Manufacturing process for chips with adhesive layers

Abstract

Training method for chips (80) with adhesive layers (30) attached to the back (Wb), the method comprising: a parting point formation step in which a plurality of parting points are formed within a wafer (W) using a laser beam along a plurality of intersecting parting lines (S1, S2) formed on the front face (Wa) of the wafer (W); an adhesive layer attachment step in which an adhesive layer (30) is attached to the back (Wb) of the wafer (W) after performing the separation start point formation step; an adhesive layer separation groove formation step in which a plurality of separation grooves (31) are formed in the adhesive layer (30) along the separation lines (S1, S2) by applying a laser beam or by using a cutting blade after performing the adhesive layer attachment step; an expansion arc attachment step in which an expansion arc (60) is attached to the bonding layer (30) which is attached to the wafer (W) after performing the bonding layer separation groove formation step; and a separation step in which the expansion arc (60) is expanded to apply an external force to the wafer (W) after the expansion arc attachment step has been performed, thereby separating the wafer (W) with the adhesive layer (30) to obtain a plurality of individual chips (80) such that each chip (80) is formed with the adhesive layer (30) attached to the back (Wb).

Description

Background of the invention; Field of the invention

[0001] The present invention relates to a manufacturing method for chips with adhesive layers attached to the back. State of the art

[0002] As described in Japanese patent application number JP 2000-182995A, there is a manufacturing process for semiconductor chips with adhesive films (die attach films) attached to the back. Each adhesive film is called a DAF (Die Attach Film), which is used for die bonding. Furthermore, as described in Japanese patent application number JP H11-40520A, there is a process called "dice pre-grinding" (or "dice pre-grinding").: dicing-before-grinding) comprising the steps of forming a plurality of grooves, each having a depth greater than the finished thickness of each chip, along a plurality of intersecting cube lines (separation lines) on the front of a wafer on which semiconductor facilities are formed, and subsequent grinding and polishing of the back of the wafer to reduce the thickness of the wafer to the finished thickness of each chip, thereby dividing the wafer into the individual chips.

[0003] Furthermore, as described in Japanese patent application JP 2002-118 081 A, there is a method comprising the steps of attaching an adhesive layer to the back side of a wafer that has already been subdivided into individual chips by the "cube-before-grind" process, and subsequently applying a laser beam from the front side of the wafer through the gap between the adjacent chips to the adhesive layer, thereby subdividing the adhesive layer. Furthermore, as described in Japanese patent application JP 2005-223 283 A, there is another method for tearing the adhesive layer by using a separating device instead of using a laser beam to cleave the adhesive layer, as mentioned above.

[0004] Further prior art that may be helpful for understanding the present invention can be found in the following documents: US 2006 / 0040472 A1 relates to a method for separating a semiconductor substrate using a laser beam. DE 102010039798 A1 relates to a wafer processing method for processing a wafer, such as a semiconductor wafer. JP 2009-283925 A relates to an adhesive layer connected to a parting line and a manufacturing method for the same. US 2009 / 0004780 A1 relates to a method for manufacturing a semiconductor chip. Summary of the invention

[0005] However, in the case of attaching the adhesive layer to the wafer, which has already been subdivided into individual chips using the "cubing before grinding" process, as disclosed in Japanese patent JP 2002-118 081 A, there is the possibility of a so-called die shift. This shift causes the separated chips to move during the adhesive layer application. This die shift creates a problem in that the separation lines, which define the chip spacing along which the laser beam is to be applied, can be curved (not straight) or, in some cases, the chip spacing can become zero. If the separation lines along which the laser beam is to be applied are curved, the laser beam must follow the curved lines, making precise laser beam control very difficult.Furthermore, if the distances between the chips become zero, the laser beam cannot be applied.

[0006] On the other hand, in the case of tearing the adhesive layer using a separating device, as disclosed in Japanese patent application JP 2005-223 283 A, there is a possibility that the adhesive layer cannot be divided into sections when torn, particularly if the chip size is 1 mm or less per side. Furthermore, the torn adhesive layer is larger than any chip, creating the problem that the end of the torn layer may adhere to the side or front surface of each chip, potentially causing a pickup failure or setup failure.

