JP4675559B2 - Laminated wafer processing method - Google Patents

Description

  The present invention relates to a processing method for forming a laminated wafer having a predetermined thickness by laminating a plurality of semiconductor wafers.

  A semiconductor wafer in which a plurality of circuits such as ICs and LSIs are partitioned by streets and formed on the surface is divided into individual semiconductor chips by cutting (dicing) the streets vertically and horizontally and used for various electronic devices.

  Since it is necessary to align the position by mechanical contact in the process of processing, the semiconductor wafer is formed with a predetermined outer diameter, and in order to prevent damage due to mechanical contact, The thickness is formed to a certain extent (for example, about 600 μm), and the outer peripheral side surface is chamfered in an arc shape or the like, and is formed to a predetermined thickness by grinding the back surface after circuit formation (for example, Patent Document 1). reference).

  In recent years, a plurality of semiconductor chips are stacked to improve the function, capacity, processing capability, and the like. When realizing this, a stacked wafer is formed by stacking a plurality of semiconductor wafers. In the laminated wafer, the lowermost first semiconductor wafer is formed to a certain thickness (for example, about 600 μm thick), and the second semiconductor wafer having the same thickness is formed on the first semiconductor wafer. After being laminated on the top surface, the top surface of the second semiconductor wafer can be thinned (for example, having a thickness) to improve heat dissipation or to allow a semiconductor wafer to be further laminated thereon. 50 μm or less). The individual semiconductor wafers constituting the laminated wafer are also chamfered in an arc shape on the outer peripheral side surface to prevent damage.

JP-A-8-37169

  However, since the outer peripheral side surface of the semiconductor wafer having a thickness of about 600 μm is chamfered in an arc shape, when the thickness of the second semiconductor wafer becomes extremely thin, such as 50 μm or less, it is chamfered in an arc shape. The outer peripheral surface is sharpened like a knife (knife edge), and chipping is likely to occur. If the chipping occurs, cracks are generated from the chip and the quality of the semiconductor wafer is significantly deteriorated or cannot be used. There is.

  On the other hand, if the outer periphery of all the semiconductor wafers constituting the laminated wafer is removed by cutting or the like, the outer diameter changes, so that alignment by mechanical contact in the process of processing cannot be performed, There is a disadvantage that it is necessary to modify existing processing equipment.

  Therefore, the problem to be solved by the present invention is to use an existing processing apparatus and perform grinding without reducing the quality of the semiconductor wafer constituting the laminated wafer so that the laminated wafer can be formed to a desired thickness. That is.

The present invention is formed on the outer periphery of a second semiconductor wafer when processing a laminated wafer in which a second semiconductor wafer having a chamfered outer periphery is laminated on the upper surface of the first semiconductor wafer having a chamfered outer periphery. The chamfered portion removing step for removing the chamfered portion and the grinding step for grinding the upper surface of the second semiconductor wafer to form the second semiconductor wafer to a predetermined thickness, Used by an outer peripheral grinding device comprising at least an outer peripheral grinding means having a chuck table for holding a laminated wafer and a grinding wheel for grinding a chamfered portion of a second semiconductor wafer constituting the laminated wafer held by the chuck table. In the grinding process, a chuck table for holding the laminated wafer after the chamfer removal process is completed, and a chuck table A top grinding device comprising at least a top grinding means provided with a grinding wheel for grinding the top surface of the second semiconductor wafer constituting the laminated wafer held on the grinding wheel constituting the peripheral grinding means, a rotating shaft, a circular substrate, which is perpendicular to the rotation axis, is composed of a fixed grinding wheel portion on the outer periphery of the circular substrate, the grindstone portion is formed in a curved surface tapered toward the outer circumferential direction, the chamfered portion is removed In the process, the outer periphery of the second semiconductor wafer is formed in a shape corresponding to the curved surface of the grindstone , and after the grinding process, the stacking of the semiconductor wafer, the chamfered part removing process, and the grinding process are repeatedly performed. The gist is that a plurality of semiconductor wafers can be laminated without causing a knife edge .

  The chamfered portion includes all chamfered portions that are easily damaged by grinding to form a thin thickness.

