Processing apparatus

Abstract

To provide a processing apparatus capable of accurately processing a wafer.SOLUTION: A processing apparatus comprises: a processing laser radiation device which radiates a processing laser beam while moving in a direction of travel along a plurality of dicing streets extending in at least one direction of a wafer; a coaxial height detection section which has the same optical axis as the processing laser beam, irradiates a surface of the wafer with a detection laser beam and detects a height position of the surface of the wafer based on reflection light of the detection laser beam; a front height detection section which is positioned on the front side relative to the processing laser radiation device; and a rear height detection section which is positioned on a rear side, which is a reverse side of the front side, relative to the processing laser radiation device. The front height detection section and the rear height detection section are movable in a parallel direction of the plurality of dicing streets and detect height positions of the dicing streets.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a processing device. [Background technology]

[0002] Conventionally, to separate wafers with semiconductor devices or electronic components formed on their surfaces into individual chips, a dicing machine is used, which cuts the wafer by creating grinding grooves in the wafer using a thin grinding wheel about 30 μm thick containing fine diamond abrasive grains.

[0003] In this processing device, the dicing blade is rotated at a high speed of, for example, 30,000 to 60,000 rpm to grind the wafer, and the wafer is completely cut (full cut) or incompletely cut (half cut or semi-full cut).

[0004] In recent years, instead of cutting using a conventional dicing blade, a processing device has been proposed in which a laser beam is focused on the interior of a wafer, forming a modified region inside the wafer and dividing the wafer into individual chips (see, for example, Patent Document 1). In this technology, the modified region formed inside the wafer is formed at a certain depth from the surface of the wafer, so it is necessary to use an autofocus mechanism to detect the height position of the wafer surface (position in the thickness direction) and control the position of the focal point of the laser beam with high precision.

[0005] In the technology disclosed in Patent Document 1, in order to form a uniformly modified region (degraded layer) at a predetermined depth inside the wafer, a detection laser light (laser light for autofocus (AF)) is irradiated onto the surface of the wafer, the height position of the wafer surface is detected based on the reflected light, and processing is performed while always maintaining a constant processing position. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-139726 Summary of the Invention [Problem to be solved by the invention]

[0007] When the AF laser beam is passed along the same optical axis as the processing laser beam, the wafer surface height position can be detected at approximately the same time as the wafer processing timing, allowing accurate processing at the designated processing point. However, if the processing speed is increased or if there is a large fluctuation in the height position of the wafer surface and the AF laser beam's tracking performance with respect to the wafer surface is insufficient, a delay occurs in the response of the detector that detects the AF laser beam to the fluctuation, and there is a risk that the accurate height position of the wafer surface cannot be detected.

[0008] Here, if a detector such as a displacement sensor is placed ahead in the processing direction, the height position of the wafer surface can be detected before the wafer is processed. Therefore, by detecting the unevenness of the wafer surface in advance and using the detection result to detect the height position using the AF laser light, the response delay of the detector that detects the AF laser light can be reduced. However, in this case, the height position of the wafer surface is not detected at the timing of wafer processing, so if the state of the wafer changes between the advance detection of the wafer surface and the timing of wafer processing, it is difficult to process the wafer in response to the change.

[0009] The present invention has been made in view of the above circumstances, and has as its object to provide a processing apparatus capable of accurately processing wafers. [Means for solving the problem]

[0010] <1> A processing apparatus according to one embodiment of the present invention includes a processing laser irradiation device that irradiates a processing laser beam while moving in a traveling direction along a plurality of dicing streets extending in at least one direction of a wafer, a coaxial height detection unit that has the same optical axis as the processing laser beam, irradiates a surface of the wafer with a detection laser beam, and detects a height position of the surface of the wafer based on reflected light of the detection laser beam, a front height detection unit located in front of the processing laser irradiation device, and a rear height detection unit located in the rear of the processing laser irradiation device on the opposite side from the front, wherein the front height detection unit is movable in a parallel direction of the plurality of dicing streets and detects a height position of the dicing street before processing by the processing laser irradiation device, and the rear height detection unit is movable in a parallel direction of the plurality of dicing streets and detects a height position of the dicing street after processing by the processing laser irradiation device. <2> the above <1> The processing apparatus described in the item (1) may correct the height position of the wafer surface by using the height information acquired by the front height detection unit. <3> the above <1> or <2> The processing apparatus described in may determine a surface condition of the dicing street after processing based on height information acquired by the front height detection unit and height information acquired by the rear height detection unit. <4> the above <1> ~ <3> The processing apparatus described in any one of the items 1 to 4 may detect an abnormality in the surface state of the wafer. [Effects of the Invention]

