JP7257604B2 - LASER PROCESSING DEVICE AND CONTROL METHOD THEREOF - Google Patents

Description

The present invention relates to a laser processing apparatus for forming a modified region inside a wafer along a dividing line of the wafer by irradiating laser light with a focal point aligned with the inside of the wafer, and a control method thereof.

A laser processing is known in which a laser beam is irradiated with a focused point on the inside of a wafer having a plurality of devices formed on the surface thereof to form a modified region inside the wafer along the dividing line of the wafer. (See Patent Document 1). Then, the laser-processed wafer is divided into individual chips with the modified region as a starting point by application of external stress.

A laser processing apparatus that performs such laser processing includes a laser unit (also referred to as a laser head) that irradiates a laser beam onto one surface of a wafer, and an infrared microscope that is fixed to the laser unit and photographs the surface of the wafer. There is known one provided (see Patent Literature 2). In this laser processing apparatus, before the modified region is formed, the alignment reference of the wafer is photographed with an infrared microscope, and the position of the planned division line of the wafer (the position of the planned division line with respect to the infrared microscope) is determined based on the photographed image obtained by this photographing. Alignment detection for detecting the relative position) is performed.

Then, based on the position detection result of the planned division line and known positional relationship information between the optical axis of the laser unit and the optical axis of the infrared microscope, alignment is performed to align the optical axis of the laser unit with one end of the planned division line. . Then, a modified region is formed inside the wafer along the division line by irradiating the laser light from the laser unit toward the focal point inside the wafer and moving the laser unit and the wafer relative to each other. Thereafter, the above-described alignment and formation of modified regions are repeatedly performed for each line to be divided.

Patent Literature 3 describes a laser processing apparatus that obtains a positional deviation between a target value (theoretical value) and an actual measurement value of the irradiation position of a laser beam irradiated onto a wafer from a laser unit. This laser processing apparatus includes a sample mounting stage separate from a wafer stage that holds a wafer. After the processed sample piece is mounted on the sample mounting stage, the surface of the processed sample piece is irradiated with laser light from the laser unit to form a laser processing trace. Next, the laser processing trace is photographed by the observation optical unit, and the positional deviation between the target value and the actual measurement value of the irradiation position of the laser beam is detected based on the photographed image obtained by this photographing.

JP 2016-107334 A JP 2016-21519 A JP 2014-111426 A

By the way, in the laser processing apparatus described in Patent Document 2, the optical axis of the laser unit changes due to changes in the environment such as the room temperature of the factory (clean room) where the apparatus is installed, or due to changes in the environment over time. and the optical axis of the infrared microscope may shift. In this case, the processing position of the laser beam by the laser unit is displaced with respect to the line to be divided, so that high-precision processing cannot be performed. For this reason, conventionally, countermeasures such as correcting misalignment have been implemented through periodic maintenance, but depending on the factory, there is a risk of misalignment occurring in a short period of time due to large temperature changes.

In order to prevent such positional deviation, it is desirable to correct the processing position of the laser beam when forming the modified region. Become. In this case, a plurality of meandering modified regions and cracks overlap, making it difficult to correct the processing position of the laser beam. If a correction deviation of several μm occurs, for example, in a narrow street process in which the width of the line to be divided is 20 μm or less, the yield is greatly reduced.

Therefore, in the laser processing apparatus described in Patent Document 2 as well, as described in Patent Document 3, the positional deviation between the target value and the actual measurement value of the irradiation position of the laser light irradiated onto the wafer from the laser unit is detected. By doing so, it is conceivable to acquire the positional relationship between the optical axis of the laser unit and the optical axis of the infrared microscope.

However, the method described in Patent Document 3 is intended for a laser processing apparatus in which the optical axis of the laser unit and the optical axis of the infrared microscope are aligned. It cannot be simply applied to the described laser processing apparatus. Moreover, even if it is possible to apply this method, there is a problem that it takes time and cost to prepare the processed sample piece and to attach and detach the processed sample piece to and from the sample mounting stage.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a laser processing apparatus and a method of controlling the laser processing apparatus, which can easily perform laser processing of a wafer with high precision.

A laser processing apparatus for achieving the object of the present invention forms a modified region inside the wafer along the dividing line of the wafer by irradiating laser light with a focal point aligned with the inside of the wafer. A laser processing apparatus having a laser optical system that irradiates a laser beam toward one surface of a wafer and a second optical axis that is arranged at a position facing the one surface and is different from the first optical axis of the laser optical system, , a relative movement mechanism that integrally moves the laser optical system and the infrared camera relative to the wafer, and an infrared camera that photographs the alignment reference of the wafer. 1 Based on the photographed image, a detection control unit for detecting the position of the line to be divided and a relative movement mechanism are driven to move the wafer relative to the laser optical system, and the laser optical system By driving the thermally processed layer formation control unit that condenses the system laser beam to form a thermally processed layer on one surface, and the relative movement mechanism, the infrared camera is relatively moved to the photographing position of the thermally processed layer, and the infrared camera Formation of a thermally processed layer within one surface based on a photographing control unit that causes a second photographed image of the thermally processed layer to be photographed, the second photographed image, and known positional relationship information between the first optical axis and the second optical axis. A computing unit that computes a positional deviation between a theoretical position value and an actually measured value, and a correcting unit that corrects the positional relationship information based on the computation result of the computing unit.

According to this laser processing apparatus, even if the relative position between the first optical axis of the laser optical system and the second optical axis of the infrared camera deviates from the design value due to changes in the environment, etc., the first optical axis of the laser optical system The positional relationship information between the first optical axis and the second optical axis of the infrared camera can be corrected.

In the laser processing apparatus according to another aspect of the present invention, in a state in which the laser beam of the laser optical system is focused on the inside of the wafer, the position detection result of the line to be divided by the detection control unit and the position corrected by the correction unit Based on the positional relationship information, the relative movement mechanism moves the laser optical system relative to the wafer along the planned division line to form a modified region inside the wafer along the planned division line. A formation controller is provided. As a result, the modified region can be formed inside the wafer with high precision along the dividing line.

In the laser processing apparatus according to another aspect of the present invention, the detection control unit drives the relative movement mechanism to relatively move the infrared camera to the imaging position of the alignment reference, causes the infrared camera to photograph the alignment reference, and 1 Acquire a captured image. Thereby, the position of the planned division line can be detected.