  The present invention is particularly effective when the second semiconductor wafer constituting the laminated wafer is formed so as to have a thickness of 50 μm or less.

  When the laminated wafer is composed of, for example, three semiconductor wafers, the third semiconductor wafer is laminated on the upper surface of the second semiconductor wafer, and the chamfered portion is removed and the upper surface is ground on the third semiconductor wafer. .

  In the present invention, since the upper surface of the second semiconductor wafer is ground after removing the chamfered portion formed on the outer periphery of the second wafer, the outer periphery can be obtained even if the second semiconductor wafer is thinly ground. It is not formed into an acute angle shape. Therefore, no cracks are generated from the outer periphery, and the quality of the semiconductor wafer is not deteriorated. Further, the first semiconductor wafer is not processed, and the initial outer diameter is maintained, so that mechanical alignment based on the outer diameter of the laminated wafer is possible.

  Furthermore, the chamfered portion can be easily and efficiently removed by using the peripheral grinding means provided with a grinding wheel for grinding the chamfered portion in the chamfered portion removing step. In particular, if the grinding wheel part constituting the grinding wheel is formed into a tapered curved surface toward the outer circumferential direction, and the grinding wheel is used in the outer circumferential removal process, the curved surface shape of the grinding wheel part is transferred to the outer circumference of the second semiconductor wafer. As a result, it is formed into a curved surface, which is more efficient and less prone to chipping. In the case where the thickness of the second semiconductor wafer is extremely thin such as 50 μm or more, chipping is particularly difficult to occur.

  After the upper surface of the second semiconductor wafer is ground, the third semiconductor wafer is laminated on the upper surface of the second semiconductor wafer, and the chamfered portion is the same as in the case of the second semiconductor wafer with respect to the third semiconductor wafer. By performing the removal step and the grinding step, it is possible to stack three or more semiconductor wafers that do not cause chipping without causing a knife edge on the outer periphery.

  As an example of an embodiment of the present invention, a case where the laminated wafer 3 shown in FIG. 1 is processed will be described. The laminated wafer 3 is configured by laminating a second semiconductor wafer 2 on the upper surface of the first semiconductor wafer 1. The upper surface of the first semiconductor wafer 1 and the lower surface of the second semiconductor wafer 2 are connected via bumps or the like. The outer periphery of the first wafer 1 constitutes a chamfered portion 10 that is chamfered in an arc shape. Similarly, the outer periphery of the second wafer 2 also forms a chamfered portion 20 that is chamfered in an arc shape.

  As shown in FIG. 2, an orientation flat 11 indicating a crystal orientation is formed on the first semiconductor wafer 1. Similarly, an orientation flat 21 is formed on the second semiconductor wafer 2. The orientation flat 11 and the orientation flat 21 are also chamfered in an arc shape. In both semiconductor wafers, an orientation notch may be formed instead of the orientation flat.

  First, as shown in FIG. 2, the lower surface of the first semiconductor wafer 1 constituting the laminated wafer 3 is fixed to the support plate 4 by being attached thereto. Then, the chamfered portion 20 of the second semiconductor wafer 2 constituting the laminated wafer 3 fixed to the support plate 4 is removed using, for example, an outer peripheral grinding device 5 shown in FIG.

  The outer peripheral grinding device 5 shown in FIG. 3 includes a chuck table 50 that holds the laminated wafer 3 and outer peripheral grinding means 51 that grinds the outer periphery of the laminated wafer 3. The chuck table 50 is movable in the X-axis direction and is rotatable, and an alignment unit 52 including an imaging unit 520 is disposed above the movement path of the chuck table 50 in the X-axis direction. On the other hand, the outer peripheral grinding means 51 is movable in the Y-axis direction and the Z-axis direction, and a circular substrate 510b is mounted perpendicularly to the tip of a rotating shaft 510a capable of high-speed rotation, and a grindstone portion 510c is disposed on the outer periphery of the circular substrate 510b. A fixed grinding wheel 510 is provided.

