Laser beam irradiation device and laser beam irradiation method

Abstract

To easily set a focus of laser light.SOLUTION: A laser light irradiation apparatus 1 comprises: a laser light irradiation unit 20 which irradiates a wafer 200 with laser light 21; a first movement unit which moves a holding table 10; a second movement unit 50 which changes a distance between the laser light irradiation unit 20 and the wafer 200; a light reception unit 70 which receives plasma light 21-1; and a control unit 100. The control unit 100 comprises: a commanding part which issues a command for irradiating the wafer 200 with the laser light 21 by moving the holding table 10 while changing the distance; an information acquisition part which acquires the light intensity of the plasma light 21-1 received by the light reception unit 70; a recording part which records the distance and the light intensity in association with each other; and a focus detection part which detects the distance at which the focus 27 of the laser light 21 is brought to the front surface 202 of the wafer 200 according to the light intensity recorded in the recording part.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a laser beam application device and a laser beam application method that perform a focus detection step of detecting the positional relationship between a laser beam application unit, which focuses a laser beam on an irradiation surface of a wafer that is irradiated with the laser beam, and the wafer. [Background technology]

[0002] Conventionally, to set the focus of a laser beam, a laser beam is irradiated onto the wafer to form a groove while the distance between the wafer and the laser beam irradiation unit is changed relatively, and the point at which the groove is narrowest is detected as the state in which the focus of the laser beam is on the surface of the wafer (see, for example, Patent Documents 1, 2 and 3). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-118808 [Patent Document 2] Patent No. 6110136 [Patent Document 3] Patent No. 6600254 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the conventional method of setting the focus of the laser beam, it is necessary to take an image of the formed groove and detect the narrow groove, which is time-consuming.

[0005] An object of the present invention is to provide a laser beam application device and a laser beam application method that can easily set the focus of a laser beam. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems and achieve the object, the laser beam irradiation device of the present invention comprises: a holding table that holds, on a holding surface, a wafer having a device region on the surface of which devices are formed and a peripheral excess region surrounding the device region and in which no devices are formed; The laser beam irradiation device includes a laser beam irradiation unit that irradiates a wafer held on a holding surface of a holding table with a laser beam, a first moving unit that relatively moves the holding table and the laser beam irradiation unit in a direction parallel to the holding surface, a second moving unit that changes the distance between the laser beam irradiation unit and the wafer, a light receiving unit that receives plasma light or reflected light generated by irradiating the wafer with the laser beam, and a control unit, and the control unit relatively moves the holding table and the laser beam irradiation unit with the first moving unit while changing the distance. The peripheral excess area an information acquiring unit that acquires information about the light intensity of the plasma light or the reflected light received by the light receiving unit; a recording unit that records information about the distance at the time of irradiating the laser beam and information about the light intensity acquired by the information acquiring unit in association with each other; and a focus detecting unit that detects information about the distance when the focus of the laser beam is aligned with the surface of the wafer that is irradiated with the laser beam, according to the information about the light intensity recorded in the recording unit. controlling the second moving unit to set the distance between the laser beam application unit and the wafer to the distance detected by the focus detection unit, and controlling the first moving unit to relatively move the holding table and the laser beam application unit while irradiating the wafer with the laser beam along the planned dividing line of the device region. It is characterized by:

[0007] In the laser beam irradiation device, the light receiving unit may receive plasma light generated by irradiating the wafer with the laser beam, and the focus detection unit may detect, in the recording unit, the distance at which the light intensity of the plasma light is at its maximum as a state in which the focus of the laser beam is aligned with the surface of the wafer that is irradiated with the laser beam.

[0008] The present invention Laser beam irradiation device The laser beam irradiation device includes a laser beam irradiation unit that irradiates a laser beam onto a wafer held on a holding surface of a holding table, a first moving unit that relatively moves the holding table and the laser beam irradiation unit in a direction parallel to the holding surface, a second moving unit that changes the distance between the laser beam irradiation unit and the wafer, a light receiving unit that receives plasma light or reflected light generated by the irradiation of the laser beam onto the wafer, and a control unit, and the control unit controls the first moving unit to move the holding table while changing the distance. a command section that issues a command to move the cable and the laser beam application unit relatively to irradiate the wafer with the laser beam; an information acquisition section that acquires information about the light intensity of the plasma light or the reflected light received by the light receiving unit; a recording section that records information about the distance at the time of irradiating the laser beam and information about the light intensity acquired by the information acquisition section in association with each other; and a focus detection section that detects information about the distance when the focus of the laser beam is aligned with the surface of the wafer that is irradiated with the laser beam, according to the information about the light intensity recorded in the recording section. The light receiving unit detects reflected light generated by irradiating the wafer with the laser beam, and the focus detection unit detects the distance at the time when the light intensity of the reflected light is minimum in the recording unit as a state in which the focus of the laser beam is aligned with the surface of the wafer that is irradiated with the laser beam. It is characterized by .

[0009] The laser beam irradiation method of the present invention is a laser beam irradiation method, A device region in which a device is formed on the surface and a peripheral excess region in which no device is formed and which surrounds the device region are formed. a holding step for holding a wafer on a holding surface of a holding table; a laser beam irradiation unit for relatively moving the holding table and the laser beam irradiation unit in a direction parallel to the holding surface while relatively changing the distance between the wafer and the laser beam irradiation unit along the optical axis of the laser beam; The outer surplus area of a laser beam irradiating step of irradiating a laser beam onto the wafer; a light receiving step of receiving, with a light receiving unit, plasma light or reflected light generated by irradiating the wafer with the laser beam; and determining whether the focus of the laser beam is aligned with the surface of the wafer that is irradiated with the laser beam based on information about the light intensity of the received plasma light or reflected light. Distance a focus detection step of detecting information about the distance; The distance between the laser beam application unit and the wafer is set to the appropriate distance, and the laser beam is applied along the division line of the device region of the wafer while the holding table and the laser beam application unit are moved relative to each other. It is characterized by:

[0010] In the laser beam irradiation method, the light receiving unit may receive plasma light generated by irradiating the wafer with the laser beam, and the focus detection step may detect the distance at which the light intensity of the plasma light is at its maximum as a state in which the focus of the laser beam is aligned with the surface of the wafer that is irradiated with the laser beam.

