imaging units 4, 5, and 6. The drive unit 7 causes the laser irradiation unit 3 and the multiple imaging units 4, 5, and 6 to move along the Z direction.

[0023] The control unit 8 controls the operation of the stage 2, the laser irradiation unit 3, the multiple imaging units 4, 5, and 6, and the drive unit 7. The control unit 8 is configured as a computer device including a processor, memory, storage unit, and communication device. In the control unit 8, the processor executes software (programs) read from the memory, etc., controls the reading and writing of data in the memory and storage unit, and the communication performed by the communication device.

[0024] The display 150 has the functions of an input section for receiving information input from the user and a display section for displaying information to the user.

[0025] [Structure of the object] The object 11 in this embodiment, as shown in Figures 2 and 3, is a wafer 20. The wafer 20 includes a semiconductor substrate 21 and a functional element layer 22. In this embodiment, the wafer 20 is described as having a functional element layer 22, but the wafer 20 may or may not have a functional element layer 22, or it 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 21a of the semiconductor substrate 21. The functional element layer 22 includes a plurality of functional elements 22a arranged two-dimensionally along the back surface 21a. The functional elements 22a are, for example, light-receiving elements such as photodiodes, light-emitting elements such as laser diodes, and circuit elements such as memory. The functional elements 22a may also be stacked in multiple layers and configured in three dimensions. In addition, although a notch 21c indicating the crystal orientation is provided in the semiconductor substrate 21, an orientation plane may be provided instead of the notch 21c.

[0026] The wafer 20 is cut along multiple lines 15 for each functional element 22a. When viewed from the thickness direction of the wafer 20, the multiple lines 15 pass between each of the functional elements 22a. More specifically, when viewed from the thickness direction of the wafer 20, the lines 15 pass through the center (center in the width direction) of the grid region 23. The grid region 23 extends in the functional element layer 22 in a manner that passes between adjacent functional elements 22a. In this embodiment, the multiple functional elements 22a are arranged in a matrix along the back surface 21a, and the multiple lines 15 are set in a grid pattern. Furthermore, although the lines 15 are virtual lines, they can also be actually drawn lines.

[0027] [Structure of the laser irradiation unit] As shown in Figure 4, the laser irradiation unit 3 includes a light source 31, a spatial light modulator 32, and a focusing lens 33. The light source 31 outputs laser light L, for example, via 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 spatial light modulator (SLM) of a reflective liquid crystal on silicon (LCOS). The focusing lens 33 focuses the laser light L modulated by the spatial light modulator 32. The focusing lens 33 can also be a correction ring lens.

[0028] In this embodiment, the laser irradiation unit 3 irradiates the wafer 20 with laser light L from the surface 21b side of the semiconductor substrate 21 along multiple lines 15, thereby forming two rows of modified regions 12a and 12b inside the semiconductor substrate 21 along the multiple lines 15. Modified region 12a is the modified region closest to the back surface 21a among the two rows of modified regions 12a and 12b. Modified region 12b is the modified region closest to modified region 12a among the two rows of modified regions 12a and 12b, and is also the modified region closest to the surface 21b.

[0029] Two rows of modified regions 12a and 12b are adjacent in the thickness direction (Z direction) of wafer 20. These two rows of modified regions 12a and 12b are formed by moving two focusing points C1 and C2 relative to the semiconductor substrate 21 along line 15. The laser light L is modulated by a spatial light modulator 32, such that focusing point C2 is located behind focusing point C1 in the travel direction and on the incident side of the laser light L. The formation of the modified regions can be single-focus or multi-focus, and can involve one path or multiple paths.

[0030] Laser irradiation unit 3 irradiates the wafer 20 with laser light L from the surface 21b side of the semiconductor substrate 21 along each of the plurality of lines 15. As an example, this is relative to a single-crystal silicon with a thickness of 400 μm. <100> The semiconductor substrate 21 is used as a substrate. Two focusing points C1 and C2 are focused to positions 54 μm and 128 μm away from the back surface 21a, respectively. Laser light L is irradiated onto the wafer 20 from the surface 21b side of the semiconductor substrate 21 along each of the plurality of lines 15. At this time, for example, under the condition that the cracks 14 covering the two rows of modified regions 12a and 12b reach the back surface 21a of the semiconductor substrate 21, the wavelength of the laser light L is set to 1099 nm, the pulse width is 700 nm, and the repetition frequency is 120 kHz. In addition, the output of the laser light L from focusing point C1 is 2.7 W, the output of the laser light L from focusing point C2 is 2.7 W, and the relative moving speed of the two focusing points C1 and C2 relative to the semiconductor substrate 21 is 800 mm / s. For example, when the number of processing paths is 5, for the aforementioned wafer 20, ZH80 (position 328 μm away from back surface 21a), ZH69 (position 283 μm away from back surface 21a), ZH57 (position 234 μm away from back surface 21a), ZH26 (position 107 μm away from back surface 21a), and ZH12 (position 49.2 μm away from back surface 21a) can be used as processing positions. In this case, for example, the laser light L can have a wavelength of 1080 nm, a pulse width of 400 nsec, a repetition frequency of 100 kHz, and a movement speed of 490 mm / s.

