JP2009246240A - Grinding method for grinding back-surface of semiconductor wafer and grinding apparatus for grinding back-surface of semiconductor wafer used in same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a grinding method for grinding a back surface of a semiconductor wafer in which the back surface of the wafer can be flatly finished, and a grinding apparatus for grinding the back surface of the semiconductor wafer used in the same. <P>SOLUTION: The grinding method for grinding a back surface of a semiconductor wafer that performs infeed grinding of a back surface of a wafer laminated body 10, during the infeed grinding of the back surface of the wafer laminated body 10, has: measuring respectively a thickness of an outer peripheral portion and an inner peripheral portion of the wafer laminated body 10 with in process gauge; calculating a thickness difference between the thickness of the outer portion and the thickness the inner portion of the wafer laminated body; and tilting an axis R2 of a grinding wheel 15 by a predetermined angle in an optional direction so as to reduce the calculated thickness difference. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for grinding a backside of a semiconductor wafer for grinding the backside of a semiconductor wafer and a semiconductor wafer backside grinding apparatus used therefor.

  In general, as a processing method to reduce the thickness of a semiconductor wafer, a support base material such as glass or resin is bonded to the surface side of the semiconductor wafer, and the semiconductor wafer is fixed to a vacuum chuck on a turntable via the support base material. There is a method of grinding the back surface of the wafer. For example, in this method, the dimension from the upper surface of the turntable to the back surface of the wafer laminate is measured with an in-process gauge as a contact sensor, and the wafer laminate is not removed from the turntable until this thickness reaches a predetermined thickness. Processing and measurement are performed in-process at the same time, and grinding is performed until the wafer thickness reaches a predetermined set dimension.

  As a conventional example related to the grinding method of the back surface of the semiconductor wafer of the present invention, there is one disclosed in Patent Document 1. In paragraph [0005] of Patent Document 1, “... when grinding a wafer, there are several methods for grinding the wafer, and among them, the wafer between two pairs of cylindrical grinding wheels. There is a creep feed grinding method that performs grinding by passing through, and an in-feed grinding method that uses a cup-type grinding wheel to perform grinding while rotating the cup-type grinding wheel and the wafer together so that the wheel passes through the center of the wafer. In particular, the above-described infeed grinding method is often used for grinding semiconductor wafers because of the advantage that high flatness is easily obtained compared to the creep feed type.

  In addition, in paragraph [0006], “Such in-feed type grinding can be performed using, for example, a grinding device 21 as shown in FIG. And holding a chuck table 23 having a grinding head 25 to which a grinding wheel 24 is fixed. For example, a semiconductor wafer 22 to be ground is attracted to the chuck table 23 and rotated. In addition, it is possible to grind one side of the semiconductor wafer by pressing the grinding wheel 24 against the wafer 22 while rotating the grinding head 25 with the rotating shaft 27. "

Japanese Patent Laying-Open No. 2005-205543

  As a problem related to the problem of the present invention, paragraph [0005] of Patent Document 1 states that “a grinding streak having a constant period is formed on the surface of a ground wafer as a trajectory of a grindstone. In addition, although a recess having a shape that is depressed at the center of the wafer is formed, grinding marks on the surface of the wafer can be removed in a polishing process, which is a later process, but in this polishing process, if the polishing amount of the wafer increases. The problem is that the flatness of the wafer deteriorates and the productivity is lowered. "

  The problem that the concave portion is formed in the central portion of the wafer is understood to be complicatedly related to a number of factors such as a grinding device, a grinding wheel, a support structure of a wafer laminate, grinding conditions, and a grinding method. The same applies when a convex portion is formed at the center of the wafer. Thus, the wafer back surface formed by the relative movement between the grinding wheel and the wafer is formed with various factors related to each other, so that the wafer back surface is finished flat with a predetermined accuracy. It is said that it is difficult.