[0011] According to the processing apparatus of the present invention, it is possible to process wafers accurately. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic configuration diagram of a processing device according to an embodiment of the present invention. [Figure 2] FIG. 2 is a schematic configuration diagram of a processing device according to the embodiment. [Figure 3]FIG. 1 is a perspective view of a wafer for explaining dicing streets on the wafer and the processing direction. [Figure 4] FIG. 2 is a functional block diagram of a control unit. [Figure 5] 10 is a graph showing the output characteristics of an AF signal. [Figure 6] 10 is a schematic diagram showing how a front height detection unit detects an abnormality. FIG. [Figure 7] 10 is a schematic diagram showing an example of the positional relationship between a coaxial AF device, a front height detection unit, and a rear height detection unit when viewed from the positive direction of the Z axis relative to the wafer. FIG. [Figure 8] FIG. 10 is a schematic diagram showing an example of the positional relationship between a coaxial AF device, a front height detection unit, and a rear height detection unit when viewed from a direction perpendicular to the extension direction of a dicing street on the wafer surface. [Figure 9] 10 is a schematic diagram showing an example of the positional relationship between a coaxial AF device, a front height detection unit, and a rear height detection unit when viewed from the extending direction of a dicing street. FIG. [Figure 10] 3 is a schematic diagram showing an example of the positional relationship between a coaxial AF device, a front height detection unit, and a rear height detection unit. FIG. [Figure 11] FIG. 1 is a schematic diagram showing an example of height position detection of a wafer surface using a coaxial AF device. [Figure 12] FIG. 4 is a sequence diagram showing the flow of operations of the processing device. [Figure 13] 10 is a schematic diagram showing a planned processing point and a processing point for explaining the flow of operation of the processing device. FIG. [Figure 14] 10 is a diagram showing an example of a result of detecting the height position of a wafer by the coaxial AF device in this embodiment. [Figure 15] 10 is an example of the detection result of the height position of a wafer using a conventional coaxial AF device. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, a processing device according to an embodiment of the present invention will be described with reference to the drawings. In the X, Y, and Z directions shown in each drawing, the + direction is the positive direction, and the - direction is the negative direction.

[0014] 1 is a schematic diagram of a processing apparatus according to an embodiment of the present invention. As shown in FIG. 1, the processing apparatus 1 includes a stage 2, a processing laser irradiation device 3, a coaxial height detection unit 4, a front height detection unit 5, a rear height detection unit 6, and a control unit 7.

[0015] The stage 2 is movable in the X and Y directions and holds by suction the wafer W. When the wafer W is processed, the stage 2 moves in the X and Y directions with the wafer W placed thereon.

[0016] The processing laser irradiation device 3 irradiates the wafer W with processing laser light while moving in the traveling direction along a plurality of dicing streets extending in at least one direction on the wafer W. As shown in Fig. 2, the processing laser irradiation device 3 includes a processing laser light source 31, a dichroic mirror 32, a condenser lens 33, and a condenser lens driving means 34. The processing laser light source 31, the dichroic mirror 32, and the condenser lens 33 are arranged in this order on a first optical path OP1, which is the optical path of the processing laser light L1, and the condenser lens 33 is arranged at a position closest to the wafer W.

[0017] The processing laser light source 31 emits processing laser light L1 for forming a modified region inside the wafer W. For example, the processing laser light source 31 has a pulse width of 1 μs or less and a peak power density of 1×10 at the focal point. 8 (W / cm 2) or more. The pulse width and peak power density of the laser light described above are merely examples, and are not particularly limited as long as the desired modified region can be formed. The processing laser light L1 emitted from the processing laser light source 31 passes through a dichroic mirror 32 and is then focused inside the wafer W by a condenser lens 33. The Z-direction position of the focusing point of the processing laser light L1 (position in the thickness direction of the wafer W) is adjusted by slightly moving the condenser lens 33 in the Z direction (the optical axis direction of the processing laser light L1) using a condenser lens driving means 34. In addition, the dichroic mirror 32 reflects the AF detection light L2 emitted from the coaxial AF device 4 described later.

[0018] The condenser lens driving means 34 drives the condenser lens 33 so that the distance between the condenser lens 33 and the surface of the wafer W is constant, based on the processing conditions set by the control unit 7. As a result, the condenser lens 33 moves slightly in the Z direction (thickness direction of the wafer) to follow the displacement of the surface of the wafer W, and the focal point of the processing laser light L1 is positioned at a constant distance (depth) from the surface of the wafer W. As a result, a modified region R can be formed at a desired position inside the wafer W. The condenser lens driving means 34 is, for example, an actuator.

[0019] In this embodiment, processing refers to forming a modified region R. A modified region R is formed at a position on the dicing street irradiated with the processing laser light L1.

[0020] The coaxial AF device (coaxial height detection unit) 4 has the same optical axis as the processing laser light, irradiates the surface of the wafer W with a detection laser light, and detects the height position of the wafer surface based on the reflected light of the detection laser light. As shown in FIG. 3, the coaxial AF device 4 irradiates the surface of the wafer W with a detection light (AF detection light) L2, and detects the height position of the surface of the wafer W based on the reflected light. A second optical path OP2, which is the optical path of the AF detection light L2, is bent by a dichroic mirror 32 so as to share a portion of the optical path with the first optical path OP1 of the processing laser light L1. A condenser lens 33 is disposed on this shared optical path. Therefore, the optical axis of the AF detection light L2 is the same as the optical axis of the processing laser light L1 just before the detection light L2 reaches the wafer W. The coaxial AF device 4 moves in the processing progress direction together with the processing laser irradiation device 3, and detects the height position of the surface of the wafer W.

[0021] Here, the "processing direction" refers to, for a single dicing street, the direction in which the processing device 1 advances toward an unprocessed region (the direction toward the planned processing point P') from a processing point P, which has already formed a modified region R on the wafer W, as indicated by the arrow Dx in FIG. 3 . The processing direction for a single dicing street is referred to as the X-direction. When processing multiple dicing streets arranged in parallel on the surface of the wafer W and processing the wafer W across the multiple dicing streets, the direction in which the processing device 1 advances from a dicing street where a processing point P has already been formed toward another dicing street where a modified region R has not yet been formed, as indicated by the arrow Dy in FIG. 3 , is also referred to as the "processing direction." In this case, the direction of advance between adjacent dicing streets is referred to as the Y-direction. That is, the direction of the arrow Dx in FIG. 3 is the X-direction, and the direction of the arrow Dy is the Y-direction.