[0031] The formation of these two rows of modified regions 12a, 12b and the crack 14 is carried out under the following conditions. That is, in subsequent steps, for example, the semiconductor substrate 21 is thinned by grinding the surface 21b of the semiconductor substrate 21 and the crack 14 is exposed to the surface 21b, and the wafer 20 is cut into multiple semiconductor elements along multiple lines 15.

[0032] [Structure of the inspection camera unit] As shown in Figure 5, the imaging unit 4 (imaging section) includes a light source 41, a reflector 42, an objective lens 43 (condenser lens), and a light detection unit 44. The imaging unit 4 photographs the wafer 20. Only a general overview of the imaging unit 4 is described here; a more detailed structure of the imaging unit 4 (specifically, the structure of the objective lens 43 equipped with the actuator 70 (see Figure 13)) 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, for example, composed of 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 reflector 42 and passes through the objective lens 43, illuminating the wafer 20 from the surface 21b side of the semiconductor substrate 21. The objective lens 43 functions as a condenser lens that focuses the light I1 output from the light source 41 onto the wafer 20 at a focusing position. At this time, the stage 2 supports the wafer 20, on which two rows of modified regions 12a and 12b are formed, as described above.

[0033] Objective lens 43 allows light I1 reflected from the back surface 21a of semiconductor substrate 21 to pass through. That is, objective lens 43 allows light I1 propagating within semiconductor substrate 21 to pass through. The numerical aperture (NA) of objective lens 43 is, for example, 0.45 or greater. Objective lens 43 has a correction ring 43a. The correction ring 43a corrects aberrations caused by light I1 within semiconductor substrate 21, for example, by adjusting the distance between the multiple lenses constituting objective lens 43. The aberration correction method is not limited to the correction ring 43a; other correction methods such as spatial light modulators can also be used. Light detection unit 44 detects light I1 (i.e., light propagating within wafer 20) transmitted from objective lens 43 and mirror 42. Light detection unit 44 is, for example, composed of an InGaAs camera, and detects light I1 in the near-infrared region. The method for detecting (photographing) light I1 in the near-infrared region is not limited to an InGaAs camera; other photographic methods such as transmission confocal microscopes that perform transmission-type photography can also be used.

[0034] The imaging unit 4 is capable of capturing images of the front ends of two rows of modified regions 12a and 12b, and multiple cracks 14a, 14b, 14c, and 14d (details described later). Crack 14a extends from modified region 12a toward the back side 21a. Crack 14b extends from modified region 12a toward the surface 21b. Crack 14c extends from modified region 12b toward the back side 21a. Crack 14d extends from modified region 12b toward the surface 21b.

[0035] [Structure of the camera unit for alignment and correction] As shown in Figure 6, the imaging unit 5 includes a light source 51, a reflector 52, a lens 53, and a light detection unit 54. The light source 51 outputs light I2 that is transmissive to the semiconductor substrate 21 of the wafer 20. The light source 51 is, for example, composed of a halogen lamp and a filter, and outputs light I2 in the near-infrared region. The light source 51 may also be common to the light source 41 of the imaging unit 4. The light I2 output from the light source 51 is reflected by the reflector 52 and passes through the lens 53, illuminating the wafer 20 from the surface 21b side of the semiconductor substrate 21.

[0036] Lens 53 allows light I2, which is reflected by the back surface 21a of the semiconductor substrate 21, to pass through. That is, lens 53 allows light I2 propagating within the semiconductor substrate 21 to pass through. The numerical aperture of 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 lens 53. Light detection unit 54 detects the light I2 passing through lens 53 and mirror 52. Light detection unit 54 is, for example, composed of an InGaAs imaging unit and detects light I2 in the near-infrared region.

[0037] Under the control of the control unit 8, the imaging unit 5 illuminates the wafer 20 with light I2 from the surface 21b side and detects the light I2 returning from the back side 21a (functional element layer 22), thereby capturing an image of the functional element layer 22. Also under the control of the control unit 8, the imaging unit 5 illuminates the wafer 20 with light I2 from the surface 21b side and detects the light I2 returning from the formation locations of the modified regions 12a and 12b of the semiconductor substrate 21, thereby acquiring an image of the region including the modified regions 12a and 12b. These images are used for calibration of the irradiation position of the laser light L. The imaging unit 6 has the same structure as the imaging unit 5, except that it has a lower magnification than the lens 53 (e.g., 6x in the imaging unit 5, 1.5x in the imaging unit 6), and is used for calibration in the same way.

[0038] [Examine the shooting principle of the camera unit] Using the imaging unit 4 shown in FIG5, as shown in FIG7, for the crack 14 spanning the two rows of modified regions 12a, 12b reaching the semiconductor substrate 21 on the back side 21a, the focal point F (the focal point of the objective lens 43) is moved from the surface 21b side to the back side 21a side. In this case, if the focal point F is focused from the surface 21b side to the tip 14e of the crack 14 extending from the modified region 12b to the surface 21b side, the tip 14e can be identified (image on the right side of FIG7). Hereinafter, the method of observing the tip 14e by focusing the focal point F on the tip 14e of the crack 14 is sometimes referred to as direct observation. However, even if the focal point F is focused from the surface 21b side to the crack 14 itself and the tip 14e of the crack 14 reaching the back side 21a, it cannot be identified (image on the left side of FIG7). On the other hand, if the focal point F is focused from the surface 21b side to the back side 21a of the semiconductor substrate 21, the functional element layer 22 can be identified.

