A method for inspecting the output state of a laser beam in a laser processing device

Abstract

To make it possible to easily check a delay in rising of a laser beam or presence or absence of light leakage when switching is performed between starting and stopping of irradiation of the laser beam.SOLUTION: An inspection method includes a preparation step 101 of preparing a wafer for inspection, a positioning step 102 of positioning a condenser for condensing a laser beam at a position facing the wafer for inspection after the preparation step 101, a laser processing step 103 of starting irradiation with a laser beam and relatively move the wafer for inspection and the focal point of the laser beam, thereby forming continuous machining marks of a predetermined length on the wafer for inspection after the positioning step 102, and a confirmation step 104 of confirming whether the machining marks have changed in a machining progressing direction immediately after the start of the irradiation with the laser beam.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a method for inspecting the output state of a laser beam in a laser processing device. [Background technology]

[0002] 2. Description of the Related Art In order to manufacture chips by dividing a semiconductor wafer, a method is known in which a modified layer is formed inside the wafer by irradiating the wafer with a focused laser beam, thereby forming division starting points (see, for example, Patent Document 1).

[0003] The laser processing apparatus used for the processing shown in Patent Document 1 can also process so-called multi-project type wafers containing a mixture of devices of different shapes and sizes by switching between starting and stopping laser beam irradiation (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 3408805 [Patent Document 2] JP 2012-125781 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, laser processing equipment has problems in that when laser beam irradiation is started again from a stopped state, a delay in the rise of the laser beam can cause the device to not be divided, and when laser beam irradiation is stopped from a continued state, laser beam light can leak, damaging the device.

[0006] Such problems as delay in the rise of the laser beam and light leakage can be improved by adjusting the output of the RF driver that controls the start and stop of laser beam irradiation.

[0007] However, in order to check for start-up delays and light leakage, a photodetector needs to be installed at the processing point, which requires man-hours and tends to increase the effort required for checking.

[0008] The present invention has been made in consideration of the above-mentioned facts, and aims to provide an inspection method for inspecting the output state of a laser beam of a laser processing device, which makes it possible to easily check for a delay in the rise of the laser beam and the presence or absence of leakage light when switching between starting and stopping irradiation of the laser beam. [Means for solving the problem]

[0009] In order to solve the above-mentioned problems and achieve the object, the inspection method for inspecting the output state of a laser beam of a laser processing apparatus of the present invention is an inspection method for inspecting the output state of a laser beam in a laser processing apparatus that performs discontinuous processing on a workpiece by repeatedly starting and stopping irradiation of a laser beam, and is characterized by including a preparation step of preparing an inspection wafer, a positioning step after the preparation step of positioning a collector that focuses the laser beam at a position facing the inspection wafer, a laser processing step after the positioning step of starting irradiation of the laser beam and moving the inspection wafer and the focal point of the laser beam relatively to form a continuous processing mark of a predetermined length on the inspection wafer, and a confirmation step of confirming whether the processing mark has changed in the processing progress direction from immediately after irradiation of the laser beam started.

[0010] In the inspection method for inspecting the output state of the laser beam of the laser processing device, if the processing mark changes in the processing progress direction immediately after the start of irradiation of the laser beam in the confirmation step, the inspection method may further include an adjustment step of adjusting the output of an RF driver that controls the start and stop of irradiation of the laser beam so that the change in the processing mark disappears.

[0011] The inspection method for inspecting the output state of a laser beam of a laser processing apparatus of the present invention is an inspection method for inspecting the output state of a laser beam in a laser processing apparatus which performs discontinuous processing on a workpiece by repeatedly starting and stopping irradiation of a laser beam, and includes a preparation step of preparing an inspection wafer, a laser processing step of forming continuous processing marks of a predetermined length on the inspection wafer by relatively moving the inspection wafer and the focal point of the laser beam while irradiating the inspection wafer with the laser beam after the preparation step, and stopping the irradiation of the laser beam on the inspection wafer after the laser processing step, and In the direction of processing Beyond the irradiation stop position Previously and a confirmation step of confirming whether or not a mark of the laser beam has been formed.

[0012] In the inspection method for inspecting the output state of the laser beam of the laser processing apparatus, if a laser beam dent is formed on the inspection wafer beyond the irradiation stop position of the laser beam in the confirmation step, the inspection method may further include an adjustment step of adjusting the output of an RF driver that controls the start and stop of irradiation of the laser beam so that a laser beam dent is no longer formed beyond the irradiation stop position.

[0013] In the inspection method for inspecting the output state of the laser beam of the laser processing device, the inspection wafer has at least two metal layers, a first metal layer and a second metal layer, having different specific heats or melting points, laminated on the upper surface of a substrate, and the laser beam may be irradiated from the side where the metal layers are laminated. Effect of the Invention

[0014] The present invention has an effect of making it possible to easily check the rise delay of the laser beam and the state of light leakage when switching between starting and stopping irradiation of the laser beam in a laser processing device. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a perspective view showing an example of the configuration of a laser processing apparatus in which the output state of a laser beam is inspected by the inspection method according to the first embodiment. [Diagram 2] FIG. 2 is a diagram showing a configuration of a laser beam irradiation unit of the laser processing apparatus shown in FIG. [Diagram 3] FIG. 3 is a diagram showing the output of an RF signal applied to an acousto-optic deflection element of the laser beam irradiation unit shown in FIG. 2, and the output of a laser beam emitted by the laser beam irradiation unit through a condenser lens. [Figure 4] FIG. 4 is a diagram showing a change in the output of a laser beam when there is a start-up delay in the laser beam irradiation unit shown in FIG. [Diagram 5] FIG. 5 is a diagram showing a change in the output of a laser beam when there is light leakage from the laser beam irradiation unit shown in FIG. [Figure 6] FIG. 6 is a flowchart showing the flow of the inspection method according to the first embodiment. [Figure 7] FIG. 7 is an exploded perspective view showing the inspection wafer prepared in the preparation step of the inspection method shown in FIG. [Figure 8] FIG. 8 is a cross-sectional view of a wafer for inspection prepared in the preparation step of the inspection method shown in FIG. [Figure 9] FIG. 9 is a plan view showing an example of a single processing mark formed on the test wafer shown in FIG. [Figure 10] FIG. 10 is a side view, partially in cross section, showing a schematic diagram of the positioning step of the inspection method shown in FIG. [Figure 11] FIG. 11 is a side view, partially in cross section, showing a schematic diagram of the laser processing step of the inspection method shown in FIG. [Figure 12] FIG. 12 is a plan view that illustrates a wafer for inspection on which processing marks are formed after the laser processing step of the inspection method shown in FIG. [Figure 13]FIG. 13 is an enlarged plan view of part XIII in FIG. 12, showing a schematic view of processing marks. [Figure 14] FIG. 14 is an enlarged plan view of part XIV in FIG. 12, showing a schematic view of processing marks. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] The form (embodiment) for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited to the contents described in the following embodiment. Furthermore, the components described below include those that a person skilled in the art can easily imagine and those that are substantially the same. Furthermore, the configurations described below can be appropriately combined. Furthermore, various omissions, substitutions, or modifications of the configurations can be made without departing from the gist of the present invention.

