JP6632356B2 - Grinding equipment - Google Patents

Description

  The present invention relates to a grinding apparatus that can grind a wafer by tilting the wafer with respect to a grinding wheel, and more particularly, to a grinding apparatus that cancels the influence of a tilt angle caused by frictional heat generated during grinding.

  In the field of semiconductor manufacturing, backside grinding of the backside of a wafer is performed in order to form a semiconductor wafer such as a silicon wafer (hereinafter, referred to as “wafer”) into a thin film.

  As a grinding device for grinding a back surface of a wafer, Patent Document 1 discloses a holding device for holding a wafer, a grinding device for grinding a wafer, a tilt angle adjusting device for adjusting a tilt of the holding device to an arbitrary angle, and a wafer. And a non-contact type thickness measuring means for measuring the thickness at a plurality of points in the radial direction. The tilt angle adjusting means adjusts the tilt of the holding means based on the measured thickness of the wafer so that the thickness of the wafer becomes uniform, and the grinding means grinds the wafer in a state of being in contact with the wafer obliquely. Proceed.

JP 2010-131687 A

  However, in the grinding device described in Patent Document 1 described above, when the holding unit and the tilt angle adjusting unit are thermally deformed by frictional heat generated during the grinding process, the tilt angle adjusted according to the thickness of the wafer becomes a desired tilt angle. The value may be out of the range, and the wafer may not be ground to a desired shape.

  Therefore, a technical problem to be solved arises in that the wafer is ground into a desired shape in consideration of a tilt angle error caused by frictional heat generated during the grinding process. The purpose is to solve.

The present invention has been proposed to achieve the above object, and the invention according to claim 1 has a holding means for holding a wafer, a grinding means for grinding the wafer, and a vertically movable means for vertically expanding and contracting. And a tilting means capable of tilting the holding means with respect to the grinding means, wherein the temperature measuring means measures the temperature of the elevating means, and which acts on the elevating means during grinding. Pressure measuring means for measuring the pressure to be applied, and the amount of expansion and contraction of the elevating means so as to cancel the amount of thermal deformation of the elevating means according to the temperature measured by the elevating means before and after grinding. And correcting means for calculating the amount of compression of the elevating means in accordance with the pressure acting on the elevating means, and correcting the amount of expansion and contraction of the elevating means so as to cancel the compression amount. Grinding equipment To provide.

  According to this configuration, the control means calculates the amount of thermal deformation of the movable support from the temperature difference between the movable support before and after the grinding, and corrects the amount of expansion and contraction of the movable support so as to cancel the amount of thermal deformation. Therefore, even when the movable support portion is thermally deformed due to frictional heat of the grinding process, the wafer can be ground into a desired shape while maintaining the tilt angle at a desired value.

Further , the control means calculates the amount of compression of the movable support part from the pressure acting on the movable support part when the grinding means presses and grinds the wafer, and the amount of expansion and contraction of the movable support part so as to cancel this compression amount. Is corrected, the wafer can be ground into a desired shape while maintaining the tilt angle at a desired value, even when the movable support section sinks during the grinding process.

The invention of claim 2, wherein, in addition to the configuration of the invention according to claim 1, wherein the temperature measuring means provides a grinding apparatus disposed in the vicinity of the lifting means.

According to this configuration, in addition to the effect of the first aspect, the temperature measuring means, since even a slight temperature rise of the movable support member that accurately measurable, is returned to the desired value of tilt angle early be able to.

In the present invention, the control means calculates the amount of thermal deformation of the movable support from the temperature difference between the movable support before and after the grinding process, and corrects the amount of expansion and contraction of the movable support so as to cancel this amount of thermal deformation. Even when the movable support portion is thermally deformed due to frictional heat of the grinding process, the wafer can be ground into a desired shape while maintaining the tilt angle at a desired value . Further, the control means calculates the amount of compression of the movable support portion from the pressure acting on the movable support portion when the grinding means presses and grinds the wafer, and the amount of expansion and contraction of the movable support portion so as to cancel this compression amount. Is corrected, the wafer can be ground into a desired shape while maintaining the tilt angle at a desired value, even when the movable support section sinks during the grinding process.