  The present invention provides a semiconductor wafer back surface grinding method and a semiconductor wafer back surface grinding apparatus used therefor that can suppress the formation of a concave portion or a convex portion at the center of the wafer and finish the back surface of the wafer flat.

  One aspect of the present invention is a state in which the wafer laminate is fixed to a table with the front side of the wafer laminate on which the support base material is bonded to face the circuit pattern facing down and the back side to be ground facing up The wafer stack is rotated in a horizontal plane, and the grinding wheel is moved at a predetermined feed rate in the vertical direction while the grinding wheel is rotated about its axis, thereby grinding the back surface of the wafer stack. A method for grinding a back surface of a semiconductor wafer, comprising measuring a thickness of a laminated body of an outer peripheral portion and an inner peripheral portion of the wafer laminated body during grinding of the rear surface of the wafer laminated body, and the outer peripheral portion and the inner peripheral portion. Calculating a difference in thickness of the laminated bodies of the portions, and inclining the axis of the grinding wheel so that the calculated thickness difference is reduced.

  Further, in the method for grinding the back surface of the semiconductor wafer, the axis of the grinding wheel can be tilted so that the in-plane pressure distribution in the contact surface between the grinding wheel and the wafer laminate is constant.

  Further, in the grinding method of a semiconductor wafer back surface, when the laminate thickness of the outer peripheral portion of the wafer laminate is thinner than the laminate thickness of the inner peripheral portion of the wafer laminate, the outer periphery of the wafer laminate The axis of the grinding wheel can be tilted so that the in-plane pressure of the portion is approximately the same as or less than the in-plane pressure of the inner peripheral portion of the wafer stack.

  Another aspect of the present invention is a semiconductor wafer back surface grinding apparatus used in a method for grinding a semiconductor wafer back surface, wherein the grinding wheel having a grindstone surface disposed to face the back surface of the wafer laminate is disposed around the axis. A spindle head that is rotatably supported by the head, measuring means for measuring the thickness of the outer peripheral portion and inner peripheral portion of the wafer laminate, and fine adjustment of the angle of the axis of the grinding wheel with respect to the vertical direction. And an input signal from the measuring means to calculate the thickness difference between the thicknesses of the outer peripheral portion and the inner peripheral portion, and to control the fine angle adjusting means so as to reduce the thickness difference. And a controller.

As described above, according to the present invention, during the infeed grinding of the back surface of the wafer laminate, based on the laminate thickness of the outer peripheral portion and the inner peripheral portion of the wafer laminate measured in-process,
By tilting the axis of the grinding wheel, the difference in thickness between the outer peripheral portion and the inner peripheral portion of the wafer stack can be reduced. Therefore, it is possible to suppress the formation of a concave portion or a convex portion at the center of the wafer and finish the wafer flat.

  Preferred embodiments of a semiconductor wafer back surface grinding method and a semiconductor wafer back surface grinding apparatus used therefor according to the present invention will be described below with reference to the accompanying drawings. Although the typical form of the semiconductor wafer back surface grinding apparatus which concerns on this invention is shown by FIG. 1, this invention is not limited to this. The back surface grinding apparatus 1 of the present embodiment includes an apparatus main body 1a, a turntable 2 that holds the wafer laminated body 10 by vacuum-sucking the surface side of the wafer laminated body 10 to which the support base material 13 is bonded with the chuck 3. The spindle head 4 that rotatably supports the grinding wheel 15 is provided. As one form of the spindle head 4, it has a linear motion feed mechanism that moves the grinding wheel 15 up and down in the vertical direction (vertical direction) and a rotation mechanism that rotates the grinding wheel 15 around the vertical axis R2. Can do. In this example, a ball screw feed mechanism can be applied to the linear motion feed mechanism, and a servo motor can be applied to the rotation mechanism.

