JP2009010179A - Processing method of wafer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent cracks on the perimeter of a wafer even when the wafer is ground in a condition that it is stuck on a glass substrate and is thinly formed in the thickness of ≤100 μm or ≤50 μm. <P>SOLUTION: When a glass substrate 1 is stuck onto the surface of a wafer W in which two or more devices have been formed through an adhesion material, and the backside of the wafer W is ground and processed so that the thickness of the wafer W may be ≤100 μm, only the backside side W3 of a device area in which two or more devices have been formed is ground, and the perimeter side W4 thereof is not ground so that a ring shape thick portion is made to remain. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a wafer processing method for thinly processing a wafer by grinding the back surface.

  A plurality of wafers formed by dividing devices such as IC and LSI by dividing lines are ground to the desired thickness and then divided into individual devices by a dicing machine etc. It's being used.

  In recent years, a technique for stacking and packaging a plurality of devices has been proposed in order to enable weight reduction and miniaturization of electronic equipment. For this reason, the thickness of the device is 100 μm or less and 50 μm or less. It is required to make it thinner.

  However, if the thickness of the device is reduced to 100 μm or less and 50 μm or less by grinding the back surface at the wafer stage in order to make the device thinner, there is a problem that handling of the wafer after grinding becomes difficult. In view of this, a technique for sticking the front surface of a wafer to a highly rigid glass substrate and grinding the back surface of the wafer to a desired thickness has been proposed by the present applicant and is put into practical use (see, for example, Patent Document 1).

JP 2004-296839 A

  However, even if the wafer is attached to glass, if the wafer is thinly formed by grinding such as 100 μm or less and 50 μm or less by grinding, the outer peripheral portion of the wafer is chipped, and the wafer is removed from the glass substrate. There is a problem that the wafer is damaged.

  Therefore, the problem to be solved by the present invention is to prevent the wafer from being damaged even if the wafer is ground while being attached to a glass substrate and the thickness thereof is reduced to 100 μm or less, 50 μm or less. It is to be.

  The present invention relates to a wafer processing method in which a glass substrate is bonded to the front surface of a wafer on which a plurality of devices are formed via an adhesive, and the back surface of the wafer is ground to reduce the wafer thickness to 100 μm or less. Thus, there is an outer peripheral surplus area surrounding the device area where a plurality of devices are formed on the surface of the wafer, and the back surface side of the device area is ground to form a concave portion, and the outer peripheral surplus area is included on the outer peripheral side of the concave portion. The ring-shaped thick part is left, and the thickness of the device region is processed to 100 μm or less.

  In this wafer processing method, the adhesive material is a type of adhesive material whose adhesive strength is reduced by an external stimulus, and the wafer with the ring-shaped thick portion remaining is removed from the glass substrate by applying an external stimulus to the adhesive material. It is desirable to do so.

  In the present invention, the wafer is bonded to a glass substrate and the back surface of the wafer is ground so that the ring-shaped thick portion including the outer peripheral surplus region on the outer peripheral side of the device region remains, so that the device region portion is 100 μm or less, 50 μm. Even if it becomes thinner as follows, the outer periphery of the wafer is not chipped. Therefore, it can be removed from the glass substrate without damaging the wafer after grinding.

  On the surface Wa of the wafer W shown in FIG. 1, a plurality of devices D are formed by being partitioned by streets S, and a portion where the plurality of devices D are formed constitutes a device region W1. Further, an outer peripheral surplus area W2 that is an area where no device is formed is formed on the outer peripheral side of the device area W1, and the device area W1 is surrounded by the outer peripheral surplus area W2. In polishing the back surface Wb of the wafer W, in order to protect the device D, the glass substrate 1 is attached to the front surface Wa of the wafer W via an adhesive material, and the state is turned over as shown in FIG. . The glass substrate 1 has a sufficient thickness for stably supporting the wafer W. Moreover, it is desirable that the adhesive used here is of a type whose adhesive strength is reduced by an external stimulus. For example, it is possible to use a UV curable adhesive material whose adhesive strength decreases when irradiated with ultraviolet rays.

  Next, the portion corresponding to the device region W1 of the back surface Wb of the wafer W, that is, the back side of the device region W1, is ground, and the thickness of the device region W1 is set to a desired thickness of 100 μm or less. For such grinding, for example, a grinding apparatus 2 shown in FIG. 3 can be used.

The grinding apparatus 2 includes a chuck table 20 that holds a wafer, and a grinding unit 21 that performs grinding on the wafer held on the chuck table 20. The grinding part 21
The rotary shaft 22 has a vertical axis and a wheel 23 attached to the lower end of the rotary shaft 22. A grindstone 24 is fixed to the lower surface of the wheel 23.

