Sookap Hahn

Hydrogen introduction and hydrogen‐enhanced thermal donor formation in silicon

Hydrogen has been introduced from a rf plasma into Czochralski Si at 275 °C. Most of the hydrogen is trapped near the surface where it forms Si—H bonds, but a small fraction diffuses into the Si. This fraction enhances oxygen‐related thermal donor (TD) formation rates in a diffusionlike profile during subsequent furnace anneals between 350 and 400 °C. A hydrogen concentration that is only a few percent of the oxygen concentration is sufficient to enhance the TD formation rate, indicative of a hydrogen‐catalyzed process. Maximum concentrations for TDs after annealing at 400 °C exceed that for retained hydrogen. A mechanism of hydrogen diffusion through oxygen traps and correlated hydrogen‐promoted oxygen diffusion is proposed to explain the enhanced TD formation rates.

Depth Profiles for Hydrogen‐Enhanced Thermal Donor Formation in Silicon: Spreading Resistance Probe Measurements

Hydrogen enhancement of formation rates for oxygen-related thermal donors in Si has been investigated for dependence on: the source of hydrogen, hydrogen isotope, and exposure time and temperature. Hydrogen injection efficiency is an important variable and depth profiles are dependent upon the surface preparation of samples exposed in an electron cyclotron resonance plasma where ion energies are {<=}35 eV. Formation rates up to 2 {times} 10{sup 16} cm{sup {minus}3} at 400 C have been observed. A sublinear dependence of the donor formation rate on beam current under 50 keV ion implantation is interpreted as a competition between oxygen-hydrogen and hydrogen-hydrogen interactions. Dependence on isotope mass and on exposure time in the plasma indicates hydrogen is the diffusing species that determines the penetration depth for the enhanced donor formation. Peculiar box-like depth profiles and high formation rates near the advancing front produced in RF plasma exposures are suggestive of hydrogen accumulation near the advancing front. The temperature dependence for the penetration depth gives in activation energy of 1.5 {+-} 0.2 eV. This energy is attributed to trap-limited diffusion wherein hydrogen lowers the energy barrier for the oxygen motion necessary to form thermal donors.

Damage formed by ion implantation in silicon evaluated by displaced atom density and thermal wave signal

Damage formed by BF+2 and As+ implantations in Si was evaluated quantitatively. The density of displaced atoms (Dda) was determined from 1.5 MeV He+ Rutherford backscattering spectrometery. Dda increased from 4.7×1016 to 1.6×1017 cm−2 with the dose increased from 6.0×1013 to 1.3×1014 cm−2. However, Dda saturates at around 4×1017 cm−2 for all doses above 5×1014 cm−2. The thermal wave signal intensity shows the same dose dependence as Dda. This result shows that thermal wave signal intensity has a close relation with the density of displaced atoms formed by ion implantation. Therefore, quantitative damage monitorings can be achieved by thermal wave intensity measurements. Also, the variation of thermal wave signal intensity with ion implant energy was studied.

Study on surface photovoltage measurement of long diffusion length silicon: Simulation results

The limitations of surface photovoltage method (SPV), using the analytical solution for the minority‐carrier distribution, are studied in detail. The principal source of error in thin wafers of long diffusion length material is the back surface recombination. The possibility of measuring large diffusion lengths in a reliable manner is discussed. With proper back surface passivation, diffusion lengths as long as several times the sample thickness can be measured. Evaluation of minor amounts of iron contamination in p‐type material is possible even if the back surface recombination velocity is high, but a correction factor is required for the traditionally used relationship to convert the observed diffusion length change to iron concentration. The value of the correction factor varies between 1 and 1.5 for high back surface recombination velocity; the magnitude depends on the ratio between wafer thickness and the diffusion length of the minority carriers. The detection limit for iron is in the 109–1011 at/c...

Damage and RTA kinetics in Ar+ and Si+ ion-implanted CZ silicon characterized by thermal wave modulated optical reflectance

In this study, damage induced by Ar+ and Si+ ion implantation and its annealing behavior during rapid thermal annealing for 10 sec at temperatures between 575-1100°C were investigated by thermal wave modulated optical reflectance, deep level transient spectroscopy, reflection high energy electron diffraction, Rutherford backscattering aligned spectra and transmission electron microscopy. Our data show that (1) thermal wave signal and its variation with repect to rapid thermal anneal temperature strongly depend upon implant dose and anneal temperature; (2) both implant species induce four distinctive deep trap levels; (3) these traps evolve during rapid thermal annealing!; and (4) for the single Si+ ion implanted samples, the variation of total trap concentration with respect to rapid thermal anneal temperatures follows that of TW. However, in the case of Ar+ ion implanted samples, no apparent correlation between thermal wave signal and DLTS trap condition could be made.

