JP2013004726A - Processing method of plate-like object - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a processing method of a plate-like object capable of further flattering a plate-like object.SOLUTION: A processing method of a plate-like object comprises: a grinding step of abutting a grinding wheel on a plate-like object 11 and grinding the plate-like object 11 to a prescribed thickness; a polishing step of polishing the plate-like object 11 with an abrasive pad having a diameter larger than a diameter of the plate-like object 11 by rotating the abrasive pad and a chuck table 50 respectively in the state in which the plate-like object 11 held by the chuck table 50 is covered by the abrasive pad and removing a grinding distortion which occurred in the grinding step after performing the grinding step; a plate-like object cross-sectional shape detection step of measuring a thickness of the polished plate-like object 11 at a plurality of points in a radial direction and detecting whether the cross-sectional shape of the plate-like object 11 is concave or convex after performing the polishing step; and a holding surface inclination adjustment step of adjusting inclination of a holding surface of the chuck table 50 so that the polished plate-like object 11 is flattered by slightly inclining the holding surface on the basis of the cross-sectional shape of the plate-like object 11 detected by the plate-like object cross-sectional shape detection step.

Description

  The present invention relates to a processing method for a plate-like object in which grinding and polishing are continuously performed on a plurality of plate-like objects.

  A semiconductor wafer in which a large number of semiconductor devices such as IC and LSI are formed on the surface and each semiconductor device is partitioned by a division line (street), or an optical device wafer in which a large number of optical devices are formed on the surface. After the back surface is ground and processed to a predetermined thickness by a grinding device, it is processed along a planned division line by a dicing device or a laser processing device and divided into individual devices. The divided devices are mobile phones, personal computers, etc. Widely used in electrical equipment.

  A grinding apparatus for grinding the back surface of a wafer comprises a rotatable chuck table having a holding surface for holding a wafer, a grinding means for rotatably mounting a grinding wheel for grinding a wafer held on the chuck table, and a grinding means. It comprises at least grinding feed means for approaching and moving away from the holding surface of the chuck table in the vertical direction, and the wafer can be ground to a predetermined thickness.

  When the back surface of the wafer is ground by the grinding device, grinding marks remain on the back surface and fine cracks are formed, and there is a problem that the bending strength of the device diced by the dicing device is lowered.

  Therefore, for example, by polishing the back surface of the wafer using a polishing apparatus as disclosed in JP-A-8-99265, the grinding marks and fine cracks are removed to improve the bending strength of the device. Has been done. Japanese Patent Laid-Open No. 2005-153090 discloses a processing apparatus that can continuously perform grinding and polishing with a single apparatus.

  This processing apparatus includes a grinding unit that grinds a wafer to a predetermined thickness, and a polishing unit that removes grinding distortion generated in the wafer by grinding. A plurality of wafers are accommodated in a cassette and loaded into a processing apparatus, and the plurality of wafers are continuously ground and polished.

JP-A-8-99265 JP 2005-153090 A

  By the way, a slight thickness variation of, for example, about 1.5 μm occurs in the ground and polished wafer. Recent devices tend to become thinner and thinner, and semiconductor wafers that have been ground and polished have become as thin as about 50 μm, and slight variations in thickness are undesirable. Usually, a ground and polished wafer tends to have a so-called middle convex shape in which the central portion is thicker than the outer peripheral portion or a so-called concave shape in which the central portion is thinner than the outer peripheral portion.

  The present invention has been made in view of these points, and an object of the present invention is to provide a processing method for a plate-like material that enables further flattening of the plate-like material such as a wafer. .

