Processing device and processing method

Abstract

To provide a processing device and a processing method which enable a high-precision measurement of a surface position of a workpiece and a high-precision processing of the workpiece in the case of laser-processing the workpiece having a coating film.SOLUTION: A processing device which irradiates a workpiece having a coating film with a processing laser beam from the coating film side, comprises: a processing laser irradiation part for irradiating it with the processing laser beam; a coaxial measurement part for irradiating it with a measurement laser beam having the same optical axis as an optical axis of the processing laser beam to measure a position of a surface of the workpiece on the basis of a reflected beam of the measurement laser beam; and a forward measurement part for measuring a position of an interface possessed by the coating film, wherein a focal position of the measurement laser beam irradiated by the coaxial measurement part is calibrated on the basis of the position of the interface possessed by the coating film measured by the forward measurement part.SELECTED DRAWING: Figure 3

Description

[Technical Field]

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

[0002] In processing workpieces such as semiconductor wafers, the workpiece may be attached to tape and laser processed. In this laser processing, a laser beam that is transparent to the tape is irradiated from the tape side to process the workpiece (for example, Patent Document 1). That is, the laser beam is incident on the workpiece through the tape, and a modified region is formed in the workpiece.

[0003] Generally, in a technology for processing a workpiece by irradiating the workpiece with laser light via tape, a laser light (measurement laser light) is irradiated from the tape side to measure the surface position of the workpiece (the position of the contact surface between the tape and the workpiece), and the surface position of the workpiece is measured.The processing laser light is focused at a predetermined position inside the workpiece using information on the measured surface position.A modified region is formed at the focused position of the processing laser light. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-192367 Summary of the Invention [Problem to be solved by the invention]

[0005] Tape applied to workpieces typically consists of a base layer and an adhesive layer, and the thickness of each layer varies depending on the position. When detecting the surface position of a workpiece by irradiating a measurement laser beam from the tape side, this variation can cause discrepancies between the measured surface position of the workpiece and the actual surface position. As a result, the focusing position of the processing laser may deviate from the target position. Furthermore, if the surface of the workpiece has streets (processing lines) or device surfaces, these irregularities can prevent the tape from adhering tightly, creating a gap between the tape and the workpiece. This gap also affects the measurement of the workpiece's surface position, resulting in inaccurate measurement results.

[0006] Furthermore, the same problem as above can occur when a workpiece having an oxide film or the like on its surface is irradiated with a measuring laser beam from the oxide film side, not limited to tape.

[0007] The present invention has been made in consideration of the above circumstances, and aims to provide a processing device and a processing method that, when laser processing a workpiece having a coating film, can measure the surface position of the workpiece with high precision and process the workpiece with high precision. [Means for solving the problem]

[0008] <1> A processing apparatus according to one aspect of the present invention is a processing apparatus that irradiates a workpiece having a coating film with processing laser light from the side of the coating film, and includes a processing laser irradiation unit that irradiates the processing laser light, a coaxial measurement unit that irradiates measurement laser light having the same optical axis as the optical axis of the processing laser light and measures the position of the surface of the workpiece based on the reflected light of the measurement laser light, and a forward measurement unit that measures the position of the interface of the coating film before it is irradiated with the processing laser light, and corrects the focusing position of the measurement laser light irradiated by the coaxial measurement unit based on the position of the interface of the coating film measured by the forward measurement unit. <2> the above <1> In the processing apparatus described above, the forward measurement unit may measure the position of the interface of the coating film before being irradiated with the processing laser light at a position shifted from the scanning position of the processing laser light. <3> the above <1> or <2> The processing apparatus described in the item (1) may detect an abnormality in the workpiece based on the position of the interface of the coating film measured by the forward measurement unit.