[0011] The present invention Laser beam irradiation method teeth , A laser beam application method comprising: a holding step of holding a wafer on a holding surface of a holding table; a laser beam application step of irradiating a laser beam onto the wafer held in the holding step by relatively moving the holding table and the laser beam application unit in a direction parallel to the holding surface while relatively changing the distance between the wafer and the laser beam application unit along the optical axis of the laser beam; a light receiving step of receiving, with a light receiving unit, plasma light or reflected light generated by irradiating the wafer with the laser beam; and a focus detection step of detecting, based on information on the light intensity of the received plasma light or reflected light, information on the distance at which the focus of the laser beam is aligned with the surface of the wafer that is irradiated with the laser beam, The light receiving unit detects reflected light generated by irradiating the wafer with the laser beam, and the focus detecting step detects the distance at which the light intensity of the reflected light is minimum as a state in which the focus of the laser beam is aligned with the surface of the wafer that is irradiated with the laser beam. It is characterized by . [Effects of the Invention]

[0012] The present invention has an effect of making it possible to easily set the focus of a laser beam. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a perspective view showing an example of the configuration of a laser beam application device according to the first embodiment. [Figure 2] FIG. 2 is a plan view schematically showing a wafer to be processed by the laser beam application apparatus shown in FIG. [Figure 3] FIG. 3 is a diagram schematically showing the configuration of a laser beam application unit and a light receiving unit of the laser beam application device shown in FIG. [Figure 4] FIG. 4 is a plan view of a wafer, which diagrammatically shows the position where the command unit of the laser beam application device shown in FIG. 1 commands the application of a laser beam. [Figure 5] FIG. 5 is a diagram schematically showing data recorded by the recording unit of the laser beam application device shown in FIG. [Figure 6] FIG. 6 is a flowchart showing the flow of the laser beam application method according to the first embodiment. [Figure 7] FIG. 7 is a perspective view showing an example of the configuration of a laser beam application device according to the second embodiment. [Figure 8] FIG. 8 is a diagram schematically showing the configuration of the laser beam application unit and the light receiving unit of the laser beam application device shown in FIG. [Figure 9] FIG. 9 is a diagram schematically showing data recorded by a recording unit of the laser beam application device according to the second embodiment. [Figure 10] FIG. 10 is a side view, partly in section, schematically illustrating an example of the configuration of the laser beam application device according to the first and second embodiments. [Figure 11] FIG. 11 is a diagram schematically showing the configuration of the laser beam application unit and the light receiving unit of the laser beam application device shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0014] Modes (embodiments) 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 embodiments. Furthermore, the components described below include those that can be easily imagined by a person skilled in the art and those that are substantially the same. Furthermore, the configurations described below can be combined as appropriate. Furthermore, various omissions, substitutions, or modifications of the configuration can be made within the scope of the gist of the present invention.

[0015] [Embodiment 1] A laser beam application device according to a first embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a perspective view showing an example of the configuration of the laser beam application device according to the first embodiment. Fig. 2 is a plan view schematically showing a wafer to be processed by the laser beam application device shown in Fig. 1. Fig. 3 is a view schematically showing the configuration of a laser beam application unit and a light receiving unit of the laser beam application device shown in Fig. 1.

[0016] (wafer) 1 according to the first embodiment is a processing device that irradiates a wafer 200 with a laser beam 21. The wafer 200 to be processed by the laser beam application device 1 according to the first embodiment is a wafer such as a disk-shaped semiconductor wafer or an optical device wafer, which has a substrate 201 made of silicon, sapphire, gallium, or the like. As shown in FIG. 2, the wafer 200 has a device region 203 and a peripheral excess region 204 surrounding the device region 203 formed on a surface 202 (corresponding to the surface irradiated with the laser beam 21).

[0017] 1, a plurality of mutually intersecting planned division lines 205 are set in the device region 203, and devices 206 are formed in regions partitioned by the planned division lines 205. The devices 206 are, for example, integrated circuits such as ICs (Integrated Circuits) or LSIs (Large Scale Integrations), image sensors such as CCDs (Charge Coupled Devices) or CMOSs ​​(Complementary Metal Oxide Semiconductors), or memories (semiconductor memory devices).

[0018] The peripheral surplus region 204 surrounds the device region 203 all around. No devices 206 are formed in the peripheral surplus region 204. The wafer 200 has a notch 207, an irregularly shaped portion indicating crystal orientation, formed on its outer edge. Note that FIG. 2 omits the devices 206 in the device region 203, and indicates the boundary 208 between the device region 203 and the peripheral surplus region 204 with a dashed line. Note that while FIG. 2 indicates the boundary 208 between the device region 203 and the peripheral surplus region 204 with a dashed line, no boundary between the device region 203 and the peripheral surplus region 204 is formed on the surface 202 of the wafer 200.

[0019] 1, the wafer 200 has a disk shape with a diameter larger than the outer diameter of the wafer 200, and an annular frame 210 attached to its outer edge. An adhesive tape 211 is attached to a back surface 209 behind the front surface 202 of the wafer 200, and the wafer 200 is supported within an opening in the annular frame 210. The wafer 200 is divided into individual devices 206 by, for example, irradiating a laser beam 21 along division lines 205.

[0020] 1 is a processing device that performs ablation processing on the wafer 200 by setting a focal point 27 of a pulsed laser beam 21, the focal point 27 having a wavelength that is absorbed by a substrate 201 constituting the wafer 200, on the surface 202 of the wafer 200, and irradiating the surface 202 with the laser beam 21 along a planned dividing line 205. As shown in FIG. 1, the laser beam application device 1 has a holding table 10 that holds the wafer 200, a laser beam application unit 20, a first moving unit 30, an imaging unit 40, and a control unit 100.

[0021] The holding table 10 holds the wafer 200 on a holding surface 11 that is parallel to the horizontal direction. The holding surface 11 is disk-shaped and made of porous ceramic or the like, and is connected to a vacuum suction source (not shown) via a suction path (not shown). The holding table 10 is sucked by the vacuum suction source to suction-hold the wafer 200 placed on the holding surface 11. A plurality of clamps (not shown) are arranged around the holding table 10 to clamp an annular frame 210 that supports the wafer 200 in an opening.

[0022] Furthermore, the holding table 10 is rotated by the rotational movement unit 33 of the first moving unit 30 about an axis that is perpendicular to the holding surface 11 and parallel to the Z-axis direction that is parallel to the vertical direction. The holding table 10, together with the rotational movement unit 33, is moved by the X-axis movement unit 31 of the first moving unit 30 in the X-axis direction (corresponding to the processing proceeding direction) that is parallel to the horizontal direction, and is moved by the Y-axis movement unit 32 in the Y-axis direction that is parallel to the horizontal direction and perpendicular to the X-axis direction. The holding table 10 is moved by the first moving unit 30 between a processing region below the laser beam application unit 20 and a carry-in / out region that is away from below the laser beam application unit 20 and where the wafer 200 is carried in and out.

[0023] The laser beam application unit 20 is a laser beam application means that focuses and applies a pulsed laser beam 21 to the wafer 200 held on the holding surface 11 of the holding table 10. In the first embodiment, a part of the laser beam application unit 20 is disposed at the tip of a support column 4, the base end of which is supported by an erected wall 3 erected from the apparatus main body 2, as shown in FIG.

[0024] The laser beam application unit 20 irradiates a laser beam 21 having a wavelength that is absorbable by the substrate 201 of the wafer 200 held on the holding table 10. As shown in Fig. 2, the laser beam application unit 20 includes an oscillator 22 that emits a pulsed laser beam 21, and a condenser lens 23 that condenses the laser beam 21 emitted from the oscillator 22 and irradiates the wafer 200 with the laser beam 21. In addition, in the first embodiment, the laser beam application unit 20 includes a mirror 24 that reflects the laser beam 21 emitted from the oscillator 22 toward the condenser lens 23.

