Observation apparatus and observation method

Abstract

The laser processing apparatus of the present invention comprises: an imaging unit having a light source, an objective lens, and a light detection unit; a drive unit for moving the imaging 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 imaging unit to a position where 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 where a first region, i.e., the area between the back surface and the surface, becomes a focusing position, and to control the actuator to move the objective lens to a position where a second region, i.e., the area opposite 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. Background 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 camera unit (e.g., an infrared camera) capable of observing 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, resulting in a larger imaging area. Normally, the camera unit is moved vertically (Z-direction) by a control unit that moves the entire camera unit. However, with the larger 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 imaging cycle time. Furthermore, even if high-speed focal point movement is achieved, the vibration after the entire camera unit moves at high speed is difficult to calm, and imaging cannot be performed until the vibration subsides, resulting in a decrease in imaging cycle time.

[0004] One aspect of the present invention is made in view of the above circumstances, and relates to an observation device and observation method capable of improving the camera's beat.

[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, wherein a modified region is formed inside the wafer by irradiating it with a laser from the first surface side. The apparatus is characterized by comprising: an imaging 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 the wafer at a focusing position, and a light detection unit that detects light propagating in the wafer; a drive unit that supports the imaging unit and moves the imaging 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 imaging 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 an 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 a 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 such that both the first and second regions become focusing positions, it is possible to appropriately and simultaneously perform direct observation of cracks originating from the modified region when the first region is a focusing position, and observation of cracks through reflection from the back surface (second surface) when the second region is a focusing position. Furthermore, by moving the condenser lens to focus the first and second regions using an actuator that moves only the condenser lens of the camera unit, the focusing position movement can be performed at high speed compared to moving the entire camera unit, and vibrations after movement can be suppressed. Here, an observation device according to one aspect of the present invention includes a drive unit that moves the entire camera unit in the Z direction and an actuator that moves the condenser lens of the camera unit in the Z direction. By simultaneously providing the drive unit and the actuator, for example, approximate alignment can be performed by the drive unit and detailed alignment by the actuator, thus reducing device costs and achieving high-precision alignment (focusing alignment of the imaging range, etc.). In an observation device according to one aspect of the present invention, firstly, the camera unit of the drive unit is controlled to focus the light on the second surface, which is the boundary between the first and second regions; then, the condenser lens is controlled by the actuator to focus the light on the first and second regions respectively. Before control via the actuator begins, by aligning the focusing position with the second surface (the boundary between the first and second regions), the high-speed movement of the focusing lens, which positions the first and second regions as focusing points, can be appropriately implemented within the maximum range of motion of the actuator. As described above, the observation device according to one aspect of the invention enables high-speed movement of the focusing position, thereby improving the camera's shooting speed.

[0007] The control unit can also perform pre-control of the actuator by fixing the actuator at the center position of the actuator's 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, so as to maximize the high-speed movement of the focusing lens that sets the first and second regions as focusing positions by utilizing the actuator's movable range to the maximum extent.

[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 so that 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 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, if the actual wafer thickness differs from the intended thickness, the focusing position is considered to deviate from the second surface. In this case, there is a problem that imaging of the first and second regions, which maximize the range of motion of the actuator described above, cannot be achieved. 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 the maximum range of motion of the actuator.

[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 camera unit to a position where at least a portion of the region not being a focusing position (i.e., the un-photographed region) within the first or second region and the specific detailed position of the second surface in the third control becomes a focusing position; and a sixth control, which controls the actuator to move the condenser lens 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 camera unit after the fifth control as a new reference position. According to the third control, imaging 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 (fifth control) is controlled to move the camera unit to a position where the un-photographed area not photographed in the third control becomes a focusing position, and the actuator (sixth control) is controlled to move the focusing lens to a position where the un-photographed area becomes a focusing position after the fifth control, making the position of the focusing lens after the fifth control a new reference position. With this structure, because control is performed to make the area not photographed in the third control a focusing position, ineffective photography is avoided, thus enabling more efficient photography. Furthermore, with this structure, even if the area to be photographed is not within the actuator's range of motion at the initial reference position, the area to be photographed can be reliably photographed by changing the reference position.