[0022] 2, the coaxial AF device 4 includes an AF light source 41, a collimator lens 42, a knife edge 43, a focus optical system 44, a movable lens driving means 45, a half mirror 46, an imaging lens 47, and a detector 48. The coaxial AF device 4 detects the height position of the surface of the wafer W using the so-called knife edge method.

[0023] The AF light source 41 is a light source that emits the AF detection light L2, and is composed of a laser light source such as an LD (Laser Diode) light source or an SLD (Super Luminescent Diode) light source. The AF detection light L2 has a wavelength that is different from that of the processing laser light L1 and that can be reflected by the surface of the wafer W.

[0024] 2, the AF detection light L2 emitted from the AF light source 41 is collimated by the collimating lens 42, and a portion of the light is blocked by the knife edge 43. The light that travels without being blocked by the knife edge 43 is reflected by the half mirror 46, further reflected by the dichroic mirror 32, and collected by the collecting lens 33 to be irradiated onto the wafer W.

[0025] The focusing optical system 44 is disposed on the second optical path OP2 of the AF detection light L2, at a position independent of the optical path shared with the first optical path OP1 of the processing laser light L1. Specifically, the focusing optical system 44 is disposed between the dichroic mirror 32 and the half mirror 46 on the AF light reflection path 244. The AF light reflection path 244 is a path for guiding the reflected light of the AF detection light L2 reflected by the surface of the wafer W to the detector 48.

[0026] The focus optical system 44 is composed of multiple lenses including a movable lens 442 configured to be movable at least along the second optical path OP2, and adjusts the focal point of the AF detection light L2 in the Z direction independently of the focal point of the processing laser light L1. The focus optical system 44 includes, in order from the wafer W side, a fixed lens 441 provided immovably along the second optical path OP2, and a movable lens 442 provided movably along the second optical path. In this embodiment, the fixed lens 441 is a positive lens, and the movable lens 442 is a negative lens.

[0027] The movable lens driving means 45 moves the movable lens 442 along the second optical path OP2. When the movable lens 442 moves along the second optical path OP2, the Z-direction position of the focal point of the AF detection light L2 changes in accordance with the direction and amount of movement of the movable lens 442, while the Z-direction position of the focal point of the processing laser light L1 remains fixed. In other words, the relative distance between the focal point of the processing laser light L1 and the focal point of the AF detection light L2 changes.

[0028] The AF detection light L2 reflected by the surface of the wafer W is refracted by the condenser lens 33, reflected by the dichroic mirror 32, passes through the focus optical system 44, and passes through the half mirror 46. Furthermore, this reflected light is condensed by the imaging lens 47, and the reflected light is irradiated onto the detector 48, forming a condensed image on the light-receiving surface of the detector 48.

[0029] The detector 48 is made of a two-part photodiode having two split light receiving elements (photoelectric conversion elements). In detail, the detector 48 splits and receives the collected image of the reflected light of the AF detection light L2, and outputs output signals (electrical signals) according to the respective light intensities to the AF signal processing unit 74, which will be described later.

[0030] The displacement of the surface of the wafer W can be detected by a known method using a two-part photodiode.

[0031] As described above, the coaxial AF device 4 is configured such that the condenser lens 33 is disposed on a shared optical path between the first optical path OP1 of the processing laser light L1 and the second optical path OP2 of the AF detection light L2. In this configuration, when the relative distance between the condenser lens 33 and the wafer W is changed to change the processing depth of the modified region, not only does the position of the focal point of the processing laser light L1 relative to the wafer W change in the Z direction, but also the position of the focal point of the AF detection light L2 changes in the Z direction relative to the wafer W.

[0032] In this way, even if the relative distance between the focusing lens 33 and the wafer W changes, by moving the movable lens 442, the focusing point of the AF detection light L2 can be aligned with the top surface Wb of the wafer W while keeping the Z-direction position of the focusing point of the processing laser light L1 fixed.

[0033] The front height detection unit 5 is a displacement sensor that detects the height position of the surface of the wafer W, and detects the height position of the surface of the region of the wafer W that is scheduled to be processed. The front height detection unit 5 is located ahead of the processing direction (the X-direction and / or Y-direction). The front height detection unit 5 detects the height position of the surface of the wafer W at a timing prior to processing of the wafer W. In particular, when the front height detection unit 5 is located away from the coaxial AF device 4 in the Y-direction, it is possible to detect in advance the surface height position of the dicing street that is scheduled to be processed, i.e., the surface shape of the dicing street.

[0034] Furthermore, the front height detection unit 5 is located in front of the coaxial height detection unit 4 and is movable in at least one of the X direction and the Y direction relative to the coaxial AF device 4. As will be described in detail later, since the front height detection unit 5 is movable in at least one of the X direction and the Y direction relative to the coaxial AF device 4, it is possible to detect the height position of the surface of the unprocessed wafer W at a position according to the user's request.

[0035] The specific configuration of the front height detection unit 5 is not particularly limited. For example, the front height detection unit 5 may be a triangulation displacement sensor or a white light confocal sensor. In particular, when the front height detection unit 5 is a white light confocal sensor, the front height detection unit 5 is less susceptible to the influence of a film or the like formed on the surface of the wafer W, and can stably detect the height position of the surface of the wafer W. Furthermore, the front height detection unit 5 may be, for example, a displacement detection device using an AF mechanism similar to the coaxial AF device 4. In this case, the front height detection unit 5 has an optical axis different from that of the processing laser light L1 and is located forward in the processing direction of the wafer W. Furthermore, the AF detection light provided by the front height detection unit 5 may be subjected to averaging processing or the like, and may have a wider focused spot diameter than the AF light source of the coaxial AF device 4.