1 is a partially cutaway side view showing a grinding device according to one embodiment of the present invention. Sectional drawing which shows the internal structure of a wafer chuck. The principal part enlarged sectional view which shows the vicinity of a movable support part. FIG. 4 is a perspective view showing an inclination unit. 4 is a graph showing a state of a temperature change of a wafer rotating mechanism and a tilting unit due to frictional heat during grinding. 7 is a graph showing a tilt angle displacement amount when a plurality of wafers are continuously processed.

  The grinding apparatus according to the present invention has a holding unit for holding a wafer in order to achieve a purpose of grinding the wafer into a desired shape in consideration of a tilt angle error caused by frictional heat generated during grinding. A grinding means for grinding a wafer; and a tilting means capable of tilting the holding means with respect to the grinding means by means of a vertically expandable / contractible elevating means, wherein the temperature of the elevating means is Temperature measuring means for measuring the amount of thermal deformation of the elevating means before and after grinding, and calculates the amount of thermal deformation of the elevating means, and corrects the amount of expansion / contraction of the elevating means so as to cancel the amount of thermal deformation. And control means for performing the operations.

  Hereinafter, a grinding device 1 according to an embodiment of the present invention will be described with reference to the drawings. In the following examples, when referring to the number, numerical value, amount, range, and the like of the constituent elements, unless otherwise specified and in principle clearly limited to a specific number, the specific number is used. The present invention is not limited to this, and may be more than or less than a specific number. The configuration of the apparatus is not limited to a grinding apparatus, and a polishing apparatus in which a grinding shaft is replaced with a polishing shaft may be used.

  Also, when referring to the shape and positional relationship of components, etc., those that are substantially similar or similar to the shape, etc., unless otherwise specified, and in cases where it is clearly considered in principle not so, etc. Including.

  In addition, the drawings may be exaggerated, for example, by enlarging a characteristic portion in order to make the characteristics easy to understand, and the dimensional ratios and the like of the components are not always the same as the actual ones. In the cross-sectional views, hatching of some components may be omitted in order to make the cross-sectional structure of the components easy to understand.

  FIG. 1 is a partially cutaway side view showing a basic configuration of the grinding apparatus 1. FIG. 2 is a sectional view showing the wafer chuck 3. FIG. 3 is an enlarged sectional view of a main part showing the vicinity of the movable support part 83. FIG. 4 is a perspective view showing the tilting means 5.

  The grinding device 1 forms a thin film by grinding the back surface of the wafer W by the grinding means 2. The grinding means 2 includes a grindstone 21, a spindle 22 having the grindstone 21 attached to the tip, and a spindle feed mechanism 23 for feeding the spindle 22 at a predetermined feed speed.

  The grindstone 21 is mounted horizontally on the tip of the spindle 22, and the ground surface of the grindstone 21 is maintained in a horizontal state. The wafer W is ground by pressing the grindstone 21 against the wafer W.

  The spindle 22 rotates the grindstone 21 around the rotation axis A1 by a motor (not shown).

  The spindle feed mechanism 23 extends along the vertical direction V, and is provided with a ball screw 23a mounted on the column 4, a motor 23b disposed at an upper end of the ball screw 23a, for rotating the ball screw 23a, and a rotation of the ball screw 23a. And a slider 23c that moves up and down.

  Below the grinding means 2, a wafer chuck 3 is arranged. The wafer chuck 3 includes a wafer holding mechanism 5 for holding the wafer W, and a wafer rotating mechanism 6 for rotating the wafer W. In order to continuously grind a plurality of wafers W, the grinding apparatus 1 includes a plurality of wafer chucks 3. The plurality of wafer chucks 3 are arranged on the index table 7 at predetermined intervals on the circumference around the rotation axis A1.

  The wafer holding mechanism 5 includes a chuck base 51, a chuck 52 having substantially the same diameter as the chuck base 51 and mounted on the upper surface of the chuck base 51, and a porous material such as alumina embedded in the upper surface of the chuck 52. And an adsorbent 53 composed of:

  The wafer holding mechanism 5 includes a pipe 54 extending from the inside of the chuck 52 to the surface of the chuck 52 through the chuck base 51 and the wafer rotating mechanism 6. The pipe 54 is connected to a vacuum source, a compressed air source, and a water supply source (not shown) via a rotary joint 62 described later. When the vacuum source is activated, the wafer W placed on the chuck 52 is held by the chuck 52 by suction. When the compressed air source or the water supply source is activated, the suction between the wafer W and the chuck 52 is released.

