Sungkweon Baek

Sub-15 nm n+/p-germanium shallow junction formed by PH3 plasma doping and excimer laser annealing

An n + /p germanium (Ge) ultrashallow junction formed by PH 3 plasma doping (PLAD) and KrF excimer laser annealing is demonstrated. In order to improve the n-type dopant activation without significant diffusion in the n + /p-Ge junction, we applied laser annealing on the PLAD samples. Compared with rapid thermal annealing (RTA), the laser annealing yielded shallower junction depth (∼15 nm) with low sheet resistance and comparable leakage current characteristics in the Ge n + /p junction. Therefore, PLAD with laser annealing can be considered as an alternative method for fabricating future Ge metal-oxide-semiconductor field-effect-transistors.

Effect of low-temperature preannealing on laser-annealed p+/n ultrashallow junctions

The effect of low-temperature preannealing on ultrashallow p+/n junctions was examined. An ultrashallow junction was formed by means of B2H6 plasma doping at an energy of 500 V. The junction was activated by low-temperature (300–500 °C) annealing, followed by laser annealing. Compared with control samples which were not preannealed, low-temperature preannealing significantly improves junction characteristics, resulting in a reduction in junction depth and a lower leakage current density. A cross-sectional transmission-electron-microscopy analysis confirmed the lower defect density, which explains the lower leakage current. By optimizing the process conditions, excellent electrical characteristics of the p+/n junction, i.e., a junction depth of 28 nm and a sheet resistance of 250 Ω/sq, can be obtained.

Highly thermal robust NiSi for nanoscale MOSFETs utilizing a novel hydrogen plasma immersion ion implantation and Ni-Co-TiN tri-layer

In this letter, hydrogen plasma immersion ion implantation (H PIII) with Ni-Co-TiN tri-layer is introduced for the first time to enhance the thermal stability of the Ni-silicide for nanoscale CMOS technology. The Ni-silicided poly-Si gate and source/drain showed stable sheet resistance in spite of 650/spl deg/C, 30 min post-silicidation annealing. The junction leakage current is even improved a lot without degradation of device performance using the proposed method.

Characteristics of heavily doped p+/n ultrashallow junction prepared by plasma doping and laser annealing

High quality p+∕n ultrashallow junctions were fabricated by high dose plasma doping and two step annealing involving low-temperature furnace annealing and excimer laser annealing. Without a preamorphization process, laser annealing is effective in terms of activation and annealing. Meanwhile, the junction depth can be controlled by the low-temperature annealing process prior to the laser annealing. By combining low-temperature preannealing and laser annealing, ultrashallow (junction depth ∼22nm), low sheet resistance (∼275Ω∕sq.), and a defect-free p+∕n junction can be obtained without preamorphization.

Antimony as a Proper Candidate for Low-Temperature Solid Phase Epitaxially Activated n + / p Junctions

Shallow, low-resistive n + /p junction was investigated for sub 100 nm metal oxide semiconductor field effect transistors (MOSFETs) using antimony and arsenic ion-implantation and low-temperature rapid thermal annealing. In contrast to As implanted junctions, Sb-doped specimens showed shallower junction depth, lower sheet resistance, and leakage current at low-temperature processing (600°C). The results indicated the superiority of antimony to arsenic as a proper dopant for low-temperature activated ultrashallow and low resistive source and drain extensions. Arsenic will not be a proper candidate because of higher sheet resistance, as a consequence of presence of inactive As-vacancy clusters, and higher leakage current for devices that should be fabricated at low temperature with implemention of high-K dielectric metal-electrode gate stacks in next generation MOSFETs.

Ultrashallow Arsenic n+/p Junction Formed by AsH3 Plasma Doping

We have investigated the ultrashallow n+/p junction formed by AsH3 plasma doping (PLAD) and the effect of hydrogen on dopant activation. Since hydrogen balance gas (99% H2) was used for AsH3 PLAD, the incorporation of a significant concentration of hydrogen resulted after PLAD. The incorporated hydrogen caused various problems, such as low dopant activation, high resistance, and high leakage current. These problems were traced to hydrogen-induced damage, which was confirmed by cross-sectional transmission electron microscopy (XTEM). Therefore, pre-annealing at low temperature, which can effectively reduce the undesired hydrogen effects, is a necessary step toward obtaining a high-quality, ultrashallow arsenic n+/p junction via AsH3 PLAD.

Bismuth ion-implanted solid-phase epitaxially grown shallow junction for metal–oxide–semiconductor field-effect transistors

A shallow, low-resistive solid phase epitaxially regrown n+∕p junction was investigated for sub-70 nm metal–oxide–semiconductor field-effect transistors (MOSFETs), using bismuth (Bi) ion-implantation and low temperature rapid thermal annealing. Bi-doped specimens showed a shallow junction depth of ∼15nm (at a background concentration of 5×1018cm−3), low sheet resistance, and leakage current at low temperature processing (700°C). The results indicated that Bi could be a proper dopant for low temperature activated source and drain extensions that are fabricated at low temperatures with the implementation of high-κ dielectric and metal–electrode gate stacks in next generation MOSFETs.

Characteristics of low-temperature preannealing effects on laser-annealed P/sup +//N and N/sup +//P ultra-shallow junctions

The low-temperature pre-annealing effects on ultrashallow junctions were investigated. p/sup +//n and n/sup +//p ultrashallow junctions were prepared by low energy B/sub 2/H/sub 6/ & PH/sub 3/ plasma doping (PLAD) and excimer laser annealing (ELA). For the p/sup +//n junction, the junction depth was reduced significantly with increasing the pre-annealing temperature from 300/spl deg/C to 500/spl deg/. For the n/sup +//p junction, the dopant deactivation with subsequent annealing was reduced from 60/spl sim/80% to 20/spl sim/40% by low-temperature pre-annealing. The significant improvements of ultrashallow junction characteristics were attributed to the reduction of point defects by low-temperature preannealing.

Effect of Low Temperature Annealing Prior to Laser Annealing of an Ultrashallow n + / p Junction

The effect of low temperature annealing prior to laser annealing on n + /p junction characteristics was investigated. A sample annealed at 400°C for 10 min before laser annealing showed a significant reduction in defect density which, in turn, improved junction characteristics such as low resistance, low junction leakage current, and less phosphorus deactivation during subsequent high temperature annealing. Cross-sectional transmission electron microscopy analysis confirmed that defects induced by plasma doping were effectively removed by preannealing followed by laser annealing. A preannealing prior to a laser annealing process represents a promising technology for future ultrashallow junction applications.

In-Depth Analysis of NBTI at 2X nm Node DRAM

An analysis on the degradation of DRAM performance caused by the NBTI degradation of p-MOSFET is first to be reported. To improve the NBTI immunity, three candidates are examined. First, minimizing Si-H bonds at Si/SiON interface through controlling the heat-budget at BEOL shows a promising result in NBTI lifetime, but it is not appropriate for DRAM process since it decreases the refresh time. Next, the buried SiGe channel p-MOSFET, which has 1.2 times higher NBTI immunity, is considered but difficult to adopt in DRAM peripheral circuit due to extra manufacturing cost. Finally, a deuterium annealing seems to be the right candidate for DRAM process since it improves the NBTI immunity without the refresh time penalty. This NBTI gain, however, varies depending on the amount of deuterium atom at Si/SiON interface and the probability of Si-D bond replacement with Si-H bond. Thus, selecting a right process sequence and an annealing condition is crucial.