[0025] The oscillator 22 includes a laser medium (not shown) that oscillates and amplifies the laser beam 21. In addition, the repetition frequency of the emitted laser beam 21 in the oscillator 22 is set by a repetition frequency setting unit 25. In the oscillator 22, the output of the emitted laser beam 21 is adjusted by an output adjustment unit 26. In the first embodiment, the output adjustment unit 26 is disposed between the oscillator 22 and the mirror.

[0026] The condenser lens 23 is disposed at a position facing the holding surface 11 of the holding table 10 in the Z-axis direction, which is parallel to the vertical direction. The condenser lens 23 is a focusing optical element that focuses and irradiates the pulsed laser beam 21 onto the wafer 200 held on the holding table 10. The condenser lens 23 transmits the laser beam 21 that is emitted from the oscillator 22 and reflected by the mirror 24, and focuses the laser beam 21 at a focal point 27. In the first embodiment, the condenser lens 23 focuses the focal point 27 of the laser beam 21 on the surface 202 of the wafer 200 held on the holding surface 11 of the holding table 10.

[0027] Furthermore, the distance between the condenser lens 23 and the wafer 200 held on the holding table 10 is changed relatively along the optical axis of the laser beam 21 by the second moving unit 50. That is, the laser beam application device 1 includes the second moving unit 50 that changes the distance between the condenser lens 23 of the laser beam application unit 20 and the wafer 200 held on the holding table 10 relatively along the optical axis of the laser beam 21.

[0028] In embodiment 1, the second moving unit 50 moves the focusing lens 23 along the optical axis of the laser beam 21 parallel to the Z-axis direction, thereby relatively changing the distance between the focusing lens 23 and the wafer 200 held on the holding table 10 along the optical axis of the laser beam 21. In embodiment 1, the second moving unit 50 includes a well-known ball screw 51 that is rotatable around its axis and parallel to the Z-axis direction, a well-known pulse motor 52 that rotates the ball screw 51 around its axis, and a well-known guide rail 53 that supports the lens holder 28 holding the focusing lens 23 so that it can be moved in the Z-axis direction.

[0029] The laser beam application unit 20 irradiates the wafer 200 held on the holding table 10 with a laser beam 21 having a wavelength that is absorbed by the substrate 201 of the wafer 200, thereby performing ablation processing on the wafer 200. Since the laser beam 21 has a wavelength that is absorbed by the substrate 201 of the wafer 200, when the laser beam 21 is irradiated onto the wafer 200, it is absorbed by the substrate 201, raising the temperature of the substrate 201 and changing the substrate 201 from a solid to a gas, ionizing electrons and the like from atoms of the gas molecules, and generating a gas containing charged particles produced by the ionization, i.e., plasma light 21-1. The light intensity of the plasma light 21-1 generated by the laser beam 21 is strongest when the focus 27 of the laser beam 21 is located on the surface 202 of the substrate 201 because the laser beam 21 has a wavelength that is absorbed by the substrate 201 of the wafer 200, and gradually weakens as the distance in the Z-axis direction of the focus 27 from the surface 202 of the substrate 201 increases.

[0030] The first moving unit 30 relatively moves the holding table 10 and the focal point 27 of the laser beam 21 emitted by the laser beam application unit 20 around axes parallel to the X-axis direction, the Y-axis direction, and 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 first moving unit 30 includes an X-axis moving unit 31, which is a processing feed unit that moves the holding table 10 in the X-axis direction, a Y-axis moving unit 32, which is an indexing feed unit that moves the holding table 10 in the Y-axis direction, and a rotational moving unit 33 that rotates the holding table 10 around an axis parallel to the Z-axis direction.

[0031] The Y-axis moving unit 32 is an indexing feed unit that moves the holding table 10 and the focal point 27 of the laser beam 21 of the laser beam application unit 20 relatively in the Y-axis direction. In the first embodiment, the Y-axis moving unit 32 is installed on the device body 2 of the laser beam application device 1. The Y-axis moving unit 32 supports the moving plate 5 that supports the X-axis moving unit 31 so that the moving plate 5 is movable in the Y-axis direction.

[0032] The X-axis moving unit 31 is a processing feed unit that moves the holding table 10 and the focal point 27 of the laser beam 21 of the laser beam application unit 20 relatively in the X-axis direction. 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 33 that rotates the holding table 10 about an axis parallel to the Z-axis direction, so that the second moving plate 6 can move freely in the X-axis direction. The second moving plate 6 supports the rotational moving unit 33 and the holding table 10. The rotational moving unit 33 supports the holding table 10.

[0033] The X-axis moving unit 31 and the Y-axis moving unit 32 each include a well-known ball screw rotatably mounted 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 and 6 movably in the X-axis direction or the Y-axis direction. The rotational moving unit 33 includes a motor for rotating the holding table 10 about its axis.

[0034] The laser beam application device 1 also includes an X-axis position detection unit (not shown) for detecting the position of the holding table 10 in the X-axis direction, a Y-axis position detection unit (not shown) for detecting the position of the holding table 10 in the Y-axis direction, and a Z-axis position detection unit (not shown) for detecting the position of the laser beam application unit 20 in the Z-axis direction. Each position detection unit outputs the detection result to the control unit 100.

[0035] 3 for detecting the position of the condenser lens 23 of the laser beam application unit 20 in the Z-axis direction. The lens position detection unit 54 outputs the detection result to the control unit 100. In the first embodiment, the lens position detection unit 54 acquires the position of the condenser lens 23, detects the distance between the condenser lens 23 of the laser beam application unit 20 and the holding surface 11 of the holding table 10 based on the acquired position information of the condenser lens 23, and outputs information about the detected distance to the control unit 100. Note that in the present invention, the lens position detection unit 54 may acquire the position of the condenser lens 23 as information about the distance between the condenser lens 23 of the laser beam application unit 20 and the holding surface 11 of the holding table 10, and output the acquired position information of the condenser lens 23 to the control unit 100.

[0036] The imaging unit 40 captures an image of the wafer 200 held on the holding table 10. The imaging unit 40 includes an imaging element such as a CCD (Charge Coupled Device) imaging element or a CMOS (Complementary MOS) imaging element that captures an image of an object facing the objective lens in the Z-axis direction. In the first embodiment, as shown in FIG. 1, the imaging unit 40 is disposed at the tip of a second support column 7 whose base end is supported by the standing wall 3, and the objective lens is disposed at a position aligned with the condenser lens 23 along the X-axis direction. The second support column 7 is parallel to the support column 4.

[0037] The imaging unit 40 acquires the image captured by the imaging element and outputs the acquired image to the control unit 100. The imaging unit 40 also captures an image of the wafer 200 held on the holding surface 11 of the holding table 10 and acquires an image for performing alignment between the wafer 200 and the laser beam application unit 20.

[0038] Laser beam application device 1 also includes a light-receiving unit 70 shown in Fig. 3. In the first embodiment, light-receiving unit 70 receives plasma light 21-1 generated by irradiation of wafer 200 held on holding table 10 with laser beam 21, and outputs information relating to the light intensity of received plasma light 21-1 to control unit 100.

