JP5505790B2 - Inspection method using dicing machine - Google Patents

Description

  The present invention relates to an inspection method using a dicing apparatus, and more particularly, to an inspection method for a dicing apparatus that cuts a transparent / semi-transparent wafer into dice using a blade.

  The dicing apparatus is an apparatus that obtains chips from a wafer by cutting the wafer along a street with a blade having abrasive grains fixed to the outer peripheral portion and cutting the wafer into dice. In this dicing apparatus, chipping occurs on the street of the wafer due to wear of the blade, and the position of the groove (kerf) cut by the blade shifts from the center of the street due to thermal deformation of the blade. For this reason, the dicing device performs a kerf check of the blade at a preset timing. In other words, the groove cut with the blade is irradiated with illumination light, the groove is imaged with a camera, the image signal is subjected to image processing or visual inspection, and the groove position, width, presence of chipping, etc. are checked. doing. In general, the kerf check is performed by cutting a predetermined number of streets at intervals of one chip and then performing a kerf check on the groove processed in the last street.

  Patent Document 1 discloses a kerf check method in a step-cut method of a twin spindle dicer. According to this kerf check method, an uncut street is cut to a predetermined depth by the first blade, and the uncut street is cut to a predetermined depth by the second blade, and the two grooves thus cut are cut. A kerf check of the first blade and the second blade is performed by inspection.

  According to the kerf check method of Patent Document 1, when performing the kerf check of the second blade, the uncut street is cut and the kerf check is performed. Therefore, the groove cut by the first blade and the second blade There is an advantage that an accurate kerf check can be performed without overlapping the groove cut by the blade.

  Recently, transparent and semi-transparent wafers mainly made of silicon carbide have been produced, and similar kerf checks have been performed on such transparent and semi-transparent wafers.

JP 2001-129822 A

  In the wafer kerf check, in the case of an opaque wafer, the entire groove imaged and processed by the camera is displayed clearly, for example, in black, so that the groove shape is highly visible and the kerf check can be performed accurately. .

  However, in the above-mentioned transparent / semi-transparent wafer, the black color of the groove is unclear, and even the part that seems to be a groove is almost the same as the color (white) of the part other than the groove (chip, street before cutting). Since they are displayed in the same color, there is a problem that it is difficult to accurately perform the kerf check. This problem is considered to occur when illumination light incident on a transparent / translucent wafer is reflected inside the wafer.

  The present invention has been made in view of such circumstances, and various inspections such as a kerf check can be performed using internal reflection of illumination light generated inside a transparent / translucent wafer. It aims at providing the inspection method by a dicing apparatus.

  In order to achieve the above object, the inspection method using the dicing apparatus of the present invention cuts a plurality of streets provided on a transparent / semi-transparent wafer at a predetermined interval with a blade, thereby forming a cutting groove. In the inspection method using the dicing apparatus that processes the wafer, the groove is irradiated with illumination light from the upper surface of the groove processed by the blade, and the groove is irradiated with illumination light obliquely from above the side surface of the groove, Illumination light incident on the inside of the wafer from the adjacent groove adjacent to the groove or from the surface of the wafer is reflected inside the wafer and the light emitted to the outside from the adjacent groove and the groove is imaged with a camera, The wafer is inspected based on an image picked up by a camera.

  The present invention is an invention of an inspection method using a characteristic that illumination light incident on a wafer from other than a kerf check groove, which is an inspection target part, returns from the kerf check groove to the camera side. According to the present invention, defects in the pattern structure inside the wafer, recognition of internal defects (interfaces such as cracks and vacancies), and processing state (blade tip state, blate center position: kerf check) that could not be carried out conventionally Recognition and positioning can be inspected based on images of grooves and adjacent grooves projected by internally reflected light. Therefore, according to the present invention, various inspections can be performed by utilizing the internal reflection of the illumination light generated inside the transparent / translucent wafer.