[0017] [Embodiment 1] An inspection method for inspecting the output state of a laser beam of a laser processing device according to a first embodiment of the present invention (hereinafter, simply referred to as an inspection method) will be described with reference to the drawings. First, the laser processing device will be described.

[0018] FIG. 1 is a perspective view showing a configuration example of a laser processing apparatus in which the output state of a laser beam is inspected by the inspection method according to the first embodiment. FIG. 2 is a diagram showing the configuration of a laser beam irradiation unit of the laser processing apparatus shown in FIG. 1. FIG. 3 is a diagram showing the output of an RF signal applied to an acousto-optic deflection element of the laser beam irradiation unit shown in FIG. 2, and the output of a laser beam emitted by the laser beam irradiation unit through a condenser lens. FIG. 4 is a diagram showing a change in the output of a laser beam when there is a rise delay in the laser beam irradiation unit shown in FIG. 3. FIG. 5 is a diagram showing a change in the output of a laser beam when there is light leakage from the laser beam irradiation unit shown in FIG. 3.

[0019] (workpiece) The laser processing apparatus 1 shown in Fig. 1 is a processing apparatus that irradiates a pulsed laser beam 21 onto a workpiece 200 and performs laser processing (corresponding to processing) on ​​the workpiece 200. The workpiece 200, which is the processing target of the laser processing apparatus 1 shown in Fig. 1, is a wafer such as a disk-shaped semiconductor wafer or an optical device wafer having a substrate 201 made of silicon, sapphire, SiC, or the like. The workpiece 200 has a plurality of planned division lines that intersect with each other set on a surface 202 of the substrate 201, and devices are formed in each area partitioned by the plurality of planned division lines set on the surface 202.

[0020] The device is, for example, an integrated circuit such as an integrated circuit (IC) or a large scale integration (LSI), or an image sensor such as a charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS).

[0021] Moreover, in the first embodiment, the workpiece 200 has a disk-like adhesive tape 208 having a diameter larger than the outer diameter of the workpiece 200 and an annular frame 207 attached to its outer edge attached thereto, and is supported in an opening 209 of the frame 207 with a back surface 203 behind the front surface 202 facing upward. In the first embodiment, the workpiece 200 is divided into individual devices along the planned division lines by, for example, laser processing using the laser processing device 1 while supported in the opening 209 of the frame 207 by the adhesive tape 208.

[0022] In addition, the workpiece 200 in embodiment 1 includes, as planned division lines, first planned division lines that are straight and spaced apart from each other in the longitudinal direction, second planned division lines that are straight along a direction perpendicular to the first planned division lines and spaced apart from each other in the longitudinal direction, and third planned division lines that connect the intersections of the first planned division lines and the second planned division lines, are straight along a direction that intersects both the first planned division lines and the second planned division lines, and are spaced apart from each other in the longitudinal direction.

[0023] In the present invention, the workpiece 200 may have a first planned division line and a second planned division line that are perpendicular to each other as planned division lines. In the first embodiment, the workpiece 200 is a wafer such as a semiconductor wafer or an optical device wafer, but in the present invention, the workpiece 200 is not limited to a wafer, and may be a package substrate in which a plurality of device chips arranged on a substrate are molded with resin, a glass substrate, or a ceramic substrate.

[0024] (Laser processing equipment) The laser processing device 1 is a device that irradiates a laser beam 21 having a wavelength that is transparent to the substrate 201 constituting the workpiece 200 from the rear surface 203 of the workpiece 200 along a planned dividing line to form a modified layer inside the substrate 201. The modified layer means a region in which the density, refractive index, mechanical strength, and other physical properties are different from those of the surroundings, and examples of the modified layer include a melting process region, a crack region, an insulation breakdown region, a refractive index change region, and a region in which these regions are mixed. The modified layer has a lower mechanical strength than other parts of the substrate 201 of the workpiece 200.

[0025] In the first embodiment, since the workpiece 200 includes the first, second, and third planned division lines as the planned division lines, the laser processing device 1 repeatedly starts and stops irradiation of the laser beam 21 to perform discontinuous (i.e., intermittent) laser processing on the workpiece 200, and forms a discontinuous (i.e., intermittent) modified layer inside the substrate 201 of the workpiece 200. As shown in FIG. 1, the laser processing device 1 has a chuck table 10 that holds the workpiece 200, a laser beam irradiation unit 20, a moving unit 30, an imaging unit (not shown), and a control unit 40.

[0026] The chuck table 10 holds the workpiece 200 on a holding surface 11 that is parallel to the horizontal direction. The holding surface 11 is disk-shaped and made of porous ceramics or the like, and is connected to a vacuum suction source (not shown) via a vacuum suction path (not shown). The chuck table 10 is sucked by the vacuum suction source to suction and hold the workpiece 200 placed on the holding surface 11. A plurality of clamps 12 are arranged around the chuck table 10 to clamp a frame 207 that supports the workpiece 200 in an opening 209.

[0027] Furthermore, the chuck table 10 is rotated by the rotary movement unit 34 of the moving unit 30 about an axis parallel to the Z-axis direction which is perpendicular to the holding surface 11 and parallel to the vertical direction. The chuck table 10, together with the rotary movement unit 34, is moved in the X-axis direction parallel to the horizontal direction by the X-axis movement unit 31 of the moving unit 30, and is moved in the Y-axis direction which is parallel to the horizontal direction and perpendicular to the X-axis direction by the Y-axis movement unit 32. The chuck table 10 is moved by the moving unit 30 between a processing area below the laser beam irradiation unit 20 and a carry-in / out area away from below the laser beam irradiation unit 20 where the workpiece 200 is carried in and out.

