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

Abstract

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.

Leakage Reduction by Thermal Annealing of NiPtSi Silicided Junctions and Anomalous Grain-Incompatible Pt Network

“…This finding indicates a common origin of the thermally induced leakage irrespective of Pt addition (i.e., an initial burst or the fast infiltration of atomic Ni and its subsequent rapid coalescence into leakage-generating and slowly diffusing clusters). 2) Since the basic formulation of the leakage generation dynamics is now established, for complete characterization of the effectiveness and limitation of Pt addition against heat, the ingression kinematics of the leakage depth are also investigated at 650 and 700 C. Because the generation of thermally induced leakage can be described by the two above-identified phenomenological parameters (i.e., the effective diffusion coefficient and the amount of initial burst), these values are plotted as a function of annealing temperature. Figure 5 shows plots of the effective diffusion coefficient of NiPt(10%)Si junctions as a function of the inverse of the annealing temperature.…”

“…Those of pure NiSi junctions in ref. 2 are also plotted for comparison. Figure 6 shows the amount of initial burst as a function of temperature for NiPt(10%)Si junctions.…”

“…2) The emergence of the initial leakage is specific to p þ /n junctions. This suggests that the availability of Si interstitials or vacancies may not be sufficient to form leakage-generating sources on their own.…”

“…1) Recently, however, an in-depth study of thin NiSi films has revealed undesirable thermal instability and associated leakage generation on shallow junctions even during thermal processing at 500 C (i.e., a typical temperature for interlayer formation by chemical vapor deposition). 2) Since such low-temperature intolerance significantly impairs device manufacturability, a way of stabilizing NiSi films against heat must be devised.…”

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

“…On the other hand, to achieve a successful process for high-performance and highly-reliable complementary metal-oxide-semiconductor (CMOS) devices, the Ni silicide formation process is one of the most difficult processes, because its formation mechanism is not well known. Therefore, it is important to understand the crystalline microstructure of Ni silicide in advanced CMOS devices since they have a serious influence on junction leakage-current and source drain leakage-current [2]- [3]. In addition, the crystal phase of Ni silicide influences the resistance value which depends on process conditions such as the annealing temperature [4]- [5].…”