[0010] One aspect 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 internally by irradiating the first surface with a laser. The method is characterized by comprising: a first step of moving the camera unit 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); and a second step of moving the focusing lens included in the camera 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 camera unit in the Z direction, and further 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 present invention, the focusing position movement can be performed at high speed, thereby improving the camera cycle time.

[0011] The aforementioned observation method may also include a pre-processing step before the first process, in which the actuator is fixed at the center of its movable range in the Z direction. With this structure, high-speed movement of the focusing lens, which positions the first and second regions as focusing points, can be appropriately implemented to the maximum extent possible within the movable range of the actuator.

[0012] According to one aspect of the present invention, even in situations with a large camera area, the focus position can be moved at high speed, thereby improving the camera's shooting speed. Attached Figure Description

[0013] Figure 1 This is a structural diagram of a laser processing apparatus according to one implementation method. Figure 2 This is a top view of a wafer in one implementation method. Figure 3 yes Figure 2 A cross-sectional view of a portion of the wafer shown. Figure 4 yes Figure 1 The diagram shows the structure of the laser irradiation unit. Figure 5 yes Figure 1 The diagram shown is a structural diagram of the inspection camera unit. Figure 6 yes Figure 1 The diagram shows the structure of the camera unit used for alignment correction. Figure 7 It is used for explanation Figure 5 The image shown is a cross-sectional view of the wafer based on the imaging principle of the inspection camera unit, and images of the inspection camera unit at various locations. Figure 8 It is used for explanation Figure 5 The image shown is a cross-sectional view of the wafer based on the imaging principle of the inspection camera unit, and images of the inspection camera unit at various locations. Figure 9 These are SEM images of the modified regions and cracks formed inside the semiconductor substrate. Figure 10 These are SEM images of the modified regions and cracks formed inside the semiconductor substrate. Figure 11 It is used for explanation Figure 5 The diagram shows the optical path of the inspection camera unit and the schematic diagram showing the image at the focal point of the inspection camera unit. Figure 12 It is used for explanation Figure 5 The diagram shows the optical path of the inspection camera unit and the schematic diagram showing the image at the focal point of the inspection camera unit. Figure 13This is a structural diagram of the objective lens equipped with an actuator. Figure 14 This is a structural diagram of the objective lens equipped with an actuator. Figure 15 This is a diagram illustrating the general outline of the focusing position movement performed by the drive unit and actuator. Figure 16 This diagram illustrates in detail the movement of the focusing position via the drive unit and actuator. Figure 17 This is a flowchart of an example of an observation method. Figure 18 This diagram illustrates in detail the movement of the focusing position via the drive unit and actuator. Detailed Implementation

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

[0015] like Figure 1 As shown, the laser processing apparatus 1 includes a stage 2, a laser irradiation unit 3, multiple camera 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 a laser 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 mounting stage 2 supports the object 11, for example, by adsorbing and attaching a film to the object 11. The mounting stage 2 is movable along the X and Y directions respectively, and is rotatable about an axis parallel to the Z direction. 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 transmissive laser L onto the object 11. When the laser L is focused into the interior of the object 11 supported by the stage 2, the laser L is particularly absorbed in the part corresponding to the focusing point C of the laser L, thus forming a modified region 12 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-treated 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 incident side of the laser L 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 modification points 12s are formed in a row along the X direction. Each modification point 12s is formed by irradiation with a single pulse of laser L. A row of modification regions 12 is a collection of multiple modification points 12s arranged in a row. Adjacent modification points 12s may be connected to each other or separated from each other, depending on the relative moving speed of the focusing point C relative to the object 11 and the repetition frequency of the laser L.

