Application of High-pressure Annealing Process to Dual Damascene Copper Interconnections

Phys. Status Solidi (c)

Kihara

Araki

et al. 2007

Self Cite

Positron lifetime measurements have been performed for Cu thin films in order to identify lattice defects. Theoretical positron lifetimes of vacancy clusters of Cu are also calculated for identification of the experimental values. Cu thin films were prepared by electro chemical deposition (ECD) and physical vapour deposition (PVD). All of the Cu thin films have longer positron lifetimes than bulk Cu does. This indicates that lattice defects are introduced during deposition. However composition analysis of positron lifetimes shows that whereas vacancy clusters exist in the ECD-Cu thin film, the positron lifetime of defect component in the PVD-Cu thin films is shorter than that of mono-vacancy. On the other hand, the positron lifetime of mono-vacancy was detected in PVD-Cu-0.5 at%Sb thin film prepared by PVD. In order to elucidate the effect of Sb, first-principles calculations have been performed for Cu including Sb and monovacancy. The result suggests that mono-vacancies are introduced because of the binding energy between a Sb atom and mono-vacancy. 1 Introduction The dual-damascene fabrication process is presently recognized as a standard Cu interconnection technique. In this technique, metallic barrier layers and Cu seed layers are deposited in successive order on the inside walls of via holes or trenches using a sputtering method (physical vapour deposition; PVD). The Cu interconnections are then embedded into via holes or trenches using an electrochemical deposition (ECD).As the diameter of the via holes becomes smaller and smaller, the relative embedding performance tends to decline. The high pressure anneal process is attracting attention because of its excellent capabilities in the filling performance of high aspect-ratio via holes and improved adhesion of wiring Cu interconnections. The PVD method is attractive from the viewpoint of simplifying the entire process and alloying of Cu-film to further enhance the electron migration resistance for example. However the PVDCu films requires higher temperatures than the ECD films to fill via holes completely by the high pressure annealing process [1,2]. On the other hand, it was found that the addition of Sb to the PVD-Cu lowers the required temperature. In the present study, positron lifetime measurement and its theoretical calculation have been performed for the ECD and PVD-Cu thin films in order to identity lattice defects, which can affects the filling behaviour.

mentioning

confidence: 99%

Identification of lattice defects in Cu thin films by positron annihilation spectroscopy

Phys. Status Solidi (c)

Kihara

Araki

et al. 2007

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“…Figure 1 shows a schematic drawing of the high-pressure annealing system used in this study. 13 In the experiments, the temperature and pressure were increased linearly from room temperature (RT) with no applied load up to a fixed temperature (up to 600°C) and pressure (150 MPa) at a heating rate of 5°C min À1 . The high temperature and pressure were maintained for 120 min, and then decreased linearly back to RT with no applied load at a cooling rate of 5°C min À1 .…”

Section: Methodsmentioning

confidence: 99%

“…In this process, Cu is deposited into vias and trenches by sputtering and is then mechanically deformed and embedded in the vias and trenches by high-temperature high-pressure treatment, thereby increasing the reliability of the interconnect and consequently improving yield. [12][13][14] Sputtered Cu films have higher purity compared with electroplated ones, and there is no possibility of inclusion of electrochemical reagents. This fact has encouraged us to reconsider the application of sputtering in the fabrication of Cu interconnections, because even for electroplated Cu films, it is still necessary to sputter the seed layers which act as electrodes for electroplating.…”

Section: Introductionmentioning

confidence: 99%

A Study of Difference in Reflow Characteristics Between Electroplated and Sputtered Cu in a Dual-Damascene Fabrication Process for Silicon Semiconductor Devices

Onishi

Fujikawa

et al. 2011

Journal of Elec Materi

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The difference in reflow characteristics between electroplated and sputtered Cu films during high-temperature high-pressure treatment was confirmed, and the basis for this difference was analyzed. Using test element groups containing a number of via holes, it was found that electroplated Cu films had much superior embedding characteristics compared with sputtered Cu films. This was confirmed by measurements of the stress-strain curves of these Cu films, which indicated that the strength at high temperature of the electroplated films was lower than that of sputtered films. Identification of lattice defects and analysis of the microstructure of these films were carried out by positron lifetime measurements and transmission electron microscopy, respectively. The results showed that a large quantity of vacancy clusters was present in the electroplated Cu films, and this increased to a maximum after isochronal annealing at 300°C. From the results, it was shown that Cu atoms in electroplated films with a large number of vacancy clusters diffuse rapidly at around 300°C, and this rapid diffusion contributes greatly to softening of the film and a promotion in reflow behavior. This study revealed that the reflow behavior of Cu films strongly depends on the presence of vacancy clusters within it.

“…Figure 5 shows a cross-sectional sketch of the pressure vessel that was used for the high-pressure annealing process in this study. 13 After the high-pressure annealing process, parts of the TEGs were examined by cross-sectional secondary-ion microscopy (SIM) so that we could estimate the filling level of the Cu. The filling level of the Cu was determined quantitatively as the filling area ratio by editing of the SIM images.…”

Section: Methodsmentioning

confidence: 99%

“…In this process Cu interconnections are deposited onto via holes and trenches by a sputtering method and are then mechanically deformed and embedded into via holes and trenches by high-temperature and high-pressure treatments, thereby increasing the reliability of the Cu interconnections and consequently improving yields. [9][10][11][12][13][14] However, the embedding mechanism for Cu interconnections has not yet been elucidated sufficiently. In this study we analyzed the reflow phenomenon of Cu interconnection into via holes by the use of viscoelastic deformation simulation, and we considered the mechanics of the reflow mechanism.…”

Section: Introductionmentioning

confidence: 99%

Reflow Phenomenon Analysis of Large Scale Integrated Cu Interconnections in Via Holes by Viscoelastic Deformation Simulation

Onishi

Yoshikawa

et al. 2010

Journal of Elec Materi

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The reflow phenomenon of Cu interconnections deposited over via holes was analyzed by viscoelastic deformation simulation using a finite-element method to clarify the embedding mechanism of Cu interconnections into via holes in a novel dual-damascene fabrication technology, which combined sputter deposition and high-pressure annealing. Cu is considered to be a viscoelastic body, and the stress distribution and deformation behavior of Cu interconnections were calculated. As a result, the deformation behavior of the Cu interconnections exhibited close agreement between the calculated and the observed values. From our series of results, we inferred that Cu interconnections are embedded into via holes by the creep deformation mechanism defined in this study during the high-pressure annealing process.