Patent Application
20250114904
The present invention relates to a polishing apparatus for polishing a workpiece and a polishing method for polishing a workpiece.
A wafer having a plurality of devices such as integrated circuits (ICs) or large-scale integration (LSI) circuits formed on a top surface thereof in such a manner as to be demarcated by a plurality of intersecting planned dividing lines is divided into individual device chips by a dicing apparatus or a laser processing apparatus. The divided device chips are used in electric apparatuses such as mobile telephones or personal computers.
In addition, a laminated wafer in which two or more wafers are laminated to each other to improve functions of the device chips is desired to be finished in such a manner as to have a shape with a desired angle and a desired step at the outer circumference of the wafer in order to form a wiring layer on an upper surface of the wafer.
A polishing apparatus and a polishing method which are configured to position a polishing pad on the upper surface of a wafer processed into a desired shape and finish the upper surface of the wafer (see Japanese Patent Laid-Open No. H11-156711, for example) have conventionally been proposed. In addition, the applicant has proposed a polishing apparatus that polishes a top surface of a wafer with high flatness and high uniformity and allows a polishing shape to be corrected during polishing (see Japanese Patent Laid-Open No. 2003-124164).
However, when polishing processing is performed while the polishing pad is positioned on the upper surface of the wafer processed in such a manner as to have the shape with the desired angle and the desired step at the outer circumference, it is difficult to finish the upper surface of the wafer in a state in which the desired angle and the desired step are maintained. An improvement has therefore been desired.
It is accordingly an object of the present invention to provide a polishing apparatus and a polishing method that can finish the wafer in a state in which the desired angle and the desired step are maintained when polishing processing is performed while the polishing pad is positioned on the wafer processed into a desired shape.
In accordance with an aspect of the present invention, there is provided a polishing apparatus for polishing a workpiece, the polishing apparatus including a chuck table configured to hold the workpiece, a polishing unit including a rotatable polishing pad configured to polish the workpiece held by the chuck table, a moving mechanism configured to move the chuck table to a loading and unloading region for loading and unloading the workpiece onto and from the chuck table and a polishing region for polishing the workpiece by the polishing unit, a raising and lowering mechanism configured to bring the polishing pad into contact with the workpiece held by the chuck table or separate the polishing pad from the workpiece by raising or lowering the polishing unit, and a shaping unit configured to shape the polishing pad. The shaping unit is configured to come into contact with a polishing surface of the polishing pad and shape the polishing surface into a desired shape.
Preferably, the shaping unit is disposed in such a manner as to be adjacent to the chuck table, and is positioned at a desired position of the polishing surface by the moving mechanism.
In accordance with another aspect of the present invention, there is provided a polishing method for polishing a workpiece, the polishing method including a preparing step of preparing a polishing apparatus including a shaping unit, a dimensional data obtaining step of obtaining dimensional data for finishing an upper surface of the workpiece into a desired shape, a shaping step of shaping a polishing surface of a polishing pad by the shaping unit on a basis of the dimensional data obtained in the dimensional data obtaining step, and a polishing step of finishing the upper surface of the workpiece into the desired shape by polishing the workpiece while the polishing surface of the polishing pad is held in contact with the workpiece held by a chuck table.
According to the present invention, it is possible to shape the polishing surface of the polishing pad corresponding to an upper surface of a wafer having an angle and a step at an outer circumference thereof and to polish and finish the upper surface of the wafer in a state in which the desired angle and the desired step are maintained.
The above and other objects, features and advantages of the present invention and the manner of realizing them will become more apparent, and the invention itself will best be understood from a study of the following description and appended claims with reference to the attached drawings showing a preferred embodiment of the invention.
A polishing apparatus and a polishing method according to an embodiment of the present invention will hereinafter be described in detail with reference to the accompanying drawings.
The polishing apparatus 1 includes an apparatus housing 2 which is in a substantially rectangular parallelepipedic shape and which is provided with the configurations described above. The polishing apparatus 1 includes, in the apparatus housing 2, the polishing unit 3 for polishing a wafer W as a workpiece and the holding unit 5 including a chuck table 52 that holds the wafer W and is configured to be rotatable. In addition, the polishing apparatus 1 includes a first cassette 6 for housing the wafer W that has not yet been subjected to the polishing processing, the first cassette 6 being disposed on the near side in the figure, a second cassette 7 for housing the wafer W that has been subjected to the polishing processing, the second cassette 7 being disposed on another side in an X-axis direction in the figure with respect to the first cassette 6, a temporary placement unit 8 for centering the wafer W, the temporary placement unit 8 being disposed in such a manner as to be adjacent in a Y-axis direction in the figure to the first cassette 6, a cleaning unit 9 disposed in such a manner as to be adjacent in the Y-axis direction to the second cassette 7, a first transporting mechanism 10 that unloads the wafer W housed within the first cassette 6 onto the temporary placement unit 8 and transports the wafer W that has been subjected to the polishing processing and cleaned by the cleaning unit 9 to the second cassette 7, a second transporting mechanism 11 that transports the wafer W mounted and centered on the temporary placement unit 8 onto the chuck table 52 of the holding unit 5 positioned in the loading and unloading region, a third transporting mechanism 12 that transports the wafer W that has been subjected to the polishing processing from the chuck table 52 positioned in the loading and unloading region on the near side in the figure to the cleaning unit 9, an operating panel 14, an unillustrated controller, and an unillustrated display unit. The shaping unit 40 is disposed in such a manner as to be adjacent to the holding unit 5, and is disposed on the polishing region side of a cover table 51 on which the chuck table 52 is disposed (details will be described later).