  In the peripheral grinding device 5, the laminated wafer 3 is supported by holding the support plate 4 side on the chuck table 50. Then, when the stacked wafer 3 is positioned immediately below the alignment means 52 by moving the chuck table 50 in the + X direction, the upper surface of the second semiconductor wafer 2 is imaged by the imaging means 520 and the position to be ground is detected. The Thereafter, the chuck table 50 further moves in the + X direction, so that the laminated wafer 3 is positioned in the vicinity of the outer peripheral grinding means 51.

  As shown in FIG. 4, the grindstone portion 510c constituting the grinding grindstone 510 is formed in a tapered curved surface shape in the outer peripheral direction (in the illustrated example, the cross section becomes a parabolic shape). First, the peripheral grinding means 51 is lowered while rotating the grinding wheel portion 510c at a high speed by the high speed rotation of the rotating shaft 510a, and the grinding wheel portion 510c is cut into the orientation flat 21 (see FIG. 2) and the chuck table 50 is moved along the X axis. By moving in the direction, the position indicated by a two-dot chain line in FIG. 5, that is, the inner side along the orientation flat 21 is ground to form the straight portion 22, and the chamfered portion 20 at that portion is removed.

  Next, when the grindstone portion 510c is positioned so as to intersect the linear portion 22, and the grindstone portion 510c that rotates at high speed while rotating the chuck table 50 is cut along the outer periphery of the second semiconductor wafer 2 to a predetermined depth, The chamfered portion 20 along the circular outer periphery of the second semiconductor wafer 2 is removed, and a circular portion 23 is formed as shown in FIG.

  In the linear portion 22 and the circular portion 23 shown in FIG. 5, the shape of the grindstone portion 510c shown in FIG. 4 is transferred as it is, so that the second semiconductor wafer 2 of the second semiconductor wafer 2 as shown in the laminated wafer 3a shown in FIG. A curved surface portion 24 corresponding to the curved surface shape of the grindstone portion 510c is formed on the outer peripheral side surface. (Chamfered portion removing step).

  As shown in FIG. 6, the laminated wafer 3a in which the curved surface portion 24 is formed on the outer periphery of the second semiconductor wafer 2 is next subjected to the upper surface of the second semiconductor wafer 2 by the upper surface grinding apparatus 6 shown in FIG. To be ground. The upper surface grinding apparatus 6 includes a chuck table 60 that holds the laminated wafer 3 and upper surface grinding means 61 that grinds the laminated wafer 3. The chuck table 60 is supported by the turntable 62 so as to be rotatable (spinning), and can be revolved by the rotation of the turntable 62.

  The upper surface grinding means 61 is fixed to the support plate 63, and the upper surface grinding means 61 is also raised and lowered as the support plate 63 is driven by the motor 64 and guided by the rail 65 to move up and down.

  The upper surface grinding means 61 is fixed to a spindle 610 having a vertical axis, a mounter 611 formed at the tip of the spindle 610, a grinding wheel 612 fixed to the mounter 611, and a lower surface of the grinding wheel 612. A grinding wheel 613. The grinding wheel 613 has a flat bottom surface that is a contact portion with an object to be ground.

  In the chuck table 60, the support plate 4 side that supports the laminated wafer 3 a is held, and the upper surface of the second semiconductor wafer 2 is exposed, and the laminated wafer 3 a is directly below the upper surface grinding means 61 by the rotation of the turntable 62. Positioned. Then, the grinding wheel 613 is rotated by the rotation of the spindle 610, and the planar lower surface of the rotating grinding wheel 613 contacts the upper surface of the second semiconductor wafer 2 as shown in FIG. To be ground. Then, by grinding a predetermined amount, the second semiconductor wafer 2 is ground to a predetermined thickness (grinding step).

  Since the arc-shaped chamfered portion has already been removed in the chamfered portion removing step, even if the upper surface of the second semiconductor wafer 2 is ground by the grinding step, in the laminated wafer 3b after the grinding step shown in FIG. The outer periphery is not a sharp knife edge. Therefore, no cracks are generated from the outer periphery, and the quality of the semiconductor wafer is not deteriorated. In addition, since the outer periphery of the second semiconductor wafer 2 is chamfered into a curved surface, chipping is unlikely to occur.

