Y. H. Ku

Silicided shallow junction formation by ion implantation of impurity ions into silicide layers and subsequent drive‐in

We have developed a technique for the fabrication of shallow, silicided n+−p and p+−n junctions with good electrical characteristics. The technique utilizes the ion implantation of dopants into silicide layers previously formed by ion‐beam mixing with Si ions and low‐temperature annealing, and the subsequent drive‐in of implanted dopants into the Si substrate to form shallow junctions. This technique can be applied to the fabrication of metal‐oxide‐semiconductor field‐effect transistor in a self‐aligned fashion and can have a significant impact on complementary metal‐oxide‐semiconductor devices.

Silicon epitaxial growth by rapid thermal processing chemical vapor deposition

High quality thin silicon epitaxial films have been grown on heavily doped p+ substrates using rapid thermal processing chemical vapor deposition with superior thickness and dopant profile control. The epitaxial growth kinetics have been studied by examining the dependence of growth rate on the deposition temperature, the volume percentage of SiH2Cl2, and the total gas flow rate. Submicron epitaxial layers with hyperabrupt dopant transition (<200 A/decade) and excellent crystalline perfection with low defect density have been obtained.

Metal‐oxide‐semiconductor characteristics of rapid thermal nitrided thin oxides

The electrical properties of thin nitrided oxide (∼100 A) formed by rapid thermal nitridation (RTN) in pure NH3 have been studied. It is found that the current‐voltage characteristic of RTN oxides follows a Fowler–Nordheim tunneling behavior with modifications caused by electron trapping processes at the oxide surface and interface. The trapping density is dependent on the RTN conditions. At the interface, both fixed charge (Nf) and interface state (Dit) densities exhibit turnaround phenomena when the RTN process proceeds. The maximum values of Nf and Dit at the turnaround points are lower for the higher temperature RTN, suggesting a viscous flow related strain relieving mechanism associated with RTN of thin oxides. Films with superior endurance behavior (QBD=20.4 C/cm2 compared with QBD=5.1 C/cm2 of thermal oxide under 10 mA/cm2 constant current stress) have been obtained by RTN at 1000 °C, 10 s.

Stable, self‐aligned TiNxOy/TiSi2 contact formation for submicron device applications

The formation of the TiNxOy/TiSi2 bilayer on Si by rapid thermal nitridation of titanium silicide in NH3 has been studied. The chemical stability in dilute HF and the effectiveness of TiNxOy on TiSi2 as a diffusion barrier for Al are discussed. The results show that this bilayer has good chemical stability in dilute HF at least for 60 s and Al/TiNxOy/TiSi2/Si is thermally stable up to 500 °C for 30 min sintering.

Shallow, silicided p+/n junction formation and dopant diffusion in SiO2/TiSi2/Si structure

Shallow silicided p+/n junctions have been formed by implanting boron ions into titanium disilicide layers and the subsequent drive‐in of the implanted boron into the Si substrate by rapid thermal annealing (RTA). Results of boron diffusion in titanium disilicide layer, its segregation at both silicide/Si and oxide/silicide interfaces, and the junction quality are presented. The precipitation of boron at the SiO2/TiSi2 interface is identified for the first time in the form of B2O3. p+/n diodes and short‐channel metal‐oxide‐semiconductor field‐effect transistors with good electrical characteristics have been fabricated using doped silicide technology.

Suppression of lateral Ti silicide growth by ion beam mixing and rapid thermal annealing

One of the most important issues in the self‐aligned silicide technology has been lateral silicide formation over the sidewall oxide spacers. In this work, the lateral silicide growth has been considerably suppressed by the use of ion beam mixing and rapid thermal annealing. Metal‐oxide‐semiconductor transistors fabricated using this technology show good electrical characteristics with negligible conduction between gate and source/drain electrodes.

Selective epitaxial growth by rapid thermal processing

Rapid thermal processing chemical vapor deposition was employed for selective epitaxial growth of silicon. Defect‐free epitaxial islands were grown into oxide windows with 〈110〉 sidewall orientation on (100) silicon substrates. The effects of growth temperature on the degree of faceting have been studied. The hydrogen prebake temperatures as low as 1000 °C have proven to be sufficient for high quality Si deposition without sidewall oxide undercutting.

Formation Of Shallow Junctions With TiN x O y /TiSi 2 Ohmic Contacts For Self-Aligned Silicide Technology

The formations of TiNx0y/TiSi2 bilayer on Si by rapid thermal nitridation of titanium silicide in NH3 as well as p+/n shallow junction using doped silicide technique have been studied. Results of the chemical stability of TiNx0v/TiSi7/Si in dilute HF, the effectiveness of TiNx0, on TiSi2 as a diffusion barrier Mr Al boron diffusion in Si02/TiSi,2/Si structure, the surface dopant concentration at the TiSi7/Si interface, and the junction quality are presented. It is found that TiNx0y/TiSi2 bilayer has good chemical stability in dilute HF for 60 sec and acts as an effeentive contact barrier between Al and Si substrate up to 500°C, 30 min. Shallow p±n junction with high boron concentration at the TiSO/Si interface has been formed. P-1-/n diodes and p-channel LDD MOSFETs fabricated using this technology show good I-V characteristics with a reverse leakage current on the order of 10-9A/cm.

Self-aligned TiNxOy/TiSi2 contact formation

Abstract Bilayers of TiN x O y /TiSi 2 have been formed successfully on silicon as low resistive contacts as well as diffusion barriers during self-aligned silicide processing by direct rapid thermal nitridation of TiSi in an NH 3 ambient. The formation of TiN x O y is due to the reaction among titanium atoms in the silicide layer, nitrogen atoms which decompose from NH 3 , and oxygen atoms. The oxygen in the TiN x O y layer has been identified in the form of a TiO phase which can suppress aluminium diffusion during sintering of the Al/TiN x O y /TiSi 2 structure, making the bilayer an effective diffusion barrier between aluminium and the silicon substrate. The growth of the TiN x O y layer can be controlled by the annealing temperature and/or time through the nitridation of TiSi 2 . This bilayer can have a low sheet resistance of 1.25–2.5 Ω/□ with a controlled thickness ratio of TiN x O y /TiSi 2 . The Al/TiN x O y /TiSi 2 /Si contact structure is thermally stable up to 500°C for 30 min sintering in forming gas. In addition, this bilayer has a good chemical stability in dilute HF for at least 60 s. Since TiN x O y /TiSi 2 is formed on source, drain and gate areas in a self-aligned fashion by two-step rapid thermal processing, this technique can easily be applied to submicron device fabrication.

Rapid Thermal Processing for Self-Aligned Silicide Technology

A self-aligned titanium silicide process which combines the use of ion-beam mixing and rapid thermal processing (RTP) has been developed for CMOS VLSI applications. Shallow silicided junctions are formed by implanting dopants into silicide layers previously formed by ion-beam mixing with Si ions and low temperature annealing, and the subsequent drive-in of the implanted ions into the Si substrate during high temperature RTP. In addition, the formation of TiN on TiSi 2 is achieved simultaneously during this process as a diffusion barrier for Al metallization. Short-channel MOS transistors with SALICIDE structure have been successfully fabricated and tested. Results of the impurity diffusion in silicide layer, the impurity segregation at both silicide/Si and oxide/silicide interfaces, contact stabilit of Al/TiN/TiSi 2 structure, and device characteristics will be reported. Issues related to this process and its application to submicron device fabrication are discussed and foreseeable problem areas identified.