Incidentally, the operating panel 14 is to instruct the unillustrated controller to start or stop the polishing processing, or specify polishing processing conditions. The unillustrated controller is also connected with the unillustrated display unit that displays processing information and the like.
The polishing unit 3 is fitted in such a manner as to be movable in an upward-downward direction along a pair of guide rails 22 and 22 extending in the upward-downward direction on an inner surface of a supporting wall 21 erected on a rear end side of the apparatus housing 2. The polishing unit 3 includes a unit housing 31, a wheel mount 33 disposed at a lower end of a rotary shaft 32 rotatably supported by the unit housing 31, a polishing wheel 34 fitted to the wheel mount 33 and provided with the polishing pad 35A (or the polishing pad 35B) on a lower surface side, an electric motor 36 that is fitted to an upper end of the unit housing 31 and rotates the wheel mount 33, and a moving base 38 that supports the unit housing 31 via a supporting member 37. An unillustrated polishing agent supply unit is connected to an upper end 32a of the rotary shaft 32. A polishing agent L in a liquid state is supplied to the lower surface side of the polishing wheel 34 via the rotary shaft 32. The moving base 38 is provided with guided grooves that are slidably fitted to the guide rails 22 and 22 described above. The polishing unit 3 is thus supported by the moving base 38 in such a manner as to be movable in the upward-downward direction.
The raising and lowering mechanism 39 that raises and lowers the polishing unit 3 along the guide rails 22 and 22 includes a pulse motor 39a, a male screw rod 39b that is disposed in the upward-downward direction in such a manner as to be parallel with the guide rails 22 and 22, is rotatably supported by the supporting wall 21, and is rotationally driven by the pulse motor 39a, and an unillustrated female screw block that is fitted to the moving base 38 and is screwed to the male screw rod 39b. The polishing unit 3 is moved in a Z-axis direction (upward-downward direction) by normal rotation and reverse rotation driving of the male screw rod 39b by the pulse motor 39a.
Either the polishing pad 35A illustrated in
The polishing pad 35B is a felt or a urethane foam formed in a flat plate shape on the lower surface of the polishing wheel 34. Formed on the lower surface side of the polishing pad 35B are radial grooves 35Ba that spread the polishing agent L in a liquid state which is supplied via the rotary shaft 32 and the wheel mount 33, to an entire region of the lower surface side of the polishing pad 35B. In addition, formed at the center of the polishing pad 35B is a polishing agent supply port 35Bb through which the polishing agent L supplied via the rotary shaft 32 of the polishing unit 3 is discharged. The polishing pads 35A and 35B are each affixed to the lower surface side of the polishing wheel 34 by an adhesive or the like. Incidentally, the following description will be made supposing that the polishing pad 35A for performing dry polishing processing is fitted to the lower surface of the polishing wheel 34.
As illustrated in
The moving mechanism 15 includes a pulse motor 15a and a male screw rod 15b that is disposed in parallel with the pair of guide rails 24 described above, has another end portion rotatably supported by a supporting block 25, and is rotationally driven by the pulse motor 15a. The male screw rod 15b is screwed into the lower surface side of the movable plate 53. The moving mechanism 15 can be moved in the Y-axis direction by normal rotation and reverse rotation driving of the male screw rod 15b by the pulse motor 15a, and can be moved between the loading and unloading region for loading and unloading the wafer W onto and from the holding unit 5 on the near side in the Y-axis direction and the polishing region for polishing the wafer W by the polishing unit 3.
As described above, the shaping unit 40 is disposed in such a manner as to be adjacent to the holding unit 5 and integral with the cover table 51. The shaping unit 40 is positioned at a desired position in the Y-axis direction by the moving mechanism 15 described above.