  As shown in FIG. 3, each wafer stack 10 that is vacuum-sucked by each chuck 3 is not limited to this embodiment, but a protective film (on the surface 12 a on which a circuit pattern is formed ( A glass base material (support base material) 13 is attached to the chuck 3 in a detachable manner in a state where the glass base material (support base material) 13 is pasted through a not-shown). As an example, the thickness of the semiconductor wafer 11 before grinding is about 750 μm, the thickness of the protective film is about 100 μm, and the thickness of the glass substrate 13 is about 1 mm. The semiconductor wafer 11 is required to have a grinding allowance from the thickness of the single wafer, and is thinly ground to a predetermined thickness, for example, about 30 μm based on this grinding allowance.

  In the back grinding apparatus 1 of the present embodiment, in-feed grinding is performed. As shown in FIG. 2, in-feed grinding is grinding performed while simultaneously rotating the grinding wheel 15 and the wafer laminate 10. That is, the grinding wheel 15 mounted on the spindle head 4 is arranged in a state of facing the wafer laminate 10 in a predetermined positional relationship in the horizontal plane (XY plane), and the wafer laminate 10 is aligned with the chuck 3 along the axis. The grinding wheel 15 is rotated around the axis R <b> 2 in the same direction as the wafer stack 10, and the grinding wheel 15 is moved vertically downward to force the back surface 12 b of the wafer 11 on the grinding wheel surface 16 a. The back surface 12b of the wafer 11 is ground by pressing with. In FIG. 2, the grinding wheel 15 and the wafer stack 10 are rotated in the same direction, but can be rotated in different directions. When the grinding wheel 15 and the wafer stack 10 are rotated in the same direction, the grinding efficiency can be improved. When the grinding wheel 15 and the wafer stack 10 are rotated in different directions, the grinding resistance is reduced. There is an advantage that the processing accuracy of the wafer 11 can be increased.

  Furthermore, the back grinding apparatus 1 of the present embodiment has some new and unique features. The back grinding apparatus 1 of the present embodiment includes in-process gauges 5 and 6 that simultaneously measure the thickness of the outer peripheral portion and the inner peripheral portion of the wafer laminate 10 during grinding of the wafer back surface 12b (see FIG. 3). The fine angle adjusting means 12 for inclining the axis R2 of the grinding wheel 15 with respect to the vertical direction and the input signals from the in-process gauges 5 and 6 are received, and the thickness difference between the outer peripheral portion and the inner peripheral portion is calculated. And a controller 16 for controlling the servo motor of the angle fine adjustment means 12 so that the calculated thickness difference is reduced. The controller has a calculation unit and an automatic angle adjustment unit. The arithmetic unit receives an input signal from the contact sensor, calculates the thickness difference between the outer peripheral portion and the inner peripheral portion of the laminate, and the automatic angle adjusting unit calculates the calculated thickness difference and the axis R2 angle of the grinding wheel 15. The servo motor of the fine angle adjustment means 12 is controlled based on the predetermined relationship.

Each component of the back surface grinding apparatus 1 of this embodiment will be described in detail.
The in-process gauges 5 and 6 as a representative form of the measuring means are obtained by converting changes in the probes 5a and 5b as contacts into a voltage signal by a differential transformer, and the upper surface of the turntable 2 based on the converted voltage signal. This is a measuring instrument for in-process monitoring the distance between the wafer back surface 12b, that is, the thickness δ of the wafer laminate 10 (see FIG. 3). The thickness δ is different for each wafer laminate 10, but is processed up to the position obtained by subtracting the grinding allowance from the thickness δ, so that the individual semiconductors are not affected by the tolerance of the support base 13 and the protective film. The wafer 11 can always be processed to the same thickness.

