Investigation of Laser Ablation of CVD Diamond Film

7/31/2019 Investigation of Laser Ablation of CVD Diamond Film

1/10

1

1

Dept. of Mechanical EngineeringTam-Kang University

Pr ecision Engineering GroupPr ecision Engineering GroupPr ecision Engineering GroupPr ecision Engineering Group 1

C. L. CHAO

Investigation of Laser Ablation of CVD

diamond film

1 Tam-Kang University, 2 Chung-Hwa University,

Taiwan, R.O.C

C.L. Chao1*, W.C. Chou1, K.J. Ma2 and Y.T. Chen2

2



C. L. CHAO

Application of Diamond Films

Applications Surface Requirement

SAW device Polished surface required

X-ray windows, UV to IR

windows, radomes

Polished surface required

Thermal Spreader for laser,

IC


Precision cutting tools Smooth/Polished surface required

MEMS Polished surface required

Biological devices Polished surface required

Wear resistant coating on

die.



2/10

2

3



C. L. CHAO

Comparison of various CVD methods of growing diamond

Method Rate(m/hr) /

Area(cm2)

Adv. Drawbacks

Hot Fi lament

(HFCVD)

0.5~8 / >250 Si mpl e, large

area

Stability,

contamination

Microwave

(MWCVD)

0.1~3 / >6 Quality, Area Expensive, rate

Arc plasma jet

(APJ)

25~ 930 /


3/10

3

5



C. L. CHAO

Comparison of Methods

Processing

Temp.Limit. On

dimension

Shape of

processing

cost of process.

equipment/

running cost

Processing

time

Mechanical

lapping

RT Lapping

Pad

Planar L/H days

Thermo-

chemical

Polishing

HT

>650oC

Heating

Zone

Planar depends Hours

Laser

Smoothing

RT Stage Planar/

non-planar

H/H Hours

RIE/Plasma

Assisted

Polishing

HT

>700oC

Chamber Planar/

non-planar

H/H Hours

6



C. L. CHAO

Mechanical polishing

10hrs

25hrs

30hrs

20hrs


4/10

4

7



C. L. CHAO

diamond

graphite

8



C. L. CHAO

Thermo-mechanically polished CVD Diamond Film


5/10

5

9



C. L. CHAO

Surface morphology of TC-polished CVD diamond film

Polishing Temp. is low, and/or C% of the pad is high

10



C. L. CHAO

Surface morphology of TC-polished CVD diamond film

Polishing Temp. is high, and/or C% of the pad is low


6/10

6

11



C. L. CHAO

Excimer Laser Machining

Facilities: ArF(193nm) lasers (LPX210)

(1)Laser source (2)45Mirror (3)Homogenizer (4)Field Lens (5)Mask

(6)Condenser Lens (7)Stage (8)Fan (9)Gas Handling (10)Optical Table

12



C. L. CHAO

Laser ablated surface

SEM micrographs of the graphitic structure on the surface after ablated by

laser for 8000 shots with a fluence of 2.8 J/cm2 and at a repetition rate of (L)

10Hz and (R) 20Hz.


7/10

7

13



C. L. CHAO

Raman spectra of laser ablated diamond film

9 00 1 00 0 1 10 0 1 20 0 1 30 0 1 40 0 1 50 0 1 60 0 1 70 0Raman shift (cm-1)

0

500

1 0 0 0

1 5 0 0

2 0 0 0

2 5 0 0

Intensity,a.u.

As Grown

9 00 1 00 0 1 10 0 1 20 0 1 30 0 1 40 0 1 50 0 1 6 00 1 70 0

Raman shift (cm-1)

0

500

1000

1500

2000

2500

Intensity,a.u.

Laser Ablated (370mj-5hz-8ks )

1332 diamond peak 1332 diamond peak

Raman: Ar+, 514nm, 2m spot size, 2W

Graphite,

Amorphous

Carbon

Nanocrystalline

diamond

14



C. L. CHAO



8/10

8

15



C. L. CHAO

Excimer laser polished CVD diamond surface(diamond film of 25m thick, repetition rate:10Hz , fluence: 2.9 J/cm2 )

As grown

100 shots 500 shots1000 shots 3000 shots5000 shots 10000 shots

16



C. L. CHAO

Roughness vs Shot Number

0 100 500 1000 3000 5000 1 0000

Shot Number

0.08

0.09

0.1

0.110.12

0.13

0.14

0.15

0.16

0.17

0.18

Ra(um)

Ra vs Shot Number

0 100 500 1000 3000 5000 10000

Shot Number

0.5

1

1.5

2

2.5

3

Rt(um)

Rt vs Shot Number


9/10

9

17



C. L. CHAO

Excimer laser polished CVD diamond surface(diamond film of 25m thick, repetition rate:10Hz , fluence: 2.9 J/cm2 )

5HzRa:0.14m

Rt:2.5m

10HzRa:0.12m

Rt:1.31m

20HzRa:0.11m

Rt:1.37m

18



C. L. CHAO

Excimer laser polished CVD diamond surface(diamond film of 120m thick, fluence: 2.5 J/cm2 )

2Hz,

3000 s hots

As grown4Hz,

3000 shots

6Hz,

3000 shots

10Hz,

3000 shots

8Hz,

3000 shots

10Hz,

5000 shots

10Hz,

4000 shots


10/10

10

19



C. L. CHAO


With KOH

20



C. L. CHAO

Summary

The higher the fluence and/or the laser pulsenumbers, the higher the ablation rate

Graphitization plays an important role in CVDdiamond films material removal

In the case of CVD diamond film of 25mthickness, laser ablation could improve the surfaceroughness from above 0.4m to around 0.1m ina minute, however scanning would be required tocover a large area,

Unless ventilation system is improved, addingKOH makes the laser ablation a rather messyprocess.

Investigation of Laser Ablation of CVD Diamond Film

Documents

Transcript of Investigation of Laser Ablation of CVD Diamond Film