JP6348856B2 - Grinding equipment - Google Patents

Description

  The present invention relates to a grinding apparatus, and more particularly, to a grinding method and a grinding apparatus for grinding a wafer to a uniform thickness by grinding the wafer with respect to a grindstone.

  In the field of semiconductor manufacturing, a grinding apparatus that grinds the surface of a semiconductor wafer such as a silicon wafer (hereinafter referred to as “wafer”) is disposed above a wafer chuck that holds the back surface of the wafer by suction. It is known to grind the surface of a wafer by pressing the grindstone against the wafer while rotating the wafer chuck and the grindstone, respectively.

  In such a grinding apparatus, unevenness in thickness may occur in the wafer after grinding due to a peripheral speed difference in the radial direction of the wafer or the like. Therefore, in order to uniformly grind the thickness of the wafer, a grinding apparatus that grinds the wafer by tilting a wafer chuck that holds the wafer with respect to a grindstone is known. In Patent Document 1, the thickness of the wafer being ground is measured, the cross-sectional shape of the wafer is grasped, and the phase and magnitude of the squareness change between the grindstone and the wafer chuck are calculated. By starting and tilting the wafer chuck, the flatness and parallelism of the wafer surface are improved.

JP-A-9-85619

  However, in the above-described grinding apparatus, since the tilt of the wafer chuck is measured from the displacement amount of each piezoelectric element, it is necessary to tilt the wafer chuck to a desired angle while controlling the applied voltage of the piezoelectric element. There was a problem that the fine adjustment of was complicated.

  Therefore, in order to uniformly grind the thickness of the entire wafer, a technical problem to be solved arises that the tilt of the wafer chuck is accurately and simply adjusted, and the present invention solves this problem. Objective.

  The present invention has been proposed to achieve the above object, and the invention according to claim 1 comprises a grindstone for grinding a wafer and a wafer chuck for sucking and holding the wafer, and grinds the wafer. A grinding apparatus, comprising: a fixed support portion that supports the wafer chuck; and a plurality of movable support portions; and an inclination adjusting means that raises and lowers the movable support portion to tilt the wafer chuck at an arbitrary angle; A coordinate measuring means for measuring coordinates of the wafer and a plurality of measurement points on the wafer chuck with respect to a reference point corresponding to a support part, and deriving a normal vector of a plane including the reference point and the measurement point, There is provided a grinding device comprising a control means for deriving the inclination of the wafer chuck in accordance with a displacement of a normal vector.

  According to this configuration, the wafer chuck is obtained by obtaining the inclination of the wafer chuck based on the displacement of the normal vector of the plane including the reference point corresponding to the fixed support portion and the plurality of measurement points on the wafer and the wafer chuck. The angle can be adjusted easily and accurately. That is, the plurality of movable support portions are moved up and down relative to the fixed support portion, so that the wafer chuck is tilted at an arbitrary angle by swinging around the fixed support portion. The tilt of the wafer chuck is derived according to the displacement of the normal vector of the plane including the reference points before and after the tilt and the measurement points. By deriving the tilt of the wafer chuck according to the displacement of the normal vector, the wafer can be directly measured from the coordinates of the measurement point without indirectly measuring the tilt of the wafer chuck based on the displacement of the movable support. Since the inclination of the chuck can be obtained, the angle of the wafer chuck can be adjusted easily and accurately.

  According to a second aspect of the present invention, in addition to the configuration of the first aspect of the present invention, there is provided a grinding apparatus in which the measurement points are respectively arranged on the wafer and the wafer chuck.

  According to this configuration, in addition to the effect of the first aspect of the invention, the thickness of the wafer can be measured based on the coordinates of the measurement points on the wafer and the coordinates of the measurement points on the wafer chuck.

  According to a third aspect of the present invention, in addition to the configuration of the first or second aspect of the present invention, a shape measuring unit that measures the actual shape of the wafer is provided, and the control unit previously stores the actual shape and the target shape of the wafer. A grinding apparatus is provided that stores a correction angle for correcting the error and makes the inclination of the wafer chuck coincide with the correction angle.

  According to this configuration, in addition to the effects of the first or second aspect of the invention, the normal of the plane including the correction angle for correcting the error between the actual shape of the wafer and the target shape, the reference point, and each measurement point By matching the inclination of the wafer chuck derived based on the displacement of the vector, the entire wafer can be ground with a uniform thickness.

