PROCESSING METHOD FOR A WAFER

Abstract

A processing method for a wafer (11) for processing a wafer (11) in which a component (15) having multiple raised areas (17) is formed in each of the regions of a front surface (11a) divided by multiple intersecting parting lines (13) formed in an intersecting manner, the processing method for a wafer (11) comprising: a cut groove formation step (23) for forming cut grooves (23) having a depth corresponding to a finished thickness of each of the component chips (27) by a cutting blade (14) along the parting lines from a front surface face of the wafer; a sealing step for sealing the front surface (11a) of the wafer (11) including the cut grooves (23) with a sealing material (20) after the cut groove formation step (23) has been performed;an alignment step for detecting an alignment mark through the sealing material (20) by means of a receiving means (18, 18a) for visible light from the front surface (11a) of the wafer (11) and detecting the parting line (13) to be laser-processed based on the alignment mark after the sealing step has been performed; a training step for a modified layer (25) wherein, in this training step, a laser beam (LB) of such a wavelength is emitted that it passes through the sealing material (20) along the parting lines (13) from the front surface (11a) of the wafer (11), wherein a focal point of the laser beam (LB) in the sealing material (20) is positioned in the cut grooves (23) to form modified layers (25) in the sealing material (20) in the cut grooves (23) after the alignment step has been performed;a grinding step for grinding the wafer (11) from a rear surface side (11b) of the wafer (11) to the finished thickness of each of the device chips (27) to expose the sealing material (20) in the cut grooves (23) after the formation step for a modified layer (25) has been performed; and a splitting step for applying an external force to the sealing material (20) in the cut grooves (23) and portions of the wafer (11), the modified layers (25) serving as the starting points of the split, into individual device chips (27), each of which has its front surface and four side surfaces surrounded by the sealing material (20) after the grinding step has been performed, wherein the alignment step is performed while an area to be received by the receiving means (18, 18a) for visible light is irradiated at an angle by an inclined light source (31).

Description

Technical field

[0001] The present invention relates to a processing method for a wafer for processing a wafer to form a 5S-shaped pack. Description of the state of the art

[0002] As a way to achieve miniaturization and higher density of various components such as large-scale integrated circuits (LSIs) and NAND flash memory, chip-size packages (CSPs) have been widely used and implemented in mobile phones, smartphones, and similar devices. Furthermore, in recent years, CSPs have evolved into CSPs where not only the front surface but all side surfaces of a chip are sealed with a sealing material; this is known as a 5S-shaped package.

[0003] The conventional 5S-shaped package is produced by the following steps. (1) Forming components (circuit) and external interconnect terminals, called protrusions, on a front surface of a semiconductor wafer (hereinafter sometimes referred to simply as the wafer). (2) Cutting the wafer along parting lines from a front surface of the wafer to form cut grooves, each having a depth corresponding to the finished thicknesses of each of the component chips. (3) Sealing the front surface of the wafer with a sealing material containing carbon black. (4) Grinding a rear surface of the wafer to a finished thickness of each of the component chips to expose the sealing material in the cut grooves. (5) Performing an alignment in which, since the front surface of the wafer is sealed with the sealing material containing carbon black, the sealing material is removed from a large section of the front surface of the wafer to expose the alignment markings such as target patterns, and the parting lines to be cut are detected based on the alignment markings. (6) Cutting the wafer along the division lines from the front surface of the wafer based on the orientation and dividing the wafer into 5S-shaped packs, each of which has its front surface and one side surface sealed with the sealing material.

[0004] Since the front surface of the wafer is sealed with the carbon black-containing sealing material as described above, the components and the like formed in the front surface of the wafer cannot be seen with the naked eye. To enable alignment by solving this problem, the present inventor has developed a technique in which, as described in the paragraph above, 5 As described, the sealing material is removed from the perimeter section of the front surface of the wafer to expose the alignment markers such as target patterns, and based on these target patterns, the parting line to be cut is detected so that alignment is carried out (see Japanese Disclosure No. 2013-074021 and Japanese Disclosure No. 2016-015438). PRESENTATION OF THE INVENTION

[0005] However, according to the alignment process described in the aforementioned patent documents, a step is required to remove the sealing material from the perimeter section of the wafer using a wide cutting blade attached to a spindle for edge cutting, instead of a cutting blade for parting. Replacing the cutting blade and removing the sealing material from the perimeter section by edge cutting is labor-intensive, resulting in low productivity.

[0006] Therefore, an objective of the present invention is to provide a processing method for a wafer in which an alignment step can be carried out by the sealing material containing carbon black, which is applied to coat a front surface of the wafer.