As is understood from
The shaping unit 44 is fastened to the supporting portion 43 by fastening screws 44a. Hence, in a case where a grindstone 45a of the grindstone unit 45 has worn and needs to be replaced as a result of repeated execution of a shaping step to be described later, or in a case where the shaping unit 44 is replaced with a shaping unit 44 having a grindstone unit 45 or a grindstone 45a in a different shape, the fastening screws 44a can be loosened to remove the shaping unit 44 from the supporting portion 43 and thereby replace the shaping unit 44. In addition, the horizontal state and the height of the supporting portion 43 are finely adjusted by rotating adjusting rods 46a (one of which is not visible in the figure) that couple the adjusting mechanisms 46 to the supporting portion 43.
The polishing apparatus 1 according to the present embodiment substantially has the configuration as described above. A polishing method performed by the polishing apparatus 1 described above will be described in the following.
In performing the polishing method according to the present invention, a preparing step of preparing the polishing apparatus 1 described above is performed. The polishing apparatus 1 described above is merely an example of a polishing apparatus configured on the basis of the present invention, and is not limited to the form of the polishing apparatus 1 described above as long as the polishing apparatus 1 includes a holding unit that holds a workpiece, a polishing unit that includes a rotatable polishing pad for polishing the workpiece held by the holding unit, a moving mechanism that moves the holding unit to the loading and unloading region for loading and unloading the workpiece onto and from the holding unit and the polishing region for polishing the workpiece by the polishing unit, a raising and lowering mechanism that brings the polishing pad into contact with the workpiece held by the holding unit or separates the polishing pad from the workpiece by raising or lowering the polishing unit, and a shaping unit that shapes the polishing pad.
A dimensional data obtaining step obtains dimensional data for finishing an upper surface of the workpiece into a desired shape. The wafer W to be subjected to polishing processing by the polishing method according to the present embodiment is a wafer W as illustrated in
A method of forming the inclined surface W1c having a desired angle by annularly removing the outer circumferential edge of the first wafer W1 is not particularly limited to any method. In an unillustrated laser processing apparatus, for example, the condensing point of a laser beam having a wavelength transmissible through the first wafer W1 is positioned and applied at a deep position in an internal part of the outer circumference of the first wafer W1 whose outer circumferential edge has not yet been removed, and the wafer W is rotated. A ring-shaped modified layer is thereby formed. Thereafter, a plurality of modified layers are formed in an inclined manner by gradually moving a position at which the condensing point of the laser beam is positioned to the central side of the first wafer W1 and moving the position upward. When the modified layers are thus formed, cracks that couple the modified layers to each other and incline in an inward direction are formed at the outer circumference of the first wafer W1. An outer circumference side can be removed by application of an external force to the outer circumferential edge side in this state. A method of applying the external force to the outer circumferential edge side is not particularly limited to any method. For example, the external force can be applied to the outer circumferential edge side of the first wafer W1 by grinding the undersurface W1b of the first wafer W1 in an appropriate grinding apparatus, or the external force can be applied to the outer circumferential edge side by jetting high pressure air from the outside of the first wafer W1. The step between the inclined surface W1chaving a desired angle at the outer circumference and the second wafer W2 is thereby formed, as illustrated in
The wafer W having the inclined surface W1c formed on the first wafer W1 as described above is set as a sample, and in order to obtain the dimensional data regarding the first wafer W1 that is laminated to the second wafer W2 and has the inclined surface W1c formed by removal of the periphery thereof, a laser length measuring device 110 is positioned above the chuck table 52 of the holding unit 5 holding the wafer W after the wafer W illustrated in
The laser length measuring device 110 includes a measuring unit 112. The laser length measuring device 110 applies a laser beam LB from the measuring unit 112, receives reflected light, and transmits a waveform indicating the light intensity of the received light to the unillustrated controller. As a result, on the basis of an interference waveform generated according to a phase difference between the laser light LB applied from the measuring unit 112 and the reflected light, a distance to an irradiation position, that is, the height of the irradiation position on the first wafer W1, can be measured precisely. While the height of the irradiation position on the first wafer W1 is measured precisely in this manner, the chuck table 52 is moved in a direction indicated by an arrow R1 in the figure, to perform scanning with the laser light LB from the outer circumferential edge, at which the inclined surface W1c of the first wafer W1 is formed, through the center of the first wafer W1 to the outer circumferential edge on an opposite side. The dimensional data including the height of the first wafer W1 and the inclination angle of the inclined surface W1c is thereby obtained. The obtained dimensional data is stored in an appropriate storage unit of the controller described above. Incidentally, when the dimensions of the first wafer W1 are measured, the chuck table 52 may be rotated by a predetermined angle (for example, 60°) at a time to perform the dimensional measurement at a plurality of positions.
