precision grinding of polycrystalline diamond scribing wheel...

Precision grinding of polycrystalline diamond scribing wheel for scribing and breaking of monocrystalline wafers

Yusuke Akiyama 1, Mutsumi Okada 1, Hirofumi Suzuki 1, a *, Toshio Fukunishi 2 Yoshiyuki Asai 2, and Kazuma Iizawa 2

1Chubu University, 1200, Matsumoto, Kasugai, Aichi, 487-8501 Japan 2Mitsuboshi Diamond Industrial Co. Ltd., 32-12, Kohroen, Settsu, Osaka, 566-0034 Japan

[email protected]

Keywords: Polycrystalline diamond, Scribing wheel, Constant pressure grinding, Diamond wheel, Scribing and breaking

Abstract. The scribing and breaking process, performed using a scribing wheel made of polycrystalline diamonds (PCD), have been widely employed in the cutting of glass plates for windows, liquid crystal displays, and smartphones. The scribing process under focus herein concerns efficient cutting of semiconductor wafers, such as SiC. To this end, techniques for grinding and polishing of PCD scribing wheels have been developed through experiments and corresponding grinding conditions have been optimized. During experiments, scribing/breaking of monocrystalline wafers was performed, using ground PCD wheels, and subsequently, effects of the wheel shape on the performance characteristics of the scribing/breaking process were evaluated.

1. Introduction

Glass plates, traditionally employed in the manufacturing of window panes, are usually cut via a process known as scribing (scratching) by means of a monocrystalline diamond stylus followed by breaking via application of bending stresses. This is made possible by the high clarity of the cutting surface and the correspondingly high cutting efficiency. Recently, scribing and breaking processes have found applications in the cutting of glass plates used in the manufacture of liquid crystal displays (LCD), plasma displays, and tempered cover glasses for smartphone displays. Highly precise and efficient cutting of large-sized glass plates could be facilitated by developing high precision CNC scribing and breaking machines [1].

Furthermore, the need for precision cutting of large and thin monocrystalline wafers has been rapidly increasing in recent years. Anisotropic and ductile Si crystals are used as semiconductors in the manufacture of integrate circuits (ICs), large scale ICs (LSI) and solar panels. Super-hard sapphire glass (monocrystalline Al2O3) is employed in the design of for light emitting diodes (LEDs) while super hard and brittle monocrystalline SiC is used in the construction of power devices for automobiles and other high-power electric devices. Wafers of these materials are cut via the dicing process by a diamond blade (thin wheel) or laser-cutting techniques.

However, there exist some problems in the conventional dicing and laser-cutting process. In the dicing process employing diamond blades as depicted in Fig. 1, the grinding efficiency is very low, and the kerf loss due to blade thickness is excessive. In addition a residual stress layer is produced by grinding heat, and additional washing and drying processes become indispensable [2, 3]. During the laser-based cutting process, substrate materials are vaporized by the high-power laser beam, as depicted in Fig. 2. The attendant thermal damage causes generation of residual stresses and the kerf loss caused by width of the laser beam is also excessive [4][5].

The proposed study focusses on the scribing process performed by means of a scribing wheel in order to overcome the aforementioned problems. During experiments, the proposed scribing process was employed in the cutting of monocrystalline wafers. Polycrystadiamond (PCD) scribing wheels with optimum cuttingground in trial with a diamond wheel, and the influence of grinding conditions and ground-on a monocrystalline SiC wafer using the ground PCD tool, and its performance was evaluated [6]. Figure 1. Schematic of dicing process

2. Scribing and breaking process

Fig. 3 depicts a schematic of the scribing and breaking process. During scribing, the substrate is scratched by means of a rotating scribing wheel. In this process, the "scratch" is formed via application of a load onto the substrate surface in contact witcleaving process, the initially generated scratch progresses deep into the substrate structure under a bending stress, and the substrate is, therefore, cleaved [7Scribing wheels, performed in this study. PCD comprises diamond abrasives sintered in the presence of alloy metals, such as cobalt. It is difficult to process, and compared to singlepresents great difficulty to process difficulty when reducing its surface roughness and improving edge accuracy [10]. It is considered that the chipping ratio, edge accuracy and surface roughness on ground scribing wheels greatly influence the scribin

