Our aim was to establish a methodology for laser assisted oxidation of semiconductor and metal surfaces. One advantage of laser oxidation is the fact that radiation is heavily absorbed in a thin surface layer of the sample and the other is its ability for local oxidation. In addition to this, laser beam can be directed into some areas that other processes cannot reach. For these reasons, Nd:YAG pulsed laser working at 1064 nm wavelength is used for the oxidation purposes of Si and Ta films. First, SiO2 layer was obtained for various O2 pressures and laser powers. The thickness, refractive index, structural, dielectric, electrical and optical characteristics of the SiO2 layers have been determined. We have established that there exists an interval of laser power in which the oxidation occurs without surface melting. The oxidation process is controlled by the laser power rather than by the substrate temperature (673 &ndash / 748 K). It was found that better film quality is obtained at higher substrate temperatures and laser power greater than 3.36 J/cm2. Second, rf-sputtered Ta films were oxidized by laser, because Ta2O5 appears to be a good promising candidate to replace SiO2 because of its high dielectric constant, high breakdown voltage and relevant small leakage current values. It was found that the substrate temperature is an important parameter to obtain denser layers with reduced amount of suboxides and the most suitable substrate temperature range is around 350 C to 400 C. &amp / #946 / -orthorhombic crystal structure was obtained when the substrate temperature is 350 &ndash / 400 C for thinner films (up to 20 &ndash / 25 nm) and 300 &ndash / 350 C for thicker films (40 nm). The refractive index values of laser grown thin tantalum oxide films were between ~1.9 and 2.2 being close to those of bulk Ta2O5 (2.0 &ndash / 2.2). Oxide thicknesses in uniform Gaussian&ndash / like shapes were measured as around the twice of those initial Ta films. Effective dielectric constant values reached ~26 when the substrate temperature was increased from 250 C to around 400 C. It was shown that the leakage current density level decreases with increasing substrate temperature. However, the refractive index values of the films were smaller than those of thermally grown films. Porous structure formed during laser oxidation might be the reason for lower refractive indices and can be improved by post&ndash / oxidation annealing.

O carbeto de silício (SiC) é um semicondutor com propriedades adequadas para substituir o silício em dispositivos eletrônicos em aplicações que exijam alta potência, alta frequência e/ou alta temperatura. Além disso, é possível crescer termicamente um filme de dióxido de silício (SiO2) sobre o SiC de maneira análoga ao silício. Porém, esses filmes apresentam maior densidade de defeitos eletricamente ativos na região interfacial SiO2/SiC que no caso do SiO2/Si, o que limita a qualidade dos dispositivos formados. Assim, compreender a origem da degradação elétrica e desenvolver métodos para passivar os defeitos na região interfacial SiO2/SiC são importantes passos para o desenvolvimento da tecnologia do SiC. Buscando uma melhor compreensão da natureza dos defeitos presentes na região interfacial SiO2/SiC, a interação de estruturas SiO2/SiC com vapor d’água enriquecido isotopicamente (D2 18O) e a interação com monóxido de carbono (CO), um dos subprodutos da oxidação térmica do SiC, foram investigadas. Observou-se que a interação com CO gera cargas positivas na estrutura e que a incorporação de deutério proveniente da água é fortemente dependente da rota de formação do filme de SiO2. Sabendo que a incorporação de nitrogênio e de fósforo na região interfacial SiO2/SiC são eficientes métodos para reduzir o número de defeitos eletricamente ativos nessa região, investigou-se a incorporação de nitrogênio em estruturas de SiC através de tratamentos térmicos em amônia enriquecida isotopicamente (15NH3) e desenvolveu-se um novo método de incorporação de fósforo, fazendo sua deposição por pulverização catódica (sputtering) Os métodos de incorporação propostos resultaram em maiores quantidades de nitrogênio e de fósforo na região interfacial SiO2/SiC do que os encontrados na literatura, tornando-os promissores candidatos na passivação elétrica do SiC. Além da caracterização físico-química utilizando diferentes técnicas, também foi feita a caracterização elétrica de capacitores Metal-Óxido-Semicondutor (MOS) testando filmes de SiO2 obtidos por sputtering ou por crescimento térmico. Adicionalmente, desenvolveu-se uma rota de síntese de padrões de 18O mais estáveis ao longo do tempo para serem utilizados em análises por reação nuclear. Também foi proposta uma metodologia de quantificação de fósforo via análise por reação nuclear. Dos resultados obtidos neste doutorado, uma melhor compreensão da