Koji Eriguchi

Comparison of thermal and plasma oxidations for HfO2/Si interface

Abstract The HfO2/Si interface stability has been investigated by using a rapid thermal annealing (RTA), an inductively coupled plasma (ICP) and a reactive sputtering, as a comparison of thermal and plasma oxidations of the Hf/Si interface. Reduction in both capacitance equivalent thickness (CET) and leakage current density (Jg) was difficult to be attained by the thermal oxidation since it accompanies the crystalline HfO2 with SiO2-like interface. Advantage is found for the plasma oxidation technique to oxidize Hf metal at low temperatures remaining the HfO2 in an amorphous phase with silicate interface. Reduction in both CET and Jg was attained by the plasma oxidation and a Hf metal pre-deposition technique.

Evaluation technique of gate oxide damage

Gate oxide damage by the plasma process is studied using test structures with various length antennas. It is shown that the gate oxide damage by the plasma process can be monitored quantitatively by measuring the charge to breakdown Q/sub BD/. From Q/sub BD/ measurements, it is found that degradation occurs in the duration of over-etching, not in main etching. The breakdown spot in the gate oxide is detected by the photon emission method. The breakdown caused by plasma damage occurs at the local oxidation of silicon (LOCOS) edge. LOCOS structure plays an important role for the degradation by plasma damage.<<ETX>>

Stress mode of gate oxide charging during the MERIE and the ICP processing and its effect on the gate oxide reliability

The gate oxide charging (stressing) mode during plasma processing was investigated from the experimental data of two TDDB measurements, Q/sub bd/ and t/sub bd/ testings and the gate current behaviour in t/sub bd/ testing after the plasma treatment and the post-process current injection (electrical stress). It was confirmed that in some cases the t/sub bd/, which determines the oxide lifetime under operating conditions, increases after the plasma treatments in both MERIE (magnetically enhanced RIE) and ICP processing.

Impacts of strained SiO/sub 2/ on TDDB lifetime projection

We clarify the effects of the strained-SiO/sub 2/ on the time dependent dielectric breakdown (TDDB) characteristics, the activation energy of the oxide breakdown and Weibull slope (/spl beta/) for the ultra-thin gate oxide. Considerations based on the extended-Stillinger-Weber potential model show that the built-in compressive strain in SiO/sub 2/ changes the statistical distribution of the Si-O-Si angle, leading to a decrease of T/sub pd/ and a spread of the distribution. The oxide breakdown tends to occur at the Si-O-Si network with a lower bond angle (/spl sim/115/spl deg/) for the 2 nm-thick SiO/sub 2//Si system.

A New Evaluation Technique Of Plasma-induced Si Substrate Damage By Photoreflectance Spectroscopy

In this study, the Si substrate damage induced by the O2 plasma exposure is investigated by photoreflectance (PR) spectroscopy for the first time. The PR signal intensity from the Si surface with the plasma exposure is found to decrease at a typical photon energy, although the Raman spectroscopy does not show an apparent change for the damaged samples. The decrease in the PR signal intensity is attributed to the penetration of oxygen into Si substrate which is considered to be the carrierrecombination center at the vicinity of Si surface. The effect of the plasma exposure on the Si band structure is also discussed on the basis of the PR spectroscopic method. particular, compound semiconductors, by measuring the change of the reflectance of a semiconductor surface potential induced by the field due to the optically generated carriers.[7][8] Since the wavelength in PR spectroscopy is usually in the visible range, the PR spectroscopy gives the information dominantly from the surface region of materials, by taking into account the skin depth of the incident light. Moreover, from the PR spectrum, the electronic state in the material is determined. The purpose of this paper is to apply the PR spectroscopy to the evaluation of the Si surfaces damaged by 02 plasma exposure, and to discuss on the obtained result, including the electrical characteristics.

Photoreflectance spectroscopic technique: a new model for estimation of plasma-induced defect density in Si substrate

In recent years, reactive ion etching (RIE) has been widely used in ULSI process technology. However, the Si surface exposure to plasmas during RIE causes the generation of defects or damage in the Si substrate due to the energetic ion bombardment and etching species penetration. This plasma-induced damage strongly affects ULSI device performance and reliability. Si substrate damage induced by CHF/sub 3/-CF/sub 4/-Ar plasma processing has been characterized by photoreflectance (PR) spectroscopy. Moreover, the damage induced by Ar plasma has been characterized in-situ in the processing chamber. Both of the PR signal intensities decrease with the plasma treatment. The decrease in PR signal intensity is attributed to the decrease in modulation due to the introduction of the charged defects that changes the space charge density of the depletion layer. We propose a new model for the estimation of the defect density induced by plasma exposure. Using this model based on PR spectroscopy, the defect density can be quantitatively calculated.

Optical characterization of antenna-area-dependent gate oxide charging damage in MOS capacitors by photoreflectance spectroscopy

Thin gate oxide charging damage has been studied by photoreflectance (PR) spectroscopy in MOS structure samples. Antenna-area-dependent oxide charging damage such as the generation of SiO/sub 2//Si interface states as well as that of electron trap sites in the oxides, has been also addressed by the decrease of the PR peak signal intensity from MOS capacitors, and also confirmed by the capacitance-voltage (C-V) characteristics.