JP2020194896A - Chip manufacturing method - Google Patents

Abstract

To provide a chip manufacturing method capable of processing wafers of different thicknesses under same processing conditions, and manufacturing a chip without causing a processing failure.SOLUTION: A chip manufacturing method includes a processing groove forming step and a modified layer forming step. The processing groove forming step forms a processing groove 26 by irradiating a wafer with a laser beam of a wavelength having absorptivity to a functional layer 24 along division schedule lines from a surface 16 side of a workpiece (wafer 10). The modified layer forming step forms a modified layer 28 serving as a division starting point by irradiating the wafer with a laser beam of a wavelength having permeability to the workpiece along the division schedule lines from a rear surface 18 side of the workpiece after the processing groove forming step. The modified layer forming step includes a multifocal forming step which condenses laser beams using multifocal forming means so that thickness variation 32 per workpiece can be absorbed, and processes the workpiece so as to form a plurality of condensing points in a thickness direction (Z-axis direction) of the workpiece.SELECTED DRAWING: Figure 7

Description

The present invention relates to a method for manufacturing a chip.

As a method of dividing a workpiece such as a semiconductor wafer into chip sizes, a laser beam is irradiated along a planned division line to form a modified layer as a division starting point, a modified layer is formed, and then an external force is applied. A laser processing apparatus that divides the laser processing apparatus is known (for example, Patent Document 1).

JP-A-2002-192370

In the above dividing method, when the thickness varies from wafer to wafer, processing under the same processing conditions may cause processing defects such as diagonal cracks and wafers that cannot be divided. A method has been devised in which the thickness of the wafer is measured before processing and the processing conditions are changed each time based on the measured thickness, but there is a risk of quality variation due to the use of different processing conditions within the same lot. ..

The present invention has been made in view of the above, and provides a method for producing a chip, which can process wafers of different thicknesses under the same processing conditions and produce a chip without causing processing defects. With the goal.

In order to solve the above-mentioned problems and achieve the object, the method for producing a chip of the present invention is a method for producing a chip by processing workpieces having different thicknesses under the same processing conditions. The work piece is partitioned by a plurality of scheduled division lines set in a grid pattern, and has a device including a functional layer in a region divided by the planned division lines on the surface side, and the surface side of the work piece. After the machined groove forming step of forming a machined groove by irradiating the functional layer with a laser beam having a wavelength having absorption along the planned division line, and after the machined groove forming step, the workpiece A modified layer forming step of irradiating a laser beam having a wavelength that is transparent to the workpiece from the back surface side along the planned division line to form a modified layer as a division starting point is included. In the modified layer forming step, the laser beam is focused by using a multifocal forming means so that the thickness variation of each workpiece can be absorbed, and a plurality of focusing points are formed in the thickness direction of the workpiece. It is characterized by including a multifocal forming step that is processed to do so.

In the method for producing a chip, the thickness variation for each workpiece may be caused by grinding the back surface of the workpiece.

In the method for producing a chip, the multifocal forming means may be LCOS.

The present invention has an effect that wafers having different thicknesses can be processed under the same processing conditions to produce chips without causing processing defects.

FIG. 1 is a perspective view of a workpiece of the method for manufacturing a chip according to an embodiment. FIG. 2 is a flowchart showing a flow of a chip manufacturing method according to an embodiment. FIG. 3 is a perspective view showing a back surface grinding step of the chip manufacturing method shown in FIG. FIG. 4 is a perspective view showing a machined groove forming step of the chip manufacturing method shown in FIG. FIG. 5 is a perspective view showing a modified layer forming step of the chip manufacturing method shown in FIG. FIG. 6 is a cross-sectional view showing a modified layer forming step of the chip manufacturing method shown in FIG. FIG. 7 is a cross-sectional view of a work piece subjected to multifocal processing in the method for manufacturing a chip according to an embodiment. FIG. 8 is a flowchart showing the flow of the modified layer forming step in the chip manufacturing method according to the modified example. FIG. 9 is a cross-sectional view of a work piece that has undergone multifocal processing and single focus processing in the chip manufacturing method according to the modified example.

An embodiment (embodiment) for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited to the contents described in the following embodiments. In addition, the components described below include those that can be easily assumed by those skilled in the art and those that are substantially the same. Further, the configurations described below can be combined as appropriate. In addition, various omissions, substitutions or changes of the configuration can be made without departing from the gist of the present invention.

