File Name: spectroscopic ellipsometry principles and applications hiroyuki fujiwara .zip
Nature of Radiation Measured: This category of spectroscopy depends on the physical quantity measured. The application of spectroscopic techniques to the detection and identification of explosive materials is of considerable importance in forensic investigations. Introduction to nonlinear optical spectroscopic techniques for investigating ultrafast processes Eric Vauthey Dpt. Among the widely used of these different types of nanoparticles in investigations to control a lot of fungal plant pathogens, there are different methods to prepare each type, also many methods and techniques followed to evaluate it as control agents against some plant pathogens.
Atomic layer deposition ALD is a special kind of chemical vapor deposition, which is mainly characterized by a self-terminating surface coverage in the progress of the two distinctive reaction steps.
As a result, ALD enables a highly conformal coating of complex three- dimensional-shaped surfaces including a unique film thickness control in the sub-nanometer range. Objectives: As a result of the student research project, the capability of in situ SE is to be demonstrated with respect to a detailed characterization of the Al2O3 ALD model process, comprising a comprehensive study of various process parameter interdependencies.
Planning of experiments 3. Familiarizing with the FHR ALD tool, including the in situ ellipsometer as well as a selection of direct surface analysis techniques for referencing purposes 4.
Conducting and minuting the planned experiments; evaluating the acquired ellipsometric spectra as well as referencing measurements 5. Interpreting, formulating and discussing the received results in writing Handed over on: October 16, Supervisors Responsible professor. I also declare that this project report was independently written by me. And I have used no resources and quotations other than those specified in this report.
Woollam Co. Atomic Layer Deposition ALD is a special type of Chemical Vapor Deposition CVD technique based on self-terminating sequential gas reactions for a conformal and pre- cise growth down to few nanometers range. Ideally due to the self-terminating reac- tions, ALD is a surface-controlled process, where process parameters other than the choice of precursors, substrates, and deposition temperature have little or no influence [Puurunen P.
In spite of the numerous applications of growth by ALD, many chemical and physical processes that control ALD growth are not yet sufficiently understood [Jaebum P. In-situ SE is very promising technique that allows the time- continuous as well as time-discrete measurement of the actual growth over an ALD process time. The following ALD process parameters were varied and their inter-dependencies were studied in detail: exposure times of precursor and co-reactant as well as Argon purge times, the deposition temperature, total process pressure, flow dynamics of two different shower head designs.
Al2O3 has relatively high melt- ing of 2, K. It is resistant to attack by many chemicals and gases. It is also a good electrical insulator but has a very good thermal conductivity[ Patnaik , p. In thin film technology Al2O3 is deposited in its amorphous phase. Al2O3 is a very important material in high performance electronics[ Perrella , p. Al2O3 is used in various fields of microelectronic industry.
It is used as a gate-oxide in transistors, dielectric in dynamic Random Access memory DRAM , fast computing applications and in making passive components. Al2O3 comes under high-k category which makes it suitable for gate dielectric in metal oxide semiconductor field effect transistors MOSFETs. The development of dynamic Random Access memory DRAM capacitor dielectrics has been similar to that of gate dielectrics.
The idea behind this is to use Al2O3 in elec- tronic industry as semiconductor-insulator-semiconductor SIS and metal-insulator- metal MIM capacitances. It is also used as an insulator in magnetic tunnel junctions MTJs used for magnetic random access memory MRAM which may allow the fabrication of solid state Q-bits based on josephson junctions JJs [ Mizuguchi u.
Park , P. To achieve high performance computing, silicon oxide was replaced by many high-k di- electrics like Al2O3[ Manchanda u. According to the property of Joseph- son junctions to perform switching at very high speed of few THz which can be used in high performance computing [ Hasuo , p.
Suzuki u. Al2O3 is used as a passivation layer on silicon, the ceramic form is often used as a carrier for thick and thin film passive components and for other small printed circuit boards PCB. It has relatively low production cost that is combined with its high thermal conductivity[ Bernardi u.