[0007] In accordance with one aspect of the present invention, a wafer machining method is provided for machining a wafer in which each of the components, having multiple raised areas, is formed in each of the regions of a front surface divided by multiple intersecting parting lines formed in an intersecting manner. The wafer machining method comprises: a cut groove forming step for creating cut grooves, each having a depth corresponding to the thickness of each of the component chips, by a cutting blade along the parting lines from a front surface face of the wafer; a sealing step for sealing the front surface of the wafer, including the cut grooves, with a sealing material after the cut groove forming step has been performed;an alignment step for detecting an alignment mark through the sealing material by means of a visible light receiving means from the front face of the wafer and detecting the parting line to be laser-processed based on the alignment mark after the sealing step has been performed; a training step for a modified layer for emitting a laser beam of such a wavelength that it passes through the sealing material along the parting lines from the front surface of the wafer, wherein a focal point of the laser beam is set in the sealing material in the cut groove to train modified layers in the sealing material in the cut grooves after the alignment step has been performed;A grinding step to grind the wafer from a rear surface face of the wafer to the finished thickness of each of the device chips to expose the sealing material in the cut grooves after the training step for a modified layer has been performed; and a division step to apply an external force to the sealing material in the cut grooves and portions of the wafer, with the modified layers serving as division start points, into individual device chips, each having the front surface and four side surfaces surrounded by the sealing material after the grinding step has been performed. The alignment step is performed while an area to be picked up by the visible light receiving means is irradiated at an angle by an inclined light source.

[0008] According to the processing method for a wafer of the present invention, while the wafer is irradiated with light through the inclined light source, the alignment mark formed in the wafer is detected through the sealing material by the visible light receiving means and the alignment can be carried out based on the alignment mark.

[0009] Therefore, the alignment step can be easily performed without removing the sealing material from the extensive section of the front surface of the wafer, as is the case in the prior art.

[0010] Accordingly, by emitting a laser beam of such a wavelength that it passes through the sealing material from the front surface of the wafer, with the focal point of the laser beam positioned in the cut grooves within the sealing material, it is possible to form the modified layers within the sealing material and then, by grinding the wafer from a rear surface to the finished thickness of each device chip, to expose the sealing material in the cut grooves, and by applying an external force to the sealing material, it is possible to divide the wafer into individual device chips, with the modified layers serving as the starting points of the division, each having a front surface and four side surfaces surrounded by the sealing material.

[0011] The above and other features, objectives and advantages of the present invention and the manner of its realization will become clearer and the invention itself will be understood by studying the following description and attached claims with reference to the attached figures, which show a preferred embodiment of the invention. List of characters Fig. Figure 1 is a perspective view of a semiconductor wafer; Fig. 2 is a perspective view showing a training step for a cut groove; Fig. Figure 3 is a perspective view showing a sealing step; Fig. Figure 4 is a section view showing an alignment step; Fig. 5A is a sectional view showing a training step for a modified layer; Fig. 5B is a partially enlarged cross-sectional view of a wafer after the training step for a modified layer has been performed; Fig. Figure 6 is a sectional view showing a grinding step; Fig. Figure 7 is a perspective view of a dividing device; Fig. 8A is a sectional view showing a division step; Fig. 8B is a sectional view showing the division step; and Fig. Figure 9 is a partially enlarged cross-sectional view of the wafer after the splitting step has been performed. DETAILED DESCRIPTION OF THE PREFERRED VERSION

[0012] One embodiment of the present invention is described in detail below with reference to the figures. Fig. Figure 1 shows a perspective view of a front surface of a semiconductor wafer (hereinafter simply referred to as wafer) 11, which is suitable for machining by a machining method of the present invention. In a front surface 11a of the semiconductor wafer 11 are several dividing lines (roads) 13 formed in a grid pattern and a building element 15 how an integrated circuit (IC) or an LSI is formed in each of the areas defined by the dividing lines 13 , which intersect orthogonally, are divided.

[0013] Each component 15 exhibits several electrode protrusions (hereinafter simply referred to as protrusions) 17 on its front surface, and the wafer 11 includes a component area on its front surface 19 , in which several components 15 , each of which involves several increases17 exhibit, are formed, and have a comprehensive marginal area 21 , which covers the component sector 19 surrounds.

[0014] In a processing method for a wafer according to an embodiment of the present invention, a forming step for a cut groove is first carried out to form cut grooves, each having a depth corresponding to a finished thickness of each component chip, by a cutting blade along the parting line. 13 from the front surface of the wafer 11 as a first step. The training step for a cut groove is carried out with reference to Fig. 2 described.

