Workpiece Processing Preparation Method and Processing Method

The present invention relates to a processing method for a sheet-shaped object, and particularly relates to a processing method of grinding and thinning the sheet-shaped object to a predetermined thickness.

When, as a workpiece, a sheet-shaped object, such as a semiconductor wafer, is to be subjected to thinning processing, as thinning proceeds, a rigidity of the workpiece significantly decreases, and consequently a crack, warping, or the like occurs therein during transportation or the processing. To prevent this problem, a process is known in which the workpiece is laminated on a rigid supporting substrate (support substrate) and then ground (see, e.g., JP 2004-207606 A).

As the thinning proceeds, an R-shape of an edge portion of the workpiece tends to have a knife-edge shape, and accordingly edge chipping is likely to occur. To prevent this problem, a process (edge trimming) is known in which, before the workpiece is laminated on the supporting substrate, a circumferential groove is formed by cutting of an outer peripheral portion of the workpiece with a cutting blade or the like (see, e.g., JP 2000-173961 A).

In each of the processing methods described above, the workpiece is fixed to a top surface of the supporting substrate via a liquid resin serving as a fixing material and ground to a predetermined thickness. However, when the edge-trimmed workpiece is ground from a surface, which is not unformed with the circumferential groove, and thinned, a problem arises in that the outer peripheral portion of the workpiece is broken to be scattered as scraps (edge chipping). This results in another problem that the scraps scattered in a device adhere to the inside of the device due to grinding water supplied during processing, and therefore it is difficult to remove the scraps.

To address these problems, a mechanism (see, e.g., JP 2023-180023 A) for collecting the scraps and a method (JP 2022-051112 A) of adding an ultrasonic unit to thereby perform grinding while cracking the scraps, are also known, but it is not possible to prevent occurrence of the scraps, which is a root cause of the problem, in addition to a problem of a complicated device configuration.

In view of the foregoing problems, the present invention proposes a novel technology for a processing method of thinning a sheet-shaped workpiece having an outer peripheral groove formed in an outer peripheral edge portion of a surface thereof.

The foregoing is the problems to be solved by the present invention, and a means for solving the problems will be described next.

In accordance with an aspect of the present invention, there is provided a workpiece processing preparation method including: an adhesive material laying step of laying an adhesive material on a top surface of a supporting substrate; a facing step of causing a sheet-shaped workpiece having an outer peripheral groove formed in an outer peripheral edge portion of a top surface thereof to face the adhesive material; a pressing step of pressing the adhesive material with the top surface of the workpiece to press-spread the adhesive material between the workpiece and the supporting substrate, and fill the outer peripheral groove with the adhesive material; and a laminated body forming step of hardening the adhesive material with an external stimulus to form a laminated body.

In accordance with another aspect of the present invention, the workpiece processing preparation method further includes: trimming step of removing, to form the outer peripheral groove in the outer peripheral edge portion of the top surface of the workpiece, a portion of an edge of the outer peripheral edge portion of the workpiece to form the outer peripheral groove.

In accordance with still another aspect of the present invention, the adhesive material contains an abrasive grain.

In accordance with yet another aspect of the present invention, a processing method includes: an adhesive material laying step of laying an adhesive material on a top surface of a supporting substrate; a facing step of causing a sheet-shaped workpiece having an outer peripheral groove formed in an outer peripheral edge portion of a top surface thereof to face the adhesive material; a pressing step of pressing the adhesive material with the top surface of the workpiece to press-spread the adhesive material between the workpiece and the supporting substrate, and fill the outer peripheral groove with the adhesive material; a laminated body forming step of hardening the adhesive material with an external stimulus to form a laminated body; a holding step of holding the supporting substrate side of the laminated body on a holding table to expose a back surface of the workpiece; and a grinding step of grinding the back surface of the workpiece with a grinding stone to thin the workpiece to a predetermined thickness.

In accordance with still another aspect of the present invention, in the grinding step, the workpiece is thinned until the adhesive material is ground.

The present invention achieves the following effects. In other words, in accordance with the aspect of the present invention, by filling the outer peripheral groove with the adhesive material and thereby eliminating a gap, it is possible to reinforce the outer peripheral edge portion in such a manner that the adhesive material supports the outer peripheral edge portion. This can prevent a situation in which the outer peripheral edge portion is scattered as large scraps.

Additionally, in accordance with the aspect of the present invention, by grinding a surface of the adhesive material exposed after the thinning of the workpiece, even when the grinding stone is susceptible to dulling, it is possible to perform dressing (setting) of the grinding stone with the abrasive grain contained in the adhesive material.

