Method for determining hydrophilicity of wafer and processing device

Abstract

To provide a method for determining the hydrophilicity of a wafer that can easily check whether the entire top surface of a wafer has hydrophilicity, and a processing device.SOLUTION: A method for determining the hydrophilicity of a wafer W includes: a first imaging step of picking up an image of the entire top surface of the wafer W with a camera 100; a water screen forming step of forming a water screen f on the entire top surface of the wafer W; a second imaging step of picking up an image of the entire top surface of the wafer W with the camera 100 after the water screen forming step; a difference image forming step of forming a difference image from the difference between the brightness of the first image picked up in the first imaging step and the brightness of the second image picked up in the second imaging step; and a determination step of, when the difference image is completely white, determining that the entire top surface of the wafer W is provided with hydrophilicity, and in the other situations, determining that the entire top surface of the wafer W is not provided with hydrophilicity. A cutting device (processing device) 1 executes predetermined processing on the wafer W that is determined to have hydrophilicity according to the hydrophilicity determination method.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to a method for determining whether or not the entire upper surface of a wafer is hydrophilic, and to a processing apparatus for processing the wafer after confirming that the entire upper surface of the wafer is hydrophilic using this determination method. [Background technology]

[0002] In the manufacturing process of semiconductor devices, the surface of a disk-shaped semiconductor wafer (hereinafter simply referred to as a "wafer") is divided into many rectangular regions by planned division lines called streets that are arranged in a grid pattern, and devices such as ICs and LSIs are formed in each rectangular region. Then, the wafer on which many devices are thus formed is cut along the planned division lines with a cutting blade of a cutting machine called a dicer, thereby obtaining multiple semiconductor chips.

[0003] In cutting devices, the wafer is cut while cutting water is being supplied to the cutting blade, and a water film is formed on the upper surface of the wafer to prevent cutting debris from adhering to the upper surface of the wafer.

[0004] As described above, even if a water film is formed on the upper surface of the wafer, the water film on the upper surface of the wafer may be destroyed by moving the chuck table holding the wafer in the X-axis direction (cutting feed direction) during the cutting process of the wafer. When the water film on the upper surface of the wafer is destroyed in this way, cutting debris adheres to the upper surface of the wafer, and there is a problem that the cutting debris cannot be removed even if the upper surface of the wafer is subsequently washed with cleaning water by a cleaning unit.

[0005] Therefore, Patent Documents 1 and 2 propose a method of irradiating the upper surface (cut surface) of a wafer with ultraviolet light to generate ozone and active oxygen to impart hydrophilicity to the upper surface of the wafer, thereby continuously forming a water film on the upper surface of the wafer. Patent Document 3 also proposes imparting hydrophilicity to the upper surface of the wafer by irradiating the upper surface (cut surface) of the wafer with plasma. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2006-295050 A [Patent Document 2] JP 2010-267638 A [Patent Document 3] JP 2013-161999 A Summary of the Invention [Problem to be solved by the invention]

[0007] However, even if the top surface of a wafer is made hydrophilic using the methods proposed in Patent Documents 1 to 3, there is no way to confirm whether the entire top surface of the wafer is actually hydrophilic, and therefore there is a possibility that cutting debris may remain partially on the top surface of the wafer.

[0008] The present invention has been made in consideration of the above-mentioned problems, and its object is to provide a method for determining the hydrophilicity of a wafer, which can easily confirm whether or not the entire upper surface of a wafer is hydrophilic, and a processing apparatus which can reliably prevent processing debris from adhering to the upper surface of a wafer. [Means for solving the problem]

[0009] The method for determining the hydrophilicity of a wafer according to the first invention is characterized in that it comprises a first imaging step of imaging the entire top surface of the wafer with a camera, a water film formation step of supplying water in an amount sufficient to form a water film over the entire top surface of the wafer and rotating the wafer at a predetermined rotation speed around the center of the wafer as an axis, a second imaging step of imaging the entire top surface of the wafer with the camera after the water film formation step, a difference image formation step of forming a difference image based on the difference in brightness between a first image captured in the first imaging step and a second image captured in the second imaging step, and a determination step of determining that the entire top surface of the wafer is not hydrophilic if there is a non-white portion in the difference image, and determining that the entire top surface of the wafer is hydrophilic if the difference image is pure white.

[0010] The method for determining the hydrophilicity of a wafer according to the second invention is characterized in that it comprises a water film forming step of supplying water in an amount sufficient to form a water film over the entire upper surface of the wafer and rotating the wafer at a predetermined rotation speed around the center of the wafer as an axis, a reflected light receiving step of receiving measurement light projected from the reflective sensor toward the wafer while moving the reflective sensor in a direction parallel to the upper surface of the wafer after the water film forming step and receiving reflected light reflected by the upper surface of the wafer and / or the water film f, and a determination step of determining that the entire upper surface of the wafer is hydrophilic if the amount of light received by the reflective sensor in the reflected light receiving step is higher than a predetermined threshold, and determining that the entire upper surface of the wafer is not hydrophilic if at least a portion of the amount of light received is lower than the threshold.

[0011] A processing apparatus according to the present invention includes a chuck table for holding a wafer, a processing unit for processing the wafer held on the chuck table, a cleaning unit for rotating the wafer held on a cleaning table and spraying cleaning water onto an upper surface of the wafer to clean the upper surface of the wafer, and a control unit, and processes the wafer by the processing unit after carrying out the method for determining the hydrophilicity of a wafer according to the first or second invention, The present invention is characterized in that it includes a judgment unit which supplies water to the center of a wafer held on the chuck table or the cleaning table, rotates the chuck table or the cleaning table to form a water film on the entire upper surface of the wafer, and then judges whether the entire upper surface of the wafer is hydrophilic or not. Effect of the Invention

[0012] According to the method for determining the hydrophilicity of a wafer of the first invention, if a difference image formed by the difference in brightness between the first image captured in the first imaging process and the second image captured in the second imaging process contains any non-white areas, it is determined that the entire top surface of the wafer is hydrophilic, and if the difference image is pure white, it is determined that the entire top surface of the wafer is hydrophilic, so that it is easy to confirm whether or not the entire top surface of the wafer is hydrophilic.