natureza e da origem dos defeitos presentes na região interfacial SiO2/SiC foi alcançada. Também obteve-se uma melhor compreensão de como os elementos passivadores nitrogênio e fósforo interagem nessa região. / Silicon carbide (SiC) is a semiconductor with adequate properties to substitute silicon in electronic devices in applications that require high power, high frequency, and/or high temperature. Besides, a silicon dioxide (SiO2) film can be thermally grown on SiC in a similar way to that on Si. However, these films present higher density of electrical defects in the SiO2/SiC interfacial region when compared to the SiO2/Si interface, which limits the quality of the fabricated devices. Thus, it is important to understand the origin of the electrical degradation and to develop methods to passivate the defects in the SiO2/SiC interfacial region in order to develop the SiC technology. Aiming at a better understanding of the nature of defects at the SiO2/SiC interfacial region, the interaction of SiO2/SiC structures with water vapor isotopically enriched (D2 18O) and the interaction with carbon monoxide (CO), one of the SiC thermal oxidation by-products, were investigated. It was observed that the interaction with CO generates positive charges in the structure and that the deuterium incorporation from the water vapor is strongly dependent on the formation route of the SiO2 film. Knowing that nitrogen and phosphorous incorporation in the SiO2/SiC interfacial region are efficient methods to reduce the number of electrical defects in this region, the nitrogen incorporation in SiC structures by isotopically enriched ammonia (15NH3) annealings was investigated and a new method to incorporate phosphorous, by sputtering deposition was developed The proposed incorporation methods resulted in higher amounts of nitrogen and phosphorous then those found in literature, making them promising candidates to the electrical passivation of SiC. Besides the physico-chemical characterization using different techniques, the electrical characterization of Metal-Oxide-Semiconductor (MOS) capacitors was also performed, testing SiO2 films obtained by sputtering deposition or thermally grown. Additionally, a route to synthesize 18O standards for nuclear reaction analyses that are more stable over time was developed. Besides, a methodology to quantify phosphorous by nuclear reaction analysis was proposed. From the results obtained in this PhD thesis, a better understanding of the nature and the origin of defects present in the SiO2/SiC interfacial region was obtained, as well as a better understanding on how the passivating elements nitrogen and phosphorous interact in this region.

O carbeto de silício (SiC) é um semicondutor com propriedades adequadas para substituir o silício em dispositivos eletrônicos em aplicações que exijam alta potência, alta frequência e/ou alta temperatura. Além disso, é possível crescer termicamente um filme de dióxido de silício (SiO2) sobre o SiC de maneira análoga ao silício. Porém, esses filmes apresentam maior densidade de defeitos eletricamente ativos na região interfacial SiO2/SiC que no caso do SiO2/Si, o que limita a qualidade dos dispositivos formados. Assim, compreender a origem da degradação elétrica e desenvolver métodos para passivar os defeitos na região interfacial SiO2/SiC são importantes passos para o desenvolvimento da tecnologia do SiC. Buscando uma melhor compreensão da natureza dos defeitos presentes na região interfacial SiO2/SiC, a interação de estruturas SiO2/SiC com vapor d’água enriquecido isotopicamente (D2 18O) e a interação com monóxido de carbono (CO), um dos subprodutos da oxidação térmica do SiC, foram investigadas. Observou-se que a interação com CO gera cargas positivas na estrutura e que a incorporação de deutério proveniente da água é fortemente dependente da rota de formação do filme de SiO2. Sabendo que a incorporação de nitrogênio e de fósforo na região interfacial SiO2/SiC são eficientes métodos para reduzir o número de defeitos eletricamente ativos nessa região, investigou-se a incorporação de nitrogênio em estruturas de SiC através de tratamentos térmicos em amônia enriquecida isotopicamente (15NH3) e desenvolveu-se um novo método de incorporação de fósforo, fazendo sua deposição por pulverização catódica (sputtering) Os métodos de incorporação propostos resultaram em maiores quantidades de nitrogênio e de fósforo na região interfacial SiO2/SiC do que os encontrados na literatura, tornando-os promissores candidatos na passivação elétrica do SiC. Além da caracterização físico-química utilizando diferentes técnicas, também foi feita a caracterização elétrica de capacitores Metal-Óxido-Semicondutor (MOS) testando filmes de SiO2 obtidos por sputtering ou por crescimento térmico. Adicionalmente, desenvolveu-se uma rota de síntese de padrões de 18O mais