JP6004705B2 - Method for forming chip with adhesive film - Google Patents

Description

  The present invention relates to a method for forming a chip with an adhesive film that forms a chip with an adhesive film attached to the back surface.

  Conventionally, as described in Patent Document 1, a method for manufacturing a semiconductor chip in which an adhesive film (adhesive layer) is attached to the back surface is known. The adhesive film is called DAF (Die Attach Film) and is used for die bonding.

  Further, as described in Patent Document 2, grooves deeper than the chip thickness at the time of completion are formed from the semiconductor element formation surface side along dicing lines arranged in a lattice pattern on the wafer on which the semiconductor elements are formed. A so-called first dicing method is known in which after the formation, the back surface of the wafer is ground and polished to the thickness of the chip at the completion, and the wafer is separated into individual chips.

  Furthermore, as described in Patent Document 3, after adhering an adhesive film on a wafer that has already been divided into chips by a prior dicing method, the adhesive film is irradiated with a laser beam through adjacent chips. A method of breaking is known.

  On the other hand, as described in Patent Document 4, there is also known a technique in which an adhesive film is not broken by a laser beam but is torn off by a dividing device.

JP 2000-182959 A JP-A-11-040520 JP 2002-118081 A JP 2005-223283 A

  However, as disclosed in Patent Document 3, in the form in which an adhesive film is attached to a wafer that has been once divided into chips by the first dicing method, the divided chips move when the adhesive film is attached. There is concern about the occurrence of die shift. When such a die shift occurs, the line to be irradiated with the laser beam formed in the gap between adjacent chips is not straight (not straight), and in some cases, the gap between the chips. Will disappear.

  If the line to be irradiated with the laser beam is bent, it is necessary to irradiate the laser beam following the curve, and it becomes very difficult to control the laser beam irradiation. Further, if there is no gap between the chips, the laser beam cannot be irradiated.

  On the other hand, in the technique of tearing the adhesive film with a dividing apparatus as disclosed in Patent Document 4, for example, when the adhesive film is torn for a chip having a chip size of 1 mm square or less, there is a risk that a region where the adhesive film is not broken may occur. There is. Further, since the torn adhesive film is formed larger than the chip, the edge of the torn adhesive film may adhere to the side surface or the surface of the chip, which may cause a pickup failure or a device failure later.

  The present invention has been made in view of the above problems, and the object of the present invention is to break the adhesive film with respect to a method for forming a chip with an adhesive film that forms a chip with an adhesive film attached to the back surface. Is to provide a technique for solving the above problems.

According to invention of Claim 1, it is a formation method of the chip | tip with an adhesive film which forms the chip | tip with an adhesive film by which the adhesive film was stuck on the back surface, Comprising: On the wafer by which the several division | segmentation schedule line which crossed was set After performing the split starting point forming step along the planned split line, the split starting point forming step, the adhesive film sticking step for sticking the adhesive film to the back surface of the wafer, and the adhesive film sticking step are performed. After the adhesive film dividing groove forming step and the adhesive film dividing groove forming step for forming the dividing groove along the line to be divided on the adhesive film by laser beam irradiation or a cutting blade, the adhesive film was adhered to the wafer. Expanding sheet sticking step to stick an expanding sheet on the adhesive film, and expanding After performing the sheet attaching step, the expanded sheet is expanded to give external force to the wafer to divide the wafer and adhesive film into individual chips, and the adhesive film with the adhesive film attached to the back A dividing step for forming a plurality of chips, and a grinding step for forming a circular concave portion by grinding the back surface of the wafer and forming an annular convex portion surrounding the circular concave portion before performing the division starting point forming step. in the division start point forming step, to form a modified layer to be a division originating points by irradiating a laser beam to the backside of the wafer, characterized in that the peripheral marginal region of the wafer does not form a circular modified layer adhesion A method for forming a filmed chip is provided.

According to the second aspect of the present invention, in the dividing step, there is provided a method for forming a chip with an adhesive film in which a circular modified layer or a dividing groove is formed from the surface of the wafer to the outer peripheral surplus area before expanding the expanded sheet. Is done.

