압축잔류응력을 이용한 극미세 DLC 박막의 탄성계수 평가

1. 압축잔류응력을 이용한 극미세 DLC박막의 탄성계수 평가 한국과학기술연구원 조성진, 정진원, 이 광 렬

2. Contents • Introduction to Residual Stress of Thin Films • Industrial Application and Residual Stress of DLC Films • Elastic Modulus Measurement by a Simple Micro-Fabrication

3. Residual Stress of Thin Films • Thin films typically support very high stresses due to the constraint of the substrate to which they are attached • Normally at near failure stress! • Affects the mechanical behaviors of the coating and devices (elastic distortion, plastic deformation, fracture, adhesion) • Origin of the Residual Stress • Any process that changes the in-plane dimension of the film relative to that of the substrate

4. Relative Dimensional Changes

5. Thermal Stress Condition : Difference in thermal expansion coeff. Difference in temperature

6. Epitaxial Strains Condition : Coherency with different lattice parameters

7. Intrinsic Stress (Growth Stress)

8. Relative Dimensional Changes

9. Bending due to Residual Stress DLC Films Deposited by Filtered Vacuum Arc.

10. Measurement of Residual Stress • Assumption • 1-D Treatment of Elastic Equilibrium • Sufficient Adhesion • df << ds • ds << R ds df Curvature (R)

11. Stress Measurement

12. Properties of Solid Carbon

13. 경질박막의 내마모 윤활특성 마모도 마찰계수. DLC WC TiN CrN TiCN 2.0 1.6 1.2 0.8 0.4 (상대비교치) 0.2 0.4 0.6 0.8 1.0

14. Applications of DLC Film

15. Residual Stress DLC Films Deposited by Filtered Vacuum Arc.

16. 1000 Dense Hydro- Carbon Dense Carbon 100 Impact Energy (eV) Polymer Like Carbon 10 Amorphous Carbon (sp2) 1 Plasma Polymers Carbon Source Hydrocarbon Source Deposition Method for DLC Films Ion Source Energy Cold Substrate

17. Intrinsic Stress (Growth Stress)

18. Typical Behavior of Residual Stress of DLC Films ta-C by FVA a-C:H by rf-PACVD

19. Self Delamination of DLC Films • K.-R. Lee et al., Diam. Rel. Mater. 2 (1993) 208. • M.-W. Moon et al., Acta Mater., 50 (2002) 1219.

20. Fn Ft Failure Due to Residual Stress Constant Temperature and Humidifier Motor At 90% R.H.

21. Stress Effect on MEMS Structure 0.45mm thick DLC coating Courtesy of SAIT

22. Key Idea of the Present Method For Isotropic Thin Films

23. Relative Dimensional Changes

24. Preparation of Free Overhang Si Etching (by KOH Solution) Wet Cleaning DLC film Deposition Cleavage along [011] Direction Strain Measurement

25. Preparation of DLC Bridges by Micro Fabrication SiO2 Isotropic Wet Etching Wet Cleaning DLC film Deposition ( on SiO2 ) Strain Estimation DLC Patterning

26. Microstructure of DLC Bridges 150mm C6H6, 10mTorr, -400V, 0.5mm

27. Strain of the Buckled Thin Films (I) Z X 2A0

28. Stain of the Buckled Thin Films (II)

29. Elastic Modulus for Various Ion Energies Nanoindentation t>1.0 ㎛

30. Elastic Modulus of Thin Films • Mechanical properties of thin films are not the same as those of materials having the sample composition in bulk form • High quench rate in deposition process • High defect densities and textures • Non-equilibrium compositions • Confinement of dislocations, craction, etc. in small dimensions

31. Nano-Indentation of Thin Film Substrate

32. Nano-Indentation • Initial unloading is pure elastic. • Sneddon’s elastic contact theory

33. Bulge Test For Isotropic Film

34. Sonic Vibration and Laser-Acoustic Technique Sonic Vibration Laser-Acoustic

35. Freehang and Micro Bridge

36. Advantages of This Method • Simple Method • Completely Exclude the Substrate Effect • Can Be Used for Very Thin Films • The possibility of elastic modulus measurement in very thin film

37. Nano-Indentation of Thin Film Substrate

38. Nano-indentation Results

39. Elastic Modulus for Various Ion Energies Nanoindentation t>1.0 ㎛

40. HDD용 Hard Disk

41. Elastic Modulus of Very Thin Films a-C:H, C6H6 -400V ta-C (Ground) J.-W. Chung et al, Diam.Rel. Mater. 10, 2069 (2001).

42. Residual Compressive Stress & G-peak Position of Raman

43. Biaxial Elastic Modulus 100 166 233 20

44. G-peak Position of Raman 233 166 100 20

45. Si Substrate 233 166 100 Si Substrate 20 Si Substrate Schematic Film Structure J.-W. Chung et al, Diam.Rel. Mater., 11, 1441 (2002).

46. Conclusions • 나노두께 박막의 탄성계수와 간단한 micro machining 기술을 이용하여 나노두께 박막 고유의 탄성계수 측정법을 제시하였다. • 나노두께의 다이아몬드상 탄소박막의 기계적 물성은 합성조건에 따라 크게 달라졌으며, 이는 초기합성시 박막의 구조변화에 기인하였다. • 나노박막의 응용과 나노 multilayer의 기계적 물성변화를 해석할 때, 이러한 문제가 주의깊게 고려되어야 한다.

47. Acknowledgement • 원천기술개발사업, KIST (1999-2000) • 선도기술개발과제, 과기처 (1994-2001) • 플라즈마 응용 표면기술연구센터, 한국과학재단 (2000-2002) • 권동일교수, 정증현박사 (서울대학교)