[0036] The rear height detection unit 6 is a displacement sensor that detects the height position of the surface of the wafer W, and detects the height position of the surface of an area that has already been processed of the wafer W. The rear height detection unit 6 differs from the front height detection unit 5 in that it is located rearward in the processing progress direction, on the opposite side from the front.

[0037] Furthermore, the rear height detection unit 6 is located behind the coaxial height detection unit 4 and is movable in at least one of the X direction and the Y direction relative to the coaxial AF device 4. As will be described in detail later, because the rear height detection unit 6 is movable in at least one of the X direction and the Y direction relative to the coaxial AF device 4, it is possible to detect the height position of the surface of the processed wafer W at a position according to the user's request.

[0038] The specific configuration of the rear height detection unit 6 is not particularly limited. For example, the rear height detection unit 6 may be a triangulation displacement sensor or a white light confocal sensor. Alternatively, the rear height detection unit 6 may be a displacement detection device using an AF mechanism similar to the coaxial AF device 4. In this case, the rear height detection unit 6 has an optical axis different from that of the processing laser light L1 and is located behind the wafer W in the processing direction. The AF detection light provided by the rear height detection unit 6 may be subjected to averaging processing or may have a wider focused spot diameter than the AF light source of the coaxial AF device 4. Because the measurement method and state can be individually changed, a measurement method or state different from that of the front height detection unit 5 can be used. For example, the rear height detection unit 6 can determine whether a half-cut crack has occurred after processing by reducing the beam spot to measure a narrow area and becoming sensitive to small changes.

[0039] The control unit 7 is composed of a CPU, memory, input / output circuits, etc., and controls various operations of each unit of the processing device 1. The control unit 7 controls, for example, the operations of the stage 2, the processing laser irradiation device 3, the coaxial height detection unit 4, the front height detection unit 5, and the rear height detection unit 6. The control unit 7 includes a stage control unit 71, a processing condition setting unit 72, a coaxial AF setting unit 73, an AF signal processing unit 74, a detection condition setting unit 75, a state determination unit 76, and an abnormality detection unit 77.

[0040] The stage control unit 71 moves the stage 2 in the X and Y directions with the wafer W placed thereon. The stage 2 moves in conjunction with the operations of the processing laser irradiation device 3, the coaxial height detection unit 4, the front height detection unit 5, and the rear height detection unit 6.

[0041] The processing condition setting unit 72 sets processing conditions when the processing laser irradiation device 3 processes the wafer W. The processing conditions are conditions set for the processing device 1 to process the wafer W, and include, for example, the number and position of dicing streets, the formation position (depth) of the modified region, the output intensity and pulse width of the processing laser light source, the stage movement speed, etc.

[0042] The coaxial AF setting unit 73 sets parameters such as the output intensity of the laser emitted from the AF light source 41. The coaxial AF setting unit 73 also sets detection conditions that are set so that the detector 48 detects the AF detection light L2. The detection conditions include at least one of the range on the wafer surface to which AF is applied and an AF gain setting value. The AF gain setting value is an AF gain value that is set for the height position of the surface of the wafer W at each sampling point of the detection light L2 detected by the detector 48. By appropriately setting the AF gain value, the detector 48 can appropriately detect the height position of the surface of the wafer W, even though the wafer W is constantly moving, and delays in the detection can be suppressed. In addition, the coaxial AF setting unit 73 controls the driving of the movable lens driving means 45 so that the focal point of the AF detection light L2 coincides with the upper surface Wb of the wafer W (specifically, so that the output of the AF signal becomes zero), and moves the movable lens 442 of the focus optical system 44 along the second optical path OP2.

[0043] The AF signal processing unit 74 generates an AF signal E, AF data, or AF information as a displacement signal (detection signal) indicating a displacement (defocus distance) in the Z direction from a reference position on the surface of the wafer W, based on the output signals output from each light-receiving element of the detector 48. For example, the AF signal corresponds to the height position of the upper surface Wb of the wafer W at a predetermined position on the wafer W. In other words, the AF signal processing unit 74 detects the height position of the upper surface Wb of the wafer W based on the output signals output from each light-receiving element of the detector 48. The AF signal E is sent to the processing condition setting unit 72, and some of the processing conditions are output to the condenser lens driving means 34.

[0044] Fig. 5 is a graph showing the output characteristics of the AF signal E. In Fig. 5, the horizontal axis represents the displacement (defocus distance) in the Z direction (thickness direction of the wafer) from the reference position on the top surface Wb of the wafer W, and the vertical axis represents the output value of the AF signal E. It is assumed that the focus point of the AF detection light L2 is adjusted in advance to coincide with the reference position (origin) on the top surface Wb of the wafer W.

[0045] As shown in FIG. 5, the output characteristic of the AF signal E is an S-shaped curve with the reference position (origin) of the top surface Wb of the wafer W as the zero-cross point. Furthermore, when the position of the top surface Wb of the wafer W is within the range indicated by the arrow in FIG. 5, i.e., within the measurement range (pull-in range) in which the displacement of the top surface Wb of the wafer W can be detected, the relationship between the displacement of the top surface Wb of the wafer W and the output of the AF signal E is a monotonically increasing (or monotonically decreasing) curve passing through the origin, and shows an approximately linear change over most of the curve. In other words, if the output of the AF signal E is zero, it can be determined that the top surface Wb of the wafer W is at a focal position that coincides with the focal point of the AF detection light L2. On the other hand, if the output of the AF signal E is not zero, the direction and amount of displacement of the top surface Wb of the wafer W can be determined.