[0028] The laser beam irradiation unit 20 is a unit that irradiates a pulsed laser beam 21 onto a workpiece 200 held on the chuck table 10 to perform laser processing on the workpiece 200 .

[0029] In the first embodiment, a part of the laser beam irradiation unit 20 is supported on the tip of a support 4 supported on an erect wall 3 erected from the apparatus main body 2, as shown in Fig. 1. The laser beam irradiation unit 20 includes a laser oscillator 25 that emits a laser beam 21 having a wavelength that is transparent to a substrate 201 of a workpiece 200, and a condenser 23 that condenses the laser beam 21 emitted from the laser oscillator 25 on the workpiece 200 held on the holding surface 11 of the chuck table 10, as shown in Fig. 2. The laser oscillator 25 includes an excitation LD 22 and a Nd:YVO4 Crystal 243 and Nd:YVO 4 The crystal 243 includes a rear mirror 241 and an output mirror 242 that return the light emitted by the crystal 243 to the receiving side. 4 The light emitted by the crystal 243 is excited and travels back and forth between the rear mirror 241 and the output mirror 242, whereby the light is amplified and laser oscillation occurs. 4 It further includes an acousto-optic deflection element 245 disposed between the crystal 243 and the rear mirror 241 to selectively deflect the optical path of the laser beam 21 to the collector 23 and a damper 247 .

[0030] The acousto-optic deflection means 24 includes an RF (Radio Frequency) driver 244 and an acousto-optic deflection element 245 that pulses the laser beam 21 by an RF (Radio Frequency) signal applied by the RF (Radio Frequency) driver 244 and deflects the traveling direction of the laser beam 21.

[0031] The RF driver 244 adjusts the amplitude of the RF signal applied to the acousto-optic deflection element 245 by the output adjustment means 246. The acousto-optic deflection element 245 can adjust the output of the laser beam 21 in response to the amplitude of the applied RF signal. When the RF signal is applied from the RF driver 244, the acousto-optic deflection element 245 guides the laser beam 21 to a damper 247 and stops the irradiation of the laser beam 21 onto the workpiece 200, etc., as shown in Fig. 3. When the application of the RF signal from the RF driver 244 is stopped, the acousto-optic deflection element 245 guides the laser beam 21 to the condenser 23 and irradiates the laser beam 21 onto the workpiece 200, etc., as shown in Fig. 3.

[0032] In addition, the horizontal axis of Figure 3 indicates the passage of time, the upper vertical axis of Figure 3 indicates the output of the RF signal applied by the RF driver 244 to the acousto-optical deflection element 245, and the lower vertical axis of Figure 3 indicates the output of the laser beam 21 irradiated from the laser beam irradiation unit 20 to the workpiece 200, etc.

[0033] The condenser 23 includes a condenser lens 231 disposed at a position facing the holding surface 11 of the chuck table 10 in the Z-axis direction, and a mirror 232 that reflects the laser beam 21 toward the condenser lens 231. The condenser lens 231 transmits the laser beam 21 and condenses the laser beam 21 at a focal point 211 (shown in FIG. 11).

[0034] The laser beam irradiation unit 20 having the above-mentioned configuration sets the focal point 211 of the pulsed laser beam 21 having a wavelength that is transparent to the workpiece 200 held on the chuck table 10 inside the workpiece 200, and irradiates the workpiece 200 from the back surface 203 side with the laser beam 21 to form a modified layer inside the workpiece 200. The condenser 23 is provided such that at least the condenser lens 231 is movable in the Z-axis direction by a condenser moving unit (not shown).

[0035] In addition, in the laser beam irradiation unit 20 having the above-mentioned configuration, when an RF signal is applied from the RF driver 244 to the acousto-optic deflection element 245, the acousto-optic deflection element 245 stops irradiating the workpiece 200 with the laser beam 21, and when the application of the RF signal from the RF driver 244 is stopped, the acousto-optic deflection element 245 starts irradiating the workpiece 200 with the laser beam 21. In the first embodiment, when the output of the RF signal applied by the RF driver 244 to the acousto-optic deflection element 245 is high, as shown in FIG. 4, even if the application of the RF signal is stopped, a delay (hereinafter referred to as a rise delay) may occur in the rise of the output of the laser beam 21 irradiated by the laser beam irradiation unit 20 to the workpiece 200 as shown by the solid line in FIG. 4, compared to the ideal rise shown by the dashed line in FIG. 4. The occurrence of a rise delay means that it takes longer for the output of the laser beam 21 to reach a desired output than the ideal rise.

[0036] In the first embodiment, when the output of the RF signal applied by the RF driver 244 to the acousto-optic deflection element 245 is low, the laser beam 21 applied to the workpiece 200 by the laser beam application unit 20 is not stopped even when the application of the RF signal is started, and leakage light 212 may occur as shown in Fig. 5. The leakage light 212 refers to the laser beam 21 of the laser beam application unit 20 being intermittently applied even when the application of the RF signal is started. The output of the leakage light 212 of the laser beam 21 is weaker than the output of the laser beam 21 while the application of the RF signal is stopped.

[0037] 4 and 5, the horizontal axis indicates the passage of time, and the vertical axis indicates the output of the laser beam 21 irradiated from the laser beam irradiation unit 20 to the workpiece 200 or the like.

[0038] The moving unit 30 relatively moves the chuck table 10 and the focal point 211 of the laser beam 21 irradiated by the laser beam irradiation unit 20 in the X-axis direction, the Y-axis direction, the Z-axis direction, and around an axis parallel to the Z-axis direction. The X-axis direction and the Y-axis direction are perpendicular to each other and parallel to the holding surface 11 (i.e., the horizontal direction). The moving unit 30 includes an X-axis moving unit 31 which is a processing feed unit that moves the chuck table 10 in the X-axis direction, a Y-axis moving unit 32 which is an indexing feed unit that moves the chuck table 10 in the Y-axis direction, and a rotation moving unit 34 which rotates the chuck table 10 around an axis parallel to the Z-axis direction.