[Embodiment]
FIG. 1 is a perspective view of a wafer to be processed in the chip manufacturing method according to the embodiment. FIG. 2 is a flowchart showing a flow of a chip manufacturing method according to an embodiment.

The method for manufacturing chips according to the embodiment is a method for manufacturing a plurality of chips 12 by dividing the wafer 10 shown in FIG. The wafer 10 which is a work piece of the chip manufacturing method is a disk-shaped semiconductor wafer or an optical device wafer having a substrate 14 such as silicon, sapphire, and gallium arsenide.

As shown in FIG. 1, the wafer 10 has a plurality of scheduled division lines 20 set on the surface 16 of the substrate 14 in a grid pattern, and a device 22 partitioned by the scheduled division lines 20. The device 22 includes a functional layer 24 in a region partitioned by a planned division line 20 on the surface 16 side. The device 22 is, for example, an integrated circuit such as an IC (Integrated Circuit) or an LSI (Large Scale Integration), a CCD (Charge Coupled Device), or a CMOS (Complementary Metal Oxide Sensor) such as a CMOS sensor.

In the embodiment, the wafer 10 is divided into individual devices 22 along the planned division line 20 and manufactured on the chip 12. The chip 12 includes a part of the substrate 14 and a device 22 on the substrate 14.

In the chip manufacturing method according to the embodiment, wafers 10 which are workpieces having different thicknesses are processed under the same processing conditions to manufacture chips 12. As shown in FIG. 2, the method for manufacturing a chip includes a back surface grinding step ST1, a machined groove forming step ST2, and a modified layer forming step ST3. In the following description, it is described that the operator operates each processing device, but the work may be performed automatically by using an automatic processing device or a transfer device. In the following description, the X-axis direction is one direction in the horizontal plane. The Y-axis direction is a direction that intersects the X-axis direction in the horizontal plane. The Z-axis direction is a direction that intersects the X-axis direction and the Y-axis direction.

(Backside grinding step)
FIG. 3 is a perspective view showing a back surface grinding step of the chip manufacturing method shown in FIG. The back surface grinding step ST1 is a step in which the wafer 10 is ground from the back surface 18 by the grinding unit 50 to be thinned to a predetermined thickness.

In the back surface grinding step ST1, the operator sucks and holds the surface 16 of the wafer 10 on the holding surface 62 of the chuck table 60. At this time, the operator preferably attaches a back grind tape to the surface 16 of the wafer 10 in order to protect the functional layer 24 of the substrate 14 from foreign matter.

The operator rotates the chuck table 60 around the axis 64 and the grinding wheel 52 of the grinding unit 50 around the axis 54. The operator brings the grinding wheel 56 of the grinding wheel 52 closer to the chuck table 60 at a predetermined feed rate while supplying the grinding water. When the grinding wheel 56 comes into contact with the back surface 18 of the wafer 10, the grinding wheel 56 grinds the back surface 18 side of the wafer 10. When the wafer 10 is thinned to a predetermined thickness by the grinding unit 50 in the back surface grinding step ST1, the operator releases the suction holding by the chuck table 60 and shifts to the machining groove forming step ST2. In the embodiment, when a plurality of wafers 10 are ground in the back surface grinding step ST1, it is assumed that a thickness variation 32 (see FIG. 7 described later) occurs for each wafer 10.

(Machining groove formation step)
FIG. 4 is a perspective view showing a machined groove forming step of the chip manufacturing method shown in FIG. The machined groove forming step ST2 is a step of irradiating a laser beam 70 having a wavelength capable of absorbing the functional layer 24 from the surface 16 side of the wafer 10 along the scheduled division line 20 to form the machined groove 26.

In the machined groove forming step ST2, the operator can attach the dicing tape 42 to which the ring-shaped frame 40 is attached to the back surface 18 of the wafer 10 in order to protect the functional layer 24 of the substrate 14 from foreign matter. preferable. The dicing tape 42 includes a base material layer made of a synthetic resin having elasticity and an adhesive layer made of a synthetic resin laminated on the base material layer and having elasticity and adhesiveness.

The operator places the back surface 18 of the wafer 10 on the holding surface of the chuck table 80. The operator sucks and holds the back surface 18 of the wafer 10 on the holding surface of the chuck table 80 via the dicing tape 42.