Substrate

Coolant

Scratch

The proposed study focusses on the scribing process performed by means of a scribing wheel in order to overcome the aforementioned problems. During experiments, the proposed scribing process was employed in the cutting of monocrystalline wafers. Polycrystadiamond (PCD) scribing wheels with optimum cuttingground in trial with a diamond wheel, and the influence of grinding conditions and

-wheel characteristics was evaluated. Furthermore, the scribing process wason a monocrystalline SiC wafer using the ground PCD tool, and its performance was evaluated

Figure 1. Schematic of dicing processemploying a diamond blade

2. Scribing and breaking processFig. 3 depicts a schematic of the scribing and breaking process. During scribing, the

substrate is scratched by means of a rotating scribing wheel. In this process, the "scratch" is formed via application of a load onto the substrate surface in contact witcleaving process, the initially generated scratch progresses deep into the substrate structure under a bending stress, and the substrate is, therefore, cleaved [7Scribing wheels, exclusively made of PCD, as shown in Fig. 4, were used in the experiments performed in this study. PCD comprises diamond abrasives sintered in the presence of alloy metals, such as cobalt. It is difficult to process, and compared to singlepresents great difficulty to process difficulty when reducing its surface roughness and improving edge accuracy [10]. It is considered that the chipping ratio, edge accuracy and surface roughness on ground scribing wheels greatly influence the scribin

Figure 4. Schematic and pictorial representation of PCD scribing wheel

Substrate

Dicing blade

Coolant

Substrate

Scratch


wheel characteristics was evaluated. Furthermore, the scribing process wason a monocrystalline SiC wafer using the ground PCD tool, and its performance was evaluated

Figure 1. Schematic of dicing processemploying a diamond blade

Figure 3. Schematic of scribing and breaking process

2. Scribing and breaking processFig. 3 depicts a schematic of the scribing and breaking process. During scribing, the

substrate is scratched by means of a rotating scribing wheel. In this process, the "scratch" is formed via application of a load onto the substrate surface in contact witcleaving process, the initially generated scratch progresses deep into the substrate structure under a bending stress, and the substrate is, therefore, cleaved [7

exclusively made of PCD, as shown in Fig. 4, were used in the experiments performed in this study. PCD comprises diamond abrasives sintered in the presence of alloy metals, such as cobalt. It is difficult to process, and compared to singlepresents great difficulty to process difficulty when reducing its surface roughness and improving edge accuracy [10]. It is considered that the chipping ratio, edge accuracy and surface roughness on ground scribing wheels greatly influence the scribin


Dicing blade

Residual stress

(a) Scribing

100°

Φ0.8



Figure 1. Schematic of dicing process employing a diamond blade


2. Scribing and breaking process Fig. 3 depicts a schematic of the scribing and breaking process. During scribing, the

substrate is scratched by means of a rotating scribing wheel. In this process, the "scratch" is formed via application of a load onto the substrate surface in contact witcleaving process, the initially generated scratch progresses deep into the substrate structure under a bending stress, and the substrate is, therefore, cleaved [7



Kerf loss

Residual stress

Bond

Substrate

(a) Scribing

Scribing Wheel

Φ2

0.65 mm



Figure 2.


Fig. 3 depicts a schematic of the scribing and breaking process. During scribing, the substrate is scratched by means of a rotating scribing wheel. In this process, the "scratch" is formed via application of a load onto the substrate surface in contact witcleaving process, the initially generated scratch progresses deep into the substrate structure under a bending stress, and the substrate is, therefore, cleaved [7



loss

Diamond abrasive

Bond

Substrate

The proposed study focusses on the scribing process performed by means of a scribing wheel in order to overcome the aforementioned problems. During experiments, the proposed scribing process was employed in the cutting of monocrystalline wafers. Polycrystadiamond (PCD) scribing wheels with optimum cutting-edge some cutting edge radius were ground in trial with a diamond wheel, and the influence of grinding conditions and


Figure 2. Schematic of laser employing high


Fig. 3 depicts a schematic of the scribing and breaking process. During scribing, the substrate is scratched by means of a rotating scribing wheel. In this process, the "scratch" is formed via application of a load onto the substrate surface in contact witcleaving process, the initially generated scratch progresses deep into the substrate structure under a bending stress, and the substrate is, therefore, cleaved [7



