Chip manufacturing process

Abstract

A chip manufacturing method for manufacturing chips from a wafer (13) having a back surface (13d) to which a central portion of a tape (17) is attached, the outer peripheral portion of which is attached to an annular frame (19), the back surface (13d) having a recessed portion (13e) formed thereon such that a component region (13b) in which a plurality of components (15) are formed is thinned and that an outer peripheral excess portion surrounding the component region (13b) remains as an annular reinforcing portion (14), the method comprising: a singulation step of singulating the plurality of components (15) and producing the chips by processing the wafer (13) along boundaries of the plurality of components (15); and a removing step of removing the annular reinforcing portion (14) using a rotating cutting blade (6c) after the singulating step.

Description

BACKGROUND OF THE INVENTIONField of the invention

[0001] The present invention relates to a chip manufacturing method for manufacturing chips from a wafer having a back surface to which a central portion of a tape is attached, the outer peripheral portion of which is attached to an annular frame, the back surface having a depressed portion formed so that a component region in which a plurality of components are formed is thinned and an outer peripheral excess portion surrounding the component region remains as an annular reinforcing portion. Description of the state of the art

[0002] Device chips, such as integrated circuits (ICs), are essential components in various electronic devices such as mobile phones and personal computers. Such chips are manufactured, for example, by dividing a wafer, which has a device region on a front side in which a plurality of devices are formed, and an outer peripheral excess region surrounding the device region, along boundaries of the plurality of devices, i.e., by singulating the plurality of device chips.

[0003] This wafer is sometimes thinned before dividing to make the chips to be manufactured small. One example of a wafer thinning process is grinding using a holding table to hold the wafer and a grinding wheel arranged above the holding table, which has several discrete grinding stones arranged in a ring. This grinding is typically performed in the following sequence.

[0004] First, the wafer is held on the holding table so that its back surface is exposed. Next, the holding table is moved so that the center of the back surface of the wafer is positioned directly under a location of the multiple grinding stones, which is pulled as the grinding wheel rotates. Next, while both the grinding wheel and the holding table are rotated, the grinding wheel is lowered so that the multiple grinding stones and the back surface of the wafer come into contact with each other. This results in the back surface of the wafer being ground, and the wafer being thinned.

[0005] However, thinning the wafer reduces its strength, making it more prone to breakage. Therefore, a method has been proposed for forming a recessed portion on the back surface of the wafer in such a way that the device region of the wafer is thinned and the outer peripheral excess portion remains as an annular reinforcement portion. In this method, the recessed portion on the back surface of the wafer is formed by grinding the back surface of the wafer as described above using a grinding wheel with an outer diameter smaller than the radius of the wafer.

[0006] Furthermore, since the annular reinforcement portion is no longer needed at the time of manufacturing components from this wafer, the annular reinforcement portion is sometimes removed by grinding prior to singulation of the multiple components. However, when the annular reinforcement portion is ground, the force applied by this grinding poses a risk of chipping of the component region connected to the annular reinforcement portion or damage to the components contained in the component region due to cracks extending into the component region.

[0007] In view of the above-mentioned situations, a technique has been proposed in which the device region and the annular reinforcement portion are separated by dividing the wafer along the outer periphery of the device region before removing the annular reinforcement portion by grinding (see, for example, Japanese Patent Application Laid-Open No. 2021-72353). This can prevent damage to the devices present in the device region.

[0008] Further information helpful for understanding the present invention can be found in the following documents: JP 2014- 207 386 A relates to a wafer processing method capable of preventing the occurrence of chipping. DE 10 2021 204 071 A1 relates to a wafer processing method comprising a preparation step, a foil arranging step, a holding step, a cutting step and a step of removing an annular protrusion portion. PRESENTATION OF THE INVENTION

[0009] However, if the wafer is split along the outer perimeter of the component area, which is being thinned, there is a risk of damaging the components contained in the component area due to the force applied during this splitting. This splitting must be performed slowly to avoid negative effects on the component area, resulting in low productivity of the chips manufactured from this wafer.

[0010] In view of the above circumstances, an object of the present invention is to provide a chip manufacturing method capable of preventing damage to components at the time of removing the annular reinforcing portion and improving the productivity of chips to be manufactured from a wafer.