[0009] <4> A processing method according to another aspect of the present invention is a processing method in which a workpiece having a coating film is irradiated with processing laser light from the coating film side, and includes a processing laser irradiation step of irradiating the processing laser light, a coaxial measurement step of irradiating a measurement laser light having the same optical axis as the optical axis of the processing laser light and measuring the position of the surface of the workpiece based on the reflected light of the measurement laser light, and a forward measurement step of measuring the position of the interface of the coating film before being irradiated with the processing laser light, and correcting the focusing position of the measurement laser light irradiated in the coaxial measurement step based on the position of the interface of the coating film measured in the forward measurement step. [Effects of the Invention]

[0010] According to the present invention, when a workpiece having a coating film is laser-processed, the surface position of the workpiece can be measured with high precision, and the workpiece can be processed with high precision. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic configuration diagram of a processing device according to an embodiment of the present invention. [Figure 2] 1 is a schematic cross-sectional view of a wafer, which is an example of a workpiece placed on a stage. [Figure 3] FIG. 2 is a schematic configuration diagram of a processing device according to the embodiment. [Figure 4] FIG. 2 is a schematic enlarged cross-sectional view of a portion including a tape, a wafer, and a stage. [Figure 5] 10 is a graph showing the output characteristics of an AF signal E. [Figure 6] FIG. 10 is a schematic diagram showing an example of an abnormality. [Figure 7] 1 is a flowchart showing a flow of wafer processing. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, a processing device according to one embodiment of the present invention will be described with reference to the drawings. In the following embodiments, when the number, numerical value, amount, range, etc. of components are mentioned, unless otherwise specified or when it is clearly limited to a specific number in principle, the number is not limited to the specific number, and may be more or less than the specific number.

[0013] Furthermore, when referring to the shape or positional relationship of components, etc., it includes things that are substantially similar or approximate to those shapes, etc., unless otherwise specified or when it is clearly considered otherwise in principle.

[0014] In addition, the drawings may exaggerate characteristic parts to make the features easier to understand, and the dimensional proportions of the components may not be the same as in reality. In addition, in cross-sectional views, hatching of some components may be omitted to make the cross-sectional structure of the components easier to understand.

[0015] 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 unit 3, a coaxial AF unit 4, a forward measurement unit 5, and a control unit 6.

[0016] The stage 2 is movable in the X and Y directions, and moves in the X and Y directions with the wafer W placed thereon during processing of the wafer W. The wafer W is an example of a workpiece.

[0017] FIG. 2 is a schematic cross-sectional view of a wafer W, which is an example of a workpiece placed on a stage. The wafer W is attached to tape T, and the tape T is held by a dicing frame 7. In this state, the wafer W is placed with the side on which the tape T is not attached in contact with the stage 2. In this embodiment, a processing laser beam and a measurement laser beam for measuring the surface position of the wafer W are irradiated toward the wafer W from the tape T side. The tape T is an example of a protective film. Hereinafter, the wafer W and the tape T may be collectively referred to as the measurement object.

[0018] The processing laser irradiation unit 3 irradiates the processing laser light from the tape T side toward the wafer W. The processing laser light is transparent to the tape T. That is, the tape T is a transparent tape. Therefore, the processing laser light enters the inside of the wafer W through the tape T. The processing laser light is scanned in the moving direction as the stage 2 moves. For example, the processing laser light is irradiated while moving in the traveling direction along a plurality of dicing streets (processing lines) extending in at least one direction of the wafer W. 3, the processing laser irradiation unit 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.

[0019] The processing laser light source 31 emits a processing laser light L1 for forming a modified region inside the wafer W. The processing laser light L1 emitted by the processing laser light source 31 has, for example, 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 measurement laser light L2 emitted from a coaxial AF unit 4 described later.

[0020] The condenser lens driving means 34 moves in the thickness direction (Z direction) of the wafer W based on the processing conditions set by the control unit 6 and also reflects the measurement results of the wafer W by the coaxial AF unit 4 (coaxial measurement unit) 4. As a result, the condenser lens 33 moves in the thickness direction of the wafer W to follow the displacement of the surface of the wafer W, and the focal point of the processing laser beam L1 is positioned at a certain 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.