[0039] Furthermore, using the imaging unit 4 shown in FIG5, as shown in FIG8, for the semiconductor substrate 21 where the crack 14 spanning the two rows of modified regions 12a and 12b does not reach the back surface 21a, the focus F is moved from the surface 21b side to the back surface 21a side. In this case, even if the focus F is focused from the surface 21b side to the tip 14e of the crack 14 extending from the modified region 12a to the back surface 21a side, the tip 14e cannot be identified (image on the left side of FIG8). However, if the focus F is focused from the surface 21b side to a region located on the opposite side of the back surface 21a (i.e., a region located on the functional element layer 22 side of the back surface 21a), and a virtual focus Fv symmetrical to the focus F is located on the tip 14e with respect to the back surface 21a, the tip 14e can be identified by the reflected light from the back surface 21a (image on the right side of FIG8). In addition, the virtual focus Fv is a point symmetrical to the focus F with respect to the back surface 21a, taking into account the refractive index of the semiconductor substrate 21. Hereinafter, the method of focusing the focal point F on the area opposite to the surface 21b relative to the back surface 21a and observing the front end 14e by means of back reflection is sometimes referred to as back reflection observation.

[0040] The inability to confirm the presence of crack 14 is presumably because the width of crack 14 is smaller than the wavelength of light I1, which serves as illumination. Figures 9 and 10 are SEM (Scanning Electron Microscope) images of the modified region 12 and crack 14 formed inside the semiconductor substrate 21, which is a silicon substrate. Figure 9(b) is a magnified image of region A1 shown in Figure 9(a), Figure 10(a) is a magnified image of region A2 shown in Figure 9(b), and Figure 10(b) is a magnified image of region A3 shown in Figure 10(a). Thus, the width of crack 14 is approximately 120 nm, which is smaller than the wavelength of light I1 in the near-infrared region (e.g., 1.1~1.2 μm).

[0041] The photographic principle conceived based on the above is as follows. As shown in Figure 11(a), if the focal point F is located in the air, light I1 will not return, thus obtaining a completely black image (the image on the right side of Figure 11(a)). As shown in Figure 11(b), if the focal point F is located inside the semiconductor substrate 21, light I1 reflected by the back surface 21a will return, thus obtaining a clean image (the image on the right side of Figure 11(b)). As shown in Figure 11(c), if the focal point F is focused from the surface 21b side to the modified region 12, the modified region 12 will cause absorption, scattering, etc., of a portion of the light I1 reflected by the back surface 21a, thus obtaining an image showing the black modified region 12 against a clean background (the image on the right side of Figure 11(c)).

[0042] As shown in Figures 12(a) and (b), if the focus F is focused from the surface 21b side to the tip 14e of the crack 14, then due to optical specificities (stress concentration, distortion, atomic density discontinuities, etc.) generated near the tip 14e, and the light being confined to the vicinity of the tip 14e, a portion of the light I1 reflected back from the back surface 21a will undergo scattering, reflection, interference, absorption, etc., thus obtaining an image where the tip 14e appears black against a clean background (the right-hand images of Figures 12(a) and (b)). As shown in Figure 12(c), if the focus F is focused from the surface 21b side to a portion other than the vicinity of the tip 14e of the crack 14, then at least a portion of the light I1 reflected from the back surface 21a will return, thus obtaining a clean image (the right-hand image of Figure 12(c)).

[0043] [Structure of the objective lens mounted on the actuator] Hereinafter, with reference to Figures 13 and 14, the objective lens 43 equipped with the actuator included in the imaging unit 4 will be described. Figure 13 is a structural diagram of the objective lens 43 equipped with the actuator 70.

[0044] As shown in Figure 13, the imaging unit 4, in addition to the structures shown in Figure 5, also includes an actuator 70. The actuator 70 is disposed (mounted) on the objective lens 43 and is an actuator that moves the objective lens 43 in the Z direction, which is the vertical direction. The actuator 70 is configured to move in the Z direction, thereby moving the objective lens 43 in the Z direction. The required range of motion of the actuator 70 is determined, for example, according to the width of the imaging area. The range of motion of the actuator 70 is set, for example, such that when the imaging unit 4 is fixed in a predetermined position by the drive unit 7 (details described later), the image is taken of the leading edge of the crack 14 extending from the modified region 12.

[0045] Now, as shown in Figure 13, two modified regions 12a and 12b are formed inside the wafer 20, and cracks 14 extend from the two modified regions 12a and 12b toward the surface 21b side and the back side 21a side of the wafer 20. In the example shown in Figure 13, the cracks 14 do not reach the surface 21b and the back side 21a of the wafer 20. In this case, in order to properly photograph the tip of the crack 14 extending from the modified region 12a, it is necessary to be able to directly observe the tip of the crack 14 extending from the modified region 12b on the surface 21b side (to make the tip of the crack 14 on the surface 21b side a focal point), and to be able to focus on a point opposite to the tip of the crack 14 on the surface 21b side relative to the back side 21a for back reflection observation (to make the point on the opposite side a focal point). In this case, the required range of motion of the actuator 70 is the "ACT range of motion" shown in Figure 13.