The operator uses the image pickup unit 72 to image the surface 16 of the wafer 10. The operator detects the scheduled division line 20 from the captured image captured by the imaging unit 72. The operator aligns the scheduled division line 20 so that the longitudinal direction is parallel to the predetermined direction. The predetermined directions are the X-axis direction and the Y-axis direction in the embodiment. The operator aligns the laser beam irradiation unit 76 and the wafer 10 so that the focusing point 74 of the laser beam 70 coincides with the scheduled division line 20.

The operator irradiates the functional layer 24 with the laser beam 70 having an absorbable wavelength while moving the laser beam irradiation unit 76 relative to the chuck table 80. As a result, the operator forms a processing groove 26 along the planned division line 20 on the surface 16 side of the wafer 10. The depth of the machined groove 26 is larger than the thickness of the functional layer 24. When the worker forms the machined grooves 26 in all the scheduled division lines 20 in the machined groove forming step ST2, the operator releases the suction holding by the chuck table 80 and shifts to the modified layer forming step ST3.

(Modified layer formation step)
FIG. 5 is a perspective view showing a modified layer forming step of the chip manufacturing method shown in FIG. FIG. 6 is a cross-sectional view showing a modified layer forming step of the chip manufacturing method shown in FIG. In the modified layer forming step ST3, after the processing groove forming step ST2, a laser beam 90 having a wavelength that is transparent to the wafer 10 is irradiated from the back surface 18 side of the wafer 10 along the scheduled division line 20, and the division starting point. This is a step of forming the modified layer 28.

The modified layer 28 means a region in which the density, refractive index, mechanical strength and other physical properties are different from those of the surroundings. The modified layer 28 is, for example, a melt processing region, a crack region, a dielectric breakdown region, a refractive index change region, a region in which these regions coexist, and the like. In the embodiment, the modified layer 28 is formed at a position at a predetermined depth 30 from the back surface 18 of the wafer 10. The predetermined depth 30 is constant over the entire length of the planned division line 20. The modified layer 28 has lower mechanical strength and the like than other parts of the wafer 10.

In the modified layer forming step ST3, the operator turns over the wafer 10 supported by the frame 40 and the dicing tape 42, and places the surface 16 of the wafer 10 on the holding surface 102 of the chuck table 100. The operator sucks and holds the surface 16 of the wafer 10 on the holding surface 102 of the chuck table 100. The dicing tape 42 may be omitted. At this time, the operator preferably attaches a back grind tape to the surface 16 of the wafer 10 in order to protect the functional layer 24 of the substrate 14 from foreign matter.

The operator images the wafer 10 with the image pickup unit 92. The operator detects the scheduled division line 20 from the captured image captured by the imaging unit 92. The operator aligns the laser beam irradiation unit 96 and the wafer 10 so that the focusing point 94 of the laser beam 90 coincides with the predetermined depth 30 on the scheduled division line 20.

The operator irradiates the scheduled division line 20 with the laser beam 90 having a wavelength having transparency while moving the laser beam irradiation unit 96 relative to the chuck table 100. Since the laser beam 90 is a laser beam 90 having a wavelength that is transparent to the wafer 10, the modified layer 28 is formed at a position at a predetermined depth 30 from the back surface 18 of the wafer 10.

(Multifocal formation step)
The modified layer forming step ST3 includes a multifocal forming step ST4. FIG. 7 is a cross-sectional view of a work piece subjected to multifocal processing in the method for manufacturing a chip according to an embodiment. In the multifocal formation step ST4, the laser beam 90 is focused by using the multifocal forming means so that the thickness variation 32 for each wafer 10 can be absorbed, and a plurality of focusing points 94 are formed in the thickness direction of the wafer 10. It is a step to process like this.

The laser beam irradiation unit 96 includes a multifocal forming means. The laser beam irradiation unit 96 including the multifocal forming means includes, for example, a laser light source, a collimating lens, a polarization control element, a prism mirror, and a spatial optical phase modulator.

The laser light source emits divergent light with linearly polarized light. The collimating lens converts the divergent light emitted from the laser light source into parallel light. The polarization control element changes the linear polarization direction of the parallel light incident from the collimated lens with respect to the optical axis. The laser beam output from the polarization control element is incident on the spatial optical phase modulator via the prism mirror.

