Session 15: Measuring Substrate-Independent Young s Modulus of Thin Films

Transcription

1 Session 15: Measuring Substrate-Independent Young s Modulus of Thin Films Jennifer Hay Factory Application Engineer Nano-Scale Sciences Division Agilent Technologies jenny.hay@agilent.com To view previous sessions: Page 1

2 What s the problem? Low-k film (440 nm) on silicon? Berkovich indenter CSM (1nm, 75 Hz) Oliver-Pharr analysis Page 2

3 The solution: accounting for substrate influence Low-k film (440 nm) on silicon Berkovich indenter CSM (1nm, 75 Hz) Oliver-Pharr analysis PLUS thin-film analysis Hay, J.L. and Crawford, B., "Measuring Substrate-Independent Modulus of Thin Films," Journal of Materials Research 26(6), It was fun to read. Prof. Gang Feng, Villanova University Page 3

4 Both film and substrate influence measured response Development of strain field during nano-indentation of a film-substrate system, from Modelling Simul. Mater. Sci. Eng. 12 (2004) (Authors: Yo-Han Yoo, Woong Lee and Hyunho Shin) Page 4

5 Review of efforts to solve this problem (1986) Doerner and Nix: Analytic model assuming linear transition from to substrate and including an empirically determined constant. (1989) King: Form of Doerner-Nix model with no adjustable parameters. (1989) Shield and Bogy: Analytic model, but with physical problems. (1992) Gao, Chiu, and Lee: Simple approximate model. (1997) Mencik: Practical refinements to the Gao model. ( ) Song, Pharr, and colleagues: Alternate version of Gao s approximate model. Page 5

6 The Song-Pharr model with Gao s weight function 1 m a (1 1 I 0 ) m s I 1 m m shear modulus; E = 2m(1+n) 0 f a t film, m f substrate, m s Page 6

7 Modeling the relationship between two springs Springs (of differing stiffness) in series, subject to a force: The deformation in each spring is DIFFERENT. The more compliant spring deforms more. The MORE COMPLIANT spring dominates the response. Springs (of differing stiffness) in parallel, subject to a force: The springs undergo the SAME deformation. The STIFFER spring dominates the response Page 7

8 How to account for lateral support of the film? clearly series Parallel? When film is stiff: Deformation in the top layer of the substrate approaches that of the film. Film dominates the response. Page 8

9 Allow film to act both in series and parallel (Hay & Crawford, 2011) Indentation force Indentation force film film substrate film substrate previous form new form Page 9

10 But previous advancements are retained Gao s weight functions, I 0 & I 1 for gradually shifting influence of each spring with indentation depth. Mencik s suggestion that t = t 0 h c. Definition of effective Poisson s ratio suggested by Song and Pharr. Page 10

11 A new model for elastic film-substrate response Applied indentation force film film substrate Page 11

12 A new model for elastic film-substrate response force m f : shear modulus, film m s : shear modulus, substrate F : empirical constant; F = a : contact radius t : film thickness D : relates stiffness to modulus; D=4a/(1-n a ) I 0 : Gao s weighting function; as a/t 0, I 0 1; as a/t, I 0 0 Page 12

13 Solving for film modulus: m f = f(m a, m f, t 0, a, h c, F) Hay & Crawford, 2011 Sneddon, 1965, as implemented by Oliver and Pharr, 1992 Page 13

14 Solving for film modulus: m f = f(m a, m f, t 0, a, h c, F) Hay & Crawford, 2011 Sneddon, 1965, as implemented by Oliver and Pharr, 1992 Hay & Crawford, 2011 Page 14

15 Solving for film modulus: m f = f(m a, m f, t 0, a, h c, F) Hay & Crawford, 2011 Sneddon, 1965, as implemented by Oliver and Pharr, 1992 Hay & Crawford, 2011 Page 15

16 Solving for film modulus: m f = f(m a, m f, t 0, a, h c, F) Hay & Crawford, 2011 Sneddon, 1965, as implemented by Oliver and Pharr, 1992 Hay & Crawford, 2011 Gao, et al., 1992 Page 16

17 Solving for film modulus: m f = f(m a, m f, t 0, a, h c, F) Hay & Crawford, 2011 Sneddon, 1965, as implemented by Oliver and Pharr, 1992 Hay & Crawford, 2011 Gao, et al., 1992 Page 17

18 Solving for film modulus: m f = f(m a, m f, t 0, a, h c, F) Hay & Crawford, 2011 Sneddon, 1965, as implemented by Oliver and Pharr, 1992 Hay & Crawford, 2011 Gao, et al., 1992 Song & Pharr, 1999 Page 18

19 Solving for film modulus: m f = f(m a, m f, t 0, a, h c, F) Hay & Crawford, 2011 Sneddon, 1965, as implemented by Oliver and Pharr, 1992 Hay & Crawford, 2011 Gao, et al., 1992 Song & Pharr, 1999 Page 19