Referring to the drawings, a description will be given hereinbelow of an embodiment of the present invention.

is a diagram illustrating an overview of a configuration of a press-shaping device to be used for workpiece processing preparation. In, in a press-shaping device, a wafer W as a workpiece is caused to face an adhesive material (resin) laid on an upper surface of a supporting substrate.

The press-shaping deviceis configured to have a table, a holding means(holding pad), a lifting means, an ultraviolet light applying means, a resin supply means, and a control devicefor controlling various operation units.

A tableis configured to have a horizontal upper surfaceand transmit ultraviolet light, and is formed of a transparent member made of, e.g., glass or the like. In the horizontal upper surface, a suction groove is formed to lead to a suction source not shown and, by generating a negative pressure on the upper surface, the upper surfaceis configured as a suction-holding surface.

The holding meansis disposed above the horizontal upper surfaceof the table, while a suction groove is formed in a horizontal lower surfacethereof to lead to a suction source not shown and, by generating a negative pressure on the lower surface, the lower surfaceis configured as the suction-holding surface. By the lower surface, a back surface (upper surface) of the wafer W as the workpiece is suction-held to expose a top surface (lower surface) thereof.

The holding meansis fixed to a lower surface of a lifting baseof the lifting meansto rise and fall with the lifting base. The lifting meanshas an actuator not shown and operates the actuator to raise and lower the lifting base.

The ultraviolet light applying meanshas a light sourcedisposed below the tableto emit ultraviolet light. Specifically, as will be described later, the ultraviolet light penetrates the tableand the supporting substrateto harden the resin.

The resin supply meanshas a supply nozzlefor supplying the liquid resinto an upper surface of the supporting substrateor the like laid on the table. The supply nozzleis configured to be movable by the actuator not shown, and is located at a supply position that locates the supply nozzleat a center position of the tableand at a retracted position away from the table. The supply nozzleis connected to a resin supply source not shown to be able to supply a predetermined amount of the resinto the upper surface of the supporting substrateor the like.

As illustrated in, the wafer W as the workpiece has a disc shape and a chamfered portion Wm formed at an edge portion thereof serving as an outer peripheral edge portion Wg. A top surface Wa of the wafer W is configured as a device surface where, in each of regions defined by, e.g., division lines perpendicular to each other, a device is to be formed.

When a back surface Wb of the wafer W is thinned, an R-shape of the chamfered portion Wm of the edge portion becomes a knife-edge shape, and consequently edge chipping is likely to occur. Accordingly, as illustrated in, by, e.g., a processing deviceincluding a cutting blade, edge trimming for trimming a portion of an outer peripheral edge of the top surface Wa of the wafer W is performed to form an outer peripheral groove G in the outer peripheral edge portion of the top surface Wa.

Specifically, the back surface Wb of the wafer W is suction-held by a holding table, while the outer peripheral edge portion Wg of the top surface Wa of the wafer W is cut with the cutting blade, and the holding tableis rotated by 360 degrees to form the circumferentially continuous stepped outer peripheral groove G.

The edge trimming of the workpiece described above can be incorporated as a trimming step into preliminary preparation for the workpiece processing preparation method according to the present invention.

Note that the outer peripheral groove G illustrated inis not particularly limited except that the outer peripheral groove G is formed by the edge trimming method using the cutting blade, and may also be formed by, e.g., laser abrasion processing or the like.

In addition, the wafer W as the workpiece may be not only a silicon wafer, but also, e.g., a plate made of a glass material or a composite wafer obtained by combining a plurality of wafers and the like together. The workpiece may have not only a disc shape, but also a rectangular shape.

Next, a description will be given of a processing preparation method including each of steps of a flow chart shown in.

As illustrated in, an adhesive material laying step is a step of laying the resinas the adhesive material on the surface of the supporting substrate.

Specifically, on the horizontal upper surfaceof the table, the sheet-shaped supporting substrateis placed. The supporting substrateis made of a transparent member made of, e.g., glass or the like and laminated on the wafer W so as to prevent cracking, warping, or the like of the wafer W, which will be extremely thinned later. The supporting substratemay have not only a disc shape, but also a rectangular shape.

Then, above a substantially center portion of the supporting substrate, the supply nozzleis located, and the resinis dropped from the supply nozzleso that a predetermined amount of the resinis supplied to the upper surface. For example, the resinis an ultraviolet-curing resin and, e.g., “Resilock” (registered trademark) manufactured by DISCO Corporation is used.