Diamond

Substrate

Substrate

Scratch

(b) After scribing

5 mm

The proposed study focusses on the scribing process performed by means of a scribing wheel in order to overcome the aforementioned problems. During experiments, the proposed scribing process was employed in the cutting of monocrystalline wafers. Polycrysta

edge some cutting edge radius were ground in trial with a diamond wheel, and the influence of grinding conditions and


Schematic of laseremploying high


Fig. 3 depicts a schematic of the scribing and breaking process. During scribing, the substrate is scratched by means of a rotating scribing wheel. In this process, the "scratch" is formed via application of a load onto the substrate surface in contact with the wheel. During the cleaving process, the initially generated scratch progresses deep into the substrate structure under a bending stress, and the substrate is, therefore, cleaved [7-9].

exclusively made of PCD, as shown in Fig. 4, were used in the experiments performed in this study. PCD comprises diamond abrasives sintered in the presence of alloy metals, such as cobalt. It is difficult to process, and compared to single-crystalline diampresents great difficulty to process difficulty when reducing its surface roughness and improving edge accuracy [10]. It is considered that the chipping ratio, edge accuracy and surface roughness on ground scribing wheels greatly influence the scribing performance.


Laser beam

Substrate

Residual

Substrate

Substrate

Scratch

After scribing

(c) Br

The proposed study focusses on the scribing process performed by means of a scribing wheel in order to overcome the aforementioned problems. During experiments, the proposed scribing process was employed in the cutting of monocrystalline wafers. Polycrysta


wheel characteristics was evaluated. Furthermore, the scribing process was performed on a monocrystalline SiC wafer using the ground PCD tool, and its performance was evaluated

Schematic of laser-cutting processemploying high-power laser beam

Fig. 3 depicts a schematic of the scribing and breaking process. During scribing, the substrate is scratched by means of a rotating scribing wheel. In this process, the "scratch" is

h the wheel. During the cleaving process, the initially generated scratch progresses deep into the substrate structure

exclusively made of PCD, as shown in Fig. 4, were used in the experiments performed in this study. PCD comprises diamond abrasives sintered in the presence of alloy

crystalline diampresents great difficulty to process difficulty when reducing its surface roughness and improving edge accuracy [10]. It is considered that the chipping ratio, edge accuracy and

g performance.


Kerf loss

Residual stress

Substrate Indenter

Bending stress

(c) Breaking

The proposed study focusses on the scribing process performed by means of a scribing wheel in order to overcome the aforementioned problems. During experiments, the proposed scribing process was employed in the cutting of monocrystalline wafers. Polycrystalline


performed on a monocrystalline SiC wafer using the ground PCD tool, and its performance was evaluated

cutting process power laser beam

Fig. 3 depicts a schematic of the scribing and breaking process. During scribing, the substrate is scratched by means of a rotating scribing wheel. In this process, the "scratch" is

h the wheel. During the cleaving process, the initially generated scratch progresses deep into the substrate structure

exclusively made of PCD, as shown in Fig. 4, were used in the experiments performed in this study. PCD comprises diamond abrasives sintered in the presence of alloy

crystalline diamond, presents great difficulty to process difficulty when reducing its surface roughness and improving edge accuracy [10]. It is considered that the chipping ratio, edge accuracy and

g performance.

Kerf loss

Laser beam

Indenter

Bending stress

aking

Figure 5. Schematic and pictorial representation of the PCD-wheel grinding setup

3. Experimental setup 3.1. Grinding of PCD scribing wheel

Fig.5 depicts schematic and pictorial representations of the setup used during grinding operations performed on the PCD scribing wheel. The PCD wheel (workpiece) was attached to the grinding setup by means of a stainless steel pin, and held in contact with the rotating diamond wheel. In order to prevent glazing and clogging of the diamond wheel, in-process truing and dressing were performed on the machine. For this purpose, a stick of white alumina WA#4000 was used as the truer. The PCD wheel was ground by means of the rotating diamond wheel, and the wheel surface, at the same time, was polished with the loose abrasives dropped off the truer/dresser. This may, therefore, be thought of as a hybrid grinding and polishing process.