[0020] The camera unit 4 captures images of 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, camera units 5 and 6 photograph the object 11 supported by the platform 2 by transmitting light through the object 11. The images obtained by camera units 5 and 6 are used, for example, to align the position of the laser L.

[0022] The drive unit 7 supports the laser irradiation unit 3 and multiple camera units 4, 5, and 6. The drive unit 7 causes the laser irradiation unit 3 and the multiple camera 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 camera 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 device, and communication device. In the control unit 8, the processor executes software (programs) read from memory, controls the reading and writing of data in memory and storage devices, and controls 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 is as follows: Figure 2 and Figure 3The image shows 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 including the functional element layer 22; however, the wafer 20 may or may not include the 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 three-dimensionally. Furthermore, 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 line region 23. The grid line 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] like Figure 4 As shown, 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 L along multiple lines 15 from the surface 21b side of the semiconductor substrate 21, thereby forming two rows of modified regions 12a and 12b along the multiple lines 15 inside the semiconductor substrate 21. 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 L is modulated by a spatial light modulator 32, such that focusing point C2 is positioned behind focusing point C1 in the travel direction and on the incident side of laser L. The formation of the modified regions can be single-focus or multi-focus, and can involve one path or multiple paths.

[0030] The laser irradiation unit 3 irradiates the wafer 20 with laser 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 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 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 laser L is set to 1099 nm, the pulse width is 700 nm, and the repetition frequency is 120 kHz. In addition, the output of laser L at focusing point C1 is 2.7 W, the output of laser L at 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 wavelength of laser L can be 1080 nm, the pulse width can be 400 nsec, the repetition frequency can be 100 kHz, and the moving speed can be 490 mm / s.

[0031] The formation of such two rows of modified regions 12a, 12b and cracks 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 cracks 14 are exposed to the surface 21b, and the wafer 20 is cut into multiple semiconductor devices along multiple lines 15.

[0032] [Inspection of the structure of the camera unit] like Figure 5 As shown, 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 captures images of the wafer 20. Furthermore, only a general overview of the imaging unit 4 will be described here; a more detailed structure of the imaging unit 4 (specifically, it includes an actuator 70 (see reference...)) is required. Figure 13 The structure of the objective lens 43 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, for example, is 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 mirror 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 focusing lens that concentrates the light I1 output from the light source 41 onto the wafer 20. 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 is used to focus transmissive light I1 relative to semiconductor substrate 21 toward semiconductor substrate 21. Objective lens 43 allows light I1 reflected by the back surface 21a of semiconductor substrate 21 to pass through. That is, objective lens 43 allows light I1 propagating in 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 in semiconductor substrate 21, for example, by adjusting the distance between the plurality of lenses constituting objective lens 43. The means of correcting aberrations is not limited to correction ring 43a, but may also be other correction means such as spatial light modulator. Light detection unit 44 detects light I1 (i.e., light propagating in 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. Among them, the means of detecting (photographing) light I1 in the near-infrared region is not limited to InGaAs cameras, but can also be other imaging means of transmission imaging, such as transmission confocal microscopes.

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

[0035] [Structure of the camera unit for alignment and correction] like Figure 6 As shown, 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, an InGaAs camera, and detects light I2 in the near-infrared region.

[0037] 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 back surface 21a (functional element layer 22), thereby capturing an image of the functional element layer 22. Similarly, 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 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 aligning the irradiation position of the laser L. The imaging unit 6 has the same structure as the imaging unit 5, except that it has a lower magnification (e.g., 6x in the imaging unit 5, 1.5x in the imaging unit 6) compared to the lens 53, and is used for alignment in the same way.