[0007] It is therefore an object of the present invention to provide a manufacturing method for chips with adhesive layers attached to the back, whereby the aforementioned problems concerning the separation of the adhesive layer can be eliminated.

[0008] According to one aspect of the present invention, a manufacturing method for chips with adhesive layers attached to the back side is provided, the method comprising a parting point formation step in which a plurality of parting points are formed in a wafer along a plurality of intersecting parting lines formed on the front side of the wafer; an adhesive layer attachment step in which an adhesive layer is attached to the back side of the wafer after performing the parting point formation step; an adhesive layer parting groove formation step in which a plurality of parting grooves are formed in the adhesive layer along the parting lines by applying a laser beam or by using a cutting blade after performing the adhesive layer formation step; and an expansion arc attachment step in which an expansion arc (i.e., a ridge or ridge) is formed on the back side of the wafer.: expand sheet) is attached to the adhesive layer that is attached to the wafer, after performing the adhesive layer separation groove formation step; and a separation step in which the expansion arc is expanded to apply an external force to the laser, after performing the expansion arc attachment step, thereby separating the wafer with the adhesive layer to obtain a multitude of individual chips, so that each chip is formed with the adhesive layer attached to the back.

[0009] Preferably, this method further includes a grinding step in which the back of the wafer is ground to form a circular recess and an annular projection surrounding the circular recess before performing the parting point formation step.

[0010] According to the present invention, the adhesive layer is formed on the back side of the wafer after the separation start points have been formed in the wafer and before the wafer is separated into individual chips. After the adhesive layer is attached to the wafer, the separation grooves in the adhesive layer are formed along the separation lines that define the spacing of the devices (chips), and the wafer is subsequently subdivided into the individual chips. According to this method, the wafer has not yet been subdivided at the time the adhesive layer is attached to it, so there is no possibility of die misalignment, thus eliminating the problem of curved separation lines or zero device spacing. Furthermore, the separation grooves in the adhesive layer are formed along the separation lines, and the wafer is subsequently subdivided into the individual chips.Accordingly, there is no possibility of the problem that occurs in the event of the adhesive layer tearing.

[0011] The above and other tasks, features and advantages of the present invention and the manner of its implementation will become more apparent, and the invention itself will be best understood by studying the following description and the attached claims with reference to the accompanying drawings, which show some preferred embodiments of the invention. Brief description of the drawings Fig. Figure 1 is a perspective view of a semiconductor wafer to be processed; Fig. Figure 2 is a perspective view of a grinding unit for performing a grinding step; Fig. Figure 3 is a perspective view of a laser processing device for performing a parting start point formation step; Fig. 4 is a block diagram of a laser beam application unit; Fig. 5A is a sectional view of the wafer in the state where the protective tape is attached to the front of the wafer; Fig. 5B is a sectional view of the wafer in the state in which a circular recess is formed on the back of the wafer; Fig. 5C is a cross-sectional view of the wafer in the state in which modified layers are formed in the wafer; Fig. 5D is a cross-sectional view of the wafer in the state where an adhesive layer is attached to the back of the wafer; Fig. Figure 6 is a cross-sectional view of the wafer in the state in which the separation grooves are formed in the adhesive layer; Fig. Figure 7A is a sectional view of the wafer in the state in which an expansion arc is attached to the bonding layer; Fig. 7B is a cross-sectional view of the wafer in the state where the protective tape is removed; Fig. Figure 7C is a sectional view of the wafer in the state in which the wafer is arranged on a clamping table with a circular projection; Fig. Figure 8A is a cross-sectional view of the wafer in the state in which a ring-shaped, modified layer has formed in the wafer; Fig. Figure 8B is a sectional view of the wafer in the state where the expansion arc is extended; Fig. 8C is a cross-sectional view of the wafer in the state where the wafer is divided into individual chips; Fig. 9A is a sectional view of the wafer in the state in which an annular parting groove is formed in the wafer as a modification; Fig. Figure 9B is a sectional view of the wafer in the state in which an annular circumferential edge region of the wafer has been removed; and Fig. 9C is a cross-sectional view of the wafer in the state where the wafer has been divided into individual chips. Detailed description of the preferred embodiment