  Further, since the first semiconductor wafer 1 is not processed and its outer diameter is maintained, there is no influence on mechanical alignment in each process based on the outer diameter of the laminated wafer 3.

  In addition, after grinding the upper surface of the 2nd semiconductor wafer 2, a 3rd semiconductor wafer can also be laminated | stacked on the said upper surface. In that case, if the chamfered portion removal process and the grinding process are performed on the third semiconductor wafer in the same manner as the second semiconductor wafer, the semiconductor wafers are stacked in layers without causing a knife edge on the outer periphery. Can be made.

  In the present invention, even if the laminated semiconductor wafers are ground and thinned, the outer periphery does not become an acute angle shape, and therefore, it can be used for the production of a high-quality semiconductor wafer having no chipping or cracking.

It is an expanded sectional view showing an example of a lamination wafer. It is a perspective view which shows the same laminated wafer and support plate. It is a perspective view which shows an example of an outer periphery grinding apparatus. It is explanatory drawing which shows the chamfer part removal process using the grinding wheel which comprises the outer periphery grinding apparatus. It is a perspective view which shows the linear part and circular part which are formed in a 2nd semiconductor wafer. It is sectional drawing which shows the laminated wafer after completion | finish of a chamfer part removal process. It is a perspective view which shows an example of an upper surface grinding apparatus. It is sectional drawing which shows the grinding process using the grinding wheel which comprises the same upper surface grinding apparatus. It is sectional drawing which shows the laminated wafer after completion | finish of a grinding process.

Explanation of symbols

1: First semiconductor wafer 10: Chamfered portion 11: Orientation flat 2: Second semiconductor wafer 20: Chamfered portion 21: Orientation flat 22: Straight portion 23: Circular portion 24: Curved portion 3 (3a, 3b): Laminated wafer 4: Support plate 5: Perimeter grinding device 50: Chuck table 51: Perimeter grinding means 510: Grinding wheel
510a: Rotating shaft 510b: Circular substrate 510c: Grinding wheel 52: Alignment means 520: Imaging means 6: Upper surface grinding device 60: Chuck table 61: Upper surface grinding means 610: Spindle 611: Mounter 612: Grinding wheel 613: Grinding wheel 62: Turntable 63: Support plate 64: Motor 65: Rail

Claims (2)

A method for processing a laminated wafer for processing a laminated wafer in which a second semiconductor wafer having a chamfered outer periphery is laminated on an upper surface of a first semiconductor wafer having at least a chamfered outer periphery,
A chamfered portion removing step of removing a chamfered portion formed on the outer periphery of the second semiconductor wafer;
A grinding step of grinding the upper surface of the second semiconductor wafer to form the second semiconductor wafer to a predetermined thickness,
In the chamfered portion removing step, a peripheral grinding means comprising a chuck table for holding the laminated wafer and a grinding wheel for grinding the chamfered portion of the second semiconductor wafer constituting the laminated wafer held by the chuck table A peripheral grinding device composed of at least
In the grinding step, a chuck table for holding the laminated wafer after the chamfered portion removing step is completed, and a grinding wheel for grinding an upper surface of the second semiconductor wafer constituting the laminated wafer held by the chuck table are provided. A top surface grinding device comprising at least a top surface grinding means is used,
The grinding wheel constituting the peripheral grinding means is composed of a rotating shaft, a circular substrate perpendicular to the rotating shaft, and a grindstone portion fixed to the outer periphery of the circular substrate. is formed in a shape tapered curved towards, in the chamfered portion removing step, the outer periphery of said second semiconductor wafer is formed in a shape corresponding to the curved surface of the abrasive Ishibe,
After the grinding step, a plurality of semiconductor wafers can be laminated without causing a knife edge on the outer periphery by repeatedly performing the lamination of the semiconductor wafer, the chamfered portion removal step, and the grinding step . Processing method.   The method for processing a laminated wafer according to claim 1, wherein in the grinding step, the upper surface is ground so that the thickness of the second semiconductor wafer is 50 μm or less.

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