[0013] According to the method of determining the hydrophilicity of a wafer of the second invention, if the amount of light received by the reflective sensor in the reflected light receiving process indicates a value higher than a predetermined threshold, it is determined that the entire upper surface of the wafer is hydrophilic, and if at least a portion of the amount of light received indicates a value lower than the threshold, it is determined that the entire upper surface of the wafer is hydrophilic, so that it is easy to confirm whether or not the entire upper surface of the wafer is hydrophilic.

[0014] According to the processing apparatus of the present invention, after confirming that the entire surface of the wafer has been made hydrophilic by the method for determining the hydrophilicity of a wafer according to the first or second invention, the wafer is subjected to a predetermined processing. Therefore, when the surface of the wafer is cleaned with cleaning water in the cleaning unit after processing, processing debris generated during wafer processing is reliably washed away by the cleaning water, and adhesion of processing debris to the upper surface of the wafer after processing can be reliably prevented. [Brief description of the drawings]

[0015] [Figure 1]1 is a perspective view of a cutting device as one embodiment of a processing device according to the present invention; [Diagram 2] FIG. [Diagram 3] 1 is a flowchart showing the process steps of a method for determining the hydrophilicity of a wafer according to a first aspect of the present invention. [Figure 4] 3 is a cutaway side view showing a first imaging step in the method for determining hydrophilicity of a wafer according to the first invention. FIG. [Diagram 5] 1 is a cutaway side view showing a water film forming step (water supplying step) in the method for determining hydrophilicity of a wafer according to the first aspect of the present invention. [Figure 6] 3 is a cutaway side view showing a water film forming step in the method for determining hydrophilicity of a wafer according to the first invention. FIG. [Figure 7] 4 is a cutaway side view showing a second imaging step in the method for determining hydrophilicity of a wafer according to the first invention. FIG. [Figure 8] FIG. 1A is a diagram showing a difference image (with hydrophilicity), and FIG. 1B is a diagram showing a difference image (without hydrophilicity). [Figure 9] 1 is a flowchart showing a method for determining hydrophilicity of a wafer and a cutting method according to a first aspect of the present invention in the order of steps. [Figure 10] 10 is a flowchart showing the process steps of a method for determining the hydrophilicity of a wafer according to a second aspect of the present invention. [Figure 11] 11 is a cutaway side view showing a reflected light receiving step in the method for determining hydrophilicity of a wafer according to the second invention. FIG. [Figure 12] FIG. 11 is a diagram showing the state when the surface of the wafer is hydrophilic, where (a) is an explanatory diagram showing how reflected light is received by a reflective sensor, and (b) is a diagram showing the relationship between the measured amount of received light in the radial direction of the wafer and a threshold value. [Figure 13] FIG. 11 is a diagram showing the state when the surface of a wafer is not hydrophilic, where (a) is an explanatory diagram showing how reflected light is received by a reflective sensor, and (b) is a diagram showing the relationship between the measured amount of received light in the radial direction of the wafer and a threshold value. [Figure 14] 10 is a flowchart showing a method for determining hydrophilicity of a wafer and a cutting method according to a second aspect of the present invention in the order of steps. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. Note that the following describes a cutting device as one embodiment of a processing device according to the present invention.

[0017] [Cutting equipment configuration] Hereinafter, a cutting device as one embodiment of a processing device according to the present invention will be described. In the following description, the front-rear direction in Fig. 1 is defined as the X-axis direction (cutting feed direction), the left-right direction is defined as the Y-axis direction (indexing feed method), and the up-down direction is defined as the Z-axis direction (cutting feed direction).

[0018] The cutting device 1 shown in FIG. 1 is what is known as a dual dicer, and is equipped with a base 2 that supports each of the components. On the upper rear surface (-X axis direction) of this base 2, two vertical gate-shaped columns 3, 4 that are long in the left-right direction (Y axis direction) are erected parallel to each other, one at the front and one at the back.

[0019] A rectangular opening 2a elongated in the front-rear direction (X-axis direction) is formed on the upper surface of the center of the Y-axis direction (left-right direction) of the base 2, and a cassette support 5 that moves up and down in the vertical direction (Z-axis direction) by a lifting mechanism (not shown) is provided on the front (+X-axis direction) corner on the left (-Y-axis direction) of the opening 2a. A rectangular box-shaped cassette 6 that stores a plurality of disk-shaped wafers W (see FIG. 2) that are the workpieces is disposed on the upper surface of the cassette support 5. A loading / unloading means 7 for loading and unloading the wafers W into and from the cassette 6 is provided near the cassette 6. For convenience of explanation, in FIG. 1, only the outline of the cassette 6 is shown by a chain line.

[0020] The cutting device 1 according to the present embodiment includes, as its main components, a chuck table 10 that holds and rotates a wafer W, which is a workpiece; a first transport means 20 that receives the wafer W taken out from the cassette 6 by the loading / unloading means 7 and transports it to the chuck table 10; a pair of left and right cutting units 30 that are processing mechanisms that cut the wafer W held on the holding surface of the chuck table 10; a pair of left and right Z-axis moving mechanisms (notching feed mechanisms) 40 that raise and lower each of the cutting units 30 in the Z-axis direction (notching feed direction); a Y-axis moving mechanism (indexing feed mechanism) 50 that reciprocates each cutting unit 30 along the Y-axis direction (indexing feed direction); a cleaning unit 60 that forms a water film on the entire upper surface of the wafer W before cutting and cleans the upper surface of the wafer W after cutting; a second transport means 80 that receives the wafer W from the chuck table 10 and transports it to the cleaning unit 60; and a control unit 90 (see FIG. 4) that controls each of the components. The cutting device 1 is equipped with an X-axis moving mechanism (cutting feed mechanism) that moves the chuck table 10 in the X-axis direction (cutting feed direction). However, since this X-axis moving mechanism is configured with a known ball screw mechanism, illustration and description thereof will be omitted.

[0021] The configurations of the main components of the cutting device 1, namely, the chuck table 10, the first conveying means 20, the cutting unit 30, the Z-axis moving mechanism 40, the Y-axis moving mechanism 50, the cleaning unit 60, the second conveying means 80 and the control unit 90, will be described below.

[0022] (Chuck table) The chuck table 10 is a disk-shaped member rotatably disposed in the approximate center of the base 2, and its upper surface constitutes a holding surface for holding a wafer W (see FIG. 2). The holding surface of the chuck table 10 is selectively connected to a suction source (not shown).