20 Solving for film modulus: m f = f(m a, m f, t 0, a, h c, F) Hay & Crawford, 2011 Sneddon, 1965, as implemented by Oliver and Pharr, 1992 Hay & Crawford, 2011 Gao, et al., 1992 Song & Pharr, 1999 Page 20

21 Solving for film modulus: m f = f(m a, m f, t 0, a, h c, F) Hay & Crawford, 2011 Sneddon, 1965, as implemented by Oliver and Pharr, 1992 Hay & Crawford, 2011 Gao, et al., 1992 Song & Pharr, 1999 Gao, et al., 1992 Page 21

22 Solving for film modulus: m f = f(m a, m f, t 0, a, h c, F) Hay & Crawford, 2011 Sneddon, 1965, as implemented by Oliver and Pharr, 1992 Hay & Crawford, 2011 Gao, et al., 1992 Song & Pharr, 1999 Menčίk et al., 1997 Gao, et al., 1992 Page 22

23 Solving for film modulus: m f = f(m a, m f, t 0, a, h c, F) Hay & Crawford, 2011 Sneddon, 1965, as implemented by Oliver and Pharr, 1992 Hay & Crawford, 2011 Gao, et al., 1992 Song & Pharr, 1999 Menčίk et al., 1997 Gao, et al., 1992 Page 23

24 Load on Sample/mN The value of finite-element simulations 70.3 o E f-in t Displacement/nm Analytic model E out Page 24

25 Load on Sample/mN The value of finite-element simulations 70.3 o E f-in t Displacement/nm Sneddon E out E apparent Page 25

26 Load on Sample/mN The value of finite-element simulations 70.3 o E f-in t Displacement/nm Sneddon & Hay-Crawford E out E film Page 26

27 Summary of 70 finite-element simulations (2D). Simulation E s, GPa Maximum indenter displacement (h), nm o E f = 10GPa 500 nm Page 27

28 Summary of 70 finite-element simulations (2D). Simulation E s, GPa Maximum indenter displacement (h), nm o E f = 10GPa 500 nm Page 28

29 Young's Modulus [GPa] Is everything OK with simulations? Ef=Es, apparent input film modulus for all simulations Indenter Penetration / Film Thickness [%] Page 29

30 Young's Modulus [GPa] Is everything OK with simulations? Ef=Es, apparent Ef=Es, film alone input film modulus for all simulations Indenter Penetration / Film Thickness [%] Page 30

31 Summary of 70 finite-element simulations (2D). Simulation E s, GPa Maximum indenter displacement (h), nm o E f = 10GPa 500 nm Page 31

32 Young's Modulus [GPa] Simulations: Compliant film on stiff substrate Ef/Es = 0.1, apparent input film modulus for all simulations Indenter Penetration / Film Thickness [%] Page 32

33 Young's Modulus [GPa] Simulations: Compliant film on stiff substrate Ef/Es = 0.1, apparent Ef/Es = 0.1, film alone input film modulus for all simulations Indenter Penetration / Film Thickness [%] Page 33

34 Young's Modulus [GPa] Simulations: Compliant film on stiff substrate Ef/Es = 0.1, apparent Ef/Es = 0.1, Film (Hay) Ef/Es = 0.1, Film (Song-Pharr) input film modulus for all simulations Indenter Penetration / Film Thickness [%] Page 34

35 Summary of 70 finite-element simulations (2D). Simulation E s, GPa Maximum indenter displacement (h), nm o E f = 10GPa 500 nm Page 35

36 Young's Modulus [GPa] Simulations: Stiff film on compliant substrate Ef/Es = 10, apparent input film modulus for all simulations Indenter Penetration / Film Thickness [%] Page 36

37 Young's Modulus [GPa] Simulations: Stiff film on compliant substrate Ef/Es = 10, apparent Ef/Es = 10, Film (Hay) input film modulus for all simulations Indenter Penetration / Film Thickness [%] Page 37

38 Young's Modulus [GPa] Simulations: Stiff film on compliant substrate Ef/Es = 10, apparent Ef/Es = 10, Film (Hay) Ef/Es = 10, Film (Song-Pharr) input film modulus for all simulations Indenter Penetration / Film Thickness [%] Page 38

39 Determining the value of F (fudge factor) E f-in sim. (P, h) E E f-out f = 2m f (1-n f ) F was determined as that value which minimized the sum of the squared relative differences (between output and input film moduli) over all 70 simulations. F : 70 d i 1 E f out E df f in / E f in 2 i 0 F = Page 39

40 Solving for film modulus: m f = f(m a, m f, t 0, a, h c, F) Hay & Crawford, 2011 Sneddon, 1965, as implemented by Oliver and Pharr, 1992 Hay & Crawford, 2011 Gao, et al., 1992 Song & Pharr, 1999 Menčίk et al., 1997 Gao, et al., 1992 Page 40