[0012] A preferred embodiment of the present invention will now be described in detail with reference to the drawings. Referring to Fig. Figure 1 shows a perspective view of a semiconductor wafer W (hereinafter referred to simply as "wafer W") to be processed, in a front side view. A plurality of first parting lines (roads) S1 and a plurality of second parting lines (roads) S2 perpendicular to the first parting lines S1 are formed on the front face Wa of the wafer W to subdivide a plurality of rectangular areas, in each of which a plurality of devices D, such as LSIs, are formed. A processing method for the wafer W according to a preferred embodiment of the invention is now described. Before performing a parting start point formation step, which is described in detail below, a grinding step is first carried out, as shown in Fig. 2 shown, in such a way that the back side Wb of the wafer W is ground to form a circular recess Wc and an annular projection Wd surrounding the circular recess Wc.

[0013] Fig. Figure 2 shows a grinding unit 11 for performing this grinding step. The grinding unit 11, which is located in Fig. Figure 2 shows a housing 12, a spindle 18 rotatably mounted in the housing 12, a mounting device 13 attached to the lower end of the spindle 18, a grinding wheel 21 screwed to the lower surface of the mounting device 13, and a servo motor (not shown) for rotating the spindle 18. A plurality of abrasive elements 52 are attached to the lower surface of the grinding wheel 21 in an annular arrangement. A clamping table 35 is provided below the grinding unit 11. The wafer W is designed to be held by vacuum against the upper surface (holding surface) of the clamping table 35. Before holding the wafer W by vacuum, a protective tape fastening step is performed such that a protective tape 10 ( Fig. 1 and Fig. 5A) is attached to the front Wa of the wafer W to protect the devices D. The wafer W is held by means of negative pressure on the upper surface of the clamping table 35 in the state in which the protective tape 10 is directed downwards.

[0014] The clamping table 35 is rotated at 300 rpm in the direction indicated, for example, by arrow 37, and the grinding wheel 21 is also rotated at, for example, 6000 rpm in the direction indicated by arrow 53. In this state, the grinding wheel 21 is lowered to bring the abrasive elements 52 into contact with the back surface Wb of the wafer W. Subsequently, the grinding wheel 21 is moved downwards by a predetermined amount at a predetermined feed rate. As a result, the back surface Wb of the wafer W is ground to form the annular recess Wc and the annular projection (ring-shaped reinforcement section) Wd, as shown in Fig. 2 shown, to form. The ring-shaped recess WC is formed by grinding the back of a fitting area 17 (see Fig. 1), in which the features D are formed, thereby reducing the thickness of the feature area 17 to a predetermined thickness (for example, 30 µm). Accordingly, a circumferential edge area (see Fig. 1), in which the devices D are not formed, left over in order to form the ring-shaped projection Wd around the circular recess Wc.

[0015] After performing the aforementioned grinding step, a parting line start point formation step is carried out such that a plurality of parting start points are formed in the wafer W along the plurality of intersecting parting lines formed on the front face Wa of the wafer W. This parting start point formation step is carried out using a laser processing device 20, which is located in Fig. Figure 3 shows the laser processing device 20 comprising a laser beam application unit 24 and a clamping table 22. The laser beam application unit 24 comprises a housing 26 and a focusing device 28, which is arranged at the front end of the housing 26. A laser beam is applied by the focusing device 28 to the rear side Wb of the wafer W, thereby forming the separation start point inside the wafer W along each separation line.

[0016] As shown in the block diagram of Fig. As shown in Figure 4, a laser oscillator 34 and a laser beam modulator 36 are provided in the housing 26 of the laser beam application unit 24. A YAG laser oscillator or a YVO4 laser oscillator can be used as the laser oscillator 34. The laser beam modulator 36 comprises a repetition frequency adjustment device 38, a laser beam pulse width adjustment device 40, and a laser beam wavelength adjustment device 42. The repetition frequency adjustment device 38, the laser beam pulse width adjustment device 40, and the laser beam wavelength adjustment device 42, which form the laser beam modulator 36, are known in the prior art, and a detailed description of these is not given here.