[0021] The coaxial AF unit 4 irradiates the upper surface W1 of the wafer W with a measurement laser beam L2 having the same optical axis as the processing laser beam L1, and measures the position of the upper surface W1 of the wafer W based on the reflected light of the measurement laser beam. The coaxial AF unit 4 is an example of a coaxial measurement unit. As shown in FIG. 3 , the coaxial AF unit 4 irradiates the upper surface W1 of the wafer W with the measurement laser beam L2, and measures the height position of the upper surface W1 of the wafer W based on the reflected light. The second optical path OP2, which is the optical path of the measurement laser beam 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 beam L1. A condenser lens 33 is disposed on this shared optical path. Therefore, the optical axis of the measurement laser beam L2 is the same as the optical axis of the processing laser beam L1 immediately before the measurement laser beam L2 reaches the wafer W. The coaxial AF unit 4 moves in the processing progress direction together with the processing laser irradiation unit 3 in accordance with the movement of the stage 2, and measures the position of the upper surface W1 of the wafer W.

[0022] 3, the coaxial AF unit 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 unit 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 measurement laser 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 measurement laser light L2 has a wavelength different from that of the processing laser light L1, and has a wavelength that can pass through the tape T and be reflected by the surface of the wafer W.

[0024] 3, the measurement laser 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 then condensed by the condenser 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 measurement laser beam L2 at a position independent of the optical path shared with the first optical path OP1 of the processing laser beam L1. Specifically, the focusing optical system 44 is disposed between the dichroic mirror 32 and the half mirror 46 on an AF light reflection path 244. The AF light reflection path 244 is a path for guiding the reflected light of the measurement laser beam L2 reflected by the surface of the wafer W to the detector 48.

[0026] The focusing 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 measurement laser beam L2 in the Z direction independently of the focal point of the processing laser beam L1. The focusing optical system 44 includes, in order from the wafer W side, a fixed lens 441 immovably provided along the second optical path OP2, and a movable lens 442 movably provided 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 processing laser beam L1 remains fixed, and the Z-direction position of the focal point of the measurement laser beam L2 changes depending on the direction and amount of movement of the movable lens 442. In other words, the relative distance between the focal point of the processing laser beam L1 and the focal point of the measurement laser beam L2 changes.

[0028] The measurement laser 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] Detector 48 is made of a two-part photodiode having a two-part light receiving element (photoelectric conversion element). In detail, detector 48 receives the divided focused image of the reflected light of measurement laser beam L2, and transmits output signals (electrical signals) corresponding to the respective light intensities to control unit 6.

[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 unit 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 beam L1 and the second optical path OP2 of the measurement laser beam 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 the Z-direction position of the focal point of the processing laser beam L1 relative to the wafer W but also the Z-direction position of the focal point of the measurement laser beam L2 relative to the wafer W changes. In this way, even when the relative distance between the condenser lens 33 and the wafer W changes, by moving the movable lens 442, the focal point of the measurement laser beam L2 can be made to coincide with the upper surface W1 of the wafer W while keeping the Z-direction position of the focal point of the processing laser beam L1 fixed.

[0032] The front measurement unit 5 measures the position of the interface of the tape T before the processing laser light L1 is irradiated at a position different from the optical axis of the processing laser light L1. The front measurement unit 5 measures, for example, the position of the upper surface T1 of the tape T. The front measurement unit 5 can also detect abnormalities in the measurement object.

[0033] Here, with reference to FIG. 4, the interface of the tape T, the position of which is measured by the forward measurement unit 5, will be described. FIG. 4 is a schematic enlarged cross-sectional view of a portion including the tape, wafer, and stage. As shown in FIG. 4, the tape T is composed of a base layer Tb and an adhesive layer Ta. The base layer Tb and adhesive layer Ta of the tape T are laminated, so there is an interface between them. By selecting or combining appropriate sensors, the forward measurement unit 5 can measure the position of at least one of the upper surface Tb1 (upper surface T1 of the tape T) and lower surface Tb2 of the base layer Tb, and the upper surface Ta1 and lower surface Ta2 of the adhesive layer Ta. The thickness of the base layer Tb is, for example, approximately 25 to 150 μm, and the thickness of the adhesive layer Ta is, for example, 10 to 30 μm, or 100 μm or more.