[0038] [Inspection of the shooting principle of the camera unit] use Figure 5 The camera unit 4 shown is as follows: Figure 7As shown, for the crack 14 spanning the two rows of modified regions 12a and 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 ( Figure 7 (Image on the right). Hereinafter, the method of focusing the focal point F on the front end 14e of the crack 14 to observe the front end 14e 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 to the front end 14e of the crack 14 on the back side 21a, confirmation cannot be made ( Figure 7 (Image on the left). In addition, if the focus F is shifted from the surface 21b side to the back surface 21a of the semiconductor substrate 21, the functional element layer 22 can be identified.

[0039] And, using Figure 5 The camera unit 4 shown is as follows: Figure 8 As shown, 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. Figure 8 (Image on the left). 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., the region located on the functional element layer 22 side relative to the back surface 21a), and a virtual focus Fv symmetrical to the focus F about the back surface 21a is located at the front end 14e, then the front end 14e can be confirmed by the reflected light from the back surface 21a. Figure 8 (Image on the right). Additionally, the virtual focus Fv is a point symmetrical to the focus F about the back surface 21a, taking into account the refractive index of the semiconductor substrate 21. Hereinafter, the method of focusing the focus F to a region located on the opposite side of the surface 21b relative to the back surface 21a and observing the front end 14e by back reflection is sometimes referred to as back reflection observation.

[0040] The inability to confirm crack 14 as described above is presumably because the width of crack 14 is smaller than the wavelength of light I1, which serves as illumination. Figure 9 and Figure 10 It is a SEM (Scanning Electron Microscope) image of the modified region 12 and the crack 14 formed inside the semiconductor substrate 21, which is a silicon substrate. Figure 9 (b) is Figure 9 A magnified image of region A1 shown in (a), Figure 10 (a) is Figure 9 A magnified image of region A2 shown in (b). Figure 10 (b) is Figure 10 A magnified image of region A3 shown in (a). Thus, the width of the crack 14 is about 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 camera principle envisioned based on the above is as follows. Figure 11 As shown in (a), if the focal point F is placed in the air, light I1 will not return, thus resulting in a completely black image. Figure 11 (Image to the right of (a)). Figure 11 As shown in (b), if the focal point F is located inside the semiconductor substrate 21, the light I1 reflected by the back surface 21a will return, thus obtaining a clean image. Figure 11 (Image to the right of (b)). Figure 11 As shown in (c), if the focus F is focused from the surface 21b side onto the modified region 12, the modified region 12 will cause absorption and scattering of a portion of the light I1 reflected back from the back surface 21a, resulting in an image where the modified region 12 appears completely black against a clean white background. Figure 11 (Image to the right of (c)).

[0042] like Figure 12 As shown in (a) and (b), if the focal point F is focused from the surface 21b side to the front end 14e of the crack 14, then, for example, due to optical specificities (stress concentration, distortion, atomic density discontinuity, etc.) generated near the front end 14e, and the light being confined near the front end 14e, a portion of the light I1 reflected back from the back surface 21a will undergo scattering, reflection, interference, absorption, etc., so an image will be obtained in which the front end 14e is displayed as black against a clean white background. Figure 12 (Images to the right of (a) and (b)). Figure 12 As shown in (c), if the focus F is adjusted from the surface 21b side to a portion beyond the vicinity of the front end 14e of the crack 14, at least a portion of the light I1 reflected by the back surface 21a will return, thus obtaining a clean image. Figure 12 (Image to the right of (c)).

[0043] [Structure of the objective lens mounted on the actuator] The following is for reference Figure 13 and Figure 14 This indicates that the objective lens 43, which includes the camera unit 4, is mounted on the actuator. Figure 13 This is a structural diagram of the objective lens 43 equipped with actuator 70.

[0044] like Figure 13 As shown, the camera unit 4 includes, in addition to Figure 5 In addition to the structures shown, an actuator 70 is also included. 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, with the imaging unit 4 fixed in a predetermined position by the drive unit 7 (details described later), the image is captured from the leading edge of the crack 14 extending from the modified region 12.