[0015] A cutting unit 10 includes a cutting blade 14 , which are removable from a tip section of a spindle 12 is attached, and an alignment unit 16, which is a visible light recording device (visible light recording unit) 18 exhibits. The recording unit 18 For visible light, it has a microscope and a camera that captures visible light.

[0016] Before performing the training step for a cut groove, an alignment is carried out in which the front surface of the wafer is aligned. 11 first with visible light through the recording unit 18 is captured for visible light, alignment marks such as target patterns, which are in each component 15 Those that are trained are detected, and the dividing line 13 The area to be cut is detected based on the alignment marks.

[0017] After the alignment has been carried out, a training step for a groove is performed, in which the cutting blade 15, which travel at high speed in the direction of an arrow R1 is rotated, is brought into the wafer 11 up to a depth corresponding to the finished thickness of each of the component chips, along the division line 13 from the front surface 11a of the wafer 11 to cut, and a clamping table (not shown) on which the wafer 11 held in suction, it is used for processing in one direction of an arrow. X1 supplied, resulting in a cut groove 23 along the dividing line 13 is being trained.

[0018] The training step for a cut groove is carried out sequentially along the parting lines. 13 carried out, extending in a first direction, while the cutting unit 10 into an index feed in a direction orthogonal to the direction X1the feed for processing around the distance of the dividing line 13 The clamping table (not shown) is then rotated 90° and the same forming step for a groove as above is carried out sequentially along the dividing lines. 13 carried out, extending in a second direction orthogonal to the first direction.

[0019] After the training step for a groove has been carried out, a sealing step is performed, in which, as in Fig. Figure 3 shows a sealing material 20 on the front surface 11a of the wafer 11 is applied to the front surface 11a of the wafer 11 , which cut the grooves 23 This involves sealing with a sealant. Since the sealant 20 The cut grooves will be liquid when the sealing step is carried out. 23with the sealing material 20 filled.

[0020] When the sealing material 20 The composition will contain 10.3% epoxy resin or epoxy resin plus phenolic resin, 85.3% silica filler, 0.1% to 0.2% carbon black, and 4.2% to 4.3% other ingredients by mass percent. Examples of the other ingredients include metal hydroxides, antimony trioxide, silicon dioxide, and the like.

[0021] If the front surface 11a of the wafer 11 with the sealing material 20 The soot, which is present in an extremely small quantity in the sealing material, causes damage when the material is covered and sealed and has such a composition. 20 It includes the sealing material 20 It is black, and accordingly it is usually difficult to see the front side. 11a of the wafer 11 through the sealing material 20 to see.

[0022] Here, the soot has seeped into the sealing material. 20 primarily to prevent electrostatic damage to the components 15 Mixed and currently no sealing material that does not contain carbon black is used commercially. The method for applying the sealing material 20 is not particularly limited; however, it is desirable to use the sealing material 20 up to a level of each of the increases 17 to apply, and then the sealing material is applied. 20 exposed to an etching process to remove the end sections of the elevations 17 to uncover.

[0023] After the sealing step has been carried out, an alignment step is performed in which the front surface 11a of the wafer 11 through the sealing material 20 through the exception for visible light from the front surface 11a of the wafer 11The recording includes at least two alignment marks such as target patterns, which are located on the front surface. 11a of the wafer 11 are trained, are detected and the division line 13 The part to be laser-processed is detected based on these alignment marks.

[0024] The alignment step is described in detail with reference to Fig. 4 described. Before performing the alignment step, the rear surface is 11b of the wafer 11 attached to a dividing band T, the outer circumferential section of which is attached to a ring-shaped frame F is appropriate. In the alignment step, as in Fig. As shown in 4, the wafer 11 through the clamping table 40 a laser processing device through the dividing belt T suctioned and held, and the sealing material 20 , the front surface 11a of the wafer11 Sealed, it lies exposed at the top. The ring-shaped frame F is then clamped together with clamps. 42 fixed.

[0025] In the alignment step, the front surface 11a of the wafer 11 by a receiving element such as a charge-coupled device (CCD) of a receiving unit 18A for visible light of a laser processing device similar to the recording unit 18 The visible light from the cutting device was used. However, because the ingredients such as silica fillers and carbon black are in the sealant material... 20 are included and furthermore, a front surface of the sealing material is uneven, even if the front surface 11a of the wafer 11 through the sealing material 20 by vertical illumination of the recording unit 18aWhen the image is taken using visible light, it is blurry, making it difficult to recognize alignment marks such as target patterns.