[0017] As in Fig. As shown in Figure 3, the wafer W is held by the protective tape 10 on the upper surface (holding surface) of the clamping table 22, which forms the laser processing device 20. In this state, the clamping table 42 is fed in the X-direction to deposit a modified layer inside the wafer W along a predetermined first parting line S1 ( Fig. 1) to form. Subsequently, the clamping table 22 is indexed in the Y-direction to similarly form a multitude of modified layers inside the wafer W along all the other first parting lines S1. Subsequently, the clamping table 22 is rotated by 90° to similarly form a multitude of modified layers inside the wafer W along all the second parting lines S2 ( Fig. 1).

[0018] In this preferred embodiment, the circular recess Wc is formed before the modified layers are formed. Accordingly, by forming the modified layers along the parting lines S1 and S2 ( Fig. 1) Within the area corresponding to the circular recess Wc, a reduction in the strength of the annular projection Wd is prevented. However, the modified layers can be formed along the parting lines from one end to the other on the outer circumference of the wafer W. The laser beam application unit 24 is equipped with an image recording unit 29 with an infrared camera for detecting the parting lines formed on the front Wa of the wafer W by applying infrared light from the rear Wb of the wafer W to perform an alignment operation. As a modification, the holding surface of the clamping table 29 can be made of a transparent material, and a conventional camera can be positioned below the holding surface of the clamping table 22 to image the front Wa of the wafer W through the holding surface.

[0019] For example, the separation start point training step is carried out using the laser beam mentioned above under the following processing conditions.

[0020] Light source: LD pumped Q-switched Nd:YVO4 pulsed laser Wavelength: 1064 nm Repetition frequency: 100kHz Average power consumption: 1 W Diameter of the focused spot: φ 1 µm Workpiece feed speed: 100 mm / s

[0021] While the modified layers are configured as the parting points in this preferred embodiment, laser-machined grooves (using a laser beam) or cut grooves (using a cutting blade) can also be configured as the parting points. However, when the modified layers are configured as the parting points, the width of each parting line can be reduced to increase the number of chips obtainable from the wafer W. From this perspective, the modified layers are preferably configured as the parting points.

[0022] Fig. Figure 5A shows the protective tape attachment step of attaching the protective tape 10 to the front Wa of the wafer W. Fig. Figure 5B shows the grinding step of grinding the back side Wb of the wafer W to create the circular recess Wc and the annular projection Wd surrounding the circular recess Wc, after performing the protective tape attachment step described in Fig. 5A is shown, to train. Fig. Figure 5C shows the parting point formation step, in which the parting points (modified layers 73) are formed along the multitude of intersecting parting lines formed on the wafer after performing the grinding step described in Fig. 5B is shown.

[0023] After performing the separation start point training step, which is in Fig. As shown in 5C, an adhesive layer attachment step is performed, as in Fig. Figure 5D shows a process carried out such that an adhesive layer 30 is attached to the back surface Wb of the wafer W. This adhesive layer 30 is referred to as a DAF (Die Attach Film), which is used for die bonding. In this preferred embodiment, the adhesive layer 30 has a circular shape so that it is attached in the circular recess Wc formed on the back surface Wb of the wafer W (in the area surrounded by the annular projection Wd). Furthermore, the outer circumference of the adhesive layer 30 comes into contact with the side wall of the circular recess Wc (the inner circumferential wall of the annular projection Wd), thereby positioning the adhesive layer 30 on the wafer W. A known fastening device, such as a vacuum laminator, can be used to attach the adhesive layer 30 to the back surface Wb of the wafer W (the lower surface of the circular recess Wc).

[0024] In the state in which the separation start point training step, which is in Fig. As shown in Figure 5C, the wafer W has not yet been cut along the dividing lines, meaning it has not yet been subdivided into individual chips. Accordingly, when attaching the adhesive layer 30 to the back side Wb of the wafer W, as shown in Figure 5C, the wafer W has not yet been cut along the dividing lines, i.e., it has not yet been subdivided into individual chips. Fig. As shown in 5D, there is no possibility of a so-called die shift, meaning the chips are not moved. After performing the adhesive layer attachment step, which is shown in Fig. As shown in 5D, an adhesive layer separation groove formation step is performed, as in Fig. 6 shown, carried out in such a way that a laser beam LB is applied to the adhesive layer 30 along the separation lines S1 and S2 in order to form a plurality of separation grooves 31 in the adhesive layer 30 along the separation lines S1 and S2.