  According to the present invention, there is provided a processing method for a plate-like material in which a plurality of plate-like materials are continuously ground, polished, and flattened, and the plate-like shape is formed by a rotatable chuck table having a holding surface for holding the plate-like material. A plate-shaped object holding step for holding an object, and a plate held by the chuck table while rotating the chuck table and rotating a grinding wheel mounted with a grinding wheel after holding the plate-shaped object by the chuck table A grinding step of abutting the grinding wheel against the object to grind the plate to a predetermined thickness; and after performing the grinding step, the chuck with a polishing pad having a diameter larger than the diameter of the object to be polished While the plate-like object held by the table is covered, the polishing pad and the chuck table are rotated to polish the plate-like object with the polishing pad, and the polishing produced on the plate-like object in the grinding step is performed. A polishing step for removing strain, and a plate shape for detecting whether the cross-sectional shape of the plate-like material is concave or convex by measuring the thickness of the polished plate-like material in a radial direction after performing the polishing step Based on the object cross-sectional shape detection step and the cross-sectional shape of the plate-like object detected in the plate-like object cross-sectional shape detection step, the holding surface of the chuck table is slightly inclined to flatten the polished plate-like object. There is provided a processing method of a plate-like object characterized by comprising a holding surface inclination adjusting step for adjusting as described above.

  According to the plate processing method of the present invention, the thickness of the plate after grinding and polishing is measured at a plurality of points in the radial direction to detect the cross-sectional shape of the plate, and based on the cross-sectional shape of the plate Since the inclination of the chuck table is adjusted before grinding the next plate-like object, the plate-like object can be further flattened.

It is a perspective view of the processing apparatus suitable for implementing the processing method of this invention. It is a back side perspective view of a polish unit. It is a bottom side perspective view of a polishing pad. It is a longitudinal cross-sectional view of a chuck table. It is a partial cross section side view which shows the relationship of the standard state of the holding surface of a chuck table, and a grinding wheel. It is a schematic diagram which shows the support method of a chuck table, and the grinding area | region at the time of grinding. It is a partial cross section side view which shows the support structure of a chuck table. It is a surface side perspective view of a semiconductor wafer. It is a back surface side perspective view of a semiconductor wafer in the state where a protective tape was stuck on the surface. It is a partial cross section side view explaining a holding step. It is a partial cross section side view explaining a rough grinding step. It is a partial cross section side view explaining a finish grinding step. It is a longitudinal cross-sectional view explaining a grinding | polishing step. It is a top view explaining a wafer section shape detection step. FIG. 15A is a longitudinal cross-sectional view of a concave wafer after grinding and polishing, and FIG. 15B is a graph showing the cross-sectional shape of the wafer shown in FIG. It is a longitudinal cross-sectional view of a wafer having a convex shape. It is a partial cross section side view explaining a holding surface inclination adjustment step.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Referring to FIG. 1, there is shown a perspective view of a processing apparatus 2 suitable for carrying out the processing method of the present invention. The processing device 2 includes a device housing 4 having a substantially rectangular parallelepiped shape. A column 6 is erected on the upper right end of the device housing 4.

  Two pairs of guide rails 8 and 10 extending in the vertical direction are provided on the inner peripheral surface of the column 6. A rough grinding unit 12 is mounted on one guide rail 8 so as to be movable in the vertical direction (Z-axis direction) by a rough grinding unit feed mechanism 14, and a finish grinding unit 16 is a finish grinding unit on the other guide rail 10. The feed mechanism 18 is mounted so as to be movable in the vertical direction.

  As shown in FIG. 5, the rough grinding unit 12 includes a unit housing 20, a spindle 22 rotatably accommodated in the unit housing 20, a wheel mount 24 fixed to the tip of the spindle 22, and a wheel mount 24. A rough grinding wheel 26 detachably attached to the tip of the motor and a motor 32 for rotationally driving the spindle 22 are included. The rough grinding wheel 26 includes a wheel base 28 and a plurality of rough grinding wheels 30 that are annularly fixed to the outer periphery of the lower end surface of the wheel base 28.