41 NanoSuite integration in CSM thin film methods Page 41

42 NanoSuite integration in ET thin film methods Page 42

43 Application: SiC on Si wafers Sample ID Description t nm 16 Silicon carbide (SiC) on Si Silicon carbide (SiC) on Si 300 Page 43

44 Experimental method Materials: o A set of 2 SiC films on Si Platform: Agilent G200 NanoIndenter with o DCM head o CSM option o Berkovich indenter o New test method: G-Series DCM CSM Hardness, Modulus for Thin Films.msm Page 44

45 Young's Modulus [GPa] Stiff films on compliant substrates: SiC on Si t=150nm, apparent citation of results Indenter Penetration / Film Thickness [%] Page 45

46 Young's Modulus [GPa] Stiff films on compliant substrates: SiC on Si t=150nm, apparent t=150nm, film citation of results Indenter Penetration / Film Thickness [%] Page 46

47 Young's Modulus [GPa] Stiff films on compliant substrates: SiC on Si t=150nm, apparent t=150nm, film t=300nm, apparent citation of results Indenter Penetration / Film Thickness [%] Page 47

48 Young's Modulus [GPa] Stiff films on compliant substrates: SiC on Si t=150nm, apparent t=150nm, film t=300nm, apparent t=300nm, film citation of results Indenter Penetration / Film Thickness [%] Page 48

49 Young's modulus, h/t=20% [GPa] SiC on Si: Modulus at h/t = 20% SiC on Si (t=150nm) Sample Film Apparent SiC on Si (t=300nm) Film modulus is about 25% higher than apparent modulus! Page 49

50 Application: low-k materials (on silicon) t 0 = 445 nm t 0 = 1007 nm Rapid Mechanical Characterization of low-k Films, Page 50

51 Experimental method Materials: o Two low-k films on Si Platform: Agilent G200 NanoIndenter with o DCM head o CSM option o Express Test option o Berkovich indenter Test Methods: o G-Series DCM CSM Hardness, Modulus for Thin Films o Express Test for Thin Films Page 51

52 Modulus of low-k film (t = 1mm) is 4.44±0.08GPa Page 52

53 Hardness of low-k film (t = 1mm) is 0.70±0.02GPa Page 53

54 Application: Ultra-thin films Page 54

55 Four samples Basecoat: sputter-deposited Al 2 O 3 (2600nm) Substrate: sintered Al 2 O 3 and TiC Page 55

56 Four samples PECVD SiO 2 (50nm) OR ALD Al 2 O 3 (50nm) Basecoat: sputter-deposited Al 2 O 3 (2600nm) Substrate: sintered Al 2 O 3 and TiC Page 56

57 Experimental method Agilent G200 with DCM II head and NanoVision Express Test Berkovich indenter Thin-film model applied to both basecoat and top layers. Page 57

58 Substrate independent modulus of 50nm films E = 146 GPa Application note: Page 58

59 In summary, the proposed model Has been verified by simulation and experiment. Is an improvement over prior models, because it works well whether the film is more compliant or more stiff than the substrate. Decreases experimental uncertainty by allowing measurements to be made at larger depths which would otherwise be unduly affected by substrate influence. Page 59

60 Application: Mechanical characterization of SAC 305 Solder by Instrumented Indentation Wednesday, May 14, 2014, 11:00 (New York) Abstract The reliability of soldered connections in electronic packaging depends on mechanical integrity; mechanical failure can cause electrical failure. Mechanical integrity, in turn, depends on mechanical properties. In this presentation, we focus on the SAC 305 solder alloy (96.5% tin, 3% silver, and 0.5% copper) due to its prevalent utilization in electronic packaging. First, we demonstrate the use of nanoindentation to measure the elastic and creep properties of SAC 305. Next, we utilize an advanced form of nanoindentation to quantitatively map mechanical properties of all the components of a realistic SAC 305 solder joint. To register: Page 60

61 Session 16: Best Practice for Instrumented Indentation Wednesday, June 11, 2014, 11:00 (New York) Abstract The purpose of this presentation is to provide a practical reference guide for instrumented indentation testing. Emphasis is placed on the better-developed measurement techniques and the procedures and calibrations required to obtain accurate and meaningful measurements. Recommended Reading Hay J.L. and Pharr G.M., Instrumented Indentation Testing, ASM Handbook: Mechanical Testing and Evaluation, Volume 8, pp (2000). To register: Page 61

62 Page 62 Thank you!

63 Two (sort of) independent problems Composite compliance: Substrate influences the stiffness that is measured. Errant contact area: Common model for determining contact area is strained in its application to thin films. These two problems are easily convoluted, because they both tend to push the calculated Young s modulus in the same direction. Page 63