[0045] Now, as Figure 13 As shown, 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. Figure 13 In the example shown, the crack 14 does not reach the surface 21b and back surface 21a of the wafer 20. In this case, in order to properly image 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 modified region 12b on the surface 21b side (to make the leading edge of the crack 14 on the surface 21b side a focal point), and to be able to focus on a point opposite to the leading edge of the crack 14 on the surface 21b side relative to the back surface 21a for back reflection observation (to make that opposite point a focal point). In this case, the required range of motion of the actuator 70 becomes... Figure 13 The "ACT movable range" is shown.

[0046] Furthermore, in cases where the modified region 12 is formed in a manner such that the crack 14 of the wafer 20 reaches both the surface 21b and the back surface 21a (i.e., in a fully cut state), at least the modified region 12 is formed in a manner such that the crack 14 reaches the surface 21b, as... Figure 14 As shown, 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 extending from the outermost surface 21b side of the modified region 12a, 12b, 12c, 12d (making surface 21b a focal point), and to be able to focus the light on a point opposite to the back surface 21a (making that opposite point a focal point). In this case, the required range of motion of the actuator 70 is as follows: Figure 14The “ACT movable range” is shown. 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 take into account the difference in refractive index and make the movable range of the actuator 70 in air approximately 100 μm + 100 μm = 200 μm.

[0047] Camera control via drive unit and actuator The following is for reference Figures 15-18 This indicates that the drive unit 7 (refer to) has passed. Figure 1 The camera control is performed by the camera unit 4 of the actuator 70 and the control unit 8 (see reference 70). In the laser processing apparatus 1, the camera control is performed by the camera unit 4 of the control unit 8 (see reference 70). Figure 1 The control unit 7 and actuator 70 simultaneously move the focusing position of the imaging unit 4 and capture images of the interior of the wafer 20 of the imaging unit 4. In this imaging control, the drive unit 7 performs approximate focusing position alignment related to imaging, and the actuator 70 performs detailed focusing position alignment related to imaging. The drive 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 a structure that moves the objective lens 43 mounted in the imaging unit 4 in the Z direction.

[0048] Figure 15 This is a diagram illustrating the general movement of the focusing position via the drive unit 7 and the actuator 70. The control unit 8 performs a first control on the drive unit 7 in a manner that moves the camera unit 4 to a position where the back surface 21a becomes the focusing position (see reference). Figure 15 (a) and, after the first control, to move the objective lens 43 to a position in which at least a portion of the region between the surface 21b and the back surface 21a, i.e., the first region 28, becomes a focusing position, the actuator 70 is controlled in such a manner as to move the objective lens 43 to a position in which at least a portion of the region between the surface 21b and the back surface 21a becomes a focusing position. Figure 15 (b) and control the actuator 70 in a manner that moves the objective lens 43 to a position such that at least a portion of the region 29, which is the opposite side of the surface 21b to the back surface 21a, becomes a focusing position (see (b)). Figure 15 (c)). Alternatively, the back surface 21a becoming a focusing position may also include the area near the back surface 21a (e.g., a region within ±10 μm from the back surface 21a) becoming a 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, such as Figure 15 As shown in (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 aligned with 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 at 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 aligned with the back surface 21a when the actuator 70 is fixed at the center can be said to be a state in which the area capable of imaging is maximized by the action of the actuator 70.

[0051] In the second control, such as Figure 15 As shown in (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. Then, as... Figure 15 As shown in (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 region 29. The control unit 8 can move the objective lens 43 via the actuator 70 either by sequentially focusing the entire area of ​​the first region 28 and the entire area of ​​the second region 29 in the Z direction, or by sequentially focusing only a portion of the first region 28 and a portion of the second region 29. Furthermore, the control unit 8 can also move the objective lens 43 via the actuator 70 by first focusing the second region 29 and then focusing the first region 28. By implementing this second control, imaging of the interior of the wafer 20 in the first region 28 and the second region 29 is performed.