  The finish grinding unit 16 includes a unit housing 34, a spindle 36 rotatably accommodated in the unit housing 34, a wheel mount 38 fixed to the tip of the spindle 36, and a wheel mount 38, as shown in FIG. A finish grinding wheel 40 that is detachably mounted and a motor 46 that rotationally drives the spindle 36 are included. The finish grinding wheel 40 includes an annular base 42 and a plurality of finish grinding wheels 44 that are annularly attached to the outer periphery of the lower end surface of the annular base 42.

  The processing device 2 includes a turntable 48 that is disposed on the front side of the column 6 so as to be substantially flush with the upper surface of the device housing 4. The turntable 48 is formed in a relatively large-diameter disk shape, and is rotated in a direction indicated by an arrow 49 by a rotation driving mechanism (not shown).

  On the turntable 48, four chuck tables 50 are arranged so as to be rotatable in a horizontal plane, being spaced apart from each other by 90 degrees in the circumferential direction. As shown in FIG. 4, each chuck table 50 has a frame body 52 formed of SUS (stainless steel) or the like. A suction path 58 is formed in the part. The suction path 58 is selectively connected to a vacuum suction source (not shown).

  A suction portion 56 made of porous ceramics or the like is fitted in the fitting recess 54 of the frame 52. The suction part 56 of the chuck table 50 has a holding surface 56a formed in a slight mountain shape with the rotation shaft 50a of the chuck table 50 as the apex, and when the radius R of the suction part 56 is 10 cm, the holding surface 56a. The difference in height H between the central part and the peripheral part is about 10 to 20 μm.

  The four chuck tables 50 arranged on the turntable 48 have a wafer carry-in / out region A, a rough grinding region B, a finish grinding region C, a polishing region D, and a turntable 48 as appropriate. The wafer is sequentially moved to the wafer loading / unloading area A.

  Next, a support mechanism for the chuck table 50 will be described with reference to FIGS. As shown in the schematic diagram of FIG. 6, the chuck table 50 is supported by one fixed point 62 and two movable points 64 that are separated from each other by 120 degrees in the circumferential direction.

  30a is a rotation locus of the rough grinding wheel 30, 60 is a processing region where the rough grinding wheel 30 grinds the wafer held by the chuck table 50, the chuck table 50 is rotated in the direction of arrow a, and the grinding wheel 30 is When rotated in the direction of arrow b, the processing region 60 is set from the center of the wafer held by the chuck table 50 toward the outer periphery, and the grinding direction is a direction from the center of the wafer toward the outer periphery. Such a processing region 60 is set by the chevron shape of the holding surface 56a and the inclined state of the holding surface 56a of the chuck table 50 as shown in FIG.

  Referring to FIG. 7, a side view of the support mechanism of the chuck table 50 is shown. The chuck table 50 is disposed on a base 66, and a flange 68 is fixed to the base 66. Reference numeral 70 denotes a frame fixed to the turntable 48.

  The tilt adjustment mechanism 72 of the chuck table 50 includes a pulse motor 74 fixed to the frame 70, a bolt 76 connected to the pulse motor 74, and an adjustment lever 78 having a nut screwed to the tip of the bolt 76. Yes. The fulcrum neck 80 of the adjustment lever 78 is fixed to the upper surface 84 a of the fulcrum block 84. The adjustment lever 78 supports an adjustment block 82 fixed to the flange 68.

  The adjustment lever 78 has a fulcrum 78a fixed to the fulcrum block 84, an action point 78b to which the adjustment block 82 is fixed, and a force point 78c into which the bolt 76 is screwed onto the nut, and is applied to the force point 78c. The force is applied to the action point 78b by the force.

  The fulcrum block 84 is fixed to the frame 70 of the turntable 48, and the fulcrum neck 80 is fixed to the upper surface 84a. The adjustment block 82 is supported at the lower end by the adjustment lever 78 and supports the chuck table 50 via the flange 68 and the base 66. The fixing point 62 is configured by fixing the flange 68 to the shaft 86 disposed on the frame 70 with a predetermined play.