  The back surface grinding apparatus of the present embodiment includes three in-process gauges 5, 6, and 7. The in-process gauge 7 is for measuring the position of the upper surface of the turntable 2, and the other two in-process gauges 5 and 6 are respectively for the thicknesses of the outer and inner peripheral portions of the wafer laminate 10. It is for measuring. By providing the two in-process gauges 5 and 6, the laminate thicknesses of the outer peripheral portion and the inner peripheral portion of the wafer laminate 10 can be simultaneously measured during the in-process, and the contact between the grinding wheel 15 and the wafer laminate 10 is achieved. A non-uniform distribution of grinding pressure in the surface can be estimated. In the present invention, the number of in-process gauges for measuring the thickness of the wafer laminate 10 is not limited to two, and three or more in-process gauges can be provided.

  The turntable 2 is formed in a disk shape and includes four chucks 3 that can rotate. A glass base material 13 bonded to the wafer laminate 10 is attracted to each chuck 3 by a vacuum pressure. Thereby, the wafer laminated body 10 is held on the chuck 3. After the back surface grinding process, the wafer stack 10 is easily detached from the chuck 3 by supplying air to the chuck 3. An output shaft 21 of the motor 20 is attached to the lower surface of each chuck 3 coaxially with the central axis of the chuck 3. Thereby, the individual chucks 3 are rotated in the clockwise direction by the driving force of the motor 20.

  The grinding wheel 15 is a grinding wheel that grinds the back surface 12b of the semiconductor wafer 10 that is sucked and held by the turntable 2. For example, a diamond grinding wheel that uses a liquid bond as a binder can be used. By making the bonding material a liquid bond, the grindstone 15 has elasticity, the impact force at the time of contact between the grindstone 15 and the wafer laminate 10 is reduced, and the wafer back surface 12b can be processed with high accuracy. The grinding wheel 15 is attached to the spindle head 4 with the grinding wheel surface 16a facing downward.

  The grinding wheel 15 is attached to the spindle head 4 so that its axis R2 is coaxial with the output shaft of a motor (not shown), and rotates counterclockwise by the driving force of the motor. The grinding wheel 15 is trued on the apparatus, and the grinding wheel surface 16a facing the wafer back surface 12b is formed flat. In addition, dressing is performed in order to regenerate a new sharp cutting edge on the surface of the grindstone 15 with reduced sharpness.

  The spindle head 4 includes a spindle 9 on which the grinding wheel 15 is mounted, a ball screw feed mechanism as a linear feed mechanism that moves the grinding wheel 15 up and down in the vertical direction, and a grinding wheel that rotates the grinding wheel 15 about the axis R2. A rotation servomotor and angle fine adjustment means 12 for inclining the axis R2 of the grinding wheel 15 with respect to the vertical direction are provided. By moving the grinding wheel 15 toward the semiconductor wafer 11 by the ball screw feed mechanism, the grinding wheel 15 is brought into contact with the back surface 12b of the semiconductor wafer 11 and a predetermined surface pressure F is applied ( 2), the wafer back surface 12b can be ground.

  5A and 5B exaggerately show the state in which the axis R2 of the grinding wheel 15 is inclined with respect to the vertical direction during the in-process by the angle fine adjustment means 12. FIG. As shown in FIG. 5A, when the thickness of the outer peripheral portion of the wafer laminate 10 is thinner than the thickness of the inner peripheral portion, that is, although not shown, a recess is formed at the center of the semiconductor wafer 11. When formed (when the outer peripheral portion of the semiconductor wafer is formed thicker than the inner peripheral portion), the grinding wheel 15 and the axis R2 of the spindle 9 are angled counterclockwise according to the thickness difference. By tilting by θ1, the grinding pressure (in-plane pressure) at the outer peripheral portion of the wafer laminate 10 is set to be equal to or smaller than the grinding pressure at the inner peripheral portion of the wafer laminate 10. As a result, the difference in thickness between the outer peripheral portion and the inner peripheral portion of the wafer laminate 10 is reduced to 0 to about the same, the grinding pressure in the contact surface between the grinding wheel 15 and the wafer laminate 10 is averaged, and the wafer back surface 12b. Can be formed flat.