Grinding conditions are summarized in Table 1. A cup type of diamond wheel was used as the grinding wheel with Φ200 mm diameter and the grain size was changed to # 3000, #5000 and #10000. The PCD scribing wheel, shaped similar to an abacus bead, was attached to the pin

Table 1 Grinding conditions Grinding wheel Grain size Shape

Outer diameter Rotation Circumferential velocity

Diamond wheel #3000, #5000, #10000 Cup type Φ200 mm 450 mm-1

277 m/min Truer / Dresser Feed rate

WA#4000 1.0 µm/s

Coolant Water base coolant Workpiece Out diameter Cutting edge angle Rotation Circumferential velocity

PCD (Poly crystalline diamond) Φ2 mm 100 ° 900 min-1

5.65 m/min Grinding angle against scribing wheel ridgeline

-90，-67.5，-45，-22.50，15，30，45，

60，75，90 ° Infeed depth of cut

Feed rate 15 µm×2 times

0.2 µm/s

Cup-type diamond wheel

PCD wheel(Workpiec

e)

Coolant

Al 2O3 dresser

Wheel spindle

40

Cup-type diamond wheel

PCD wheel

of a rotating workpiece spindle. Diameter of the PCD wheel was Φ2 mm, and the included cutting-edge angle was 100° as shown in Fig. 4.

3.2. Measurement method of the PCD scribing wheel

The surface of the PCD scribing wheel, ground as described above, was measured and evaluated by means of a non-contact laser probe scanner. A blue laser of short wavelength (λ=0.473 µm) was used in order to reduce the laser spot diameter, thereby improving its resolution. The spot diameter was reduced to 0.25 µm. Shape accuracy and surface roughness of the 40 degrees tilted outer surface and ridge line were measured, as depicted in Fig. 6.

Figure 6. Measurements performed on the PCD scribing setup 3.3. Scribing set-up and corresponding scribing method

In order to evaluate the PCD scribing wheel, monocrystalline wafers of SiC were scribed using the ground PCD wheel. Fig. 7 depicts the scribing set-up used during scribing experiments. The scribing wheel was made to rotate on the substrate by applying a constant load. In the scribing test, wafers having a thickness of 0.3 mm were vacuum-chucked onto the stage and scribed manually. Residual stresses are often generated during the scribing process, since scratches are formed along with plastic deformation of cracks that appear on substrates under the applied scribing load. These residual stresses were estimated by measuring phase differences on the scribed wafer by means of birefringence equipment.

Figure 7. Schematic and pictorial representation of the scribing setup 4. Experimental results 4.1 Results for grinding of PCD scribing wheel

The PCD scribing wheel was ground using a cup-type diamond grinding wheel, and the effects of grinding conditions on surface quality of the PCD wheel were tested.

(a) Effect of grinding direction The grinding angle θ with respect to the ridgeline was varied within the range from -90 °

- 90 °, as depicted in Fig. 9. The grain size during grinding was #3000. Fig. 8 depicts SEM

PCD wheel

Pin jig

Objective lens

Load

Wafer

Vacuum chuck

Stage

Scribing wheel

Load

Scribing wheel Wafer Vacuum

chuck

images of the ground scribing wheel on the ridgeline. For grinding angles between 45 chipping was observed on the ridgelno chipping was observed. In order to quantitatively evaluate the edge sharpness of the PCD scribing wheel, the following chipping ratio was introduced. A profile on the ridgeline was scanned usan edge measuring more than 1 the total length of the chipping, lc to the ridgeline length, L. rc = l

(a) Chipping ratio

Fig. 9(a) depicts variations in the measured chipping ratio on the ridgeline of the cutting

edge. Many chippings were observed at the grinding angles of 30 ° chippings were observed for grinding angles of the order of with that demonstrated by SEM images of the ground PCD wheel. Fig. 9(b) depicts variations in the measured surface roughness along the ridgeline

0

0.2

0.4

-90

Ch

ipp

ing

ra

tio

%

images of the ground scribing wheel on the ridgeline. For grinding angles between 45 chipping was observed on the ridgelno chipping was observed. In order to quantitatively evaluate the edge sharpness of the PCD scribing wheel, the following chipping ratio was introduced. A profile on the ridgeline was scanned using a nonan edge measuring more than 1 the total length of the chipping, lc to the ridgeline length, L.

rc = lc / L

Figure 8.

hipping ratio Figure 9. Effect of grinding angle against the ridgeline of the scribing wheel