[0023] The chuck table 10 is supported by an X-axis moving mechanism (not shown) via a rotating mechanism (not shown) disposed below the chuck table 10. That is, the chuck table 10 is rotated around a vertical axis by the rotating mechanism (not shown) and can be moved back and forth along the X-axis direction (cutting feed direction) by an X-axis moving mechanism (not shown) disposed below the chuck table 10. The periphery of the chuck table 10 at a rectangular opening 2a opening on the upper surface of the base 2 is covered by a rectangular plate-shaped cover 8 that moves together with the chuck table 10, and both sides (left and right) of the cover 8 at the opening 2a in the X-axis direction (left and right) are covered by bellows-shaped expandable covers 9 that expand and contract together with the cover 8 in the X-axis direction.

[0024] Here, the wafer W, which is the workpiece, is, for example, a thin, disk-shaped member made of single crystal silicon (Si), and as shown in Fig. 2, its surface (the upper surface in Fig. 2) is partitioned into a plurality of rectangular regions by mutually orthogonal lattice-like division lines (streets) L1, L2, and devices D such as ICs and LSIs are formed in each rectangular region. A dicing tape T is attached to the back surface (the lower surface in Fig. 2) of the wafer W having a large number of devices D formed on its surface. Note that, in addition to silicon (Si), silicon carbide (SiC), glass, ceramics, sapphire, etc. may be used as the material of the wafer W.

[0025] (First conveying means) The first transport means 20 receives the wafer W removed from the cassette 6 by the carry-in / out means 7 and transports it to the chuck table 10. This first transport means 20 is equipped with an L-shaped arm 22 that is movable in the left-right direction (Y-axis direction) along a guide rail 21 provided on one (front) gate-type column 3 along the left-right direction (Y-axis direction), and a disk-shaped suction pad 24 attached to the lower end of a shaft 23 that extends vertically downward from the tip of the arm 22.

[0026] (Cutting unit) The pair of cutting units 30 can be moved up and down in the Z-axis direction (cutting feed direction) by a pair of front and rear Z-axis moving mechanisms 40, and can be moved back and forth in the Y-axis direction (indexing feed direction) by a pair of front and rear Y-axis moving mechanisms 50. Note that since the basic configuration of both cutting units 30 is the same, the configuration of only one of the cutting units 30 will be described below.

[0027] Each cutting unit 30 is attached to the lower part of each Z-axis base 42 of the Z-axis moving mechanism 40, which will be described later, together with a camera 31 serving as an imaging means, and each includes a disk-shaped cutting blade 32 attached to the tip of a spindle (not shown) arranged in the Y-axis direction (left-right direction). Each spindle and each cutting blade 32 are rotated at high speed by each spindle motor (not shown) serving as a rotary drive source. Here, each cutting blade 32 is configured by forming a cutting edge on the outer periphery of a circular base, and the cutting edge is formed by fixing diamond abrasive grains or the like with a resin bond, a metal bond, a vitrified bond, or the like.

[0028] In addition, each camera 31, which is an imaging means, captures an image of the surface of the wafer W held on the holding surface of the chuck table 10 and detects the positions of the planned division lines L1, L2 (see Figure 2) by image processing such as pattern matching, and is equipped with an imaging element such as a CCD or CMOS.

[0029] (Z-axis movement mechanism) Each pair of Z-axis moving mechanisms 40 is a mechanism for independently moving each cutting unit 30 up and down along the Z-axis direction (cutting feed direction), and is provided on the rear (-X-axis side) gate-shaped column 4. That is, each Z-axis moving mechanism 40 includes a pair of Z-axis guide rails 41 arranged parallel to each other and vertically on the left and right of a Y-axis base 51 (described later) of each Y-axis moving mechanism 50, a Z-axis base 42 that can move up and down along these Z-axis guide rails 41, a rotatable Z-axis ball screw 43 arranged vertically between the pair of Z-axis guide rails 41, and a Z-axis servo motor 44 that can rotate forward and backward and drives the Z-axis ball screw 43. Each cutting unit 30 is attached to the lower part of each Z-axis base 42. A nut member (not shown) is protruded from the back surface of each Z-axis base 42, and each Z-axis ball screw 43 is screwed and inserted into this nut member.

[0030] In each Z-axis moving mechanism 40 configured as described above, when the Z-axis servo motor 44 is started and the Z-axis ball screw 43 rotates forward and backward, the Z-axis base 42, which has a protruding nut member (not shown) that screws into the Z-axis ball screw 43, moves up and down along a pair of Z-axis guide rails 41, so that each cutting unit 30 attached to the Z-axis base 42 can also move independently in the Z-axis direction (up and down) along the Z-axis direction (cutting feed direction).

[0031] (Y-axis movement mechanism) The pair of left and right Y-axis movement mechanisms 50 are mechanisms for independently reciprocating each cutting unit 30 along the Y-axis direction (indexing feed direction), and are provided on the rear (-X-axis side) gate-type column 4 together with the Z-axis movement mechanism 40. That is, each Y-axis movement mechanism 50 includes a Y-axis base 51, and these Y-axis bases 51 are each movable along the Y-axis direction along a pair of upper and lower Y-axis guide rails 52 that are arranged in parallel to each other along the Y-axis direction (left and right direction) on the front side of the gate-type column 4.

[0032] In the pair of left and right Y-axis movement mechanisms 50, a pair of upper and lower rotatable Y-axis ball screws 53 are arranged along the Y-axis direction (left and right direction) between the pair of upper and lower Y-axis guide rails 52, and nut members (not shown) protruding from the back surfaces of the pair of left and right Y-axis bases 51 are screwed into the Y-axis ball screws 53. One axial end of each Y-axis ball screw 53 is connected to a Y-axis servo motor 54 (only one of which is shown in FIG. 1) which serves as a rotational drive source.

[0033] Therefore, in each Y-axis movement mechanism 50, when the Y-axis servo motor 54 is driven to rotate the Y-axis ball screws 53 forward and backward, a pair of left and right Y-axis bases 51 having protruding nut members (not shown) that screw into these Y-axis ball screws 53 can move together with the Z-axis base 42 in the Y-axis direction (indexing feed direction) along the Y-axis guide rail 52. Therefore, the cutting unit 30 and the camera 31 attached to each Z-axis base 42 can move in the Y-axis direction (indexing feed direction) along the Y-axis guide rail 52.

