Progress in Thermal Fatigue of Micro/Nano-ScaleMetal Conductors
Guangping ZHANG1(), Honglei CHEN1,2, Xuemei LUO1, Bin ZHANG3
1 Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China 2 School of Materials Science and Engineering, University of Science and Technology of China, Shenyang 110016, China 3 Key Laboratory for Anisotropy and Texture of Materials, Ministry of Education, School of Materials Science and Engineering, Northeastern University, Shenyang 110819, China
Cite this article:
Guangping ZHANG, Honglei CHEN, Xuemei LUO, Bin ZHANG. Progress in Thermal Fatigue of Micro/Nano-ScaleMetal Conductors. Acta Metall Sin, 2018, 54(3): 357-366.
The world has gradually entered the industrial 4.0 Era, which is dominated by the Internet of Things (IOT) and intelligent manufacturing. Especially, strong requirement for artificial intelligence and big data processing, the development and preparation of micro/nano electronic devices is becoming increasingly active, and much more concerns have been attracted to small-scale materials. Because of the constraint effect of geometric and microstructural dimensions of these materials, the thermal fatigue damage behavior is different from that of the bulk counterparts. At the same time, the change of the material scale from microns to nanometers also results in the transformation of the deformation mechanism, so that the materials exhibit different damage behaviors and significant size effects. In this paper, thermal fatigue testing methods, thermal fatigue damage and evolution, and the factors influencing thermal fatigue properties of metal film/line are reviewed, the corresponding mechanism of thermal fatigue and the size effect of the micro/nano-scale metals are discussed. The prospective research of this field in the future is addressed.
Fig.1 Schematics of the sample structure (a) two pads on the two ends of the line are used for electric contacts (W and L present the width and the length of the testing line, respectively) (b) schematic illustration of the testing setup
Film
Substrate
t / nm
W / μm
D / μm
j / (MAcm-2)
f / Hz
Ref.
Cu/Ta
Surface
100
8~15
0.5±0.2
14~24
200
[33]
oxidized Si
300
8~15
1.5±0.5
14~24
200
200
8~15
1.0±0.5
14~24
200, 20000
[43]
300
0.5±0.2
14~24
200
Cu/Ta/SiNx
Surface
200
8
1.5±0.5
10~40
200, 20000
[35]
oxidized Si
300
8
0.5±0.2
10~40
200, 20000
Cu/Ta/SiNx with/without
Surface
200
8
1.3±0.5
10~40
20000
[34]
photoresist encapsulation
oxidized Si
Al-1%Si (atomic fraction)
Surface
550
3.3
-
10, 11
200
[17]
with/without photoresist
oxidized Si
encapsulation
Al-1%Si (atomic fraction)
Surface
550
3.3
0.3~0.6
12.2±0.3
200
[17]
with SiNx encapsulation
oxidized Si
Cu
Surface
60
5, 10, 15
0.055±0.02
3.2~26.5
50
[37]
oxidized Si
Au
SiO2
200
2
0.074±0.011
3.5~11.5
50
[45]
Au
Surface
35
0.1~5
0.032±0.012
3.5~35.2
100
[38]
oxidized Si
Table 1 Material systems and experiment parameters of thermal fatigue by some researchers[17,33~35,37,38,43,45]
Fig.2 Relationship between strain range and thermal fatigue life of various metal lines reported by some researchers under various test conditions[33~35,37,42,43,45] (half-filled symbols) (More details are listed in Table 1. Mechanical fatigue data for bulk Cu[46] (solid line) and Cu films[47] (solid symbols) were also presented)
Fig.3 Typical damage morphologies of <100> out-of-plane oriented grains (a) and <111> out-of-plane oriented grains (b) (The left images show the early stages of damage formation and the right images show the later stages)
Fig.4 TEM observations of the damaged (111) out-of-plane oriented grain in thermally fatigued Cu films(a) brighter regions are thinned areas near grain and twin boundaries. The voids along the twin bound- ary are indicated with arrows(b) dislocations with three different Burgers vectors on (111) slip plane (1, 2 and 3) are also indicated. Dislocations 1 are invisible under the present g=200 vector
Fig.5 Schematic of mechanical fatigue and thermal fatigue mechanisms of thin metal films as a function of characteristic size in the small-scale metal materials (Tm—melting point temperature; T0—room temperature; dc—critical characteristic size to cause fatigue mechanism transformation; d—film thickness; σ—tensile stress applied to films during thermal cycling; GB—grain boundary; PSB—persistent slip band)
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