[0025] In the preferred embodiment, which is described in Fig. As shown in Figure 6, ablation is performed on the adhesive layer 30 by the laser beam LB while the wafer W is held on a clamping table 44. Specifically, the clamping table 44 has a holding surface 44a for holding the wafer W under negative pressure. The wafer W is held under negative pressure by the protective tape 10 on the holding surface 44a of the clamping table 44 in the state where the adhesive layer 30 is attached to the lower surface of the circular recess Wc of the wafer W. The laser beam LB is applied to the adhesive layer 30 to form the parting grooves 31 in the adhesive layer 30 along the parting lines S1 and S2. The parting grooves 31 can be fully cut grooves that completely cut through the adhesive layer 30, or partially cut grooves that do not completely cut through the adhesive layer 30.

[0026] For example, the adhesive layer separation groove formation step, in which the separation grooves in the adhesive layer 30 are formed by removal, is carried out under the following processing conditions. Light source: LD pumped Q-switched Nd:YAG pulsed laser Wavelength: 355 nm (third harmonic generation of the YAG laser) Power: 3 to 3.75 W Repetition frequency: 10 kHz Workpiece feed speed: 100 to 200 mm / s

[0027] While the adhesive layer separation groove formation step is carried out by ablation using a laser processing device in this preferred embodiment, a cutting device with a rotating cutting blade can be used to form a cut groove in order to create the separation grooves 31. In this case, there is a possibility that the cutting blade will be subjected to stress by cutting the adhesive layer 30, depending on the thickness and type of the cutting blade and the type of the adhesive layer 30. In such a case, it is preferable to use a laser processing device.

[0028] After performing the adhesion layer separation groove formation step, which is in Fig. As shown in 6, an expansion arch fastening step is used, as in Fig. Figure 7A shows that the process is carried out by attaching an expansion arc 60 to the adhesive layer 30, which is attached to the wafer W. Specifically, the adhesive layer 60 is attached to the adhesive layer 30 in the state where the adhesive layer 30, which is attached to the wafer W, is oriented upwards and covered with the expansion arc 60. A known fastening device, such as a vacuum laminator, can be used to attach the expansion arc 60 to the adhesive layer 30.

[0029] The expansion arc 60 is temporarily supported on the annular frame F in such a way as to close the opening of the annular frame F. Accordingly, the adhesive layer 30 and the wafer W are attached to the annular frame F by the expansion arc 60. After carrying out the expansion arc attachment step, which is described in Fig. As shown in 7A, a protective tape removal step is performed, as in Fig. Figure 7B shows that the process is carried out in such a way that the protective tape 10 is removed from the front Wa of the wafer W. Accordingly, the front Wa of the wafer W, on which the features D are formed, is exposed.

[0030] After performing the protective tape removal step, which is described in Fig. As shown in 7B, a holding step is performed in the manner shown in Fig. Figure 7C shows that the wafer W, which is attached to the ring-shaped frame F, compared to the one in Fig. The wafer W is inverted in the state shown in Figure 7B and then placed on a clamping table 70, which has a circular projection 72 on its upper surface (holding surface) corresponding to the circular recess Wc of the wafer W. Specifically, the circular projection 72 of the clamping table 70 engages the circular recess Wc of the wafer W from the underside when in Fig. 7C is considered, introduced. That is, the wafer W is held on the clamping table 70 in such a way that the back side Wb of the wafer W completely covers the circular projection 72.

[0031] After performing the holding step, which is in Fig. As shown in 7C, a separation step is performed, as in Fig. Figures 8A to 8C show that the extension arc 60 is extended to apply an external force to the wafer W, thereby dividing the wafer W with the adhesive layer 30 along the dividing lines to obtain a plurality of individual chips 80, so that each chip 80 to which the adhesive layer 30 is attached on the back is formed.

