JP2024090681A - Annular protrusion removal device - Google Patents

Abstract

To efficiently separate and remove an annular protrusion from a wafer in a short period of time.
[Solution] The protrusion removal device 1 includes a holding table 10 that holds a work set WS, which is formed by adhering a tape T having an ultraviolet-curing adhesive to the bottom surface of a circular recess W1 on the back surface of a wafer W having a ring-shaped dividing starting point P along the outer periphery of the circular recess W1, an annular protrusion W2, and a ring frame F, and integrating the work set WS with the tape T, via the tape T; a wedge 31 that is inserted horizontally into the boundary between the tape T and the adhered surface of the annular protrusion W2 in the vertical direction; a moving mechanism 33 that moves the wedge 31 in the radial direction of the wafer W; an ultraviolet ray irradiation unit 35 that irradiates ultraviolet ray UV from the tip of the wedge 31; a rotation mechanism 20 that rotates the holding table 10 around the center of the holding table 10 as an axis; and a control unit 40 that moves the wedge 31 horizontally while irradiating ultraviolet ray UV from the ultraviolet ray irradiation unit 35.
[Selected Figure] Figure 6

Description

The present invention relates to an annular protrusion removal device for removing an annular protrusion from a wafer having a circular recess on the back surface and an annular protrusion formed around the recess.

In the manufacturing process of semiconductor devices such as ICs and LSIs used in electronic devices, the back surface of the wafer is ground to thin the wafer to a specified thickness in order to reduce the size and weight of the semiconductor device. In recent years in particular, there has been a demand for thinner semiconductor devices to meet the demand for thinner and more compact electronic devices such as mobile phones and personal computers. However, when the wafer is ground to a thickness of, for example, 50 μm or less, the flexural strength of the wafer decreases, making it more susceptible to breakage and difficult to handle thereafter.

For example, Patent Documents 1 and 2 propose a grinding method that increases the rigidity of the wafer after grinding by grinding only the back side of the area where the devices are formed on the wafer to form a circular recess in the center, and leaving an annular protrusion of the same thickness as before grinding on the outer periphery of this circular recess as a reinforcing part. The annular protrusion formed on the back side of the wafer by such a grinding method can prevent damage to the wafer when it is handled.

On the other hand, when dividing the wafer into individual chips after grinding, the annular convex portion becomes an obstacle to division, so it is necessary to remove the annular convex portion beforehand before division. For this reason, for example, Patent Document 1 proposes a processing method in which the annular convex portion is separated from the wafer by cutting with a cutting blade, and Patent Document 2 proposes a processing method in which the annular convex portion is separated and removed from the wafer by irradiating it with a laser beam.

When cutting off and removing an annular convex portion from a wafer using the processing methods proposed in Patent Documents 1 and 2, tape coated with ultraviolet-curing adhesive is applied to the surface of the wafer on the circular concave side in the center and to a ring frame surrounding the wafer, the wafer and ring frame are integrated into a work set by the tape, and the boundary between the circular concave portion and the annular convex portion of the wafer is cut into a ring shape. At this time, the adhesive on the tape is irradiated with ultraviolet light to harden the adhesive. A wedge is then inserted between the annular convex portion of the wafer and the tape to peel the annular convex portion off the tape and remove it from the wafer.

JP 2021-174896 A JP 2022-059711 A

However, as with conventional methods, the process of irradiating the adhesive on the tape with ultraviolet light and the process of peeling the annular convex portion off the tape are carried out separately, which means that it takes time to separate and remove the annular convex portion from the wafer, making it inefficient.

The present invention was made in consideration of the above problems, and its purpose is to provide an annular protrusion removal device that can efficiently separate and remove an annular protrusion from a wafer in a short time.

In order to achieve the above object, the present invention provides an annular protrusion removal device for removing annular protrusions from a wafer having a device formed on its front surface, a circular recess corresponding to the device on its back surface, and an annular protrusion outside the circular recess, the wafer having a ring-shaped division starting point along the outer periphery of the circular recess, a work set in which a tape having an ultraviolet-curable adhesive is applied to the bottom surface of the circular recess on the back surface of the wafer, the annular protrusion, and a ring frame to integrate the work set, the work set being held via the tape, and a holding table for holding the tape and a ring frame in a vertical direction. The device is characterized by comprising a wedge that can move horizontally from between the outer circumference of the wafer and the inner circumference of the ring frame toward the center of the wafer at the boundary with the surface to be attached of the convex portion, a movement mechanism that moves the wedge in the radial direction of the wafer, an ultraviolet irradiation unit that irradiates ultraviolet light from the tip of the wedge, a rotation mechanism that rotates the holding table and the wedge relatively around the center of the holding table, and a control unit that moves the wedge horizontally while irradiating ultraviolet light from the ultraviolet irradiation unit, and removes the annular convex portion while hardening the glue.