[0052] Figure 16 This diagram illustrates the detailed movement of the focusing position via the drive unit 7 and actuator 70. (See diagram for details.) Figure 16As shown in (a), if 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 after 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 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, based on the light detection result performed by the light detection unit 44 in this state. Figure 16 (b)). The area near the back side 21a here may also be the area encompassing the entire range of the focusing position that can be deviated from the back side 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. Imaging near the back surface 21a is performed by continuously changing the focusing position in the Z direction in this way. The control unit 8 may also detect the device pattern on the back surface 21a based on the signal from the light detection unit 44 as an imaging result, and determine the detailed position of the back surface 21a based on the device 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 appropriately located.

[0054] The control unit 8 performs a fourth control, namely, in the second control, it controls the actuator 70 (see reference) in such a way that the objective lens 43 is moved from the aforementioned reference position to a position in which at least a portion of the first region 28 becomes a focusing position. Figure 16 (d) and control the actuator 70 in such a manner as 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 reference). 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 Figure 16 In the manner shown, the objective lens 43 is moved to a reference position that serves as the starting position for imaging by the first and third controls, and then the imaging process of imaging the interior of the wafer 20 is performed by the fourth control to extract information about the modified region 12 (e.g., detection of the leading edge position of the crack 14).

[0056] Figure 17 This is a flowchart illustrating an example of an observation method implemented in laser processing apparatus 1. Hereinafter, refer to... Figure 17 and Figure 16 This is an example illustrating the observation method.

[0057] like Figure 17 As shown, 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, through control unit 8, such as Figure 16 As shown in (a), the drive unit 7 is controlled in such a way that the camera unit 4 is moved to a position that makes the back surface 21a a focus position (step S2: first process).

[0059] Next, the actuator 70 is controlled by the control unit 8 to move the position of the objective lens 43 in the Z direction while the area near the back surface 21a is in a focusing position, and the detailed position of the back surface 21a is specified based on the detection result of the light detection unit 44 in this state, such as... Figure 16 As shown in (b), the actuator 70 is controlled to move the objective lens 43 to a position that makes the specific position of the back surface 21a the focusing position, i.e., the reference position. That is, the focusing position is corrected based on the detection result (step S3: second process).

[0060] Next, through control unit 8, such as Figure 16 As shown in (c), the actuator 70 is controlled to move the objective lens 43 to a position that makes the second region 29, which is the observation side on the back side, a focusing position. (Step S4: Second process) Then, via the control unit 8, as shown... Figure 16 As shown in (d), the actuator 70 is controlled in such a way that the objective lens 43 is moved to a position that makes the first region 28, which is the observation side of the surface, a focusing position. (Step S5: Second step) The above is an example of an observation method.

[0061] Furthermore, the observation method for implementing the laser processing apparatus 1 is not limited to Figure 16 and Figure 17 As shown in the diagram. Figure 18This is a diagram illustrating in detail other examples of focusing position movement via drive unit 7 and actuator 70. Figure 18 In the manner shown, with Figure 16 The first control described above is implemented in the same manner as shown (refer to...). Figure 18 (a) and the third control described above is implemented in the second control following the first control (refer to) Figure 18 (b)). That is, Figure 18 The control shown in (a) corresponds to Figure 16 The control shown in (a), in addition, Figure 18 The control shown in (b) corresponds to Figure 16 The control shown in (b). Here, in Figure 16 In the method shown, the third control for determining the reference position (refer to...) Figure 16 In (b)), although an image is obtained near the back surface 21a, this image is only used to determine the reference position and is not used as information related to the derivation of information concerning the modified region 12 of wafer 20. Regarding this point, in Figure 18 In the manner shown, the third control (refer to) Figure 18 The imaging results obtained in (b) near the back surface 21a are used not only as information related to the derivation of the reference position, but also as information related to the derivation of information related to the modified region 12 of the wafer 20. In this way, by effectively using the imaging results of the third control, it is possible to avoid performing repeated imaging processing on the same area, and imaging can be performed more efficiently.