The spatial optical phase modulator performs phase modulation of the incident laser light. In the embodiment, the spatial optical phase modulator is an LCOS (Liquid Crystal On Silicon) manufactured by Hamamatsu Photonics Co., Ltd. The spatial optical phase modulator performs spatial phase modulation of the incident laser light. The spatial optical phase modulator uses diffraction to split the incident laser light into a plurality of laser lights. The spatial optical phase modulator collects the branched laser light at an arbitrary position.

After detecting the planned division line 20 from the captured image captured by the imaging unit 92, the operator sets a plurality of focusing points 94 in the thickness direction of the wafer 10 of the scheduled division line 20 in the multifocal formation step ST4. A multifocal forming means is set in. The thickness direction of the wafer 10 is the Z-axis direction in the embodiment. As described above, it is assumed that the thickness variation 32 of each of the plurality of wafers 10 is generated by the grinding process by the back surface grinding step ST1. The operator sets the interfocal distance and the number of focal points with reference to the thickest wafer 10 among the plurality of wafers 10. The operator aligns the position of the condensing point 94 closest to the back surface 18 in the thickness direction of the wafer 10 with reference to the back surface 18.

The operator irradiates the scheduled division line 20 with the laser beam 90 having a wavelength having transparency while moving the laser beam irradiation unit 96 relative to the chuck table 100. At this time, the laser beam 90 focuses on a plurality of focusing points 94 arranged in the thickness direction of the wafer 10 at almost the same time. Since the laser beam 90 is a laser beam 90 having a wavelength that is transparent to the wafer 10, the modified layer 28 is formed at the focusing point 94 inside the wafer 10.

When the modified layer 28 is formed on all the planned division lines 20 in the modified layer forming step ST3 including the multifocal forming step ST4, the operator releases the suction holding by the chuck table 100. After the modified layer forming step ST3, the operator divides the wafer 10 into individual devices 22 along the planned division line 20 to manufacture the chip 12. The operator applies an external force to the wafer 10 by, for example, expanding the dicing tape 42. The wafer 10 is divided along the planned division line 20 starting from the modified layer 28.

As described above, the method for manufacturing a chip according to the embodiment is when a laser beam 90 having a wavelength that is transparent to the wafer 10 is irradiated along the scheduled division line 20 to form the modified layer 28. , The multifocal forming means is used to process the wafer 10 so as to form a plurality of focusing points 94 in the thickness direction.

As a result, when processing the wafer 10 having the thickness variation 32, a plurality of focusing points 94 of the laser beam 90 can be formed in accordance with the assumed thickest wafer 10. By forming a plurality of focusing points 94 of the laser beam 90 according to the assumed thickest wafer 10, even if the wafers 10 having different thicknesses are processed under the same conditions, no processing defect occurs. The chip 12 can be manufactured. Further, the processing time can be shortened by using the multifocal processing that condenses light to different thicknesses almost at the same time. When the thickness of the wafer 10 is thin, the condensing point 94 protrudes from the wafer 10, but the functional layer 24 on the surface 16 side is removed in the machined groove forming step ST2, so that the influence on the device 22 can be suppressed. Can be done. Further, in the machined groove forming step ST2, the machined groove 26 formed by the laser beam 70 has irregularities on the groove bottom, so that the laser beam 90 absorbs or reflects on the groove bottom of the machined groove 26. As a result, damage to the chuck table 100 can be suppressed.

[Modification example]
FIG. 8 is a flowchart showing the flow of the modified layer forming step in the chip manufacturing method according to the modified example. FIG. 9 is a cross-sectional view of a work piece that has undergone multifocal processing and single focus processing in the chip manufacturing method according to the modified example. The modified layer forming step ST3 includes a multifocal forming step ST4 and a single focal point forming step ST5, as shown in FIG.

The modified example differs from the embodiment in that the modified layer 28 is formed by the multifocal formation step ST4 and the single focus formation step ST5. In the modified example, the modified layer 28 includes a modified layer 34 by multifocal processing and a modified layer 36 by single focus processing. The multifocal formation step ST4 is a step of forming a modified layer 34 by multifocal processing on about half of the surface 16 side of the wafer 10 in the thickness direction. The single focus forming step ST5 is a step of forming a plurality of modified layers 36 by single focus processing on about half of the back surface 18 side in the thickness direction of the wafer 10.