[0046] The AF signal processing unit 74 determines whether the AF signal E (height position of the upper surface Wb of the wafer W) is located within a predetermined range. Note that the AF signal processing unit 74 does not have to determine whether the height position of the upper surface Wb of the wafer W is located within a predetermined range. For example, the AF signal processing unit 74 determines whether the position (hereinafter sometimes referred to as the actuator height position) obtained by converting the height position of the upper surface Wb of the wafer W acquired based on the AF signal E into the position of the condenser lens driving means 34, that is, the position (actuator height position) of the condenser lens driving means 34 corresponding to the position of the condenser lens 33 arranged so that the focal point of the AF detection light L2 is located on the upper surface Wb of the wafer W, is located within the predetermined range.

[0047] Here, the predetermined range is, for example, the distance or range (full stroke) over which the condenser lens driving means 34 can move minus the distance or range over which the condenser lens driving means 34 moves necessary to measure the entire thickness of the wafer W. For example, if the thickness of the wafer W is 400 μm, the effective refractive index is 4, and the full stroke of the thickness detectable range is 120 μm (and the downward or upward direction in the Z direction is positive), the condenser lens driving means 34 needs to move 100 μm in the Z direction (=wafer thickness / effective refractive index=400 μm / 4) to measure the entire thickness of the wafer W. Therefore, if the height position of the condenser lens driving means 34 is located within a range of 20 μm from 0 μm (e.g., the initial position or reference position of the condenser lens driving means 34 in the Z direction), the thickness of the wafer W can be measured over the entire length by controlling the condenser lens driving means 34 to move the condenser lens 33. This determination makes it possible to improve the accuracy of detecting the height position of the upper surface Wb.

[0048] The height position of the surface of the wafer W detected by the front height detection unit 5 is transmitted to the coaxial AF setting unit 73. Therefore, the coaxial AF device 4 can detect the height position of the wafer W based on the height position of the surface of the wafer W detected by the front height detection unit 5. For example, the coaxial AF device 4 can correct errors from the surface shape traced during processing by detecting the height position of the wafer W based on the height position of the surface of the wafer W detected by the front height detection unit 5. Furthermore, the coaxial AF device 4 can correct vibrations of the laser head and the like that may occur during processing based on the height position of the surface of the wafer W detected by the front height detection unit 5. Therefore, the coaxial AF device 4 can accurately detect the height position of the wafer W, thereby improving the height position detection sensitivity.

[0049] The detection condition setting unit 75 sets the distances in the X and Y directions between the front height detection unit 5 and the coaxial AF device 4, and the distances in the X and Y directions between the rear height detection unit 6 and the coaxial AF device 4. In other words, the detection condition setting unit 75 allows the front height detection unit 5 to be moved to any position in the X and Y directions in front of the coaxial height detection unit 4. The detection condition setting unit 75 also allows the rear height detection unit 6 to be moved to any position in the X and Y directions behind the coaxial height detection unit 4. The spacing between the dicing streets (INDEX distance I (see, for example, FIG. 7)) varies depending on the type of wafer W. By setting the INDEX distance I by the detection condition setting unit 75, the height position of the dicing street at an appropriate position in the Y direction can be detected.

[0050] The control unit 7 may include a condition determination unit 76 that determines the surface condition of the wafer W after processing. The condition determination unit 76 can determine the surface condition of the wafer W after processing based on the height information from the front height detection unit 5 and the height information from the rear height detection unit 6. For example, if there is a large difference between the length measurement data from the rear height detection unit 6 and the length measurement data from the coaxial AF device 4 or the front height detection unit 5, there is a possibility that surface damage due to processing has occurred. Therefore, a threshold may be set for the difference between the value of the length measurement data from the rear height detection unit 6 and the length measurement data from the coaxial AF device 4 or the front height detection unit 5, and if the difference is equal to or greater than the threshold, it may be determined that the surface condition is poor.

[0051] Furthermore, the presence or absence of a half-cut can be determined by using a high-resolution sensor or the like in the rear height detection unit 6. For example, the presence or absence of a half-cut can be detected by applying a configuration similar to that of the coaxial AF device 4 to the rear height detection unit 6 and setting the laser beam spot diameter to 10 μm or less. Specifically, for example, the height position of the surface of the wafer W without a half-cut is measured in advance using the front height detection unit 5 and the rear height detection unit 6, the difference between these measurements is calculated, and a threshold value is set based on this difference. The presence or absence of a half-cut can be determined by comparing the difference between the height positions measured by the front height detection unit 5 and the rear height detection unit 6, obtained through actual measurement, with the threshold value. When using only a conventional coaxial AF device, if the beam spot diameter is too small, minute stains or changes on the wafer surface will be detected. Therefore, when using only a conventional coaxial AF device, the spot diameter must be set to a certain size, for example, a diameter of several tens of μm to 100 μm. A spot diameter of several tens of μm to 100 μm makes it difficult to detect a half-cut with high accuracy. On the other hand, as described above, by using a sensor with high resolution in the rear height detection unit 6, it is possible to determine whether or not there is a half cut.

