JP2017166961A - Device and method for detecting inside of workpiece - Google Patents

Abstract

Kind Code: A1 A method and apparatus for detecting the inside of a workpiece that can detect a processing mark formed inside the workpiece by irradiating the workpiece with a laser beam without actually dividing the wafer. provide. A holding means for holding a workpiece, an illuminating means for irradiating the workpiece with light having a wavelength that is transparent to the workpiece, and a workpiece. Inside the workpiece, which is constituted by at least an imaging means 50 for imaging the object and a reflecting mirror 583 which is provided to face the side face of the workpiece and reflects light from the side face and guides the light to the imaging means. Detection device. [Selection diagram] FIG.

Description

  The present invention relates to an internal detection apparatus and internal detection method for a workpiece that detects a processing mark such as a modified layer formed by irradiating a workpiece, for example, a silicon wafer, with a laser beam.

  A wafer formed by dividing a plurality of devices such as IC and LSI on the surface by dividing lines is divided into individual devices by a dicing apparatus and used for electric devices such as mobile phones and personal computers.

  In addition to using the above-described dicing apparatus as a technique for dividing a wafer formed on the surface by dividing a plurality of devices by dividing lines, the applicant has a wavelength having transparency to the wafer. A technique for dividing a wafer into individual devices by applying an external force after forming a modified layer along the planned dividing line and irradiating with a laser beam condensing point positioned inside the wafer (for example, Patent Document 1) Furthermore, the numerical aperture of the condensing lens for condensing the pulsed laser beam is appropriately set, and the pulsed laser beam condensed by the condensing lens is irradiated along the planned dividing line and positioned on the single crystal substrate. A so-called shield tunnel is formed by growing a pore and an amorphous material that shields the pore between the focused point and the side on which the pulse laser beam is incident. Forming a technique for dividing the wafer with external force is applied to the individual devices (e.g., see. Patent Document 2) proposes.

  The technology for dividing a wafer as described above into individual devices has been improved every day. In particular, the above-mentioned modified layers, shield tunnels, etc. are formed in the single crystal substrate by irradiating a laser beam. In the case of dividing by applying an external force, various conditions for irradiating the laser beam, such as changes in output, repetition frequency, numerical aperture set by the condensing lens, condensing point position, etc. It is known to affect the formation of processing marks formed on the surface. Therefore, in order to improve the processing efficiency and the product quality, it is necessary to sufficiently study how the change of the laser beam irradiation condition affects the formation of the processing marks.

Japanese Patent No. 3408805 JP 2014-2221483 A

  With a dicing machine that uses a cutting blade to cut the wafer, it is possible to easily detect the processing state such as the cutting depth formed by the cutting blade from the outside even during the processing. When using a processing method that forms a modified layer, shield tunnel, etc. inside the wafer, it is difficult to accurately grasp the dimensions and shape of the processing marks formed inside from the outside. After the processing, an external force is actually applied to divide the wafer along the processing marks and observe the divided surface to grasp the state formed by the laser beam.

  However, when observing the divided surface after dividing the wafer individually, the processing marks formed inside will be destroyed, so the state of the processing marks before destruction, for example, the formed modified layer It is impossible to observe the height etc. of the object strictly. In addition, by changing various conditions when irradiating a laser beam, forming a modified layer, a shield tunnel, etc., forming an external force, dividing it along the planned dividing line, and then observing the dividing surface If the modified layer and shield tunnel are not sufficient, the wafer will not be divided as intended, and even if the divided surface is observed, the processing traces such as the modified layer formed inside must be verified accurately. There is a problem that can not be.

  The present invention has been made in view of the above-mentioned facts, and its main technical problem is to detect a processing trace formed inside by irradiating a workpiece with a laser beam without actually dividing the wafer. An object of the present invention is to provide a method for detecting the inside of a workpiece and a detection device.