Gate oxide integrity and minority‐carrier lifetime correlated with Si wafer polish damage

This study investigated the effects of Si wafer polish damage on the electrical performance and integrated circuits, using metal‐oxide‐semiconductor capacitors as the test structures. These test capacitors were fabricated with 100 or 250 A oxide layers thermally grown on wafers having varied polish‐damaged surfaces. Field‐dependent and time‐dependent breakdown data were measured and correlated with the surface polish quality as characterized by thermal wave (TW) modulated reflectance measurements. To study the effects of damage remaining in the silicon beneath the Si/SiO2 interface after the formation of the capacitors, the minority‐carrier lifetime was measured and also correlated with the TW values obtained on the starting (nonprocessed) wafer surfaces. The results of this study established that increased polish damage, indicated by higher TW values, adversely affects thin oxide breakdown integrity and reduces the minority‐carrier lifetime.

Os papéis da ciência dos materiais e da engenharia para uma sociedade sustentável

N ossa civilização entrou em uma nova era de materiais. Como está fartamente documentado em vários relatórios governamentais e acadêmicos, as sociedades avançadas em todo o mundo rapidamente adquirem habilidades sem precedentes no sentido de criar materiais projetados para satisfazer necessidades humanas. Em todo país, a qualidade de vida e segurança econômica e militar dependem cada vez mais da capacidade de sintetizar e processar materiais, de descobrir novos e de integrá-los em tecnologias de manufatura economicamente eficientes e ecologicamente seguras. Na verdade, sem os novos materiais e sua produção eficiente, não existiria o nosso mundo de equipamentos modernos, máquinas, computadores, automóveis, aeronaves, aparelhos de comunicação e produtos estruturais. Cientistas e engenheiros de materiais continuarão a estar na dianteira dessas e de outras áreas de ciência e engenharia a serviço da sociedade, à medida que conquistem novos níveis de entendimento e controle sobre os blocos básicos que compõem os materiais: átomos, moléculas, cristais e arranjos não-cristalinos.

Damage and its rapid thermal annealing kinetics in Ar+ ion implanted Cz silicon

Abstract In this study, damage induced by Ar+ ion implantation and its annealing behavior during rapid thermal annealing for 10 s at temperatures between 575–1100°C were investigated by thermal wave modulated optical reflectance, deep level transient spectroscopy, reflection high energy electron diffraction, Rutherford backscattering aligned spectra and transmission electron microscopy. Our data show that: (1) both implant dose and energy affect the nature of damage and its rapid thermal annealing behavior; (2) Ar+ ion implantation induces four distinctive deep trap levels; (3) these traps evolve during rapid thermal annealing; and (4) in the case of medium energy (100 keV) implanted Si samples, the damage anneals out from inside out whereas the high energy (1 MeV) ion implant damage anneals out from outside in.

Investigation of rapid-thermal-processing-induced defects in ion-implanted Czochralski silicon by the magic mirror method

In this study, 150 mm diameter p-type (100) silicon wafers (with no screen oxide) were implanted in a batch implanter with 5*1015 cm-2 of arsenic at 80 keV. After implantation the wafers were subjected to rapid thermal annealing for 10 s at temperatures: wafer warpage measurements, optical imaging inspection (magic mirror method), X-ray transmission topography and thermal wave modulated optical reflectance. This paper summarises the measured results of wafer defects and damage due to the rapid thermal processing.

Investigation of rapid thermal process-induced defects in ion-implanted Czochralski silicon

Rapid Thermal Processing (RTP) has shown promise as a tool that will reduce the thermal budget presently used in the manufacture of advanced ULSI devices. Because of the rapid rates of temperature rise and fall coupled with inherent system temperature non-uniformities of RiP systems plastic deformation has been identified to occur in RTP- processed wafers. Concern over these types of process-induced defects has brought about the identification of various methods of uniformity characterization of RiP-processed wafers. In this study 150 mm p-type wafers (with no screen oxide) were first implanted on a batch implanter with conditions of 5E15 of arsenic at 80 keY. After implantation the wafers were rapid thermally annealed for 10 seconds at the temperatures ranging from 900 to 1250 C. Each wafer was then measured by several techniques: wafer warpage measurements optical imaging inspection (magic mirror method) X-ray transmission topography and thermal wave modulated-optical reflectance. This presentation summarizes the measured results of wafer defects and damage due to the RTP processing. 1.