Fig. 9(a) depicts variations in the measured chipping ratio on the ridgeline of the cutting edge. Many chippings were observed at the grinding angles of 30 ° chippings were observed for grinding angles of the order of with that demonstrated by SEM images of the ground PCD wheel. Fig. 9(b) depicts variations in the measured surface roughness along the ridgeline

Θ=-

Θ=0°

Θ=60°

-90 -45

Grinding angle

images of the ground scribing wheel on the ridgeline. For grinding angles between 45 chipping was observed on the ridgelno chipping was observed. In order to quantitatively evaluate the edge sharpness of the PCD scribing wheel, the following chipping ratio was introduced. A profile on the ridgeline was

ing a non-contact laser probe scanner, and chipping was defined as a micro break of an edge measuring more than 1 the total length of the chipping, lc to the ridgeline length, L.

c / L

Figure 8. SEM images of the ground scribing wheel on the ridgeline

hipping ratio variation (b) Figure 9. Effect of grinding angle against the ridgeline of the scribing wheel


-90° 10 µm

=0°

=60°

0 45

Grinding angle θ °

0

1

2

-90

Su

rfac

e ro

ug

hn

ess

µm

R

z

images of the ground scribing wheel on the ridgeline. For grinding angles between 45 chipping was observed on the ridgeline. On the other hand, grinding angle of no chipping was observed. In order to quantitatively evaluate the edge sharpness of the PCD scribing wheel, the following chipping ratio was introduced. A profile on the ridgeline was

contact laser probe scanner, and chipping was defined as a micro break of an edge measuring more than 1 µm in size. The chipping ratio, rc was calculated as the ratio of the total length of the chipping, lc to the ridgeline length, L.

c / L

SEM images of the ground scribing wheel on the ridgeline

(b) Surface roughnessFigure 9. Effect of grinding angle against the ridgeline of the scribing wheel


90° Θ=-67.5°

=0° Θ=15°

=60° Θ=75°

90

45

0

-

Grinding angle,

-45 0

Grinding angle

images of the ground scribing wheel on the ridgeline. For grinding angles between 45 ine. On the other hand, grinding angle of

no chipping was observed. In order to quantitatively evaluate the edge sharpness of the PCD scribing wheel, the following chipping ratio was introduced. A profile on the ridgeline was

contact laser probe scanner, and chipping was defined as a micro break of m in size. The chipping ratio, rc was calculated as the ratio of

the total length of the chipping, lc to the ridgeline length, L. c / L


urface roughness vFigure 9. Effect of grinding angle against the ridgeline of the scribing wheel


67.5°

=15°

=75°

9045

0°

135°

-90° -135-45°

Grinding angle,

45 90





the total length of the chipping, lc to the ridgeline length, L. c / L


variation (c) Figure 9. Effect of grinding angle against the ridgeline of the scribing wheel

Fig. 9(a) depicts variations in the measured chipping ratio on the ridgeline of the cutting edge. Many chippings were observed at the grinding angles of 30 ° chippings were observed for grinding angles of the order of -90 ° with that demonstrated by SEM images of the ground PCD wheel. Fig. 9(b) depicts variations in the measured surface roughness along the ridgeline. Surface roughness corresponding to

Θ=-45°

=15° Θ=30°

=75° Θ=90°

135

135° PCD wheel

Ridgelin

Grinding angle, Θ





(c) Wheel edge radius Figure 9. Effect of grinding angle against the ridgeline of the scribing wheel

Fig. 9(a) depicts variations in the measured chipping ratio on the ridgeline of the cutting edge. Many chippings were observed at the grinding angles of 30 ° - 75 °, a

90 ° - 15°. This trend coincides with that demonstrated by SEM images of the ground PCD wheel. Fig. 9(b) depicts variations

. Surface roughness corresponding to

45° Θ=

=30° Θ=45°

=90° Θ: Grinding angle

0

1

2

-90 -45

Ed

ge

ra

diu

s R

μm

Grinding angle

PCD wheel

Ridgelin

images of the ground scribing wheel on the ridgeline. For grinding angles between 45 ine. On the other hand, grinding angle of -90°, -45°, and 0°,




heel edge radius vFigure 9. Effect of grinding angle against the ridgeline of the scribing wheel