  By the way, the inventor earnestly obtained the following knowledge as a result of earnestly examining a kerf check improvement measure for transparent and translucent wafers. That is, when illumination light for kerf check is irradiated onto a transparent / semi-transparent wafer, the illumination light is also irradiated to the groove adjacent to the groove (hereinafter referred to as the adjacent groove) in addition to the groove for kerf check. The A part of the illumination light irradiated to the adjacent groove enters the wafer from the adjacent groove because the wafer is transparent / translucent. Then, internal reflection is performed inside the wafer, and part of the reflected light is emitted outward from the kerf check groove. The emitted light and the light reflected from the groove for kerf check interfere with each other, and the camera captures the interference light. As a result, in the image after image processing, the kerf check groove is not displayed as clear black, but is displayed in a color including white. In other words, it was experimentally determined that the light incident on the inside of the wafer from the adjacent groove and internally reflected, and the light emitted outward from the kerf check groove out of the internally reflected light was the cause of the kerf check failure. . Actually, even if it is a groove | channel, the part displayed substantially white is a part near an adjacent groove | channel, and was displayed along the adjacent groove | channel. Moreover, the part away from the adjacent groove | channel among the grooves was displayed black.

  The present invention performs kerf check by extracting the groove by taking a difference between an image when the illumination light incident on the wafer is shielded from a region other than the groove region and an image when the illumination light is not shielded. Is preferred.

  Thereby, according to the present invention, since the groove for kerf check can be extracted even for a transparent / semi-transparent wafer, kerf check can be performed accurately.

  In the present invention, it is preferable to detect the internal defect of the wafer by comparing the luminance of the image with the luminance of the image having no internal defect.

  When the wafer has internal defects (interfaces such as cracks and vacancies), incident light other than the kerf check groove does not return to the camera side from the kerf check groove even if it is reflected inside the wafer. That is, in the vicinity of the groove where the internal defect is generated, the inside of the groove is changed to black, so that the brightness is lower than that of the image without the internal defect. In the present invention, the internal defect of the wafer can be inspected by detecting this change in brightness (discoloration).

  In the conventional inspection technique, only the appearance of the part to be inspected is recognized by image processing, but in the present invention, the internal state of the wafer can be inspected by using the internally reflected light.

  In the present invention, it is preferable to inspect chips of the wafer based on an internal pattern image of the wafer projected on the wall surface of the groove by internal reflection of the wafer.

  Thereby, this invention can test | inspect the soundness of a chip | tip during the dicing process of a wafer.

  In the conventional inspection technique, only the appearance of the part to be inspected is recognized by image processing, but in the present invention, the state of the chip can be inspected by using the internally reflected light.

  In the present invention, it is preferable to inspect the blade edge state of the blade based on a grinding mark image of the blade reflected on the wall surface of the groove by internal reflection of the wafer.

  The present invention evaluates the blade edge state of the flade using an image of a blade grinding mark projected on the groove wall surface by internal reflection, that is, an image with a clear contrast difference improved by internal reflection. Therefore, this invention can test | inspect the soundness of a blade during the dicing process of a wafer.

  In the present invention, it is preferable to measure the cutting end position of the groove based on a change in luminance of the image of the groove.

  The present invention relates to cutting control using the discoloration of the groove, and the cutting end position can be measured by recognizing the luminance state of the groove (adjacent groove).

  According to the inspection method using the dicing apparatus of the present invention, since the internal reflection of the illumination light generated inside the transparent / semi-transparent wafer is used, various inspections can be performed.

Plan view showing main configuration of twin spindle dicer Side view of twin spindle dicer shown in FIG. Schematic structure diagram showing the configuration of the ITV camera Explanatory drawing of kerf check method by dicing machine Explanatory drawing of kerf check method by dicing machine Explanatory drawing of the image processing method for performing kerf check Explanatory drawing of internal defect inspection method by dicing machine Explanatory drawing of image processing method for internal defect inspection Explanatory drawing of internal structure inspection method by dicing machine Explanatory drawing of image processing method for internal structure inspection Explanatory drawing of the image processing method for performing blade edge state inspection Explanatory drawing of the image processing method for inspecting the cutting end position of the groove

  Hereinafter, preferred embodiments of an inspection method using a dicing apparatus according to the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a plan view showing a main configuration of a twin spindle dicer 10 to which the present invention is applied, and FIG. 2 is a side view of the twin spindle dicer 10 shown in FIG.