[0026] In this respect, the alignment step of the present embodiment can be achieved by illuminating an area to be recorded at an angle with light from an inclined light source. 31 in addition to the vertical illumination of the recording unit 18a For visible light, the blur problem of the captured image is improved, thus enabling detection of the alignment marks.

[0027] The light irradiation from the inclined light source 31 preferably white light and an angle of incidence at the front surface 11a of the wafer 11 is preferably in a range of 30° to 60°. The recording unit preferably includes 18AFor visible light, an exposure control is used, which allows the exposure time or similar parameters to be adjusted. Next, the clamping table is used. 40 rotated by θ so that a straight line connecting these alignment marks is parallel to the direction X1 a feed for processing, and furthermore the cutting unit 10 , which in Fig. 2 is shown, in the direction orthogonal to the direction X1 for a feed for processing by a distance between the alignment mark and the center of the division lines 13 moved, thereby changing the dividing line 13 , which is to be laser processed, is detected.

[0028] After the alignment step has been carried out, a training step for a modified shift is performed by, as described in Fig. 5A shows a laser beam LB of such a wavelength (for example, 1064 nm) that it passes through the sealing material. 20 runs, from a laser head (light collector) 46 the laser processing device along the division line 13 from the front surface 11a of the wafer 11 is applied, with a focal point of the laser beam LB in the sealing material. 20 in the cut groove 23 is positioned and the clamping table 40 for processing in the direction of the arrow X1 is supplied to create a modified layer 25 , which in Fig. 5B is shown, in which the sealing material 20 in the cut groove 23 to train.

[0029] This training step for a modified layer is carried out sequentially along the division lines. 13carried out, extending in a first direction, whereupon the clamping table 40 is rotated by 90°, and the training step for a modified layer is then carried out sequentially along the division lines. 13 carried out, extending in the second direction orthogonal to the first direction.

[0030] After the training step for a modified layer has been carried out, a grinding step is performed in which the wafer 11 from the rear surface 11b of the wafer 11 Each component chip is ground to a finished thickness to apply the sealing material. 20 in the cut groove 23 to uncover.

[0031] This grinding step is related to Fig. 6 described. A surface protection tape 22 is on the front surface 11a of the wafer 11 attached and the wafer 11is provided by a clamping table 24 in a grinding device through the surface protection belt 22 suctioned and held.

[0032] A grinding unit 26 includes a spindle 30 , which are rotatable in a spindle housing 28 is mounted and is driven by a rotating motor, which is not shown, a disc mounting 32 , which are located at one end of the spindle 30 is fixed, and a grinding wheel 34 , which are removable from the disc mounting 32 is attached. The grinding wheel 34 is made of a ring-shaped disc base 36 and several grinding stones 38 formed on an outer circumference of a lower end of the disc base 36 are secured.

[0033] During the grinding step, while the clamping table 24When the grinding wheel is rotated in the direction of arrow a at, for example, 300 revolutions per minute, it is rotated. 34 rotated in one direction of arrow b, for example at 6000 revolutions per minute, and a feed mechanism for a grinding unit (not shown) is driven to supply the grinding stones. 38 the grinding wheel 34 in contact with the rear surface 11b of the wafer 11 bring to.

[0034] Then the rear surface 11b of the wafer 11 ground while the grinding wheel 34 The wafer is moved downwards by a predetermined amount at a predetermined feed rate into a grinding feeder. While the wafer reaches a certain thickness... 11 The thickness of a contact type or a non-contact type is measured by a measuring instrument, and the wafer is then identified. 11ground to a predetermined thickness, for example 100 µm, thereby applying the sealing material 20 , which is in the cut grooves 23 is filled, is exposed.

[0035] After the grinding step has been carried out, a division step is performed in which an external force is applied to the wafer. 11 using a dividing device 50 , which in Fig. 7 is shown, applied to the wafer 11 into individual component chips 27 to divide. The dividing device 50 , which in Fig. As shown in section 7, it includes a frame holding device. 52 , which holds the ring-shaped frame F and a band expansion device 54 , that the dividing band T, which is attached to the ring-shaped frame F, which is held by the frame retaining device 52 is held, expands.

[0036] The frame holding device 52includes a ring-shaped frame retaining element 56 and several terminals 58 as a fixing means attached to an external environment of the frame holding element 56 are arranged. An upper surface of the frame retaining element 56 forms a mounting surface 56a from which the ring-shaped frame F is to be attached, and the ring-shaped frame F is on the mounting surface 56a attached.

[0037] Then the ring-shaped frame F , which is attached to the mounting surface 56a is attached to the frame retaining element 56 through the clamps 58 fixed. The frame holding device 52 , which is designed in this way, is supported in such a way that it is extended in a vertical direction by the expansion means 54 is movable.