Koltsov from Leningrad Technological Institute. The concept of the ALD process was first proposed by Prof. Aleskovskii in his Ph. It was the work of Dr. Tuomo Suntola and coworkers in Finland in mids that made a scientific idea a true thin film deposition technology and later on adopted by an industrial use.
Since then it is widely used in manufacturing industries as well as research institute[ Nalwa ]. ALD is one of the thin film deposition technique that is based on sequential use of self- terminating surface reactions[ Puurunen , p. A material of desired thickness can be grown with ALD by repeating the following characteristic four pulses:.
Exposure of the first precursor, typically an metal-organic compound such as TMA. Purge or evacuation of the reaction chamber to remove the non-reacted precursor molecules and the gaseous reaction by-products. Exposure of the second co-reactant such as Ozone or another treatment, to acti- vate the surface again for the reaction of the first precursor. Purge or evacuation of the reaction chamber [ Puurunen , p. But practically it is not the case: Most ALD processes do not fulfill these criteria[ Puurunen , p.
Figure 3. In ALD, the thickness of grown material can be controlled very precisely because in the ideal case the film thickness depends only on the number of reaction cycles. Deposi- tions done with an ALD has a better step coverage and side wall deposition. ALD tech- nique is capable to grow very thin films and film properties can be reproduced.
ALD allows high density, low defect density and conformal coatings. Practically, the physical state of films like amorphous and crystallinity can be controlled by varying the process parameters like substrate temperature [ cambridge nanotech July ]. ALD gives a choice to grow heterogeneous, graded index and doped layers of differ- ent materials. Due to availability of various precursors in the market, it is possible to grow almost all materials used in semiconductor industry [ Nalwa , p.
Other ALD techniques like spatial ALD, roll-to-roll and batch processing can be incorporated to achieve high throughput of wafers per minute. Thus several wafers can be deposited with very fine thin films of different materials [ Nalwa , p. Films grown with the help of ALD can be of low stress due to molecular self-assembly.
Although we have wide range of materials available that can be grown by ALD, many important materials like Si, Ge, Si3N4, several multi-component ox- ides, certain metals cannot currently be deposited by ALD in a cost-effective way [Ritala p.
ALD is technique based on chemical reactions that occur on the surface of substrate, thus there is always a risk of residues being left from the precursors specially carbon or hydrogen. In subfig- ure 3. It was also found that TMA frag- ments only stick permanently to the surface after protons from the surface migrate to TMA and eliminate one or more ligands as CH4. The resulting formation of an Al-O bond is the first step in film growth[ Elliott u.
In figure 3. Therefore creating the self terminating re- action until the whole substrate surface was left with no -OH groups; this is the case in ideal conditions and with optimised process parameters. Moreover, excessive TMA molecules were left non-reacted on the surface or on the walls of the chamber.
Later that can be removed easily by Ar purge along with methane by products. Thus after reac- tion with the monolayer of TMA adsorbate, a layer that looks like in figure 3. This mechanism was proposed by [ Goldstein u. After the accomplish- ment of step shown in figure 3. By perform- ing these pulses over and again, a fine Al2O3 thin film of desired thickness that looks similiar to figure 3.
Every ALD cycle comprises of four steps as described in section 3. In this figure every ALD step has been shown with different colors. Starting with TMA exposure, marked as light green, TMA molecules get adsorbed on the substrate surface until there are no more adsorption sites available.
This is the reason for self-limitation in ALD. Now after this TMA exposure, it is necessary to purge excessive molecules out of the chamber. This step has been shown in figure 3. As Argon gas was used to purge the chamber because it is inert in nature. It should also be stated here, that the amount of adsorbed TMA was not dropped in the figure because ideally Ar due to its inert nature purge cannot break the chemical bond formed during first step.
The ozone exposure has been shown as light blue in the figure 3. Ozone starts to react with TMA adsorbate and form various complex intermediates on the surface[ Goldstein u.
This curve is assumed to show an exponential decay, which can be approximately defined by a fitting function described in formula 3. On completion of this step, all methyl ligands have been removed from the TMA adsorbed surface. After accomplishment of this step it is now important to remove all the reaction byproducts out of the chamber.