[0011] According to one aspect of the present invention, there is provided a chip manufacturing method for manufacturing chips from a wafer having a back surface to which a central region of a tape is attached, the outer peripheral portion of which is fixed to an annular frame, the back surface having a depressed portion formed thereon such that a device region in which a plurality of devices are formed is made thin and that an outer peripheral excess region surrounding the device region remains as an annular reinforcement portion, the method comprising: a dicing step of dicing the plurality of devices and manufacturing the chips by processing the wafer along boundaries of the plurality of devices; and a removing step of removing the annular reinforcement portion using a rotating cutting blade after the dicing step.

[0012] Preferably, in the singulation step, the plurality of components are singulated using a rotating cutting blade for singulation or a laser beam having a wavelength absorbable by the wafer.

[0013] In the present invention, the singulation step of singulating the plurality of components and manufacturing chips is performed before the removal step of removing the annular reinforcement portion. That is, in the present invention, the removal step is performed in a state where the annular reinforcement portion and the chips of the plurality of components are separated. Therefore, the present invention can prevent damage to components that might be caused by the force applied to the annular reinforcement portion in the removal step.

[0014] Furthermore, in the present invention, without performing the step of separating the device region of the wafer and the annular reinforcement portion, the annular reinforcement portion can be removed, and the chips of the plurality of devices can be manufactured. Therefore, in the present invention, chip productivity can be improved compared to the chip manufacturing method including such a step.

[0015] The above and other objects, features and advantages of the present invention, as well as the modes for carrying them into effect, will best become apparent and the invention itself will be best understood by studying the following description and appended claims, with reference to the attached drawings which illustrate a preferred embodiment of the invention. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1A is a perspective view schematically illustrating an example of a frame unit having a wafer; Fig. Figure 1B is a cross-sectional view schematically showing the Fig. 1A shows the frame unit; Fig. 2 is a flowchart schematically illustrating an example of a chip manufacturing method for manufacturing chips from the wafer included in the frame unit; Fig. 3A is a partially cross-sectional side view schematically illustrating an example of a singulation step; Fig. 3B is a partially cross-sectional side view schematically illustrating another example of the singulation step; Fig. 4A is a partially cross-sectional side view schematically illustrating an example of a removal step; Fig. 4B is a partially cross-sectional side view schematically illustrating an example of the removal step; Fig. 4C is a partially cross-sectional side view schematically illustrating an example of the removal step; Fig. 5A is a partially cross-sectional side view schematically illustrating another example of the removal step; and Fig. 5B is a partial cross-sectional side view schematically illustrating the other example of the removal step. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0016] An embodiment of the present invention will be described with reference to the accompanying drawings. Fig. 1A is a perspective view schematically illustrating an example of a frame unit having a wafer. Fig. Figure 1B is a cross-sectional view schematically showing the Fig. 1A. A frame unit shown in Fig. 1A and Fig. The frame unit 11 shown in Figure 1B has a wafer 13 whose front side 13a is exposed.

[0017] The wafer 13 is formed, for example, from a single-crystal semiconductor material such as silicon (Si), silicon carbide (SiC), or gallium nitride (GaN). Furthermore, the wafer 13 has a device region 13b in which a plurality of devices 15 are formed, as well as an outer peripheral excess region 13c surrounding the device region 13b.

[0018] In the component region 13b, the boundaries of the plurality of components 15 are defined in a grid pattern, and each of the plurality of linear sections provided within these boundaries is also referred to as a designated dividing line. Furthermore, a recessed portion 13e is formed on a back surface 13d of the wafer 13 such that the component region 13b is thinned and the outer peripheral excess portion 13c remains as an annular reinforcement portion 14.

[0019] Furthermore, a central portion of a circular plate-shaped tape 17 having a larger diameter than the wafer 13 is attached to the back surface 13d of the wafer 13 so that the central portion comes into close contact with the wafer 13 at the recessed portion 13e without a gap. The tape 17 includes, for example, a film-shaped flexible base and an adhesive layer provided on the side of the wafer 13.

[0020] The base of the tape is made of materials such as polyolefin (PO), polyethylene terephthalate (PET), polyvinyl chloride (PVC), or polystyrene (PS). The adhesive layer is made of materials such as ultraviolet-curable silicone rubber, an acrylic material, or an epoxy material.