  The wafer rotation mechanism 6 rotates the wafer W held by the wafer holding mechanism 5 around the rotation axis A2. The rotation direction of the wafer W is set opposite to the rotation direction of the grindstone 21. The wafer rotation mechanism 6 includes a motor 61, a rotary joint 62, and an air bearing 63.

  The motor 61 is mounted on the back surface of the index table 7. A belt 61 b is hung on an output shaft 61 a of the motor 61 and a pulley 62 a of the rotary joint 62, and the output of the motor 61 is transmitted to the rotary joint 62.

  The rotary joint 62 has a non-rotating portion fixed to the index table 7 and a rotating portion connected to the chuck base 51 via a rotor 63a described later. The rotary joint 62 is rotatable around the rotation axis A2.

  The air bearing 63 includes a rotor 63a rotatable around the rotation axis A2, and a stator 63b arranged on the outer periphery of the rotor 63a. The rotor 63a and the chuck base 51 are fixed via bolts 63c. A predetermined gap (air gap) is provided between the rotor 63a and the stator 63b, and by supplying compressed air to the gap from the outside, the rotor 63a rotates without contact with the stator 63b. be able to.

  The grinding apparatus 1 is provided with a tilting means 8 for tilting the rotation axis A2 of the wafer chuck 3 with respect to the rotation axis A1 of the grindstone 21. The tilting means 8 includes a tilt table 81, a fixed support 82, and a movable support 83.

  The tilt table 81 is formed in a substantially triangular shape in plan view. In the tilt table 81, one fixed support part 82 and two movable support parts 83 are arranged 120 degrees apart on the circumference around the rotation axis A2.

  The fixed support portion 82 is fastened to the tilt table 81 with bolts 82a. The fixed support 82 is arranged below the grindstone 21. The fixed support portion 82 may be provided with a temperature measuring unit and a pressure measuring unit (not shown).

  The movable support portion 83 includes a nut 83a embedded in the tilt table 81, a tilt ball screw 83b fixed to the index table 7 and having an upper portion screwed to the nut 83a, and a tilt motor 83c for rotating the tilt ball screw 83b. , Is provided. The movable support 83 is formed longer than the fixed support 82. One of the two movable support portions 83 is disposed below the grindstone 21. Note that the movable support portion 83 only needs to be able to expand and contract in the vertical direction V, and may be, for example, an air cylinder or the like.

  The grinding device 1 includes a contact-type temperature sensor 9a and a non-contact-type temperature sensor 9b as temperature measuring means 9 for measuring the temperature of the movable support portion 83. The temperature measuring means 9 is a known temperature sensor, and may be a contact type or a non-contact type. It is preferable that the temperature measuring means 9 is disposed near the movable support portion 83 and accurately measures a temperature change of the movable support portion 83. The contact-type temperature sensor 9a is embedded at the upper end of the tilt ball screw 83b, and measures the temperature of the upper portion of the tilt ball screw 83b. The non-contact temperature sensor 9b is arranged near the center of the tilt ball screw 83b, and measures the temperature at the center of the tilt ball screw 83b.

  The grinding device 1 includes a load cell 10 for measuring a pressure acting on the movable support 83. The load cell 10 measures the pressure acting on the movable support 83 when pressing the grindstone 21 against the wafer W.

  The operation of the grinding device 1 is controlled by the control device 11. The control device 11 controls each component of the grinding device 1. The control device 11 includes, for example, a CPU, a memory, and the like. Note that the function of the control device 11 may be realized by controlling using software, or may be realized by operating using hardware.

  The control device 11 tilts the rotation axis A2 with respect to the rotation axis A1 based on the current thickness of the wafer W measured by a thickness sensor (not shown) so that a desired wafer thickness is obtained. The processing area for grinding W is adjusted. In addition, the thickness sensor is not limited to the one included in the configuration of the grinding device 1, and may be, for example, a device that feeds back the data measured by an external device of the grinding device 1 to the control device 11. Hereinafter, the angle of the rotation axis A2 with respect to the rotation axis A1 is referred to as “tilt angle”. The two movable support portions 83 can be independently extended and contracted in the vertical direction V, and the tilt table 81 can be tilted with respect to the fixed support portion 82 to tilt the rotation axis A2.