[0039] The Y-axis moving unit 32 is a unit that relatively indexes and feeds the chuck table 10 and the laser beam irradiation unit 20. In the first embodiment, the Y-axis moving unit 32 is installed on the device body 2 of the laser processing device 1. The Y-axis moving unit 32 supports a moving plate 5 that supports the X-axis moving unit 31 so as to be movable in the Y-axis direction.

[0040] The X-axis moving unit 31 is a unit that relatively processes and feeds the chuck table 10 and the laser beam irradiation unit 20. The X-axis moving unit 31 is installed on the moving plate 5. The X-axis moving unit 31 supports a second moving plate 6 that supports a rotational moving unit 34 that rotates the chuck table 10 around an axis parallel to the Z-axis direction, so as to be movable in the X-axis direction. The second moving plate 6 supports the rotational moving unit 34 and the chuck table 10. The rotational moving unit 34 supports the chuck table 10.

[0041] The X-axis moving unit 31 and the Y-axis moving unit 32 each include a well-known ball screw rotatably provided about its axis, a well-known pulse motor for rotating the ball screw about its axis, and a well-known guide rail for supporting the moving plates 5, 6 movably in the X-axis or Y-axis direction. The rotation moving unit 34 includes a motor for rotating the chuck table 10 about its axis, etc.

[0042] The laser processing apparatus 1 also includes an X-axis position detection unit (not shown) for detecting the position of the chuck table 10 in the X-axis direction, a Y-axis position detection unit (not shown) for detecting the position of the chuck table 10 in the Y-axis direction, and a Z-axis position detection unit for detecting the position of the condenser 23 included in the laser beam irradiation unit 20 in the Z-axis direction. Each position detection unit outputs a detection result to the control unit 40.

[0043] The imaging unit includes a plurality of imaging elements for imaging the workpiece 200 held on the chuck table 10. The imaging elements are, for example, a charge-coupled device (CCD) imaging element or a complementary metal-oxide semiconductor (CMOS) imaging element. The imaging unit images the workpiece 200 held on the holding surface 11 of the chuck table 10, obtains an image for performing alignment between the workpiece 200 and the laser beam irradiation unit 20, and outputs the obtained image to the control unit 40. In the first embodiment, the imaging unit is supported on the tip of the support 4 and disposed at a position aligned with the condenser lens 231 of the laser beam irradiation unit 20 in the X-axis direction.

[0044] The control unit 40 controls the above-mentioned components of the laser processing apparatus 1, and causes the laser processing apparatus 1 to perform laser processing operations on the workpiece 200. The control unit 40 is a computer having an arithmetic processing device having a microprocessor such as a CPU (central processing unit), a storage device having a memory such as a ROM (read only memory) or a RAM (random access memory), and an input / output interface device. The arithmetic processing device of the control unit 40 performs arithmetic processing according to a computer program stored in the storage device, and outputs control signals for controlling the laser processing apparatus 1 to the above-mentioned components of the laser processing apparatus 1 via the input / output interface device, thereby realizing the functions of the control unit 40.

[0045] The control unit 40 is connected to a display unit such as a liquid crystal display device that displays the status and images of the machining operation, an input unit used by the operator to register machining content information, and an alarm unit that emits at least one of sound and light to notify the operator. The input unit is composed of at least one of a touch panel provided on the display unit and an external input device such as a keyboard.

[0046] Next, an inspection method according to the first embodiment will be described. Fig. 6 is a flow chart showing the flow of the inspection method according to the first embodiment. The inspection method is a method for inspecting the output state of the laser beam 21 in the laser processing apparatus 1 having the above-mentioned configuration. Note that inspecting the output state of the laser beam 21 means checking the presence or absence of the above-mentioned rise delay and the presence or absence of the leakage light 212.

[0047] The inspection method according to the first embodiment includes a preparation step 101, a positioning step 102, a laser processing step 103, a confirmation step 104, and an adjustment step 105, as shown in FIG.

[0048] (Preparation step) Fig. 7 is an exploded perspective view showing an inspection wafer prepared in the preparation step of the inspection method shown in Fig. 6. Fig. 8 is a cross-sectional view of the inspection wafer prepared in the preparation step of the inspection method shown in Fig. 6. Fig. 9 is a plan view showing an example of a single processing mark formed on the inspection wafer shown in Fig. 7. The preparation step 101 is a step of preparing the inspection wafer 50 shown in Figs. 7 and 8.

[0049] The inspection wafer 50 corresponds to the workpiece 200 to be processed by the laser processing apparatus 1. As shown in Fig. 7 and Fig. 8, the inspection wafer 50 is formed by laminating at least two metal layers 52, 53, a first metal layer 52 and a second metal layer 53 having different specific heats or melting points, on an upper surface 54 of a substrate 51. In the first embodiment, the inspection wafer 50 includes a substrate 51, a first metal layer 52, and a second metal layer 53, and the two metal layers 52, 53 are formed on an upper surface 54 of the substrate 51.

[0050] The substrate 51 is formed in a disk shape with both surfaces 54, 55 being flat and parallel to each other and having a uniform thickness. The substrate 51 is made of a material in which a modified layer is formed by setting a focal point 211 inside and irradiating the laser beam 21, similar to the substrate 201 of the workpiece 200. The substrate 51 is made of the same material as the substrate 201 of the workpiece 200 corresponding to the inspection wafer 50, and has the same thickness as the substrate 201 of the workpiece 200 corresponding to the inspection wafer 50. In the first embodiment, the substrate 51 is made of silicon, sapphire, SiC, or the like, as the substrate 201 of the workpiece 200 corresponding to the inspection wafer 50.

[0051] The first metal layer 52 is formed to a predetermined thickness by deposition on the entire upper surface 54 of the substrate 51. The second metal layer 53 is formed to a predetermined thickness by deposition on the entire upper surface 54 of the first metal layer 52. In the first embodiment, the first metal layer 52 and the second metal layer 53 are laminated on the upper surface 54 of the substrate 51 in order of decreasing specific heat. The second metal layer 53 is formed of a metal having a smaller specific heat than the first metal layer 52. In the present invention, the first metal layer 52 and the second metal layer 53 may be laminated on the upper surface 54 of the substrate 51 in order of increasing melting point.

[0052] The first metal layer 52 and the second metal layer 53 are ablated in an irradiation spot area irradiated with a laser beam 21 having a wavelength that is transparent to the substrate 51 of the workpiece 200 and the substrate 51 of the inspection wafer 50, forming a single processing mark 56 as shown in Figure 9.

