Siegfried L. Maurer

Sharp Reduction of Contact Resistivities by Effective Schottky Barrier Lowering With Silicides as Diffusion Sources

An extremely low contact resistivity of 6-7 × 10^-9 Ω·cm² between Ni_0.9Pt_0.1Si and heavily doped Si is achieved through Schottky barrier engineering by dopant segregation. In this scheme, the implantation of B or As is performed into silicide followed by a low-temperature drive-in anneal. Reduction of effective Schottky barrier height is manifested in the elimination of nonlinearities in IV characteristics.

Activation of Implanted n-Type Dopants in Ge Over the Active Concentration of 1 × 1020 cm − 3 Using Coimplantation of Sb and P

One of the greatest challenges in fabricating a Ge-channel n-MOSFET is achieving a high n-type dopant activation within the source and drain regions. Conventional approaches to increase the electrically active doping level have been proven to be unsatisfactory, and typically the highest activation of n-type dopants is 4 × 10 19 cm -3 using phosphorus. This article describes a method to enhance the activation level of n-type dopants in Ge. Coimplantation of phosphorus and antimony leads to dopant activation over 1 X 10 20 cm -3 at 500°C. The enhancement of n-type dopant activation is attributed to reducing the implantation damage upon annealing due to increase in solid solubility of the dopants.

Lateral displacement induced disorder in L1 0 -FePt nanostructures by ion-implantation

Ion implantation is a promising technique for fabricating high density bit patterned media (BPM) as it may eliminate the requirement of disk planarization. However, there has not been any notable study on the impact of implantation on BPM fabrication of FePt, particularly at nano-scale, where the lateral straggle of implanted ions may become comparable to the feature size. In this work, implantation of antimony ions in patterned and unpatterned L10-FePt thin films has been investigated. Unpatterned films implanted with high fluence of antimony exhibited reduced out-of-plane coercivity and change of magnetic anisotropy from perpendicular direction to film-plane. Interestingly, for samples implanted through patterned masks, the perpendicular anisotropy in the unimplanted region was also lost. This noteworthy observation can be attributed to the displacement of Fe and Pt atoms from the implantation sites to the unimplanted areas, thereby causing a phase disorder transformation from L10 to A1 FePt.

Magnetic and structural properties of CoCrPt–SiO2-based graded media prepared by ion implantation

The magnetic and structural properties of graded media fabricated by ion implantation of nitrogen (14 N+), oxygen (16O+), and cobalt (59Co+) ions in the CoCrPt–SiO2 recording layer of prototype disk have been studied. Ion implantation of the species was controlled at the atomic scale to fabricate the graded media. Magnetometric measurements indicated that the coercivity was reduced with an increasing dose of the implanted species. The observation of an increase in magnetic domain size has been attributed to the reduction in magnetocrystalline anisotropy energy, which is desirable for achieving graded media. The study indicates that the magnetic properties can be tailored by the appropriate selection of the implantation dose and species.

First-Order Reversal Curve Investigations on the Effects of Ion Implantation in Magnetic Media

Ion implantation of different ion species of varying mass on magnetic recording media was investigated. Except for helium (4He⁺) and cobalt (59Co⁺) ions, all the other ions showed reduction in saturation magnetization (M_s). In fact, M_s was reduced to ~ 0 emu/cc at a fluence of 2 × 10¹⁶ and 5 × 10¹⁶ ions/cm² for antimony (121Sb⁺) and argon (40Ar⁺ ) ions, respectively. First-order reversal curves (FORC) showed a reduction in the switching field and distribution as the fluence of the implanted species increased. In addition, the magnetostatic interactions which were present in the media were found to be overwhelmed by an increase in exchange interaction as fluence increased. It was noticed that the heavier the implanted ion, the lower was the lateral range and straggle. A negative correlation was also observed between the straggle of the implanted species and the increased exchange interaction. This observation is expected to play a very crucial role in high-density patterned media fabrication.

Ion Implantation Challenges for Patterned Media at Areal Densities Over 5 Tbpsi

Ion implantation of lighter (4He+) and heavier ion species (121Sb+) was studied to investigate their suitability in fabricating bit patterned media (BPM) for areal densities ≥ 5 Tbpsi. Conventional CoCrPt- SiO2 and the next generation high-anisotropy L10 FePt media were employed to understand the mass-dependent lateral straggle of the ions. First-order reversal curve measurement for CoCrPt- SiO2 media revealed an increase in exchange interaction in the implanted films with the increasing fluence. Interestingly, there was an order-disorder transformation of the phase for L10 FePt media upon implantation. Implantation using lighter ions resulted in a larger lateral straggle. This lateral movement of ions from the unmasked to masked regions during BPM fabrication will, furthermore, impede the process of bit isolation. In contrast, lateral straggle was reduced for heavier ions. However, this was achieved at the expense of the diffusion of host atoms displaced from their lattice positions which caused a reduction of anisotropy even in the unimplanted regions. Therefore, the requirement to strike a balance between the lateral straggle of the implanted species and the movement of host atoms to accomplish ultra-high densities in implantation-assisted-BPM recording is reported as a challenging problem.

Effective Schottky Barrier lowering for contact resistivity reduction using silicides as diffusion sources

In this work we present a potential solution for forming ultra-shallow junctions with extremely low contact resistivities in which dopants are implanted into silicides and diffused to the semiconductor interface using low temperature anneals. Conventional silicide process requires a fine tuning of silicide thickness and deep source/drain doping profile to achieve low contact resistance and low source/drain diffusion sheet resistance. With the silicide implantation approach, we show that they can be engineered independently, providing a larger design space for the reduction of total external resistance. We demonstrate that contact resistance for NiPt silicide can be significantly reduced down to 7×10−9 Ω-cm2 for p+ Si and 6×10−9 Ω-cm2 for n+ Si by using Schottky Barrier Height (SBH) tuning through the implantation of B/As into pre-formed NiPtSi followed by low-temperature drive-in annealing (see Fig. 1 for the process flow). Moreover, we find that the same low contact resistance can be achieved for both heavily and moderately doped junctions, which grants an additional degree of freedom in junction design to reduce series resistance. With this technology, the ultra-shallow junction process can be simplified to the formation of ultra-thin silicide followed by shallow implantation and low temperature RTA (<600C) without any demand of ultra-high thermal budget for the S/D doping. Implantation into silicides, as an alternative to surface implantation prior to silicidation, prevents silicide morphology degradation (encroachment, roughness, or inverted pyramids) induced by extra defects from the surface implantation.

All-Wet, Metal-Compatible High-Dose-Implanted Photoresist Strip

An all-wet process based on a novel chemistry has been developed to enable the removal of high-dose implanted photoresist in the presence of exposed metal layers and other materials typical of advanced gate stacks.