According to the present invention, while the adhesive on the tape is hardened by irradiating ultraviolet light from the ultraviolet irradiation unit, a wedge is inserted between the annular convex portion of the wafer and the tape and the wedge is moved horizontally to peel the annular convex portion off the tape. This allows the adhesive to harden and the annular convex portion to be peeled off from the tape almost simultaneously, resulting in the effect of efficiently cutting off and removing the annular convex portion from the wafer in a short time.

1 is a vertical cross-sectional view of an annular protrusion removal device and a work set according to the present invention; FIG. FIG. 2 is a front view of a hardening and peeling means of the annular protrusion removing apparatus according to the present invention. 4 is a cutaway front view showing a holding step in the annular protrusion removal method using the annular protrusion removal device according to the present invention; FIG. 1 is a cutaway front view showing a wedge placement step in a method for removing an annular protrusion using the annular protrusion removal device according to the present invention; 4 is a cutaway front view showing an ultraviolet ray irradiation step in the annular protrusion removal method using the annular protrusion removal device according to the present invention. FIG. FIG. 7 is an enlarged detailed view of part A in FIG. 6 . 3 is a cutaway front view showing a removing step in an annular protrusion removing method using the annular protrusion removing device according to the present invention; FIG.

The following describes an embodiment of the present invention with reference to the attached drawings.

[Configuration of annular protrusion removal device]
First, the configuration of the annular protrusion removal apparatus according to the present invention will be described with reference to FIG. 1. The annular protrusion removal apparatus 1 is an apparatus for removing an annular protrusion W2 formed as a reinforcing part on the outer periphery of a wafer W before the wafer W is divided, and is equipped with the following components:

That is, the annular protrusion removal device 1 mainly comprises a holding table 10 that holds the work set WS shown in FIG. 2, a rotation mechanism 20 that rotates the holding table 10, a pair of hardening and peeling means 30, and a control unit 40 that controls the operation of the rotation mechanism 20 and each of the hardening and peeling means 30. Below, the configurations of the holding table 10, the rotation mechanism 20, the hardening and peeling means 30, and the control unit 40, which are the main components of the annular protrusion removal device 1 according to the present invention, will be described.

(holding table)
The holding table 10 is a disk-shaped member, and a porous disk-shaped porous member 10A is incorporated in the upper center thereof, and the lower surface of the porous member 10A constitutes the holding surface. The porous member 10A is selectively connected to a suction source (not shown) such as a vacuum pump. Four clamps 11 (only two are shown in FIG. 1) are arranged at equal angular pitches (90° pitches) in the circumferential direction on the outer periphery of the holding table 10 to grip the work set WS set on the holding surface of the holding table 10 and fix it to the holding table 10 as shown in FIG. 4.

As shown in detail in FIG. 2, the surface (top surface in FIG. 2) of the wafer W is divided into many rectangular regions by mutually intersecting dividing lines L1, L2 called streets arranged in a grid pattern, and devices D such as ICs and LSIs are formed in each rectangular region. Then, in the preceding grinding process, the wafer W on which many devices D are formed is ground at the center (the portion corresponding to the device D (see FIG. 2) on the back surface) of the wafer W, forming a circular recess W1 of a predetermined thickness. A ring-shaped protrusion that retains the thickness before grinding is formed radially outward from the circular recess W1 as a reinforcing portion. The outer periphery of the wafer W is chamfered to form a circular arc-shaped curved surface.