[0046] Furthermore, when the modified region 12 is formed in a fully cut state, such as when the crack 14 of the wafer 20 reaches the surface 21b and the back surface 21a, at least in the case where the modified region 12 is formed so that the crack 14 reaches the surface 21b, as shown in FIG14, in order to properly photograph the leading edge of the crack 14 extending from the modified region 12, it is necessary to be able to directly observe the leading edge of the crack 14 extending from the surface 21b side of the modified region 12a, 12b, 12c, 12d (so that the surface 21b can be the focal point) and to be able to focus the light on a point that is the opposite side of the back surface 21a to the surface 21b for back reflection observation (so that the point that is the opposite side can be the focal point). In this case, the required range of motion of the actuator 70 is the "ACT range of motion" shown in FIG14. For example, if the thickness of the wafer 20 made of silicon substrate is 400 μm, and the wafer 20 is in a fully cut state, the imaging range in silicon becomes 400 μm + 400 μm = 800 μm (including the area opposite to the back surface 21a, which becomes the surface 21b). In this case, it is preferable to consider the difference in refractive index so that the movable range of the actuator 70 in air is approximately 100 μm + 100 μm = 200 μm.

[0047] Photographic control using drive units and actuators Hereinafter, referring to Figures 15 to 18, the photographic control performed by the photographic unit 4 using the drive unit 7 (see Figure 1) and the actuator 70 will be described. In the laser processing apparatus 1, the drive unit 7 and the actuator 70 are controlled by the control unit 8 (see Figure 1) to photograph the interior of the wafer 20 while moving the focusing position of the photographic unit 4. In this photographic control, the drive unit 7 performs approximate focusing position alignment related to the photograph, and the actuator 70 performs detailed focusing position alignment related to the photograph. The drive unit 7 is a structure that supports the entire photographic unit 4 and moves the entire photographic unit 4 in the Z direction. The actuator 70 is a structure that is mounted in the photographic unit 4 with the objective lens 43 and moves the objective lens 43 in the Z direction.

[0048] Figure 15 is a schematic diagram illustrating the movement of the focusing position using the drive unit 7 and the actuator 70. The control unit 8 performs a first control (see Figure 15(a)) to move the imaging unit 4 to a position where the back surface 21a becomes the focusing position, and after the first control, controls the actuator 70 to move the objective lens 43 to a position where at least a portion of the area between the surface 21b and the back surface 21a, i.e., the first region 28, becomes the focusing position (see Figure 15(b)) and controls the actuator 70 to move the objective lens 43 to a position where at least a portion of the area opposite to the back surface 21a, i.e., the second region 29, becomes the focusing position (see Figure 15(c)). Alternatively, the back surface 21a becoming the focusing position may also include the area near the back surface 21a (e.g., an area within ±10 μm from the back surface 21a) becoming the focusing position.

[0049] Furthermore, before performing the first control, the control unit 8 performs pre-control of the actuator 70 by fixing the actuator 70 at the center position (center fixed) of the actuator 70's movable range in the Z direction. The center position of the movable range only needs to be near the center position of the movable range, for example, if the movable range of the actuator 70 is 80μm, a position of 40μm±10μm is sufficient.

[0050] In the first control, as shown in FIG15(a), under the control of the control unit 8, the drive unit 7 moves the entire imaging unit 4 such that the focusing position is on the back surface 21a. That is, the Z-axis is lowered to the vicinity of the back surface 21a. As described above, the actuator 70 is fixed in the center in the Z direction. Since the first region 28 and the second region 29, which are the imaging areas, are symmetrical with respect to the back surface 21a (that is, the back surface 21a is the center of the imaging area in the Z direction), the state in which the focusing position is on the back surface 21a when the actuator 70 is fixed in the center can be said to be a state in which the area that can be photographed is expanded to the maximum extent by the action of the actuator 70.

[0051] In the second control, as shown in FIG15(b), under the control of the control unit 8, firstly, the actuator 70 moves only the objective lens 43 such that the focusing position becomes the first region 28. Next, as shown in FIG15(c), under the control of the control unit 8, the actuator 70 moves only the objective lens 43 such that the focusing position becomes the second region 29. The control unit 8 can move the objective lens 43 by the actuator 70 in a manner that the entire area of ​​the first region 28 and the entire area of ​​the second region 29 in the Z direction are sequentially focused, or it can move the objective lens 43 by the actuator 70 in a manner that only a portion of the first region 28 and a portion of the second region 29 are sequentially focused. Furthermore, the control unit 8 can also move the objective lens 43 by the actuator 70 in a manner that the second region 29 is first focused, and then the first region 28 is focused. By implementing the second control, internal imaging of the wafer 20 in the first region 28 and the second region 29 is performed.