  According to the present invention, after the division starting point is formed on the wafer, the adhesive film is attached to the back surface of the wafer before the wafer is divided into individual chips. Thereafter, the adhesive film is formed with dividing grooves along the gaps between the chips, and the wafer is divided into individual chips.

  According to this method, since the wafer is not divided at the time of adhering the adhesive film, the planned division line formed in the gap between the chips is bent or the gap is eliminated without causing die shift. There is nothing. And since the division | segmentation groove | channel along the clearance gap between chips | tips is formed and a wafer is divided | segmented into each chip | tip, the malfunction in the method of tearing an adhesive film does not arise.

It is a perspective view shown about the semiconductor wafer which is a process target. It is a perspective view of the grinding unit for implementing a grinding step. It is a perspective view of the laser processing apparatus for implementing a division | segmentation starting point formation step. It is a block diagram of a laser beam irradiation unit. (A) is sectional drawing shown about the wafer which stuck the protective tape. (B) is sectional drawing shown about the wafer which comprised the circular recessed part. (C) is sectional drawing shown about the wafer in which the modified layer was formed. (D) is sectional drawing shown about the wafer which stuck the adhesive film. It is sectional drawing shown about the wafer in which the division | segmentation groove | channel was formed in the adhesive film. (A) is sectional drawing shown about the wafer which stuck the expanded sheet. (B) is sectional drawing shown about the wafer from which a protective tape is removed. (C) is sectional drawing shown about the wafer set to the chuck table which has a convex-shaped upper surface. (A) is sectional drawing shown about the wafer which stuck the expanded sheet. (B) is sectional drawing shown about the condition which expands an expanded sheet. (C) is sectional drawing shown about the condition divided | segmented into a chip | tip. (A) is sectional drawing shown about the wafer which stuck the expanded sheet. (B) is sectional drawing shown about the condition which removes a ring-shaped outer periphery excess area | region. (C) is sectional drawing shown about the condition divided | segmented into a chip | tip.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Referring to FIG. 1, a front side perspective view of a semiconductor wafer W to be processed (hereinafter also simply referred to as “wafer W”) is shown. On the surface of the wafer W, the first division planned line (street) S1 and the second division planned line S2 are formed orthogonally, and a plurality of sections divided by the first division planned line S1 and the second division planned line S2. A device D such as an LSI is formed in each region.

  Embodiments of the present invention for processing such a wafer W will be described in the following order. First, in this embodiment, before carrying out the division starting point forming step described in detail later, as shown in FIG. 2, the back surface Wb of the wafer W is ground to form a circular recess Wc and surround the circular recess Wc. A grinding step for forming the annular convex portion Wd is performed.

  FIG. 2 shows a grinding unit 11 for performing a grinding step. The spindle 18 is rotatably accommodated in a housing 12, the mounter 13 is fixed to the tip of the spindle 18, and the mounter 13 is screwed. The grinding wheel 21 includes a plurality of grinding wheels 52 arranged in an annular shape, and a servo motor (not shown) that rotates the spindle 18.

  A chuck table 35 is disposed below the grinding unit 11, and the wafer W is sucked and held on the chuck table 35. In the previous stage of the suction holding, a protective tape attaching step for attaching the protective tape 10 (FIGS. 1 and 5A) to the surface Wa of the wafer W in order to protect the device D is to be performed. . Then, the wafer W is held on the chuck table 35 so that the protective tape 10 is on the lower side.

  Then, while rotating the chuck table 35 in the direction indicated by the arrow 37 at, for example, 300 rpm, the grinding wheel 21 is rotated in the direction indicated by the arrow 53, for example, at 6000 rpm, and the grinding wheel 52 of the grinding wheel 21 contacts the back surface of the wafer W. Let Then, the grinding wheel 21 is ground and fed downward by a predetermined amount at a predetermined grinding feed speed.