  In order to solve the above-mentioned main technical problem, according to the present invention, there is provided an internal detection device for a workpiece that detects a processing mark formed inside by irradiating the workpiece with a laser beam, the workpiece being processed Holding means for holding an object; illumination means for irradiating the workpiece with light having a wavelength that is transmissive to the workpiece; imaging means for imaging the workpiece; There is provided an internal detection device for a workpiece, which is arranged to face the side surface of the workpiece and which includes at least a reflecting mirror that reflects light from the side surface and guides the light to the imaging means.

  According to the present invention, there is also provided an internal detection method for a workpiece that detects a processing mark formed therein by irradiating the workpiece with a laser beam, and the workpiece is held by the holding means. A holding step, an illumination step of irradiating the workpiece with light having a wavelength that is transparent to the workpiece, and a side surface of the workpiece held by the holding means. A reflecting mirror positioning step of reflecting the light from the side surface and guiding it to the imaging means, and imaging the side surface of the workpiece with the imaging means, and forming the reflection mirror on the inside of the workpiece There is provided a method for detecting an inside of a workpiece including a processing mark detection step of detecting a processing mark.

  It is preferable that the method further includes a flattening step of forming a flat portion for detecting the processing mark on the side surface before or after forming the processing mark in the workpiece. .

  According to the internal detection device and internal detection method of the workpiece of the present invention, the size, shape, etc. of the processing mark can be detected by the light transmitted from the side surface of the workpiece without actually dividing the workpiece. Is possible. Further, the internal detection device according to the present invention includes an illuminating unit that irradiates light having a wavelength that is transmissive to the workpiece held by the holding unit, and a workpiece that is held by the holding unit. Since it is composed of an imaging means for imaging and a reflecting mirror disposed on the side surface of the workpiece held by the holding means and reflecting light from the side surface to guide the imaging means, On the other hand, it can be easily and inexpensively configured from an existing laser processing apparatus that has transparency, for example, an imaging unit including an infrared irradiation unit and an infrared camera.

The laser processing apparatus with which the internal detection apparatus which implements the internal detection method of a workpiece based on this invention is applied. Explanatory drawing for demonstrating the state which comprises an internal detection apparatus in the laser processing apparatus shown in FIG. Explanatory drawing for demonstrating the planarization process which forms the flat part in a to-be-processed object applied to the internal detection apparatus of this invention. Explanatory drawing explaining the state which laser-processes to a workpiece in the laser processing apparatus shown in FIG. Explanatory drawing for demonstrating the process trace detection process in this invention. In the internal detection apparatus of this invention, explanatory drawing for demonstrating the state which forms a process trace and implements a planarization process after implementing a process trace detection process.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of a workpiece internal detection method and an internal detection device according to the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 shows an overall perspective view of a laser processing apparatus 40 configured to be equipped with an internal detection device for detecting the inside of a workpiece according to the present invention and for performing laser processing on the workpiece. The figure is shown. A laser processing apparatus 40 shown in the figure includes a base 41, a holding mechanism 42 for holding the workpiece, a moving means 43 for moving the holding mechanism 42, and a laser beam on the workpiece held by the holding mechanism 42. A laser beam irradiation means 44 for irradiating, a display means 45, an imaging means 50, and control means (not shown) constituted by a computer are provided, and each means is controlled by the control means.

  The holding mechanism 42 includes a rectangular X-direction movable plate 61 mounted on the base 41 so as to be movable in the X direction, and a rectangular Y-direction movable plate mounted on the X-direction movable plate 61 so as to be movable in the Y direction. 63, a cylindrical column 60 fixed to the upper surface of the Y-direction movable plate 63, and a rectangular cover plate 62 fixed to the upper end of the column 60. The cover plate 62 is formed with a long hole 62a extending in the Y direction. A circular suction chuck 66 made of a porous material and extending substantially horizontally is formed on the upper surface of the chuck table 64 as a holding means for holding a circular workpiece extending upward through the elongated hole 62a. Has been placed. The suction chuck 66 is connected to suction means (not shown) by a flow path passing through the support column 60. A plurality of clamps 68 are arranged on the periphery of the chuck table 64 at intervals in the circumferential direction. Note that the X direction is a direction indicated by an arrow X in FIG. 1, and the Y direction is a direction indicated by an arrow Y in FIG. 1 and is a direction orthogonal to the X direction. The plane defined by the X direction and the Y direction is substantially horizontal.