  Conversely, as shown in FIG. 5B, when the thickness of the outer peripheral portion of the wafer laminate 10 is thicker than the thickness of the inner peripheral portion, that is, a convex portion at the center of the semiconductor wafer 11. Is formed (when the thickness of the outer peripheral portion of the single semiconductor wafer is smaller than the thickness of the inner peripheral portion), the grinding wheel 15 and the axis R2 of the spindle 9 are turned counterclockwise according to the thickness difference. The angle θ2 is inclined so that the grinding pressure at the outer peripheral portion of the wafer stack 10 is approximately the same as or higher than the grinding pressure at the inner peripheral portion of the wafer stack 10. As a result, the difference in thickness between the outer peripheral portion and the inner peripheral portion of the wafer laminate 10 is reduced to 0 to about the same, the grinding pressure in the contact surface between the grinding wheel 15 and the wafer laminate 10 is averaged, and the wafer back surface 12b. Can be formed flat.

  Next, with reference to FIG. 6, the grinding method of the semiconductor wafer back surface using the back surface grinding apparatus 1 is demonstrated. First, in step S <b> 1, the wafer stack 10 is vacuum-adsorbed to the chuck 3 with the front side of the wafer stack 10 facing down and the back side of the wafer stack 10 facing up. In step S2, the thickness δ of the wafer laminated body 10 integrated with the glass substrate 13 is measured on the apparatus using an in-process gauge or an IR sensor, and the final thickness of the wafer 11 is determined from the thickness δ of the wafer laminated body 10. Is subtracted to find the grinding allowance. The grinding allowance is input to the controller so that the back grinding apparatus 1 is controlled.

  Subsequently, in step S3, the turntable 2 is rotated to position the wafer stack 10 in the horizontal plane so that the wafer stack 10 and the grinding wheel 15 face each other. Next, in step S4, the wafer laminate 10 is rotated by the motor 20, the grinding wheel 15 attached to the spindle head 4 is rotated by the motor, the ball screw is driven to move the grinding wheel 15 downward, and the grinding wheel The 15 grindstone surfaces 16a are pressed against the back surface of the semiconductor wafer 11, and the wafer back surface 12b is ground.

  In step S5, during the backside grinding of the wafer, the in-process gauges 5 and 6 are used to determine the thicknesses of the outer peripheral portion and inner peripheral portion of the wafer laminated body 10 in the region where the wafer laminated body 10 and the grinding wheel 15 are not in contact. Measure with In step S6, after calculating the thickness difference between the outer peripheral portion and the inner peripheral portion of the wafer laminated body 10 by the calculation unit of the controller (not shown), in step S7, the grinding wheel is so adjusted that the calculated thickness difference is reduced. 15 and the axis R2 of the spindle 9 are inclined by a predetermined angle in an arbitrary direction.

  Finally, in step S8, with the grinding wheel 15 and the axis R2 of the spindle 9 inclined, the wafer back surface 12b is processed by a predetermined grinding allowance, and the back surface processing ends.

  After the grinding is completed, polishing is performed by a polishing apparatus (not shown) while the wafer stack 10 is fixed to the chuck 3 to remove a work-affected layer and the like. As a result, damage such as inadvertent cracking of the wafer 11 is prevented. The polished wafer stack 10 is removed from the chuck 3 and transferred to the next process for coating and dicing.

  Thus, according to the semiconductor wafer back surface grinding method and the semiconductor wafer back surface grinding apparatus used therefor according to the present embodiment, the outer peripheral portion and the inner peripheral portion of the wafer stacked body 10 measured in-process during the grinding of the wafer stacked body 10. By tilting the axis R2 of the grinding wheel 15 and the spindle 9 in a predetermined angle based on the thickness of the stacked body, the grinding pressure in the contact surface between the grinding wheel 15 and the wafer stack 10 can be averaged. 12b can be formed flat.