[0039] Light-receiving unit 70 includes second collecting lens 71 and light-receiving section 72. Second collecting lens 71 faces focal point 27 of laser beam 21 from laser beam application unit 20 along an optical axis that intersects all of the X-axis direction, Y-axis direction, and Z-axis direction. Second collecting lens 71 transmits plasma light 21-1 generated by irradiation with laser beam 21, and collects plasma light 21-1 on light-receiving section 72. In embodiment 1, the position of second collecting lens 71 in the direction along the optical axis can be adjusted by lens movement unit 73.

[0040] Light receiving unit 72 receives plasma light 21-1 generated by irradiation with laser beam 21, detects the light intensity of received plasma light 21-1, and outputs information corresponding to the light intensity of received plasma light 21-1 to control unit 100. In the first embodiment, light receiving unit 72 is configured by a well-known photoelectric sensor or an imaging device equipped with an imaging element such as a CCD imaging element or a CMOS (Complementary MOS) imaging element.

[0041] Furthermore, in the first embodiment, light-receiving unit 70 includes bandpass filter 74 disposed between second collecting lens 71 and light-receiving section 72. In the first embodiment, bandpass filter 74 transmits plasma light 21-1 in a predetermined frequency band and does not transmit light in other frequency bands. The predetermined frequency band is a range of light frequencies between a predetermined upper limit frequency and a predetermined lower limit frequency that is lower than the upper limit frequency and includes the frequency of plasma light 21-1. In other words, bandpass filter 74 transmits plasma light 21-1 generated by irradiation with laser beam 21.

[0042] In light-receiving unit 70, plasma light 21-1 generated by irradiation with laser beam 21 is transmitted and collected by second condenser lens 71, and received by light-receiving section 72 via bandpass filter 74. Information relating to the light intensity of plasma light 21-1 received by light-receiving section 72 is output to control unit 100. In embodiment 1, light-receiving unit 70 is disposed at the tip of third support column 8, the base end of which is supported by standing wall 3, as shown in FIG. 1 . Third support column 8 is parallel to support columns 4 and 7.

[0043] The control unit 100 controls each of the above-mentioned components of the laser beam application apparatus 1, causing the laser beam application apparatus 1 to perform processing operations on the wafer 200. The control unit 100 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 RAM (random access memory), and an input / output interface device. The arithmetic processing device of the control unit 100 performs arithmetic processing in accordance with a computer program stored in the storage device, and outputs control signals for controlling the laser beam application apparatus 1 to the above-mentioned components of the laser beam application apparatus 1 via the input / output interface device, thereby realizing the functions of the control unit 100.

[0044] The laser beam application device 1 also includes a display unit, which is a display means configured with a liquid crystal display device or the like that displays the status of the processing operation, images, etc., and an input unit, which is an input means used by the operator to input processing conditions, etc. The display unit and the input unit are connected to the control unit 100. The input unit is configured with at least one of a touch panel provided on the display unit and an external input device such as a keyboard. The display unit may be another information device such as a tablet terminal, smartphone, or PC (Personal Computer) that is connected to the laser beam application device 1 by wire or wirelessly.

[0045] As shown in Fig. 1, the control unit 100 includes a command section 101, an information acquisition section 102, a recording section 103, and a focus detection section 104. Fig. 4 is a plan view of a wafer schematically showing a position where laser beam irradiation is instructed by the command section of the laser beam application device shown in Fig. 1. Fig. 5 is a diagram schematically showing data recorded by the recording section of the laser beam application device shown in Fig. 1.

[0046] The command unit 101 outputs a command to each component of the laser beam application device 1 to relatively move the holding table 10 and the laser beam application unit 20 using the first moving unit 30 while changing the distance in the Z axis direction between the condenser lens 23 of the laser beam application unit 20 and the holding surface 11 of the holding table 10 using the second moving unit 50, thereby irradiating the wafer 200 with the laser beam 21. In the first embodiment, the command unit 101 relatively moves the holding table 10 and the laser beam application unit 20 using the first moving unit 30 while changing the distance in the Z axis direction between the condenser lens 23 of the laser beam application unit 20 and the holding surface 11 of the holding table 10 using the second moving unit 50, thereby irradiating the laser beam 21 at an irradiation position 212 on a surface 202 of a peripheral excess region 204 of the wafer 200 held on the holding table 10 shown in FIG. In FIG. 4, in the first embodiment, the irradiation position 212 on the front surface 202 of the wafer 200 where the laser beam 21 is irradiated in response to a command from the command unit 101 is indicated by a solid line.

[0047] The information acquisition unit 102 acquires information regarding the light intensity of the plasma light 21-1 received by the light receiving unit 70 and information regarding the distance between the focusing lens 23 of the laser beam application unit 20 and the holding surface 11 of the holding table 10 detected by the lens position detection unit 54 at the time the laser beam 21 was applied, generates data 80 (shown in Figure 5) that links the information regarding the light intensity of the plasma light 21-1 with the information regarding the distance between the focusing lens 23 of the laser beam application unit 20 and the holding surface 11 of the holding table 10 at the time the laser beam 21 was applied, and stores the generated data 80 in the recording unit 103. In addition, the information acquisition unit 102 may acquire the position of the focusing lens 23 of the laser beam application unit 20 detected by the lens position detection unit 54 at the time when the laser beam 21 was applied, generate data linking information about the light intensity of the plasma light 21-1 with the position of the focusing lens 23 of the laser beam application unit 20 at the time when the laser beam 21 was applied, and store the generated data in the recording unit 103.

[0048] The horizontal axis of data 80 shown in FIG. 5 represents the distance between condenser lens 23 of laser beam application unit 20 and holding surface 11 of holding table 10 at the time of application of laser beam 21, with the distance gradually increasing toward the right. The vertical axis of data 80 shown in FIG. 5 represents the light intensity of plasma light 21-1, with the light intensity of plasma light gradually increasing toward the top. For this reason, data 80 shown in FIG. 5 is data that links the distance at the time of application of laser beam 21 with the light intensity of plasma light 21-1 acquired by information acquisition unit 102. Recording unit 103 records data 80 acquired and generated by information acquisition unit 102.

[0049] Focus detection unit 104 detects information about the distance between condenser lens 23 of laser beam application unit 20 and holding surface 11 of holding table 10 at the time when laser beam 21 is applied in a state where focus 27 of laser beam 21 is aligned with surface 202 of wafer 200 to be irradiated with laser beam 21, in accordance with information about the light intensity of plasma light 21-1 in data 80 recorded in recording unit 103. In the first embodiment, focus detection unit 104 detects maximum light intensity 81 of plasma light 21-1 in data 80, and detects distance 82 linked to maximum light intensity 81 detected in data 80.

