Interpretation of texture changes during self-annealing of electroplated copper

Zhang, W. Q.; Li, A. D.; B., G.; Yin, Kuibo; Xia, Yidong; Liu, Z. G.; Chan, Chia‐Hsin; Cheung, Ka Lun; Bayes, Martin; Yee, K. W.

doi:10.1016/j.mee.2010.05.007

Cited by 6 publications

(6 citation statements)

References 30 publications

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“…The observations made in the aforementioned studies on the stability of different texture components are in contrast to the ones made in [30], where the (111) texture becomes increasingly pronounced. To further complicate the picture, it can be noted that observations have been made in [31] of evolution of (110) and (311) textures in Cu thin films several days or months after deposition.…”

Section: Microstructure Mechanisms Involved In the Self-annealingmentioning

confidence: 99%

Investigation of microstructure evolution during self-annealing in thin Cu films by combining mesoscale level set and ab initio modeling

Hallberg

Olsson

2016

Journal of the Mechanics and Physics of Solids

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Microstructure evolution in thin Cu films during room temperature self-annealing is investigated by means of a mesoscale level set model. The model is formulated such that the relative, or collective, influence of anisotropic grain boundary energy, mobility and heterogeneously distributed stored energy can be investigated. Density functional theory (DFT) calculations are performed in the present work to provide the variation of grain boundary energy for different grain boundary configurations. The stability of the predominant (111) fiber texture in the as-deposited state is studied as well as the stability of some special low-Σ grain boundaries. Further, the numerical model allows tracing of the grain size distribution and occurrence of abnormal grain growth during self-annealing. It is found that abnormal grain growth depends mainly on the presence of stored energy variations, whereas anisotropic grain boundary energy or mobility is insufficient to trigger any abnormal growth in the model. However, texture dependent grain boundary properties, mobility in particular, contribute to an increased content of low-Σ boundaries in the annealed microstructure. The increased presence of such boundaries is also promoted by stored energy variations. In addition, if the stored energy variations are sufficient the coexisting (111) and (001) texture components in the as-deposited state will evolve into a (001) dominated texture during annealing. Further, it is found that whereas stored energy variations promote the stability of the (001) texture component, anisotropic grain boundary energy and mobility tend to work the other way and stabilize the (111) component at the expense of (001) grains.

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Section: Microstructure Mechanisms Involved In the Self-annealingmentioning

confidence: 99%

Investigation of microstructure evolution during self-annealing in thin Cu films by combining mesoscale level set and ab initio modeling

Hallberg

Olsson

2016

Journal of the Mechanics and Physics of Solids

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“…However, since the 60° twinning in f.c.c. materials is caused by a rotation around <111> the relation between {111} and {115} orientations and vice versa is explainable by 1 st order twins [10]. This relation is shown in the texture plot in Fig.…”

Section: Results: Grain Orientationmentioning

confidence: 77%

“…5 The appearance of orientations near {101} is described by Stangl et al [3] and correlates with layer thickness as well as plating parameters [13]. In the case of 1 st order twinning of {101} orientations, the resulting orientations are {101} and {114} [10]. Therefore, some of these twins are barely visible in Fig.…”

Section: Results: Grain Orientationmentioning

confidence: 90%

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Influence of liner-system and Cu-layer thickness on the grain structure of electroplated Cu

Mueller

Kriz

Meinhold

et al. 2012

2012 4th Electronic System-Integration Technology Conference

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The grain structure of 1.2 µm electroplated Cu layers with undoped Cu seed layer has been investigated using electron backscatter diffraction (EBSD). Therefore orientation imaging microscopy (OIM) was carried out on samples with five different liner systems (Ti, Ta, WTi, TiN and TaN), three different annealing steps (self-anneal at room temperature, 1 h at 110 °C and 0.5 h at 380 °C) and two plating chemistries with varying acid content. In addition, samples with 1 µm and 3 µm electroplated Cu on an Al-doped Cu seed layer have been analyzed in order to investigate the influence of the plated layer thickness on grain structure.The results show that the grain structure is dominated by low energy CSL boundaries, especially Σ3 twins, which can be found in almost every grain. This twinning causes a typical deviation from the expected {111} orientation parallel to the sample surface towards {115} orientations. This is the result of the self-annealing process (caused by recrystallization).Differences in orientation caused by the liner system will be shown as well as influences of the Cu-plating thickness on the fraction of {101} orientations. Finally, changes in grain size and twinning fraction due to subsequent annealing steps will be presented. IntroductionSince Cu was successfully implemented in semiconductor processes, the variety of applications of Cu based devices has grown steadily. With its higher electrical and thermal conductivity, its better thermal stability and its smaller coefficient of thermal expansion compared to Al, Cu pushed the limits for clock frequencies and power consumption for semiconductor devices. In frontend applications the Cu grain size gains more and more importance on the overall performance and reliability of the interconnect system [1-2]. Apart from the importance for frontend applications, the development of highly integrated 3D systems, as well as power applications creates a need for Cu based backend technologies, such as direct Cu-Cu Bonding and Cu to Cu wire bonding. The properties of Cu such as surface oxidation or the mechanical behavior like hillock formation and Cu protrusion in through silicon vias (TSV) are only some of the challenges, which need further process related investigations on microstructure in order to make Cu based interconnection technologies more reliable.Cu thin films are deposited by electrochemical deposition because of its good filling properties (compared to physical vapor deposition), its availability due to the frontend applications, and the fast and cost efficient process implementation. The resulting grain structure undergoes a so called self-annealing process after plating that causes a microstructure evolution at room temperature accompanied by decreasing resistance and hardness [3][4][5][6][7][8]. Investigations by

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“…The sums are taken over the first five diffraction peaks [26]. We normalize the data further with respect to ψ to partially correct the dependence of the diffraction signal on the combination of ψ and 2θ according to…”

Section: Texturementioning

confidence: 99%

Properties of electroless Cu films optimized for horizontal plating as a function of deposit thickness

Sharma

Brüning

Nguyen

et al. 2015

Microelectronic Engineering

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The properties of electroless films produced from a bath designed for horizontal plating, the preferred technology for high production volumes in printed circuit board metallization, are reported. Film thickness, substrate type and electrolyte temperature were varied. Formation of a continuous layer of copper film is correlated with a change in the visual and spectroscopic appearance. Grain orientation is random in thin films and a 〈110〉 texture develops with increasing thickness. The plating solution contains Cu and Ni ions. Nickel co-deposits in copper films in the form of Ni hydroxide, and its concentration decreases from about 6% in the vicinity of the substrate to about 1% at the film surface. Film stress and strain were measured by substrate curvature and X-ray diffraction, respectively. Both stress and strain decrease as the film thickness increases. Stress remains tensile throughout during deposition and during relaxation, promoting film adhesion by preventing blisters. After deposition, stress relaxes first towards compressive and then towards tensile. The stress, the stress relaxation and the Ni concentration are high at the base of the film. We attribute this to the higher volume fraction of grain boundaries (smaller grain size) in this region.

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Interpretation of texture changes during self-annealing of electroplated copper

Cited by 6 publications

References 30 publications

Investigation of microstructure evolution during self-annealing in thin Cu films by combining mesoscale level set and ab initio modeling

Investigation of microstructure evolution during self-annealing in thin Cu films by combining mesoscale level set and ab initio modeling

Influence of liner-system and Cu-layer thickness on the grain structure of electroplated Cu

Properties of electroless Cu films optimized for horizontal plating as a function of deposit thickness

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