  The moving means 43 includes an X direction moving means 70, a Y direction moving means 72, and a rotating means (not shown). The X direction moving means 70 includes a ball screw 74 extending in the X direction on the base 41 and a motor 76 connected to one end of the ball screw 74. A nut portion (not shown) of the ball screw 74 is fixed to the lower surface of the X-direction movable plate 61. Then, the X-direction moving means 70 converts the rotational motion of the motor 76 into a linear motion by the ball screw 74 and transmits it to the X-direction movable plate 61, and moves the X-direction movable plate 61 along the guide rail 43 a on the base 41. Advance and retreat in the X direction. The Y direction moving means 72 has a ball screw 78 extending in the Y direction on the X direction movable plate 61 and a motor 80 connected to one end of the ball screw 78. A nut portion (not shown) of the ball screw 78 is fixed to the lower surface of the Y-direction movable plate 63. Then, the Y-direction moving means 72 converts the rotational motion of the motor 80 into a linear motion by the ball screw 78, transmits it to the Y-direction movable plate 63, and moves in the Y-direction along the guide rail 61a on the X-direction movable plate 61. The plate 63 is moved back and forth in the Y direction. The rotating means is built in the support column 60 and rotates the suction chuck 66 with respect to the support column 60.

  The imaging means 50 is attached to the lower surface of the front end of the frame body 82, is located above the guide rail 43a, and is to be processed placed on the chuck table 64 by moving the chuck table 64 along the guide rail 43a. An object can be imaged, and a display means 45 is mounted on the top surface of the front end of the frame 82 so that an image picked up by the image pickup means 50 can be displayed via the control means. In the illustrated embodiment, the imaging unit 50 includes an infrared light source 52 for irradiating the workpiece with infrared rays, as shown in FIG. Infrared illuminating means composed of an optical fiber 521 for guiding an infrared ray from the infrared light source 52 to the optical system 54, and an infrared imaging device for outputting an electrical signal corresponding to the infrared ray captured by the optical system 54 ( The imaging unit 56 is provided with an infrared CCD, and the captured image signal is sent to a control means described later. A reflecting mirror unit 58 configured to be detachable from the optical system 54 can be disposed at the lower end of the optical system 54, and the reflecting mirror unit 58 is fitted to the tip of the optical system 54. An annular ring portion 581 to be combined, an arm portion 582 extending downward from the ring portion 581, and a reflecting mirror 583 extending from the tip of the arm portion 582 to the inner lower side with an inclination angle of 45 °. Is provided. The reflector unit 58 is attached to the optical system 54 by positioning the ring portion 581 of the reflector unit 58 at the distal end portion of the optical system 54 and the distal end portion of the fixing screw 584 in a recess 54 a formed at the distal end portion of the optical system 54. This is done by entering and fixing. As will be described in detail later, the reflecting mirror 583 is positioned at a position facing the side surface of the workpiece held on the chuck table 64, and reflects the infrared rays irradiated from the infrared light source 52 on the side surface. The inclination is set so that the infrared rays from the side surface of the workpiece reflected by the irradiated area are guided to the imaging unit 56 including the infrared imaging device while irradiating the workpiece. Note that the infrared rays emitted from the infrared light source 52 do not necessarily have to be reflected by the reflecting mirror 583 and can be appropriately changed according to the location and image to be imaged. The workpiece internal detection device according to the present embodiment is thus configured by the imaging unit 50 used in the alignment process at the time of laser processing, and the reflecting mirror unit 58 configured to be attached to the imaging unit 50. Yes.