[0034] As described above, in the cutting device 1 shown in FIG. 1, the chuck table 10 and the wafer W held thereon are movable along the X-axis direction (cutting feed direction), and the pair of left and right cutting units 30 and cameras 31 are movable along the Y-axis direction (indexing feed direction) and the Z-axis direction (cutting feed direction), respectively.

[0035] (Washing unit) As described below, the cleaning unit 60 functions to form a water film f (see FIG. 6) on the entire upper surface of the wafer W before cutting and to clean the upper surface of the wafer W after cutting, and is disposed in front of and to the right of the opening 2a on the base 2 as shown in FIG. 1. As shown in FIGS. 4 to 7, the cleaning unit 60 includes a cleaning table 61 that rotates while suction-holding the wafer W, and a nozzle 62 that supplies water (pure water) from above to the wafer W suction-held on the cleaning table 61.

[0036] The cleaning table 61 is a disk-shaped member, and is configured by joining together an upper frame body 61A and a lower support plate 61B, and a disk-shaped porous member 63 made of porous ceramics or the like is incorporated in the center of the frame body 61A. The upper surface of the porous member 63 forms a holding surface for holding the wafer W.

[0037] A servo motor 64, which is a rotary drive source, and an encoder 65, which detects the rotation direction and rotation speed of the servo motor 64, are disposed below the cleaning table 61, and the center of the cleaning table 61 is fixed to the upper end of a rotation shaft (motor shaft) 66 extending vertically upward from the servo motor 64. A rotary joint 67 is provided at the middle part of the rotation shaft 66. Therefore, when the servo motor 64 is started, its rotation is transmitted to the cleaning table 61 via the rotation shaft 66, so that the cleaning table 61 rotates around the axis at a predetermined speed. The servo motor 64 and the encoder 65 are electrically connected to a control unit 90.

[0038] A communication passage 68 is formed inside each of the cleaning table 61, the rotary shaft 66, and the rotary joint 67. One end (upper end) of the communication passage 68 opens to the lower surface of the porous member 63, and the other end (lower end) of the communication passage 68 is bent at a right angle in an L-shape inside the rotary joint 67 and connected to a pipe 69. Two branch pipes 69a and 69b branch out from the pipe 69. One branch pipe 69a is connected to a suction source 71 via a variable orifice 70 and an on-off valve V1, and the other branch pipe 69b is connected to an air supply source 73 via a variable orifice 72 and an on-off valve V2. The pipe 69 is provided with a pressure gauge 74 for measuring the pressure of the air flowing through the pipe 69. The on-off valves V1 and V2 are electrically connected to a control unit 90, and their opening and closing operations are controlled by the control unit 90.

[0039] On the other hand, a rotating shaft 75, a servo motor 76 for rotating the rotating shaft 75, and an encoder 77 for detecting the rotation direction and rotation angle of the servo motor 76 are vertically arranged on the side of the cleaning table 61, and a rotating arm 78 extends horizontally from the upper end of the rotating shaft 75. A nozzle 62 is vertically attached to the tip of the rotating arm 78, and a water supply source 79 is connected to the nozzle 62. By rotating the rotating shaft 66 by a predetermined angle (90°) by the servo motor 76, the rotating arm 78 and the nozzle 62 attached to the tip thereof are horizontally rotated about the rotating shaft 66 to be selectively positioned at the retracted position shown in FIG. 4 and the water supply position shown in FIG. 5. The length of the rotating arm 78 is set to a value such that, when the rotating arm 78 is positioned at the water supply position shown in FIG. 5, an injection port (not shown) opening on the lower surface of the nozzle 62 attached to the tip of the rotating arm 78 is positioned at the center of the wafer W. The servo motor 64 and the encoder 65 are electrically connected to a control unit 90.

[0040] (Second conveying means) The second transport means 80 serves to transport the wafer W between the chuck table 10 and the cleaning table 61 of the cleaning unit 60. The second transport means 80 includes an L-shaped arm 82 that is movable in the left-right direction (Y-axis direction) along a guide rail 81 that is provided on the front surface of one (front) gate-type column 3 along the left-right direction (Y-axis direction), and a disk-shaped suction pad 84 attached to the lower end of a shaft 83 that extends vertically downward from the tip of the arm 82.

[0041] (Control unit) The control unit 90 controls each of the components constituting the cutting device 1, and includes a CPU (Central Processing Unit) that performs arithmetic processing according to a control program, and memories such as a ROM (Read Only Memory) and a RAM (Random Access Memory). In particular, in this embodiment, as described below, the control unit 90 performs a function of determining whether the entire upper surface of the wafer W is hydrophilic or not by image processing, and as shown in Fig. 4, the control unit 90 includes a differential image forming unit 91 and a determination unit 92. The functions of the differential image forming unit 91 and the determination unit 92 will be described in detail later.

[0042] [How to determine the hydrophilicity of a wafer] <First Invention> Next, a method for determining the hydrophilicity of the wafer W according to the first aspect of the invention, which is carried out in the cutting device 1 configured as above, will be described. As shown in FIG. 3, the method includes the following steps: 1) First imaging process 2) Water film formation process 3) Second imaging process 4) Differential image formation process 5) Judgment process These steps are carried out in this order to determine whether or not the entire top surface of the wafer W is hydrophilic. Here, 1) the first imaging step, 2) the water film forming step, 3) the second imaging step, 4) the differential image forming step, and 5) the determination step in the determination method according to the first invention will be described below with reference to Figs. 4 to 9.

[0043] 1) First imaging process: As shown in FIG. 4, the first imaging step is a step of forming a first image by imaging the entire upper surface of the wafer W held on the cleaning table 61 of the cleaning unit 60 with the camera 100. Specifically, in this first imaging step, one wafer W is taken out of the cassette 6 by the carry-in / out means 7 shown in FIG. 1, and the taken-out wafer W is transferred to the first conveying means 20. Then, the first conveying means 20 conveys the wafer W to the chuck table 10 by the suction pad 24, and places the wafer W on the holding surface of the chuck table 10 with the dicing tape T facing down. Here, the wafer W accommodated in the cassette 6 is irradiated with ultraviolet rays by an ultraviolet irradiating means (not shown) provided in the cassette 6, thereby imparting hydrophilicity to the entire surface. Note that the entire surface of the wafer W can also be made hydrophilic by irradiating the entire surface of the wafer W with plasma instead of ultraviolet rays.