In the laser processing apparatus according to another aspect of the present invention, the detection control unit determines the position of the planned division line and the predetermined position to form the thermally processed layer within the invalid area of the wafer based on the first captured image. The thermally processed layer formation control unit controls the relative movement mechanism and the laser optical system based on the positional relationship information and the detection result of the planned formation position by the detection control unit to form a thermally processed layer at the planned formation position. do. Thereby, a thermal processing layer can be formed in the invalid area of the wafer.

In the laser processing apparatus according to another aspect of the present invention, the planned formation position is the end of the planned division line.

In the laser processing apparatus according to another aspect of the present invention, at least the thermal processing layer formation control unit, the imaging control unit, the calculation unit, and the correction unit are repeated for each direction of the dividing line, for each wafer, or for each of a plurality of wafers. Equipped with a repeat control unit to operate. Thereby, the positional relationship information can be corrected at a predetermined timing.

A method of controlling a laser processing apparatus for achieving the object of the present invention includes a laser optical system that irradiates a laser beam toward one surface of a wafer, and a first optical axis of the laser optical system arranged at a position facing the one surface of the wafer. An infrared camera that has a second optical axis different from the wafer, and a relative movement mechanism that integrally moves the laser optical system and the infrared camera relative to the wafer. In a control method of a laser processing apparatus for forming a modified region inside a wafer along a planned division line of the wafer by irradiating the laser beam with the focal point aligned with the laser beam, the infrared camera is caused to photograph the alignment reference of the wafer. a detection step of detecting the position of the line to be divided based on the first photographed image of the alignment reference photographed by the infrared camera; , a thermally processed layer forming step in which a thermally processed layer is formed on one surface by condensing the laser beam of the laser optical system, and the infrared camera is moved to the photographing position of the thermally processed layer by the relative movement mechanism, and the thermal processing is performed by the infrared camera. Thermal processing within one surface based on a photographing step of photographing a second photographed image of the layer, the second photographed image photographed in the photographing step, and known positional relationship information of the first optical axis and the second optical axis. The method includes a calculation step of calculating the positional deviation between the theoretical value and the measured value of the layer formation position, and a correction step of correcting the positional relationship information based on the calculation result in the calculation step.

In a method for controlling a laser processing apparatus according to another aspect of the present invention, in a state in which the laser beam of the laser optical system is focused on the inside of the wafer, the position detection result of the line to be divided in the detection step and the correction step are performed. Based on the positional relationship information corrected in , the relative movement mechanism moves the laser optical system relative to the wafer along the planned dividing line to form a modified region inside the wafer along the planned dividing line. It has a modified region forming step.

INDUSTRIAL APPLICABILITY The present invention can easily perform laser processing of a wafer with high precision.

1 is a schematic diagram of a laser processing apparatus; FIG. 1 is a plan view of a wafer to be processed by a laser processing apparatus; FIG. 3 is a cross-sectional view of a portion of the wafer shown in FIG. 2; FIG. It is a functional block diagram of a control device. FIG. 4 is an explanatory diagram for explaining formation of a modified region inside a wafer; FIG. 4 is an explanatory diagram for explaining formation of a modified region inside a wafer; FIG. 4 is an explanatory diagram for explaining the formation of two layers of modified regions inside the wafer; FIG. 4 is an explanatory diagram for explaining the formation of two layers of modified regions inside the wafer; FIG. 5 is an explanatory diagram for explaining formation of a thermally processed layer by a thermally processed layer formation control unit; FIG. 5 is an explanatory diagram for explaining formation of a thermally processed layer by a thermally processed layer formation control unit; FIG. 10 is an explanatory diagram for explaining the calculation of the positional deviation between the theoretical value and the actual measurement value of the formation position of the thermally processed layer on the back surface of the wafer by the calculation unit; FIG. 5 is an explanatory diagram for explaining correction of positional relationship information by a correction unit; 4 is a flow chart showing the flow of laser processing of a wafer by the laser processing apparatus having the above-described configuration, particularly correction processing of positional relationship information corresponding to the control method of the laser processing apparatus of the present invention. It is an explanatory view for explaining a modification of a processing unit.

[Configuration of laser processing device]
FIG. 1 is a schematic diagram of a laser processing apparatus 10. As shown in FIG. As shown in FIG. 1, the laser processing apparatus 10 performs laser processing on the wafer 12 as a pre-process before dividing the wafer 12 (eg, silicon wafer) into a plurality of chips 14 (see FIG. 2). The XYZ directions in the drawing are orthogonal to each other, of which the X and Y directions are horizontal, and the Z direction is vertical. The θ direction is the direction of rotation with the Z direction as the axis of rotation.

FIG. 2 is a plan view of a wafer 12 to be processed by the laser processing apparatus 10. FIG. FIG. 3 is a cross-sectional view of a portion of wafer 12 shown in FIG. As shown in FIGS. 2 and 3, the wafer 12 is partitioned into a plurality of regions by a plurality of streets arranged in a grid. A device layer 16 forming a chip T is provided in each of these partitioned regions. The laser processing apparatus 10 forms a modified region 200 (see FIG. 6) inside the wafer 12 along a plurality of dividing lines C1 and C2 set on streets. Note that the line to be divided C1 and the line to be divided C2 are orthogonal to each other.

Returning to FIG. 1 , the laser processing apparatus 10 includes an Xθ stage 20 , a processing unit 22 and a control device 24 .

The Xθ stage 20 sucks and holds the surface of the wafer 12 on which the device layer 16 is provided via a protective tape (not shown). As a result, the wafer 12 is held on the Xθ stage 20 so that the back surface, which is opposite to the front surface, faces a processing unit 22 which will be described later. Therefore, the back surface of the wafer 12 corresponds to one surface of the present invention.

The Xθ stage 20 is moved in the X direction and rotated in the θ direction by a stage drive mechanism 26 (see FIG. 4) under the control of a controller 24, which will be described later. Note that the stage drive mechanism 26 has a configuration in which a known linear motion mechanism and a rotation mechanism are combined. The moving direction M1 is the moving direction of the Xθ stage 20 toward one side of the X direction, and the moving direction M2 is the moving direction of the Xθ stage 20 toward the other side of the X direction.