[0052] The control unit 7 may also include an anomaly detection unit 77 that detects anomalies on the surface of the wafer W using either the coaxial AF device 4 or the front height detection unit 5. FIG. 6 is a schematic diagram illustrating anomaly detection by the anomaly detection unit 77. In the figure, the upper and lower limits of the set detection threshold are indicated by two dashed lines, and the surface height position of a single dicing street that the front height detection unit 5 has already detected or is expected to detect is indicated by a solid line. As the stage 2 moves in the positive direction of the X axis, the front height detection unit 5 moves relatively in the negative direction of the X axis to detect the surface height position of the wafer W. When the front height detection unit 5 detects a surface height position at each processing point of the wafer W that exceeds the detection threshold, as indicated by the dashed line, the anomaly detection unit 77 detects the surface height position at each processing point of the wafer W that exceeds the detection threshold as an anomaly.

[0053] Next, we will explain the positional relationship between the coaxial AF device 4, the front height detection unit 5, and the rear height detection unit 6. Fig. 7 is a schematic diagram showing an example of the positional relationship between the coaxial AF device 4, the front height detection unit 5, and the rear height detection unit 6 when viewed from the positive direction of the Z axis with respect to the wafer W. Fig. 7 shows a dicing street S where already-machined processing points P are lined up, and a dicing street S' where not-yet-machined planned processing points P' are lined up.

[0054] 7, the front height detection unit 5 is located in the negative X-axis direction and the positive Y-axis direction with respect to the coaxial AF device 4. In other words, the front height detection unit 5 is located in front of the coaxial AF device 4. The front height detection unit 5 detects the height positions of the planned processing points P' aligned along the dicing street S'.

[0055] FIG. 8 is a schematic diagram showing the positional relationship of the coaxial AF device, the front height detection unit, and the rear height detection unit when viewed from a direction (Y direction) perpendicular to the extension direction of the dicing street on the wafer surface. FIG. 9 is a schematic diagram showing the positional relationship of the coaxial AF device, the front height detection unit, and the rear height detection unit when viewed from a direction (X direction) parallel to the dicing street. As shown in FIGS. 8 and 9, the front height detection unit 5 is located forward of the processing laser beam L1 and the AF laser beam L2 in the processing progress direction. When the processing laser beam L1 is irradiated onto the wafer W, a modified layer is formed on the dicing street starting from the processing focal point f of the processing laser beam L1. An upper crack is formed in the modified layer in the positive direction of the Z axis, and a lower crack is formed in the modified layer in the negative direction of the Z axis.

[0056] It is preferable that the distance in the X-axis direction between the front height detection unit 5 and the coaxial AF device 4 be as small as possible. By making the distance in the X-axis direction between the front height detection unit 5 and the coaxial AF device 4 as small as possible, it is possible to reduce the movement distance in the X direction that is not used for processing. In particular, by making the distance in the X-axis direction between the front height detection unit 5 and the coaxial AF device 4 as small as possible, an increase in the processing stroke is suppressed, and the time required for processing can be shortened.

[0057] As described above, the front height detection unit 5 and the rear height detection unit 6 can be moved to any position in the X direction (the extension direction of the dicing streets) and the Y direction (the parallel direction of the dicing streets). After the movement, the front height detection unit 5 and the rear height detection unit 6 function while maintaining the positional relationship between the coaxial AF device 4, the front height detection unit 5, and the rear height detection unit 6.

[0058] 10(a), the front height detection unit 5 is located in the negative X-axis direction and the positive Y-axis direction with respect to the coaxial AF device 4, and the rear height detection unit 6 is located in the positive X-axis direction and the negative Y-axis direction. In other words, the front height detection unit 5 is located forward in the Y-axis direction with respect to the coaxial AF device 4, and the rear height detection unit 6 is located rearward in the Y-axis direction. With this positional relationship, the front height detection unit 5 measures the profile of the entire length of the dicing street before processing, the coaxial AF device 4 detects the height position of the surface of the wafer W while the processing laser irradiation device 3 processes the wafer W, and the rear height detection unit 6 measures the profile after processing to determine the state.

[0059] In FIG. 10(b), the front height detection unit 5 is located in the negative X-axis direction and at the same position (on the same processing line) in the Y-axis direction relative to the coaxial AF device 4, while the rear height detection unit 6 is located in the positive X-axis direction and the negative Y-axis direction. That is, the front height detection unit 5 is located on the same processing line relative to the coaxial AF device 4, while the rear height detection unit 6 is located shifted rearward in the Y-axis direction. This positional relationship shortens the time interval between the profile measurement by the front height detection unit 5 and the detection of the height position of the surface of the wafer W by the coaxial AF device 4. This reduces the change over time in the state of the wafer W after the profile measurement by the front height detection unit 5. As a result, the height position of the surface of the wafer W can be more appropriately detected by the coaxial AF device 4, reflecting the profile measurement results by the front height detection unit 5.

[0060] 10(c), the front height detection unit 5 is located in the negative X-axis direction and the positive Y-axis direction relative to the coaxial AF device 4, and the rear height detection unit 6 is located in the positive X-axis direction and at the same position (on the same processing line) in the positive Y-axis direction. That is, the front height detection unit 5 is located forward in the Y-axis direction relative to the coaxial AF device 4, and the rear height detection unit 6 is located on the same processing line. With this positional relationship, the front height detection unit 5 measures the profile of the entire length of the dicing street before processing, the coaxial AF device 4 detects the height position of the surface of the wafer W while the processing laser irradiation device 3 processes the wafer W, and the rear height detection unit 6 measures the profile after processing in real time to determine the state.

[0061] 10(d), the front height detection unit 5 and the rear height detection unit 6 are located on the same processing line as the coaxial AF device 4. This positional relationship can shorten the time interval between the profile measurement by the front height detection unit 5 and the detection of the height position of the surface of the wafer W by the coaxial AF device 4. In addition, the rear height detection unit 6 can measure the profile after processing in real time and determine the state.