As shown in FIG. 2, a circular ring frame F is concentrically arranged on the radial outside of the wafer W, and a tape T coated with an ultraviolet-curable adhesive (not shown) is attached to the circular recess W1 on the back surface of the wafer W and the upper surface of the ring frame F. The tape T integrates the wafer W and the ring frame F to form a work set WS, and the work set WS is held on the lower holding surface of the holding table 10 as described later (see FIG. 4). Here, a ring-shaped division starting point P, such as a cutting groove by cutting or a modified layer by laser irradiation, is formed in a ring shape on the outer periphery of the circular recess W1 of the wafer W (the boundary with the annular protrusion W2). In addition, the wafer W with the circular recess W1 and the annular protrusion W2 formed on the back surface by grinding is cut along the planned division lines L1, L2 (see FIG. 2) by cutting after the annular protrusion W2 is removed by the annular protrusion removal device 1.

(Rotation mechanism)
The rotation mechanism 20 is a mechanism for rotating the holding table 10 relative to the pair of hardening/peeling means 30, and in this embodiment is configured by a servo motor that rotates the holding table 10 in a horizontal plane at a predetermined speed around the central axis CL of the holding table 10.

(Hardening and peeling means)
The pair of hardening/peeling means 30 are intended to peel off the annular convex portion W2 of the wafer W from the tape T while hardening the adhesive applied to the tape T, and are disposed so as to face each other in the radial direction (at a circumferential pitch of 180°) below the annular portion between the work set WS and the wafer W. Here, the configuration of the pair of hardening/peeling means 30 is the same, and therefore the configuration of one of the hardening/peeling means 30 will be described below with reference to FIG.

The hardening and peeling means 30 is composed of an inverted truncated cone wedge 31, a two-stage cylindrical support 32 extending vertically downward from the center of the wedge 31, a moving mechanism 33 that horizontally supports the wedge 31 via the support 32 and moves the wedge 31 horizontally in the radial direction of the wafer W, a lifting mechanism 34 that raises and lowers the wedge 31 vertically, and an ultraviolet ray irradiation unit 35 that irradiates ultraviolet rays horizontally from the outer peripheral edge of the wedge 31. Here, the support 32 supports the wedge 31 so that it can rotate freely around its center.

The wedge 31 is made of a transparent glass plate in the shape of an inverted truncated cone that transmits light, and its outer periphery has a sharp knife-edge shape. The upper surface of the wedge 31 forms a flat tapered surface that slopes downward at a small angle α toward the outside in the radial direction of the wafer W (to the right in Figure 3). A reflective film (not shown) is applied to the outer surface of the wedge 31, except for the knife-edge outer periphery, and a triangular prism-shaped reflective member 36, which is an optical member that reflects light, is housed in the upper center of the interior of the wedge 31.

The moving mechanism 33 is a mechanism for moving the wedge 31 together with the support 32 in the horizontal direction (the radial direction of the wafer W), and the lifting mechanism 34 is a mechanism for vertically lifting and lowering the wedge 31 together with the support 32, and these operations are controlled by the control unit 40.

The ultraviolet irradiation section 35 irradiates ultraviolet rays UV from the outer periphery of the wedge 31 radially outward, and is composed of a light source 351 built into the support 32, an optical path 352 formed vertically from the light source 351 to the wedge 31 at the axial center of the support 32, and the outer periphery of the wedge 31 which irradiates ultraviolet rays UV horizontally.

(Control Unit)
The control unit 40 includes a CPU (Central Processing Unit) that performs calculations according to a control program, and storage units such as a ROM (Read Only Memory) and a RAM (Random Access Memory). The control unit 40 is electrically connected to the rotation mechanism 20, the movement mechanism 33 of the curing/peeling means 30, the lifting mechanism 34, the light source 351 of the ultraviolet ray irradiation unit 35, and the like, and controls the operations of these devices.

[Method for removing annular protrusion]
Next, a method for removing the annular convex portion W2 from the wafer W using the annular convex portion removing apparatus 1 configured as above will be described below with reference to FIGS.

The method for removing the annular convex portion W2 using the annular convex portion removal device 1 according to the present invention is a method for removing the annular convex portion W2 from the wafer W through the following steps in sequence: 1) a holding step, 2) a wedge placement step, 3) an ultraviolet light irradiation step, and 4) a removal step. Each step will be described below in turn.