estáveis ao longo do tempo para serem utilizados em análises por reação nuclear. Também foi proposta uma metodologia de quantificação de fósforo via análise por reação nuclear. Dos resultados obtidos neste doutorado, uma melhor compreensão da natureza e da origem dos defeitos presentes na região interfacial SiO2/SiC foi alcançada. Também obteve-se uma melhor compreensão de como os elementos passivadores nitrogênio e fósforo interagem nessa região. / Silicon carbide (SiC) is a semiconductor with adequate properties to substitute silicon in electronic devices in applications that require high power, high frequency, and/or high temperature. Besides, a silicon dioxide (SiO2) film can be thermally grown on SiC in a similar way to that on Si. However, these films present higher density of electrical defects in the SiO2/SiC interfacial region when compared to the SiO2/Si interface, which limits the quality of the fabricated devices. Thus, it is important to understand the origin of the electrical degradation and to develop methods to passivate the defects in the SiO2/SiC interfacial region in order to develop the SiC technology. Aiming at a better understanding of the nature of defects at the SiO2/SiC interfacial region, the interaction of SiO2/SiC structures with water vapor isotopically enriched (D2 18O) and the interaction with carbon monoxide (CO), one of the SiC thermal oxidation by-products, were investigated. It was observed that the interaction with CO generates positive charges in the structure and that the deuterium incorporation from the water vapor is strongly dependent on the formation route of the SiO2 film. Knowing that nitrogen and phosphorous incorporation in the SiO2/SiC interfacial region are efficient methods to reduce the number of electrical defects in this region, the nitrogen incorporation in SiC structures by isotopically enriched ammonia (15NH3) annealings was investigated and a new method to incorporate phosphorous, by sputtering deposition was developed The proposed incorporation methods resulted in higher amounts of nitrogen and phosphorous then those found in literature, making them promising candidates to the electrical passivation of SiC. Besides the physico-chemical characterization using different techniques, the electrical characterization of Metal-Oxide-Semiconductor (MOS) capacitors was also performed, testing SiO2 films obtained by sputtering deposition or thermally grown. Additionally, a route to synthesize 18O standards for nuclear reaction analyses that are more stable over time was developed. Besides, a methodology to quantify phosphorous by nuclear reaction analysis was proposed. From the results obtained in this PhD thesis, a better understanding of the nature and the origin of defects present in the SiO2/SiC interfacial region was obtained, as well as a better understanding on how the passivating elements nitrogen and phosphorous interact in this region.

O carbeto de silício (SiC) é um semicondutor com propriedades adequadas para substituir o silício em dispositivos eletrônicos em aplicações que exijam alta potência, alta frequência e/ou alta temperatura. Além disso, é possível crescer termicamente um filme de dióxido de silício (SiO2) sobre o SiC de maneira análoga ao silício. Porém, esses filmes apresentam maior densidade de defeitos eletricamente ativos na região interfacial SiO2/SiC que no caso do SiO2/Si, o que limita a qualidade dos dispositivos formados. Assim, compreender a origem da degradação elétrica e desenvolver métodos para passivar os defeitos na região interfacial SiO2/SiC são importantes passos para o desenvolvimento da tecnologia do SiC. Buscando uma melhor compreensão da natureza dos defeitos presentes na região interfacial SiO2/SiC, a interação de estruturas SiO2/SiC com vapor d’água enriquecido isotopicamente (D2 18O) e a interação com monóxido de carbono (CO), um dos subprodutos da oxidação térmica do SiC, foram investigadas. Observou-se que a interação com CO gera cargas positivas na estrutura e que a incorporação de deutério proveniente da água é fortemente dependente da rota de formação do filme de SiO2. Sabendo que a incorporação de nitrogênio e de fósforo na região interfacial SiO2/SiC são eficientes métodos para reduzir o número de defeitos eletricamente ativos nessa região, investigou-se a incorporação de nitrogênio em estruturas de SiC através de tratamentos térmicos em amônia enriquecida isotopicamente (15NH3) e desenvolveu-se um novo método de incorporação de fósforo, fazendo sua deposição por pulverização catódica (sputtering) Os métodos de incorporação propostos resultaram em maiores quantidades de nitrogênio e de fósforo na região interfacial SiO2/SiC do que os encontrados na literatura, tornando-os promissores candidatos na passivação elétrica do SiC. Além da caracterização físico-química utilizando diferentes técnicas, também