  The present invention obtains the tilt of the wafer chuck based on the displacement of the normal vector of the plane including the reference point before and after the tilt and the measurement point, thereby directly measuring the wafer chuck from the measurement point on the wafer and the wafer chuck. Since the inclination can be obtained, the angle of the wafer chuck can be adjusted easily and accurately.

The top view which shows the grinding-work apparatus which concerns on one Example of this invention. The partially cutaway side view showing a precision grinding stage. The perspective view which shows a wafer chuck and a coordinate measurement means. The schematic diagram which shows a mode that the wafer W is inclined. The schematic diagram which shows the normal vector of the plane containing a reference point and a measurement point. It is a schematic diagram which shows the cross-sectional shape of the wafer when the wafer is tilted about the X axis, (a) shows the cross-sectional shape of the wafer when the tilt angle is increased, and (b) is the tilt angle. This shows the cross-sectional shape of the wafer in the case where the diameter is reduced. It is a schematic diagram which shows the cross-sectional shape of a wafer when the wafer is tilted about the Y axis, (a) shows the cross-sectional shape of the wafer when the tilt angle is increased, and (b) is the tilt angle. This shows the cross-sectional shape of the wafer in the case where the diameter is reduced. The perspective view which shows the wafer chuck and coordinate measuring means which concern on the modification of this invention.

  In order to achieve the purpose of accurately and simply adjusting the tilt of the wafer chuck in order to uniformly grind the thickness of the entire wafer, the grinding apparatus according to the present invention adsorbs the grindstone for grinding the wafer and the wafer. And a wafer chuck for holding the wafer chuck, comprising: a fixed support portion for supporting the wafer chuck; and a plurality of movable support portions; An inclination adjusting means for inclining to an angle, a coordinate measuring means for measuring coordinates of a plurality of measurement points on the wafer and the wafer chuck with respect to a reference point corresponding to the fixed support portion, and a normal vector of a plane including the reference point and the measurement point And control means for deriving the inclination of the wafer chuck in accordance with the displacement of the normal vector.

  Hereinafter, a grinding apparatus 1 according to an embodiment of the present invention will be described. In the following examples, when referring to the number, numerical value, quantity, range, etc. of the constituent elements, the specific number is used unless otherwise specified and clearly limited to a specific number in principle. It is not limited, and it may be a specific number or more.

  In addition, when referring to the shapes and positional relationships of components, etc., those that are substantially similar to or similar to the shapes, etc., unless otherwise specified or otherwise considered in principle to be apparent. Including.

  Further, in order to make the features easy to understand, the drawings may be exaggerated by enlarging the characteristic portions or the like, and the dimensional ratios and the like of the constituent elements are not always the same. In the cross-sectional view, hatching of some components may be omitted in order to facilitate understanding of the cross-sectional structure of the components.

  In this embodiment, the terms “upper” and “lower” correspond to the upper and lower parts in the vertical direction (Z-axis direction).

  FIG. 1 is a diagram showing a device configuration of the grinding device 1. The grinding apparatus 1 includes an INDEX table 2 that can rotate the paper surface of FIG. 1 counterclockwise, four wafer chucks 3 that are spaced apart from each other at an equal interval on the INDEX table 2, and an INDEX table. 2, a grindstone 4 and a polishing cloth (polish pad) 5, a load unit 6 that accommodates a wafer W before processing, an unload unit 7 that accommodates a wafer after processing, and a wafer from the load unit 6. A first arm 8 for transporting the wafer W to the chuck 3 and a second arm 9 for transporting the wafer W from the wafer chuck 3 to the unload unit 7 are provided. Note that the configuration of the grinding apparatus 1 is not limited to the above-described one. For example, the ground wafer W may not be subjected to polishing.

  The grinding apparatus 1 is provided with an alignment stage ST1, a rough grinding stage ST2, a fine grinding stage ST3, a polishing stage ST4, and a cleaning stage ST5. Each stage is partitioned by a shutter (not shown). Each time the INDEX table 2 rotates 90 °, the wafer W is processed in the order of rough grinding, fine grinding, and polishing.