The processing unit 22 has a laser unit 28 and an infrared microscope 30 . The processing unit 22 is arranged above the Xθ stage 20 in the Z direction, and is controlled by a control device 24 which will be described later.

Also, the processing unit 22 is moved in the Y and Z directions by a unit drive mechanism 32 (see FIG. 4) under the control of a control device 24, which will be described later. The unit drive mechanism 32 constitutes the relative movement mechanism of the present invention together with the stage drive mechanism 26 described above, and a known linear motion mechanism is used.

The laser unit 28 corresponds to the laser optical system of the present invention, and irradiates the laser light L toward the back surface of the wafer 12 . Laser unit 28 includes laser light source 40, beam expander 42, mirror 44, λ/2 waveplate 46, spatial light modulator 48, mirror 50, mirror 52, lens 54, mirror 56, mirror 58, lens 60, and collector. An optical lens 62 is provided. The configuration of the laser unit 28 is not limited to the configuration shown in FIG. 1, and various head configurations used for laser processing of the wafer 12 may be employed.

The laser light source 40 emits laser light L for laser processing of the wafer 12 toward the beam expander 42 . Since the type of laser light L is known technology (see, for example, Patent Document 1), a specific description is omitted here.

The beam expander 42 expands the laser light L incident from the laser light source 40 to an appropriate beam diameter for phase modulation by a spatial light modulator 48, which will be described later. The laser light L emitted from the beam expander 42 passes through the mirror 44 and the λ/2 wavelength plate 46 and enters the spatial light modulator 48 .

For the spatial light modulator 48, for example, a reflective liquid crystal (LCOS: Liquid Crystal on Silicon) spatial light modulator (SLM: Spatial Light Modulator) is used. This spatial light modulator 48 modulates the laser light L incident from the λ/2 wavelength plate 46 by presenting a predetermined hologram pattern under the control of the control device 24 . As a result, the laser light L is aberration-corrected so that the aberration of the laser light L condensed inside the wafer 12 is less than or equal to a predetermined aberration. Since the configuration and function of the spatial light modulator 48 are well-known technology (see Patent Document 1 above), a detailed description thereof will be omitted here.

The laser light L modulated by the spatial light modulator 48 passes through mirrors 50 , 52 , 54 , 56 , 58 and 60 and is condensed by a condensing lens 62 . The position of the condenser lens 62 is adjusted in the Z direction by a lens moving mechanism (not shown). This lens moving mechanism adjusts the Z-direction position of the focal point of the laser light L (wafer depth direction position) by adjusting the Z-direction position of the condenser lens 62 under the control of the control device 24. . The optical axis A1 of the condenser lens 62 (laser unit 28) corresponds to the first optical axis of the invention.

The infrared microscope 30 is fixed to the laser unit 28 and moves together with the laser unit 28 . The infrared microscope 30 includes an illumination light source 64, a half mirror 66, an objective lens 68, an infrared camera 70, and the like.

As the illumination light source 64, for example, an LD (Laser Diode) light source, an SLD (Super Luminescent Diode) light source, or the like is used. The illumination light source 64 outputs illumination light in a wavelength range that passes through the wafer 12 , for example, infrared light in the infrared range toward the half mirror 66 .

The half mirror 66 transmits part of the illumination light incident from the illumination light source 64 and emits it toward the objective lens 68 . Thereby, the illumination light is condensed on the back surface of the wafer 12 by the objective lens 68 . The Z-direction position (wafer depth direction position) of the focal point of the illumination light condensed by the objective lens 68 is adjusted by moving the objective lens 68 in the Z-direction by a lens moving mechanism (not shown). The optical axis A2 of the objective lens 68 is the illumination axis of the illumination light source 64 and the photographing optical axis of the infrared camera 70, which will be described later, and corresponds to the second optical axis of the present invention. Both the optical axes A1 and A2 are parallel to the Z direction.

Part of the reflected light of the illumination light reflected by the wafer 12 is reflected toward the infrared camera 70 by the half mirror 66 .

The infrared camera 70 has an imaging device (not shown) that is sensitive to the wavelength region of infrared light. The state inside the wafer 12 can be confirmed based on the photographed image of the wafer 12 photographed by the infrared camera 70 with the focal point of the objective lens 68 aligned with the inside of the wafer 12 . In addition, the state of the back surface of the wafer 12 can be confirmed based on the captured image of the wafer 12 captured by the infrared camera 70 with the objective lens 68 focused on the back surface of the wafer 12 .

Image data of the captured image captured by the infrared camera 70 is output to the control device 24 . The control device 24 causes the monitor 72 to display the photographed image of the inside or the rear surface of the wafer 12 based on the image data of the photographed image input from the infrared camera 70 .

As the infrared camera 70, a camera (near-infrared camera) having high sensitivity in the near-infrared region (wavelength region of 1 μm or more) typified by, for example, an InGaAs (indium gallium arsenide) camera is preferably used.

The optical axis A2 of the infrared camera 70 is located downstream of the position of the optical axis A1 of the laser unit 28 described above in the moving direction M1 (one direction in the X direction) of the wafer 12 during laser processing. Thereby, the infrared camera 70 can photograph the wafer 12 on the dividing lines C<b>1 and C<b>2 which are the same as the processing position of the wafer 12 by the laser light L of the laser unit 28 .

[Configuration of control device]
FIG. 4 is a functional block diagram of the control device 24. As shown in FIG. As shown in FIG. 4, the control device 24 includes a stage drive mechanism 26, a laser unit 28 (laser light source 40 and spatial light modulator 48), an infrared microscope 30 (illumination light source 64 and infrared camera 70), and a unit The driving mechanism 32, the monitor 72, and the operating section 74 are connected. A known keyboard, mouse, operation buttons, and the like are used for the operation unit 74 .

The control device 24 is composed of an arithmetic device such as a personal computer, and has an arithmetic circuit composed of various processors, memories, and the like. Various processors include CPU (Central Processing Unit), GPU (Graphics Processing Unit), ASIC (Application Specific Integrated Circuit), and programmable logic devices [for example, SPLD (Simple Programmable Logic Devices), CPLD (Complex Programmable Logic Device), and FPGAs (Field Programmable Gate Arrays)]. Various functions of the control device 24 may be realized by one processor, or may be realized by a plurality of processors of the same type or different types.