[0032] Specifically, as in Fig. As shown in Figure 8A, a laser beam LB is applied to the boundary between the setup area 17 and the circumferential edge area 19 of the wafer W, that is, the boundary between the circular recess Wc and the annular projection Wd of the wafer W, during rotation of the clamping table 70, thereby forming an annular modified layer 74 along the boundary between the circular recess Wc and the annular projection Wd of the wafer W. The modified layer 74 is preferably formed along the extension line of the inner circumferential wall of the annular projection Wd. Subsequently, the expansion arc 60 is formed using an expansion device (not shown), as in Figure 8A. Fig. 8B shows, expanded. As mentioned above, the modified layer 74 was already formed in wafer W, as shown in Fig. 8A shown, and the multitude of modified layers 73 were already formed in the wafer W along the separation lines S1 and S2 by the separation start point formation step, as in Fig. 5C shown, formed. Furthermore, the multitude of separation grooves 31 were already formed in the adhesive layer 30 along the separation lines S1 and S2 by the adhesive layer separation groove formation step, as shown in Fig. 6 shown, formed. Accordingly, the wafer W is fractured along the modified layers 73 and 74 to obtain the individual chips 80, as shown in Fig. 8C shown.

[0033] A modification of this separation step is now being made with reference to Fig. 9A to 9C described. As in Fig. As shown in Figure 9A, a laser beam is applied to ablate the boundary between the setup area 17 and the circumferential edge area 19 of the wafer W, that is, the boundary between the circular recess Wc and the annular projection Wd of the wafer W during rotation of the clamping table 70, thereby forming an annular parting groove 75 along the boundary between the circular recess Wc and the annular projection Wd of the wafer W. The parting groove 75 is preferably formed along the extension line of the inner circumferential wall of the annular projection Wd.

[0034] Subsequently, the ring-shaped circumferential edge region 19 of the wafer W, which was separated from the setup area 17 by the parting groove 75, is removed, as shown in Fig. 9B shown. Subsequently, the expansion arc 60 is expanded using an expansion device (not shown), as in Fig. 9C shown. As mentioned above, the multitude of modified layers 73 were already formed in wafer W along the separation line S1 and S2 by the separation start point formation step, as shown in Fig. 5C shown. Furthermore, the multitude of separation grooves 31 were already formed in the adhesive layer 30 along the separation lines S1 and S2 by the adhesive layer separation groove formation step, as shown in Fig. Figure 6 shows that the wafer W is broken along the modified layers 73 to obtain the individual chips 80.

[0035] According to the preferred embodiment mentioned above, the adhesive layer 30 is attached to the back side Wb of the wafer W after the separation start points have been formed in the wafer W and before the wafer W is separated into individual chips. After the adhesive layer 30 is attached to the wafer W, the separation grooves 31 are formed in the adhesive layer 30 along the separation lines S1 and S2, which define the spacing of the devices D (chips), and the wafer W is subsequently divided into individual chips. According to this method, the wafer W has not yet been divided at the time the adhesive layer 30 is attached to the wafer W, so there is no possibility of die misalignment, thus eliminating the problem that the separation lines S1 and S2, which define the spacing of the devices D, may be curved or that the spacing of the devices D may become zero.Furthermore, the separation grooves 31 are formed in the adhesive layer 30 along the separation lines S1 and S2, and the wafer W is subsequently subdivided into individual chips. Accordingly, the problem that occurs in the case of tearing of the adhesive layer 30 is eliminated.

[0036] According to the preferred embodiment mentioned above, the modified layers can preferably be formed in a workpiece having narrow parting lines by using a laser beam, which is a suitable operating principle. Furthermore, the annular projection Wd, which is formed simultaneously with the formation of the circular recess Wc, can be made to act as a circumferential reinforcement section, so that the thin wafer W with the parting start points formed therein can be handled safely.Furthermore, even if the wafer W is split along some of the separation points during handling to separate some of the chips, the protective tape 10, which is attached to the front Wa of the wafer W, is bent due to the formation of the annular projection Wd (circumferential reinforcement section) in the wafer W, thereby eliminating the influence of the location of the other chips and thus preventing any possibility of die misalignment. Moreover, since the separation grooves 31 are formed in the adhesive layer 30, the adhesive layer 30 can be easily and reliably separated in all areas, that is, along all the separation lines S1 and S2. In particular, the present invention is suitable for forming thin, small chips with adhesive layers or for processing a wafer with a large diameter, for example, 30 cm (12 inches).