  In the alignment stage ST 1, the first arm 8 takes out the wafer W from the load unit 6 and places the wafer W on the wafer chuck 3. The wafer W is vacuum-sucked by the wafer chuck 3 and fixed integrally with the wafer chuck 3. When the wafer W is attached to the wafer chuck 3, the INDEX table 2 rotates 90 ° counterclockwise on the paper surface of FIG. 1, and the wafer W is transferred to the rough grinding stage ST2. Further, the second arm 9 transports the polished wafer W from the wafer chuck 3 to the unload unit 7.

  In the rough grinding stage ST2, the surface of the wafer W is ground by rotating the grindstone 4 and the wafer chuck 3 respectively and pressing the grindstone 4 against the wafer W. After the rough grinding, the INDEX table 2 rotates 90 ° counterclockwise on the paper surface of FIG. 1, and the wafer W is transferred to the fine grinding stage ST3.

  In the precision grinding stage ST3, the grindstone 4 and the wafer chuck 3 are each rotated, and the grindstone 4 is pressed against the wafer W to grind the surface of the wafer W. After the fine grinding, the INDEX table 2 rotates 90 ° counterclockwise on the paper surface of FIG. 1, and the wafer W is transferred to the polishing stage ST4.

  In the polishing stage ST4, the polishing cloth 5 and the wafer chuck 3 are each rotated, and the polishing cloth 5 is pressed against the wafer W, whereby the surface of the wafer W is polished to a mirror surface. After polishing, the INDEX table 2 rotates 90 ° counterclockwise on the paper surface of FIG. 1, and the wafer W is transferred to the alignment stage ST1.

  In the cleaning stage ST5, after the cleaning liquid is discharged from the cleaning nozzle (not shown) to the polished wafer W transferred to the unload unit 7 by the second arm 9 to remove grinding debris, the unload unit 7 is rotated at high speed. And the wafer W is dried.

  The operation of the grinding apparatus 1 is controlled by the control means 10. The control means 10 controls each component constituting the grinding apparatus 1. The control means 10 is comprised by CPU, memory, etc., for example. The function of the control means 10 may be realized by controlling using software, or may be realized by operating using hardware.

  Next, the precision grinding stage ST3 will be described in detail based on the drawings. FIG. 2 is a partially cutaway side view showing the wafer chuck 3 and the grindstone 4. FIG. 3 is a perspective view showing the wafer chuck 3 and the coordinate measuring means 30.

  In the precision grinding stage ST3, the wafer chuck 3 and the grindstone 4 are arranged to face each other in the vertical direction.

  The grindstone 4 rotates around the rotation axis O1. The grindstone 4 is disposed above the wafer chuck 3 and can move up and down in the vertical direction. The grinding surface of the grindstone 4 is maintained in a horizontal state.

  The wafer chuck 3 includes a chuck base 3a, a rotating portion 3b that supports the chuck base 3a, and a chuck 3c that is formed on the upper surface of the chuck base 3a and has substantially the same diameter as the chuck base 3a. . An adsorbent 3d made of a porous material such as alumina is embedded in the upper surface of the chuck 3c. The rotating part 3b rotates around the rotation axis O2 by the motor 3e via the rotary joint 3f and the pulley 3g.

  In the chuck 3c, a pipe line 3h extending from the center of the chuck 3c to the surface of the chuck 3c through the chuck base 3a and the rotating portion 3b is provided. The pipe line 3h is connected to a vacuum source, a compressed air source, and a water supply source (not shown). When the vacuum source is activated, the wafer W placed on the chuck 3c is attracted and held by the chuck 3c.

  The fine grinding stage ST3 is provided with an inclination adjusting means 20 and a coordinate measuring means 30.

  The inclination adjusting means 20 includes one fixed support portion 21 that supports the wafer chuck 3 and two movable support portions 22 and 22. The fixed support portion 21 and the movable support portion 22 are arranged at equal intervals of 120 degrees around the wafer chuck 3 in plan view. Hereinafter, a direction parallel to a line segment connecting the two movable support portions 22 and 22 is defined as an X-axis direction, and a direction orthogonal to the X-axis is defined as a Y-axis direction.

  The fixed support portion 21 is a tilt fulcrum that is disposed below the rotating portion 3 b and supports the spindle base 3 i of the wafer chuck 3.

  The movable support 22 includes a tilt motor 22a fixed to the INDEX table 2, a tilt screw 22b connected to the tilt motor 22a, and a nut 22c fixed to the spindle base 3i and screwed into the tilt screw 22b. And. When the tilting motor 22a is driven, the tilting screw 22b rotates and moves forward and backward with respect to the nut 22c, so that the spindle base 3i swings around the fixed support portion 21.

