Susumu Sakuragi

Formation of ultra shallow p+/n junction in silicon using a combination of low-temperature solid phase epitaxy and non-melt double-pulsed green laser annealing

MOSFETs scaling-down is an effective way to attain high-performance CMOS operating with lower power and leakage current. However, short channel effects have become a serious problem due to the shortening of channel length. One of the promising methods to suppress this problem is by forming a shallow, highly doped and activated source/drain extension region. Fabricating ultra shallow p+/n junction is difficult due to the channeling of boron ions and anomalous boron diffusion during fabrication processes. A combination of Ge pre-amorphization implantation, low-energy boron implantation and two-step annealing, involving low-temperature solid phase epitaxy preannealing followed by non-melt laser annealing was used for forming ultra shallow p+/n junction in silicon. The physical relationship among the regrowth of implanted layer, boron activation and diffusion, and leakage current is investigated. We have succeeded in forming ultra shallow p+/n junction with junction depth of 8 nm and sheet resistance of 920 Ω/.

Formation of shallow p + /n junction in silicon by non-melt laser annealing

In this work, shallow p+/n junction was formed by annealing the implanted samples (prepared by Ge preamorphization implantation (Ge-PAI) and low energy B implantation) with non-melt laser annealing process using two different laser sources, i.e. excimer laser, KrF and green laser in order to compare the dopant diffusion, activation and regrowth of implanted layer. Experimental results show that remarkable boron diffusion occurred during annealing of the samples subjected to KrF laser annealing with a very short annealing time. Only slight diffusion of boron at the tail region is observed in the samples subjected green laser annealing. We considered that the penetration depth and pulse duration are the important factors that may cause the difference in boron diffusion during annealing process.

Ultra‐Shallow P+/N Junction Formation in Si Using Low Temperature Solid Phase Epitaxy Assisted with Laser Activation

A combination of Ge pre‐amorphization implantation (Ge‐PAI), low‐energy B implantation and laser annealing is a promising method to form highly‐activated, abrupt and ultra‐shallow junctions (USJ). In our previous report of IIT 2006, we succeeded in forming pn junctions less than 10 nm using non‐melt double‐pulsed green laser. However, a large leakage current under reverse bias was observed consequently due to residual defects in the implanted layer. In this study, a method to form USJ is proposed: a combination of low‐temperature solid phase epitaxy and non‐melt laser irradiation for B activation. Ge pre‐amorphization implantation was performed at energy of 6 keV with a dose of 3×1014/cm2. Then B implantation was performed at energy of 0.2 keV with a dose of 1.2×1015/cm2. Samples were annealed at 400 °C for 10 h in nitrogen atmosphere. Subsequently, non‐melt laser irradiation was performed at energy of 690 mJ/cm2 and pulse duration of 100 ns with intervals of 300 ns. As a result, USJ around 10 nm with bet...

A defect behavior in boron shallow junction formation of Si under low-temperature pre-anneal and non-melt-laser anneal

Physical relationship among regrowth of damaged layer, dopant activation and dopant diffusion has been investigated in the formation of boron shallow junction of Si under low-temperature pre-annealing (PA) and non-melt laser annealing (LA). The degree of crystal regrowth was adjusted with pre-annealing time. It is clarified that the regrowth of amorphous Si layer up to the junction depth has an important key to realize the low leakage current and to suppress the unnecessary B diffusion after LA.

Diffusion-less ultra-shallow p + /n junction formation in Si using low-temperature solid phase epitaxy and non-melt laser annealing

Formation of ultra-shallow p+/n junction has been performed with the combination of low-temperature solid phase epitaxy and non-melt laser annealing. The former is aimed for improving crystallinity of junction region and the latter for activating implanted B ions. After pre-amorphization implantation of Ge, B ion implantation was performed at energy of 0.2keV with a dose of 1.2×1015/cm2. With adequate conditions, the junction depth around 8nm with sheet resistance of 920 Ω/□ is successfully formed in non-melting state. B dopant profile is kept almost with the as-implanted profile. In addition, the junction leakage current at reverse bias decreases dramatically with low-temperature solid phase epitaxy due to the reduction of residual defects.

Formation of ultrashallow junctions less than 10nm with the combination of low energy B ion implantation and laser annealing

Formation of ultrashallow active junctions will be required in keeping the ongoing miniaturization of ULSIs. We reported the formation of p+/n ultrashallow junctions less than 10nm with the combination of low energy B ion implantation and non‐melt laser annealing. First a Ge pre‐amorphization implant was performed at energies of 3 keV, 6 keV with a dose of 3E14 /cm2. After the pre‐amorphization implant, a B implant was performed at 0.2 keV and 0.3keV with doses of 8E14 /cm2 and 1.2E15 /cm2. Double‐pulsed laser annealing was adopted at annealing process. B depth profiles are measured with SIMS analysis. In case of 0.3 keV B I/I with 3 keV Ge pre‐amorphization, ultrashallow junctions less than 10nm was successfully formed with the double‐pulse laser irradiation of 760 mJ/cm2. A reasonable sheet resistance of ∼550 Ω/□ was obtained in such a ultrashallow junction.

Strongly (111) Oriented Metallization by Ion Plating Method

We have succeeded in the synthesis of strong Cu(111) textured films by means of the novel ion plating method(URT-IP). This URT-IP method combines the Cu deposition with the surface cleaning (self-cleaning). In the Cu film synthesis, the cations play a main role: the self-cleaning of underlying Cu seed and TaN barrier surfaces at the first stage of Cu deposition and the promotion of (111) texture. The two growth processes dependent on underlying materials cause the strong (111) orientation; the epitaxial growth on the same (111) oriented underlayer and the promotion of thermodynamically stable (111) texture on the amorphous underlayer. The in-situ Ar + cleaning of underlayer surfaces by the URT-IP improves the (11) orientation to be much stronger. The URT-IP method is applied also to the synthesis of strong Pt(111) textured films with the same fcc system.