  As a result, as shown in FIG. 2, the back surface of the device region 17 (see FIG. 1) corresponding to the region where the device D is formed is ground and removed on the back surface of the wafer W to a predetermined thickness (for example, 30 μm). A circular concave portion Wc is formed, and a region corresponding to the outer peripheral surplus region 19 (see FIG. 1) where the device D is not formed is left to form an annular convex portion (ring-shaped reinforcing portion) Wd.

  Next, as shown in FIG. 3, a division start point forming step for forming a division start point along the scheduled division line is performed on the wafer W on which a plurality of intersecting scheduled lines are set. In the present embodiment, the laser beam irradiation unit 24 of the laser processing apparatus 20 is used to irradiate the back surface Wb of the wafer W with the laser beam from the condenser 28 to form the division starting point.

  As shown in the block diagram of FIG. 4, a laser oscillation means 34 and a laser beam modulation means 36 are disposed in the casing 26 of the laser beam irradiation unit 24. As the laser oscillation means 34, a YAG laser oscillator or a YVO4 laser oscillator can be used. The laser beam modulation unit 36 includes a repetition frequency setting unit 38, a laser beam pulse width setting unit 40, and a laser beam wavelength setting unit 42.

  The repetition frequency setting means 38, the laser beam pulse width setting means 40, and the laser beam wavelength setting means 42 constituting the laser beam modulation means 36 are of known forms, and detailed description thereof is omitted in this specification.

  In the above configuration, as shown in FIG. 3, the wafer W is held on the holding surface of the chuck table 22 of the laser processing apparatus 20 via the protective tape 10, and the chuck table 22 is moved in the X-axis direction. By processing and feeding, a modified layer is formed along the planned division line S1 (FIG. 1). The chuck table 22 is index-fed in the Y-axis direction, and a modified layer is formed for all the division lines S1. Thereafter, the chuck table 22 is rotated 90 degrees, and a modified layer is similarly formed along the planned division line S2 (FIG. 2).

  In the present embodiment, since the circular concave portion Wc is formed in advance, the strength of the annular convex portion is formed by forming the modified layer on the division lines S1 and S2 (FIG. 1) within the range of the circular concave portion Wc. Decline can be prevented. However, the modified layer may be formed along the planned dividing line from one end to the other end of the outer peripheral edge of the wafer. In addition, in order to detect and align the division line arranged at the position on the back side, the laser beam irradiation unit 24 includes an imaging unit 29 having an infrared camera, or is configured with a transparent material. It can be considered that the rear surface of the wafer is imaged through the holding surface with a camera disposed below the holding surface of the chuck table.

The processing conditions in the division starting point forming step using a laser beam are set as follows, for example.
Light source: LD excitation Q switch Nd: YVO 4 pulse laser Wavelength: 1064 nm
Repetition frequency: 100 kHz
Average output: 1W
Condensing spot diameter: φ1μm
Processing feed rate: 100 mm / sec

  Further, in the division starting point forming step, the division starting point may be formed by a laser processing groove or a cutting groove by a cutting blade in addition to forming the division starting point by the modified layer. In addition, when the modified layer is formed as the division starting point as described above, the width of the planned dividing line can be reduced and the number of chips can be improved. It is preferable to form a modified layer.

  At the stage described above, as shown in FIG. 5A, the protective tape attaching step of attaching the protective tape 10 to the surface Wa of the wafer W, and as shown in FIG. A grinding step for forming the circular concave portion Wc by grinding the back surface Wb and forming the annular convex portion Wd surrounding the circular concave portion Wc, and a plurality of intersecting scheduled lines are set as shown in FIG. A split starting point forming step for forming a split starting point (modified layer 73) along the planned split line on the wafer W is performed.

  And after performing the division | segmentation starting point formation step shown in FIG.5 (C), as shown in FIG.5 (D), the adhesive film sticking step which sticks the adhesive film 30 on the back surface Wb of the wafer W is implemented. . The adhesive film 30 is called DAF (Die Attach Film) and is used for die bonding.