foi feita a caracterização elétrica de capacitores Metal-Óxido-Semicondutor (MOS) testando filmes de SiO2 obtidos por sputtering ou por crescimento térmico. Adicionalmente, desenvolveu-se uma rota de síntese de padrões de 18O mais estáveis ao longo do tempo para serem utilizados em análises por reação nuclear. Também foi proposta uma metodologia de quantificação de fósforo via análise por reação nuclear. Dos resultados obtidos neste doutorado, uma melhor compreensão da natureza e da origem dos defeitos presentes na região interfacial SiO2/SiC foi alcançada. Também obteve-se uma melhor compreensão de como os elementos passivadores nitrogênio e fósforo interagem nessa região. / Silicon carbide (SiC) is a semiconductor with adequate properties to substitute silicon in electronic devices in applications that require high power, high frequency, and/or high temperature. Besides, a silicon dioxide (SiO2) film can be thermally grown on SiC in a similar way to that on Si. However, these films present higher density of electrical defects in the SiO2/SiC interfacial region when compared to the SiO2/Si interface, which limits the quality of the fabricated devices. Thus, it is important to understand the origin of the electrical degradation and to develop methods to passivate the defects in the SiO2/SiC interfacial region in order to develop the SiC technology. Aiming at a better understanding of the nature of defects at the SiO2/SiC interfacial region, the interaction of SiO2/SiC structures with water vapor isotopically enriched (D2 18O) and the interaction with carbon monoxide (CO), one of the SiC thermal oxidation by-products, were investigated. It was observed that the interaction with CO generates positive charges in the structure and that the deuterium incorporation from the water vapor is strongly dependent on the formation route of the SiO2 film. Knowing that nitrogen and phosphorous incorporation in the SiO2/SiC interfacial region are efficient methods to reduce the number of electrical defects in this region, the nitrogen incorporation in SiC structures by isotopically enriched ammonia (15NH3) annealings was investigated and a new method to incorporate phosphorous, by sputtering deposition was developed The proposed incorporation methods resulted in higher amounts of nitrogen and phosphorous then those found in literature, making them promising candidates to the electrical passivation of SiC. Besides the physico-chemical characterization using different techniques, the electrical characterization of Metal-Oxide-Semiconductor (MOS) capacitors was also performed, testing SiO2 films obtained by sputtering deposition or thermally grown. Additionally, a route to synthesize 18O standards for nuclear reaction analyses that are more stable over time was developed. Besides, a methodology to quantify phosphorous by nuclear reaction analysis was proposed. From the results obtained in this PhD thesis, a better understanding of the nature and the origin of defects present in the SiO2/SiC interfacial region was obtained, as well as a better understanding on how the passivating elements nitrogen and phosphorous interact in this region.

The continuous downscaling has enforced the device size and oxide thickness to few nanometers. After serving for several decades as an excellent gate oxide layer in complementary metal oxide semiconductor (CMOS) devices, the thickness of SiO2 layer has reached to its theoretical limits. Ultra-thin films of SiO2 can result in severe leakage currents due to direct tunneling as well as maintaining the homogeneity of the layers becomes an additional challenge. The use of a high- (HK) layer can solve these twin concerns of the semiconductor industry, which can also enhance the capacitance due to superior dielectric permittivity and reduce the leakage current by being thicker than the silicon dioxide. This thesis is concerned about the development of solution route fabricated high-k (TiO2, ZrO2 and HfO2) gate dielectrics and the investigation of high-/silicon interfaces by highly sensitive DLTS technique in MOS structures. The solution processing reduce the industrial fabrication cost and the DLTS method has the advantage to accurately measure the interface related defects parameters; such as interface trap density (Dit), capture cross-section (), activation energy (ET) and also distinguish between bulk and interface traps. In this thesis, HK films have been deposited by solution route, the material and electrical properties of the film and the HK/Si interface have been extensively evaluated. IN CHAPTER 1, we have summarized the history and evolution of transistor and it provides the background for the work presented in this thesis. IN CHAPTER 2, we have described the experimental method /technique used for the fabrication and characterization. The advantages and working