  In addition, this invention is not limited to the said embodiment, In the range which does not deviate from the main point of this invention, it can deform | transform and implement variously. In this embodiment, the wafer laminate 10 is composed of a semiconductor wafer 11, a protective film, and a glass substrate 13. However, as another form, the wafer laminate is composed of a semiconductor wafer, a protective film, and a resin substrate. You can also In addition, a liquid adhesive can be used instead of the protective film for bonding the semiconductor wafer 11 and the base material 13 to each other.

  In addition, the grinding apparatus 1 of the present embodiment includes the in-process gauges 5 and 6. However, if the thickness of the wafer stack 10 fixed to the turntable 2 can be measured, the grinding apparatus 1 is changed to another measuring unit. You can also.

It is a perspective view showing one embodiment of a semiconductor wafer back grinding device concerning the present invention. It is explanatory drawing of in-feed grinding. It is explanatory drawing which shows the state which is measuring the outer peripheral part and inner peripheral part of a wafer laminated body simultaneously with an in-process gauge. It is a side view of a semiconductor wafer back surface grinding apparatus. (A) shows a state where the axis of the grinding wheel is tilted counterclockwise, and (b) is an explanatory view showing a state where the axis of the grinding wheel is tilted clockwise. It is a flowchart of the grinding method of a semiconductor wafer back surface.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Semiconductor wafer back surface grinding apparatus 2 Turntable 3 Chuck 4 Spindle head 5, 6, 7 In-process gauge 10 Wafer laminated body 11 Semiconductor wafer single-piece | unit 12 Angle adjustment means 13 Glass base material (support base material)
15 Grinding wheel 16 Controller

Claims (4)

In order to protect the circuit pattern, the wafer laminate is fixed to the table with the front side of the wafer laminate to which the supporting base material is bonded facing down and the back side to be ground facing up. A method for grinding a backside of a semiconductor wafer, wherein the backside of the wafer laminate is ground by rotating in a horizontal plane and moving the grinding wheel at a predetermined feed rate in the vertical direction while rotating the grinding wheel about its axis. Because
During grinding of the back surface of the wafer laminate,
Measuring the laminate thickness of the outer peripheral portion and inner peripheral portion of the wafer laminate;
Calculating a difference in thickness of the laminate between the outer peripheral portion and the inner peripheral portion;
Inclining the axis of the grinding wheel so that the calculated thickness difference is reduced,
A method for grinding a backside of a semiconductor wafer.   The method for grinding a back surface of a semiconductor wafer according to claim 1, wherein the axis of the grinding wheel is inclined so that an in-plane pressure distribution in a contact surface between the grinding wheel and the wafer laminate is constant.   When the laminate thickness of the outer peripheral portion of the wafer laminate is thinner than the laminate thickness of the inner peripheral portion of the wafer laminate, the in-plane pressure of the outer peripheral portion of the wafer laminate is the wafer. The grinding method of the back surface of a semiconductor wafer according to claim 1 or 2, wherein the axis of the grinding wheel is inclined so as to be equal to or smaller than the in-plane pressure of the inner peripheral portion of the laminated body. It is a semiconductor wafer back surface grinding apparatus used for the grinding method of the semiconductor wafer back surface of any one of Claims 1-3,
A spindle head that supports the grinding wheel having a grinding wheel surface disposed opposite to the back surface of the wafer laminate so as to be rotatable about the axis;
Measuring means for measuring the laminate thickness of the outer peripheral portion and inner peripheral portion of the wafer laminate,
Angle fine adjustment means for inclining the axis of the grinding wheel with respect to the vertical direction;
A controller that receives an input signal from the measuring means, calculates a thickness difference between the laminated body thicknesses of the outer peripheral portion and the inner peripheral portion, and controls the angle fine adjusting means so as to reduce the thickness difference;
A semiconductor wafer back surface grinding apparatus.

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