  The twin spindle dicer 10 shown in these drawings includes a wafer table 12 that holds a wafer W, a pair of cutting units 14A and 14B that cut the wafer W held on the wafer table 12, and a pair of imaging that images the wafer W. The units 16A and 16B, a drive system that constitutes the twin spindle dicer 10, and a control device 18 that performs overall control of the control system.

  The wafer table 12 has a disk shape as shown in FIG. 1 and holds the back surface of the wafer W by vacuum suction. The wafer table 12 is reciprocated along the X-axis direction in FIG. 1 by being driven by a feed mechanism (not shown). Further, the wafer table 12 is rotated around a central axis (θ axis) by being driven by a rotation driving mechanism (not shown).

  The wafer W is held on the wafer table 12 while being mounted on a wafer frame (not shown). That is, the wafer W is held on the wafer table 12 in a state of being attached to a wafer sheet attached to the wafer frame.

  The cutting units 14A and 14B are provided with blades 20A and 20B for cutting the wafer W, respectively. The blades 20A and 20B are connected to spindles 22a and 22b of motors 22A and 22B, respectively. The cutting units 14A and 14B are individually moved in the Y-axis direction in FIG. 1 and the Z-axis direction in FIG. 2 by being driven by a spindle moving mechanism.

  As shown in FIG. 2, the spindle moving mechanism includes a pair of Y carriages 24A and 24B. The pair of Y carriages 24A and 24B are both slidably supported by guide rails 26 and 26 disposed along the Y-axis direction. And it is slid individually along the Y-axis direction in FIGS. 1 and 2 by being driven by a slide drive means (not shown) (for example, a linear motor).

  On the Y carriages 24A and 24B, Z-axis direction moving mechanisms 28A and 28B each including a linear guide and a driving unit (not shown) are installed. The Z-axis direction moving mechanisms 28A and 28B drive the Z carriages 30A and 30B along the Z-axis direction in FIG. Motor brackets 32A and 32B are attached to the front ends of the Z carriages 30A and 30B, and the motors 22A and 22B are attached to the motor brackets 32A and 32B.

  The spindle moving mechanism is configured as described above, and the cutting units 14A and 14B are moved in the Y-axis direction and the Z-axis direction, respectively, by being driven by the spindle moving mechanism. That is, the cutting units 14A and 14B are moved along the Y-axis direction by sliding the Y carriages 24A and 24B along the guide rails 26 and 26, and the Z carriages 30A and 30B of the Z-axis direction moving mechanisms 28A and 28B. Is moved (moved up and down) along the Z-axis direction.

  The cutting units 14A and 14B that move in this way have the cutting pitch varied by moving along the Y-axis direction, and the cutting depth varies by moving along the Z-axis direction.

  The imaging units 16A and 16B include ITV cameras 34A and 34B. As shown in FIG. 1, the ITV cameras 34A and 34B are held by camera holders 36A and 36B, and the camera holders 36A and 36B are fixed to motor brackets 32A and 32B. The ITV cameras 34 </ b> A and 34 </ b> B take an image of the upper surface of the wafer W held on the wafer table 12 and output the image data to an image processing device (image processing means) 38.

  The image processing device 38 performs image processing on the obtained image data and performs a kerf check of grooves cut by the blades 20A and 20B, inspection of defects inside the wafer W (interfaces such as cracks and holes), and patterns inside the wafer W. Inspection of structural defects and inspection of groove processing state (blade tip state, blade center position) are performed. Details of this inspection will be described later.

  In the kerf check by the image processing device 38, the position and width of the grooves cut by the blades 20A and 20B, the presence / absence of chipping, and the like are measured. Further, by outputting an image signal from the image processing device 38 to the monitor 40, the wafer W is displayed on the screen of the monitor 40.

  FIG. 3 is a schematic structural diagram showing the configuration of the ITV cameras 34A and 34B.

  The ITV cameras 34A and 34B include two half mirrors 42 and 44 in the vertical direction. A light 46 is disposed above the half mirrors 42 and 44 in the vertical direction, and illumination light from the light 46 is applied to the wafer W via the half mirrors 42 and 44. The illumination angle of the illumination light may be from the upper surface (directly above) of the groove, or may be an oblique angle from above the side surface of the groove.

