TWI640036B - Processing method of wafer - Google Patents

Abstract

The object of the present invention is to divide a wafer having a ring-shaped convex portion on the outer periphery of the back surface into individual elements without deteriorating the quality. The solution is the processing method of the present invention. By grinding only the back surface corresponding to the element formation region, a crystal with a ring-shaped convex portion for reinforcement is formed on the back surface corresponding to the remaining peripheral area surrounding the element formation region. A method for processing a circularly divided wafer includes forming a separation groove at a boundary between a ring-shaped convex portion and a concave portion of a wafer in a state where a protective tape is attached to the front surface of the wafer, and a back surface of the wafer is formed. A dicing tape is attached to the side, and the protective tape and the annular protrusion are removed from the front side of the wafer, and the element formation area of the wafer is divided into individual elements.

Description

Processing method of wafer Field of invention

The present invention relates to a processing method for dividing a wafer having a ring-shaped convex portion formed on the outer periphery of the back surface of the wafer into individual wafers.

Background of the invention

In recent years, in order to reduce the weight and miniaturization of electrical machines, the thickness of wafers has been required to be thinner, for example, 50 μm or less. A thin wafer formed in this way will not only reduce rigidity but also warp. Therefore, handling and handling may become difficult, and there is a risk of damage during transportation and the like. Therefore, there is a method of grinding only the back surface corresponding to the element formation region where the element is formed on the wafer, and forming a ring-shaped convex portion for reinforcement on the back surface corresponding to the outer peripheral area surrounding the element formation region. A grinding method has been proposed (see, for example, Patent Document 1).

As a method of dividing such a wafer along a predetermined division line, a method of removing a ring-shaped convex portion before dividing a wafer has been proposed (see, for example, Patent Document 2). In this method, a dicing tape is attached along the back surface of the wafer protruding with the annular convex portion, and the back side of the wafer is supported on the work clamp table through the dicing tape. On the work clamp table, the porous part protruding from the top surface of the table is inserted into the recess of the wafer, and the wafer is removed from the wafer by a cutting blade. Cut the ring-shaped convex part away from the front side. After that, the wafer is cut from the front side with a cutting blade and divided into individual elements.

Prior art literature Patent literature

Patent Document 1: Japanese Patent Laid-Open No. 2007-173487

Patent Document 2: Japanese Patent Laid-Open No. 2010-186971

Summary of invention

In the method described in Patent Document 2, since a circular convex portion and a concave portion are formed on the back surface of the wafer, if a dicing tape is attached along the back surface of the wafer, the corners of the concave portion of the wafer are formed. There are bubbles remaining. When cutting the ring-shaped convex portion from the wafer, when the cutting blade is cut from the front side of the wafer toward the back surface where the recess is formed, the cutting blade may be shaken due to air bubbles, or cutting chips may enter the air bubbles. , Which has a bad impact on the wafer. Therefore, on the wafer from which the ring-shaped convex portion has been removed, there is a problem that the element quality on the outer peripheral side of the wafer is deteriorated.

The present invention has been made in view of such a problem, and an object thereof is to provide a wafer that can be divided into individual elements without deteriorating the quality of a wafer in which a ring-shaped convex portion is formed on the outer periphery of the back surface. processing method.

The wafer processing method of the present invention is a wafer processing method in which a substantially circular element formation region having a plurality of elements formed by dividing a predetermined line on the front surface and a remaining region surrounding the periphery of the element formation region is processed. A method is composed of the following steps: a recess forming step, attaching a protective tape on the front side of a wafer, and grinding only a region on the back side corresponding to the element formation region of the wafer to a predetermined thickness to make the element The formation area is thinned to a desired thickness, a recess is formed on the back surface, and a ring-shaped convex portion protruding from the back side is formed in the remaining area of the outer periphery; the ring-shaped convex portion dividing step is performed on the ring after the recess forming step is performed. A circular dividing groove is formed at the boundary between the convex portion and the concave portion, and the annular convex portion and the concave portion are divided; in the transfer step, after the annular convex portion dividing step is performed, the dividing groove is on the back of the wafer. A cutting tape is attached to the entire inner surface of the substrate, and the protective tape is peeled off, and the ring-shaped convex portion is removed; and a step of dividing the element formation region, after performing the transfer step, division is performed along a predetermined division line of the element formation region. .

