Hei Wong

Excess silicon at the silicon nitride/thermal oxide interface in oxide–nitride–oxide structures

The chemical composition and structure of Si3N4/thermal (native and wet) SiO2 interface in oxide–nitride–oxide structures are studied by using secondary ion mass spectroscopy, electron energy loss spectroscopy (EELS) and Auger electron spectroscopy (AES) measurements. EELS and AES experiments show the existence of excess silicon at the Si3N4/thermal SiO2 interface. Excess silicon (Si–Si bonds) at Si3N4/SiO2 interface exists in the form of Si-rich silicon oxynitride. Numerical simulation of the Si–Si bond’s electronic structure by using semiempirical quantum-chemical method (MINDO/3) shows that Si–Si defects act as either electron or hole traps. This result explains the abnormally large electron and hole capturing at this interface reported earlier.

Conduction mechanisms in MOS gate dielectric films

Abstract This paper reviews the conduction mechanisms in the gate dielectric films of MOSFETs for VLSI and ULSI technologies. They include Fowler–Nordheim tunneling, internal Schottky (or Pool–Frenkel) effect, two-step (or trap-assisted) tunneling, shallow-trap-assisted tunneling, and band-to-band tunneling. The current transport in the gate dielectric films is manly controlled by film material composition, film processing conditions, film thickness, trap energy level and trap density in the films. In general, for a given gate dielectric film, the current transport behaviors are normally governed by one or two conduction mechanisms.

Defects in silicon oxynitride gate dielectric films

Abstract As the aggressive scaling of the metal-oxide-semiconductor structure continues, new reliability challenges in gate dielectric materials now came across as the gate dielectric thickness will be further down scaled to its technological constraint (

Low-frequency noise study in electron devices: review and update

Abstract Low-frequency noise or flicker noise has been found in many systems and has become a hot research topic for more than eight decades. It was believed that there exists a common origin of this kind of noise for different systems. The common origin theories were shook as more experiments on electron devices were conducted. For electronic system, it is easier to produce samples with different noise behaviors via different fabrication processes, measurement conditions such as temperature, stressing, biasing etc. More and more studies suggest that if there is a common regime for the low-frequency noise, it must be mathematical rather than physical ones. These mathematical processes give rise to 1/f spectrum could be due to the distribution of time constant in spatial or energy-wise and the non-linear transformation of Gaussian signal. This paper presents a historical review on the development of low-frequency noise study in electron devices and the recent progresses in the understanding and modeling are updated.

Short-range order in non-stoichiometric amorphous silicon oxynitride and silicon-rich nitride

By de-convoluting the Si 2p X-ray photoelectronic spectra, it was found that the short-range order in amorphous silicon oxynitride ðSiOxNyÞ films with different compositions can be quantitatively described by the random bonding model. In this model the SiOxNy consists of five types of randomly distributed tetrahedra and it indicates that metal– oxide–semiconductor transistor with this gate dielectric will not result in any gigantic potential fluctuation in the conduction channel. On the contrary, the structure of silicon-rich silicon nitride SiNx can only be described by the random mixture model where the local composition fluctuations in this film will result in gigantic potential contravariant fluctuation. 2002 Elsevier Science B.V. All rights reserved.

Preparation of Thin Dielectric Film for Nonvolatile Memory by Thermal Oxidation of Si-Rich LPCVD Nitride

In this work, we develop methods for fabricating high quality dielectric films for nonvolatile memory applications. Oxide/Si-rich nitride/oxide structures are fabricated where the Si-rich nitride layer was deposited by the low pressure chemical vapor deposition (LPCVD) technique, With a Si-rich nitride layer, the Fowler-Nordheim tunneling voltage can be cut down to 3 V for oxide thickness of about 100 A. By reoxidizing the Si-rich nitride layer, secondary ion mass spectroscopy study reveals that the hydrogen content of nitride film and its interface can be reduced by more than 40%. With this method, high nitrogen content oxynitride and smoother oxynitride/oxide interfaces result and the interface charge trapping can be improved remarkably.

Recent developments in silicon optoelectronic devices

Abstract Due to the rapid growth of the internet and multi-media communication networks, there are urgent needs and tremendous commercial values in the development of optoelectronics integrated circuits (OEICs). This work reviews the recent developments and the prospect of silicon-based integrated optoelectronic circuits (Si-OEICs). The technological aspects of porous silicon and oxynitride devices for integrated optoelectronic applications are discussed. Some optoelectronic devices being realized with these technologies are described. Recent achievements indicate that the present constraints for using Si-based materials in optoelectronics are mainly technological rather than physical. Once these technological difficulties are resolved, the realization and applications of Si-OEICs will grow rapidly.

Electronic structure of α-Al2O3: Ab initio simulations and comparison with experiment

Al2O3 films 150 Å thick are deposited on silicon by the ALD technique, and their x-ray (XPS) and ultraviolet (UPS) photoelectron spectra of the valence band are investigated. The electronic band structure of corundum (α-Al2O3) is calculated by the ab initio density functional method and compared with experimental results. The α-Al2O3 valence band consists of two subbands separated with an ionic gap. The lower band is mainly formed by oxygen 2s states. The upper band is formed by oxygen 2p states with a contribution of aluminum 3s and 3p states. A strong anisotropy of the effective mass is observed for holes: mh⊥* ≈ 6.3m0 and mh‖* ≈ 0.36m0. The effective electron mass is independent of the direction me‖* ≈ me⊥* ≈ 0.4m0.

Silicon integrated photonics begins to revolutionize

The advances in Si technology and the rapid growth of broadband communication via optical fiber allow silicon integrated photonics to begin revolutionizing the electronic devices, circuits, and systems. The pace of technological development has been recently speeded up. Using microfabrication technology we are now able to make waveguide structures and optical components from Si-based materials, such as silicon oxynitride or doped silica. Visible light can be obtained from Si-based materials such as Si quantum wire/dots and Si nanoclusters embedded in insulators. The remaining issues are to develop processes and device structures to make Si photonics economically viable with system and device performance comparable to their existing counterparts. Recent efforts have demonstrated that the light-emitting efficiency can be enhanced greatly and that the lasing effect is also possible with the nanostructures. The impact of these moves will be revolutionary. The successful development of Si integrated photonics will enable on-chip optical interconnects for future microprocessor and giga-scale circuits, chip-to-chip fiber interconnection and will greatly decrease the cost for fiber-to-home connection. This will be one of the major moves for the next technology revolution. The present article discusses some recent developments on these aspects.

XPS Study of the Bonding Properties of Lanthanum Oxide/Silicon Interface with a Trace Amount of Nitrogen Incorporation

Recently, both electrical and material properties of lanthanum oxide (La 2 O 3 ) have been found to significantly improve with a trace amount of nitrogen doping. This work conducted a detailed investigation on the nitrogen incorporation at the La 2 O 3 /Si interface by using X-ray photoelectron spectroscopy (XPS) and capacitance-voltage measurements. The process-dependent chemical bonding structures of Si, O, and La atoms at the interface were studied in detail. For samples annealed at 500°C and above, the interfacial metallic La-Si bonds were converted into La-N bonds, and some Si-O bonds were found at the interface. These effects resulted in a significant reduction in the interface trap density. The bulk properties of La 2 O 3 were also improved with the proposed technique as a result of the filling of oxygen vacancies with nitrogen atoms.