  The coordinate measuring means 30 is a displacement meter disposed so as to face the wafer W and the wafer chuck 3. The displacement meter is, for example, a non-contact type optical sensor. The coordinate measuring means 30 measures the three-dimensional coordinates of the measurement points P1 and P2 (P1 ', P2') facing each other. The coordinates of the measurement points P1 and P2 are measured using the reference point P0 corresponding to the fixed support portion 21 as the origin. The reference point P0 is a point obtained by projecting the fixed support portion 21 onto a reference plane that is a horizontal plane including the measurement points P1 and P2. Hereinafter, the measurement points before tilting the wafer chuck 3 are “P1, P2”, and the measurement points after tilting the wafer chuck 3 are “P1 ′, P2 ′”.

  Further, the precision grinding stage ST3 is provided with a shape measuring means (not shown) for measuring the actual shape of the wafer W. The shape measuring means has a known configuration. For example, the shape of the wafer W can be obtained by scanning the thickness of the wafer W radially.

  Next, a control procedure for the inclination of the wafer W will be described with reference to FIGS. FIG. 4 is a schematic diagram showing a state in which the wafer W is tilted. FIG. 5 is a schematic diagram showing a normal vector V1 of the reference surface S1 including the reference point P0 and the measurement points P1 and P2, and a normal vector V2 of the plane S2 including the reference point P0 and the measurement points P1 ′ and P2 ′. It is.

  When the control device 10 raises and lowers the movable support portion 22 in the vertical direction, the wafer W and the wafer chuck 3 swing and tilt as indicated by a broken line in FIG. The coordinate data of the measurement points P1 and P2 before being tilted and the coordinate data of the measurement points P1 'and P2' after being tilted, which are measured by the coordinate measuring means 30, are sent to the control device 10. Based on these coordinate data, the control device 10 calculates the normal vector V1 of the reference surface S1 including the reference point P0 and the measurement points P1 and P2, and the method of the plane S2 including the reference point P0 and the measurement points P1 ′ and P2 ′. A line vector V2 is calculated. Then, as shown in FIG. 5, the control device 10 obtains the inclination of the wafer W from the displacement of the normal vectors V1 and V2 before and after the wafer W is inclined.

  Next, the grinding procedure in the precision grinding stage ST3 will be described with reference to FIGS. FIG. 6 is a schematic diagram showing a cross-sectional shape of the wafer W when the wafer W is tilted around the X axis. FIG. 7 is a schematic diagram showing a cross-sectional shape of the wafer W when the wafer W is tilted about the Y axis.

  In the precision grinding stage ST3, the actual shape of the wafer W is measured using shape measuring means. The shape measuring means sends the shape data of the actual shape of the wafer W to the control means 10.

  Based on the actual shape data of the wafer W, the control means 10 derives a correction angle for tilting the wafer W about the X axis and the Y axis. Here, the “correction angle” refers to an angle at which the wafer W is tilted about the X axis and the Y axis in order to perform grinding so that the shape of the wafer W matches the actual shape of the wafer W. Further, the “target shape” refers to a wafer shape in which the wafer W is formed flat on both the front and back surfaces. By tilting the wafer W about the X axis and the Y axis, the shape of the wafer W can be ground to a desired shape. For example, when the inclination angle around the X axis is increased, as shown in FIG. 6A, the cross-sectional shape of the wafer W is formed in a convex shape, and when the inclination angle around the X axis is reduced, FIG. As shown in FIG. 3, the cross-sectional shape of the wafer W is formed in a concave shape. Further, when the tilt angle around the Y axis is increased, the cross-sectional shape of the wafer W is formed in an M shape as shown in FIG. 7A, and when the tilt angle around the Y axis is decreased, FIG. ), The cross-sectional shape of the wafer W is formed in a W shape. Therefore, the correction angle is set to an appropriate angle according to the error between the actual shape of the wafer and the target shape. The correction angle is recorded in advance in the control means 10.