[0044] In this embodiment, the camera 100 and the differential image forming section 91 and determining section 92 provided in the control section 90 constitute a determining unit.

[0045] Next, the second transport means 80 sucks and holds the wafer W on the chuck table 10 by the suction pad 84, transports the wafer W to the cleaning unit 60, and places it on the cleaning table 61. Then, the control unit 90 opens one of the on-off valves V2 while closing the other on-off valve V1. As a result, air in the porous member 63 of the cleaning table 61 is sucked by the suction source 71 through the communication passage 68, generating a negative pressure in the porous member 63, and the wafer W is sucked and held on the holding surface of the cleaning table 61 with the dicing tape T facing down by the negative pressure, as shown in FIG. 4 (step S1 in FIG. 9).

[0046] From the above state, as shown in Fig. 4, while illuminating the entire upper surface of the wafer W from diagonally above the wafer W with the lighting fixture 101, the entire upper surface of the wafer W is imaged from diagonally above the wafer W with the camera 100 to form a first image, and this first image is stored in the memory of the control unit 90 (step S2 in Fig. 9). Note that in this first imaging step, the nozzle 62 is retracted to a retracted position to the side of the cleaning table 61.

[0047] 2) Water film formation process: The water film forming step is a step of forming a water film f shown in Fig. 6 on the entire upper surface of the wafer W after the first imaging step. Specifically, as shown in Fig. 5, the servo motor 76 of the cleaning unit 60 is started to rotate the rotary shaft 75 and the rotary arm 78 by a predetermined angle. Then, the rotary arm 78, which had been retracted to the retracted position, and the nozzle 62 attached to its tip rotate horizontally, and the nozzle 62 is positioned above the center of the wafer W. In this state, water (pure water) is supplied from a water supply source 79 to the nozzle 62, and a predetermined amount of water (an amount necessary to form a water film f of a predetermined thickness shown in Fig. 6) is dropped from the nozzle 62 onto the center of the upper surface of the wafer W.

[0048] As described above, when a predetermined amount of water is supplied from the nozzle 62 to the center of the upper surface of the wafer W, as shown in Fig. 6, the servo motor 76 is started again to rotate the rotary shaft 75 by a predetermined angle, thereby rotating the rotary arm 78 and the nozzle 62 in the horizontal direction and retracting the rotary arm 78 and the nozzle 62 to their retracted positions. Then, from this state, the servo motor 64 is started to rotate the cleaning table 61 and the wafer W held thereon at a predetermined speed around the axis in the direction of the arrow in the figure. The rotation speed of the cleaning table 61 is, for example, 100 min -1The wafer W is rotated at 90° C. for 10 seconds. Then, the water supplied from the nozzle 62 to the center of the upper surface of the wafer W spreads uniformly toward the outer periphery of the wafer W by the centrifugal force caused by the rotation of the wafer W, and a water film f of uniform thickness is formed on the upper surface of the wafer W as shown in FIG. 6 (step S3 in FIG. 9). In this embodiment, the water film f is formed on the upper surface of the wafer W held on the cleaning table 61, but the water film f may be formed on the upper surface of the wafer W held on the chuck table 10. In this embodiment, the predetermined amount of water supplied to the center of the upper surface of the wafer W is an amount of water that overflows from the upper surface of the wafer W, and the overflowing water may be removed from the wafer W by the rotation of the cleaning table 61 to form the water film f on the upper surface of the cleaning table 61.

[0049] 3) Second imaging process: As shown in Fig. 7, the second imaging step is a step of imaging the entire upper surface of the wafer W on which a water film f has been formed in the previous water film forming step by the camera 100 to form a second image. Specifically, in this second imaging step, similar to the first imaging step, the entire upper surface of the wafer W is illuminated by the lighting fixture 101 from diagonally above the wafer W, while the entire upper surface of the wafer W is imaged by the camera 100 from diagonally above the wafer W to form a second image, and the second image is stored in the memory of the control unit 90 (step S4 in Fig. 9). Note that, in this second imaging step as well, the nozzle 62 and the rotating arm 78 are retracted to the retracted position.

[0050] 4) Differential image formation process: The differential image forming step is a step in which the differential image forming section 91 of the control section 90 forms a differential image based on the difference between the brightness of the first image formed in the first imaging step and the brightness of the second image formed in the second imaging step. That is, the differential image forming section 91 forms a differential image as shown in Fig. 8(a) and (b) based on the difference between the brightness of the first image and the brightness of the second image stored in the memory of the control section 90 (step S5 in Fig. 9).

[0051] 5) Judgment process: The judgment step is a step of judging whether the entire upper surface of the wafer W is hydrophilic (whether the entire upper surface of the wafer W is hydrophilic) based on the differential image formed in the previous differential image forming step. That is, the judgment unit 92 of the control unit 90 judges whether the entire differential image is pure white (step S6 in FIG. 9). For example, if the entire differential image is pure white as shown in FIG. 8(a) (step S6: Yes), it is judged that the entire upper surface of the wafer W is hydrophilic, and cutting processing is performed on the wafer W (step S7 in FIG. 9). On the other hand, as shown in FIG. 8(b), if there is a non-white portion in the differential image (step S6: No), it is judged that the upper surface of the wafer W is not hydrophilic, and the wafer W is returned to the cassette 6 (step S11 in FIG. 9), and the subsequent processing on the wafer W is terminated (step S10 in FIG. 9). In addition, the wafer W that is determined not to have a hydrophilic surface and returned to the cassette 6 is irradiated with ultraviolet light or plasma to impart hydrophilicity to the surface, and then the presence or absence of hydrophilicity described above is judged again, or the wafer is removed from the processing target. For example, the cutting device 1 has a function of irradiating the wafer W stored in the cassette 6 with ultraviolet light or plasma. Alternatively, the cutting device 1 may have a function of irradiating the wafer W removed from the cassette 6 with ultraviolet light or plasma to impart hydrophilicity to the wafer W, and then the presence or absence of hydrophilicity may be judged again.

[0052] In this embodiment, the judgment unit 92 provided in the control unit 90 automatically judges whether or not the upper surface of the wafer W is hydrophilic based on the differential image formed by the differential image forming unit 91, but the operator may visually inspect the differential image to judge whether or not the upper surface of the wafer W is hydrophilic.