[0052] Figure 16 illustrates the details of the focusing position movement using the drive unit 7 and actuator 70. As shown in Figure 16(a), in cases where the thickness of wafer 20 differs from the intended thickness, it is assumed that the focusing position after the first control has deviated from the back surface 21a. Therefore, the control unit 8 performs a third control, that is, in the second control following the first control, it first controls the actuator 70 to move the position of the objective lens 43 in the Z direction while the region near the back surface 21a is the focusing position, and based on the light detection result performed by the light detection unit 44 in this state, it specifies the detailed position of the back surface 21a, and controls the actuator 70 to move the objective lens 43 to the position where the specified detailed position of the back surface 21a becomes the focusing position, i.e., the reference position (see Figure 16(b)). The region near the back surface 21a here can also be a region that includes the entire range of focusing positions that can deviate from the back surface 21a after the first control.

[0053] In the third control, under the control of the control unit 8, the actuator 70 moves only the objective lens 43 in such a way that the focusing position after the first control moves in the Z direction. By continuously changing the focusing position in the Z direction in this way, photography near the back surface 21a is performed. The control unit 8 may also detect the element pattern on the back surface 21a based on the signal from the light detection unit 44 as a result of photography, and determine the detailed position of the back surface 21a based on the element pattern. Alternatively, the control unit 8 may determine the detailed position of the back surface 21a from the specific information obtained by direct observation and back reflection observation of the crack 14 originating from the modified region 12 near the back surface 21a based on the signal from the light detection unit 44. Then, under the control of the control unit 8, the actuator 70 moves the objective lens 43 to a position where the detailed position of the back surface 21a becomes the focusing position, i.e., a reference 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 of the back surface 21a, so that the focusing position is properly positioned.

[0054] The control unit 8 performs a fourth control, namely, in the second control, it controls the actuator 70 to move the objective lens 43 from the aforementioned reference position to a position in which at least a portion of the first region 28 becomes a focusing position (see Figure 16(d)), and controls the actuator 70 to move the objective lens 43 from the reference position to a position in which at least a portion of the second region 29 becomes a focusing position (see Figure 16(c)). The control unit 8 can move the objective lens 43 by the actuator 70 in a manner that makes the entire area of ​​the first region 28 and the entire area of ​​the second region 29 in the Z direction a sequential focusing position, or it can move the objective lens 43 by the actuator 70 in a manner that makes only a portion of the first region 28 and a portion of the second region 29 a sequential focusing position.

[0055] Thus, in the manner shown in Figure 16, the objective lens 43 is moved to a reference position that serves as the starting position for photography by the first and third controls, and the interior of the wafer 20 is photographed by the subsequent fourth control, and information about the modified region 12 is output (e.g., detection of the leading edge position of the crack 14).

[0056] Figure 17 is a flowchart of an example of an observation method implemented in the laser processing apparatus 1. Hereinafter, an example of the observation method will be described with reference to Figures 17 and 16.

[0057] As shown in Figure 17, firstly, the actuator 70 is controlled by the control unit 8 to fix the actuator 70 at the center position of its movable range in the Z direction (step S1: preliminary process). Alternatively, this center fixing of the actuator 70 can also be performed manually.

[0058] Next, the control unit 8, as shown in FIG16(a), controls the drive unit 7 to move the camera unit 4 to a position where the back surface 21a becomes a light-focusing position (step S2: first process).

[0059] Next, the control unit 8 controls the actuator 70 to move the position of the objective lens 43 in the Z direction when the area near the back surface 21a is in a focusing position. Based on the detection result of the light detection unit 44 in this state, the actuator 70 controls the movement of the objective lens 43 to a position, i.e., a reference position, where the specified detailed position of the back surface 21a becomes the focusing position, as shown in FIG16(b). That is, the focusing position is corrected based on the detection result (step S3: second process).

[0060] Next, the actuator 70 is controlled by the control unit 8, as shown in FIG16(c), to move the objective lens 43 to a position where the second region 29, which is the observation area on the back side, becomes a focusing position (step S4: second process). Then, the actuator 70 is controlled by the control unit 8, as shown in FIG16(d), to move the objective lens 43 to a position where the first region 28, which is the observation area on the surface, becomes a focusing position (step S5: second process). The above is an example of an observation method.

[0061] Furthermore, the observation method implemented by the laser processing apparatus 1 is not limited to the methods shown in Figures 16 and 17. Figure 18 is a diagram illustrating in detail another example of focusing position movement using the drive unit 7 and the actuator 70. In the configuration shown in Figure 18, the first control described above (refer to Figure 18(a)) and the third control described above (refer to Figure 18(b)) are implemented in the second control following the first control, just as in the configuration shown in Figure 16. That is, the control shown in Figure 18(a) corresponds to the control shown in Figure 16(a), and the control shown in Figure 18(b) corresponds to the control shown in Figure 16(b). Here, in the configuration shown in Figure 16, although the photographic result near the back surface 21a is obtained in the third control for determining the reference position (refer to Figure 16(b)), this photographic result is only used to determine the reference position and is not used as information related to the output of information related to the modified region 12 of the wafer 20. Regarding this, in the manner shown in Figure 18, the photographic results obtained in the third control (refer to (b)) near the back surface 21a are used not only as information related to the output of the reference position, but also as information related to the output of information related to the modified region 12 of the wafer 20. In this way, by effectively utilizing the photographic results of the third control, repeated photographic processing of the same area can be avoided, and photographic processing can be carried out more efficiently.