[0062] The front height detection unit 5 and the rear height detection unit 6 can be moved to any position in the X and Y directions relative to the coaxial AF device 4, and can therefore be set to a position according to the user's request.

[0063] The positional relationship in the XY plane between the coaxial AF device 4 and the front height detection unit 5 is not limited to the positional relationship shown in Fig. 10 as long as the front height detection unit 5 is located rearward in the machining progress direction, and the positional relationship in the XY plane between the coaxial AF device 4 and the rear height detection unit 6 is not limited to the positional relationship as described above as long as the rear height detection unit 6 is located rearward in the machining progress direction. Note that the front height detection unit 5 may be located in the Y direction of the coaxial AF device 4, and the rear height detection unit 6 may be located in the Y direction of the coaxial AF device 4.

[0064] Next, an example of a method for processing the wafer W will be described in detail below. When a processing apparatus is equipped only with a coaxial AF device as a means for detecting the height position of the surface of the wafer W, the processing apparatus detects the height position of the surface of the wafer W simultaneously with the timing of processing the wafer W. Therefore, if the coaxial AF device can track the surface of the wafer W, the height position of the surface of the wafer W can be accurately detected, as shown in FIG. 11(a). However, if the processing speed is increased or if the height position of the surface of the wafer W fluctuates significantly and the coaxial AF device's tracking performance is insufficient for the surface of the wafer W, a delay occurs in the response of the detector that detects the AF detection light L2 to the fluctuations (FIG. 11(b)), and the height position of the surface of the wafer W may not be accurately detected. To address this issue, it is conceivable to reduce the response delay by, for example, increasing the AF gain. However, if the coaxial AF device cannot track the unevenness of the surface of the wafer W, causing signal overshoot or fluctuation, as shown in FIG. 11(c), the height position of the surface of the wafer W may not be accurately detected.

[0065] To address the above-mentioned issues, the front height detection unit 5 transmits information about the detected height (height information) to the detection condition setting unit 75 of the coaxial AF device 4. This optimizes the detection conditions for the height position of the surface of the wafer W by the coaxial AF device 4. Therefore, the coaxial AF device 4 and the front height detection unit 5 can accurately detect the height position of the surface of the wafer W.

[0066] The flow of operation of the processing device 1 will be described. FIG. 12 is a sequence diagram showing the flow of operation of the processing device 1. FIG. 13 is a schematic diagram showing a plurality of planned processing points P'. In FIG. 13, the lth dicing street S l and the l+1th dicing street S l+1 The subscript of the planned machining point P' or the machining point P indicates the position of the planned machining point P' or the machining point P. For example, the planned machining point P l,m ' indicates that the planned processing point is the lth dicing street S l In this example, the front height detection unit 5 is located at the m-th position of the planned processing point P 1,m', and the coaxial AF device 4 and the processing laser irradiation device 3 are positioned at the processing point P 1,m-1 The rear height detection unit 6 is disposed at the processing point P 1+1,m-2 The processing flow will be explained assuming that the nozzle is placed at the position shown in FIG.

[0067] The front height detection unit 5 detects the planned processing point P of the wafer W. 1,m Detect the height position of the ' and set the processing point P 1,m The front height detection unit 5 further transmits the height position information of the planned processing point P' to the detection condition setting unit 75 of the coaxial AF device 4 (step Sa1). 1,m The height position information of the rear height detector 6 is transmitted to the detection condition setting unit 75 of the rear height detector 6 (step Sa2).

[0068] Next, the control unit 7 controls the stage 2 (step Sb1) to set the target processing point P 1,m ' to the next planned processing point P 1,m+1 ' (Step Sb2). 1,m ' to the next planned processing point P 1,m+1 ', and the coaxial AF device 4 and the processing laser irradiation device 3 move to the previous processing point P 1,m-1 From the planned processing point P 1,m ', and the rear height detection unit 6 moves to the processing point P 1+1,m-2 From machining point P 1+1,m-1 Go to.

[0069] Next, the control unit 7 determines the planned processing point P 1,m The detection conditions (height position detection conditions) of the reflected light of the AF detection light L2 for the target processing point P' are set (step Sc1). 1,m The height position of the planned machining point P 1,m After irradiating the AF detection light L2 onto the target point P 1,mThe reflected light of the AF detection light L2 reflected on the surface of the AF detection light L1 is detected by the detector 48. The detector 48 divides and receives the focused image of the reflected light of the AF detection light L2, and outputs an output signal according to the amount of light for each divided image to the AF signal processing unit 74. The AF signal processing unit 74 generates an AF signal E based on the output signal. Next, the AF signal processing unit 74 transmits the AF signal E to the processing condition setting unit 72 of the processing laser irradiation device 3 (step Sc3). Here, the coaxial AF device 4 detects the target processing point P based on the appropriate detection conditions. 1,m The height position of the ' can be detected.

[0070] Next, the processing condition setting unit 72 sets the processing conditions based on the AF signal E, and the processing laser light source 31 irradiates the laser light L1 to the processing target point P 1,m ' is machined (step Sd1). Therefore, the planned machining point P 1,m ' is the machining point P 1,m At this time, the coaxial AF setting unit 73 controls the driving of the movable lens driving means 45 so that the output of the AF signal E becomes zero. Furthermore, based on the processing conditions set by the processing condition setting unit 72, the driving of the condenser lens driving means 34 is controlled to adjust the Z-direction position of the focal point of the processing laser beam L1. As a result, a modified region R is formed at the processing point P.