Referring back to FIG. 1, the laser beam irradiation means 44 is built in a frame 82 that extends upward from the upper surface of the base 41 and then extends substantially horizontally, and is transmissive to the workpiece, for example, 1340 nm. A laser beam whose output is appropriately adjusted at a wavelength of is irradiated toward a workpiece placed on the chuck table 64 through a condenser 44a disposed on the lower surface of the front end of the frame body 82, and the inside thereof is irradiated. The modified layer is formed.
The laser processing apparatus 40 in the present embodiment includes a control unit (not shown). The control unit is configured by a computer and stores a central processing unit (CPU) that performs arithmetic processing according to a control program, a control program, and the like. A read-only memory (ROM), a read / write random access memory (RAM) for temporarily storing detected values, calculation results, and the like, an input interface, and an output interface are provided. In addition to the image signal from the image pickup means 50, a signal from a position detection means (not shown) of the holding mechanism 42 in the X and Y directions is input to the input interface of the control means. Further, an operation signal is transmitted from the output interface toward the laser beam oscillator 44, the infrared light source 52, the X direction moving means 70, the Y direction moving means 72, and the like.

  The internal detection apparatus for executing the internal detection method of the workpiece carried out according to the present invention is configured as described above, and its operation will be described below.

  FIG. 3 shows a disk-shaped silicon wafer 10 whose inside is detected by the internal detection device of the present invention. In addition, although this silicon wafer 10 is irradiated with a laser beam by the laser processing apparatus 40 shown in FIG. 1 and a modified layer is formed therein, in this embodiment, no device is formed on the surface. A test silicon wafer 10 is employed.

  When detecting the processing trace formed inside by irradiating the laser beam to the silicon wafer 10 by the internal detection device of the present invention, first, the end portion of the silicon wafer 10 is first cut in advance as shown in FIG. Thus, a flattening step is performed in which the divided silicon wafers 10a and 10a ′ are divided and the flat portions 12 are formed on the side surfaces of the new silicon wafer 10a. The flattening step can be performed using a dicing apparatus that cuts the end portion of the silicon wafer 10 with a rotating cutting blade, and a silicon wafer 10a in which the flat portion 12 is formed is obtained. Further, the silicon wafer 10 before being divided or the silicon wafer 10a after being divided is positioned at the opening of the annular frame F and attached to the adhesive tape T, and the outer peripheral portion of the adhesive tape T is attached to the annular frame F. (See FIG. 3).

  The adhesive tape T side of the silicon wafer 10 a described above is placed on the chuck table 64 of the laser processing apparatus 40 shown in FIG. 1, and the annular frame F is fixed by a clamp 68 provided on the chuck table 64. Then, by operating a suction means (not shown), the silicon wafer 10a is suction fixed on the suction chuck 66 (holding step).

  When the holding step is performed, the X-direction moving means 70 is operated, the suction chuck 66 that sucks and holds the silicon wafer 10a is positioned immediately below the imaging means 50, and the silicon wafer 10a is controlled by the imaging means 50 and a control means (not shown). An alignment step for detecting a processing region to be laser processed is executed. The laser processing executed in the present embodiment is for detecting the inside by changing the irradiation condition of the laser beam, and irradiates the laser beam LB along the flat portion 12 as shown in FIG. Then, a processing mark made of one modified layer 100 is formed. Therefore, the alignment step is to align the position of the condenser 44a of the laser beam irradiation means 44 with the flat portion 12, and at a position away from the flat portion 12 by a predetermined distance (for example, 30 μm). Alignment is performed so that the laser beam from the condenser 44a is irradiated along the flat portion 12. When the alignment process is performed as described above, the chuck table 64 is moved to the laser beam irradiation region where the condenser 44a of the laser beam irradiation means 44 is located.

  The laser beam oscillating means 44 is operated so that the condensing point of the pulse laser beam irradiated from the condenser 44a is positioned so as to be a predetermined height inside the silicon wafer 10a, and from the condenser 44a to the silicon wafer 10a. The suction chuck 66 constituting the chuck table 64 is moved at a predetermined moving speed in the direction indicated by the arrow X in FIG. 4A while irradiating a pulse laser beam having a wavelength having transparency. By carrying out laser processing in this way, as shown in FIG. 4B as an enlarged cross-sectional view of the main part, along the flat part 12 of the test silicon wafer 10a, one line of modification is provided. A quality layer 100 is formed.