With this configuration, a circular division groove can be formed at the boundary between the annular convex portion and the concave portion on the back side of the wafer in a state where the protective tape is attached to the front side of the wafer. Therefore, when the dicing tape is attached to the back surface of the wafer, the air between the back surface of the wafer and the dicing tape can run into the dividing groove. According to this, the wafer can be affixed by attaching a dicing tape with no air bubbles remaining on the entire back surface of the wafer, peeling off the protective tape from the front side of the wafer, and removing the annular protrusion from the wafer. Good transfer from protective tape to cutting tape. In addition, since the wafer is divided with no bubbles remaining on the back surface of the wafer, the quality of the device does not decrease due to the influence of the bubbles.

According to the present invention, before a dicing tape is attached to the back surface of a wafer, a dividing groove is formed at the boundary between the annular convex portion and the concave portion, so that the wafer having the annular convex portion formed on the outer periphery of the back surface can be placed on the wafer. Without deteriorating the quality, it is divided into individual elements.

11‧‧‧ Front of the wafer

The back of the 12‧‧‧ wafer

13, 19‧‧‧ outer edge

14‧‧‧ gap

15‧‧‧ recess

16‧‧‧ annular projection

17‧‧‧ divided trench

18‧‧‧ divided scheduled line

21‧‧‧Grinding device

22, 32‧‧‧Work clamp

23‧‧‧Grinding Wheel

26‧‧‧Cutting Chips

31‧‧‧ cutting device

33‧‧‧ cutting insert

34‧‧‧Jig Department

A1‧‧‧Element formation area

A2‧‧‧External area

D‧‧‧Element

F‧‧‧ ring frame

T1‧‧‧Protection tape

T2‧‧‧Cutting Tape

W‧‧‧ Wafer

X, Y, Z‧‧‧ directions

FIG. 1 is a perspective view of a wafer according to this embodiment.

FIG. 2 is a diagram showing an example of a step of forming a recessed portion in this embodiment.

FIG. 3 is a diagram showing an example of a step of dividing an annular convex portion according to the present embodiment.

4A to 4C are diagrams showing an example of a transfer procedure in this embodiment.

FIG. 5 is a diagram showing an example of a step of dividing the element formation region according to this embodiment.

6A to 6C are explanatory diagrams of a wafer processing method of a comparative example.

Forms used to implement the invention

The wafer processing method of this embodiment is performed on a so-called TAIKO wafer in which only the outer peripheral portion of the back surface of the wafer is retained and only the inner side is ground. In the case where the wafer is divided into individual elements, when only the center of the back surface of the wafer is thinned into a concave shape, the back surface side of the wafer cannot be made because the outer peripheral portion protrudes from the back surface side of the wafer. Keep on the work clamp. Therefore, the wafer is usually divided into individual wafers after the outer periphery of the wafer is removed and the back surface of the wafer is flattened.

At this time, although dicing tape must be attached to the back of the wafer, Since the peripheral portion protrudes from the back surface of the wafer, air bubbles remain between the back surface of the wafer and the dicing tape. Therefore, in the wafer processing method of this embodiment, before the dicing tape is attached to the back surface of the wafer, a division that becomes a discharge path for air bubbles is formed at the boundary between the concave portion and the peripheral portion of the wafer. ditch. This makes it possible to attach the dicing tape to the entire back surface of the wafer without any gap even if the outer peripheral portion of the wafer is formed.

Hereinafter, a method for processing a wafer according to this embodiment will be described in detail with reference to the attached drawings. FIG. 1 is a perspective view of a wafer according to this embodiment. FIG. 2 is a diagram showing an example of a step of forming a recessed portion in this embodiment. FIG. 3 is a diagram showing an example of a step of dividing an annular convex portion according to the present embodiment. FIG. 4 is a diagram showing an example of a transfer procedure in this embodiment. FIG. 5 is a diagram showing an example of a step of dividing the element formation region according to this embodiment.