  In the present embodiment, the adhesive film 30 is configured in a disk shape that fits in a circular recess Wc formed in the back surface Wb of the wafer W (a range surrounded by the annular protrusion Wd). Moreover, it is good also as a structure which enables the positioning with respect to the wafer W of the adhesive film 30 by making the outer periphery of the adhesive film 30 contact the rising part (inner peripheral wall) of the cyclic | annular convex part Wd.

  Further, the adhesive film 30 can be attached to the back surface Wb of the wafer W (the bottom surface of the circular recess Wc) with a known device such as a vacuum laminator.

  Here, in the state in which the division start point forming step in FIG. 5C is performed, the division planned line is not completely cut. That is, it is not divided into individual chips. For this reason, even if the adhesive film 30 is attached to the back surface Wb of the wafer W as shown in FIG. 5D, a so-called die shift in which the chip moves does not occur.

  Next, after carrying out the adhesive film sticking step shown in FIG. 5 (D), as shown in FIG. 6, as shown in FIG. A film dividing groove forming step is performed.

  In the present embodiment shown in FIG. 6, the processing is performed with the wafer W held on the chuck table 44 by ablation processing by the laser beam LB. The wafer W is sucked and held on the holding surface 44 a of the chuck table 44 via the protective tape 10, and the adhesive film 30 is stuck on the circular recess Wc of the wafer W.

  Then, the adhesive film 30 is irradiated with a laser beam LB to form a division groove 31 along the division line S1. The dividing groove 31 may be a groove that completely cuts the adhesive film 30 or a half-cut groove that does not completely cut the adhesive film 30.

In addition, the conditions of the ablation process at the time of forming the division | segmentation groove | channel 31 in the adhesive film 30 are set as follows, for example.
Light source: LD excitation Q switch Nd: YAG pulse laser Wavelength: 355 nm (third harmonic of YAG laser)
Output: 3 to 3.75W
Repetition frequency: 10 kHz
Processing feed rate: 100 to 200 mm / sec

  In addition to performing the adhesive film dividing groove forming step by ablation processing using a laser processing apparatus as in the present embodiment, the dividing groove 31 is formed by a cutting device that forms cutting grooves with a rotating cutting blade. It is good. In this case, depending on the blade thickness and type of the cutting blade and the type of the adhesive film 30, there is a concern that the cutting blade may be clogged by cutting the adhesive film 30. In such a case, it is preferable to use a laser processing apparatus.

  After carrying out the adhesive film dividing groove forming step shown in FIG. 6, as shown in FIG. 7A, an expanded sheet attaching step for attaching the expanded sheet 60 onto the adhesive film 30 attached to the wafer W. Is implemented.

  In the present embodiment, the expanded film 60 is attached to the adhesive film 30 so that the adhesive film 30 in which the dividing grooves 31 are formed is on the upper side and the expanded sheet 60 is covered from the upper side of the adhesive film 30. . The expanded sheet 60 can be attached to the adhesive film 30 with a known device such as a vacuum laminator.

  The expand sheet 60 is provided so as to close the opening of the annular ring frame F, and the adhesive film 30 and the wafer W are fixed to the ring frame F via the expand sheet 60.

  Next, as shown in FIG. 7B, a protective tape removing step for removing the protective tape 10 from the surface Wa of the wafer W is performed. Thereby, the surface Wa of the wafer W on which the device is formed is exposed.

  Next, as shown in FIG. 7C, the wafer W fixed to the annular frame F is turned over from the state shown in FIG. 7B, and then the convex upper surface corresponding to the concave shape of the circular concave portion Wc of the wafer W. A holding step of setting the wafer W fixed to the annular frame F is performed on the chuck table 70 having 72.

  In the present embodiment, a chuck table 70 having a convex upper surface 72 inserted from below into a circular concave portion Wc of the wafer W is used, and the wafer W is covered with the rear surface Wb of the wafer W so as to cover the convex upper surface 72. Is held on the chuck table 70.