[0038] The expansion agent 54 For a band, an expansion drum 60on, which are located inside the ring-shaped frame retaining element 56 is arranged. An upper end of the expansion drum 60 is equipped with a closure 62 Closed. The expansion drum 60 has an inner diameter that is smaller than the inner diameter of the annular frame F and larger than the outer diameter of the wafer 11 is the one attached to the dividing band T is attached to the ring-shaped frame F.

[0039] The expansion drum 60 features a support flange 64 on, which is integrally formed at a lower end. The expansion medium 54 Furthermore, a drive means is required for a belt. 66 on, which the ring-shaped frame retaining element 56 moved in the vertical direction. The propulsion system 66 consists of several air cylinders 68 trained, which are attached to the support flange 64are arranged, and piston rods thereof are connected to a lower surface of the frame retaining element. 56 tied together.

[0040] The propulsion system 66 , which consists of several air cylinders 68 The ring-shaped frame retaining element is designed to move the ring-shaped frame holding element. 56 in the vertical direction between a reference position in which the mounting surface 56a essentially the same height as a front surface of the closure 62 features which is the upper end of the expansion drum 60 serves, and an expansion position that is a predetermined amount deeper than the top end of the expansion drum 60 is.

[0041] The division step for the wafer 11 , which uses the dividing device 50 The procedure, which is designed as described above, is carried out with reference to Fig. 8A and Fig. 8B described. As in Fig. As shown in 8A, the ring-shaped frame F, which holds the wafer 11 through the dividing band T, on the mounting surface 56a of the frame retaining element 56 attached and from the frame retaining element 56 through the clamps 58 fixed. In this case, the frame retaining element is 56 positioned in the reference position in which the mounting surface 56a of which essentially the same height as the top of the expansion drum 60 exhibits.

[0042] Next, the air cylinders will be 68 powered to secure the frame retaining element 56 to lower to the extension position, as in Fig. 8B is shown. Accordingly, the ring-shaped frame is F , which is attached to the mounting surface 56a of the frame retaining element 56 is fixed, lowered, and as a result lies the dividing band T, which is attached to the ring-shaped frame. Fis attached to an upper end edge of the expansion drum 60 and is essentially extended in a radial direction.

[0043] As a result, tensile forces are applied radially to the wafer. 11 , which is attached to the dividing band T is attached, applied. If the tensile forces are therefore radial to the wafer 11 The wafer will be applied 11 along the modified layers 24 , which are in the sealing material 20 in the cut groove 23 along the dividing lines 13 are formed, divided, with the modified layers 25 serve as starting points for the division, as shown in the enlarged view of Fig. 9 shown, where the wafer 11 into individual component chips 27 is divided, each of which has its front surface and four side surfaces sealed by the sealing material. 20 surrounds and features.

[0044] The present invention is not limited to the details of the preferred embodiments described above. The scope of the invention is defined by the attached claims, and all changes and modifications that fall within the equivalent scope of the claims are therefore included in the invention. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] JP 2013074021

[0004] JP 2016015438

[0004]

Claims

[1] Wafer machining method for machining a wafer in which each feature having multiple elevations is formed in each of the regions of a front surface divided by multiple intersecting division lines formed in an intersecting manner, the wafer machining method comprising: a training step for a cut groove to form cut grooves, each having a depth corresponding to a finished thickness of each of the component chips, by a cutting blade along the parting lines from a front surface side of the wafer; a sealing step to seal the front surface of the wafer, including the cut grooves, with a sealing material after the training step for a cut groove has been performed; an alignment step to detect an alignment mark through the sealing material by means of a visible light receiving means from the front surface of the wafer and detect the parting line to be laser processed based on the alignment mark after the sealing step has been performed; a training step for a modified layer to emit a laser beam of such wavelength that it passes through the sealing material along the parting lines from the front surface of the wafer, wherein a focal point of the laser beam is positioned in the sealing material in the cut grooves to form modified layers in the sealing material in the cut grooves after the alignment step has been performed; a grinding step to grind the wafer from a rear surface side of the wafer to the finished thickness of each of the device chips to expose the sealing material in the cut grooves after the training step for a modified layer has been performed; and a division step to apply an external force to the sealing material in the cut grooves and parts of the wafer, with the modified layers serving as the starting points of the division, into individual component chips, each of which has its front surface and four side surfaces surrounded by the sealing material after the grinding step has been performed, wherein the alignment step is carried out while an area to be recorded by the visible light receiving device is illuminated at an angle by an inclined light source.

Images