[0053] In this way, the first metal layer 52 is made of a material that is melted or thermally deformed by the laser beam 21. In the first embodiment, the first metal layer 52 is made of a metal such as titanium (Ti), chromium (Cr), nickel (Ni), or aluminum (Al). The specific heat of titanium is about 528 J / kg°C, and the specific heat of chromium is about 461 J / kg°C. It is possible to use a metal layer with an even lower specific heat as the first metal layer 52, but in that case, a sufficient thickness is required. In other words, it is preferable that the first metal layer 52 is formed in a configuration that is less susceptible to the influence of the laser beam 21 than the second metal layer 53.

[0054] The second metal layer 53 is made of a material that is completely removed or carbonized by the laser beam 21. In the first embodiment, the second metal layer 53 is made of tin (Sn), platinum (Pt), gold (Au), silver (Ag), indium (In), lead (Pb), or the like. The specific heat of tin is about 226 J / kg°C, the specific heat of platinum is about 134 J / kg°C, the specific heat of gold is about 130 J / kg°C, the specific heat of silver is about 234 J / kg°C, the specific heat of indium is 239 J / kg°C, and the specific heat of lead is about 130 J / kg°C.

[0055] As described above, since the specific heat of the first metal layer 52 is larger than that of the second metal layer 53, when the laser beam 21 is irradiated onto the inspection wafer 50, if the spot shape of the laser beam 21 (the cross-sectional shape in the direction perpendicular to the optical axis at the focal point 211 of the laser beam 21) is circular, a single processing mark 56 is formed in a circular shape as shown in Fig. 9. At the outer edge of the single processing mark 56 (shown by dense parallel hatching in Fig. 9), the second metal layer 53 is removed or carbonized to expose the carbonized second metal layer 53. At the center of the single processing mark 56 (shown by coarse parallel hatching in Fig. 9), the second metal layer 53 is completely removed, and the surface layer of the first metal layer 52 is removed to expose the first metal layer 52.

[0056] Also, in embodiment 1, in the preparation step 101, a circular adhesive tape 208 having a diameter larger than the outer diameter of the inspection wafer 50 is adhered to the underside 55 of the substrate 51 of the inspection wafer 50, and an annular frame 207 having an inner diameter larger than the outer diameter of the inspection wafer 50 is adhered to the outer edge of the adhesive tape 208.

[0057] (Positioning step) Fig. 10 is a side view, partially in cross section, showing a schematic diagram of the positioning step of the inspection method shown in Fig. 6. The positioning step 102 is a step of positioning the condenser 23 for focusing the laser beam 21 at a position facing the inspection wafer 50 after the preparation step 101.

[0058] In the first embodiment, in the positioning step 102, the control unit 40 receives the processing conditions input by the operator by operating the input unit or the like, and the substrate 51 of the inspection wafer 50 is placed on the holding surface 11 of the chuck table 10 positioned in the carry-in / out area via the adhesive tape 208. In the first embodiment, when the control unit 40 receives an instruction from the operator to start the inspection operation from the input unit, it starts the operations of the positioning step 102 and the laser processing step 103.

[0059] The processing conditions include the wavelength, repetition frequency, and output of the laser beam 21, the position of the focal point 211 in the Z-axis direction, the moving speed of the chuck table 10 in the X-axis direction when the laser beam 21 is irradiated (hereinafter referred to as the processing feed speed), and the output of the RF signal. In the first embodiment, the wavelength of the laser beam 21 is 1342 nm, and the repetition frequency of the laser beam 21 is 90 kHz. The output of the laser beam 21 is set to 0.05 W increments between 0.2 W and 0.5 W (specifically, 0.2 W, 0.25 W, 0.3 W, 0.35 W, 0.4 W, 0.45 W, and 0.5 W). In the first embodiment, the output of the laser beam 21 has a predetermined value of 0.2 W, a second predetermined value of 0.25 W, a third predetermined value of 0.3 W, a fourth predetermined value of 0.35 W, and a fifth predetermined value of 0.4 W.

[0060] In the inspection method of embodiment 1, the laser processing apparatus 1 forms a plurality of single processing marks 56 (hereinafter, when distinguishing between the single processing marks 56, it will be indicated by the reference symbol 56-1) formed by irradiating the inspection wafer 50 with a laser beam 21 of a predetermined value, a single processing mark 56 formed by irradiating the wafer 50 with a laser beam 21 of a second predetermined value (hereinafter, when distinguishing between the single processing marks 56, it will be indicated by the reference symbol 56-2), a single processing mark 56 formed by irradiating the wafer 50 with a laser beam 21 of a third predetermined value (hereinafter, when distinguishing between the single processing marks 56, it will be indicated by the reference symbol 56-3), a single processing mark 56 formed by irradiating the wafer 50 with a laser beam 21 of a fourth predetermined value (hereinafter, when distinguishing between the single processing marks 56, it will be indicated by the reference symbol 56-4), and a single processing mark 56 formed by irradiating the wafer 50 with a laser beam 21 of a fifth predetermined value (hereinafter, when distinguishing between the single processing marks 56, it will be indicated by the reference symbol 56-5).

[0061] In the positioning step 102, the control unit 40 suction-holds the inspection wafer 50 on the holding surface 11 of the chuck table 10 via the adhesive tape 208, and clamps the frame 207 with the clamp section 12. In the positioning step 102, the control unit 40 controls the moving unit 30 to move the chuck table 10, which holds the inspection wafer 50 by suction, from the carry-in / out area toward the processing area, and positions the inspection wafer 50 held by suction on the chuck table 10 below the imaging unit.

[0062] In the positioning step 102, the control unit 40 uses the imaging unit to capture an image of the inspection wafer 50 held by suction on the holding surface 11 of the chuck table 10, performs alignment, and positions the inspection wafer 50 below the condenser lens 231 of the collector 23 of the laser beam irradiation unit 20, as shown in Fig. 10. In the first embodiment, in the positioning step 102, the laser processing apparatus 1 positions the laser beam irradiation unit 20 above the center in the Y-axis direction of the inspection wafer 50 held by suction on the holding surface 11 of the chuck table 10 and above one end in the X-axis direction.