The control device 24 functions as an integrated control section 80, a storage section 82, a movement control section 84, a laser control section 86, a microscope control section 88, and a display control section 90 by executing control programs (not shown). Hereinafter, what is described as "-unit" in the present embodiment may be "-circuit", "-device", or "-device". That is, what is described as "--unit" may consist of firmware, software, hardware, or a combination thereof.

The general control section 80 centrally controls the operation of each section of the laser processing apparatus 10 based on the input operation to the operation section 74 .

The storage unit 82 pre-stores positional relationship information 92 in addition to the control program described above. The positional relationship information 92 is known information indicating the relative positional relationship between the position (XY coordinates) of the optical axis A1 of the laser unit 28 and the position (XY coordinates) of the optical axis A2 of the infrared camera 70 in the XY directions. As the positional relationship information 92, values measured by the manufacturer of the laser processing apparatus 10 are stored. Further, the positional relationship information 92 is corrected (rewritten) by an information correction control section 100 which will be described later.

The movement control unit 84 drives the stage driving mechanism 26 and the unit driving mechanism 32 under the control of the integrated control unit 80, so that the laser unit 28 and the infrared microscope 30 are integrally moved with respect to the wafer 12 in the XYZ directions and θ. Relative movement in the direction. As a result, the optical axis A1 of the laser unit 28 can be aligned with the processing start position of the wafer 12 [an end of an ineffective area 12a (see FIG. 10) to be described later and an end of the planned division lines C1 and C2] before laser processing. At times, the laser unit 28 can be moved relative to the wafer 12 in the X direction. In addition, the optical axis A2 of the infrared microscope 30 can be aligned with a specific position of the wafer 12 [alignment reference, thermally processed layer 120 (see FIG. 10) described later, etc.] before laser processing.

The laser control unit 86 controls emission of the laser light L by the laser light source 40 and modulation of the laser light L by the spatial light modulator 48 under the control of the integrated control unit 80 . Since the modulation control of the laser beam L by the spatial light modulator 48 is a well-known technique, a detailed description thereof will be omitted.

The microscope control unit 88 controls emission of illumination light from the illumination light source 64 and photographing of the wafer 12 by the infrared camera 70 under the control of the integrated control unit 80 .

The display control unit 90 controls display on the monitor 72 . Based on the image data of the photographed image of the wafer 12 input from the infrared camera 70, the display control unit 90 causes the monitor 72 to display the photographed image. The display control unit 90 also causes the monitor 72 to display various setting screens of the laser processing apparatus 10 .

The integrated control unit 80 functions as a detection control unit 96, a modified region formation control unit 98, and an information correction control unit 100 by executing the above-described control program.

The detection control unit 96 controls each unit of the laser processing apparatus 10 to detect the positions (including the orientation within the XY plane) of the division lines C1 and C2 of the wafer 12 held on the Xθ stage 20. Run discovery.

First, the detection control unit 96 controls the stage drive mechanism 26, the unit drive mechanism 32, and the infrared microscope 30 via the movement control unit 84 and the microscope control unit 88 to produce the photographed image 102 of the alignment reference of the wafer 12. Acquire (capture) image data. The alignment reference here is a reference for the laser processing apparatus 10 to recognize the positions of the dividing lines C1 and C2 of the wafer 12. For example, known references such as streets and recognition marks are used. It should be noted that the alignment reference may be provided at any position such as the inside, front surface, or rear surface of the wafer 12 as long as it can be photographed by the infrared camera 70 .

Specifically, when acquiring the image data of the photographed image 102 , the detection control unit 96 drives the stage driving mechanism 26 and the unit driving mechanism 32 to set the infrared camera 70 to a photographing position ( position where the alignment reference is included in the imaging range of the infrared camera 70). After this movement, the detection control section 96 controls the infrared camera 70 so that the infrared camera 70 takes an image of the wafer 12 including the alignment reference. As a result, image data of the photographed image 102 of the wafer 12 is acquired by the infrared camera 70 , and this image data is output from the infrared camera 70 to the detection control section 96 . Note that the captured image 102 corresponds to the first captured image of the present invention.

Based on the image data of the captured image 102, the detection control unit 96 detects the alignment reference in the captured image 102 by a known image recognition method, thereby detecting the positions of the dividing lines C1 and C2 of the wafer 12. .

Further, based on the detection result of the alignment reference, the detection control unit 96 detects a thermal processing layer 120 (see FIG. 10) within the invalid area 12a (see FIG. 10) of the wafer 12 in addition to the positions of the division lines C1 and C2. reference) is detected. The invalid area 12a is an area within the wafer 12 separated from the chips 14 (for example, an outer peripheral area of the wafer 12). In the present embodiment, the end portion of one of the dividing lines C1 and C2 is predetermined as the position where the thermally processed layer 120 is to be formed. Therefore, the detection control unit 96 can detect the formation planned position of the thermally processed layer 120 by detecting the positions of the planned division lines C1 and C2.

The modified region formation control unit 98 controls the stage drive mechanism 26, the unit drive mechanism 32, and the laser unit 28 via the movement control unit 84 and the laser control unit 86, and for each planned division line C1, C2, A modified region 200 (see FIG. 6) is formed inside the wafer 12 along the dividing lines C1 and C2.

Specifically, the modified region formation control unit 98 drives the stage driving mechanism 26 via the movement control unit 84 based on the alignment detection result by the detection control unit 96 to rotate the Xθ stage 20 in the θ direction. , one of the dividing lines C1 and C2 orthogonal to each other (for example, the dividing line C1) is made parallel to the X direction.

Next, the modified region formation control unit 98 starts forming a modified region 200 (see FIG. 6) corresponding to the first planned division line C1 among the plurality of planned division lines C1 parallel to the X direction. . The modified region formation control unit 98 controls the laser unit 28 (optical axis A1) based on the alignment detection result (the position detection result of the line to be divided C1) by the detection control unit 96 and the positional relationship information 92 in the storage unit 82. and the planned division line C1.

Here, in the above-described alignment detection, the relative positional relationship between the infrared camera 70 (optical axis A2) and the planned division lines C1 and C2 is detected. ) and the infrared camera 70 (optical axis A2) are known. Therefore, the modified region formation control unit 98 can determine the relative positional relationship between the laser unit 28 (optical axis A1) and the planned dividing lines C1 and C2 based on the alignment detection result and the positional relationship information 92. .