  The wafer W is in a state where the glass substrate 1 side is held by the chuck table 20 and the back surface Wb is exposed. Then, as the chuck table 20 rotates and the grinding unit 21 descends while the wheel 23 rotates, the rotating grindstone 24 comes into contact with the back surface Wb of the wafer W to perform grinding. At this time, the grindstone 24 is brought into contact with the back side of the device region W1 (see FIG. 1) formed on the surface Wa of the wafer W, and the outer peripheral side thereof is not ground. Then, the back side of the device region W1 is ground by a desired amount. When the thickness reaches 100 μm or less and reaches a desired value, the grinding is finished. Thus, by grinding only the back side of the device region W1 in the back surface Wb, as shown in FIG. 4 and FIG. 5, a concave portion W3 is formed on the back surface Wb. The ring-shaped thick part W4 having the same thickness as that remains. Since the ring-shaped thick portion W4 remains on the wafer W, the outer periphery of the wafer W is not chipped by grinding.

  In addition, the width | variety of the ring-shaped thick part W4 should just be about 2-3 mm, for example. Further, it is desirable that the thickness of the ring-shaped thick portion W4 is several hundred μm. On the other hand, the thickness of the device region W1 can be reduced to about 30 μm. After the back surface is ground, the wafer W is removed from the chuck table 20. However, since the outer periphery of the wafer W is not chipped, there is no possibility that the wafer W is damaged during the removal.

  After the ring-shaped thick portion is formed, a metal film made of gold, silver, titanium or the like is formed on the back surface Wb of the wafer W, and an electrical test of each device D is performed. When forming a metal film on the back surface Wb, for example, a reduced pressure film forming apparatus 3 shown in FIG. 6 can be used. The vacuum film forming apparatus 3 includes a holding unit 32 that holds the wafer W in an electrostatic manner inside a chamber 31. A sputtering source 34 made of metal is an excitation member at an opposed position above the holding unit 32. It is arranged in a state supported by 33. A high frequency power source 35 is connected to the sputtering source 34. In addition, an inlet 36 for introducing a sputtering gas is provided on one side of the chamber 31, and a decompression port 37 communicating with a decompression source is provided on the other side.

In the reduced pressure film forming apparatus 3, the back surface of the wafer W is held facing the sputtering source 34 by holding the glass substrate 1 side electrostatically in the holding unit 32. Then, a high frequency power of about 40 kHz is applied from the high frequency power source 35 to the sputtering source 34 magnetized by the excitation member 33, and the inside of the chamber 31 is decompressed to about 10 ⁻² Pa to 10 ⁻⁴ Pa from the decompression port 37 to decompress When the plasma is generated by introducing the argon gas from the introduction port 36 as well as the environment, the argon ions in the plasma collide with the sputtering source 34 and the particles are ejected and deposited on the back surface of the wafer W, as shown in FIG. As shown, a metal film 6 is formed. The metal film 6 has a thickness of about 30 to 60 nm, for example. When the ring-shaped thick portion W4 is masked, the metal film 6 is formed only in the concave portion W3. The metal film formed in this way is formed in a state where the back side of the device region W1 is thinned by grinding. However, since the ring-shaped thick portion W4 is formed on the wafer W, the wafer W can be handled. It becomes easy, and there is no possibility that the wafer W is damaged when the wafer W is taken out from the holding part 32. Note that vapor deposition, CVD, or the like may be used to form the metal film.

  After the formation of the metal film 6, the glass substrate 1 adhered to the surface Wa of the wafer W is peeled off as shown in FIG. At this time, in the case where the adhesive material interposed between the wafer W and the glass substrate 1 is of a type in which the adhesive force decreases due to an external stimulus, the adhesive material is given an external stimulus to increase the adhesive force. After lowering, the glass substrate 1 is peeled off. For example, when the adhesive material is of a type in which the adhesive strength is reduced when irradiated with ultraviolet rays, the adhesive strength of the adhesive material 1a is reduced by irradiating ultraviolet rays from the glass substrate 1 side as shown in FIG. Let Thus, the glass substrate 1 can be easily peeled by reducing the adhesive strength of the adhesive material 1a in advance.

  Next, as shown in FIG. 10, the back surface side on which the metal film 6 is formed is held by the holding table 50, and the holding table 50 is connected to the ground, thereby connecting the wafer W to the ground via the metal film 6. To do. Then, the probe 51 is brought into contact with the device D on the surface side, and the electrical characteristics of each device are tested by a probe test. Since the ring-shaped thick portion W4 is formed on the wafer W, the wafer W can be easily attached and detached during this test.