Thus the final step of Ar purging after ozone exposure has been followed to clear the chamber. Ar purge causes no damage to the recently formed Al2O3 on surface because Ar gas is inert in nature and Al-O bond is sufficiently strong to be damaged by Ar purge. Cycle time of a complete ALD cycle is described mathematically in equation 3. Theoretically, adsorption of TMA molecules can also be described in terms of exponential growth with KTMA as one of its parameters but due to practical reasons and fast adsorption it was complicated to do the fitting pro- cedure.
Therefore, in this project the focus was more on studying the growth kinetics for ozone. But one can obtain the same re- sults with both the precursors by tweaking other parameters like temperature, pressure etc. In [ Delabie u. It has been also shown in [ Soto , p.
It also does not show any inhibited first reaction cycles[ Park u. ALD experiments shown in [ J. Spiegelman u. Sundqvis , p. Saturation pulse times were similar between the two oxi- dants as this is directly related to gas flow dynamics in the specific ALD process cham- ber.
High electrochemical po- tential of ozone results in fast reaction rates at relatively low temperatures as compare to water which is less reactive [ Hans sundstrom , p. However, the use of ozone as a second reactant does not significantly alter the growth rate when compared to water based Al2O3 ALD films [ Kim u.
It was also found that substrate temperature plays crucial role rather than a choice of oxygen source while describing Al2O3 film properties like film thickness uniformity, step coverage and growth rate. On the contrary, for both oxygen precursors, the molar growth rate per cycle decreases with increasing temperature, and at no temperature does the O3 process yield faster growth than the H2O process [Elliott u.
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Atomic layer deposition ALD is a special kind of chemical vapor deposition, which is mainly characterized by a self-terminating surface coverage in the progress of the two distinctive reaction steps. As a result, ALD enables a highly conformal coating of complex three- dimensional-shaped surfaces including a unique film thickness control in the sub-nanometer range. Objectives: As a result of the student research project, the capability of in situ SE is to be demonstrated with respect to a detailed characterization of the Al2O3 ALD model process, comprising a comprehensive study of various process parameter interdependencies. Planning of experiments 3.
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Все были в растерянности. - Ключ… - Ее передернуло. - Коммандер Стратмор отправил кого-то в Испанию с заданием найти ключ.
Насколько. Сьюзан не понимала, к чему клонит Стратмор. - В марте я испробовала алгоритм с сегментированным ключом в миллион бит. Ошибка в функции цикличности, сотовая автоматика и прочее. ТРАНСТЕКСТ все равно справился.
Какой номер вы набираете? - Сеньор Ролдан не потерпит сегодня больше никаких трюков. - 34-62-10, - ответили на другом конце провода. Ролдан нахмурился. Голос показался ему отдаленно знакомым. Он попытался определить акцент - может быть, Бургос.
Лифт спускался на пятьдесят ярдов вниз и затем двигался вбок по укрепленному туннелю еще сто девять ярдов в подземное помещение основного комплекса агентства. Лифт, соединяющий шифровалку с основным зданием, получал питание из главного комплекса, и оно действовало, несмотря на отключение питания шифровалки. Стратмору, разумеется, это было хорошо известно, но даже когда Сьюзан порывалась уйти через главный выход, он не обмолвился об этом ни единым словом.
Это означало, что на его, Халохота, стороне фактор внезапности, хотя вряд ли он в этом так уж нуждается, у него и так все козыри на руках. Ему на руку была даже конструкция башни: лестница выходила на видовую площадку с юго-западной стороны, и Халохот мог стрелять напрямую с любой точки, не оставляя Беккеру возможности оказаться у него за спиной, В довершение всего Халохот двигался от темноты к свету. Расстрельная камера, мысленно усмехнулся. Халохот оценил расстояние до входа.
И все же Сьюзан понимала, что остановить Хейла могут только его представления о чести и честности. Она вспомнила об алгоритме Попрыгунчик. Один раз Грег Хейл уже разрушил планы АНБ.
Солнечные лучи, проходя сквозь этот экран, покрывали стены нежным кружевным узором.