  After performing the expand sheet sticking step as described above, as shown in FIGS. 8A to 8C, the expand sheet 60 is expanded to apply an external force to the wafer W, and the wafer W and the adhesive film 30 are bonded. A dividing step of dividing the chip into individual chips and forming a plurality of chips with adhesive film 30A having the adhesive film 30 attached to the back surface is performed.

  First, as shown in FIG. 8A, a circular modified layer 74 is formed in the outer peripheral surplus region 19 by irradiating the outer peripheral surplus region 19 of the wafer W with a laser beam and rotating the chuck table 70. . The modified layer 74 is preferably provided on an extension line of the inner peripheral wall of the annular convex portion Wd.

  Next, as shown in FIG. 8B, the expanding sheet 60 is expanded by an expanding device (not shown). At this time, with respect to the wafer W, in addition to the modified layer 74 in the outer peripheral surplus region 19, the modified layer 73 has already been formed by the division starting point forming step shown in FIG. Since the dividing groove 31 is formed by the adhesive film dividing groove forming step shown in FIG. 6, the modified layers 73 and 74 are broken and divided into individual chips 80 and 80 as shown in FIG. Is done.

  In addition to performing the dividing step in the form shown in FIGS. 8A to 8C, the dividing step may be performed in the form shown in FIGS.

  First, as shown in FIG. 9A, a circular divided groove 75 is formed in the outer peripheral surplus area 19 by ablation processing with a laser beam (or cutting with a cutting blade) in the outer peripheral surplus area 19 of the wafer W. . The dividing groove 75 is preferably provided on an extension line of the inner peripheral wall of the annular convex portion Wd.

  Next, as shown in FIG. 9B, the outer peripheral surplus region 19 of the wafer W divided in a ring shape by the dividing groove 75 is removed.

  Next, as shown in FIG. 9C, the expanding sheet 60 is expanded by an expanding device (not shown). At this time, the modified layer 73 has already been formed on the wafer W by the division starting point forming step shown in FIG. 5C, and the adhesive film 30 is formed by the adhesive film dividing groove forming step shown in FIG. Since the dividing groove 31 is formed, the portion of the modified layer 73 is broken and is divided into individual chips 80 and 80 as shown in FIG.

  According to the embodiment described above, after the division starting point is formed on the wafer W, the adhesive film 30 is attached to the back surface of the wafer W before the wafer W is divided into individual chips. Thereafter, the adhesive film 30 is formed with division grooves 31 along the gaps between the chips, and the wafer W is divided into individual chips.

  According to such a method, since the wafer W is not divided at the time of adhering the adhesive film 30, a division planned line formed by a gap between chips is bent or a gap is not generated without causing a die shift. Will not disappear. And since the division | segmentation groove | channel 31 along the clearance gap between chips | tips is formed and the wafer W is divided | segmented into each chip | tip, the malfunction in the method of tearing the adhesive film 30 does not arise.

  According to the present embodiment, it is possible to form a modified layer using a laser beam, which is a suitable operation for a workpiece having a narrow division line.

  Further, the annular convex portion Wd formed simultaneously with the formation of the circular concave portion Wc can function as an outer peripheral reinforcing portion, and it is possible to safely handle the thin wafer W in a state where the division starting point is applied. Become. In addition, by forming the annular convex portion Wd (outer peripheral reinforcing portion) on the wafer W, even if some chips are divided starting from the division starting point during handling, Since the protective tape 10 affixed to the surface is not bent and the arrangement of other chips is not affected, there is no possibility of die shift.

  Moreover, since the division | segmentation groove | channel 31 is formed, the division | segmentation of the adhesive film 30 becomes easy, and also the adhesive film 30 can be reliably divided | segmented in all the area | regions. In particular, the present invention can be suitably applied to the formation of a thin and small chip with an adhesive film and a wafer having a large diameter of 12 inches.