[0050] The focus detection unit 104 stores the detected distance 82 in the recording unit 103 as the distance between the condenser lens 23 of the laser beam application unit 20 and the holding surface 11 of the holding table 10 at the time when the laser beam 21 is applied in a state where the focal point 27 of the laser beam 21 is aligned with the surface 202 of the wafer 200 to be irradiated with the laser beam 21, in accordance with the light intensity of the plasma light 21-1 in the data 80 recorded in the recording unit 103. Thus, in the first embodiment, the focus detection unit 104 detects the distance 82 at the time when the light intensity of the plasma light 21-1 in the data 80 recorded in the recording unit 103 is maximum as the state where the focal point 27 of the laser beam 21 is aligned with the surface 202 of the wafer 200 to be irradiated with the laser beam 21. In the example shown in FIG. 5, the distance 82 is 22.5 mm. Note that the laser beam application unit 20 and the holding table 10 move relative to each other, and either one may move, so the distance 82 between the laser beam application unit 20 and the wafer 200 is recorded, but the information regarding the distance between the laser beam application unit 20 and the wafer 200 is not limited to the distance 82. For example, in the case of a mechanism in which the condenser lens 23 of the laser beam application unit 20 moves relative to the holding surface 11, the position of the condenser lens 23 and the light intensity of the plasma light 21-1 may be recorded in association with each other, and the position of the condenser lens 23 is also included in the information regarding the distance referred to in the present invention.

[0051] The functions of the command unit 101, the information acquisition unit 102, and the focus detection unit 104 are realized by the arithmetic processing unit performing arithmetic processing in accordance with a computer program stored in a storage device. The function of the recording unit 103 is realized by the above-mentioned storage device.

[0052] Next, a description will be given of the processing operation of the laser beam application apparatus 1 having the above-described configuration. In the laser beam application apparatus 1, the control unit 100 receives and registers processing conditions input by an operator, and the wafer 200 is placed via adhesive tape 211 on the holding surface 11 of the holding table 10 positioned in the carry-in / out area. When the control unit 100 receives an instruction to start the processing operation from the operator, the laser beam application apparatus 1 starts the processing operation.

[0053] In the processing operation, the laser beam application device 1 carries out the laser beam application method according to embodiment 1. Fig. 6 is a flowchart showing the flow of the laser beam application method according to embodiment 1. As shown in Fig. 6, the laser beam application method shown in Fig. 6 includes a holding step 1001, a laser beam application step 1002, a light receiving step 1003, and a focus detection step 1004.

[0054] (holding step) The holding step 1001 is a step of holding the wafer 200 on the holding surface 11 of the holding table 10. In the holding step 1001, the control unit 100 suction-holds the wafer 200 on the holding surface 11 of the holding table 10 via the adhesive tape 211, and also causes the clamp section to clamp the annular frame 210. In the holding step 1001, the control unit 100 of the laser beam application device 1 controls the first moving unit 30 to move the holding table 10 to the processing area, and the imaging unit 40 captures an image of the wafer 200 suction-held on the holding table 10 to obtain the image, thereby performing an alignment step of detecting the processing area.

[0055] (Laser beam irradiation step) The laser beam irradiation step 1002 is a step in which the distance in the Z-axis direction between the wafer 200 and the focusing lens 23 of the laser beam irradiation unit 20 is changed relatively along the optical axis of the laser beam 21, while the holding table 10 and the laser beam irradiation unit 20 are moved relatively in a direction parallel to the holding surface 11, thereby irradiating the laser beam 21 onto the wafer 200 held on the holding table 10.

[0056] In the laser beam irradiation step 1002, the command section 101 of the control unit 100 controls the second moving unit 50 and the first moving unit 30 of the laser beam irradiation device 1 to move the focusing lens 23 in the Z-axis direction and to move the wafer 200 held on the holding table 10 and the focusing lens 23 in the X-axis direction, the Y-axis direction, and around the axis, thereby irradiating the peripheral excess area 204 with the laser beam 21.

[0057] (light receiving step) Light receiving step 1003 is a step in which plasma light 21-1 generated by irradiating wafer 200 with laser beam 21 is received by light receiving unit 70. Light receiving step 1003 is performed simultaneously with laser beam irradiating step 1002 in order for light receiving unit 70 to receive plasma light 21-1 generated by irradiating wafer 200 with laser beam 21. In light receiving step 1003, in laser beam irradiation device 1, information acquisition section 102 of control unit 100 generates data 80 from the detection result of lens position detection unit 54 and the detection result of the light receiving section of light receiving unit 70, and records generated data 80 in recording section 103.

[0058] (Focus detection steps) Focus detection step 1004 is a step of detecting, based on information about the light intensity of received plasma light 21-1, information about distance 82 at which focal point 27 of laser beam 21 is aligned with surface 202 of wafer 200 to be irradiated with laser beam 21. In focus detection step 1004, focus detection section 104 of control unit 100 in laser beam application device 1 detects maximum light intensity 81 of plasma light 21-1 in data 80, detects distance 82 associated with detected maximum light intensity 81 in data 80, and records this in recording section 103. Thus, in focus detection step 1004, focus detection section 104 detects distance 82 at which the light intensity of plasma light 21-1 is maximum as a state in which focal point 27 of laser beam 21 is aligned with surface 202 of wafer 200 to be irradiated with laser beam 21, and the laser beam application method is terminated.

[0059] In the processing operation, the control unit 100 of the laser beam application device 1 performs alignment to detect the position of the planned dividing line 205, and controls the second moving unit 50 to position the condenser lens 23 of the laser beam application unit 20 at the distance 82 detected by the focus detection unit 104 and recorded in the recording unit 103, thereby setting the focus 27 of the laser beam application unit 20 on the front surface 202 of the wafer 200. In the processing operation, the control unit 100 of the laser beam application device 1 controls the first moving unit 30 to relatively move the holding table 10 and the laser beam application unit 20, while irradiating the substrate 201 with a pulsed laser beam 21 from the front surface 202 side along the planned dividing line 205 of the wafer 200.

[0060] In the first embodiment, in the processing operation, when the laser beam application device 1 has applied the laser beam 21 along all of the planned dividing lines 205, it stops applying the laser beam 21 and moves the holding table 10 to the carry-in / out area. In the processing operation, the laser beam application device 1 positions the holding table 10 in the carry-in / out area, stops suction holding of the wafer 200 on the holding table 10, and releases the clamping of the annular frame 210 of the clamp unit, thereby completing the processing operation.

[0061] The laser beam application apparatus 1 and the laser beam application method according to the first embodiment described above detect the distance 82 at which the light intensity of the plasma light 21-1 generated by the absorption of the laser beam 21 by the wafer 200 reaches a maximum light intensity 81 as a state in which the focal point 27 of the laser beam 21 is aligned with the surface 202 of the wafer 200 to be irradiated with the laser beam 21. For this reason, the laser beam application apparatus 1 and the laser beam application method according to the first embodiment do not need to image the processed groove formed after irradiating the laser beam 21, measure the width, and compare the images, and the focal point 27 can be set by the laser beam application apparatus 1 alone.

[0062] As a result, the laser beam application device 1 and the laser beam application method according to the first embodiment have the advantage that the focus 27 of the laser beam 21 can be easily set.