[0062] Now, in the third control (reference) used to determine the reference position Figure 18 In (b)), region A1 near the back side 21a is obtained (refer to...). Figure 18 The imaging result of (c)). 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 the area other than the aforementioned area A1 becomes the focusing position, in a manner that makes the area within the first region 28 or the second region 29, and the detailed position of the specific back surface 21a in the third control, become the focusing position. Figure 18 In the example shown, the un-photographed area of ​​the second region 29 is designated as an area where photography is not required. In this case, the control unit 8 controls the drive unit 7 in a manner that moves the entire imaging unit 4 to a position where region A2, which is the un-photographed area of ​​the first region 28, becomes a focusing position (pushing it upwards). More specifically, the control unit 8, taking into account the movable range of the actuator 70, controls the drive unit 7 in a manner that moves the entire imaging unit 4 to a position where region A2 becomes a focusing position through a 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 in which region A2, which is included in the un-imaged area, becomes 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 only a part of the region A2 becomes a sequential focusing position.

[0064] Thus, in Figure 18 In the illustrated manner, the imaging results obtained in the third control are used not only as information related to the derivation of the reference position but also as information related to the derivation of information related to the modified region 12 of the wafer 20. The fifth and sixth controls are implemented only for areas where imaging results cannot be obtained in the third control, thereby enabling efficient imaging. Furthermore, for example, if the desired imaging area is not entirely within the movable range of the actuator 70, the entire desired imaging area can be imaged by sequentially expanding the imaging area through the implementation of the fifth and sixth controls (multiple times as needed).

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

[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, wherein a modified region 12 is formed inside by irradiating the wafer 21b with laser light. It is characterized by comprising: an imaging 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 the wafer 20 at a focusing position; and a light detection unit 44 that detects light propagating in the wafer 20; a drive unit 7 that supports the imaging unit 4 and moves the imaging unit 4 in the Z direction, which is the vertical direction; and an objective lens 43 that is provided with the objective lens 43 to move the objective lens 43 in the vertical direction. An actuator 70 that moves in the Z direction; and a control unit 8 that 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, the drive unit 7, which 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, the actuator 70, which 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 such that both the first region 28 and the second region 29 become focusing positions, it is possible to simultaneously and appropriately perform 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, etc., through back surface 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 has 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 simultaneously providing the drive unit 7 and the actuator 70, for example, approximate alignment can be performed by the drive unit 7 and detailed alignment by the actuator 70, etc. Compared to the case where the entire Z-direction movement 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 driving unit 7 and the imaging unit 4 are controlled to make the back surface 21a, which serves as the boundary between 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 between the first region 28 and the second region 29), the high-speed movement of the objective lens 43, which makes the first region 28 and the second region 29 focus positions, can be appropriately implemented to the maximum extent within the movable range of the actuator 70. 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 high-speed movement of the objective lens 43, which sets the first region 28 and the second region 29 to a focusing position, within the movable range of the actuator 70.

[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 becomes 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 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, if the actual thickness of the wafer 20 differs from the intended thickness, the focusing position is expected 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 described above, 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 range of motion 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-imaged 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, imaging near the back surface 21a can be performed during the determination of the specific detailed position of the back surface 21a. Therefore, in this observation device 1, the drive unit 7 (fifth control) is controlled to move the imaging unit 4 to a position where the un-imaged area not captured in the third control becomes a focusing position, and the actuator 70 (sixth control) is controlled to move the objective lens 43 to a new reference position after the fifth control, and to move the objective lens 43 to a position where the un-imaged area becomes a focusing position. With this structure, because control is performed to make the area not captured 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 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.