In the multifocal formation step ST4 according to the modified example, the operator sets the multifocal forming means so that a plurality of focusing points 94 are formed on about half of the surface 16 side of the wafer 10 in the thickness direction of the planned division line 20. To do. The operator sets the interfocal distance and the number of focal points with reference to the thickest wafer 10 among the plurality of wafers 10. The operator aligns the position of the condensing point 94 closest to the back surface 18 in the thickness direction of the wafer 10 with reference to the back surface 18.

The operator irradiates the scheduled division line 20 with the laser beam 90 having a wavelength having transparency while moving the laser beam irradiation unit 96 relative to the chuck table 100. At this time, the laser beam 90 focuses on a plurality of focusing points 94 arranged in the thickness direction of the wafer 10 at almost the same time. Since the laser beam 90 is a laser beam 90 having a wavelength that is transparent to the wafer 10, a modified layer 34 is formed at a condensing point 94 inside the wafer 10 by multifocal processing. When the operator forms the modified layer 34 by the multifocal processing on all the planned division lines 20 in the multifocal formation step ST4, the operator shifts to the single focus forming step ST5.

In the single focus forming step ST5, the operator sets the laser beam irradiation unit 96 to irradiate the single focus laser beam 90. The operator positions the laser beam irradiation unit 96 so that the condensing point 94 is formed on the back surface 18 side of the modified layer 34 by the multifocal processing on the back surface 18 side in the thickness direction of the wafer 10 of the planned division line 20. Match.

The operator irradiates the scheduled division line 20 with a pulsed laser beam 90 having a wavelength having a transmittance while moving the laser beam irradiation unit 96 relative to the chuck table 100. The operator irradiates the laser beam 90 a plurality of times in the thickness direction of the wafer 10 to form the modified layer 36 by single focus processing at the internal focusing point 94. When the worker forms the modified layer 36 by the single focus processing on all the scheduled division lines 20 in the single focus formation step ST5, the suction holding by the chuck table 100 is released.

In this way, the modified layer 28 can be formed by multifocal processing and single focal processing. By forming a part of the modified layer 28 by single focus processing, sufficient energy can be input and the partitionability can be improved.

The present invention is not limited to the above embodiment. That is, it can be modified in various ways without departing from the gist of the present invention.

10 Wafer (workpiece)
12 Chip 14 Substrate 16 Front surface 18 Back surface 20 Scheduled division line 22 Device 24 Functional layer 26 Machining groove 28 Modified layer 30 Depth 32 Thickness variation 34 Modified layer by multifocal processing 36 Modified layer by single focus processing 40 Frame 42 Dicing Tape 50 Grinding unit 52 Grinding wheel 54, 64 Axis center 56 Grinding grindstone 60 Chuck table 62 Holding surface 70, 90 Laser beam 72, 92 Imaging unit 74, 94 Condensing point 76, 96 Laser beam irradiation unit 80, 100 Chuck table 102 Holding surface ST1 Back surface grinding step ST2 Machining groove formation step ST3 Modified layer formation step ST4 Multifocal formation step ST5 Single focus formation step

Claims (3)

This is a chip manufacturing method for manufacturing chips by processing workpieces with different thicknesses under the same processing conditions.
The work piece is
It is partitioned by a plurality of scheduled division lines set in a grid pattern, and has a device including a functional layer in the region partitioned by the planned division lines on the surface side.
A processing groove forming step of irradiating a laser beam having a wavelength capable of absorbing the functional layer from the surface side of the workpiece along the planned division line to form a processing groove.
After the processing groove forming step, a laser beam having a wavelength that is transparent to the work piece is irradiated from the back surface side of the work piece along the planned division line to form a modified layer serving as a division start point. The modified layer formation step to be formed and
Including
The modified layer forming step
So that the thickness variation of each work piece can be absorbed
The laser beam is focused using a multifocal forming means and
A method for manufacturing a chip, which comprises a multifocal formation step of processing so as to form a plurality of condensing points in the thickness direction of the workpiece. The method for manufacturing a chip according to claim 1, wherein the thickness variation for each workpiece is caused by grinding the back surface of the workpiece. The method for producing a chip according to claim 1 or 2, wherein the multifocal forming means is an LCOS.

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