Akira Furuya

Compositional dependence of electrical characteristics of SrBi2(Ta1−xNbx)2O9 thin-film capacitors

Ferroelectric capacitors using SrBi2(Ta1−xNbx)2O9 (SBTN) were compositionally altered varying Nb concentration from 0 to 1, the corresponding I–V and P–E electrical characteristics evaluated from room temperature to 145 °C. These temperature evaluations reveal that the leakage current will increase with larger Nb concentration and the dominant conduction mechanism changes from Schottky to Frenkel–Poole emission. The ferroelectric hysteresis curve shifts in the direction of negative polarization as the temperature or the concentration of Nb increases. Concentration increases in Nb reduces the temperature dependence of remnant polarization and coercive field. Film resistance to imprint and degradation from elevated temperature improves. Substituting b-site Nb for Ta allows imprinted capacitors to recover by application of either bipolar fatigue pulses at room temperature (RT) or, cycling P–E measurement pulses at elevated temperature. Due to this asymmetrical tradeoff of film ferroelectric properties, there...

Evaluation of Cu adhesive energy on barrier metals by means of contact‐angle measurement

The adhesive energies at Cu/SiO2, Cu/TiN, and Cu/TiW interfaces were investigated by measuring the contact angles of Cu particles to the substrate. To form the Cu particles, thin Cu films deposited on each substrate were annealed at 500 °C for 50 h. The adhesive energies are determined to be 0.8, 1.8, and 2.2 N/m for the SiO2, TiN, and TiW, respectively. The Cu particle on TiW film shows the highest adhesion. When TiW is used as a barrier metal, fine Cu lines are fabricated by reactive ions etching without peeling. On the other hand, Cu lines on the TiN film are peeled during the etching. This is consistent to the evaluation result that TiW has higher adhesive energy than TiN.

TI CONCENTRATION EFFECT ON ADHESIVE ENERGY AT CU/TIW INTERFACE

Changes in adhesive energy at Cu/TiW interfaces caused by varying the Ti concentration were evaluated by means of contact angle measurement. The adhesive energy was evaluated by applying the Young–Dupre equation to the contact angle. Copper particles were fabricated by annealing thin Cu film deposited on the TiW film. The adhesive energies at the Cu/TiW interface were evaluated as 1.5, 2.1, and 2.6 N/m for a Ti concentration of 0, 10, and 20 wt. %, respectively. The adhesive energies were found to increase almost linearly as the Ti concentration was increased. These results were applied to prevent TiW/Cu/TiW interconnects fabricated by using infrared-assisted reactive ion etching from peeling at the Cu/TiW interface. In annealing Cu films on TiW substrates at 600 °C in a vacuum, it was found that the Cu peeled from the TiW when the Ti concentration was 10 wt. %, but it stuck to that at 20 wt. %. The effect of Ti on the adhesion strength was also studied from the results of molecular calculation by using t...

Evaluation of CVD/PVD multilayered seed for electrochemical deposition of Cu-damascene interconnects

Multilayered seed for electrochemical deposition (ECD) of Cu was investigated to develop narrow-pitched, dual-damascene Cu interconnects that will be required for future ULSI devices. The seed was obtained by the physical vapor deposition (PVD) of a Cu film followed by the chemical vapor deposition (CVD) of a Cu film. The seed of the thinner CVD-Cu element and the thicker PVD-Cu element demonstrated better filling characteristics in high-aspect ratio vias. Good current-voltage characteristics were demonstrated using the multilayered seed technique with Cu dual-damascene interconnects (0.28 /spl mu/m minimum via size) resulting in a via resistance about 0.7 /spl Omega/. In addition, ring-oscillator circuits were fabricated by integrating the double-layered interconnects with a transistor having a 0.18 /spl mu/m gate width. The propagation delay per inverter, which had an interconnect with 10/sup 4/ vias, was about 6 ns. We successfully fabricated multilevel Cu-damascene interconnects, which are available for future high-speed devices using this multilayered seed technique.

Microstructure of Cu film sputter deposited on TiN

The correlation between the microstructure of Cu films and the deposition conditions of the sputtering method was investigated to obtain larger grain size and higher (111) texture. Cu film was deposited on SiO2 and TiN by varying substrate temperature, Ar gas pressure, and rf power. It is found that the texture of the Cu film has very little dependence on the deposition conditions. The Cu grains are more oriented to (111) on a TiN substrate than on a SiO2 substrate, and the (111) ratio of the Cu films on the TiN substrate increases as the (111) ratio of the TiN film is increased. The maximum increase in grain size was tenfold by reducing the Ar pressure from 3 to 1 mTorr, fivefold by increasing the deposition temperature from room temperature to 300 °C, and twofold by increasing the sputtering power from 1.1 to 4.4 W/cm2. Thus, it is revealed that the lowering of Ar gas pressure is the dominant factor for enlarging the grain size. An increase in the energy of Cu particles brought about by reducing the Ar gas pressure is discussed as one of the factors contributing to the increase in the grain size.The correlation between the microstructure of Cu films and the deposition conditions of the sputtering method was investigated to obtain larger grain size and higher (111) texture. Cu film was deposited on SiO2 and TiN by varying substrate temperature, Ar gas pressure, and rf power. It is found that the texture of the Cu film has very little dependence on the deposition conditions. The Cu grains are more oriented to (111) on a TiN substrate than on a SiO2 substrate, and the (111) ratio of the Cu films on the TiN substrate increases as the (111) ratio of the TiN film is increased. The maximum increase in grain size was tenfold by reducing the Ar pressure from 3 to 1 mTorr, fivefold by increasing the deposition temperature from room temperature to 300 °C, and twofold by increasing the sputtering power from 1.1 to 4.4 W/cm2. Thus, it is revealed that the lowering of Ar gas pressure is the dominant factor for enlarging the grain size. An increase in the energy of Cu particles brought about by reducing the Ar ...

Reduction of the hydrogen degradation in SrBi2(Ta1−xNbx)2O9 by TiN barrier metal

The use of ferroelectric SrBi2(Ta1−xNbx)2O9 (SBTN) as a mainstream form of nonvolatile memory requires that the degradation of its electrical qualities that is caused by annealing in a hydrogen atmosphere be reduced. Titanium nitride (TiN) is a candidate for use as a barrier-metal layer against hydrogen diffusion. The relationship between the degradation in the qualities of SBTN and the quality of the TiN barrier metal has been investigated. TiN when sputtered onto SBTN capacitors creates a good barrier under all sputtering conditions, and maintains the electrical characteristics of the SBTN through annealing in an atmosphere of H2. Higher density TiN films provide more effective protection. The characteristics of the degraded capacitor were investigated in terms of its current-voltage characteristic. Remanent polarization can be recovered from, at least partially, by applying a series of bipolar pulses. This rejuvenation of the electrical qualities indicates that degradation arises from a combination of ...

TiW/Cu/TiW interconnection lines patterned by IR-assisted RIE

This paper presents a new Cu-metallization technology which consists of TiW/Cu/TiW film structure formation and the followed IR-assisted RIE. It is demonstrated that line structure Cu lines, which have low electrical resistivity and high EM resistance, are obtained without peeling. Further, MOS diodes and MOSFETs using these lines have fine characteristics and they are stable up to 700/spl deg/C annealing.