[0034] In addition, in this embodiment, tape T (transparent tape) is given as an example of a coating film, but the coating film may be a tape other than tape T, for example, a tape having multiple interfaces, or an oxide film, etc.

[0035] The specific configuration of the forward measurement unit 5 for measuring the interface position of the tape T (peritoneum) is appropriately selected depending on the measurement target. The forward measurement unit 5 may have an AF mechanism like the coaxial AF unit 4, or may be another optical displacement sensor, a linear approach type displacement sensor, or an ultrasonic displacement sensor.

[0036] If the forward measurement unit 5 has an AF mechanism, a light source with any wavelength can be selected as the light source. The optical axis of the measurement laser light L2 of the coaxial AF unit 4 is coaxial with the optical axis of the processing laser light L1 of the processing laser irradiation unit 3. The wavelength of the processing laser light L1 is, for example, 1064 to 1400 nm. Because the optical axis of the measurement laser light L2 is coaxial with the optical axis of the processing laser light L1, the measurement laser light L2 cannot use wavelengths similar to those of the processing laser light L1, and the wavelength of the laser light that can be used is limited. This is because if light with a wavelength close to that of the processing laser light L1 is used for the measurement laser light L2, the transmittance of the wafer W increases, and the reflection of the measurement laser light L2 from the surface of the wafer W is weakened. Furthermore, to enable the use of light with a wide range of wavelengths for the measurement laser light L2 while the optical axis of the measurement laser light L2 is coaxial with the optical axis of the processing laser light L1, coatings compatible with a wide range of wavelengths are required for the condenser lens, mirrors used in the optical path, etc. In this case, the reflectance and transmittance decrease as the wavelength deviates from the corresponding wavelength. Therefore, even in this case, the wavelength of the laser light that can be used for the measurement laser light L2 is limited. On the other hand, if the forward measurement unit 5 has an AF mechanism, it can irradiate light from a position different from the optical axis of the processing laser light L1, so the wavelength of the light emitted by the forward measurement unit 5 is not limited by the processing laser light L1. The light irradiated by the forward measurement unit 5 may be laser light of any wavelength or white light. In the case of white light, the position of the interface of the tape T can be measured based on information obtained by dispersing the light reflected from the tape T using a spectroscope.

[0037] Examples of optical displacement sensors include a triangulation type sensor, a coaxial confocal type sensor, and a spectroscopic interference type sensor.

[0038] Examples of triangulation sensors include sensors that use position sensitive detectors (PSDs), sensors that use image sensors, sensors that use specular or diffuse reflection, sensors that use line beams or spot beams, and light-section sensors.

[0039] Triangulation sensors are suitable for measuring the interface position of coating films with small variations in reflectance across the measurement area. Furthermore, because the spot size of triangulation sensors can change, they are preferably used for coating films with small variations in interface position. On the other hand, triangulation sensors can also average the measured position by increasing the measurement spot size.

[0040] A coaxial confocal sensor can irradiate light having multiple wavelengths (e.g., white light) and individually receive the reflected light of each wavelength, making it applicable to coating films with multiple interfaces. Furthermore, since the beam size of a coaxial confocal sensor hardly changes even when the measurement distance changes, stable measurements can be made regardless of fluctuations in the position of the interface. Therefore, it is preferable that the forward measurement unit 5 be a coaxial confocal sensor.

[0041] Spectral interference sensors are less affected by the intensity of reflected light, making them suitable for measuring coatings with varying reflectance, such as clothing films with uneven color or thickness.