Fig. 9(a) depicts variations in the measured chipping ratio on the ridgeline of the cutting 75 °, and relatively few

15°. This trend coincides with that demonstrated by SEM images of the ground PCD wheel. Fig. 9(b) depicts variations


=-22.5°

=45°

: Grinding angle

-45 0


images of the ground scribing wheel on the ridgeline. For grinding angles between 45 - 90°, 45°, and 0°,



(1)

variation Figure 9. Effect of grinding angle against the ridgeline of the scribing wheel

Fig. 9(a) depicts variations in the measured chipping ratio on the ridgeline of the cutting nd relatively few

15°. This trend coincides with that demonstrated by SEM images of the ground PCD wheel. Fig. 9(b) depicts variations


45 90

°

negative grinding angles was smaller compared to that corresponding to positive angles. Fig. 9(c) depicts variations of measured edge radius along the ridgeline. Edge radius measured its minimum value when grinding angle was set to zero. It can, therefore, be inferred from the above results that it is most suitable to grind the PCD scribing wheel along its ridgeline.

(b) Effect of grinding wheel grain size To investigate the effect of grinding wheel grain size, the grinding angle, Θ was fixed at zero, and grain size of the grinding wheel was varied from #3000 to #10000. Corresponding grinding conditions are summarized in Table 2. Fig. 10(a) and 10(b), respectively, depict variations in the chipping ratio and surface roughness with wheel grain size. Grinding experiments demonstrate that the chipping ratio and surface roughness of the scribing wheel edge were smaller corresponding to smaller grain size of the wheel.

Table 2 Grinding conditions

(a) Variation of chipping ratio (b) Variation of surface roughness Figure 10. Effect of grain size of the grinding wheel

Figure 11. Effect of hybrid machining using loose diamond abrasives

Wheel

Outer diameter (mm) Rotation (mm

-1)

Speed (m/min)

SD 3000

Φ200

450

277

SD 5000

Φ150

600

283

SD 10000

Φ150

600

283

Workpiece

Outer diameter (mm)

Rotation (mm-1

)

Speed (m/min)

PCD (Polycrystalline diamond)

Φ2

900

5.65

Grinding angle, θ (°) 0

0

1

2

0 2500 5000 7500 10000

Su

rfa

ce r

ou

gh

ness

µm

Rz

Grain size #

0

0.04

0.08

0 2500 5000 7500 10000

Ch

ipp

ing

ra

tio

%

Grai size #

0

0.04

0.08

0.12

0.16

Ch

ipp

ing

ra

tio

％

Grinding

Grinding +

Polishing

0

0.5

1

1.5

Su

rfa

ce r

ou

gh

ne

ssµ

m R

z

Grinding

Grinding +

Polishing

0

0.5

1

1.5

Ed

ge

ra

diu

s R

µm

Grinding +

Polishing

Grinding

(c) Effect of hybrid grinding and polishing processes During the grinding experiment, the scribing wheel was ground with a diamond wheel

having a grain size of #3000 while adding loose abrasives in order to reduce the chipping ratio, surface roughness and improve machining efficiency. As a polishing abrasive, diamond abrasive of 0-3 µm in abrasive size was used. Fig. 11 depicts the effect of this hybrid machining using loose diamond abrasives. The chipping ratio and surface roughness of the wheel ridgeline were observed to have been reduced under hybrid machining while the edge radius was found to have slightly increased.

4.2 Scribing results obtained using the scribing wheel

A scribing test was performed using PCD scribing wheels ground with three grain sizes of the wheel, #3000, #5000 and #10000 of the diamond wheel as depicted in Fig. 10. Monocrystalline SiC wafers (0001) (Si face) were scribed under varying scribing loads. Scribing conditions are summarized in Table 3. Monocrystalline wafers were vacuum chucked, and the scribing wheel was scanned on the wafer with loads being applied via air pressure.

Nomarski micrographs of the scribed SiC wafer are depicted in Fig. 12. With increase in scribing load and coarsening of the grinding wheel grain size, the scratch was observed to have become clearer. Fig.13 depicts changes in scratch depth, measured using a non-contact type of laser probe scanner. In both crystal orientations, the scratch was observed to have become clear. With increase in scribing load and coarsening of the grinding wheel grain size, the depth of scratch was found to have increased.