  FIG. 5 is a partial cross-sectional side view showing the relationship between the holding surface 56a of the chuck table 50 and the rough grinding wheel 12, and the holding surface 56a of the chuck table 50 and the tip of the grinding wheel 30 (grinding surface). Maintained in parallel.

  The spindle 22 of the rough grinding unit 12 is supported such that its axis 22a is in the vertical direction, and the central axis 50a of the chuck table 50 is disposed slightly inclined from the vertical direction. In FIG. 5, the inclination of the chuck table 50 is exaggerated.

  As shown in FIG. 2, the polishing unit 88 includes a stationary block 90 fixed on the apparatus housing 4 and an X-axis moving block 92 that is mounted on the stationary block 90 and can be moved in the X-axis direction by the X-axis moving mechanism 94. And a Z-axis moving block 96 mounted on the X-axis moving block 92 and movable in the Z-axis direction by the Z-axis moving mechanism 98.

  A unit housing 100 is disposed in the Z-axis moving block 96, and a spindle 102 is rotatably accommodated in the unit housing 100. A wheel mount 104 is fixed to the tip of the spindle 102, and a polishing wheel 106 is attached to the wheel mount 104 so as to be detachable.

  As shown in FIG. 3, the polishing wheel 106 includes a base 108 attached to the wheel mount 104 and a polishing pad 110 attached to the base 108. The polishing pad 110 is made of, for example, a felt material in which abrasive grains are dispersed in polyurethane or felt and fixed with an appropriate bond agent.

  A polishing liquid supply hole 116 is formed at the center of the base 108 and the polishing pad 110. Further, a plurality of grooves 118 for holding a polishing liquid are formed on the polishing surface (lower surface) of the polishing pad 110.

  Referring to FIG. 1 again, on the front side of the housing 4 of the processing apparatus 2, a first cassette 122 for stocking wafers before processing and a second cassette 124 for storing wafers after processing are detachably mounted. Is done.

  Reference numeral 126 denotes a wafer transfer robot, which transfers the wafer accommodated in the first cassette 122 to the temporary placement table 128 and also transfers the processed wafer cleaned by the spinner cleaning unit 132 to the second cassette 124. .

  Reference numeral 130 denotes a wafer carry-in / out for carrying a wafer from the temporary placement table 128 to the chuck table 50 positioned in the wafer carry-in / out region A, or sucking the processed wafer from the chuck table 50 to the spinner cleaning unit 132. The unit is movable in the X-axis direction, the Y-axis direction, and the Z-axis direction.

  Referring to FIG. 8, there is shown a perspective view of a semiconductor wafer 11 to be processed by the processing method of the present invention. A semiconductor wafer 11 shown in FIG. 8 is made of, for example, a silicon wafer having a thickness of 700 μm, and a plurality of division lines (streets) 13 are formed in a lattice shape on the surface 11a, and a plurality of division lines 13 are formed. A device 15 such as an IC or an LSI is formed in each of the areas partitioned by.

  The semiconductor wafer 11 configured as described above includes a device region 17 in which the device 15 is formed, and an outer peripheral surplus region 19 that surrounds the device region 17. A notch 21 is formed on the outer periphery of the semiconductor wafer 11 as a mark indicating the crystal orientation of the silicon wafer.

  In carrying out the processing method of the present invention, a protective tape 23 is attached to the surface 11a of the semiconductor wafer 11 by a protective tape attaching step in order to protect the device 15 formed on the surface 11a. Therefore, the front surface 11a of the semiconductor wafer 11 is protected by the protective tape 23, and the back surface 11b is exposed as shown in FIG.

  Hereinafter, the processing method of the present invention using the processing apparatus 2 shown in FIG. 1 will be described. The semiconductor wafer 11 having the protective tape 23 adhered to the surface accommodated in the first wafer cassette 122 is pulled out of the first cassette 122 by the wafer transfer robot 126 and transferred to the temporary setting table 128. At 128, the semiconductor wafer 11 is centered.