[0042] The front measurement unit 5 measures the position of the top surface T1 of the tape T, and the position information of the top surface T1 is reflected in the measurement of the position of the top surface W1 of the wafer W by the coaxial AF unit 4, thereby improving the measurement accuracy of the top surface W1. For example, the coaxial AF unit 4 corrects the focusing position of the measurement laser light L2 by the difference between the thickness of the tape T calculated based on the surface position of the tape T and the average thickness of the tape T. The measurement laser light L2 is irradiated at the corrected position to measure the position of the top surface W1 of the wafer W. By reflecting the surface position information of the tape T in the scanning of the coaxial AF unit 4, the accuracy of the focusing position of the measurement laser light L2 can be further improved. Furthermore, if the focusing position of the measurement laser light L2 deviates from a predetermined range, it can be corrected in real time. When a plurality of interfaces exist on the tape T, the accuracy of the focusing position of the measurement laser light L2 can be further improved based on the position information of the plurality of interfaces.

[0043] It is preferable that the front measurement unit 5 measures the interface position of the tape at a position shifted from the scanning position of the processing laser light L1. For example, when the wafer W is processed along a dicing street (processing line), it is preferable that the front measurement unit 5 measures the interface position of the tape on an unprocessed dicing street (before irradiation with the processing laser light L1), which is different from the dicing treat to which the processing laser light L1 is irradiated. By having the front measurement unit 5 measure the interface position of the tape at a position shifted from the scanning position of the processing laser light L1, it is possible to ensure sufficient analysis time before measurement by the coaxial AF unit 4, and productivity can be maintained.

[0044] Furthermore, the forward measuring unit 5 may be movable in front of the coaxial measuring unit 4 relative to the coaxial AF unit 4 in at least one of the X direction and the Y direction.

[0045] The control unit 6 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 6 controls, for example, the above-mentioned operations of the stage 2, processing laser irradiation unit 3, coaxial measurement unit 4, and forward measurement unit 5. The control unit 6 controls the operation of the processing device 1 based on preset control conditions called a recipe.

[0046] The control unit 6 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 unit 3, the coaxial measurement unit 4, and the forward measurement unit 5.

[0047] The control unit 6 generates an AF signal E, AF data, AF information, or the like as a displacement signal (detection signal) indicating a displacement (defocus distance) of the upper surface W1 of the wafer W from a reference position in the Z direction based on the output signal output from each light-receiving element of the detector 48. For example, the AF signal corresponds to the height position of the upper surface W1 of the wafer at a predetermined position of the wafer W. In other words, the position of the upper surface W1 of the wafer W is measured based on the output signal output from each light-receiving element of the detector 48.

[0048] 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 upper surface W1 of the wafer W, and the vertical axis represents the output value of the AF signal E. It is assumed that the focal point of the measurement laser light L2 is adjusted in advance to coincide with the reference position (origin) on the upper surface W1 of the wafer W.

[0049] 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 W1 of the wafer W as the zero-cross point. Furthermore, when the position of the top surface W1 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 W1 of the wafer W can be detected, the relationship between the displacement of the top surface W1 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 W1 of the wafer W is at a focal position that coincides with the focal point of the measurement laser light L2. On the other hand, if the output of the AF signal E is not zero, the displacement direction and amount of the top surface W1 of the wafer W can be determined.

[0050] The control unit 6 determines whether the AF signal E (height position of the upper surface W1 of the wafer W) is located within a predetermined range. Note that the control unit 6 does not have to determine whether the height position of the upper surface W1 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 W1 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 measurement laser light L2 is located on the upper surface W1 of the wafer W, is located within the predetermined range.

[0051] 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 measurement accuracy of the height position of the upper surface W1.

[0052] As described above, the control unit 6 drives the coaxial AF unit 4 using information on the interface position of the tape T. Therefore, the position of the upper surface W1 of the wafer W can be measured more accurately.