principals of spin-coating and DLTS techniques are summarized. IN CHAPTER 3, we have presented the preparation and optimization of TiO2 based HK layer. Structural, surface morphology, optical electrical and dielectric properties are discussed in details. A high- 34 value is achieved for the 36 nm TiO2 films. IN CHAPTER 4, we presented the technologically relevant Si/TiO2 interface study by DLTS technique. The DLTS analysis reveals a small capture cross-section of the interface with acceptable interface state density. IN CHAPTER 5, we have focused on the fabrication of amorphous ZrO2 films on p-Si substrate. The advantage of amorphous dielectric layer is summarized as first dielectric reported SiO2 is used in its amorphous phase. The moderate-15 with low leakage current density is achieved. IN CHAPTER 6, the HfO2 films are prepared using hafnium isopropoxide and a high value of dielectric constant 23 is optimized with low leakage current density. The current conduction mechanisms are discussed in details. IN CHAPTER 7, we have probed the oxygen vacancy related sub-band-gap states in HfO2 by DLTS technique. IN CHAPTER 8, we have presented the summary of the dissertation and the prospect research directions are suggested. In summary, we have studied the group IVB transition metal elemental oxides (TMEO); TiO2, ZrO2 and HfO2 thin films in the MOS structure, as a possible replacement of SiO2 gate dielectric. For the TMEO films deposition a low-cost and simple method spin-coating was utilized. The film thicknesses are in the range of 35 – 39 nm, which was measured by ellipsometry and confirmed with the cross-sectional SEM. A rough surface of gate dielectric layer can trap the charge carrier and may cause the Fermi level pinning, which can cause the threshold voltage instabilities. Hence, surface roughness of oxide layer play an important role in CMOS device operation. We have achieved quite good flat surfaces (RMS surface roughness’s are 0.2 – 2.43 nm) for the films deposited in this work. The TiO2 based MOS gate stack shows an optimized high dielectric constant ( 34) with low leakage current density (3.710-7 A.cm-2 at 1 V). A moderate dielectric constant ( 15) with low leakage current density (4.710-9 A.cm-2 at 1 V) has been observed for the amorphous ZrO2 thin films. While, HfO2 based MOS gate stack shows reasonably high dielectric constant ( 23) with low leakage current density (1.410-8 A.cm-2 at 1 V). We have investigated the dominating current conduction mechanism and found that the current is mainly governed by space charge limited conduction (SCLC) mechanism for the high bias voltages, while low and intermediate bias voltages show the (Poole – Frenkel) PF and (Fowler – Nordheim) FN tunneling, respectively. For the HfO2 MOS device band alignment is drawn from the UPS and J-V measurements. The band gap and electron affinity of HfO2 films are estimated 5.9 eV and 3 eV, respectively, which gives a reasonable conduction band offset (1.05 eV) with respect to Si. A TMEO film suffers from a large number of intrinsic defects, which are mostly oxygen vacancies. These defects can create deep levels below the conduction band of high- dielectric material, which can act like a hole and electron traps. In addition to that, interface between Si and high- is an additional concern. These defect states in the band gap of high- or at the Si/ high- interface might lead to the threshold voltage shifts, lower carrier mobility in transistor channel, Fermi level pinning and various other reliability issues. Hence, we also studied bulk and interfacial defects present in the high- films on Si and their interface with Si by a very sensitive DLTS technique. The capture cross-sections are measured by insufficient filling DLTS (IF – DLTS). The defects present at the interface are Si dandling bond and defect in the bulk are mostly oxygen vacancies related defects present in various charge states. The interface states (Dit) are in the range of 2×1011 to 9×1011 eV-1cm-2, which are higher than the Al/SiO2/Si MOS devices (Dit in Al/SiO2/Si is the benchmark and in the order of 1010 eV-1cm-2). Still this is an acceptable value for Si/high-k (non-native oxide) MOS devices and consistent with other deposition methods. The capture cross-sections are found to be quite low in the order of 10-18 to 10-19 cm2, which indicate a minor impact on the device operation. The small value of capture cross-sections are attributed to the involvement of tunneling, to and from the bulk traps to the interface. In conclusion, the low cost solution processed high- thin films obtained are of high quality and find their importance as a potential dielectric layer. DLTS study will be helpful to reveal various interesting facts observed in high- such as resistive switching, magnetism and leakage current problems mediated by oxygen vacancy related defects