Table3. Scribing conditions

Scribing wheel

Cutting edge angle

Grinding wheel

PCD (Poly crystalline diamond)

100°

#3000, #5000, #10000

Workpiece

Thickness

Monocrystalline SiC wafer (0001) Si face

0.33 mm

Load 1.2, 1.7，2.4，3.0 N (by Air pressure)

Stage Vacuum chuck

Figure 12. Nomarski micrographs for scribed SiC wafer

10µm

1.2 N

1.7 N

2.4 N

3.0 N

1.2 N

1.7 N

2.4 N

3.0 N

1.2 N

1.7 N

2.4 N

3.0 N

1.2 N

1.7 N

2.4 N

3.0 N

1.2 N

1.7 N

2.4 N

3.0 N

1.2 N

1.7 N

2.4 N

3.0 N

Parallel to OF Cross to OF

#3000

#5000

#10000

Grain size of wheel

Fig. 14 demonstrates changes in surface roughness of the scratches of the scratches on the SiC wafer surface post scribing. The surface roughness was measured and evaluated by means of a nonreduced grain size of the grinding wheel and increased sharpness of the edgwheel. In addition, very little residual stresses were observed.

5. Conclusions

PCD scribing wheels with different grinding angle were developed via grinding, and the cutting edge accuracies of prototype scribing wheels along with corresponding surface roughness, edge radius and chipping ratio were evaluated. Subsequently, monocrystalwafers were scribed and scratched using the prototype PCD scribing wheel, and evaluated. From the grinding and scribing experiments, following results were obtained:

(1) The cutting edge accuracy and surface roughness of the ground PCD tool were sfor the grinding angles of

(2) With decrease in grain size of the grinding wheel, the edge of the scribing wheel was observed to become sharper.

(3) The hybrid grinding and polishing processes were found to be effective in enhancing the precision of PCD scribing wheels.

(4) The scribed surface on the SiC wafer was deep and clear. Also, the residual stresses developed were negligible when the edge of the scribing wheel was sharp.

Acknowledgements

Fig. 14 demonstrates changes in surface roughness of the scratches of the scratches on the wafer surface post scribing. The surface roughness was measured and evaluated by means

of a non-contact laser probe scanner, and tends to be small in both crystal orientations for reduced grain size of the grinding wheel and increased sharpness of the edgwheel. In addition, very little residual stresses were observed.

(a) Parallel to flat orientation (OF)

(a) Parallel to flat orientation (OF) Figure 14.

5. Conclusions PCD scribing wheels with different grinding angle were developed via grinding, and the

cutting edge accuracies of prototype scribing wheels along with corresponding surface roughness, edge radius and chipping ratio were evaluated. Subsequently, monocrystalwafers were scribed and scratched using the prototype PCD scribing wheel, and evaluated. From the grinding and scribing experiments, following results were obtained:

(1) The cutting edge accuracy and surface roughness of the ground PCD tool were sfor the grinding angles of


(3) The hybrid grinding and polishing processes were found to be effective in enhancing the recision of PCD scribing wheels.


Acknowledgements

0.3

0.6

0.9

De

pth

µm

0

0.5

1

1.5

2

Su

rfa

ce r

ou

gh

ne

ss μ

m R

z


contact laser probe scanner, and tends to be small in both crystal orientations for reduced grain size of the grinding wheel and increased sharpness of the edgwheel. In addition, very little residual stresses were observed.

(a) Parallel to flat orientation (OF) Figure 13.

(a) Parallel to flat orientation (OF) Figure 14. Variations in surface roughness of scratch with scribing load


(1) The cutting edge accuracy and surface roughness of the ground PCD tool were sfor the grinding angles of -90




Acknowledgements

0

0.3

0.6

0.9

0 1

#3000#5000

#10000

0

Load



(a) Parallel to flat orientation (OF) Figure 13. Change of scratch depth with scribing load

(a) Parallel to flat orientation (OF) Variations in surface roughness of scratch with scribing load


(1) The cutting edge accuracy and surface roughness of the ground PCD tool were s90 - 0°.