  Next, the wafer W is divided into individual devices. Prior to the division into devices, as shown in FIG. 11, a step absorbing member 7 having a thickness corresponding to the depth of the recess W3 formed on the back surface of the wafer W is adhered to the dicing tape T, and the step absorbing member The back surface of the wafer W is stuck so that 7 is accommodated in the recess W3 of the wafer W. The outer diameter of the step absorbing member 7 is preferably slightly smaller than the outer diameter of the recess W3. The step absorbing member 7 may be formed integrally with the dicing tape T.

  A dicing frame F on a ring is attached to the outer peripheral portion of the dicing tape T. As shown in FIGS. 12 and 13, the wafer W in which the thickness of the concave portion W3 is absorbed by the step absorbing member 7 is as follows. The dicing tape F is supported by the dicing frame F via the dicing tape T. And the wafer W is divided | segmented into each device D by the cutting device 4 shown, for example in FIG.

  The cutting apparatus 4 includes a chuck table 40 that holds the wafer W via the dicing tape T, and a cutting means 41 that acts on the wafer W held on the chuck table 40 to perform cutting. The chuck table 40 is connected to a drive source 400 and is rotatable. The drive source 400 is fixed to the moving base 401, and the moving base 401 can be moved in the X-axis direction by the cutting feed means 42. The cutting feed means 42 includes a ball screw 420 disposed in the X-axis direction, a pulse motor 421 coupled to one end of the ball screw 420, and a pair of guide rails 422 disposed in parallel to the ball screw 420. A nut (not shown) provided at the lower part of the moving base 401 is screwed into the ball screw 420. The ball screw 420 is driven by the pulse motor 421 to rotate, and accordingly, the moving base 401 is guided by the guide rail 422 and moves in the X-axis direction.

  The cutting means 41 has a configuration in which a cutting blade 412 is attached to the tip of a spindle 411 that is rotatably supported by a housing 410, and the housing 410 is supported by a support portion 413.

  An alignment means 43 for detecting a wafer street is fixed to the side of the housing 410. The alignment unit 43 includes a camera 430 that images the wafer W, and detects a street to be cut by processing such as pattern matching with a key pattern stored in advance based on an image acquired by the camera 430 ( Alignment).

  The cutting means 41 and the alignment means 43 can be moved in the Z-axis direction by the cutting feed means 44. The cutting feed means 44 includes a ball screw 441 disposed in the Z-axis direction in the wall portion 440, a pulse motor 442 that rotates the ball screw 441, and a guide rail 443 disposed in parallel with the ball screw 441. A nut (not shown) inside the support portion 413 is screwed into the ball screw 441. The support part 413 is driven by the pulse motor 442 and guided by the guide rail 443 as the ball screw 441 rotates, and moves up and down in the Z-axis direction. The cutting means 41 supported by the support part 413 also moves in the Z-axis direction. It is configured to move up and down.

  The cutting means 4 can be moved in the Y-axis direction by an index feed means 45. The index feeding means 45 includes a ball screw 450 arranged in the Y-axis direction, a moving base 451 formed integrally with the wall portion 440 and screwed into the ball screw 450, and a pulse motor that rotates the ball screw 450. 452 and a guide rail 453 arranged in parallel with the ball screw 450, and a nut (not shown) inside the moving base 451 is screwed into the ball screw 450. The moving base 451 is driven by the pulse motor 452 and is guided by the guide rail 453 as the ball screw 450 is rotated, and moves in the Y-axis direction. In accordance with this, the cutting means 41 also moves in the Y-axis direction. It has a configuration.

  The wafer W supported by the dicing frame F via the dicing tape T is sucked and held by the chuck table 40 with the surface Wa side exposed. Then, when the chuck table 40 moves in the + X direction, the wafer W moves immediately below the camera 430, and the surface Wa of the wafer W is imaged by the camera 430, and the street S is detected by the alignment means 43 based on the image. At the same time, the street S and the cutting blade 412 are aligned in the Y-axis direction.

  Further, the chuck table 40 is moved in the + X direction by the cutting feed means 42, and the cutting means 41 is lowered by the cutting feed means 44 while rotating the cutting blade 412 at a high speed, and the cutting blade 412 is cut toward the detected street. And cut the street.

  The same cutting is performed sequentially while the cutting means 41 is indexed and fed by the intervals of the streets by the index feeding means 45, and after all the streets in the same direction are cut, the same cutting is performed while rotating the chuck table 40 by 90 degrees. As a result, the wafer W is divided into individual devices D. When each street is cut, if the ring-shaped thick portion W4 on the extended line of the street S is also cut, it is not necessary to remove the ring-shaped thick portion W4 later.