As shown in FIG. 1, the wafer W is formed into a substantially circular plate shape, and is divided into a plurality of regions by grid-like predetermined division lines 18 arranged on the front surface 11. In the center of the wafer W, an element D is formed in each region divided by the planned division line 18. The front surface 11 of the wafer W can be divided into an element formation area A1 where a plurality of elements D are formed, and an area A2 remaining around the periphery of the element formation area A1. In addition, a notch 14 indicating a crystal orientation is formed on the outer edge 13 of the wafer W. The wafer W is carried into the grinding device 21 with the protective tape T1 attached to the front surface 11 (see FIG. 2).

As shown in FIG. 2, a recessed portion forming step is first performed. In the recess forming step, the front surface 11 side of the wafer W is held on the work table 22 of the grinding device 21 through the protective tape T1. Then, while making the grinding device 21 The grinding wheel 23 rotates around the Z axis while approaching the work table 22, and the grinding wheel 23 and the back surface 12 of the wafer W are brought into rotational contact with each other to grind the wafer W. At this time, of the back surface 12 of the wafer W, only the back side of the element formation region A1 of the front surface 11 is ground. Thereby, on the back surface 12 of the wafer W, a region corresponding to the element formation region A1 can be thinned to a desired thickness to form a circular recess 15, and a region corresponding to the remaining peripheral region A2 can be transferred from the wafer W. The back surface 12 side protrudes to form an annular convex portion 16.

In this way, only the central portion of the wafer W is thinned by the recessed portion 15, and the rigidity of the wafer W can be improved by the annular convex portion 16 surrounding the recessed portion 15. Accordingly, while the element formation region A1 of the wafer W is thinned, the warpage of the wafer W can be suppressed by the ring-shaped convex portion 16 and breakage during transportation can be prevented. Furthermore, the wafer W may be a semiconductor wafer such as silicon or gallium arsenide, or may be a ceramic, glass, or sapphire optical element wafer. The wafer W on which the concave portion 15 and the annular convex portion 16 are formed is carried into the cutting device 31 with the protective tape T1 attached (see FIG. 3).

As shown in FIG. 3, a ring-shaped convex portion dividing step is performed after the concave portion forming step. In the ring-shaped convex portion dividing step, the front surface 11 side of the wafer W is held on the work table 32 of the cutting device 31 through the protective tape T1. At this time, the wafer W is aligned with respect to the work stage 32 so that the center of the wafer W is aligned with the rotation axis (Z axis) of the work stage 32. In addition, the cutting insert 33 is positioned at the boundary between the annular convex portion 16 and the concave portion 15 of the wafer W, and the cutting insert 33 rotated at a high speed is cut into the annular convex portion 16 and the concave portion 15 from the back surface 12 side of the wafer W. Junction.

In addition, when cutting into the half of the protective tape T1 with the cutting blade 33 In the middle of the waist, the work clamp 32 is rotated to cut the wafer W into a circle by the cutting blade 33. Thereby, a circular division groove 17 can be formed between the concave portion 15 and the annular convex portion 16 along the outer periphery of the wafer W, and the annular convex portion 16 can be cut away from the wafer W. The wafer W having the division grooves 17 formed therein is carried into a transfer device (not shown). At this time, the element formation region A1 of the wafer W is conveyed in a state of being supported by the annular convex portion 16 through the protective tape T1. That is, the ring-shaped convex portion 16 functions as a ring-shaped frame to suppress the warpage of the thinned element formation region A1 of the wafer W.