[0063] [Embodiment 2] A laser beam application device and a laser beam application method according to a second embodiment of the present invention will be described with reference to the drawings. Fig. 7 is a perspective view showing an example of the configuration of a laser beam application device according to the second embodiment. Fig. 8 is a diagram schematically showing the configuration of a laser beam application unit and a light receiving unit of the laser beam application device shown in Fig. 7. Fig. 9 is a diagram schematically showing data recorded by a recording unit of the laser beam application device according to the second embodiment. In Figs. 7, 8 and 9, the same parts as those in the first embodiment are designated by the same reference numerals, and their description will be omitted.

[0064] The laser beam application device 1-2 of the second embodiment is the same as that of the first embodiment except that, as shown in FIG. 7, the imaging unit 40 is arranged at the tip of the support column 4, the configuration of the laser beam application unit 20-2 and the light receiving unit 70-2 shown in FIG. 8, the light receiving unit 70 receives the reflected light 21-2 of the laser beam 21, and the data 80-2 (shown in FIG. 9) acquired by the information acquisition unit 102 and recorded in the recording unit 103 are different.

[0065] When the laser beam 21 is irradiated onto the wafer 200, it generates the aforementioned plasma light 21-1 and also reflects the laser beam 21 (this reflected laser beam 21 is reflected light 21-2). Since the laser beam 21 has a wavelength that is absorbed by the substrate 201 of the wafer 200, when the laser beam 21 is irradiated onto the wafer 200, the closer the focal point 27 is to the surface 202 of the substrate 201, the more easily the laser beam 21 is absorbed by the substrate 201, and the energy of the laser beam 21 is used for processing, so the light intensity of the reflected light 21-2 becomes weaker, and the farther the focal point 27 is from the surface 202 of the substrate 201, the less easily the laser beam 21 is absorbed by the substrate 201, so the energy of the laser beam 21 is not used for processing, and the light intensity of the reflected light 21-2 becomes stronger. For this reason, the light intensity of the reflected light 21-2 of the laser beam 21 is weakest when the focal point 27 of the laser beam 21 is located on the surface 202 of the substrate 201, and gradually increases as the distance of the focal point 27 from the surface 202 of the substrate 201 in the Z-axis direction increases.

[0066] 8, the laser beam application unit 20-2 according to the second embodiment includes a beam splitter 29 between the oscillator 22 and the condenser lens 23, which transmits the laser beam 21 and reflects the reflected light 21-2. The beam splitter 29 transmits the laser beam 21 emitted by the oscillator 22 toward the condenser lens 23 and reflects the reflected light 21-2.

[0067] The light-receiving unit 70-2 according to the second embodiment receives reflected light 21-2 generated by irradiation of the wafer 200 held on the holding table 10 with the laser beam 21, and outputs information about the light intensity of the received reflected light 21-2 to the control unit 100. As shown in Fig. 8, the light-receiving unit 70-2 according to the second embodiment at least includes a band-pass filter 74 that transmits reflected light 21-2 of a predetermined frequency band out of the reflected light 21-2 reflected by the beam splitter 29 and does not transmit light of other frequency bands, and a light-receiving section 72 that receives the reflected light 21-2 reflected by the beam splitter 29 and transmitted by the band-pass filter 74.

[0068] The light receiving unit 72 receives reflected light 21-2 generated by irradiation with the laser beam 21, detects the light intensity of the received reflected light 21-2, and outputs information about the light intensity of the received reflected light 21-2 to the control unit 100. In the second embodiment, the light receiving unit 72 is configured with a power meter. Note that when the output of the laser beam 21 used for processing is high, the intensity of the reflected light 21-2 also increases, so a power meter that can measure high-output light is preferable. However, if a filter that attenuates the reflected light 21-2 is installed in the optical path before it is received by the light receiving unit 72, the reflected light 21-2 can be acquired not only by a power meter but also by a known photoelectric sensor or a known imaging unit.

[0069] The light receiving unit 70-2 receives reflected light 21-2, which is generated by irradiation of the laser beam 21, passes through the condenser lens 23, and is reflected by the beam splitter 29, at a light receiving section 72 via a band pass filter 74, and outputs information relating to the light intensity of the reflected light received by the light receiving section 72 to the control unit 100. In the second embodiment, the light receiving unit 70-2 is disposed inside the housing of the laser beam irradiation unit 20-2.

[0070] The information acquisition unit 102 of the laser beam application device 1-2 of embodiment 2 acquires information corresponding to the light intensity of the reflected light 21-2 received by the light receiving unit 70 and information corresponding to the distance between the focusing lens 23 of the laser beam application unit 20-2 and the holding surface 11 of the holding table 10 detected by the lens position detection unit 54 at the time the laser beam 21 was applied, generates data 80-2 (shown in Figure 9) linking the light intensity of the reflected light 21-2 with the distance between the focusing lens 23 of the laser beam application unit 20 and the holding surface 11 of the holding table 10 at the time the laser beam 21 was applied, and stores the generated data 80-2 in the recording unit 103.

[0071] The horizontal axis of data 80-2 shown in FIG. 9 indicates the distance between the condenser lens 23 of the laser beam application unit 20-2 and the holding surface 11 of the holding table 10 at the time of application of the laser beam 21, and shows a case where the distance gradually increases toward the right. The vertical axis of data 80-2 shown in FIG. 9 indicates the light intensity of the reflected light 21-2, and shows a case where the light intensity of the reflected light 21-2 gradually increases toward the top. For this reason, the data 80-2 shown in FIG. 9 is data that links the distance at the time of application of the laser beam 21 with the light intensity of the reflected light 21-2 acquired by the information acquisition unit 102. In the second embodiment, the recording unit 103 records the data 80-2 acquired and generated by the information acquisition unit 102.

[0072] Furthermore, the focus detection unit 104 of the laser beam application device 1-2 according to the second embodiment detects the distance between the condenser lens 23 of the laser beam application unit 20-2 and the holding surface 11 of the holding table 10 at the time when the laser beam 21 is applied in a state in which the focus 27 of the laser beam 21 is aligned with the surface 202 of the wafer 200 to be irradiated with the laser beam 21, in accordance with the light intensity of the reflected light 21-2 of the data 80-2 recorded in the recording unit 103. In the second embodiment, the focus detection unit 104 detects the minimum light intensity 81-2 of the reflected light 21-2 of the data 80-2, and detects the distance 82-2 associated with the minimum light intensity 81-2 detected in the data 80-2.

[0073] The focus detection unit 104 stores the detected distance 82-2 in the recording unit 103 as the distance between the condenser lens 23 of the laser beam application unit 20-2 and the holding surface 11 of the holding table 10 at the time when the laser beam 21 is applied in a state where the focal point 27 of the laser beam 21 is aligned with the surface 202 of the wafer 200 to be irradiated with the laser beam 21, in accordance with the light intensity of the reflected light 21-2 of the data 80-2 recorded in the recording unit 103. Thus, in the second embodiment, the focus detection unit 104 detects the distance 82-2 at the time when the light intensity of the reflected light 21-2 of the data 80-2 recorded in the recording unit 103 is minimum as the state where the focal point 27 of the laser beam 21 is aligned with the surface 202 of the wafer 200 to be irradiated with the laser beam 21. In the example shown in FIG. 9, the distance 82 is 22 mm. Note that the laser beam application unit 20-2 and the holding table 10 move relative to each other, and either one may move, so the distance 82 between the laser beam application unit 20-2 and the wafer 200 is recorded, but the information regarding the distance between the laser beam application unit 20-2 and the wafer 200 is not limited to the distance 82. For example, in the case of a mechanism in which the condenser lens 23 of the laser beam application unit 20-2 moves relative to the holding surface 11, the position of the condenser lens 23 and the light intensity of the plasma light 21-1 may be recorded in association with each other, and the position of the condenser lens 23 is also included in the information regarding the distance referred to in the present invention.