  Before dividing the wafer, as shown in FIG. 15, the front surface of the wafer W is adhered to the dicing tape T so that the back surface is exposed, and the chuck table 40 of the cutting apparatus 4 shown in FIG. 14 is rotated. The cutting blade 412 may be cut along the inner periphery of the ring-shaped thick part W4 and cut into a circle, and the ring-shaped thick part W4 may be removed as shown in FIG. As described above, if the ring-shaped thick portion W4 is removed before the wafer W is divided, only the device region W1 may be cut at the time of the division, and it is not necessary to cut the ring-shaped thick portion W4. Therefore, the moving stroke of the chuck table 40 at the time of cutting the street S can be shortened, and the division can be performed efficiently.

  Further, as shown in FIG. 15, the back surface side of the wafer W is exposed and the ring-shaped thick portion W4 is not removed, or the back surface side of the wafer W is exposed and the ring-shaped thick portion as shown in FIG. If a street to be cut is detected from the back side using an infrared camera in a state where W4 is removed, cutting can be performed as it is and division into devices can be performed.

  In the above example, the case where the division is performed after the formation and the test of the metal film has been described. However, the division may be performed without the formation and the test of the metal film. In this case, both dicing from the back surface and dicing from the front surface are possible. Further, the ring-shaped thick portion can be removed before the dividing step.

It is a perspective view which shows a wafer and a glass substrate. It is the perspective view which looked at the wafer by which the glass substrate was stuck on the surface from the back surface side. It is a perspective view which shows the state which grinds the back surface side of the device area | region of a wafer. It is a perspective view which shows the wafer in which the recessed part was formed in the back surface, and the ring-shaped thick part was formed. It is sectional drawing which shows the wafer in which the recessed part was formed in the back surface, and the ring-shaped thick part was formed. It is sectional drawing which shows an example of a reduced pressure film-forming apparatus roughly. It is sectional drawing which shows the wafer by which the metal film was coat | covered on the back surface. It is a perspective view which shows the state which removes a glass substrate from a wafer. It is sectional drawing which shows the state which irradiates an ultraviolet-ray to an adhesive material. It is a perspective view which shows the state which performs the probe test of a device. It is a perspective view which shows the state which affixes the back surface of a wafer to a dicing tape. It is a perspective view which shows the state in which the wafer was supported by the dicing frame via the dicing tape. It is an expanded sectional view showing the state where a wafer was stuck on dicing tape. It is a perspective view which shows an example of a cutting device. It is a perspective view which shows the state by which the surface of the wafer was affixed on the dicing tape. It is a perspective view which shows the state which removes a ring-shaped thick part from a wafer.

Explanation of symbols

W: Wafer Wa: Front surface S: Street D: Device W1: Device region W2: Peripheral surplus region Wb: Back surface W3: Recessed portion W4: Ring-shaped thick portion T: Dicing tape F: Dicing frame 1: Glass substrate 1a: Adhesive material 2: Grinding device 20: Chuck table 21: Grinding unit 22: Rotating shaft 23: Wheel 24: Grinding wheel 3: Depressurized film forming device 31: Chamber 32: Holding unit 33: Excitation member 34: Sputter source 35: High frequency power source 36: Introduction Port 37: Pressure reducing port 4: Cutting device 40: Chuck table 400: Driving source 401: Moving base 41: Cutting means 410: Housing 411: Spindle 412: Cutting blade 413: Supporting part 42: Cutting feed means 420: Ball screw 421 Pulse motor 422: Guide rail 43: Alignment means 430: Infrared turtle 44: Cutting feed means 440: Wall portion 441: Ball screw 442: Pulse motor 443: Guide rail 45: Index feed means 450: Ball screw 451: Moving base 452: Pulse motor 453: Guide rail 50: Holding table 51: Probe 6: Metal film 7: Step absorbing member

Claims (2)

A wafer processing method in which a glass substrate is attached to the surface of a wafer on which a plurality of devices are formed via an adhesive, and the back surface of the wafer is ground to process the thickness of the wafer to 100 μm or less.
An outer peripheral surplus region surrounding a device region where a plurality of devices are formed exists on the surface of the wafer, and a rear surface side of the device region is ground to form a concave portion, and the outer peripheral surplus region is formed on the outer peripheral side of the concave portion. A method for processing a wafer, in which a ring-shaped thick portion including a remaining portion is left and the thickness of the device region is processed to 100 μm or less.   The pressure-sensitive adhesive material is a pressure-sensitive adhesive material whose adhesive strength is reduced by an external stimulus, and the wafer on which the ring-shaped thick portion remains is removed from the glass substrate by applying an external stimulus to the pressure-sensitive adhesive material. A method for processing a wafer according to 1.

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