In addition, the laser processing which forms said modified layer is performed on the following processing conditions, for example.
Wavelength: 1342nm
Repetition frequency: 90 kHz
Average output: 1.0-2.0W
Spot diameter: φ2μm
Processing feed rate: 700 mm / sec

  When the processing trace made of the modified layer 100 is formed on the silicon wafer 10a, the reflecting mirror unit 58 is attached and fixed to the tip of the optical system 54 of the imaging means 50 as shown in FIG. When the reflecting mirror unit 58 is mounted and fixed, the chuck table 64 is moved by operating the X direction moving means 70 and the Y direction moving means 72, and the vertical position of the imaging means 50 is adjusted as appropriate, so that FIG. As shown in FIG. 5B, the reflecting mirror 583 of the reflecting mirror unit 58 is positioned at a position facing the side surface where the flat portion 12 of the silicon wafer 10a is formed (reflecting mirror positioning step).

  When the reflecting mirror positioning step is performed, the infrared light source 52 is operated to guide infrared light to the optical system 54 via the optical fiber 521. As is apparent from the schematic cross-sectional view shown in FIG. 5B, the infrared light guided to the optical system 54 via the optical fiber 521 is reflected by the half mirror 541 and guided to the reflecting mirror 583 via the condenser lens 542. The infrared light reflected by the reflecting mirror 583 is configured to be irradiated to the flat portion 12 of the silicon wafer 10a. The infrared rays applied to the flat portion 12 are light having a wavelength that passes through the silicon wafer 10a, and pass through the silicon wafer 10a to illuminate the modified layer 100 formed inside (illumination process).

  Infrared light that illuminates the inside of the silicon wafer 10a is reflected by a processing mark formed by the modified layer 100, passes through the inside of the silicon wafer 10a, and passes through the flat portion 12 formed on the side surface to reflect the reflector 583. Is incident on. The incident reflected light passes through the condenser lens 542 and the half mirror 541 of the optical system 54, is guided to the imaging unit 56 having an infrared imaging device, and is input to a control unit (not shown), and the random access memory ( (RAM) and displayed on the display means 45 (processing mark detection step).

  By performing the above-described processing mark detection step, it is possible to detect the processing marks formed inside the silicon wafer 10a without actually dividing the silicon wafer 10a. That is, by observing the dimension in the thickness direction and the shape of the modified layer 100 formed on the silicon wafer 10a from the image displayed on the display means 45, the irradiation condition of the laser beam when the laser processing is executed. Can influence the formation of the modified layer.

  In the present embodiment, the above-described recon wafer 10a is irradiated with a laser beam to form a single modified layer 100, and after performing the above-described processing mark detection step (see FIG. 6A), again. A planarization process is performed. That is, it is possible to form a new silicon wafer for internal detection by cutting the region where the detected modified layer is formed. More specifically, as shown in FIG. 6B, the silicon wafer 10a that has been subjected to the processing mark detection step is placed on a holding means of a cutting device 30 that is separately prepared, and the silicon wafer 10a is placed along the flat portion 12. The region including the modified layer 100 is cut, and the silicon wafer 10a is divided into a new silicon wafer 10b and a 10b ′ including the already detected modified layer 100. Then, the divided 10b ′ is cut off to obtain a silicon wafer 10b having a new flat portion 12 ′ (see FIG. 6C). The silicon wafer 10b thus obtained is again placed on the laser processing apparatus 40 shown in FIG. 1, the laser processing conditions are changed, and a new modified layer is formed along the flat portion 12 ′. A processing mark detection step for detecting the new modified layer is executed. By repeating these operations, a single silicon wafer 10 can be used to change the processing conditions to form a large number of processing marks, and each can be observed. Moreover, in this embodiment, since the internal detection apparatus of a to-be-processed object can be comprised as it is only by attaching the reflective mirror unit 58 with respect to the imaging means 50 of the laser processing apparatus 40, the process which forms a modification layer Subsequent to this, it is not necessary to remove the workpiece from the holding means, and it is possible to execute the machining mark detection step as it is.