[0021] Furthermore, an annular frame 19 is fixed to an outer peripheral portion of the belt 17, which has an inner diameter larger than the diameter of the wafer 13. The annular frame 19 is formed, for example, from a metallic material such as aluminum or stainless steel.

[0022] Fig. 2 is a flowchart schematically illustrating an example of the chip manufacturing process from the wafer 13 provided in the frame unit 11. In this process, the wafer 13 is first processed along the boundaries of the plurality of components 15 to singulate the plurality of components 15 and thereby manufacture chips (singulation step: S1).

[0023] Fig. Figure 3A is a partially cross-sectional side view schematically illustrating an example of the singulation step (S1). In simpler terms, Fig. 3A shows a way of separating a plurality of components 15 using a rotating cutting blade (separation cutting blade) in a cutting device.

[0024] Note that an X1-axis direction and a Y1-axis direction defined in Fig. 3A are directions perpendicular to each other on a horizontal plane, and a Z1-axis direction is a direction (vertical direction) perpendicular to both the X1-axis direction and the Y1-axis direction.

[0025] One in Fig. The cutting apparatus 2 shown in Figure 3A includes a holding table 4. The holding table 4 includes a circular plate-shaped frame body 4a whose diameter is slightly smaller than the diameter of the recessed portion 13e formed on the back surface 13d of the wafer 13.

[0026] The frame body 4a is formed, for example, from a metallic material such as stainless steel or ceramic. Furthermore, the frame body 4a includes a circular plate-shaped bottom wall and a cylindrical side wall erected from an outer peripheral portion of the bottom wall. That is, a circular plate-shaped recessed portion defined by the bottom wall and the side wall is formed on one side of an upper surface of the frame body 4a.

[0027] Furthermore, a circular plate-shaped porous plate (not shown) having a diameter substantially equal to the diameter of the recessed portion is fixed to the recessed portion formed on the upper surface side of the frame body 4a. This porous plate is made of, for example, porous ceramic.

[0028] The holding table 4 is connected to an X1-axis direction movement mechanism (not shown). The X1-axis direction movement mechanism includes, for example, a ball screw and a motor. When the X1-axis direction movement mechanism is actuated, the holding table 4 moves along the X1-axis direction.

[0029] The holding table 4 is also coupled to a rotary drive source (not shown), such as a motor. When the rotary drive source is actuated, the holding table 4 rotates about a rotation axis, which is a straight line passing through the center of the upper surface of the holding table 4 and extending along the Z1-axis direction.

[0030] Furthermore, the porous plate of the support table 4 is fluidly connected to a suction source (not shown), such as an ejector, via a through-hole formed in the bottom wall of the frame body 4a. When the suction source is actuated, a suction force acts on a space near an upper surface of the porous plate.

[0031] Further, a plurality of clamps (not shown) are provided around the holding table 4 at substantially equal intervals along a circumferential direction of the holding table 4. Each of the plurality of clamps is capable of gripping the annular frame 19 included in the frame unit 11 and holding the annular frame 19 in a position below the upper surface of the holding table 4.

[0032] When the frame unit 11 is loaded into the cutting device 2, the wafer 13 is placed on the holding table 4 with the belt 17 therebetween so that the recessed portion 13e formed on the back surface 13d of the wafer 13 is attached to an upper portion of the holding table 4.

[0033] At this time, the annular frame 19 of the frame unit 11 is gripped by the plurality of clamps and held in a position below the upper surface of the holding table 4. Furthermore, the wafer 13 is held on the holding table 4 via the belt 17 when the suction source fluidly coupled to the porous plate of the holding table 4 is operated in this state.

[0034] A cutting unit 6 is provided above the holding table 4. The cutting unit 6 has a spindle 6a extending along the Y1 axis direction. A cutting blade 6b is attached to a tip end of the spindle 6a.

[0035] A base end of the spindle 6a is coupled to a rotary drive source (not shown), such as a motor. When the rotary drive source is actuated, the cutting blade 6b rotates together with the spindle 6a around a rotation axis, which is a straight line along the Y1-axis direction.