The ring-shaped convex portion dividing step is not limited to the cutting step (circle cut) by the cutting insert 33. The ring-shaped convex portion dividing step may have a configuration in which a dividing groove 17 can be formed between the circular concave portion 15 and the ring-shaped convex portion 16 of the wafer W. For example, a wafer W The ablation process is performed by a laser beam having an absorptive wavelength. The so-called ablation means that when the irradiation intensity of the laser beam is above a predetermined processing threshold, the solid surface is converted into electronic, thermal, optical science, and mechanical energy. As a result, neutral atoms, The phenomenon that molecules, positive and negative ions, free radicals, clusters, electrons, and light are rapidly released and the solid surface is etched.

As shown in FIG. 4, the transfer step can be performed after the step of dividing the annular convex portion. In the transfer step, as shown in FIG. 4A, a dicing tape T2 is attached along the back surface 12 of the wafer W. At this time, for example, the wafer W is placed on the inside of the ring frame F on a platform in a decompression space of a transfer device, and the dicing tape T2 is pressed against the wafer with a circular plate corresponding to the recess 15 of the wafer W.圆 W 的 背 12。 Round W of the back 12. Then, while pulling the cutting tape T2 radially outward, A dicing tape T2 is attached from the center of the back surface 12 of the wafer W toward the radially outer side.

When attaching this dicing tape T2, as shown in FIG. 4B, the air between the back surface 12 of the wafer W and the dicing tape T2 can be extruded to the outside in the radial direction so that it runs to the annular convex portion 16 and the concave portion 15 at the junction of the divisional ditch 17. Therefore, bubbles 25 (refer to FIG. 6) do not remain on the back surface 12 side of the wafer W, and the dicing tape T2 can be adhered to the inner side of the dividing groove 17 on the back surface 12 of the wafer W well. The whole part. Next, as shown in FIG. 4C, the protective tape T1 is peeled from the front surface 11 of the wafer W, and the annular convex portion 16 is further removed from the dicing tape T2. Thereby, the element formation area A1 of the wafer W can be left on the dicing tape T2. The wafer W transferred to the dicing tape T2 is carried into the cutting device 31 (see FIG. 5) again. Moreover, peeling of the protective tape T1 and removal of the ring-shaped convex portion 16 may be performed by a transfer device, or may be performed manually by an operator.

Moreover, in this embodiment, the removal of the annular convex portion 16 is not performed in the cutting device 31 immediately after the annular convex portion dividing step is completed, but is performed after the transfer is performed on the transfer device. In the case where the removal of the annular convex portion 16 is performed automatically, for example, in the device shown in Japanese Patent Laid-Open No. 2013-098246, the scraper is implemented in a state where tension is applied to the tape. Because only the protective tape T1 of the same size is affixed to the wafer W after the ring-shaped convex portion dividing step, the ring-shaped convex portion 16 cannot be removed by a scraper before the cutting tape T2 is attached in the transfer step. Therefore, as long as the transfer step is not performed, it becomes difficult to automatically remove the annular convex portion 16.

In addition, by crystallizing at a stage before the recess forming step, A configuration in which the circle W is held on the annular frame F to remove the annular convex portion 16 in the cutting device 31 may be considered. However, in order to perform a recess formation step for the wafer W supported on the annular frame F in the grinding device 21, it is necessary to improve the grinding device 21 itself, which has a problem of increasing costs. As described above, in this embodiment, the wafer W is transferred to the transfer device so that the wafer W is transferred from the protective tape T1 to the dicing tape T2 in the transfer device. Therefore, the annular protrusion can be implemented with a simple structure. Removal of 16. Furthermore, as described above, when the wafer W is transferred to the transfer device, the ring-shaped convex portion 16 functions as a ring frame, so that it is possible to prevent deflection of the element formation region A1 that has been thinned by the wafer W. Damage caused by damage.

As shown in FIG. 5, the element forming region division step can be performed after the transfer step. In the element formation region dividing step, the back surface 12 side of the wafer W is held on the work clamp table 32 by the dicing tape T2, and the ring frame F around the wafer W is fixed and held by the clamp portion 34. The cutting blade 33 is positionally aligned with respect to the planned division line 18 on the radially outer side of the wafer W, and is lowered at this position to a height at which it can cut into the half-middle waist of the dicing tape T2. Then, the wafer W on the work table 32 is cut and fed in the X-axis direction with respect to the cutting blade 33 that rotates at a high speed, so that the wafer W can be cut along the predetermined division line 18.