[0063] (Laser processing step) Fig. 11 is a side view, partially in cross section, showing a schematic diagram of the laser processing step of the inspection method shown in Fig. 6. Fig. 12 is a plan view showing a schematic diagram of an inspection wafer on which processing marks are formed after the laser processing step of the inspection method shown in Fig. 6.

[0064] The laser processing step 103 is a step in which, after the positioning step 102, irradiation of the laser beam 21 is started and the inspection wafer 50 and the focal point 211 of the laser beam 21 are moved relatively to each other, thereby forming a continuous processing mark 57 (shown in FIG. 7) of a predetermined length on the inspection wafer 50. The laser processing step 103 is also a step in which, after the preparation step 101, the inspection wafer 50 and the focal point 211 of the laser beam 21 are moved relatively to each other while irradiating the laser beam 21, and irradiation of the laser beam 21 on the inspection wafer 50 is stopped, thereby forming a continuous processing mark 57 of a predetermined length on the inspection wafer 50. The processing mark 57 is composed of a plurality of single processing marks 56.

[0065] In the embodiment 1, in the laser processing step 103, the control unit 40 sets the focal point 211 on the surface of the inspection wafer 50 sucked and held on the chuck table 10 based on the processing conditions. In the embodiment 1, in the laser processing step 103, the control unit 40 controls the laser beam application unit 20 and the moving unit 30 based on the processing conditions to start irradiating the pulsed laser beam 21 from the laser beam application unit 20 toward the inspection wafer 50.

[0066] In the first embodiment, in the laser processing step 103, the control unit 40 controls the laser beam application unit 20 and the moving unit 30 based on the processing conditions to move the chuck table 15 in the X-axis direction and move the laser beam application unit 20 relative to the chuck table 10 from the position shown by the dotted line in Fig. 11 to the position shown by the solid line in Fig. 11, while irradiating the inspection wafer 50 with a pulsed laser beam 21 from the laser beam application unit 20 from the side where the metal layers 52, 53 are laminated. Thus, in the first embodiment, the laser beam 21 is irradiated from the side of the inspection wafer 50 where the metal layers 52, 53 are laminated.

[0067] In embodiment 1, in the laser processing step 103, the control unit 40 controls the laser beam irradiation unit 20 and the moving unit 30 based on the processing conditions to stop the irradiation of the laser beam from the laser beam irradiation unit 20 on the inspection wafer 50.

[0068] In the first embodiment, in the laser processing step 103, the laser beam 21 ablates the metal layers 52, 53 of the inspection wafer 50, so that the laser processing apparatus 1 forms a processing mark 57 that is made up of a plurality of single processing marks 56 and that is continuous over a predetermined length on the metal layers 52, 53 of the inspection wafer 50, as shown in Fig. 12. In this specification, "continuous processing marks 57" means that the single processing marks 56 are formed side by side on the same line, and adjacent single processing marks 56 may overlap or may be spaced apart.

[0069] In the first embodiment, in the laser processing step 103, the control unit 40 controls the laser beam irradiating unit 20 and the moving unit 30 to start irradiating the inspection wafer 50 with the laser beam 21 having a predetermined output power from the laser beam irradiating unit 20, irradiates the inspection wafer 50 with the pulsed laser beam 21 while relatively moving the laser beam irradiating unit 20 and the chuck table 10 in the X-axis direction, and stops irradiating the inspection wafer 50 with the laser beam 21 from the laser beam irradiating unit 20. In the first embodiment, in the laser processing step 103, by irradiating the inspection wafer 50 with the laser beam 21 having a predetermined output power, processing marks 57 consisting of a plurality of single processing marks 56-1 (hereinafter, when the processing marks 57 are to be distinguished from one another, they are indicated by the reference symbol 57-1) are formed.

[0070] In embodiment 1, in the laser processing step 103, after forming the processing mark 57-1 on the inspection wafer 50, the control unit 40 controls the moving unit 30 to move the chuck table 10 in the Y-axis direction and the X-axis direction, and when forming the processing mark 57-1 on the inspection wafer 50, the laser beam irradiation unit 20 is positioned above a position spaced a predetermined distance in the Y-axis direction from the position where the irradiation of the laser beam 21 began.

[0071] In the first embodiment, in the laser processing step 103, the control unit 40 controls the laser beam irradiating unit 20 and the moving unit 30 to start irradiating the inspection wafer 50 with the laser beam 21 having an output of a second predetermined value from the laser beam irradiating unit 20, irradiates the inspection wafer 50 with the pulsed laser beam 21 while relatively moving the laser beam irradiating unit 20 and the chuck table 10 in the X-axis direction, and stops irradiating the inspection wafer 50 with the laser beam 21 from the laser beam irradiating unit 20. In the first embodiment, in the laser processing step 103, by irradiating the laser beam 21 having an output of the second predetermined value, a processed mark 57 consisting of a plurality of single processed marks 56-2 is formed on the inspection wafer 50 (hereinafter, the processed marks 57 are indicated by the reference symbol 57-2 when distinguishing between each other).

[0072] Thus, in embodiment 1, in the laser processing step 103, the laser processing apparatus 1 repeats the operation of starting to irradiate the inspection wafer 50 with a pulsed laser beam 21 and moving the laser beam irradiation unit 20 and the chuck table 10 relatively in the X-axis direction, and then stopping irradiation of the laser beam 21 and moving the chuck table 10 in the Y-axis and X-axis directions to position the laser beam irradiation unit 20 above the inspection wafer 50, by switching the output of the laser beam 21 between a predetermined value, a second predetermined value, a third predetermined value, a fourth predetermined value, and a fifth predetermined value in that order. In embodiment 1, in the laser processing step 103, the laser processing apparatus 1 forms, on the metal layer 52, 53 side of the inspection wafer 50, processing marks 57-1, processing marks 57-2, processing marks 57 consisting of multiple single processing marks 56-3 (hereinafter, when distinguishing between the processing marks 57, it will be indicated by the reference symbol 57-3), processing marks 57 consisting of multiple single processing marks 56-4 (hereinafter, when distinguishing between the processing marks 57, it will be indicated by the reference symbol 57-4), and processing marks 57 consisting of multiple single processing marks 56-5 (hereinafter, when distinguishing between the processing marks 57, it will be indicated by the reference symbol 57-5).

