Yukinori Hirose

Impact of additional Pt and NiSi crystal orientation on channel stress induced by Ni silicide film in metal?oxide?semiconductor field-effect transistors

The impact of additional Pt and Ni monosilicide (NiSi) crystal orientation on channel stress from Ni silicide in metal–oxide–semiconductor field-effect transistors (MOSFETs) has been demonstrated. The channel stress generation mechanism can be explained by the NiSi crystal orientation. In pure Ni silicide films, the channel stress in the p-type substrate is much larger than that in the n-type one, since the NiSi a-axis parallel to the channel direction is strongly aligned on the p-type substrate compared with on the n-type one. On the other hand, in NiPt silicide films, the difference in the channel stress between the p- and n-type substrates is small, because the NiSi crystal orientation on the p-type substrate is similar to that on the n-type one. These results can be explained by the Pt segregation at the interface between the NiSi film and the Si surface. Segregated Pt atoms cause the NiSi b-axis to align normal to the Si(001) surface in the nucleation step owing to the expansion of the NiSi lattice spacing at the NiSi/Si interface. Furthermore, the Pt segregation mechanism is considered to be caused by the grain boundary diffusion in the Ni2Si film during NiSi formation. We confirmed that the grains of Ni2Si on the p-type substrate are smaller than those on the n-type one. The Ni2Si film on the p-type substrate has more grain boundary diffusion paths than that on the n-type one. Therefore, the amount of Pt segregation at the NiSi/Si interface on the p-type substrate is larger than that on the n-type one. Consequently, the number of NiSi grains with the b-axis aligned normal to the Si(001) in the p-type substrate is larger than that in the n-type one. As a result, the channel stress induced by NiPt silicide in PMOS is larger than that in NMOS. According to this mechanism, controlling the Pt concentration at the NiSi/Si interface is one of the key factors for channel stress engineering.

Analysis of Channel Stress Induced by NiPt-Silicide in Metal–Oxide–Semiconductor Field-Effect Transistor and Its Generation Mechanism

Channel stress induced by NiPt-silicide films in metal–oxide–semiconductor field-effect transistors (MOSFETs) was demonstrated using UV-Raman spectroscopy, and its generation mechanism was revealed. It was possible to accurately measure the channel stress with the Raman test structure. The channel stress depends on the source/drain doping type and the second silicide annealing method. In order to discuss the channel stress generation mechanism, NiPt-silicide microstructure analyses were performed using X-ray diffraction analysis and scanning transmission electron microscopy. The channel stress generation mechanism can be elucidated by the following two factors: the change in the NiSi lattice spacing, which depends on the annealing temperature, and the NiSi crystal orientation. The analyses of these factors are important for controlling channel stress in stress engineering for high-performance transistors.

Characterization of Low-k/Cu Damascene Structures Using Monoenergetic Positron Beams

Defects in SiOCH/Cu damascene structures were probed using monoenergetic positron beams. Doppler broadening spectra of the annihilation radiation and positron lifetime spectra were measured for samples patterned with 0.54- and 2.16-µm pitches. An analysis using the lineshape parameters S and W was shown to provide useful information about pores and vacancies in materials buried in the damascene structure. The lifetime and intensity of positronium trapped by pores in SiOCH were decreased by the scaling, which was attributed to the shrinkage of pores and an introduction of electron/hole traps by the fabrication process of the damascene structure.

Analysis of Junction Leakage Current Failure of Nickel Silicide Abnormal Growth Using Advanced Transmission Electron Microscopy

This is the first paper to reveal the formation mechanism of the abnormal growth of nickel silicide that causes leakage-current failure in complementary metal-oxide- semiconductor (CMOS) devices by using advanced transmission electron microscope (TEM) techniques: electron tomography and spatially-resolved electron energy-loss spectroscopy (EELS). We reveal that the abnormal growth of Ni silicide results in a single crystal of NiSi2 and that it grows toward Si <;110> directions along (111) planes with the Ni diffusion through the silicon interstitial sites. In addition, we confirm that the abnormal growth is related to crystal microstructure and crystal defects. These detailed analyses are essential to understand the formation mechanism of abnormal growths of Ni silicide.