[0074] The laser beam application method according to the second embodiment, like the first embodiment, includes a holding step 1001, a laser beam application step 1002, a light receiving step 1003, and a focus detection step 1004. In the laser beam application method according to the second embodiment, in the holding step 1001, like the first embodiment, the wafer 200 is held on the holding surface 11 of the holding table 10, and in the laser beam application step 1002, like the first embodiment, the wafer 200 held on the holding table 10 is irradiated with a laser beam 21.

[0075] The light receiving step 1003 of the laser beam application method according to the second embodiment is a step in which the light receiving unit 70-2 receives reflected light 21-2 generated by irradiating the wafer 200 with the laser beam 21. In the laser beam application method according to the second embodiment, in the light receiving step 1003, the light receiving unit 70-2 receives reflected light 21-2 generated by irradiating the wafer 200 with the laser beam 21. In the laser beam application method according to the second embodiment, in the light receiving step 1003, the information acquisition unit 102 of the control unit 100 generates data 80-2 from the detection result of the lens position detection unit 54 and the detection result of the light receiving part of the light receiving unit 70, and records the generated data 80-2 in the recording unit 103.

[0076] The focus detecting step 1004 of the laser beam application method according to the second embodiment is a step of detecting, based on the light intensity of the received reflected light 21-2, a distance 82-2 at which the focus 27 of the laser beam 21 is aligned with the surface 202 of the surface of the wafer 200 that is irradiated with the laser beam 21. In the focus detecting step 1004 of the laser beam application method according to the second embodiment, the focus detecting section 104 of the control unit 100 detects the minimum light intensity 81-2 of the reflected light 21-2 of the data 80-2, and detects and records in the recording section 103 the distance 82-2 associated with the detected minimum light intensity 81-2 in the data 80-2. Thus, in the focus detection step 1004 of the laser beam application method according to embodiment 2, the focus detection unit 104 detects the distance 82-2 at which the light intensity of the reflected light 21-2 is at its minimum as the state in which the focus 27 of the laser beam 21 is aligned with the surface 202 of the wafer 200 onto which the laser beam 21 is irradiated.

[0077] The laser beam application apparatus 1-2 and the laser beam application method according to the second embodiment detect a distance 82-2 at which the light intensity of reflected light 21-2 generated by absorption of the laser beam 21 by the wafer 200 becomes a minimum light intensity 81-2 as a state in which the focal point 27 of the laser beam 21 is aligned with the surface 202 of the wafer 200 to be irradiated with the laser beam 21. For this reason, the laser beam application apparatus 1-2 and the laser beam application method according to the second embodiment do not require imaging of the formed processed groove after irradiating the laser beam 21, measuring and comparing the width, and can set the focal point 27 by the laser beam application apparatus 1-2 alone, thereby achieving the effect of easily setting the focal point 27 of the laser beam 21, as in the first embodiment.

[0078] [Modification] A laser beam application device and a laser beam application method according to modifications of the first and second embodiments of the present invention will be described with reference to the drawings. Fig. 10 is a side view, partially in cross section, showing a schematic configuration example of the laser beam application device according to the first and second embodiments. Fig. 11 is a diagram showing a schematic configuration of a laser beam application unit and a light receiving unit of the laser beam application device shown in Fig. 10. In Figs. 10 and 11, the same parts as those in the first and second embodiments are designated by the same reference numerals, and their description will be omitted.

[0079] In the laser beam application apparatus 1-3 and the laser beam application method according to the modified example, the wafer 200-3 to be processed is a so-called TAIKO (registered trademark) wafer in which the back surface 209 of the device region 203 is ground to form a circular recess 213, and the back surface 209 of the peripheral excess region 204 is not ground to form an annular protrusion 214, as shown in FIG.

[0080] 10 , in a laser beam application device 1-3 according to a modified example, a holding table 10-3 is arranged with the holding surface 11 facing downward, and the condenser lens 23 of the laser beam application unit and the light-receiving unit 70 are supported on a support base 9 installed below the holding table 10. In this modified example, in the laser beam application device 1-3, the condenser lens 23 of the laser beam application unit 20-3 is arranged closer to the outer edge of the holding surface 11 of the holding table 10 than the light-receiving unit 70-3. In this modified example, the light-receiving section 72 of the light-receiving unit 70-3 is configured by the well-known photoelectric sensor, well-known imaging device, or power meter described in the first or second embodiment.

[0081] 10 and 11 , in the laser beam application device 1-3, the laser beam application unit 20-3 applies a laser beam 21 along a direction intersecting the vertical and horizontal directions so as to gradually move toward the inner periphery of the holding surface 11 as it moves toward the holding surface 11 of the holding table 10, and the light receiving unit 70-3 receives plasma light 21-1 or reflected light 21-2 generated by the application of the laser beam 21 and along a direction intersecting the vertical and horizontal directions so as to gradually move toward the inner periphery of the holding surface 11 as it moves downward. In the laser beam application device 1-3, as described above, the laser beam application unit 20-3 and the light receiving unit 70-3 are positioned diagonally downward rather than directly below the processing point, thereby preventing debris generated by the application of the laser beam 21 and falling from adhering to the condenser lens 23 of the laser beam application unit 20-3, etc.

[0082] As in the first or second embodiment, the laser beam application apparatus 1-3 and the laser beam application method according to the modified example receive, with the light receiving unit 70-3, the plasma light 21-1 or the reflected light 21-2 generated when the laser beam 21 is absorbed by the wafer 200, detect the distances 82, 82-2, and determine the detected distances 82, 82-2 as a state in which the focal point 27 of the laser beam 21 is aligned with the surface 202 of the wafer 200 to be irradiated with the laser beam 21. For this reason, the laser beam application apparatus 1-3 and the laser beam application method according to the modified example do not require imaging the formed processed groove after irradiating the laser beam 21, measuring and comparing the widths, and can set the focal point using the laser beam application apparatus 1-3 alone, thereby achieving the effect of easily setting the focal point 27 of the laser beam 21, as in the first or second embodiment.

[0083] The laser beam application method of the present invention is performed as an initial setting when the apparatus is installed in a factory, or at any timing, such as when a predetermined number of wafers have been processed or after a predetermined period of time has passed. By registering the timing of execution in the laser beam application apparatuses 1, 1-2, and 1-3, the control unit 100 may automatically execute the laser beam application method of the present invention, or an operator may be notified that it is time to execute the method by using a notification means such as a display on a display unit, a sound, a light, or information transmission to another communication device. The laser beam application method of the present invention is performed when a predetermined timing set in advance arrives, before the execution of the processing step of processing the wafers 200 along the planned dividing lines 205.