(2) With decrease in grain size of the grinding wheel, the edge of the scribing wheel was



2

Load N

#3000 #5000

#10000

2

N

#3000 #5000

#10000



(a) Parallel to flat orientation (OF) Change of scratch depth with scribing load

(a) Parallel to flat orientation (OF) Variations in surface roughness of scratch with scribing load


(1) The cutting edge accuracy and surface roughness of the ground PCD tool were s


(3) The hybrid grinding and polishing processes were found to be effective in enhancing the


3

Su

rfa

ce r

ou

gh

ne

ssμ

m R

z

4



(b) Normal to flat orientation Change of scratch depth with scribing load

(a) Parallel to flat orientation (OF) (b) Normal to flat orientation Variations in surface roughness of scratch with scribing load






0

0.3

0.6

0.9

0

De

pth

µm

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contact laser probe scanner, and tends to be small in both crystal orientations for reduced grain size of the grinding wheel and increased sharpness of the edg


(b) Normal to flat orientation Variations in surface roughness of scratch with scribing load






1 2

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#3000 #5000

#10000

2

Load N

#3000 #5000

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contact laser probe scanner, and tends to be small in both crystal orientations for reduced grain size of the grinding wheel and increased sharpness of the edge of the scribing


(b) Normal to flat orientation Variations in surface roughness of scratch with scribing load





(4) The scribed surface on the SiC wafer was deep and clear. Also, the residual stresses

3

4

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contact laser probe scanner, and tends to be small in both crystal orientations for e of the scribing

Variations in surface roughness of scratch with scribing load

PCD scribing wheels with different grinding angle were developed via grinding, and the cutting edge accuracies of prototype scribing wheels along with corresponding surface roughness, edge radius and chipping ratio were evaluated. Subsequently, monocrystalline SiC wafers were scribed and scratched using the prototype PCD scribing wheel, and evaluated.

(1) The cutting edge accuracy and surface roughness of the ground PCD tool were superior



(4) The scribed surface on the SiC wafer was deep and clear. Also, the residual stresses

The authors would like to acknowledge the financial support received from the ministry of education, Science and Culture of Japan under the grant-In-Aid for Scientific Research (No.16H04251), and Osawa Scientific Studies Grant Foundation. References [1] Ono T., Tanaka K., (2001) Effective of Scribing Wheel Dimensions on the Cutting of

AMLCD Glass Substrates, Journal of the Society for Information Display, 9(2): 87-94. [2] Brinksmeier E, Mutlugünes Y, Klocke F, Aurich J C, Shore P, Ohmori H (2010)

Ultra-precision Grinding, Annals of the CIRP 59(2): 652-671. [3] Zhou P., Xu S., Wang Z., Yan Y., Kang R., Guo D., (2016) A load identification method for

the grinding damage induced stress (GDIS) distribution in silicon wafers, International Journal of Machine Tools and Manufacture, 107: 1-7.

[4] Tsai H. C., Huang B. W., (2008) Diamond Scribing and Laser Breaking for LCD Glass Substrates, Journal of materials processing technology, 198: 350–358.

[5] Yamamoto K., Hasaka. H. Morita N, and Ohmura E., (2010) Influence of Glass Substrate Thickness in Laser Scribing of Glass, Precision Engineering, 34(1): 55-61.

[6] Suzuki H., Okada M., Asai W., Sumiya H., Harano K., Yamagata Y., Miura K., (2017) Micro Milling Tool Made of Nano-Polycrystalline Diamond for Precision Cutting of SiC, Annals of the CIRP 66(1): 93-96.

[7] Liao S. Y., Yang M. G. Hsu, S. Y., (2010) Vibration Assisted Scribing Process on LCD Glass Substrate, International Journal of Machine Tools & Manufacture, 50: 532–537.

[8] Ono T., (2012) Effect of Scribing Wheel Dimensions on the Cutting of LCD Glass Substrate, Journal of the Society for Information Display, 31(1): 156-159.

[9] Chang K.H., Huang L. J., Sung C. J., Yang R. S., (2010) Newly Designed Glass Scribing Wheel Made of Chemical Vapour Deposition Diamond Film, The American Ceramic Society, 12(1): 4122-4128.

[10] Suzuki, H., Moriwaki, T., Yamamoto, Y., Goto, Y., (2007) Precision Cutting of Aspherical Ceramic Molds with Micro PCD Milling Tool, Annals of the CIRP, 56(1): 131-134.

precision grinding of polycrystalline diamond scribing wheel...

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