  Next, the wafer 11 adsorbed by the wafer carry-in / out unit 130 is transported to the chuck table 50 positioned in the wafer carry-in / out region A, and the suction path 58 of the chuck table 50 is connected to a vacuum suction source, so that FIG. As shown in FIG. 3, the suction portion 56 of the chuck table 50 is sucked and held via the protective tape 23.

  After the semiconductor wafer 11 is sucked and held by the chuck table 50, the turntable 48 is rotated 90 degrees in the clockwise direction indicated by the arrow 49 so that the chuck table 50 is positioned in the rough grinding region B facing the rough grinding unit 12.

  In the rough grinding of the semiconductor wafer 11, as shown in FIG. 11, the grinding wheel 26 is moved in the direction of the arrow b while the chuck table 50 is rotated in the direction of the arrow a at, for example, 300 rpm with respect to the semiconductor wafer 11 thus positioned. For example, while rotating at 6000 rpm, the rough grinding unit feed mechanism 14 is operated to bring the grinding wheel 30 for rough grinding into contact with the back surface 11 b of the semiconductor wafer 11.

  Then, the grinding wheel 26 is ground and fed by a predetermined amount at a predetermined grinding feed speed, and rough grinding of the back surface 11b of the semiconductor wafer 11 is performed. The wafer 11 is ground to a desired thickness while measuring the thickness of the wafer 11 with a contact or non-contact thickness gauge.

  When the rough grinding is finished, the turntable 48 is further rotated 90 degrees in the clockwise direction, and the wafer 11 after the rough grinding is positioned in the finish grinding region C. In this finish grinding, as shown in FIG. 12, while rotating the chuck table 50 in the arrow a direction at 300 rpm, for example, the grinding wheel 40 is rotated in the arrow b direction at 6000 rpm, for example, and the finish grinding unit feed mechanism 18 is operated. Then, the grinding wheel 44 for finish grinding is brought into contact with the back surface of the wafer 11.

  Then, the grinding wheel 40 is ground and fed by a predetermined amount at a predetermined grinding feed speed, and the back surface of the wafer 11 is ground. While measuring the thickness of the wafer 11 with a contact-type or non-contact-type thickness measurement gauge, the wafer 11 is finished to a desired thickness, for example, 52 μm.

  The chuck table 50 holding the wafer 11 for which finish grinding has been completed is positioned in the polishing region D facing the polishing unit 88 by further rotating the turntable 48 90 degrees in the clockwise direction.

  As shown in FIG. 13, the polishing pad 110 of the polishing unit 88 of this embodiment has a diameter larger than the diameter of the semiconductor wafer 11. The spindle 102 of the polishing unit 88 has a polishing liquid supply path 103 communicating with the polishing liquid supply path 116 of the polishing wheel 106. Here, it should be noted that the inclination of the chuck table 50 shown in FIG. 13 is the same as the inclination of the chuck table 50 shown in FIG. The inclination of the chuck table 50 of FIG. 12 is exaggerated.

  In the polishing step, with the polishing pad 110 covering the ground semiconductor wafer 11 sucked and held by the chuck table 50, the chuck table 50 is moved to the arrow while supplying the polishing liquid through the polishing liquid supply paths 103 and 116. While rotating in the a direction and rotating the polishing pad 110 in the direction of arrow b, the polishing pad 110 is pressed against the back surface 11b of the semiconductor wafer 11 to polish the back surface 11b of the wafer 11 to a thickness of about 50 μm. By this polishing step, the grinding distortion generated in the grinding step is removed.

  After completion of the polishing step, as shown in FIG. 14, the non-contact thickness measuring device 120 is rotated in the direction of arrow A, and the thickness of the semiconductor wafer 11 is measured at a plurality of points in the radial direction. A wafer cross-sectional shape detecting step for detecting whether the wafer is concave or convex is performed.