Structure-Modification Model of Porogen-Based Porous SiOC Film with Ultraviolet Curing

The effect of ultraviolet (UV) curing on film properties of porogen based porous SiOC (P-SiOC) film was investigated. The P-SiOC films were prepared by plasma-enhanced chemical vapor deposition (PECVD) using alkoxysilane and porogen (hydrocarbon). UV curing time was changed from 0 s to 1000 s. The variation of the k value and elastic modulus on the P-SiOC film with UV curing can be classified into three phases. From the behavior of pore density and free volume rate evaluated by using positron annihilation spectroscopy (PAS), the multiphase model for structural modification of P-SiOC film by UV curing was proposed. In addition, the optimum UV curing time for obtaining a superior P-SiOC film with lower k value and higher mechanical strength was determined.

Three-Dimensional Visualization Technique for Crystal Defects in High Performance p-Channel Metal–Oxide–Semiconductor Field-Effect Transistors with Embedded SiGe Source/Drain

We have performed a detailed analysis of crystal defects in high-performance p-channel metal–oxide–semiconductor field-effect transistors (pMOSFETs) with embedded SiGe source/drain (S/D), using low-angle annular dark field (ADF) scanning transmission electron microscopy (STEM) and electron tomography. We achieved successful results in three-dimensional visualization of crystal defects for the first time. Consequently, we have discussed about the three-dimensional physical geometric relationship between crystal defects and device architecture. This approach is sure to contribute to the development of advanced complementary metal–oxide–semiconductor (CMOS) devices using strained silicon technology.

Study of formation mechanism of nickel silicide discontinuities in high performance CMOS devices

We performed detailed analysis of Ni silicide discontinuities induced by agglomeration that causes the increasing electric resistance in high-performance CMOS devices by using advanced physical analysis techniques. We confirmed that the agglomeration of the Ni silicide is related to elongated-triangular- shaped-splits — which we call delta-shaped-splits — which cause discontinuities that occur at small-angle grain boundaries pinned by boron clusters even with small stress. We successfully determined the formation mechanism of the Ni silicide discontinuities in detail. It is essential to develop a highly reliable Ni salicide process, especially for 45 nm node high performance devices and beyond.

Analysis of Ni silicide abnormal growth mechanism using advanced TEM techniques

We performed detailed analysis of the abnormal growth of Ni silicide that causes leakage-current failure in CMOS devices. We investigated the three-dimensional shape and the crystal microstructure of the abnormal growth by using advanced transmission electron microscope (TEM) techniques: electron tomography and spatially-resolved electron energy-loss spectroscopy (EELS). Furthermore, we revealed that the abnormal growth is related to crystal microstructure and crystal defects. This detailed information is important in the mechanism elucidation of abnormal growth of Ni silicide. To develop a highly reliable Ni salicide process, it is essential to understand the failure mechanism of abnormal growths of Ni silicide, especially for 45 nm node devices and beyond. To conclude, we discuss the solutions for the development of a successful Ni salicide process.

Study of formation mechanism of nickel silicide discontinuities in high-performance complementary metal–oxide–semiconductor devices

We performed detailed analysis of nickel silicide discontinuities induced by agglomeration, which causes the increased electric resistance in high-performance complementary metal–oxide–semiconductor devices, by using advanced physical analysis techniques: transmission electron microscopy (TEM), scanning electron microscopy (SEM) electron backscatter diffraction (EBSD) analysis, and three-dimensional atom-probe (AP) analysis. We confirmed that the agglomeration of the nickel silicide is related to elongated-triangular-shaped splits, which cause discontinuities that occur at low-angle grain boundaries pinned by boron clusters even with small stress. We successfully determined the formation mechanism of these nickel silicide discontinuities in detail.

Characterizations of NiSi2-Whisker Defects in n-Channel Metal?Oxide?Semiconductor Field-Effect Transistors with Channel on Si(100)

Electrical and physical characteristics of nickel disilicide (NiSi2)-whisker defects in n-channel metal–oxide–semiconductor field-effect transistors (nMOSFETs) on Si(100) have been investigated. NiSi2-whisker defects are easily generated in narrow-channel-width nMOSFETs with the channel on Si(100) and anomalously increase the leakage current between the drain and the source. A NiSi2 whisker elongates toward the direction along the trench edge and pierces the channel region. These physical properties of NiSi2-whisker defects were revealed by detailed failure analyses. The influence of the recessed depth of trench-fill oxides on NiSi2-whisker defects was also investigated. Furthermore, it is found that trench-edge defects, such as Si(111) stacking faults, are generated in the channel before the Ni silicide formation. These trench-edge defects were not observed in the channel. We also propose a generation model for NiSi2-whisker defects. The nucleation of NiSi2 precipitates might be generated at trench-edge defects, and Ni atoms diffuse toward the direction during the silicidation annealing. As a result, NiSi2-whisker defects are generated toward the direction at the trench edge.