[0053] If the entire top surface of the wafer W is determined to be hydrophilic by the above method for determining the hydrophilicity of the wafer W (step S6: Yes in Figure 9), cutting processing is performed on the wafer W as described above (step S7 in Figure 9). Below, a method for cutting the wafer W using the cutting device 1 shown in Figure 1 will be described.

[0054] [Wafer cutting method] When the entire upper surface of the wafer W is determined to be hydrophilic by the hydrophilicity determination method (Step S6 in FIG. 9: Yes), the wafer W is transferred from the cleaning table 61 to the second transfer means 80. That is, when one of the on-off valves V1 shown in FIG. 4 is closed and the other on-off valve V1 is opened, air from the air supply source 73 is supplied to the porous member 63 of the cleaning table 61 via the branch pipe 69b, the piping 69, and the communication passage 68 and is blown upward from the porous member 63, so that the wafer W held on the cleaning table 61 can be easily detached from the cleaning table 61 together with the dicing tape T.

[0055] From the above state, the wafer on the cleaning table 61 is sucked and held by the suction pads 84 of the second transport means 80, and the second transport means 80 moves in the -Y axis direction (left direction) along the guide rails 81 to transport the wafer W to the chuck table 10 and place the wafer W on the holding surface of the chuck table 10. Then, the chuck table 10 is connected to a suction source (not shown) and a negative pressure is generated on the holding surface, and the wafer W is sucked and held on the holding surface of the chuck table 10 with the dicing tape T facing down by the negative pressure.

[0056] From the above state, the chuck table 10 and the wafer W held thereon are moved along the X-axis direction by an X-axis moving mechanism (not shown) and positioned below the pair of left and right cutting units 30, and the front surface of the wafer W is imaged by the camera 31 of each cutting unit 30. When an image is obtained by imaging the front surface of the wafer W by the camera 31, a planned division line L1 (see FIG. 2) to be cut is detected by image processing such as pattern matching processing based on the image.

[0057] As described above, when the planned dividing line L1 of the wafer W is detected, the position in the Y-axis direction (indexing feed direction) of the cutting blade 32 (see Figure 1) of each cutting unit 30 is indexed by each Y-axis moving mechanism 50, and the position of each cutting blade 32 in the Y-axis direction is aligned with the position of the planned dividing line L1 to be cut.

[0058] Then, from the above state, the cutting blade 32 of each cutting unit 30 is rotated at high speed, and is lowered by a predetermined cutting depth by each Z-axis moving mechanism 40, and the chuck table 10 and the wafer W held thereon are moved in the X-axis direction (cutting feed direction) by an X-axis moving mechanism (not shown). Then, the wafer W is cut along the division line L1 by the cutting blade 32 of each cutting unit 30, and when such an operation is performed for all the division lines L1 in one direction, the chuck table 10 and the wafer W held thereon are rotated by 90° by a rotation mechanism (not shown), and the wafer W is cut along the division line L2 (see FIG. 2) in the other direction perpendicular to the division line L1 where cutting has been completed. In addition, in the cutting process of the wafer W by the cutting blade 32, cutting water (pure water) is sprayed toward the cutting blade 32.

[0059] Then, when the wafer W is divided into a plurality of pieces along the grid-like division lines L1, L2 as described above, the wafer W is cleaned by the cleaning unit 60 (step S8 in FIG. 9). That is, the wafer W is sucked and held by the suction pad 84 of the second transport means 80 and transported from the chuck table 10 to the cleaning unit 60, and placed on the holding surface of the cleaning table 61 of the cleaning unit 60 with the dicing tape T facing down. Then, similarly to the above, the wafer W is sucked and held on the holding surface of the cleaning table 61, and as shown in FIG. 5, water (cleaning water) is sprayed toward the center of the wafer W from the nozzle 62 located above the center of the wafer W, and the cleaning table 61 is rotated together with the wafer W at a predetermined speed around the axis center in the direction of the arrow in FIG. 6 by the servo motor 64.

[0060] Then, the cutting debris adhering to the upper surface of the wafer W is washed away by the water (cleaning water), but since the entire upper surface of the wafer W has been determined to be hydrophilic as described above by the hydrophilicity determination method of the present invention, the cutting debris is washed away together with the cleaning water and does not adhere to the upper surface of the wafer W.

[0061] As described above, when the entire upper surface of the wafer W is cleaned with cleaning water, the wafer W is sucked and held by the suction pad 84 of the second transport means 80 and transferred from the cleaning unit 60 to the carry-in / out means 7. Then, the carry-in / out means 7 to which the wafer W has been transferred holds the wafer W and stores the wafer W in the cassette 6 (step S9 in FIG. 9), and the determination of the hydrophilicity of the wafer W and the cutting process are completed (step S10 in FIG. 9).

[0062] As is clear from the above explanation, according to the method for determining the hydrophilicity of a wafer W of the first invention, if there is a non-white portion in the differential image formed by the difference in brightness between the first image captured in the first imaging process and the second image captured in the second imaging process, it is determined that the entire upper surface of the wafer W is not hydrophilic, and if the differential image is pure white, it is determined that the entire upper surface of the wafer W is hydrophilic. Therefore, an effect is obtained in which it is possible to easily confirm whether or not the entire upper surface of the wafer W is hydrophilic.

[0063] Furthermore, according to the cutting device 1 of the present invention, the method for determining the hydrophilicity of the wafer W is used to confirm that the entire surface of the wafer W is hydrophilic before performing a predetermined processing on the wafer W. Therefore, when the surface of the wafer W is cleaned with cleaning water in the cleaning unit 60 after processing, cutting debris generated by the cutting processing of the wafer W is reliably washed away by the cleaning water, and the effect is obtained that the adhesion of cutting debris to the upper surface of the wafer W after processing can be reliably prevented.

[0064] <Second Invention> Next, a method for determining the hydrophilicity of a wafer W according to the second aspect of the present invention will be described. This method is also carried out by the cutting device 1 shown in FIG. 1. As shown in FIG. 10, this method includes the following steps: 1) Water film formation process 2) Reflected light reception process 3) Judgment process The above steps are carried out in this order to determine whether or not the entire upper surface of the wafer W is hydrophilic. Here, 1) the water film forming step, 2) the reflected light receiving step, and 3) the determination step in the determination method according to the second invention will be described below with reference to Figs.

