Vacancy-Induced Plastic Deformation in Electrodeposited Copper Films

Many aspects of the electrochemistry of copper in aqueous acid solution are dominated by the presence of low coverage, high energy, metastable surface states which constitute surface active sites. Such states undergo quasireversible redox transitions within the double-layer region, and these species play a vital role in electrocatalytic and electrodeposition processes in the case of this electrode system. In the present work this aspect of copper electrochemistry is explored using alternating current impedance techniques and one of the main conclusions drawn is that there are often important aspects of surface electrochemistry that can only be rationalized in terms of the unusual properties of the active, highly defective, state of the surface.

mentioning

confidence: 99%

AC Impedance Investigation of Copper in Acid Solution

Burke

Sharna

2008

“…For example, excess vacancies may migrate to grain boundaries during the annealing, which creates free volumes and grooves. 24 Grain-size effect on Cu chlorination process.- Figure 3 shows the Cu conversion and CuCl x formation rates during the plasma-Cu reaction vs the original Cu film annealing temperature. The plasma exposure condition was fixed at 600 W, 60 mTorr, and Cl 2 flow rate of 12 sccm.…”

Section: Resultsmentioning

confidence: 99%

Grain-Size Effect on a Plasma-Based Copper Etch Process

Liu

Kuo

Ahmed

et al. 2008

The effect of the copper film's microstructure on the Cl 2 plasma-based copper etch process has been studied. Copper films were sputter deposited and annealed at different temperatures. The film's grain size increased and the resistivity decreased with the annealing temperature. Under the same plasma exposure condition, the copper conversion rate and the CuCl x reaction product formation rate increased monotonically with the grain size. At the same time, the Cl content and the porosity of CuCl x increased with the grain size. The roughness of the etched Cu surface also increased with the original copper grain size. These observations were explained by diffusion mechanisms of Cl and Cu atoms in the plasma-copper reaction process as well as microstructures of CuCl x and the original copper film.

“…It is proposed [6][7][8][9] that the phenomenon of SMC arises from a volume contraction in the copper film due to the out-diffusion of excess vacancies. Vacancies have relatively high diffusivity in copper at room temperature and will tend to migrate to the surface.…”

Section: D106mentioning

confidence: 99%

“…Thus, the study of the deposition and properties of copper metallization films is of major importance to the semiconductor industry. In particular, understanding and controlling the microstructure of electrodeposited copper [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] metallization is increasingly important.…”

mentioning

confidence: 99%

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An Isothermal Annealing Study of Spontaneous Morphology Change in Electrodeposited Copper Metallization

Ahmed

Buckley

Nakahara

et al. 2007

Self Cite

A systematic investigation of the effect of annealing time and temperature on the incubation period for spontaneous morphology change ͑SMC͒ in electrodeposited copper metallization is reported. Based on an additivity principle derived by Mittemeijer for transformations with an Arrhenius-type dependence of kinetics on temperature, it is shown that the remaining incubation time for SMC at room temperature following annealing at a given temperature should be linearly related to the annealing time. By repeatedly scanning atomic-force microscopy images at room temperature, the time at which SMC occurred was determined for films annealed for various times at temperatures ranging from 32 to 60°C. At each temperature studied, the remaining incubation time at room temperature was found to decrease approximately linearly with increasing annealing time, thus experimentally verifying the behavior predicted by the additivity principle. An Arrhenius plot of the measured rates of decrease showed good linearity and yielded a value of 0.48 eV for the activation energy. This is consistent with a vacancy diffusion mechanism for the process occurring during the incubation period, and supports our proposed mechanism for SMC.Copper has been widely adopted as an interconnection material in ultralarge-scale integrated ͑ULSI͒ circuits. 1-3 Electrodeposition is the technology of choice for the fabrication of copper interconnects because of factors such as the ability to fill dual damascene architectures without voids, lower cost, and better electromigration performance. As a consequence of its rapid growth, the technology has in many respects outpaced fundamental scientific understanding, and many important questions need to be investigated if technological progress is to be maintained. Thus, the study of the deposition and properties of copper metallization films is of major importance to the semiconductor industry. In particular, understanding and controlling the microstructure of electrodeposited copper 4-22 metallization is increasingly important.It has been observed that the microstructure of both sputtered and electrodeposited copper can change considerably with time, even at room temperature. 4,23-33 The effects of additives to the plating bath on the electrodeposition and properties of copper metallization have been studied extensively. 15,18,19 Scanning probe microscopy, including atomic force microscopy ͑AFM͒ and scanning tunneling microscopy ͑STM͒, has proved to be a useful tool to study copper electrodeposition; [4][5][6][7][8][11][12][13][14][15][16][17][18][19][20][32][33][34][35][36][37][38][39][40][41][42][43] mechanistic studies, the effect of additives, and the influence of the substrate on microstructure have been reported. The influence of various additives on the roomtemperature recrystallization of electrodeposited copper has been investigated by Stafford et al. 22 using X-ray diffraction and resistance measurements. Lingk and Gross 27 demonstrated the influence of damascene topography and showed that initiation of r...