1) Holding step:
As shown in Fig. 4, the holding step is a step of holding the work set WS on the holding surface of the lower surface of the holding table 10, and in this holding step, the wafer W of the work set WS is pressed from below against the holding surface of the holding table 10 via the tape T, and the ring frame F is gripped and fixed by four clamps 11 (only two are shown in Fig. 4). Then, the porous member 10A of the holding table 10 is connected to a suction source (not shown) and the porous member 10A is sucked, generating a negative pressure in the porous member 10A, and the wafer W is sucked and held on the holding surface of the holding table 10 via the tape T by being attracted by this negative pressure. At this time, the pair of hardening and peeling means 30 are disposed below the ring-shaped portion between the outer periphery of the wafer W of the tape T and the inner periphery of the ring frame F.

2) Wedge placement process:
5, the wedge placement step is a step of driving the lifting mechanisms 34 of each pair of curing/peeling means 30 to lift each wedge 31 together with the moving mechanisms 33 and ultraviolet ray irradiation units 35, and bringing the outer periphery of the upper surface of the wedge 31 (the upper surface facing the wafer W) into contact with the tape T. At this time, the control unit 40 activates the rotation mechanism 20 to rotate the turntable 10 around its central axis CL at a predetermined speed within the horizontal plane.

3) Ultraviolet irradiation step:
In the ultraviolet irradiation process, as shown in FIG. 6, ultraviolet rays UV emitted from the light sources 351 of each of a pair of ultraviolet irradiation units 25 are irradiated radially outward from the outer peripheral edge of the wedge 31, and the moving mechanism 33 is activated to move the wedge 31 together with the ultraviolet irradiation unit 35 horizontally in the direction of the arrow shown toward the center of the wafer W.

That is, the ultraviolet rays UV emitted vertically upward from the light source 351 of the ultraviolet irradiation unit 35 enter the inside of the wedge 31 through the optical path 352 formed in the support 32. The ultraviolet rays UV that enter the wedge 31 are first reflected by the reflecting member 36, and then repeatedly reflected by a reflective film (not shown) that is applied to the outer periphery of the wedge 31, and as shown in detail in FIG. 7, a portion of the ultraviolet rays UV that are emitted horizontally from the outer periphery of the wedge 31 toward the outside. Then, a portion of the ultraviolet rays UV that are emitted horizontally from the outer periphery of the wedge 31 is irradiated toward the adhesive portion between the annular protrusion W2 of the wafer W and the tape T, hardening the ultraviolet-curable glue applied to that portion of the tape T.

As described above, the adhesive of the tape T to which the annular convex portion W2 of the wafer W is adhered hardens by irradiation with ultraviolet rays UV, and at the same time, the movement mechanism 33 moves each wedge 31 horizontally together with the ultraviolet irradiation unit 35 toward the center of the wafer W so that they approach each other. Then, as shown in detail in FIG. 7, the knife-edge-shaped outer edge of each wedge 31 (only one is shown in FIG. 7) is inserted vertically into the boundary between the tape T and the adhered surface of the annular convex portion W2 of the wafer W. Note that even during this ultraviolet irradiation process, the holding table 10 and the work set WS (wafer W) rotate horizontally at a predetermined speed around their central axis CL.

As described above, in the ultraviolet irradiation process, the ultraviolet rays UV emitted from the light source 351 of the ultraviolet irradiation unit 35 are irradiated from the outer periphery of each wedge 31 toward the glue of the tape T adhered to the annular convex portion W2 of the wafer W, hardening the glue, and at the same time, the outer periphery of each wedge 31 is inserted vertically into the boundary between the tape T and the adhered surface of the annular convex portion W2 of the wafer W.

4) Removal step:
8, while the holding table 10 and the wafer W held thereon are rotated by the rotating mechanism 20, the moving mechanism 33 horizontally moves each of the wedges 31 in a direction approaching each other toward the center of the wafer W. That is, while the glue of the portion bonding the annular convex portion W2 of the tape T is hardened by ultraviolet light UV irradiated from the outer periphery of each wedge 31, the knife-edge-shaped outer periphery of each wedge 31 is inserted into the boundary between the annular convex portion W2 of the wafer W and the portion of the tape T bonded to the annular convex portion W2, the rotatable wedges 31 move horizontally in a direction approaching each other toward the center of the wafer W, whereby the outer periphery of each wedge 31 functions as a scraper to push open the gap in the bonding portion between the tape T and the annular convex portion W2. Then, the annular convex portion W2 of the wafer W becomes easily peeled off from the adhesive of the tape T that has hardened due to irradiation with ultraviolet rays UV, and the annular convex portion W2 is separated from the division starting point P such as a cutting groove and falls under its own weight.