After the wafer W is cut along one of the planned division lines 18, the cutting blade 33 can be aligned with the adjacent planned division line 18 for cutting. This operation is repeated to cut the wafer W along all the predetermined division lines 18 in one direction. After cutting along all the division lines 18 in one direction of the wafer W, the work clamp 32 can be rotated 90 degrees, and the same can be performed. On the other hand, the wafer W is cut along a predetermined division line 18 perpendicular to the predetermined division line 18 in the other direction. As a result, only the thinned element formation region A1 is subjected to a full cut along the planned division line 18, and the wafer W can be divided into a plurality of elements D.

As described above, in the processing method of the wafer W of the present embodiment, the dicing tape T2 is well adhered to the entire back surface 12 of the element formation region A1 of the wafer W, and therefore, it is not applied when the element formation region A1 is divided. , Which causes the quality of the component D to deteriorate. That is, since no gap is formed between the outer edge 19 of the element formation area A1 and the dicing tape T2 (see FIG. 6C), there is no possibility that cutting chips enter this gap. Accordingly, the wafer W on which the annular convex portion 16 is formed can be divided into individual elements D without deteriorating the quality.

In addition, the element formation region division step is not limited to the division step of mechanical dicing by the cutting blade 33. The element formation region dividing step may be performed as long as the element formation region A1 can be divided along the predetermined division line 18. For example, the element formation region is divided by an ablation process using a laser beam having a wavelength absorptive to the wafer W. It may be implemented by stealth dicing (registered trademark) using a laser beam having a wavelength that is transparent to the wafer W.

In the stealth dicing, a modified layer is formed along a predetermined division line 18, and an external force is applied to the wafer W to divide the modified device into individual elements D with the modified layer as a starting point. Furthermore, the modified layer refers to a state in which the density, refractive index, mechanical strength, and other physical characteristics of the wafer W are different from the surroundings by the irradiation of the laser beam, and the intensity is lower than the surroundings. region. The modified layer may be, for example, a melt-treated region, a crack region, an insulation breakdown region, a refractive index change region, or a region obtained by mixing these.

Here, in order to compare with the present invention, a method of processing a wafer of a comparative example will be briefly described with reference to FIG. 6. FIG. 6 is an explanatory diagram of a wafer processing method of a comparative example. The method of processing the wafer of the comparative example is different from the method of processing the wafer of the present embodiment in that a dicing tape is attached to the back surface of the wafer and then the annular convex portion is cut away from the wafer. The configuration in which the annular convex portion and the concave portion are formed on the back surface of the wafer is the same as the present embodiment, and therefore description thereof is omitted. In addition, in the comparative example, for convenience of explanation, the same names are given the same reference numerals for explanation.

As shown in FIG. 6A, in the processing method of the wafer W of the comparative example, a dicing tape T2 is attached along the back surface 12 of the wafer W before forming the split groove 17 (see FIG. 6B). Therefore, when there is no air discharge channel between the back surface 12 of the wafer W and the dicing tape T2, air bubbles 25 may remain in the corners of the annular convex portion 16 and the concave portion 15 of the back surface 12 of the wafer W. Therefore, the dicing tape T2 cannot be attached to the outer edge side of the element formation region A1 of the wafer W. When the wafer W is supported on the ring frame F (see FIG. 4) through the dicing tape T2, the protective tape T1 can be peeled from the front surface 11 of the wafer W.

Next, as shown in FIG. 6B, a circular cutting groove 17 is formed at the boundary between the annular convex portion 16 and the concave portion 15 of the wafer W by the cutting insert 33. At this time, because the cutting edge of the cutting insert 33 enters the air bubble 25, the cutting insert 33 will oscillate and the machining quality will be reduced, and the cutting chips 26 will enter the air bubble 25 and cause pollution. When the dividing groove 17 is formed in the wafer W, the annular convex portion 16 of the wafer W can be removed from the dicing tape T2. Secondly, As shown in FIG. 6C, the wafer W is cut by the cutting blade 33 along the planned division line 18 (see FIG. 5), and the wafer W is divided into individual elements D. At this time, because the dicing tape T2 is not adhered to the outer edge 19 of the wafer W, cutting chips 26 may enter the gap between the outer edge 19 of the wafer W and the dicing tape T2, and the quality of the component D may be deteriorated.