  An image sensor 48 having a low magnification optical system (L) is disposed on the side of the half mirror 42, and an image sensor 50 having a high magnification optical system (H) is disposed on the side of the half mirror 44. Is arranged. That is, according to the ITV cameras 34A and 34B, the illumination light from the light 46 is irradiated onto the wafer W through the half mirrors 42 and 44, and the reflected light from the wafer W is reduced through the half mirrors 44 and 42. An image is picked up by the image pickup device 48 of magnification. Similarly, the reflected light from the wafer W is imaged by the high-magnification imaging device 50 via the half mirror 44. In addition, the code | symbol 52 of FIG. 3 is the groove | channel for a kerf check cut | disconnected by the blade 20A (20B). The groove 52 is a V-shaped cut, but the angle and shape of the groove are not limited thereto.

  The control device 18 shown in FIGS. 1 and 2 controls the drive system of the wafer table 12 and the cutting units 14A and 14B. The control device 18 controls the wafer table 12 and the cutting units 14A and 14B according to a preset cutting pattern, cuts the wafer W held on the wafer table 12 along the street, and cuts the grooves 52 in FIG. 3 into the wafer. Process into W. Further, the above-described inspection such as a kerf check is performed in accordance with a timing set in advance in the data or an instruction from the operator. That is, the control device 18 controls the ITV cameras 34A and 34B and the image processing device 38 at the time of inspection such as kerf check.

  Next, an inspection method using the twin spindle dicer 10 configured as described above will be described. In the inspection method of the embodiment, a transparent / translucent wafer is used as the wafer W.

  First, a kerf check method using a dicing apparatus will be described.

  In this inspection method, as shown in FIG. 4, the illumination light incident on the wafer W from other than the region of the groove 52 for kerf check is shielded by the shutter 54, and the shutter 54 is not shielded as shown in FIG. This is a method of extracting the groove 52 and performing a kerf check by taking the difference from the image of.

  The image shown in FIG. 6A is an image obtained by taking the difference between the two images. In the case where the image is not shielded by the shutter 54, the light reflected from the adjacent groove 52A and internally reflected returns to the camera 34A (34B) side from the kerf check groove 52, as in the image of FIG. 6B. The color on the adjacent groove 52A side is white, and the color on the opposite side is black. Further, the image when shielded by the shutter 54 has a black kerf check groove 52 because internal reflection does not occur as in the image of FIG. 6C. The control device 18 takes the difference between these two images, normalizes it as shown in FIG. 6D, and binarizes this image to obtain the image shown in FIG. 6E. Since this image is black with white stripes in the center, the control device 18 extracts the white line of this image as a groove 52 for kerf check.

  Therefore, according to this kerf check inspection method, the kerf check of the transparent / semi-transparent wafer W can be accurately performed using the internally reflected light of the wafer W.

  Next, an internal defect inspection method for the wafer W using a dicing apparatus will be described.

  This inspection method is a method for detecting internal defects (interfaces such as cracks and vacancies) of a wafer by comparing the brightness of an image of a groove with the brightness of an image having no internal defects.

  As shown in the cross-sectional view of the wafer W in FIG. 7, when the wafer W has an internal defect 56, the light incident on the wafer W from other than the kerf check groove 52 is reflected inside the wafer W. Since it is blocked by 56, it does not return to the camera side from the groove 52 for kerf check. That is, in the vicinity of the groove 52 where the internal defect 56 is generated, the inside of the groove 52 is changed to black as shown in FIGS. 8A, 8B, and 8C. The brightness is small in comparison. In this inspection method, since this luminance change (discoloration) is detected, the internal defect 56 of the wafer W can be inspected.

  Therefore, according to this internal defect inspection method, the internal state of the wafer W can be inspected using the internally reflected light of the wafer W.

  Next, a chip inspection method for the wafer W by the dicing apparatus will be described.

  This inspection method is based on the internal pattern image 55 of the wafer W shown in FIGS. 10A, 10B, and 10C, which is displayed on the wall surface 53 of the groove 52 by internal reflection of the wafer W as shown in FIG. This is a method for inspecting the chip T of the wafer W. Thereby, the soundness of the chip | tip T can be test | inspected during the dicing process of the wafer W. FIG.