  Then, the control device 10 normalizes the normal vector V1 of the reference surface S1 including the reference point P0 and the measurement points P1 and P2, and the normal vector of the inclined surface S2 including the reference point P0 and the measurement points P1 ′ and P2 ′. The movable support portion 21 is controlled so that the inclination of the wafer W about the X axis and Y axis derived from the displacement from V2 coincides with the correction angle about the X axis and Y axis derived by the control means 10.

  As a modification of the present embodiment in which the coordinates of the surface of the wafer W and the wafer chuck 3 are directly measured, one in which the coordinates of the surface of the wafer W and the wafer chuck 3 are indirectly measured can be considered. In such a modification, as shown in FIG. 8, measurement points P <b> 1 and P <b> 2 may be provided on the spindle base 3 i of the wafer chuck 3. In FIG. 8, the coordinate measuring means 30 is a sensor embedded in the lower surface of the spindle base 3i. In addition to the above, the measurement points P1 and P2 may be in any arrangement as long as the reference point and the plurality of measurement points form a plane. It should be noted that the interval between measurement points is preferably long. Thereby, the Z coordinate of the measurement point when the wafer W and the wafer chuck 3 are tilted can be measured with high accuracy.

  In this way, the grinding apparatus 1 according to this embodiment described above uses the reference surface S1 including the reference point P0 corresponding to the fixed support portion 21 and the measurement points P1 and P2 on the wafer W and the wafer chuck 3. The inclination of the wafer W and the wafer chuck 3 is obtained by obtaining the inclination of the wafer chuck 3 based on the line vector V1 and the displacement of the normal vector V2 of the plane S2 including the reference point P0 and the measurement points P1 ′ and P2 ′. Since it is obtained directly, the angle of the wafer chuck 3 can be adjusted easily and accurately.

  Further, by disposing the measurement point P1 on the wafer W and disposing the measurement point P2 on the wafer chuck 3, the thickness of the wafer W can be measured based on the coordinates of the measurement points P1 and P2.

  Further, by matching the correction angle for correcting the error between the actual shape of the wafer W and the target shape and the inclination of the wafer chuck 3 derived based on the displacements of the normal vectors V1 and V2, the entire wafer W can be obtained. Grinding can be performed with a uniform thickness.

  The present invention can be variously modified without departing from the spirit of the present invention, and the present invention naturally extends to the modified ones.

DESCRIPTION OF SYMBOLS 1 ... Grinding device 2 ... INDEX table 2a ... Partition wall 3 ... Wafer chuck 4 ... Grinding wheel 4a ... Grinding stone feeder 5 ... Polishing cloth (polish pad)
6 ・ ・ ・ Load unit 7 ・ ・ ・ Unload unit 8 ・ ・ ・ First arm 9 ・ ・ ・ Second arm 10 ・ ・ ・ Control means 20 ・ ・ ・ Inclination adjustment means 21 ・ ・ ・ Fixed support 22・ ・ ・ Movable support 22a ・ ・ ・ Tilt motor 22b ・ ・ ・ Tilt screw 22c ・ ・ ・ Nut 30 ・ ・ ・ Coordinate measuring means W ・ ・ ・ Wafer P0 ・ ・ ・ Reference point P1, P2, P1 ′, P2 '... measurement point S1 ... plane including reference point and measurement point (before tilting) S2 ... plane including reference point and measurement point (after tilting) V1 ... (tilting) Previous vector V2 ... Normal vector (after tilt)

Claims (3)

A grinding apparatus for grinding a wafer, comprising a grindstone for grinding a wafer and a wafer chuck for sucking and holding the wafer,
Inclination adjusting means comprising a fixed support part for supporting the wafer chuck and a plurality of movable support parts, and tilting the wafer chuck to an arbitrary angle by raising and lowering the movable support part;
Coordinate measuring means for measuring coordinates of the wafer and a plurality of measurement points on the wafer chuck with respect to a reference point corresponding to the fixed support portion;
A control means for deriving a normal vector of a plane including the reference point and the measurement point, and deriving an inclination of the wafer chuck according to a displacement of the normal vector;
A grinding apparatus characterized by comprising:   The grinding apparatus according to claim 1, wherein the measurement points are arranged on the wafer and the wafer chuck, respectively. Comprising a shape measuring means for measuring the actual shape of the wafer;
3. The grinding according to claim 1, wherein the control means stores in advance a correction angle for correcting an error between the actual shape of the wafer and a target shape, and makes the inclination of the wafer chuck coincide with the correction angle. Processing equipment.