[0036] The cutting unit 6 is connected to a Y1-axis direction movement mechanism (not shown) and a Z1-axis direction movement mechanism (not shown). The Y1-axis direction movement mechanism and the Z1-axis direction movement mechanism each include, for example, a ball screw and a motor. When the Y1-axis direction movement mechanism and / or the Z1-axis direction movement mechanism are actuated, the cutting unit 6 moves along the Y1-axis direction and / or the Z1-axis direction.

[0037] When performing the dicing step (S1) in the cutting device 2, first, the rotary drive source coupled to the holding table 4 rotates the holding table 4 in such a manner that the linear portions (designated dividing lines) present in the boundaries of the plurality of components 15 formed on the wafer 13 become parallel to the X1-axis direction.

[0038] Next, the X1-axis direction moving mechanism adjusts the position of the holding table 4 and / or the Y1-axis direction moving mechanism adjusts the position of the cutting unit 6 so that the intended dividing line parallel to the X1-axis direction is positioned in the X1-axis direction as viewed from the cutting blade 6b in plan view.

[0039] Then, the Z1-axis direction moving mechanism lifts the cutting unit 6 so that a lower end of the cutting blade 6b is positioned lower than a lower side of the recessed portion 13e formed on the back side 13d of the wafer 13, but higher than the upper surface of the holding table 4.

[0040] Next, the rotary drive source coupled to the base end of the spindle 6a rotates the spindle 6a to rotate the cutting blade 6b. Then, the X1-axis direction moving mechanism moves the holding table 4 in a direction opposite to the X1-axis direction, so that the lower end of the cutting blade 6b extends from one end to the other end of the wafer 13 in the X1-axis direction. As a result, the wafer 13 is cut and divided along the designated dividing lines.

[0041] In other words, a groove 11a is formed in the frame unit 11, penetrating the wafer 13 and exposing the tape 17 on a lower surface thereof. The above steps are repeated until the wafer 13 is divided along all boundaries of the plurality of components 15. This completes the dicing step (S1).

[0042] Note that the specific example of the singulation step (S1) is not limited to the details described above. Fig. Figure 3B is a partially cross-sectional side view schematically illustrating another example of the singulation step (S1). Simplified, Fig. 3B shows the manner of singulating a plurality of components 15 using a laser beam with a wavelength absorbable by the wafer 13 in a laser processing device.

[0043] Note that an X2-axis direction and a Y2-axis direction, which are Fig. 3B are directions perpendicular to each other on a horizontal plane, and a Z2-axis direction is a direction (vertical direction) perpendicular to both the X2-axis direction and the Y2-axis direction.

[0044] One in Fig. 3B, the laser processing device 8 has a holding table 10. The holding table 10 has the same structure as the one shown in Fig. 3A. Specifically, the holding table 10 includes a circular plate-shaped frame body 10a and a circular plate-shaped porous plate fixed to a depressed portion formed on one side of an upper surface of the frame body 10a.

[0045] The holding table 10 is connected to an X2-axis direction movement mechanism (not shown) and a Y2-axis direction movement mechanism (not shown). The X2-axis direction movement mechanism and the Y2-axis direction movement mechanism each include, for example, a ball screw and a motor. When the X2-axis direction movement mechanism and / or the Y2-axis direction movement mechanism are actuated, the holding table 10 moves along the X2-axis direction and / or the Y2-axis direction.

[0046] The holding table 10 is also coupled to a rotary drive source (not shown), such as a motor. When the rotary drive source is operated, the holding table 10 rotates about a rotation axis, which is a straight line passing through the center of the upper surface of the holding table 10 and extending along the Z2-axis direction.

[0047] The porous plate of the support table 10 is fluidly connected to a suction source (not shown), such as an ejector, via a through-hole formed in a bottom wall of the frame body 10a. When the suction source is actuated, a suction force acts on a space near an upper surface of the porous plate.

[0048] Around the holding table 10, a plurality of clamps (not shown) are provided at substantially equal intervals along a circumferential direction of the holding table 10. Each of the plurality of clamps is capable of gripping the annular frame 19 included in the frame unit 11 and holding the annular frame 19 in a position below the upper surface of the holding table 10.

[0049] Further, when setting the frame unit 11 into the laser processing apparatus 8, the wafer 13 is placed on the holding table 10 with the tape 17 therebetween so that the recessed portion 13e formed on the back surface 13d of the wafer 13 is fitted to an upper portion of the holding table 10.