Therefore, the modified region formation control section 98 drives the stage drive mechanism 26 and the unit drive mechanism 32 via the movement control section 84 based on the alignment detection result and the positional relationship information 92, and the optical axis of the laser unit 28 is shifted. Alignment is performed to align A1 with one end of the first planned division line C1, for example, one end on the moving direction M2 side.

5 and 6 are explanatory diagrams for explaining the formation of the modified region 200 inside the wafer 12. FIG. As shown in FIGS. 5 and 6, the modified region formation controller 98 controls the laser unit 28 after the above-described alignment is completed to focus the laser light L at a predetermined depth position from the back surface of the wafer 12. The light is converged on the light point P1 to form the modified region 200 at the position of the convergence point P1.

Next, the modified region formation controller 98 drives the stage drive mechanism 26 via the movement controller 84 to move the Xθ stage 20 in the movement direction M2. As a result, the laser unit 28 is relatively moved in the movement direction M1 with respect to the wafer 12 while the laser beam L is condensed at the condensing point P1. Unit 28 is moved relative to wafer 12 in the X direction. As a result, a modified region 200 is formed inside the wafer 12 along the first dividing line C1. Further, when the modified region 200 is formed, a crack 202 is generated in the thickness direction (Z direction) of the wafer 12 starting from the modified region 200 .

After forming the modified region 200 corresponding to the first division line C1, the modified region formation control section 98 drives the unit driving mechanism 32 via the movement control section 84 to divide the laser unit 28. It is moved in the Y direction toward the second line to be divided C1 by a distance corresponding to the pitch interval of the line C1. As a result, alignment is performed to align the optical axis A1 of the laser unit 28 with one end of the second planned dividing line C1, for example, one end on the moving direction M1 side.

Then, the modified region formation control section 98 controls the stage drive mechanism 26 and the laser unit 28 via the movement control section 84 and the laser control section 86 to focus the laser light L of the laser unit 28 on the focus point P1. Light and movement of the Xθ stage 20 in the movement direction M1 are executed. As a result, a modified region 200 is formed inside the wafer 12 along the second dividing line C1.

Similarly, the modified regions 200 are formed inside the wafer 12 along all the dividing lines C1. Next, the modified region formation control unit 98 drives the stage drive mechanism 26 via the movement control unit 84 to rotate the Xθ stage 20 by 90°, thereby making the planned division line C2 parallel to the X direction. Then, the modified region formation control unit 98 controls the stage driving mechanism 26 and the laser unit 28 via the movement control unit 84 and the laser control unit 86 in the same manner as the formation of the modified region 200 corresponding to the planned division line C1. Then, the modified regions 200 are formed inside the wafer 12 along all the dividing lines C2. Formation of the modified region 200 is completed as described above.

7 and 8 are explanatory diagrams for explaining the formation of two layers of modified regions 200 inside the wafer 12. FIG. As shown in FIGS. 7 and 8, when the wafer 12 is thick, two layers of modified regions 200 may be formed inside the wafer 12 along the dividing lines C1 and C2. In this case, the modified region formation control unit 98 controls the laser beam of the laser unit 28 after forming the modified region 200 of the first layer described with reference to FIGS. The above-described formation of the modified region 200 is repeated while changing the condensing position of L to the condensing point P2 which is located inside the wafer 12 and shallower than the condensing point P1 (the position on the upper side in the Z direction). Execute. Thereby, the modified region 200 of the second layer is formed. It should be noted that three or more layers of modified regions 200 may be formed according to the thickness of the wafer 12 .

Returning to FIG. 4, the information correction control section 100 corrects the positional relationship information 92 in the storage section 82 .

As described above, the optical axis A1 of the laser unit 28 and the infrared camera may change due to changes in the environment such as the room temperature of the factory (clean room) in which the laser processing apparatus 10 is installed, or changes in the environment over time. 70 may be displaced relative to the optical axis A2. In this case, a deviation occurs between the positional relationship between the optical axes A1 and A2 defined by the positional relationship information 92 and the actual positional relationship between the two. As a result, the optical axis A1 of the laser unit 28 cannot be accurately positioned (aligned) with one end of the planned division lines C1 and C2 based on the initial positional relationship information 92 (at the time of shipment). Therefore, the information correction control unit 100 corrects (updates) the positional relationship information 92 at a predetermined timing.

The information correction control section 100 functions as a thermal processing layer formation control section 110 , an imaging control section 112 , a calculation section 114 and a correction section 116 .

9 and 10 are explanatory diagrams for explaining the formation of the thermally processed layer 120 by the thermally processed layer formation controller 110. FIG. As shown in FIGS. 9 and 10, the thermally processed layer formation control unit 110 controls the stage driving mechanism 26 and the laser unit 28 via the movement control unit 84 and the laser control unit 86 so that the invalid area 12a of the wafer 12 is formed. and at the line end portion (hereinafter simply referred to as the line end portion) which is either end portion of the dividing lines C1 and C2.

First, the thermally processed layer formation control unit 110 performs movement control based on the position detection result of the formation planned position (line end) of the thermally processed layer 120 by the detection control unit 96 and the positional relationship information 92 in the storage unit 82. The stage driving mechanism 26 and the unit driving mechanism 32 are driven via the section 84 to perform alignment for aligning the optical axis A1 of the laser unit 28 with the line end. Here, the optical axis A1 of the laser unit 28 is aligned with, for example, one end in the X direction (for example, the end on the moving direction M2 side) within the line end.

Then, the thermally processed layer formation controller 110 controls the laser unit 28 to converge the laser light L on the converging point P3 on the back surface of the wafer 12 after the above alignment is completed. As a result, the energy of the laser light L is concentrated at the condensing point P3, and the rear surface of the wafer 12 is ablated at the condensing point P3 to form the thermally processed layer 120. FIG.