As described above, in the method of processing the wafer W of the comparative example, in particular, the quality of the element D on the outer peripheral side of the wafer W is deteriorated. On the other hand, in the method of processing the wafer W of this embodiment, there is no air bubble 25 remaining between the back surface 12 of the wafer W and the dicing tape T2, such as the method of processing the wafer W of the comparative example. In this case, the quality of the element D on the outer peripheral side of the wafer W is not deteriorated due to the bubbles 25.

As described above, according to the method for processing a wafer W according to this embodiment, the protective tape T1 is attached to the front surface 11 side of the wafer W, and the annular protrusions 16 and A circular dividing groove 17 is formed at the boundary of the recessed portion 15. Therefore, when attaching the dicing tape T2 to the back surface 12 of the wafer W, the air between the back surface 12 of the wafer W and the dicing tape T2 can be caused to run to the dividing groove 17. Therefore, the dicing tape T2 can be attached without leaving bubbles 25 on the entire back surface 12 of the wafer W, and the protective tape T1 can be peeled off from the front surface 11 of the wafer W, and the annular convex portion 16 can be removed. With this, the wafer W can be well transferred from the protective tape T1 to the dicing tape T2. In addition, since the wafer W is divided in a state where no bubbles 25 remain on the back surface 12 of the wafer W, the quality of the element W does not decrease due to the influence of the bubbles 25.

Furthermore, the present invention is not limited to the above-mentioned embodiments, and can be developed Implement various changes. In the embodiment described above, the size, shape, and the like shown in the drawings are not limited to this, and may be appropriately changed within the range in which the effects of the present invention are exhibited. In addition, as long as it does not deviate from the range of the objective of this invention, it can implement suitably, and can implement it.

In the above-mentioned processing method of the wafer W, although the configuration in which the wafer W is transferred to the dicing tape T2 attached to the ring frame F in the transfer step is not limited to this configuration. In the transfer step, as long as the dicing tape T2 can be attached to the back surface 12 of the wafer W, and the protective tape T1 can be peeled off from the front surface 11 of the wafer W, even if the wafer W is not supported in a ring shape through the dicing tape T2 Frame F is also available.

Industrial availability

As described above, the present invention has the effect of being able to be divided into individual elements without deteriorating the quality, and is divided into individual elements on a wafer having a ring-shaped convex portion formed on the outer periphery of the back surface of the wafer. Is useful in wafer processing methods.

Claims (1)

A wafer processing method is a wafer processing method including a substantially circular element formation region having a plurality of elements formed by dividing a predetermined line on a front surface, and a wafer surrounding a remaining area around the periphery of the element formation region. It is composed of the following steps: a recess forming step, attaching a protective tape on the front side of the wafer, and grinding only the area on the back side corresponding to the element formation area of the wafer to a predetermined thickness to make the element formation area thin It is reduced to a desired thickness, and a recessed portion is formed on the back surface, and an annular convex portion protruding from the back side is formed in the remaining area of the outer periphery; the annular convex portion is divided, and after the recessed portion forming step is performed, the annular convex portion is formed. A circular dividing groove is formed at the boundary with the concave portion, and the annular convex portion and the concave portion are divided; in the transfer step, after the annular convex portion dividing step is performed, the inside of the dividing groove on the back surface of the wafer is adjusted. Adhere a dicing tape, peel off the protective tape, and remove the ring-shaped convex portion; and a step of dividing the element formation region, and after performing the transfer step, follow the element formation region The dividing line is divided, in this transferring step, along the backside of the wafer radially outward from the center of the wafer back surface of the dicing tape attaching.