[0062] Now, in the third control used to determine the reference position (see Figure 18(b)), the imaging result of region A1 near the back surface 21a (see Figure 18(c)) is obtained. In this case, the control unit 8 performs the fifth control, that is, controls the drive unit 7 to move the entire imaging unit 4 to a position where at least a portion of the un-imaged area other than region A1, which is not a focal point position when the region within the first region 28 or the second region 29 is the specific position of the back surface 21a in the third control, becomes a focal point position. In the example shown in Figure 18, the un-imaged area of ​​the second region 29 is a region that does not need to be imaged. In this case, the control unit 8 controls the drive unit 7 to move the entire imaging unit 4 to a position where region A2, which is the un-imaged area of ​​the first region 28, becomes a focal point position (pushing upwards). More specifically, the control unit 8 considers the range of motion of the actuator 70 and controls the drive unit 7 to move the entire imaging unit 4 to a position where region A2 becomes a focal point position by means of the sixth control described later, which moves the objective lens 43 by the actuator 70.

[0063] Then, the control unit 8 performs a sixth control, that is, it uses the position of the objective lens 43 of the imaging unit 4 after the fifth control as a new reference position, and controls the actuator 70 to move the objective lens 43 to a position that makes region A2, which is included in the un-photographed area, a focusing position. The control unit 8 can move the objective lens 43 by the actuator 70 in a way that makes the entire region A2 in the Z direction a sequential focusing position, or it can move the objective lens 43 by the actuator 70 in a way that makes only a part of region A2 a sequential focusing position.

[0064] Thus, in the configuration shown in Figure 18, the fifth and sixth controls are implemented so that the photographic results obtained in the third control are used not only as information related to the output of the reference position but also as information related to the output of information related to the modified region 12 of the wafer 20. This allows for efficient photographic execution by photographing only areas where photographic results cannot be obtained in the third control. Furthermore, even if the desired photographic area is not entirely within the movable range of the actuator 70, the fifth and sixth controls can be implemented (multiple times as needed) to sequentially expand the photographic area and photograph the entire desired area.

[0065] [Effects] The effects of the laser processing apparatus 1 (observation apparatus) and observation method involved in this embodiment will be explained below.

[0066] 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. It is characterized by comprising: a photographic unit 4 having a light source 41 that outputs transmissive light to the wafer 20, an objective lens 43 that focuses the light output from the light source 41 onto a focusing position on the wafer 20, and a light detection unit 44 that detects light propagating in the wafer 20; a drive unit 7 that supports the photographic unit 4 and moves the photographic unit 4 in the Z direction, which is the vertical direction; and a drive unit 7 that is provided with the objective lens 43 and moves the objective lens 43 in the vertical direction. The actuator 70 moves in the Z direction; and the control unit 8 performs: a first control to move the camera unit 4 to a position where the back surface 21a becomes a focusing position; and a second control, after the first control, to move the objective lens 43 to a position where at least a portion of the area between the back surface 21a and the surface 21b, i.e., the first region 28, becomes a focusing position, and to move the objective lens 43 to a position where at least a portion of the area opposite to the back surface 21a and the surface 21b, i.e., the second region 29, becomes a focusing position.

[0067] In such a laser processing apparatus 1, during the observation of a wafer 20 with the modified region 12 formed thereon, a drive unit 7 that moves the imaging unit 4 in the Z direction is controlled to move the imaging unit 4 to a position where the back surface 21a of the wafer 20 becomes a focusing position. Then, an actuator 70 that moves the objective lens 43 in the Z direction is controlled to move the objective lens 43 to a position where the region between the back surface 21a and the surface 21b, i.e., the first region 28, becomes a focusing position, and the objective lens 43 is also moved to a position where the region opposite to the back surface 21a, i.e., the second region 29, becomes a focusing position. In this way, by moving the objective lens 43 so that both the first region 28 and the second region 29 become focusing positions, it is possible to appropriately perform both direct observation of cracks 14 originating from the modified region 12 when the first region 28 is a focusing position, and observation of cracks 14 using back reflection when the second region 29 is a focusing position. Furthermore, by moving the objective lens 43 of the first region 28 and the second region 29 to a focusing position using only the actuator 70 that moves the objective lens 43 of the imaging unit 4, the focusing position movement can be performed at high speed compared to moving the entire imaging unit 4, and vibration after movement can also be suppressed. Here, the laser processing apparatus 1 of this embodiment includes a drive unit 7 that moves the entire imaging unit 4 in the Z direction and an actuator 70 that 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, approximate alignment can be performed by the drive unit 7 and detailed alignment can be performed by the actuator 70. Compared to the case where the entire movement in the Z direction is performed by the actuator that can achieve detailed alignment, the apparatus cost can be reduced, and high-precision alignment (focusing alignment of the imaging range, etc.) can be performed. In the laser processing apparatus 1 of this embodiment, firstly, the imaging unit 4 is controlled by the drive unit 7 to make the back surface 21a, which is the boundary surface of the first region 28 and the second region 29, a focusing position. Then, the objective lens 43 is controlled by the actuator 70 to make the first region 28 and the second region 29 focus positions respectively. Before the control by the actuator 70 begins, by aligning the focusing position with the back surface 21a (the boundary surface of the first region 28 and the second region 29), the movable range of the actuator 70 can be maximized, and high-speed movement of the objective lens 43 to make the first region 28 and the second region 29 focus positions can be appropriately implemented. As described above, the laser processing apparatus 1 according to this embodiment can perform high-speed focusing position movement, thereby improving the imaging cycle time.