[0050] At this time, the annular frame 19 of the frame unit 11 is gripped by the plurality of clamps and held in a position below the upper surface of the holding table 10. Furthermore, the wafer 13 is held on the holding table 10 via the belt 17 when the suction source fluidly coupled to the porous plate of the holding table 10 is actuated in this state.

[0051] A head 12 of a laser beam application unit is provided above the holding table 10. The head 12 houses an optical system such as a condenser lens and a mirror. Furthermore, the head 12 is coupled to a Z2-axis direction movement mechanism (not shown). The Z2-axis direction movement mechanism includes, for example, a ball screw and a motor. When the Z2-axis direction movement mechanism is actuated, the head 12 moves along the Z2-axis direction.

[0052] The laser beam application unit includes a laser oscillator (not shown) that generates a laser beam with a wavelength absorbable by the wafer 13 (for example, 355 nm). The laser oscillator uses, for example, neodymium-doped yttrium aluminum garnet (Nd:YAG) or the like as the laser medium. When a laser beam LB is generated by the laser oscillator, the laser beam LB is applied by the head 12 to the holding table 10 side via the optical system housed in the head 12.

[0053] When performing the dicing step (S1) in the laser processing apparatus 8, first, the rotary drive source coupled to the holding table 10 rotates the holding table 10 in such a manner that the linear portions (designated dividing lines) included in the boundaries of the plurality of components 15 formed on the wafer 13 become parallel to the X2-axis direction.

[0054] Next, the X2-axis direction movement mechanism and / or the Y2-axis direction movement mechanism adjusts the position of the holding table 10 so that the intended dividing line, which is parallel to the X2-axis direction, is positioned in the X2-axis direction as viewed from the center of the head 12 in plan view. Thereafter, the Z2-axis direction movement mechanism raises the head 12 so that a focal point of the laser beam LB to be applied by the head 12 is positioned at a height substantially equal to the height of the front side 13a of the wafer 13.

[0055] Then, while the laser beam LB is applied from the head 12 to the wafer 13, the X2-axis direction movement mechanism moves the holding table 10 in a direction opposite to the X2-axis direction, so that the laser beam LB travels from one end to the other end of the wafer 13 in the X2-axis direction. As a result, laser ablation occurs along the designated dividing lines, and the wafer 13 is divided.

[0056] In other words, a groove 11a is formed in the frame unit 11, penetrating the wafer 13, with the tape 17 exposed on a lower surface thereof. The above steps are repeated until the wafer 13 is divided along all boundaries of the plurality of components 15. This completes the dicing step (S1).

[0057] When the singulation step (S1) is carried out in the manner described above, the annular reinforcement section 14 of the wafer 13 is separated from the chips of the plurality of components 15. Furthermore, in the Fig. 2, the annular reinforcing portion 14 is removed using a rotating cutting blade (removal step: S2) after the singulation step (S1) has been performed.

[0058] Fig. 4A, Fig. 4B and Fig. 4C each represent a partially cross-sectional side view schematically illustrating an example of the removal step (S2). In simpler terms, the Fig. 4A, Fig. 4B and Fig. 4C illustrates the manner in which the annular reinforcing portion 14 is removed by causing an outer peripheral surface of a rotating cutting blade (removal cutting blade) to come into contact with an upper surface of the annular reinforcing portion 14.

[0059] The removal step (S2) is used, for example, in the Fig. 3A. In the cutting device 2, before performing the removing step (S2), a cutting blade (removal cutting blade) 6c is attached to the tip end of the spindle 6a in place of the cutting blade (separation cutting blade) 6b.

[0060] The cutting blade 6c has a larger blade thickness (width along the Y1-axis direction) than the cutting blade 6b. For example, the blade thickness of the cutting blade 6c is slightly larger than the width of the annular reinforcement portion 14 along a radial direction of the wafer 13.

[0061] When performing the removing step (S2) in the cutting device 2, first, the X1-axis direction moving mechanism adjusts the position of the holding table 4 and / or the Y1-axis direction moving mechanism adjusts the position of the cutting unit 6 so that the cutting blade 6c is positioned over one end of the annular reinforcing portion 14 in the Y1-axis direction (see Fig. 4A).