[0065] 1) Water film formation process: The water film forming process is a process in which a water film f shown in FIG. 6 is formed over the entire upper surface of the wafer W held on the cleaning table 61 of the cleaning unit 60 shown in FIG. 1. In this water forming process, the wafer W is held by suction on the holding surface of the cleaning table 61 with the dicing tape T facing down (step S21 in FIG. 14).

[0066] From the above state, a predetermined amount of water is dropped onto the center of the upper surface of the wafer W, and the wafer W is rotated around its axis at a predetermined speed, whereby the water supplied to the center of the upper surface of the wafer W spreads evenly toward the outer periphery of the wafer W due to the centrifugal force caused by the rotation of the wafer W, and a water film f of uniform thickness is formed on the upper surface of the wafer W (step S22 in FIG. 14). This water film forming step is the same as the water film forming step in the determination method according to the first invention (see FIGS. 5 and 6).

[0067] 2) Reflected light reception process: 11, the reflected light receiving step is a step in which the cleaning table 61 and the wafer W held thereon are rotated around the axis center by the servo motor 64 in the direction of the arrow in the drawing at a predetermined speed, the reflective sensor 110 is moved above the wafer W in a horizontal direction parallel to the upper surface of the wafer W by the horizontal movement mechanism 120, and the measurement light La projected from the light projecting unit 111 of the reflective sensor 110 toward the upper surface of the wafer W is reflected by the upper surface of the wafer W and / or a water film f and the reflected light Lb is received by the light receiving unit 112 (step S23 in FIG. 14). Specifically, the reflective sensor 110 measures the amount of reflected light Lb received by the light receiving unit 112 while moving horizontally in the radial direction (to the right in FIG. 11) toward the outer periphery of the wafer W from the position where the measurement light La emitted from the light projecting unit 111 is irradiated to the center O of the wafer W as a starting point. Here, the reflective sensor 110 is electrically connected to the control unit 90, and the amount of reflected light Lb measured by the reflective sensor 110 is transmitted to the control unit 90 and stored in a memory. In Fig. 11, the same elements as those shown in Fig. 6 are denoted by the same reference numerals, and a repeated description of them will be omitted.

[0068] 3) Judgment process: The determination step is a step in which the determination unit 92 of the control unit 90 determines whether the upper surface of the wafer W is hydrophilic or not based on the amount of reflected light Lb received by the light receiving unit 112 of the reflective sensor 110. Specifically, the determination unit 92 determines whether the amount of reflected light Lb received by the light receiving unit 112 of the reflective sensor 110 is higher or lower than a preset threshold value (step S24 in FIG. 14). For example, as shown in FIG. 12(a), when a water film f of uniform thickness is formed over the entire upper surface of the wafer W, as shown in FIG. 12(b), the amount of reflected light Lb received by the light receiving unit 112 of the reflective sensor 110 indicates a constant value higher than the threshold value along the radial direction of the wafer W (step S24: Yes), so that the determination unit 92 determines that the entire upper surface of the wafer W is hydrophilic and performs cutting processing on the wafer W (step S25 in FIG. 14). The reflective sensor 110, the horizontal movement mechanism 120, the servo motor 64 which is a rotation mechanism for the cleaning table 61, and the determination section 92 of the control section 90 constitute a determination unit.

[0069] On the other hand, when peeling occurs in a part of the water film f formed on the upper surface of the wafer W as shown in Fig. 13(a), the amount of reflected light Lb received at the peeled part of the water film f is lower than the threshold value as shown in Fig. 13(b) (step S24: No). In such a case, the determination unit 92 determines that the upper surface of the wafer W is not hydrophilic, returns the wafer W to the cassette 6 (see Fig. 1) (step S29 in Fig. 14), and ends the subsequent processing of the wafer W (step S28 in Fig. 14). Note that the wafer W that is determined to have no hydrophilic surface and returned to the cassette 6 is irradiated with ultraviolet light or plasma to impart hydrophilicity to the surface, and then the presence or absence of hydrophilicity as described above is determined again, or the wafer W is removed from the processing target. As shown in Figures 11 to 13, the reflective sensor 110 has the light-projecting unit 111 and the light-receiving unit 112 arranged at a distance from each other, but this is not limited to this, and the sensor may be a coaxial reflective sensor in which the light-projecting unit 111 and the light-receiving unit 112 are arranged on the same axis.

[0070] In this embodiment, the judgment unit 92 provided in the control unit 90 automatically judges whether or not the upper surface of the wafer W is hydrophilic based on the amount of reflected light Lb received by the light receiving unit 112 of the reflective sensor 110. However, the operator may visually check the amount of received light displayed on a display unit (not shown) to judge whether or not the upper surface of the wafer W is hydrophilic.

[0071] If the entire top surface of the wafer W is determined to be hydrophilic by the above method for determining the hydrophilicity of the wafer W (step S24: Yes in Figure 14), cutting is performed on the wafer W as described above (step S25 in Figure 14). However, since this cutting has been described above, a repeated explanation of it will be omitted.

[0072] Then, when the wafer W is divided into a plurality of pieces along the lattice-shaped division lines L1, L2 (see FIG. 2) by the cutting process, the wafer W is cleaned by the cleaning unit 60 (step S26 in FIG. 14). Since the cleaning of the wafer W has been described above, a repeated description thereof will be omitted. However, since the entire upper surface of the wafer W has been determined to be hydrophilic by the hydrophilicity determination method according to the second invention as described above, cutting debris is washed away together with the cleaning water and does not adhere to the upper surface of the wafer W.

[0073] Then, when the entire upper surface of the wafer W has been cleaned with the cleaning water, the wafer W is sucked and held by the suction pad 84 of the second transport means 80 shown in Fig. 1 and transferred from the cleaning unit 60 to the transfer means 7. The transfer means 7 to which the wafer W has been transferred holds the wafer W and stores the wafer W in the cassette 6 (step S27 in Fig. 14), and the determination of the hydrophilicity of the wafer W and the cutting process are completed (step S28 in Fig. 14).

[0074] As is clear from the above explanation, according to the method of determining the hydrophilicity of a wafer W of the second invention, if the amount of light received by the light receiving portion 112 of the reflective sensor 110 in the reflected light receiving process indicates a value higher than a predetermined threshold value, it is determined that the entire upper surface of the wafer W is hydrophilic, and if at least a portion of the amount of light received indicates a value lower than the threshold value, it is determined that the entire upper surface of the wafer W is not hydrophilic. Therefore, it is possible to easily confirm whether or not the entire upper surface of the wafer W is hydrophilic.

