Chie Hongo

Effects of nitrogen in HfSiON gate dielectric on the electrical and thermal characteristics

The effects of the nitrogen in the HfSiON gate dielectric on the electrical and thermal properties of the dielectric were investigated. It is clearly demonstrated that nitrogen enhances the dielectric constant of silicates. High dielectric constants of the HfSiON are maintained and boron penetration is substantially suppressed in the HfSiON during high temperature annealing. These properties are ascribed to the homogeneity of the bond structure in the film containing nitrogen through high temperature annealing.

Junction Leakage Generation by NiSi Thermal Instability Characterized Using Damage-Free n+/p Silicon Diodes

Using n+/p junctions formed by solid phase diffusion, a clear correlation between junction leakage and NiSi thermal instability was readily established. After forming an NiSi layer on damage-free junctions, various post-annealing processes at around the silicidation temperature were applied. A consistent and systematic rise of the leakage level was observed with the increase of the annealing time and the temperature. The migration of the released Ni atoms away from the NiSi layer, the subsequent clustering of the migrant Ni atoms, and the eventual formation of generation-recombination centers deep inside the Si substrate were identified as the basic components of the principal leakage mechanism. Detailed analysis of the thermally stimulated ingressive movement of the leakage-depth profiles revealed a substantial Ni burst at an early stage of annealing. This anomalous Ni burst imposes severe restrictions on junction shallowing for NiSi technology and sets a strict upper limit on the allowable process temperature for effective leakage suppression.

Thermally stable ultra-thin nitrogen incorporated ZrO/sub 2/ gate dielectric prepared by low temperature oxidation of ZrN

Ultra-thin nitrogen incorporated ZrO/sub 2/ (ZrON) film is successfully prepared by low temperature oxidation of ZrN. Capacitance equivalent thickness (CET) of 15 /spl Aring/ with Jg=1 mA/cm/sup 2/@ Vg=-1 V is demonstrated. There is no increase in CET up to 1000/spl deg/C. Silicide formation at poly-Si/ZrO/sub 2//Si stack at high temperature annealing is also inhibited. In addition, the boron penetration from p+ poly-Si to Si substrate is substantially suppressed.

Accurate SIMS depth profiling for ultra-shallow implants using backside SIMS

We studied accurate depth profiling for ultra-shallow implants using backside SIMS. In the case of measuring ultra-shallow profiles, the effects of surface transient and knock-on are not negligible. Therefore, we applied backside SIMS to analyze ultra-shallow doping to exclude these effects. Comparing the SIMS profiles of surface-side and those of backside, backside profiles show a sharper ion implantation tail than surface-side profiles. Furthermore, backside SIMS profiles show almost no dependence on primary ion energy. This indicates that backside SIMS provides sharp B profiles suitable for analyzing ultra-shallow implants, using higher primary ion energy in comparison with implantation energy. The backside SIMS technique has a good potential to be used for next generation devices.

Degradation mechanism of HfSiON gate insulator and effect of nitrogen composition on the statistical distribution of the breakdown

We intensively investigate the degradation mechanism of HfSiON during constant voltage stress. It is found that unstable trap-sites in the HfSiON play a significant role in the conduction path creation. We also find Weibull slopes increase and the statistical fluctuation of post-breakdown conductance is suppressed with increasing nitrogen concentration of the film, probably due to the improved homogeneity of the HfSiON microstructure.

Intrinsic Junction Leakage Generated by Cobalt In-Diffusion during CoSi2 Formation.

Using solid phase diffusion, damage-free n+/p junctions are fabricated to investigate intrinsic junction leakage induced by CoSi2 formation over them. With finely adjusted junction depth, xj, the first clear and systematic investigation is successfully conducted. Leakage generation with the shallowing xj proceeds uniformly, maintaining a tight ensemble distribution. Cobalt in-diffusion deep inside the silicon substrate and resultant generation-recombination (GR) center formation are suspected to be the primary causes of the intrinsic leakage. An anomalously large cross section of the GR centers indicates cobalt clustering as a physical origin of the gap states. Caution is advised regarding the cobalt inward migration, which could threaten the realization of future metal-insulator-silicon devices.

Systematic Investigation of Leakage Suppression by Pre-Silicide Implantation for CoSi2 Formation on Shallow n+/p Si Diodes

Using simple and damage-free n+/p Si diodes, a sensitive and comparative investigation is conducted on the suppression of CoSi2-induced leakage by ion implantation just before silicidation (pre-silicide ion implantation: PSII). Avoiding high dose implantation, junctions are formed by solid phase diffusion. These junctions allow basic and systematic monitoring of PSIIs intrinsic ability to suppress leakage. It is revealed that PSII suppresses junction leakage uniformly without causing any silicide spikes. It is also confirmed that PSII substantially reduces cobalt in-diffusion. Moreover, leakage suppression strongly depends on the element being implanted, i.e., As-PSII is found to be greatly superior to Ge-PSII. Furthermore, it is discovered that the presence of oxygen facilitates this advantage of arsenic. Combining these two factors, i.e., by As-PSII through an oxide, leakage suppression up to 4 orders of magnitude is attained.

Quantitative secondary ion mass spectrometry analysis of impurities in GaN and AlxGa1−xN films using molecular ions MCs+ and MCs2+

Abstract In SIMS analysis of GaN and AlxGa1−xN films, MCs+ and MCs2+ ion detection (M is the element to be analyzed) was investigated under Cs+ bombardment. The MCs2+ ions have a larger ion yield than the MCs+ ions when M is one of electronegative ions. Application of these molecular ions to SIMS analysis has made it possible to detect electropositive and electronegative elements in a single analysis run. Further, these molecular ions are useful to minimize the matrix effect in AlxGa1−xN films, with x ranging from 0 to 0.17. The formation mechanism of the MCs+ and MCs2+ ions can also be postulated by comparing the useful yield of these molecular ions and that of single (negative and/or positive) ions. These molecular ions are assumed to be produced mainly by recombination processes in which sputtered neutral species (M and/or MCs) combine with Cs+ ions.

Mechanism of the Suppression of Zr Silicide Formation in Poly-Si/ZrON/ZrSiON/Si Structure

In this paper, the mechanisms of the suppression of Zr-silicide formation in poly-Si/ZrON/interfacial-layer/Si structure at 1000°C annealing are discussed in detail. It was demonstrated that gaseous SiO desorption, which played a dominant role in the silicide formation in the case of the ZrO 2 /SiO 2 /Si, was completely inhibited in the ZrON/interfacial-layer/Si structure. In addition, we have found that an ultrathin interfacial SiON layer between poly-Si and ZrON stabilized the interface. Consequently, we concluded that the effective nitrogen incorporation into top/bottom interfacial SiON layers with our process was responsible for the superior thermal stability of the stack.