[0053] The control unit 6 can detect abnormalities in the measurement object. The coaxial AF unit 4 and the forward measurement unit 5 measure the position of the top surface W1 of the wafer W or the interface of the tape T while moving from an area where the wafer W is not attached and only the tape T is present. When moving from an area A where only the tape T is present (see FIG. 2) to an area B where the wafer W is attached (see FIG. 2), the coaxial AF unit 4 may not be able to detect the top surface W1 of the wafer W. Specifically, in tape-through processing, the interface of the tape T may be mistakenly detected as the top surface W1 of the wafer W. However, the forward measurement unit 5 measures the position of the interface of the tape T before the coaxial AF unit 4 measures the position of the top surface W1 of the wafer W. Therefore, the control unit 6 can more accurately measure the position of the top surface W1 of the wafer W by excluding the interface of the tape T, for example, the vicinity of the position of the top surface T1 of the tape T, from the detection target in the measurement by the coaxial AF unit 4. In this way, the control unit 6 can prevent the coaxial AF unit 4 from detecting an abnormality.

[0054] Furthermore, the control unit 6 can detect abnormalities in the measurement object based on the position of the interface of the tape T. Fig. 6 is a schematic diagram showing an example of an abnormality. In Fig. 6(A), there is an abnormality in the thickness of the tape T. The front measurement unit 5 measures the position of the upper surface T1 (upper surface Tb1 of the base layer Tb) of the tape T. If the position of the upper surface Tb1 is not within a predetermined range, the control unit 6 can determine that an abnormality has occurred in the measurement object. In Figure 6(B), a gap S occurs between the wafer W and the tape T (adhesive layer Ta). The front measurement unit 5 measures the position of the lower surface Ta2 of the adhesive layer Ta. If the position of the lower surface Ta2 is not within a predetermined range, the control unit 6 can determine that an abnormality has occurred in the measurement object. In Figure 6(C), a foreign object C is present inside the tape T. The front measurement unit 5 measures the position of the upper surface Ta1 or the lower surface Ta2 of the adhesive layer Ta. If the position of the upper surface Ta1 or the lower surface Ta2 is not within a predetermined range, the control unit 6 can determine that an abnormality has occurred in the measurement object. In FIG. 6(D), a device D is formed on the surface of a wafer W. Because the device D protrudes from the wafer W, the tape T does not adhere tightly to the device D, creating a gap S in the vicinity of the device D. The front measurement unit 5 measures the position of the lower surface Ta2 of the adhesive layer Ta. If the position of the lower surface Ta2 is not within a predetermined range, the control unit 6 can determine that an abnormality has occurred in the measurement object. In FIG. 6(E), a foreign substance C is present on the surface of the wafer W. Because the foreign substance C is present on the wafer W, the tape T does not adhere closely to the foreign substance C, creating a gap S in the vicinity of the foreign substance C. The front measurement unit 5 measures the position of the lower surface Ta2 of the adhesive layer Ta. If the position of the lower surface Ta2 is not within a predetermined range, the control unit 6 can determine that an abnormality has occurred in the measurement object.

[0055] If the measurement target has an abnormality as described above, the processing laser beam L1 may not be focused at the set position, or the desired processing state may not be obtained. However, because the control unit 6 can detect the abnormality, the wafer W in which an abnormality is detected can be removed from the stage 2 without being processed, preventing the generation of defective products.

[0056] Next, an example of the flow of processing the wafer W will be described in detail below with reference to Fig. 7. Fig. 7 is a flowchart showing the flow of processing the wafer W. A recipe is created in advance for processing the wafer W. This recipe includes tape information (such as the average thickness of the tape T, the average thickness of the base layer Tb, and the average thickness of the adhesive layer Ta). The recipe also includes conditions for detecting anomalies (such as a threshold value for the tape interface position).

[0057] First, the forward measurement unit 5 measures the interface position of the tape T (step S1). The control unit 6 determines whether there is any abnormality in the measurement object (step S2). If the interface position is outside a predetermined threshold range or if a foreign object is detected (step S2 / NO), the operation of the processing device 1 is stopped. Furthermore, for example, position information of the upper surface T1 of the interface of the tape T is reflected in the scanning of the coaxial AF unit 4, and position information of the upper surface Ta1 and the lower surface Ta2 of the adhesive layer Ta is used for abnormality detection.

