Toshiaki Tsutsumi

Suppression of Anomalous Gate Edge Leakage Current by Control of Ni Silicidation Region using Si Ion Implantation Technique

It is reported for the first time that the anomalous gate edge leakage current in NMOSFETs is caused by the lateral growth of Ni silicide toward the channel region, and this lateral growth is successfully suppressed by the control of the Ni silicidation region using the Si ion implantation (Si I.I.) technique. As a result, the anomalous gate edge leakage current is successfully reduced, and the standby current and yield for 65nm-node SRAM are greatly improved. This novel technique has high potential for 45nm and 32nm CMOS technology

Improvement of thermal stability of nickel silicide using N 2 ion implantation prior to nickel film deposition

Nitrogen ion implantation (N2 I.I.) prior to Ni film deposition successfully suppresses the agglomeration of nickel silicide (NiSi) formed on arsenic doped silicon substrate in NMOS region, and drastically improves the thermal stability of its resistivity at narrow lines. Using this technique, lower sheet resistance of NiSi narrow line can be kept at high annealing temperature of 650degC for 30 sec. Comparing with argon ion implantation (Ar I.I.), only the N2 I.I. can suppress the agglomeration of NiSi. These results suggest that the implanted N2 ions form Ni-N or Si-N bonds in NiSi, and as a result, these bonds suppress the excess diffusion of Ni and Si atoms during thermal process

Anomalous Nickel Silicide Encroachment in n-Channel Metal–Oxide–Semiconductor Field-Effect Transitors on Si(110) Substrates and Its Suppression by Si+ Ion-Implantation Technique

A novel low-leakage-current nickel self-aligned-silicide (SALICIDE) process in n-channel metal–oxide–semiconductor field-effect transistors (nMOSFETs) on Si(110) substrates is reported. Anomalous nickel silicide encroachment in the direction in nMOSFETs on Si(110) substrates is found for the first time. This encroachment causes anomalous off-state leakage current (Ioff) in nMOSFETs on Si(110) substrates. In particular, in the case of the channel on Si(110) substrates, Ni atoms easily diffuse in the direction, and nickel silicide preferentially grows in the direction. As a result, anomalous leakage current between the drain and the source occurs, and the leakage current seriously degrades transistor performance. In order to overcome these problems, we propose a method of suppressing anomalous Ioff on Si(110) substrates by Si+ ion-implantation technique prior to the nickel SALICIDE process. This method is effective for suppressing the encroachment of nickel silicide and realizing low-leakage complementary metal–oxide–semiconductor (CMOS) devices on Si(110) substrates.

Anomalous Gate-Edge Leakage Current in nMOSFETs Caused by Encroached Growth of Nickel Silicide and Its Suppression by Confinement of Silicidation Region Using Advanced

The anomalous gate-edge leakage current in n-channel metal-oxide-semiconductor field-effect transistors (nMOSFETs), which is caused by the encroached growth of nickel silicide across the p-n junction, is first reported. Furthermore, this encroached growth, which is caused by the isotropic and rapid diffusion of Ni atoms during the silicidation annealing, is successfully suppressed by the advanced Si+ ion-implantation (Si-I.I.) technique. Using the Si-I.I. technique, both the anisotropic silicidation to the perpendicular direction and the phase transition from Ni2Si to NiSi are enhanced by the introduction of damaged layers into Si substrates, such as vacancy and amorphous Si layers, and as a result, the silicidation region is confined at the source and drain regions. In addition, we propose a new evaluation method for the quantitative analysis of the encroached growth based on its growth properties, namely, the variability of encroached growths, which is three standard deviations of the roughness at silicide edges. The usefulness of this simple analysis for a large number of nMOSFETs is also demonstrated.

\hbox{Si}^{+}

A novel low leakage-current Ni SALICIDE process in nMOSFETs on Si(110) is proposed. It is found for the first time that the anomalous off-state leakage-current (Ioff) in nMOSFETs on Si(110) is caused due to the inherent Ni silicide encroachment toward the channel region. Especially, <110> channel on Si(110) has fatal defect for CMOS fabrication. We propose two methods to suppress the anomalous Ioff, the creative ingenuity of design layout within SRAM and Si ion implantation (Si I.I.) technique. These two methods are quite effective to realize high performance and low cost CMOS devices on Si(110).

Ion-Implantation Technique

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.

A Novel Low Leakage-Current Ni SALICIDE Process in nMOSFETs on Si(110) Substrate

Effects of dry-etching damage at the surface of p-type silicon on pyramidal spike growth of nickel disilicide (NiSi2) were investigated by using sheet resistance (Rs) measurement, cross sectional SEM7TEM, UV Raman spectroscopy and elastic recoil detection analysis (ERDA), and as a result, a model for nickel diffusion induced by vacancies was proposed. According to this model, the pyramidal spike shape growth of NiSi2 is enhanced by vacancies in silicon substrate generated by H ions projected during reactive ion etching (RIE). To confirm this model, Si ions were implanted prior to nickel deposition instead of RIE process, and the vacancies with the same depth in silicon substrate as those caused by H+ ions during RIE were generated. The Rs increase of NiSi was successfully reproduced by this Si ion implantation technique. Then, it is concluded that pyramidal spike growth of MS12 is caused by the vacancies generated by H ion projected during RIE process before nickel silicidation.