In this embodiment, a pair of hardening/peeling means 30 are disposed at positions facing each other in the radial direction of the wafer W, so that the annular protrusion W2 is stably separated from the wafer W in a well-balanced manner in the circumferential direction. As described above, the upper surface of each wedge 31 forms a tapered surface that is inclined obliquely downward at a small angle α (see FIG. 3) toward the outside in the radial direction of the wafer W, so that the outer peripheral edge of each wedge 31 effectively widens the gap in the adhesive portion between the tape T and the annular protrusion W2, and each wedge 31 can fully function as a scraper.

As described above, when the annular convex portion W2 is cut off and removed from the wafer W in the removal process, only the thin wafer W (circular concave portion W1) from which the annular convex portion W2 has been removed, the ring frame F, and the tape T remain in the work set WS. Then, the wafer W (circular concave portion W1) is divided along the division starting points P such as division grooves by the tape T being pulled radially outward and expanded, to obtain multiple device chips on which individual devices D (see Figure 1) are mounted.

As described above, according to the method for removing the annular convex portion W2 performed using the annular convex portion removal device 1 of this embodiment, while the adhesive of the tape T is hardened by irradiating ultraviolet rays UV from the ultraviolet irradiation unit 35, the wedge 31 is inserted between the annular convex portion W2 of the wafer W and the tape T, and the wedge 31 is moved horizontally to peel the annular convex portion W2 from the tape T. This allows the adhesive to be hardened and the annular convex portion W2 to be peeled off from the tape T almost simultaneously, and the annular convex portion W2 can be efficiently separated and removed from the wafer W in a short time.

The present invention is not limited to the above-described embodiment, and various modifications are possible within the scope of the claims and the technical ideas described in the specification and drawings.

1: annular protrusion removal device, 10: holding table, 10A: porous member,
11: clamp, 20: rotation mechanism, 30: hardening and peeling means, 31: wedge,
32: Support, 33: Moving mechanism, 34: Lifting mechanism, 35: Ultraviolet ray irradiation unit, 351: Light source, 352: Light path, 36: Reflecting member, 40: Control unit, CL: Central axis of holding table,
D: device, F: ring frame, L1, L2: planned division lines, P: division starting point,
T: tape, UV: ultraviolet light, WS: work set, W: wafer, W1: circular recess,
W2: annular convex portion, α: inclination angle of the upper surface of the wedge

Claims (2)

1. An annular protrusion removal apparatus for removing an annular protrusion from a wafer having a device formed on a front surface thereof, a circular recess corresponding to the device on a rear surface thereof, and an annular protrusion outside the circular recess, the apparatus comprising:
the wafer has a ring-shaped division starting point along an outer periphery of the circular recess,
a holding table that holds a work set, which is formed by attaching a tape having an ultraviolet-curable adhesive to a bottom surface of the circular recess on the rear surface of the wafer, the annular protrusion, and a ring frame, and which is integrated with the bottom surface of the circular recess, the annular protrusion, and the ring frame, via the tape;
a wedge movable in a vertical direction at a boundary between the tape and the surface of the annular protrusion, the wedge being movable in a horizontal direction from between the outer periphery of the wafer and the inner periphery of the ring frame toward the center of the wafer;
a moving mechanism for moving the wedge in a radial direction of the wafer;
an ultraviolet ray irradiation unit that irradiates ultraviolet rays from a tip of the wedge;
a rotation mechanism for relatively rotating the holding table and the wedge around an axis of the center of the holding table;
a control unit that moves the wedge in a horizontal direction while irradiating ultraviolet light from the ultraviolet light irradiation unit;
Equipped with
An annular protrusion removal device that removes the annular protrusion while hardening the glue. The ultraviolet irradiation unit is composed of a light source that emits ultraviolet light, an optical path that guides the ultraviolet light to the wedge, and an outer periphery of the wedge,
The wedge is a disk-shaped glass plate having a reflective film on its outer surface other than the outer periphery;
2. The apparatus for removing an annular protrusion according to claim 1, wherein ultraviolet light emitted from said light source is reflected inside said wedge by said reflective film and is irradiated from said outer periphery.

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