[0084] Specifically, a wafer 200 to be actually processed in the processing step, or a dummy wafer not used in the processing step, is held on the holding table 10, and the laser beam application method of the present invention is performed in the peripheral surplus region 204 of the held wafer 200 to focus the laser beam 21. In the case of a dummy wafer, the laser beam 21 may be applied to any location on the wafer surface, not just the peripheral surplus region 204. After the focus detection step 1004 is performed, if there is a deviation from the previously set focal position, the amount of deviation is stored as a correction value, and a correction step is performed to correct the focal position of the laser beam 21 when performing the processing step, and after the correction step is performed, the processing step is started.

[0085] The present invention is not limited to the above-described embodiment. That is, various modifications can be made without departing from the gist of the present invention. For example, in the present invention, the laser beam 21 may be irradiated onto the back surface 209 of the wafer 200 to detect the distances 82 and 82-2. In addition, in the present invention, the laser beam 21 may be irradiated onto a dummy wafer on which no device 206 is formed to detect the distances 82 and 82-2. [Explanation of symbols]

[0086] 1,1-2,1-3 Laser beam irradiation device 10,10-3 Holding table 11 Holding surface 20, 20-2, 20-3 Laser beam irradiation unit 21 Laser beam 21-1 Plasma light 21-2 Reflected light 30 First Mobile Unit 50 Second Mobile Unit 70, 70-2, 70-3 Light receiving unit 82,82-2 distance 100 control unit 101 Headquarters 102 Information acquisition department 103 Recording Section 104 Focus detection unit 200,200-3 wafers 202 Surface (surface irradiated with laser beam) 1001 holding steps 1002 Laser beam irradiation step 1003 light receiving steps 1004 focus detection steps X: Parallel to the holding surface Y Parallel to the holding surface

Claims

1. A wafer having a device region on a surface on which devices are formed and a peripheral excess region surrounding the device region and on which no devices are formed, comprising: a holding table for holding a wafer on a holding surface; a laser beam application unit that applies a laser beam to a wafer held on a holding surface of the holding table; a first moving unit that moves the holding table and the laser beam application unit relatively in a direction parallel to the holding surface; a second moving unit that changes the distance between the laser beam application unit and the wafer; a light receiving unit that receives plasma light or reflected light generated by irradiating the wafer with a laser beam; a control unit; The control unit a command section that issues a command to irradiate the peripheral excess area of ​​the wafer with the laser beam by moving the holding table and the laser beam application unit relatively with the first moving unit while changing the distance with the second moving unit; an information acquiring unit that acquires information about the light intensity of the plasma light or the reflected light received by the light receiving unit; a recording unit that records information about the distance at the time when the laser beam is irradiated and information about the light intensity acquired by the information acquisition unit in association with each other; a focus detection unit that detects information about the distance when the focus of the laser beam is aligned with the surface of the wafer that is irradiated with the laser beam, in accordance with the information about the light intensity recorded in the recording unit; Equipped with a laser beam application device for applying the laser beam along a planned dividing line of the device region of the wafer while controlling the second moving unit to set the distance between the laser beam application unit and the wafer to the distance detected by the focus detection unit, and controlling the first moving unit to move the holding table and the laser beam application unit relatively.

2. the light receiving unit receives plasma light generated by irradiating the wafer with the laser beam; 2. The laser beam irradiation device according to claim 1, wherein the focus detection unit detects the distance at the time when the light intensity of the plasma light is at its maximum in the recording unit as a state in which the focus of the laser beam is aligned with the surface of the wafer that is irradiated with the laser beam.

3. a laser beam application unit that applies a laser beam to a wafer held on a holding surface of the holding table; a first moving unit that moves the holding table and the laser beam application unit relatively in a direction parallel to the holding surface; a second moving unit that changes the distance between the laser beam application unit and the wafer; a light receiving unit that receives plasma light or reflected light generated by irradiating the wafer with a laser beam; a control unit; The control unit a command section that issues a command to relatively move the holding table and the laser beam application unit by the first moving unit while changing the distance by the second moving unit, and to irradiate the wafer with the laser beam; an information acquiring unit that acquires information about the light intensity of the plasma light or the reflected light received by the light receiving unit; a recording unit that records information about the distance at the time when the laser beam is irradiated and information about the light intensity acquired by the information acquisition unit in association with each other; a focus detection unit that detects information about the distance when the focus of the laser beam is aligned with the surface of the wafer that is irradiated with the laser beam, in accordance with the information about the light intensity recorded in the recording unit; Equipped with the light receiving unit detects reflected light generated by irradiating the wafer with the laser beam; The focus detection unit detects the distance at the time when the light intensity of the reflected light is minimum in the recording unit as a state in which the focus of the laser beam is aligned with the surface of the wafer that is irradiated with the laser beam.

4. A laser beam irradiation method, comprising: a holding step of holding a wafer, on a holding surface of a holding table, the wafer having a device region on the surface of which devices are formed and a peripheral excess region surrounding the device region and in which no devices are formed; a laser beam application step in which the holding table and the laser beam application unit are moved relatively in a direction parallel to the holding surface while the distance between the wafer and the laser beam application unit is changed relatively along the optical axis of the laser beam, thereby applying a laser beam to an outer peripheral excess region of the wafer held in the holding step; a light receiving step of receiving plasma light or reflected light generated by irradiating the wafer with the laser beam with a light receiving unit; a focus detection step of detecting information about the distance at which the focus of the laser beam is aligned with the surface of the wafer that is irradiated with the laser beam, based on information about the light intensity of the received plasma light or the reflected light; Equipped with a laser beam irradiation method characterized by setting the distance between the laser beam irradiation unit and the wafer to the appropriate distance, and irradiating the laser beam along the planned dividing line of the device region of the wafer while moving the holding table and the laser beam irradiation unit relatively.

5. the light receiving unit receives plasma light generated by irradiating the wafer with the laser beam; 5. The laser beam irradiation method according to claim 4, wherein the focus detection step detects the distance at the time when the light intensity of the plasma light is at its maximum as a state in which the focus of the laser beam is aligned with the surface of the wafer that is irradiated with the laser beam.

6. A laser beam irradiation method, comprising: a holding step of holding the wafer on a holding surface of a holding table; a laser beam application step in which the holding table and the laser beam application unit are moved relatively in a direction parallel to the holding surface while the distance between the wafer and the laser beam application unit is changed relatively along the optical axis of the laser beam, thereby irradiating the wafer held in the holding step with a laser beam; a light receiving step of receiving plasma light or reflected light generated by irradiating the wafer with the laser beam with a light receiving unit; a focus detection step of detecting information about the distance at which the focus of the laser beam is aligned with the surface of the wafer that is irradiated with the laser beam, based on information about the light intensity of the received plasma light or the reflected light; Equipped with the light receiving unit detects reflected light generated by irradiating the wafer with the laser beam; The focus detection step detects the distance at the time when the light intensity of the reflected light is minimum, as a state in which the focus of the laser beam is aligned with the surface of the wafer that is irradiated with the laser beam.

Images