Next, the thermally processed layer formation controller 110 drives the stage drive mechanism 26 via the movement controller 84 to move the Xθ stage 20 by a predetermined distance in the movement direction M2. As a result, the laser unit 28 is relatively moved in the movement direction M1 with respect to the wafer 12 while the laser beam L of the laser unit 28 is focused at the focal point P3. is relatively moved in the X direction. As a result, a thermally processed layer 120 extending in the X direction along the line ends is formed on the back surface of the wafer 12 . In this embodiment, the moving distance of the Xθ stage 20 is adjusted so that the length of the thermally processed layer 120 in the X direction is, for example, 5 mm. The moving distance is not particularly limited as long as the thermally processed layer 120 is within the invalid area 12a, that is, the distance does not affect the quality of the chip .

The imaging control unit 112 controls imaging of the thermally processed layer 120 by the infrared microscope 30 (infrared camera 70). The imaging control unit 112 drives the stage driving mechanism 26 and the unit driving mechanism 32 via the movement control unit 84 based on the position detection result of the formation planned position (line end) of the thermal processing layer 120 by the detection control unit 96 . Then, the infrared microscope 30 is moved relative to the wafer 12 to the photographing position of the thermal processing layer 120 . Next, the photographing control unit 112 causes the infrared camera 70 of the infrared microscope 30 to photograph the thermally processed layer 120 . As a result, the infrared camera 70 acquires the image data of the photographed image 122 (see FIG. 4) of the heat-processed layer 120 , and this image data is output from the infrared camera 70 to the calculation unit 114 . Note that the captured image 122 corresponds to the second captured image of the present invention.

FIG. 11 is an explanatory diagram for explaining the calculation of the positional deviation between the theoretical value and the actually measured value of the formation position of the thermally processed layer 120 on the back surface of the wafer 12 by the calculation unit 114 . As shown in FIG. 11, the calculation unit 114 detects the thermally processed layer 120 (indicated by diagonal lines) in the captured image 122 based on the image data of the captured image 122 by a known image recognition method. Based on the position of the thermally processed layer 120 in the captured image 122 and the position of the optical axis A2 of the infrared camera 70 when the captured image 122 was captured, the calculation unit 114 performs thermal processing on the back surface of the wafer 12. An actual measurement value of the formation position of the layer 120 is detected.

Further, the calculation unit 114 uses the position detection result of the planned formation position (line end) of the thermal processing layer 120 by the detection control unit 96 as a theoretical value of the formation position of the thermal processing layer 120 on the back surface of the wafer 12. . This theoretical value assumes that there is no deviation between the positional relationship between the optical axis A1 of the laser unit 28 and the optical axis A2 of the infrared camera 70 determined by the positional relationship information 92 and the actual positional relationship between the two. This is the formation position of the thermally processed layer 120 in the case of FIG.

Then, the calculation unit 114 calculates (δx, δy) as values indicating the positional deviation (the amount of positional deviation and the direction of the deviation) between the theoretical value and the measured value of the formation position of the thermally processed layer 120 . The magnitude of each value of (δx, δy) indicates the amount of positional deviation in the X direction and the Y direction, and the positive and negative values of each value of (δx, δy) indicate the direction of positional deviation (X direction and positive or negative in the Y direction).

The calculation result (δx, δy) of the positional deviation is the relationship between the positional relationship between the optical axis A1 of the laser unit 28 and the optical axis A2 of the infrared camera 70 defined by the positional relationship information 92 and the actual positional relationship between the two. If there is no gap between them, it will be zero. Therefore, the calculation result (δx, δy) is a value indicating how much the positional relationship between the optical axis A1 and the optical axis A2 has changed from the designed value.

FIG. 12 is an explanatory diagram for explaining correction of the positional relationship information 92 by the correction unit 116. As shown in FIG. In FIG. 12, the coordinates (X1, Y1) are the coordinates (design values) of the optical axis A2 of the infrared camera 70, and the coordinates (X2, Y2) are the coordinates (design values) of the optical axis A1 of the laser unit . Coordinates (X1, Y1) and coordinates (X2, Y2) are relative position coordinates of the other [eg, coordinates (X2, Y2)] with reference to either one [eg, coordinates (X1, Y1)]. be. Also, Δx=X2−X1. Furthermore, in this embodiment, Y1=Y2.

When the calculation result (δx, δy) of the positional deviation is not zero, the relative positional relationship between the optical axis A1 and the optical axis A2 is the positional relationship indicated by the factory-shipped positional relationship information 92 as indicated by symbol XIIA in FIG. , to the positional relationship indicated by symbol XIIB in FIG.

Therefore, the correction unit 116 determines the actual position of the optical axis A1 of the laser unit 28 and the position of the optical axis A2 of the infrared camera 70 in the XY directions based on the positional deviation calculation results (δx, δy) by the calculation unit 114. By calculating the (latest) relative positional relationship, the positional relationship information 92 in the storage unit 82 is corrected. As a result, based on the position detection result of the detection control unit 96 and the positional relationship information 92 corrected by the correction unit 116, the thermally processed layer formation control unit 110 described above controls the laser unit 28, the stage driving mechanism 26, and the A modified region 200 can be formed inside the wafer 12 by controlling the unit drive mechanism 32 .

Such correction of the positional relationship information 92 by the information correction control unit 100, that is, the operation of each unit of the information correction control unit 100 is performed for each direction of the dividing lines C1 and C2 and for each wafer 12 under the control of the general control unit 80. , and/or for each of the plurality of wafers 12 . Therefore, the integrated control section 80 functions as a repeat control section of the present invention. Note that the positional relationship information 92 may be corrected periodically or when the laser processing apparatus 10 is activated.

[Action of laser processing device]
FIG. 13 is a flow chart showing the flow of the laser processing of the wafer 12 by the laser processing apparatus 10 having the above configuration, particularly the process of correcting the positional relationship information 92 corresponding to the control method of the laser processing apparatus of the present invention.

As shown in FIG. 13, when the wafer 12 to be laser-processed is held by suction on the Xθ stage 20, the detection control section 96 of the control device 24 is activated. The detection control unit 96 controls the stage driving mechanism 26, the unit driving mechanism 32, and the infrared microscope 30, and acquires the image data of the photographed image 102 of the wafer 12 as an alignment reference. Then, the detection control unit 96 performs alignment detection for detecting the positions of the division lines C1 and C2 in the wafer 12 based on the image data of the captured image 102 (step S1, corresponding to the detection step of the present invention). Further, the detection control unit 96 detects the positions of the planned division lines C1 and C2, thereby determining the position of the line end of one of the planned division lines C1 and C2 located within the invalid area 12a (the position of the thermal processing layer 120). Position to be formed) is also detected.