[0073] In the first embodiment, in the laser processing step 103, the laser processing device 1 forms a plurality of processing marks 57-1, 57-2, 57-3, 57-4, 57-5 in parallel as shown in Fig. 12. The processing marks 57-1, 57-2, 57-3, 57-4, 57-5 shown in Fig. 12 are formed when the laser beam 21 starts irradiating at the left end of the figure, and the single processing marks 56-1, 56-2, 56-3, 56-4, 56-5 are started to be formed. The processing marks 57-1, 57-2, 57-3, 57-4, 57-5 shown in Fig. 12 are formed when the laser beam 21 stops irradiating at the right end of the figure, and the single processing marks 56-1, 56-2, 56-3, 56-4, 56-5 are stopped to be formed.

[0074] In embodiment 1, in laser processing step 103, when the laser processing apparatus 1 forms processing marks 57-1, 57-2, 57-3, 57-4, and 57-5 on the metal layer 52, 53 side of the inspection wafer 50, it controls the moving unit 30 to position the chuck table 10 in the loading / unloading area, stops the suction holding of the inspection wafer 50 on the holding surface 11 of the chuck table 10, and releases the clamping of the frame 207 of the clamp section 12.

[0075] (Confirmation step) Fig. 13 is a plan view showing a schematic enlargement of part XIII in Fig. 12 to show the processing marks. Fig. 14 is a plan view showing a schematic enlargement of part XIV in Fig. 12 to show the processing marks.

[0076] The confirmation step 104 is a step for confirming whether the processing mark 57 has changed in the processing proceeding direction immediately after the start of irradiation of the laser beam 21. The confirmation step 104 is also a step for confirming whether or not an indentation 58 of the laser beam 21 has been formed on the inspection wafer 50 beyond the irradiation stop position of the laser beam 21 after the laser processing step 103. The indentation 58 is formed mainly by ablation processing of the surface of the second metal layer 53 due to irradiation with the leakage light 212 of the laser beam 21.

[0077] In the confirmation step 104, the operator or the like observes the single processed marks 56-1, 56-2, 56-3, 56-4, and 56-5 shown in Fig. 13, including the processed marks 57-1, 57-2, 57-3, 57-4, and 57-5 immediately after the start of irradiation of the laser beam 21. In the confirmation step 104, the operator or the like checks whether the single processed marks 56-1, 56-2, 56-3, 56-4, and 56-5 of the processed marks 57-1, 57-2, 57-3, 57-4, and 57-5 expose the carbonized second metal layer 531 at the outer edge and expose the first metal layer 52 at the center, and checks whether the processed marks 57-1, 57-2, 57-3, 57-4, and 57-5 have changed in the processing progress direction since the start of irradiation of the laser beam 21.

[0078] In embodiment 1, in confirmation step 104, for example, if the outer diameter of the exposed first metal layer 52 of the single processing marks 56-1, 56-2, 56-3, 56-4, and 56-5 is 90% or more of the outer diameter of the single processing marks 56-1, 56-2, 56-3, 56-4, and 56-5, it is determined that the carbonized second metal layer 531 is exposed at the outer edge and the first metal layer 52 is exposed at the center.

[0079] In the first embodiment, in the confirmation step 104, an operator or the like determines that a delay in the rise of the laser beam 21 has occurred when the single processing mark 56 of the processing mark 57 changes in the X-axis direction, which is the processing progress direction, from immediately after the start of irradiation. For example, as shown in Fig. 13, if the single processing mark 56-2 of the processing mark 57-2 does not expose the first metal layer 52 at the center immediately after the start of irradiation, but exposes the first metal layer 52 at the center over time, it is determined that a delay in the rise of the laser beam 21 has occurred when the laser beam 21 with the output of the second predetermined value is irradiated.

[0080] Also, in confirmation step 104, the operator etc. observes an area, for example, as shown in Figure 14, which includes the processing marks 57-1, 57-2, 57-3, 57-4, 57-5 at the irradiation stop position of the laser beam 21 and includes the surface of the second metal layer 53 further in the processing progress direction than the single processing marks 56-1, 56-2, 56-3, 56-4, 56-5 at the irradiation stop position.

[0081] In the confirmation step 104, the operator or the like confirms whether or not the dent 58 is formed on the surface of the second metal layer 53 further in the processing direction than the single processing marks 56-1, 56-2, 56-3, 56-4, 56-5 at all irradiation stop positions of all processing marks 57-1, 57-2, 57-3, 57-4, 57-5, that is, whether or not the dent 58 of the laser beam 21 is formed beyond the irradiation stop position. In the first embodiment, in the confirmation step 104, if it is determined that the dent 58 is not formed on the surface of the second metal layer 53 further in the processing direction than the single processing marks 56-1, 56-2, 56-3, 56-4, 56-5 at all irradiation stop positions of all processing marks 57-1, 57-2, 57-3, 57-4, 57-5, it is determined that there is no leakage light 212.

[0082] On the other hand, in the first embodiment, in the confirmation step 104, if it is determined that the dent 58 is formed on the surface of the second metal layer 53 further in the processing progress direction than the irradiation stop position, it is determined that there is leakage light 212 when forming the single processing mark 56 of the processing mark 57 in which the dent 58 is formed. For example, as shown in Fig. 14, if the dent 58 is formed on the surface of the second metal layer 53 further in the processing progress direction than the single processing mark 56-4 at the irradiation stop position of the processing mark 57-4, it is determined that there is leakage light 212 of the laser beam 21 when the laser beam 21 with the output of the fourth predetermined value is irradiated.

[0083] (Adjustment steps) The adjustment step 105 is a step of adjusting the output of an RF signal, which is an output of an RF driver 244 that controls the start and stop of irradiation of the laser beam, so that the changes in the processing marks 57-1, 57-2, 57-3, 57-4, and 57-5 disappear if the processing marks 57-1, 57-2, 57-3, 57-4, and 57-5 have changed in the X-axis direction immediately after the start of irradiation of the laser beam 21 in the confirmation step 104. The adjustment step 105 is also a step of adjusting the output of an RF signal of the RF driver 244 so that the laser beam dent 58 does not form beyond the irradiation stop position if the dent 58 of the laser beam 21 has been formed on the inspection wafer 50 beyond the irradiation stop position of the laser beam 21 in the confirmation step 104.