[0037] As a configuration to reduce the handling risk of a thin wafer (any problem, such as wafer damage during handling), it is considered to connect the laser processing or cutting device for forming the parting points with the grinding or tape attachment device in a series arrangement (a configuration that combines or integrates a variety of devices into one). In this case, the parting point formation process (parting point formation step) requires more time than the other processes.Specifically, when processing a wafer to obtain smaller chips (tiny chips), the number and spacing of the parting points are increased. This increases the time required to form the parting points, leading to a reduction in the UPH (Units Per Hour) value, i.e., the number of wafers that can be processed per hour. If the wafer has a large diameter, the number and spacing of the parting points are increased even further, resulting in a further reduction in the UPH value.

[0038] Accordingly, when using such a series-arranged configuration, a balance in the UPH value cannot be maintained between the laser processing device or the cutting device for forming the separation start points and the grinding device or the tape fastening device, and the downtime of the grinding device or the tape fastening device is increased, resulting in a reduction of the CoO value (Cost of Operation).

[0039] In contrast, the wafer W is not simply reduced in thickness; instead, in the preferred embodiment mentioned above, an annular projection Wd is formed along the outer circumference of the wafer W, thereby increasing the strength of the wafer W and reducing handling risks. As a result, the risk of reducing the CoO value can be minimized, thus ensuring a good CoO value throughout the entire process.Furthermore, if the in-line configuration mentioned above is not used, the laser processing device or the cutting device for forming the separation start points can be operated independently of the grinding device or the tape attachment device in order to ensure that the UPH value of the laser processing device or the cutting device for forming the separation start points does not affect the UPH value of the grinding device or the tape attachment device, thus increasing the number of wafers that can be processed per hour.

[0040] While the grinding step of forming the circular recess and the annular protrusion is performed in the embodiment described above, a thickness reduction step can instead be performed by grinding the entire back side of the wafer without forming the annular recess and protrusion, thereby reducing the wafer's thickness. Following the thickness reduction step, all the other steps, including the parting point formation step, the adhesive layer attachment step, the adhesive layer parting groove formation step, the expansion arc attachment step, and the parting step, are performed in that order. As a modification, the thickness reduction step can be performed after the parting point formation step.Subsequently, the adhesive layer attachment step, the adhesive layer separation groove formation step, the expansion arc attachment step and the separation step are carried out in a similar manner in this order.

Claims

[1] A method for forming chips (80) with adhesive layers (30) attached to the back side (Wb), the method comprising: a separation start point forming step of forming a plurality of separation start points using a laser beam within a wafer (W) along a plurality of intersecting separation lines (S1, S2) formed on the front side (Wa) of the wafer (W); an adhesive layer attaching step of attaching an adhesive layer (30) to the back surface (Wb) of the wafer (W) after performing the separation start point forming step; an adhesive layer separation groove forming step of forming a plurality of separation grooves (31) in the adhesive layer (30) along the separation lines (S1, S2) by applying a laser beam or by using a cutting knife after performing the adhesive layer fixing step; an expansion sheet attaching step of attaching an expansion sheet (60) to the adhesive layer (30) attached to the wafer (W) after performing the adhesive layer separating groove forming step; and a separating step of expanding the expansion sheet (60) to apply an external force to the wafer (W) after performing the expansion sheet attaching step, thereby separating the wafer (W) with the adhesive layer (30) to obtain a plurality of individual chips (80), such that each chip (80) is formed with the adhesive layer (30) attached to the back side (Wb). [2] A forming method for chips (80) having adhesive layers (30) according to claim 1, further comprising a grinding step of grinding the back surface (Wb) of the wafer (W) to form a circular recess (Wc) and an annular projection (Wd) surrounding the circular recess before the separation start point forming step is performed.

Images