[0062] Next, the rotary drive source coupled to the base end of the spindle 6a rotates the spindle 6a so that the cutting blade 6c rotates. Thereafter, while the cutting blade 6c is kept rotating, the Z1-axis direction moving mechanism lowers the cutting unit 6 until the outer peripheral surface of the cutting blade 6c comes into contact with the tape 17 (see Fig. 4B).

[0063] As a result, the cutting blade 6c cuts into the annular reinforcement portion 14, removing one end of the annular reinforcement portion 14 in the Y1-axis direction. Thereafter, while the cutting blade 6c is kept rotating, the rotary drive source coupled to the holding table 4 rotates the holding table 4 in such a manner that the frame unit 11 performs at least one rotation (see Fig. 4C).

[0064] As a result, the annular reinforcement portion 14 is completely removed. Note that the specific example of the removal step (S2) is not limited to the details described above. For example, in the removal step (S2), the cutting blade 6c could cut into the annular reinforcement portion 14 while the holding table 4 rotates.

[0065] Further, in the removing step (S2), the annular reinforcing portion 14 may be removed by grinding using the rotating cutting blade 6c. Fig. 5A and Fig. 5B are each a partial cross-sectional side view schematically illustrating an example of such a removal step (S2).

[0066] When performing the removing step (S2) as described above, first, the X1-axis direction moving mechanism adjusts the position of the holding table 4 and / or the Y1-axis direction moving mechanism adjusts the position of the cutting unit 6 so that the cutting blade 6c is positioned in the Y1-axis direction as viewed from one end of the annular reinforcing portion 14 in the Y1-axis direction in plan view.

[0067] Next, the Z1-axis direction moving mechanism lifts the cutting unit 6 so that a lower end of the cutting blade 6c is positioned at a height substantially equal to the height of a lower surface of the annular reinforcing portion 14 (see Fig. 5A). Thereafter, the rotary drive source coupled to the base end of the spindle 6a rotates the spindle 6a, and the rotary drive source coupled to the holding table 4 rotates the holding table 4 so that both the cutting blade 6c and the frame unit 11 rotate.

[0068] Then, when both the cutting blade 6c and the frame unit 11 are kept rotating, the Y1-axis direction moving mechanism causes the cutting unit 6 to approach the holding table 4 until one side surface of the cutting blade 6c comes into contact with the tape 17 (see Fig. 5B). As a result, the annular reinforcing portion 14 is ground by the cutting blade 6c and removed as a whole.

[0069] In the Fig.In the chip manufacturing method illustrated in Figure 2, the singulation step (S1) for singulating the plurality of components 15 and manufacturing chips is performed before the removal step (S2) for removing the annular reinforcing portion 14. That is, in this method, the removal step (S2) is performed in a state where the annular reinforcing portion 14 and the chips of the plurality of components 15 are separated. Therefore, this method can prevent damage to the components 15 that might be caused by the force applied to the annular reinforcing portion 14 in the removal step (S2).

[0070] Furthermore, with this method, without performing the step of singulating the device region 13b of the wafer 13 and the annular reinforcement portion 14, the annular reinforcement portion 14 can be removed, and the chips of the plurality of devices 15 can be manufactured. Therefore, this method can improve chip productivity compared to the chip manufacturing method including such a step.

[0071] In addition, structures, methods, and other matters relating to the embodiment may be appropriately changed without departing from the scope of the subject matter of the present invention.

Claims

[1] A chip manufacturing method for manufacturing chips from a wafer (13) having a back surface (13d) to which a central portion of a tape (17) is attached, the outer peripheral portion of which is attached to an annular frame (19), the back surface (13d) having a recessed portion (13e) formed thereon such that a component region (13b) in which a plurality of components (15) are formed is thinned and that an outer peripheral excess portion surrounding the component region (13b) remains as an annular reinforcing portion (14), the method comprising: a singulation step of singulating the plurality of components (15) and producing the chips by processing the wafer (13) along boundaries of the plurality of components (15); and a removing step of removing the annular reinforcing portion (14) using a rotating cutting blade (6c) after the singulating step. [2] A chip manufacturing method according to claim 1, wherein in the singulating step, the plurality of components (15) are singulated using a rotating cutting blade (6b) for singulation or a laser beam (LB) having a wavelength absorbable by the wafer (13).

Images