  In this wafer cross-sectional shape detection step, as shown in FIG. 15 (A), the central portion has a middle concave shape that is thinner than the outer peripheral portion, or the central portion is thicker than the outer peripheral portion as shown in FIG. It is detected whether it is a middle convex shape. FIG. 15B is a graph showing the thickness detection data of FIG.

  If a concave-concave shape as shown in FIG. 15 is detected in the wafer cross-sectional shape detection step, the rotation shaft 50a of the chuck table 50 in the standard state is rotated by a very small angle in the direction indicated by arrow A as shown in FIG. Then, the holding surface inclination adjusting step is performed in which the rotating shaft 50a is slightly laid down and the central portion of the holding surface 56a is adjusted slightly lower than the standard state.

  On the other hand, if a center-convex shape as shown in FIG. 16 is detected, the rotation shaft 50a of the chuck table 50 is rotated in the direction opposite to the arrow A to slightly raise the rotation shaft 50a, and the central portion of the holding surface 56a is standard. Adjust so that it is slightly higher than the state.

  As a result, the tilt adjustment of the holding surface of one chuck table 50 out of the four chuck tables 50 is completed, and the semiconductor wafer 11 is sucked onto the holding surface 56a of the chuck table 50 in this state from the next time. The rough grinding step, the finish grinding step, and the polishing step are performed by holding.

  For the other three chuck tables 50, after the first rough grinding step, finish grinding step, polishing step, and wafer cross-sectional shape detection step are performed, the inclination of the holding surface 56 a is adjusted based on the cross-sectional shape of the wafer 11. The holding surface inclination adjusting step is performed.

  As described above, when the holding surface tilt adjustment step is completed for all the chuck tables 50, the semiconductor wafer 11 can be further planarized in the second and subsequent grinding and polishing of the semiconductor wafer 11.

  In the above-described embodiment, the example in which the processing method of the present invention is performed on the semiconductor wafer 11 has been described. However, the workpiece is not limited to the semiconductor wafer 11, and other plates such as an optical device wafer and a glass substrate are used. The processing method of the present invention can be similarly applied to the object.

2 Processing device 11 Semiconductor wafer 12 Rough grinding unit 16 Finish grinding unit 23 Protective tape 48 Turntable 50 Chuck table 88 Polishing unit 110 Polishing pad 120 Non-contact thickness measuring instrument

Claims (2)

A plate-like material processing method for continuously grinding and polishing a plurality of plate-like materials,
A plate-like object holding step for holding the plate-like object with a rotatable chuck table having a holding surface for holding the plate-like object;
After holding the plate-like object on the chuck table, the grinding wheel is brought into contact with the plate-like object held on the chuck table while rotating the grinding wheel on which the grinding wheel is mounted while rotating the chuck table. A grinding step for grinding the object to a predetermined thickness;
After performing the grinding step, the polishing pad and the chuck table are respectively rotated while the plate-like object held by the chuck table is covered with a polishing pad having a diameter larger than the diameter of the plate-like object to be polished. Polishing the plate-like object with the polishing pad, and removing the grinding distortion generated in the plate-like object in the grinding step;
After carrying out the polishing step, a plate-like object cross-sectional shape detecting step for measuring the thickness of the polished plate-like substance in a radial direction and detecting whether the cross-sectional shape of the plate-like object is concave or convex; and
Based on the cross-sectional shape of the plate-like object detected in the plate-like object cross-sectional shape detecting step, the holding surface of the chuck table is slightly inclined to adjust so that the polished plate-like object is flattened. A surface tilt adjustment step;
The processing method of the plate-shaped object characterized by comprising. A second plate-like object holding step of holding the second plate-like object by the chuck table after performing the holding surface inclination adjusting step;
The plate-shaped object processing method according to claim 1, wherein the grinding step and the polishing step are performed on the second plate-shaped object in a state where the second plate-shaped object is held by the chuck table.

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