When the alignment detection is completed, the thermal processing layer formation control section 110 of the information correction control section 100 operates. The thermally processed layer formation control unit 110 controls the stage driving mechanism 26 and the unit driving mechanism 32 based on the detection result of the planned formation position of the thermally processed layer 120 by the detection control unit 96 and the positional relationship information 92 in the storage unit 82. The laser unit 28 is driven to form the thermally processed layer 120 on the rear surface of the wafer 12 as shown in FIG.

Next, the imaging control unit 112 drives the stage driving mechanism 26 and the unit driving mechanism 32 based on the detection result of the formation planned position of the thermally processed layer 120 by the detection control unit 96, and causes the infrared microscope 30 to photograph the thermally processed layer 120. After moving to the position, the thermal processing layer 120 is photographed by the infrared camera 70 (step S3, corresponding to the photographing step of the present invention). As a result, image data of the photographed image 122 of the heat-processed layer 120 is output from the infrared camera 70 to the calculation unit 114 .

The calculation unit 114 operates according to input of image data of the captured image 122 from the infrared camera 70 . After detecting the thermally processed layer 120 in the captured image 122 based on the image data of the captured image 122 by an image recognition method, the calculation unit 114 determines the position of the thermally processed layer 120 in the captured image 122 and the time when the captured image 122 was captured. and the position of the optical axis A2 of the infrared camera 70, the measured value of the formation position of the thermally processed layer 120 on the back surface of the wafer 12 is detected. Further, the calculation unit 114 acquires the detection result of the planned formation position of the thermal processing layer 120 detected by the detection control unit 96 during alignment detection as a theoretical value of the formation position of the thermal processing layer 120 on the back surface of the wafer 12. . Then, as shown in FIG. 11 described above, the calculation unit 114 calculates the positional deviation between the theoretical value and the actual measurement value of the formation position of the thermally processed layer 120, and the calculation result (δx, δy) is corrected by the correction unit 116 (step S4, corresponding to the calculation step of the present invention).

When the calculation result (δx, δy) of the positional deviation is input from the calculation unit 114, the correction unit 116, based on the calculation result (δx, δy), stores the positional relationship information 92 (step S5, corresponding to the correction step of the present invention).

When the correction of the positional relationship information 92 is completed, the modified region formation control section 98 operates. The modified region formation control section 98 controls the stage drive mechanism 26, the unit drive mechanism 32, and the laser unit 28 based on the alignment detection result by the detection control section 96 and the corrected positional relationship information 92 in the storage section 82. 5 to 8, one or more layers of modified regions 200 are formed inside the wafer 12 along the dividing lines C1 (step S6). Note that step S6 corresponds to the modified region forming step of the present invention.

Since the laser processing of the wafer 12 is performed based on the corrected positional relationship information 92, the relative position of the optical axis A1 of the laser unit 28 and the optical axis A2 of the infrared camera 70 changes due to changes in the environment in which the laser processing apparatus 10 is installed. deviates from the design value, the modified region 200 can be formed inside the wafer 12 with high accuracy along the dividing line C1.

After forming the modified region 200 along each planned division line C1, the overall control unit 80 executes repetitive control to repeatedly operate each part of the information correction control unit 100 (YES in step S7, NO in step S8). As a result, the processes from step S2 to step S5 described above are repeatedly executed, and the positional relationship information 92 in the storage unit 82 is re-corrected. In this case, the new heat-processed layer 120 may be formed, for example, at the end of the last planned division line C1 after forming the modified region 200 corresponding to the last planned division line C1. As a result, the formation of a new thermally processed layer 120 can be quickly started without relatively moving the wafer 12 and the laser unit 28 .

Then, by executing step S6 as described above, the modified region 200 of one layer or multiple layers is formed inside the wafer 12 along each dividing line C2. This completes the modified region forming step (NO in step S7).

When executing the above-described repetitive control for each wafer 12 or for each of a plurality of wafers 12 (YES in step S7), the integrated control unit 80 executes alignment detection in step S1 (YES in step S8), The process from step S2 to step S6 is executed.

The laser-processed wafer 12 is divided into a plurality of chips 14 by a known dividing device.

[Effect of this embodiment]
As described above, the laser processing apparatus 10 of the present embodiment forms the thermally processed layer 120 on the back surface of the wafer 12 and photographs the thermally processed layer 120. By calculating the positional deviation from the measured value, the positional relationship information 92 between the position of the optical axis A1 of the laser unit 28 and the position of the optical axis A2 of the infrared camera 70 can be corrected. As a result, even if the relative position between the optical axis A1 and the optical axis A2 deviates from the design value due to changes in the environment in which the laser processing apparatus 10 is installed, this deviation can be reflected in the positional relationship information 92.

Therefore, regardless of changes in the environment in which the laser processing apparatus 10 is installed, the modified region 200 can be formed inside the wafer 12 with high accuracy along the dividing lines C1 and C2. In addition, since the thermally processed layer 120 is formed directly on the wafer 12, it is not necessary to prepare a processed sample piece as in Patent Document 3 or attach/detach the processed sample piece to/from the X.theta. can be reduced. As a result, highly accurate laser processing of the wafer 12 can be easily performed.

[Modified example of machining unit]
FIG. 14 is an explanatory diagram for explaining a modification of the processing unit 22. As shown in FIG. In the processing unit 22 of the above embodiment, the position of the optical axis A1 of the laser unit 28 and the position of the optical axis A2 of the infrared camera 70 are aligned in the Y direction in terms of design, but as indicated by symbol XIVA in FIG. , the position of the optical axis A1 of the laser unit 28 and the position of the optical axis A2 of the infrared camera 70 in the Y direction may be shifted. Note that Δy=Y2−Y1.

As indicated by symbol XIVB in FIG. 14, even if the position of the optical axis A1 of the laser unit 28 and the position of the optical axis A2 of the infrared camera 70 are deviated in the Y direction, the calculation unit 114 The actual relative positional relationship between the optical axis A1 and the optical axis A2 can be calculated based on the positional deviation calculation results (δx, δy). As a result, the positional relationship information 92 in the storage section 82 can be corrected as in the above embodiment.