The adhesive material may be the resinalone, but preferably contains abrasive grains having an average gain size of, e.g., not less than 0.1 μm and not more than 20 μm. By causing the resinto contain the abrasive grains, it is possible to grind the resinwith grinding stones and thereby achieve an effect of setting by so-called dressing, as will be described later in detail.

Note that the abrasive grains are, e.g., fused white alundum (WA), green carbon (GC), or the like, but is not particularly limited. The average grain size is defined as, e.g., a grain size when an accumulated height is 50% in a precipitation test method (i.e., a median size or 50% size). Note that the average grain size may also be defined as a most frequent grain size in an electrical resistance test method (i.e., a most frequent grain size or mode size).

As illustrated in, a facing step causes the wafer W as the sheet-shaped workpiece having the outer peripheral groove G formed in the outer peripheral edge portion of the top surface Wa to face the resinas the adhesive material.

Specifically, the wafer W is brought into a state where the back surface Wb is suction-held by the holding meanssuch that the top surface Wa of the wafer W is exposed to face downward.

As illustrated in, the resinas the adhesive material is pressed with the top surface Wa of the wafer W as the workpiece so that the resinis press-spread between the wafer W and the supporting substrateand fills the outer peripheral groove G.

Specifically, first, the supply nozzleis retracted so as to move away from the position below the holding means. Then, the back surface Wb of the wafer W is suction-held by the lower surfaceof the holding means, while the wafer W is lowered to a predetermined height by the lifting means(see). When the top surface Wa of the wafer W reaches the resin, the resinis spread with no gap between the wafer W and the table.

The supporting substratehaving an area larger than that of the top surface Wa of the wafer W is used. Thus, as illustrated in an enlarged portion of, it is possible to cause the resinto flow around and enter the outer peripheral groove G and fill the outer peripheral groove G.

It is to be noted herein that, to reliably fill the outer peripheral groove G with the resin, in the adhesive material laying step, the resinis supplied in a sufficient amount. For example, as illustrated in, the resinmay also be supplied in such a large amount as to fill a space of the outer peripheral groove G and thereby prevent a gap from being formed between the outer peripheral edge portion Wg and the supporting substrate, while flowing out of the space of the outer peripheral groove G. Note that the resinis not necessarily required to fill the outer peripheral groove G entirely (100%) but may fill only 30% or more of the outer peripheral groove G.

As illustrated in, a laminated body forming step is a step of hardening the resinas the adhesive material with an external stimulus to form a laminated bodyillustrated in.

Specifically, a height of the wafer W is maintained at a predetermined height so as to maintain a state where the outer peripheral groove G is filled with the resinby the pressing step, while ultraviolet light UV is applied from below by the ultraviolet light applying means() to the resinvia the tableand the supporting substrateto harden the resin. At this time, the resinfilling the outer peripheral groove G is also hardened.

In the present embodiment, a means for the external stimulus for hardening the resinis the application of the ultraviolet light. Another example of the external stimulus is heat and, in this case, it can be considered to use a thermosetting resin as the resin. As a result of the hardening of the resin, a device D () formed on the top surface Wa of the wafer W is protected by the resin.

After the hardening of the resin, the wafer W held by the holding means() is released therefrom to form the laminated body(laminated wafer (composite wafer)) in which the wafer W, the supporting substrate, and the resinare integrated, as illustrated in.

Next, a description will be given of a method of performing thinning processing on the laminated bodyformed as described above.

As illustrated in, a holding step is a step of holding the supporting substrateof the laminated bodyon a holding tableto expose the back surface Wb of the wafer W as the workpiece.

Specifically, as illustrated in, the supporting substrateof the laminated bodyis suction-held on a holding surfaceof the holding tableof a grinding deviceto expose the back surface Wb of the wafer W. The holding tableis controlled to be rotated by a motor not shown.

As illustrated in, the grinding deviceincludes a spindlecontrolled to be rotated by the motor not shown and a grinding wheelto be fixed to a leading end of the spindle. On the grinding wheel, a plurality of grinding stonesare arranged in a circumferential direction.

As illustrated in, a grinding step is a step of grinding the back surface Wb of the wafer W as the workpiece with the grinding stonesto thin the wafer W to a predetermined thickness.

Specifically, by rotating the holding tableand simultaneously feeding the grinding wheeldownward with a lifting mechanism not shown, while rotating the grinding wheel, grinding is performed in such a manner as to press the grinding stonesagainst the back surface Wb of the wafer W.