[0068] The control unit 8 can also perform pre-control of the actuator 70 before the first control, by fixing the actuator 70 at the center position of its movable range in the Z direction. Thus, the second control can be implemented while the actuator 70 is fully movable in both directions (up and down) of the Z direction, maximizing the utilization of the actuator 70's movable range and appropriately implementing high-speed movement of the objective lens 43 to achieve a focusing position in the first region 28 and the second region 29.

[0069] The control unit 8 can also implement the following in the second control: a third control, which controls the actuator 70 to move the position of the objective lens 43 in the Z direction when the region near the back surface 21a is a focusing position, based on the light detection result of the light detection unit 44 in this state, to determine the detailed position of the back surface 21a, and controls the actuator 70 to move the objective lens 43 to a position where the specified detailed position of the back surface 21a becomes a focusing position, i.e., a reference position; and a fourth control, which controls the actuator 70 to move the objective lens 43 from the reference position to a position where at least a portion of the first region 28 becomes a focusing position, and controls the actuator 70 to move the objective lens 43 from the reference position to a position where at least a portion of the second region 29 becomes a focusing position. Even with the first control, for example, in cases where the actual thickness of the wafer 20 differs from the intended thickness, the focusing position is still considered to deviate from the back surface 21a. In this case, there is a problem that the imaging of the first region 28 and the second region 29, which have the maximum range of motion of the actuator 70, cannot be achieved. In this regard, in the second control, the specific position of the back surface 21a is used as a reference position based on the light detection result (third control). The objective lens 43 is moved from the reference position to the imaging range of the first region 28 and the second region 29 by the actuator 70 (fourth control). Thus, even if the focusing position deviates from the back surface 21a in the first control, the reference position can be set appropriately to achieve imaging of the first region 28 and the second region 29 with maximum utilization of the movable range of the actuator 70.

[0070] The control unit 8 can also implement the following in the second control: a third control, which controls the actuator 70 to move the position of the objective lens 43 in the Z direction when the area near the back surface 21a is a focusing position, based on the light detection result of the light detection unit 44 in this state, to determine the detailed position of the specific back surface 21a, and controls the actuator 70 to move the objective lens 43 to a position where the specific detailed position of the back surface 21a becomes a focusing position, i.e., a reference position. Furthermore, the control unit 8 also implements: a fifth control, which controls the drive unit 7 to move the imaging unit 4 to a position where at least a portion of the area within the first region 28 or the second region 29, which was not a focusing position when the specific detailed position of the back surface 21a was determined in the third control, becomes a focusing position; and a sixth control, which controls the actuator 70 to move the objective lens 43 to a position where the area included in the un-photographed area becomes a focusing position, using the position of the objective lens 43 of the imaging unit 4 after the fifth control as a new reference position. According to the third control, during the process of determining the detailed position of the specific back surface 21a, photography near the back surface 21a can be performed. Therefore, in this observation device 1, the drive unit 7 is controlled (fifth control) to move the imaging unit 4 to a position where the un-imaged area not imaged in the third control becomes the focusing position, and the actuator 70 is controlled (sixth control) to make the position of the objective lens 43 after the fifth control a new reference position and move the objective lens 43 to a position where the unimaged area becomes the focusing position. With this structure, because control is performed to make the area not imaged in the third control a focusing position, invalid imaging is avoided, thus enabling more efficient imaging. Furthermore, with this structure, even if the area to be imaged is not within the range of motion of the actuator 70 at the initial reference position, the area to be imaged can be reliably imaged by changing the reference position.

[0071] The observation method of this embodiment is a 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. It is characterized by comprising: a first step of moving the imaging unit 4 to a position where the back surface 21a becomes a focusing position by a drive unit 7 that moves the imaging unit 4 in the Z direction (vertical direction); and a second step of moving the objective lens 43 included in the imaging unit 4 to a position where at least a portion of the region between the back surface 21a and the surface 21b, i.e., a first region 28, becomes a focusing position by an actuator 70 that moves the objective lens 43 in the Z direction, and further moving the objective lens 43 to a position where at least a portion of the region opposite to the back surface 21a (the side opposite to the surface 21b), i.e., a second region 29, becomes a focusing position. According to the observation method of this embodiment, the focusing position movement can be performed at high speed, thereby improving the imaging cycle time.