  The workpiece internal detection device and the workpiece internal detection method configured according to the present invention are not limited to the above-described embodiments, and various modifications can be made. For example, in the above-described embodiment, an example in which a silicon wafer is employed as a workpiece and an infrared light source is used has been described. However, the present invention is not limited thereto, and light having a wavelength having transparency can be set as the light source. Any object can be used as long as it is a workpiece. For example, when a sapphire substrate or a lithium tantalate (LT) substrate is employed as a workpiece, a light source that emits visible light can be employed as a light source of light that is emitted to detect the inside.

  In the above-described embodiment, the workpiece is held by the holding means, and after the workpiece is held by the holding means, the modified layer is formed inside by performing laser processing, and the modified layer is detected as it is. Although the trace detection step is performed, the present invention is not limited to this. Before holding the workpiece on the holding means for performing the trace detection step, the modified layer is subjected to laser processing in advance. Then, a processing mark detection step of detecting the inside by holding the workpiece on the holding means may be performed.

  In the above-described embodiment, in the laser processing apparatus, the reflecting mirror unit is attached to the alignment imaging means used in the alignment process performed when laser processing is performed, and the internal detection apparatus for the workpiece is configured. The present invention is not limited to this, and the internal detection device for the workpiece can be configured as a device independent of the laser processing device.

  In the above-described embodiment, after performing laser processing to form a single modified layer, a processing trace detection step of detecting the inside of the workpiece held by the holding means is performed, and then a new flat portion The example of repeating the flattening step for forming the surface, forming the modified layer again, and performing the processing mark detection step for detecting the newly formed modified layer has been shown. When forming the modified layer in the inside, a plurality of modified layers are formed at a predetermined interval while changing the laser processing conditions little by little, and the single modified layer closest to the flat part is formed. After performing the processing mark detection step, a new flat portion is formed by a flattening step of cutting and removing only the region where the single modified layer close to the flat portion is formed, and is closest to the new flat portion. To carry out a processing mark detection step of detecting another modified layer. It may be returned Ri. Thereby, it is not necessary to separately perform laser processing between the processing mark detection step and the flattening step, and the processing mark detection efficiency is improved.

  In the above-described embodiment, the example in which the dicing apparatus is used as the means for performing the flattening process for forming the flat portion on the side surface of the workpiece to be observed has been described. For example, a laser processing apparatus that divides a workpiece by laser processing may be employed.

10: Silicon wafer 12, 12 ': Flat part 30: Cutting device 40: Laser processing device 42: Holding mechanism 43: Moving means 44: Laser beam irradiation means 44a: Condenser 45: Display means 50: Imaging means 52: Infrared light source 54: Optical system 56: Imaging unit 58 including an infrared imaging device 58: Reflecting mirror unit 581: Ring unit 582: Arm unit 583: Reflecting mirror

Claims (3)

An internal detection device for a workpiece that detects a processing mark formed inside by irradiating the workpiece with a laser beam,
Holding means for holding the workpiece, illumination means for irradiating the workpiece with light having a wavelength that is transmissive to the workpiece, and imaging means for imaging the workpiece A reflecting mirror disposed opposite to the side surface of the workpiece and reflecting light from the side surface to guide the imaging means;
An internal detection device for a workpiece comprising at least a workpiece. An internal detection method for a workpiece that detects a processing mark formed inside by irradiating the workpiece with a laser beam,
A holding step of holding the workpiece on the holding means;
An illumination step of irradiating the workpiece with light having a wavelength that is transparent to the workpiece;
A reflecting mirror positioning step for positioning a reflecting mirror facing the side surface of the workpiece held by the holding means and reflecting the light from the side surface to the imaging means;
A processing mark detection step of capturing an image of a side surface of the workpiece with the imaging means and detecting the processing mark formed inside the workpiece;
A method for detecting the inside of a workpiece including   3. A flattening step of forming a flat portion for detecting the processing mark on the side surface before or after forming the processing mark in the workpiece. The internal detection method of the workpiece as described in 2.