[0075] In addition, after confirming that the entire surface of the wafer W is made hydrophilic by the method for determining the hydrophilicity of the wafer W according to the second invention, a predetermined cutting process is performed on the wafer W. Therefore, when the surface of the wafer W is cleaned with cleaning water in the cleaning unit 60 after the cutting process, the cutting debris generated by the cutting process of the wafer W is reliably washed away by the cleaning water, and the adhesion of the cutting debris to the upper surface of the wafer W after the cutting process can be reliably prevented.

[0076] Although the present invention has been described above as being applied to a cutting device, the present invention can be similarly applied to any other processing devices such as grinding devices and polishing devices other than cutting devices.

[0077] In addition, the present invention is not limited to the application of the embodiments described above, and various modifications are possible within the scope of the claims and the technical ideas described in the specification and drawings. [Explanation of symbols]

[0078] 1: cutting device (processing device), 2: base, 2a: opening of base, 3, 4: gate-shaped column, 5: cassette support stand, 6: cassette, 7: loading / unloading means, 8: cover, 9: expandable cover, 10: chuck table, 20: first conveying means, 21: guide rail, 22: arm, 23: shaft, 24: suction pad, 30: cutting unit (processing unit), 31: camera, 32: cutting blade, 40: Z-axis movement mechanism, 41: Z-axis guide rail, 42: Z-axis base, 43: Z-axis ball screw, 44: Z-axis servo motor, 50: Y-axis movement mechanism, 51: Y-axis base, 52: Y-axis guide rail, 53: Y-axis ball screw, 54: Y-axis servo motor, 60: cleaning unit, 61: cleaning table, 62: nozzle, 63: Porous member, 64: Servo motor (rotation mechanism), 65: Encoder, 66: rotating shaft, 67: rotary joint, 68: connecting passage, 69: piping, 69a, 69b: branch pipe, 70: variable orifice, 71: suction source, 72: variable orifice, 73: air supply source, 74: pressure gauge, 75: rotating shaft, 76: servo motor, 77: Encoder, 78: Swivel arm, 79: Water supply source, 80: Second conveying means, 81: guide rail, 82: arm, 83: shaft, 84: suction pad, 90: control unit, 91: differential image forming unit, 92:: determination unit, 100: camera, 101: lighting equipment, 110: reflective sensor, 111: light projecting unit, 112: light receiving unit, 120: horizontal movement mechanism, D: device, f: water film, L1, L2: planned division lines, La: measurement light, Lb: reflected light, O: center of wafer, T: dicing tape, V1, V2: on-off valve, W: wafer

Claims

1. A method for determining whether or not an entire top surface of a wafer is hydrophilic, comprising the steps of: a first imaging step of imaging the entire upper surface of the wafer with a camera; a water film forming step of supplying water in an amount sufficient to form a water film on the entire upper surface of the wafer and rotating the wafer at a predetermined rotation speed around the center of the wafer; a second imaging step of imaging the entire upper surface of the wafer with the camera after the water film forming step; a differential image forming step of forming a differential image based on a difference between a brightness of a first image captured in the first imaging step and a brightness of a second image captured in the second imaging step; a determining step of determining that the entire upper surface of the wafer is not hydrophilic if there is a non-white portion in the difference image, and determining that the entire upper surface of the wafer is hydrophilic if the difference image is pure white; A method for determining the hydrophilicity of a wafer comprising:

2. A method for determining whether or not an entire top surface of a wafer is hydrophilic, comprising the steps of: a water film forming step of supplying water in an amount sufficient to form a water film on the entire upper surface of the wafer and rotating the wafer at a predetermined rotation speed around the center of the wafer; a reflected light receiving step of receiving measurement light projected from the reflective sensor toward the wafer and reflected by the wafer or water on the wafer while moving the reflective sensor in a direction parallel to the wafer's upper surface after the water film forming step; a determining step of determining that the entire upper surface of the wafer is hydrophilic when the amount of light received by the reflective sensor in the reflected light receiving step indicates a value higher than a preset threshold, and determining that the entire upper surface of the wafer is not hydrophilic when at least a portion of the amount of light received indicates a value lower than the threshold; A method for determining the hydrophilicity of a wafer comprising:

3. 3. A processing apparatus comprising: a chuck table for holding a wafer; a processing unit for processing the wafer held on the chuck table; a cleaning unit for rotating the wafer held on a cleaning table and spraying cleaning water onto an upper surface of the wafer to clean the upper surface of the wafer; and a control unit, the processing apparatus processing the wafer by the processing unit after carrying out the method for determining hydrophilicity of a wafer according to claim 1 or 2, The processing apparatus includes a judgment unit that supplies water to the center of a wafer held on the chuck table or the cleaning table, rotates the chuck table or the cleaning table to form a water film on the entire top surface of the wafer, and then judges whether the entire top surface of the wafer is hydrophilic or not.

4. The judgment unit is a camera capable of capturing an image of the entire top surface of a wafer held on the chuck table or the cleaning table; a differential image forming unit that forms a differential image by a difference between a brightness of a first image captured by the camera of the wafer held on the chuck table or the cleaning table and a brightness of a second image captured by the camera of the wafer; a determination unit that determines that the entire upper surface of the wafer is not hydrophilic if there is a non-white portion in the difference image, and that the entire upper surface of the wafer is hydrophilic if the difference image is pure white; The processing apparatus according to claim 3 .

5. The judgment unit is a reflective sensor including a light projecting unit that projects a measurement light toward an upper surface of the wafer held on the chuck table or the cleaning table, and a light receiving unit that receives light reflected by the upper surface of the wafer or by water on the upper surface of the wafer; a horizontal movement mechanism for moving the reflective sensor in a direction parallel to an upper surface of the wafer; a rotation mechanism that rotates the chuck table or the cleaning table; a determining unit which determines that the entire upper surface of the wafer is hydrophilic when the amount of light received by the light receiving unit indicates a value higher than a preset threshold value by moving the reflective sensor horizontally by the horizontal moving mechanism while rotating the chuck table or the cleaning table, and determines that the entire upper surface of the wafer is not hydrophilic when at least a part of the amount of light received indicates a value lower than the threshold value; The processing apparatus according to claim 3 .

Images