[0058] If there is no abnormality in the measurement object, for example, if the interface position of the tape T is within the threshold range and no foreign matter is detected (step S2 / YES), the information on the interface position is used to drive the coaxial AF unit 4. For example, while correcting the focusing position of the measurement laser light L2 of the coaxial AF unit 4 by the difference between the thickness of the tape T calculated based on the position of the top surface T1 of the tape T and the average thickness of the tape T, the measurement laser light L2 is irradiated to the corrected position to measure the position of the top surface W1 of the wafer W (step S3, coaxial measurement step, forward measurement step).

[0059] Next, based on the position information of the upper surface W1 of the wafer W, the inside of the wafer W is irradiated with a processing laser light L1 to process the wafer W (step S4, processing laser irradiation step).

[0060] Next, the control unit 6 determines the processing state (step S5). The control unit 6 determines whether the depth or width of the crack formed after irradiation with the processing laser light L1, measured using the measurement laser light L2, is within a predetermined threshold range. If the crack depth or width is outside the threshold range (step S5 / NO), the operation of the processing device 1 is stopped. On the other hand, if the crack depth is within the threshold range (step S5 / YES), the stage 2 is moved and steps S1 to S5 are repeatedly performed. When processing of all processing points is completed, the operation of the processing device 1 is stopped.

[0061] 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.

[0062] The coaxial AF unit 4 is configured to measure the height position of the surface of the wafer W using the knife-edge method, but the coaxial AF unit is not limited to this. The coaxial AF unit may be configured to apply a commonly known method such as the astigmatism method.

[0063] 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.

[0064] The control unit 6 may be composed of a wafer transport means, an operation panel, a monitor, an indicator light, and the like.

[0065] The operation panel may be equipped with switches and a display device for controlling the operation of each part of the processing device. The monitor can display wafer images captured by a 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.

[0066] Furthermore, in the above embodiment, abnormalities are detected by measuring the position of the interface of the coating film (tape T), but the control unit 6 may determine that an abnormality has occurred in the object to be measured by the forward measurement unit 5 detecting the foreign matter C itself.

[0067] Furthermore, within the scope of the present invention, the components in the above-described embodiments may be replaced with well-known components as appropriate, and the above-described modifications may be combined as appropriate. [Explanation of symbols]

[0068] 1 Processing equipment 3. Laser irradiation unit for processing 4 Coaxial AF section (coaxial measurement section) 5 Front measurement section 6 Control Unit L1 Laser beam for processing L2 Measurement laser light T-tape Ta adhesive layer Tb base material layer W wafer

Claims

1. A processing device that irradiates a processing laser beam onto a workpiece having a coating film from the coating film side, a processing laser irradiation unit that irradiates the processing laser light; a coaxial measurement unit that irradiates a measurement laser beam having the same optical axis as the optical axis of the processing laser beam and measures the position of the surface of the workpiece based on the reflected light of the measurement laser beam; a forward measurement unit that measures the position of the interface of the coating film before the processing laser light is irradiated, The processing device corrects the focusing position of the measurement laser light irradiated by the coaxial measurement unit based on the position of the interface of the coating film measured by the forward measurement unit.

2. 2. The processing device according to claim 1, wherein the forward measurement unit measures the position of the interface of the coating film before irradiation with the processing laser light at a position shifted from a scanning position of the processing laser light.

3. 3. The processing apparatus according to claim 1, wherein an abnormality in the workpiece is detected based on the position of the interface of the coating film measured by the forward measuring unit.

4. A processing method in which a workpiece having a coating film is irradiated with processing laser light from the coating film side, a processing laser irradiation step of irradiating the processing laser light; a coaxial measurement step of irradiating a measurement laser beam having the same optical axis as the optical axis of the processing laser beam and measuring the position of the surface of the workpiece based on the reflected light of the measurement laser beam; a forward measurement step of measuring a position of an interface of the coating film before the coating film is irradiated with the processing laser light, The processing method includes correcting a focusing position of the measurement laser light irradiated in the coaxial measurement step based on the position of the interface of the coating film measured in the forward measurement step.

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