[0084] In the first embodiment, in the adjustment step 105, if it is determined in the confirmation step 104 that a delay in the rising edge of the laser beam 21 occurs when the laser beam 21 having the output of the second predetermined value is irradiated as shown in Fig. 13, the output of the RF signal of the RF driver 244 is adjusted so that the change in the processing mark 57 disappears, that is, the delay in the rising edge of the laser beam 21 is reduced. Also, in the adjustment step 105, if it is determined in the confirmation step 104 that there is leakage light 212 of the laser beam 21 when the laser beam 21 having the output of the fourth predetermined value is irradiated as shown in Fig. 14, the output of the RF signal of the RF driver 244 is adjusted so that the laser beam dent 58 is not formed beyond the irradiation stop position.

[0085] The inspection method according to the first embodiment ends after it is determined in the confirmation step 104 that there is no delay in the rising edge of the laser beam and no leakage light 212, or after adjusting the output of the RF signal of the RF driver 244 in the adjustment step 105. Note that in the present invention, the inspection method may check for the presence or absence of a delay in the rising edge of the laser beam 21 and the presence or absence of the leakage light 212 by sequentially performing the preparation step 101, the positioning step 102, the laser processing step 103, and the confirmation step 104 again after adjusting the output of the RF signal of the RF driver 244 in the adjustment step 105.

[0086] As described above, the inspection method according to the first embodiment irradiates the metal layers 52, 53 of the inspection wafer 50 held on the chuck table 10 with the laser beam 21. Therefore, by checking the processing marks 57-1, 57-2, 57-3, 57-4, 57-5 formed on the inspection wafer 50, it is possible to check whether there is a delay in the rise of the laser beam 21 and whether there is leakage light 212 when switching between starting and stopping the irradiation of the laser beam 21.

[0087] Therefore, the inspection method according to the first embodiment eliminates the need to install a photodetector, thereby reducing the amount of labor required, and has the advantage of making it possible to easily check whether there is a delay in the rise of the laser beam 21 and whether there is leakage light 212.

[0088] In addition, the inspection method according to embodiment 1 checks whether the processing marks 57-1, 57-2, 57-3, 57-4, and 57-5 have changed in the X-axis direction immediately after the start of irradiation of the laser beam 21, so that it is easy to check whether there is a delay in the rise of the laser beam 21.

[0089] Furthermore, in the laser processing apparatus 1 of embodiment 1, if it is found in the confirmation step 104 that the processing marks 57-1, 57-2, 57-3, 57-4, and 57-5 have changed in the X-axis direction immediately after the start of irradiation of the laser beam 21, then in the adjustment step 105, the output of the RF signal from the RF driver 244 is adjusted so that the changes in the processing marks 57-1, 57-2, 57-3, 57-4, and 57-5 are reduced, thereby suppressing the rise delay of the laser beam 21.

[0090] Furthermore, in the inspection method according to embodiment 1, in confirmation step 104, it is confirmed whether or not a dent 58 has been formed beyond the irradiation stop position, so that it is possible to easily confirm whether or not there is leakage light 212 of laser beam 21.

[0091] Furthermore, in the inspection method according to the first embodiment, if a dent 58 is formed beyond the irradiation stop position, in the adjustment step 105, the output of the RF signal from the RF driver 244 is adjusted so that the dent 58 is no longer formed, thereby making it possible to suppress the leakage light 212 of the laser beam 21.

[0092] It should be noted that the present invention is not limited to the above-described embodiment, and can be practiced in various modified forms without departing from the gist of the present invention. [Explanation of symbols]

[0093] 1 Laser processing equipment 21 Laser Beam 23 Concentrator 50 Test wafer 51 Substrate 52 First metal layer (metal layer) 53 Second metal layer (metal layer) 54 Top 57,57-1,57-2,57-3,57-4,57-5 Machining marks 58 Dent 101 Preparation Steps 102 Positioning Step 103 Laser Processing Steps 104 Confirmation Step 105 Adjustment Steps 200 Workpiece 211 Focus point 244 RF Driver

Claims

1. A method for inspecting an output state of a laser beam in a laser processing device that performs discontinuous processing on a workpiece by repeatedly starting and stopping irradiation of a laser beam, comprising the steps of: A preparation step of preparing a wafer for inspection; After the preparation step, a positioning step of positioning a collector that focuses the laser beam at a position facing the wafer to be inspected; After the positioning step, a laser processing step of starting irradiation of the laser beam and relatively moving the inspection wafer and a focal point of the laser beam to form a continuous processing mark of a predetermined length on the inspection wafer; a confirmation step of confirming whether the processing mark has changed in the processing progress direction immediately after the start of the laser beam irradiation; 13. A method for inspecting an output state of a laser beam, comprising:

2. In the confirmation step, if the processing mark has changed in the processing progress direction immediately after the start of the irradiation of the laser beam, an adjustment step is further included in which an output of an RF driver that controls the start and end of the irradiation of the laser beam is adjusted so that the change in the processing mark disappears.

2. A method for inspecting an output state of a laser beam according to claim 1.

3. A method for inspecting an output state of a laser beam in a laser processing device that performs discontinuous processing on a workpiece by repeatedly starting and stopping irradiation of a laser beam, comprising the steps of: A preparation step of preparing a wafer for inspection; After the preparation step, a laser processing step of relatively moving the inspection wafer and a focal point of the laser beam while irradiating the inspection wafer with the laser beam and stopping the irradiation of the laser beam on the inspection wafer, thereby forming a continuous processing mark of a predetermined length on the inspection wafer; After the laser processing step, a confirmation step of confirming whether or not a mark of the laser beam is formed on the inspection wafer beyond a position where the laser beam stops in a processing direction of the laser beam; 13. A method for inspecting an output state of a laser beam, comprising:

4. If a dent of the laser beam is formed on the inspection wafer beyond the irradiation stop position of the laser beam in the confirmation step, the method further includes an adjustment step of adjusting an output of an RF driver that controls the start and end of irradiation of the laser beam so that a dent of the laser beam is not formed beyond the irradiation stop position.

4. A method for inspecting an output state of a laser beam according to claim 3.

5. The inspection wafer comprises: At least two metal layers, a first metal layer and a second metal layer, having different specific heats or melting points, are laminated on the upper surface of a substrate; The laser beam is 5. The method for inspecting the output state of a laser beam according to claim 1, wherein the laser beam is irradiated from the side where the metal layer is laminated.

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