  The control device 11 stores data of the grinding amount of the wafer W according to the tilt angle. Thereby, the thickness of the wafer W before or during grinding is measured, and the grinding amount and the tilt angle are adjusted based on this thickness and the desired thickness. Further, the control device 11 stores data relating to the amount of thermal deformation and the amount of compression of the movable support portion 83. Specifically, the data relating to the amount of thermal deformation is, for example, the length of the tilt ball screw 83b, the linear expansion coefficient of the tilt ball screw 83b, and the like. The data on the compression amount is, for example, the length, the longitudinal elasticity coefficient, the cross-sectional area, and the like of the tilt ball screw 83b.

  Next, the operation of the tilting means 8 will be described. FIG. 5 is a graph showing how the temperature of the air bearing 63 and the tilt ball screw 83b changes due to frictional heat during grinding. FIG. 6 is a graph showing the amount of displacement of the tilt angle when a plurality of wafers W are continuously processed.

  The temperature of the wafer rotation mechanism 6 and the tilting means 8 is increased by frictional heat generated when the wafer W is ground. The temperature difference of the temperature rise differs according to the distance between the member and the wafer W. For example, as shown in FIG. 5, the processing proceeds with the air bearing 63 near the wafer W and the tilt ball screw 83b far from the wafer W. As a result, a temperature difference occurs. Therefore, it is preferable that the temperature measuring means 9 is arranged near the tilt ball screw 83b. Thereby, the temperature change of the tilting means 8, especially the temperature of the movable support portion 83 can be accurately measured.

  Further, the tilt angle of the tilting means 8 also changes according to the pressure acting on the movable support 83. Specifically, as shown in FIG. 6, when the grinding process is started, the wafer holding mechanism 5 is settled down by the pressure acting on the movable support portion 83, and the movable support portion 83 is compressed in the longitudinal direction. Becomes smaller. Next, until the wafer W is ground to a desired thickness, the movable support portion 83 extends and the tilt angle increases. When the wafer W is continuously processed, the displacement of the tilt angle of the wafer W is integrated without resetting the tilt angle when replacing the wafer W.

  Therefore, the tilt angle of the inclination means 8 is appropriately corrected as follows. First, the control device 11 obtains the amount of thermal deformation ΔLs in the longitudinal direction of the movable support 83 based on the temperatures of the movable support 83 before and after grinding measured by the contact temperature sensor 9a and the non-contact temperature sensor 9b. .

  Then, the control device 11 adjusts the tilt angle in consideration of the thermal deformation amount ΔLs. Specifically, the control unit 11 obtains a tilt angle necessary for grinding the wafer W to a desired thickness and a pre-correction expansion / contraction amount ΔL1 of the tilt ball screw 83b that realizes the tilt angle. Next, the control means 11 reduces the pre-correction expansion / contraction amount ΔL1 by the thermal deformation amount ΔLs to obtain a corrected expansion / contraction amount ΔL2 of the tilt ball screw 83b. That is, the control unit 11 corrects the amount of expansion and contraction of the movable support 83 so as to cancel the amount of thermal deformation ΔLs.

  Since the movable support portion 83 is formed to be longer than the fixed support portion 82, the fixed support portion 83 is thermally deformed more greatly than the fixed support portion 82. Therefore, by reducing the amount of thermal deformation ΔLs of the movable support portion 83, the effect of frictional heat can be significantly reduced. Note that the control device 11 may correct the amount of expansion and contraction in consideration of the thermal deformation of the fixed support portion 82. That is, the corrected expansion / contraction amount ΔL2 can cancel the influence of frictional heat by subtracting the thermal deformation amount ΔLs of the movable support portion 83 and adding the thermal deformation amount ΔL ′ of the fixed support portion 82 to the expansion / contraction amount ΔL1 before correction. it can.

  Further, the control device 11 obtains the amount of compression ΔLp of the movable support portion 83 in the longitudinal direction based on the pressure measured by the load cell 10.