The above-described dimensional data is data used to shape a polishing surface of the polishing pad 35A in a shaping step to be described later, and may be corrected to such dimensional data that data indicating minute projections and depressions at the inclined surface W1c of the first wafer W1 is averaged to represent a smooth inclined surface. In addition, the dimensional data obtaining step is not necessarily limited to obtaining the dimensional data by actually measuring the shape of the processed first wafer W1 as described above, and, for example, includes obtaining, from design information, dimensional data in design which is a target when the inclined surface W1c having the desired angle described above is formed on the first wafer W1.
After the dimensional data obtaining step described above is performed, the wafer W is removed from the chuck table 52, and the moving mechanism 15 that moves the chuck table 52 is actuated to move the chuck table 52 provided with the shaping unit 40 to the polishing region, where the polishing unit 3 is disposed, and position the grindstone 45a of the shaping unit 40 directly below the center (position indicated by alternate long and short dashed lines C) of the polishing pad 35A, as illustrated in
Then, on the basis of the dimensional data obtained by the above-described dimensional data obtaining step, the above-described raising and lowering mechanism 39 is actuated to lower the polishing unit 3 in a direction indicated by an arrow R4 in
After the recessed portion 35Aa is formed as illustrated in
After the polishing surface of the polishing pad 35A of the polishing unit 3, particularly, the inclined surface 35Ab at the outer circumference, is formed into a desired shape as described above by performing the dimensional data obtaining step and the shaping step described above, a polishing step which performs polishing processing on the laminated wafer W housed in the first cassette 6 is performed. The wafer W housed in the first cassette 6 is the laminated wafer in which the first wafer W1 and the second wafer W2 described above are laminated to each other, and the inclined surface W1c is formed at the outer circumference of the first wafer W1, as described with reference to
In performing the polishing step, the first transporting mechanism 10 is actuated to unload the wafer W from the first cassette 6 and transport the wafer W to the temporary placement unit 8, and the wafer W is centered in the temporary placement unit 8. Next, the second transporting mechanism 11 is actuated to transport the wafer W to the chuck table 52 positioned in the loading/unloading position, and mount the wafer W on the chuck table 52 in a state in which the first wafer W1 is oriented upward. The wafer W mounted on the chuck table 52 is positioned in the polishing region by actuating the moving mechanism 15 described above.
After the wafer W is positioned in the polishing region, the rotary shaft 32 of the polishing unit 3 is rotated at a predetermined rotational speed (for example, 500 rpm) in a direction indicated by an arrow R2 in the figure, and the chuck table 52 is rotated at a predetermined rotational speed (for example, 500 rpm) in a direction indicated by an arrow R7 in the figure. Next, the raising and lowering mechanism 39 described above is actuated to lower the polishing unit 3. As illustrated in
While the polishing pad 35A and the chuck table 52 are rotated as described above, the inclined surface W1c of the first wafer W1 is polished over the entire circumference by the inclined surface 35Ab formed on the lower surface side of the polishing pad 35A. After the inclined surface W1c of the first wafer W1 is polished in this manner, polishing processing is performed as required by positioning the undersurface W1b of the first wafer W1 in a flat region of the recessed portion 35Aa of the polishing surface of the polishing pad 35A and polishing the undersurface W1b until a desired surface roughness is obtained. This completes the polishing method according to the present embodiment.
After the polishing step described above is completed, the moving mechanism 15 is actuated to move the holding unit 5 to the loading and unloading region, and the third transporting mechanism 12 is actuated to transport the wafer W to the cleaning unit 9, where the wafer W is cleaned and dried. After the cleaning and the drying are completed, the first transporting mechanism 10 is actuated to unload the wafer W and house the wafer W in a predetermined position of the second cassette 7.
According to the polishing apparatus 1 and the polishing method described above, the polishing surface of the polishing pad can be shaped in such a manner as to correspond to the upper surface of the wafer having an angle and a step at the outer circumference thereof, and the upper surface of the wafer can be polished and finished in a state in which the desired angle and the desired step are maintained.
In the embodiment described above, description has been made of a case where the polishing pad fitted to the lower surface side of the polishing wheel 34 is the polishing pad 35A for performing dry polishing. However, the present invention is not limited to this, and the present invention is applicable also in the case of the polishing pad 35B for performing polishing while supplying the polishing agent L in a liquid state from the upper end 32a of the rotary shaft 32 of the polishing unit 3. By performing a procedure similar to that of the embodiment described above, it is possible to perform the dimensional data obtaining step on the wafer W1 as a workpiece, perform the shaping step on the polishing pad 35B on the basis of the obtained dimensional data and thereby shape the polishing surface, and perform the polishing processing on the first wafer W1 by the polishing surface shaped by performing the shaping step.
The present invention is not limited to the details of the above described preferred embodiment. The scope of the invention is defined by the appended claims and all changes and modifications as fall within the equivalence of the scope of the claims are therefore to be embraced by the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023-173601 | Oct 2023 | JP | national |