  On the other hand, as a device configuration to reduce the handling risk of thin wafers (defects such as damage that occurs during handling), the laser processing device and cutting device for forming the split starting point, and the grinding device and tape applicator are connected in-line. It is conceivable to adopt a configuration (a configuration in which a plurality of devices are combined as one device).

  In this case, the process for forming the division start point (division start point formation step) takes a long time compared to other processes. In particular, for wafers on which small chips (minimum chips) are formed, the number and distance of the division starting points increase, so that a long time is required for the process for forming the division starting points, and UPH per unit time is increased. (Unit Per Hour: number of processed sheets)) will be poor. When the wafer has a large diameter, the number and the distance of the division starting points further increase, so that the UPH is further deteriorated.

  For this reason, in the case of adopting an in-line connection configuration, there is no balance between the UPH of the laser processing apparatus or the cutting apparatus for forming the division starting point and the UPH of the grinding apparatus or the tape applicator. The time when the apparatus and the tape applicator are not operating increases, and the CoO (Cost Of Operation) deteriorates.

  In this respect, in this embodiment, the wafer W is not simply thinned, but by leaving the annular convex portion Wd on the outer periphery, the strength of the wafer W is increased and the handling risk is reduced. Thus, the risk of deterioration of CoO is reduced, and good CoO can be realized as a whole process.

  Further, in the case of not using the in-line as described above, the laser for forming the division start point can be obtained by separately operating the laser processing apparatus and cutting apparatus for forming the division start point, and the grinding apparatus and the tape applicator. The UPH of the processing apparatus or the cutting apparatus can be prevented from affecting the UPH of the grinding apparatus or the tape applicator, and more wafers can be processed.

  In the embodiment described above, the grinding step for forming the circular concave portion and the annular convex portion is performed. However, the thinning is performed so that the wafer is entirely thinned without forming the circular concave portion and the annular convex portion. It is good also as implementing a division | segmentation base point formation step, an adhesive film sticking step, an adhesive film division | segmentation groove | channel formation step, an expanded sheet sticking step, and a division | segmentation step after that. In addition, after performing the division starting point forming step, a thinning step for thinning the wafer is performed, and then an adhesive film attaching step, an adhesive film dividing groove forming step, an expanded sheet attaching step, and a dividing step are executed. May be.

DESCRIPTION OF SYMBOLS 10 Protective tape 30 Adhesive film 31 Divided groove 60 Expand sheet 73 Modified layer 74 Modified layer 74 Modified layer 75 Divided groove W Wafer Wa Surface Wb Back surface Wc Circular recess Wd Annular convex

Claims (2)

A method for forming a chip with an adhesive film that forms a chip with an adhesive film having an adhesive film attached to the back surface,
A split starting point forming step for forming a split starting point along the planned split line on a wafer set with a plurality of split target lines intersecting; and
After carrying out the split starting point forming step, an adhesive film attaching step for attaching an adhesive film to the back surface of the wafer;
After performing the adhesive film sticking step, an adhesive film split groove forming step for forming a split groove along the planned split line on the adhesive film with laser beam irradiation or a cutting blade;
After performing the adhesive film dividing groove forming step, an expanded sheet attaching step of attaching an expanded sheet on the adhesive film attached to the wafer;
After performing the expanding sheet attaching step, the expanding sheet was expanded to apply an external force to the wafer to divide the wafer and the adhesive film into individual chips, and the adhesive film was attached to the back surface. A dividing step of forming a plurality of chips with adhesive film;
Before carrying out the split starting point forming step, the back surface of the wafer is ground to form a circular concave portion, and a grinding step to form an annular convex portion surrounding the circular concave portion;
Equipped with a,
Bonding said a division start point forming step, to form a modified layer to be a division originating points by irradiating a laser beam to the backside of the wafer, characterized in that the peripheral marginal region of the wafer does not form a circular modified layer A method for forming a chip with a film. 2. The chip with an adhesive film according to claim 1, wherein in the dividing step, a circular modified layer or a dividing groove is formed from the surface of the wafer to the outer peripheral surplus area before expanding the expanded sheet. Forming method.

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