  The control device 11 adjusts the tilt angle of the tilt stage 81 in consideration of the compression amount ΔLp. That is, the control means 11 adds the compression amount ΔLp to the corrected expansion / contraction amount ΔL2 of the tilt ball screw 83b, and obtains the re-corrected expansion / contraction amount ΔL3 of the movable support 83 so as to cancel the compression amount ΔLp.

  In particular, a higher pressure acts on the movable support portion 83 disposed below the grindstone 21 during the grinding process than the other movable support portion 83. Therefore, it is preferable that the pressure acting on the two movable support portions 83 is individually measured, and the compression amount ΔLp and the re-correction expansion / contraction amount ΔL3 are individually obtained for each movable support portion 83. Note that the control device 11 may correct the amount of expansion and contraction in consideration of the amount of compression of the fixed support portion 82. That is, the re-correction expansion / contraction amount ΔL3 is obtained by adding the compression amount ΔLp of the movable support portion 83 to the correction expansion / contraction amount ΔL2 and reducing the compression amount ΔL ″ of the fixed support portion 82, and thereby the pressure generated by pressing the grindstone 21 during grinding. Can be more accurately canceled.

  Thus, in the above-described grinding apparatus 1, the control device 11 calculates the amount of thermal deformation of the movable support portion 83 from the temperature difference between the movable support portion 83 before and after the grinding, and cancels the amount of thermal deformation. In order to control the amount of expansion and contraction of the movable support portion 83, the tilt angle of the tilt table 81 is maintained at a desired value even when the movable support portion 83 is thermally deformed due to frictional heat of the grinding process. W can be ground into a desired shape.

  Further, the control means 11 calculates the amount of compression of the movable support portion 83 from the pressure acting on the movable support portion 83 when the grinding means 2 presses and grinds the wafer W, and moves the movable portion 83 so as to cancel the compression amount. In order to control the amount of expansion and contraction of the support portion 83, the wafer W is ground into a desired shape while maintaining the tilt angle of the tilt table 81 at a desired value even when the movable support portion 83 sinks during the grinding process. be able to.

  The present invention can be variously modified without departing from the spirit of the present invention, and it goes without saying that the present invention extends to the modified ones.

DESCRIPTION OF SYMBOLS 1 ... Grinding device 2 ... Grinding means 21 ... Grinding stone 22 ... Spindle 23 ... Spindle feed mechanism 23a ... Ball screw 23b ... Motor 23c ... Slider 3 ... Wafer chuck (Holding means)
4 ... Column 5 ... Wafer holding mechanism 51 ... Chuck base 52 ... Chuck 53 ... Adsorbent 54 ... Pipe line 6 ... Wafer rotation mechanism 61 ... Motor 61a ... -Output shaft 61b-Belt 62-Rotary joint 62a-Pulley 63-Air bearing 63a-Rotor 63b-Stator 63c-Bolt 7-Index table 8- Tilt means 81 Tilt table 82 Fixed support part 82a Bolt 83 Movable support part 83a Nut 83b Ball screw for tilt 83c Motor for tilt 9 Temperature measuring means 9a: contact type temperature sensor 9b: non-contact type temperature sensor 10: load cell 11: control device (control device) Stage)
A1 ... Rotary shaft (of grinding means)
A2 ··· Rotation axis (of wafer chuck) V · · · Vertical direction W · · · Wafer

Claims (2)

A grinding apparatus comprising: holding means for holding a wafer; grinding means for grinding the wafer; and inclining means capable of inclining the holding means with respect to the grinding means by vertically elongating means. hand,
Temperature measuring means for measuring the temperature of the elevating means,
Pressure measuring means for measuring the pressure acting on the elevating means during grinding,
In accordance with the measured temperature of the elevating means before and after grinding, the amount of thermal deformation of the elevating means is calculated, and the amount of expansion / contraction of the elevating means is corrected so as to cancel the amount of thermal deformation , and acts on the elevating means. Control means for calculating the amount of compression of the elevating means according to the pressure to be applied, and correcting the amount of expansion and contraction of the elevating means so as to cancel the amount of compression ;
A grinding device comprising: The temperature measuring means, the grinding apparatus according to claim 1, characterized in that it is arranged in the vicinity of the lifting means.