[0072] The above observation method can also be further included in a pre-processing step before the first step, in which the actuator 70 is fixed at the center of its movable range in the Z direction. With such a structure, the movable range of the actuator 70 can be maximized, and high-speed movement of the objective lens 43, which makes the first region 28 and the second region 29 the focusing position, can be appropriately implemented.

[0073] 1: Laser processing equipment 2: Platform 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 Zone 12b: Modified region 12s: Change in particle size 14: Cracks 14a: Cracks 14b: Cracks 14c: Cracks 14d: Cracks 14e: Frontend 15: Line 20: Wafer 21: Semiconductor substrate 21a: Back 21b: Surface 21c: Gap 22: Functional Component Layer 22a: Functional element 23: Grid area 28: Area 1 29: Second Area 31: Light source 32: Spatial Light Modulator 33: Condensing Lens 41: Light source 42: Reflector 43: Objective lens 43a: Calibration ring 44: Optical Detection Department 51: Light source 52: Reflector 53: Lens 54: Optical Detection Department 70: Actuator 150: Monitor A1: Area A2: Area A3: Area C: Focusing point C1: Focusing point C2: Focusing point L: Laser light I1: Light I2: Light F: Focus Fv: Virtual Focus

Claims

1. An observation apparatus, characterized in that: it is an observation apparatus 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, comprising: a photographic unit having a light source that outputs transmissive light to the wafer, a focusing lens that focuses the light output from the light source onto a focusing position on the wafer, and a light detection unit that detects light propagating in the wafer; a driving unit that supports the photographic unit and moves the photographic unit in a Z direction, which is a vertical direction; an actuator that is disposed on the focusing lens and moves the focusing lens in the Z direction; and a control unit configured to perform control as follows: The first control moves the aforementioned driving unit to a position where the aforementioned photographic unit is positioned such that the aforementioned second surface becomes the aforementioned focusing position; and the second control, after the aforementioned first control, moves the aforementioned condenser lens to a position where at least a portion of a first region, which is the area between the aforementioned second surface and the aforementioned first surface, becomes the aforementioned focusing position, and moves the aforementioned condenser lens to a position where at least a portion of a second region, which is the area opposite to the aforementioned first surface relative to the aforementioned second surface, becomes the aforementioned focusing position.

2. The observation apparatus as described in claim 1, wherein: Prior to the first control, the aforementioned control unit further performs: pre-control, which controls the aforementioned actuator in such a way that the aforementioned actuator is fixed at the center position of the aforementioned actuator's movable range in the Z direction.

3. The observation apparatus as described in claim 1 or 2, wherein: The aforementioned control unit is configured in the aforementioned second control in such a manner as follows: a third control, which controls the actuator to move the position of the condenser lens in the aforementioned Z direction when the region of the aforementioned first region or the aforementioned second region that is biased against the aforementioned second surface becomes the aforementioned focusing position, and controls the actuator to move the condenser lens to a reference position that makes the specified detailed position of the aforementioned second surface become the aforementioned focusing position; and a fourth control, which controls the actuator to move the condenser lens from the aforementioned reference position to a position that makes at least a portion of the aforementioned first region become the aforementioned focusing position, and controls the actuator to move the condenser lens from the aforementioned reference position to a position that makes at least a portion of the aforementioned second region become the aforementioned focusing position.

4. The observation apparatus as described in claim 1 or 2, wherein: The aforementioned control unit is configured in the aforementioned second control in a manner that performs the following control: Third control, which controls the actuator to move the position of the condenser lens in the aforementioned Z direction when the region of the aforementioned first region or the aforementioned second region that is biased against the aforementioned second surface becomes the aforementioned focusing position, and controls the actuator to move the condenser lens to a reference position that makes the specified detailed position of the aforementioned second surface become the aforementioned focusing position. The control unit is also configured to perform the following control: Fifth control, which controls the drive unit to move the aforementioned imaging unit to a position that makes at least a portion of the un-imaged area become the aforementioned focusing position, where the un-imaged area is a region within the aforementioned first region or the aforementioned second region and is not a region that was not a aforementioned focusing position when the specified detailed position of the aforementioned second surface was determined in the aforementioned third control; and Sixth control, which controls the actuator to move the condenser lens of the aforementioned imaging unit after the aforementioned fifth control to a position that makes a region contained in the aforementioned un-imaged area become the aforementioned focusing position, using the position of the condenser lens of the aforementioned imaging unit after the aforementioned fifth control as the new aforementioned reference position.

5. An observation method, characterized in that: it is an observation method for a wafer having a first surface and a second surface, and having a modified region formed internally by irradiating laser light from the first surface side, comprising: In the first step, the camera unit is moved to a position where the second surface becomes a focusing position by a drive unit that moves the camera unit in the Z direction (vertical direction). In the second step, the focusing lens is moved to a position where at least a portion of a first region between the second surface and the first surface becomes the focusing position by an actuator that moves the focusing lens included in the camera unit in the Z direction, and the focusing lens is moved to a position where at least a portion of a second region opposite to the first surface becomes the focusing position.

6. The observation method as described in claim 5, wherein: Also includes: In the preliminary process, prior to the first process, the actuator is controlled in such a way that it is fixed at the center of the actuator's movable range in the Z direction.

Images