[0071] The observation method of this embodiment is a method for observing a wafer 20 having a surface 21b and a back surface 21a, wherein a modified region 12 is formed internally by irradiating a laser from the surface 21b side. The method 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, i.e., a second region 29, which is the opposite side of the surface 21b to the back surface 21a, i.e., a second region 29, becoming 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 may also include a pre-processing step prior to the first step, in which the actuator 70 is fixed at the center of its movable range in the Z direction. With this structure, high-speed movement of the objective lens 43, which positions the first region 28 and the second region 29 as focusing points, can be appropriately implemented to the maximum extent possible within the movable range of the actuator 70.

Claims

1. An observation device, characterized in that: It is an observation device for observing wafers having a first surface and a second surface, and having modified regions formed inside by irradiating a laser from the first surface side. have: The camera unit includes a light source that outputs transmissive light to the wafer, a focusing lens that focuses the light output from the light source onto the wafer at a focusing position, and a light detection unit that detects the light propagating in the wafer. A drive unit that supports the camera unit and moves the camera unit in the Z direction, which is the vertical direction; An actuator, disposed on the condenser lens, moves the condenser lens in the Z direction; and Control Department The control unit is configured to perform control in the following manner: The first control controls the drive unit in such a way that the camera unit is moved to a position where the second surface becomes the focusing position; as well as The second control, following the first control, controls the actuator in such a way that the condenser lens is moved to a position such that at least a portion of the region between the second surface and the first surface, i.e., the first region, becomes the focusing position, and controls the actuator in such a way that the condenser lens is moved to a position such that at least a portion of the region opposite to the second surface and the first surface, i.e., the second region, becomes the focusing position.

2. The observation device as described in claim 1, characterized in that: Before the first control, the control unit also performs: pre-control, which controls the actuator in such a way that the actuator is fixed at the center position of the actuator's movable range in the Z direction.

3. The observation device as described in claim 1 or 2, characterized in that: The control unit is configured in the second control to perform the following control: The third control controls the actuator by moving the position of the condensing lens in the Z direction when the region near the second surface becomes the focusing position. Based on the light detection result of the light detection unit in this state, the detailed position of the second surface is determined, and the actuator is controlled by moving the condensing lens to a position, i.e., a reference position, whereby the determined detailed position of the second surface becomes the focusing position. as well as The fourth control controls the actuator in a manner that moves the condenser lens from the reference position to a position in which at least a portion of the first region becomes the condenser position, and controls the actuator in a manner that moves the condenser lens from the reference position to a position in which at least a portion of the second region becomes the condenser position.

4. The observation device as described in claim 1 or 2, characterized in that: The control unit is in the second control. It is structured in the following manner: The third control involves moving the position of the condensing lens in the Z direction when the region near the second surface becomes the focusing position. Based on the light detection result of the light detection unit in this state, the detailed position of the second surface is determined, and the actuator is controlled to move the condensing lens to a reference position where the determined detailed position of the second surface becomes the focusing position. It is also constituted by implementing the following control methods: The fifth control moves the driving unit to a position in which at least a portion of the unphotographed area becomes the focusing position, the unphotographed area being a region within the first region or the second region, and not being a region that was not considered as the focusing position when the detailed position of the second surface was determined in the third control; as well as The sixth control moves the actuator by using the position of the condenser lens of the camera unit after the fifth control as the new reference position, and moves the condenser lens to a position that makes the area contained in the un-photographed area the condenser position.

5. An observation method, characterized in that: It 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 a laser from the first surface side. include: In the first step, a drive unit that moves the camera unit in the Z direction (vertical direction) moves the camera unit to a position where the second surface becomes a focusing position; and In the second step, by using an actuator that moves the focusing lens contained in the camera unit in the Z direction, the focusing lens is moved 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 the focusing position, and the focusing lens is moved to a position where at least a portion of the region opposite to the second surface and the first surface, i.e., the second region, becomes the focusing position.

6. The observation method as described in claim 5, characterized in that: It also includes a pre-process, prior to the first process, controlling the actuator in such a way that the actuator is fixed at the center of the actuator's movable range in the Z direction.

Images