  Therefore, according to this chip inspection method, the state of the chip T can be inspected using the internally reflected light of the wafer W.

  Next, a method for inspecting the blade edge state of the blade 20A (20B) by the dicing apparatus will be described.

  This inspection method is a method for inspecting the blade tip state of the blade 20A (20B) based on the grinding mark image of the blade 20A (20B) projected on the wall surface of the groove 52 by internal reflection of the wafer W.

  That is, as shown in FIG. 11A, as shown in the image of the grinding mark of the blade 20A (20B) projected on the wall surface of the groove 52 by the internal reflection of the wafer W, that is, the extracted image of FIG. The blade edge state of the flade 20A (20B) is evaluated using an image in which the contrast difference improved by internal reflection is clear.

  Therefore, according to this inspection method, the soundness of the blade 20A (20B) can be inspected using the internally reflected light of the wafer W.

  Next, a method for inspecting the cutting end position of the groove by the dicing apparatus will be described.

  This inspection method is a method in which the cutting end position of the groove is measured and inspected based on the change in luminance of the groove image.

  As shown in the image of FIG. 12, the groove wall for the kerf check has a white groove wall on the adjacent groove 52B side due to internal reflection of light incident from the adjacent groove 52B. In the adjacent grooves 52A and 52B, the groove wall on the edge E side becomes black as it approaches the edge E of the wafer W. The cause of this phenomenon is that the illumination light does not enter the wafer W from the edge E. In other words, the adjacent groove 52A becomes black from the position beyond the cutting end portion of the adjacent groove 52B. The same applies to the adjacent groove 52B. That is, by detecting the black generation position of the adjacent groove 52A, the cutting end position of the adjacent groove 52B can be measured and inspected.

  This inspection method is an invention related to cutting control using the discoloration of the groove, and the cutting end position can be measured by recognizing the luminance state of the groove (adjacent groove).

  DESCRIPTION OF SYMBOLS 10 ... Twin spindle dicer, 12 ... Wafer table, 14A, 14B ... Cutting unit, 16A, 16B ... Imaging unit, 18 ... Control apparatus, 20A, 20B ... Blade, 22A, 22B ... Motor, 22a, 22b ... Spindle, 24A, 24B ... Y carriage, 26 ... guide rail, 28A, 28B ... Z axis direction moving mechanism, 30A, 30B ... Z carriage, 32A, 32B ... motor bracket, 34A, 34B ... ITV camera, 36A, 36B ... camera holder, 38 ... Image processing apparatus, 40 ... monitor, 42, 44 ... half mirror, 46 ... light, 48, 50 ... imaging device, 52 ... kerf check groove, 52A ... adjacent groove, 54 ... shutter, 56 ... internal defect

Claims (6)

In an inspection method by a dicing apparatus that cuts a plurality of streets provided on a transparent / translucent wafer at a predetermined interval with a blade to process a cutting groove into the wafer,
Irradiate the illumination light from the upper surface of the groove processed by the blade, and irradiate the illumination light obliquely from above the side surface of the groove,
Illumination light incident on the inside of the wafer from the adjacent groove adjacent to the groove or from the surface of the wafer is reflected inside the wafer, and the light emitted outside from the adjacent groove and the groove is imaged with a camera.
An inspection method using a dicing apparatus, wherein the wafer is inspected based on an image captured by the camera.   The kerf check is performed by extracting the groove by taking a difference between an image when the illumination light incident on the wafer is shielded from a region other than the groove region and an image when the illumination light is not shielded. Inspection method using a dicing machine.   The inspection method using a dicing apparatus according to claim 1, wherein the internal defect of the wafer is detected by comparing the brightness of the image with the brightness of an image having no internal defect.   The inspection method by a dicing apparatus according to claim 1, wherein a chip of the wafer is inspected based on an internal pattern image of the wafer projected on the wall surface of the groove by internal reflection of the wafer.   The inspection method by the dicing apparatus according to claim 1, wherein the blade edge state is inspected based on a grinding mark image of the blade projected on the wall surface of the groove by internal reflection of the wafer.   The inspection method by the dicing apparatus according to claim 1, wherein a cutting end position of the groove is measured based on a change in luminance of the image of the groove.

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