[0071] Processing point P 1+1,m-1 The rear height detection unit 6 located at the processing point P 1+1,m-1 Next, the rear height detection unit 6 detects the surface height position of the processing point P 1+1,m-1 In detail, the front height detection unit 5 determines the state and abnormality of the planned machining point P 1+1,m-1 '(Processing point P 1+1,m-1 ) and the height position of the processing point P by the rear height detection unit 6 1+1,m-1 The state determination unit 76 compares the height position of the processing point P with the height position of the processing point P, and determines that the surface state is good if the difference is equal to or less than a desired threshold value. The threshold value is set using the height position of the surface of the wafer W detected by the front height detection unit 5 as a reference value. 1+1,m-1The determination result of the surface condition is transmitted (step Se3). If the determination result is poor or if an abnormality is detected, the control unit 7 may stop the operation of the processing device 1.

[0072] The above steps Sa1 to Sd3 are repeated to machine all of the planned machining points P'. Whether all of the planned machining points P' have been machined is determined by checking the information on the planned machining points P' registered in the recipe against the machining results. For example, it is determined whether the number of machining points P machined by the machining device 1, which is stored in the memory of the control unit 7, matches the number of planned machining points P' in the recipe. It is also determined in the same way whether the surface condition has been detected and determined for all of the machining points P.

[0073] Fig. 14 is a graph showing an example of the detection results of the height position of a wafer using a coaxial AF device. Fig. 14 shows an example of the detection results of the height position of the surface of the wafer W on an arbitrary dicing street when the detection conditions are optimized based on the AF signal E generated by the AF signal processing unit 74. Fig. 14 shows area A, where the dicing street has steep irregularities, and area B, which has a gentler surface compared to area A. Here, by optimizing the detection conditions as described above, the AF signal processing unit 74 can accurately detect the height position of the dicing street in both areas A and B.

[0074] FIG. 15 shows an example of the detection result of the wafer height position using a conventional method. FIG. 15 also shows the result of detecting the height positions of the BG tape and the surface of the wafer W using only a coaxial AF device without using a front height detection unit. In FIG. 15, area C corresponds to the edge of the wafer W, and area D corresponds to the area closer to the center than the edge of the wafer W. When the wafer W is ground by backgrinding, the height position of the wafer W is likely to be disturbed at the edge of the wafer W due to over-grinding or non-uniformity of the pattern device on the front side of the wafer W. Therefore, it is difficult to accurately detect the height position using only a conventional coaxial AF device. However, by using height position information previously acquired by the front height detection unit 5, the detection accuracy of the height position is improved. As described above, even when there are steep irregularities on the dicing tape, dicing frame, etc., it is possible to accurately detect the height position of the surface of the wafer W by detecting the height position of the surface of the wafer W in advance and setting in advance optimal detection conditions for the height position of the surface of the wafer W by the coaxial AF device 4. Note that, as described above, the detection condition setting unit 75 may set, for example, an AF gain setting value as the detection condition.

[0075] Although the embodiments of the present invention have been described above, the technical scope of the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

[0076] The coaxial AF device 4 is configured to detect the height position of the surface of the wafer W using the knife-edge method, but the coaxial AF device is not limited to this. The coaxial AF device may be configured to apply a commonly known method such as the astigmatism method, for example.

[0077] In addition, in the above embodiment, the control unit comprehensively controls the processing device 1, but multiple control units may control the processing device 1. In addition, the control unit may be provided integrally with the processing device, or may be provided separately.

[0078] The control unit 7 may be composed of a wafer transport means, an operation panel, a television monitor, an indicator light, and the like.

[0079] The operation panel may be equipped with switches and a display device for controlling the operation of each part of the processing device. The television monitor can display wafer images captured by the CCD camera, program contents, various messages, etc. The indicator light displays the operating status of the processing device 1, such as processing in progress, processing completion, emergency stop, etc.

[0080] For example, within the scope of the present invention, the components in the above-described embodiments may be replaced with well-known components, and the above-described modifications may be combined as appropriate. [Explanation of symbols]

[0081] 1 Processing equipment 2 Stage 3. Laser irradiation equipment for processing 4 Coaxial height detector 5 Front height detection unit 6 Rear height detection unit 7 Control Unit

Claims

1. a processing laser irradiation device that irradiates a processing laser beam while moving in a traveling direction along a plurality of dicing streets extending in at least one direction of the wafer; a coaxial height detection unit that has the same optical axis as the processing laser light, irradiates a detection laser light onto the surface of the wafer, and detects the height position of the surface of the wafer based on the reflected light of the detection laser light; a front height detection unit located in front of the processing laser irradiation device; a rear height detection unit located rearward on the opposite side to the front with respect to the processing laser irradiation device, the front height detection unit is movable in a parallel direction of the plurality of dicing streets and detects a height position of the dicing streets before processing by the processing laser irradiation device; The rear height detection unit is movable in a parallel direction of the plurality of dicing streets and detects the height positions of the dicing streets after processing by the processing laser irradiation device.

2. The processing apparatus according to claim 1 , wherein the height information acquired by the front height detection unit is used to correct the height position of the wafer surface.

3. 3. The processing device according to claim 1, wherein a surface condition of the dicing street after processing is determined based on the height information acquired by the front height detection unit and the height information acquired by the rear height detection unit.

4. 3. The processing apparatus according to claim 1, further comprising: a processing unit configured to detect an abnormality in the surface condition of the wafer.

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