[others]
In the above-described embodiment, the thermally processed layer 120 is formed at the end of one of the dividing lines C1 and C2 in the invalid area 12a on the back surface of the wafer 12. However, the quality of the chip 14 is affected. The position where the thermal processing layer 120 is to be formed is not particularly limited as long as it is within the invalid region 12a that does not exert the

In the above embodiment, the heat-processed layer 120 is formed in a substantially linear pattern extending in the X direction, but the heat-processed layer 120 is not limited to a linear pattern and may be formed in an arbitrary pattern.

In the above embodiment, the processes from step S2 to step S5 shown in FIG. 13 are executed independently of other processes performed by the laser processing apparatus 10, but step S6 (modification It may be performed in parallel with other steps performed before (formation of region 200). As another process, for example, there is a height detection process for detecting the height of the back surface of the wafer 12 .

In the above embodiment, the stage drive mechanism 26 and the unit drive mechanism 32 were used as examples of the relative movement mechanism of the present invention. The configuration is not particularly limited.

Although the infrared microscope 30 is connected to the outside of the laser unit 28 in the above embodiment, the infrared microscope 30 may be provided inside the housing of the laser unit 28 .

10 ... laser processing equipment,
12 ... Wafer,
12a... invalid area,
20 ... Xθ stage,
22 ... processing unit,
24 ... control device,
26 ... stage driving mechanism,
28 ... laser unit,
30... Infrared microscope,
32 ... unit drive mechanism,
70... Infrared camera,
80 ... integrated control unit,
92 ... positional relationship information,
96 ... detection control unit,
98 ... modified region formation control unit,
100... Information correction control unit,
122 ... photographed image,
110...Thermal processing layer formation control unit,
112 ... photographing control unit,
114 ... calculation unit,
116 ... correction unit,
120... photographed image,
200... Modified area

Claims (8)

In a laser processing apparatus for forming a modified region inside a wafer along the dividing line of the wafer by irradiating laser light with a focal point aligned with the inside of the wafer,
a laser optical system that irradiates the laser beam toward one surface of the wafer;
an infrared camera arranged at a position facing the one surface and having a second optical axis different from the first optical axis of the laser optical system for photographing the wafer;
a relative movement mechanism for integrally moving the laser optical system and the infrared camera relative to the wafer;
a detection control unit for causing the infrared camera to photograph the alignment reference of the wafer and detecting the position of the line to be divided based on a first photographed image of the alignment reference photographed by the infrared camera;
The relative movement mechanism is driven to move the wafer relative to the laser optical system, and the laser beam of the laser optical system is condensed on the one surface of the wafer that is relatively moved to the one surface. a thermally processed layer formation control unit for forming a thermally processed layer in the
an imaging control unit that drives the relative movement mechanism to relatively move the infrared camera to an imaging position of the thermally processed layer and causes the infrared camera to capture a second captured image of the thermally processed layer;
Positional deviation between the theoretical value and the measured value of the formation position of the thermally processed layer in the one plane based on the second photographed image and the known positional relationship information of the first optical axis and the second optical axis. a computing unit that computes
a correction unit that corrects the positional relationship information based on the calculation result of the calculation unit;
A laser processing device comprising: In a state in which the laser beam of the laser optical system is converged on the inside of the wafer, the position detection result of the line to be divided by the detection control unit and the positional relationship information corrected by the correction unit. according to the relative movement mechanism, the laser optical system is relatively moved with respect to the wafer along the line to be divided to form the modified region inside the wafer along the line to be divided. 2. The laser processing apparatus according to claim 1, further comprising an area formation controller. The detection control unit drives the relative movement mechanism to relatively move the infrared camera to an imaging position of the alignment reference, causes the infrared camera to photograph the alignment reference, and obtains the first captured image. The laser processing apparatus according to claim 1 or 2. The detection control unit detects, based on the first photographed image, the position of the planned dividing line and a predetermined planned formation position of the thermally processed layer within the invalid area of the wafer,
The thermally processed layer formation control unit controls the relative movement mechanism and the laser optical system based on the positional relationship information and the detection result of the planned formation position by the detection control unit to move the layer to the planned formation position. 4. The laser processing apparatus according to any one of claims 1 to 3, which forms a thermally processed layer. 5. The laser processing apparatus according to claim 4, wherein the planned formation position is an end portion of the planned division line. a repeat control unit for repeatedly operating at least the thermally processed layer formation control unit, the imaging control unit, the calculation unit, and the correction unit for each direction of the scheduled division line, each wafer, or each of a plurality of wafers; The laser processing apparatus according to any one of claims 1 to 5. A laser optical system for irradiating a laser beam toward one surface of a wafer, and a second optical axis arranged at a position facing the one surface and different from the first optical axis of the laser optical system, and photographing the wafer. and a relative movement mechanism for integrally moving the laser optical system and the infrared camera relative to the wafer, wherein the laser optical system focuses the laser light on the inside of the wafer. to form a modified region inside the wafer along the dividing line of the wafer,
a detection step of causing the infrared camera to photograph the alignment reference of the wafer and detecting the position of the line to be divided based on a first photographed image of the alignment reference photographed by the infrared camera;
Thermal processing for forming a thermally processed layer on the one surface of the wafer, which is relatively moved with respect to the laser optical system by the relative movement mechanism, by condensing the laser beam of the laser optical system on the one surface of the wafer. a layer forming step;
a photographing step of moving the infrared camera to a photographing position of the heat-processed layer by the relative movement mechanism and causing the infrared camera to photograph a second photographed image of the heat-processed layer;
A theoretical value of the formation position of the thermally processed layer within the one plane based on the second photographed image photographed in the photographing step and the known positional relationship information of the first optical axis and the second optical axis. and a calculation step of calculating the positional deviation between the measured value and
a correction step of correcting the positional relationship information based on the calculation result of the calculation step;
A method of controlling a laser processing apparatus having In a state in which the laser beam of the laser optical system is converged on the inside of the wafer, the position detection result of the line to be divided in the detection step and the positional relationship information corrected in the correction step. according to the relative movement mechanism, the laser optical system is relatively moved with respect to the wafer along the line to be divided to form the modified region inside the wafer along the line to be divided. 8. The method of controlling a laser processing apparatus according to claim 7, further comprising a region forming step.

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