Atomic layer deposition of high-k dielectrics from novel cyclopentadienyl-type precursors

The atomic layer deposition (ALD) method was applied for fabricating high permittivity (high-k) dielectrics, viz. HfO2, ZrO2 and rare earth oxides, which can be used to replace SiO2 as gate and capacitor dielectric. The dielectrics were processed by ALD using novel cyclopentadienyl (Cp, -C5H5) precursors together with water or ozone as the oxygen source. ALD, which has been identified as an important thin film growth technique for microelectronics manufacturing, relies on sequential and saturating surface reactions of alternately applied precursors, separated by inert gas purging. The surface-controlled nature of ALD enables the growth of thin films of high conformality and uniformity with an accurate thickness control. The ALD technique is introduced and ALD processes for HfO2, ZrO2 and rare earth oxide films, as well as the applications of the high-k dielectrics in microelectronics are reviewed. The need for developing new ALD processes for the high-k materials is emphasized. ALD processes for HfO2 and ZrO2 were developed using Cp-type precursors. The effect of different oxygen sources, namely water or ozone, on the film growth characteristics and properties of the ALD-processed films was examined in detail. The oxide films were stoichiometric, with impurity levels below even 0.1 at-% for C or H. Electrical measurements showed promising dielectric properties such as high permittivity values and low leakage current densities. Other properties, such as structure, interfacial layer thickness and morphology, were also characterized. Compared to films processed by water, the ozone-processed films on H-terminated Si showed improved dielectric properties, as well as higher density, lower roughness and better initial growth rate. In addition, in situ gas-phase measurements by quadrupole mass spectrometry (QMS) were performed in order to study the ZrO2 growth mechanism. A number of Cp-precursors were tested for the ALD of several rare earth oxide films. The thermal stability of many of the precursors was limited, but nevertheless, ALD-type processes were developed for Y2O3 and Er2O3 films. High reactivity of the Cp-precursors towards water resulting in high growth rates (1.2-1.7 Å/cycle) and purity of the Y2O3 and Er2O3 films were realized. Despite the detected partial decomposition of the (CpMe)3Gd precursor, Gd2O3 films with high growth rate and purity as well as effective permittivity of about 14 were deposited. Finally, promising processes for ternary scandates, namely YScO3, GdScO3, and ErScO3, were developed using either Cp- or β-diketonate-based processes. These as-deposited ternary films were amorphous exhibiting high effective permittivity (14-15), low leakage current density, and resistance towards crystallization upon annealing even up to 800°C.reviewe

Atomic layer deposition of lanthanum oxide with heteroleptic cyclopentadienyl-amidinate lanthanum precursor - Effect of the oxygen source on the film growth and properties

La2O3 thin films were deposited by atomic layer deposition from a liquid heteroleptic La precursor, La(iPrCp)2(iPr-amd), with either water, ozone, ethanol, or both water and ozone (separated by a purge) as the oxygen source. The effect of the oxygen source on the film growth rate and properties such as crystallinity and impurities was studied. Saturation of the growth rate was achieved at 225 °C with O3 as the oxygen source. With water, very long purge times were used due to the hygroscopicity of La2O3 but saturation of the growth rate was not achieved. Interestingly, when an O3 pulse was added after the water pulse with a purge in between, the growth rate decreased and the growth saturated at 200 °C. With ethanol lanthanum hydroxide was formed instead of La2O3 at 200–275 °C whereas hexagonal La2O3 films were obtained at 300 °C but the growth was not saturative. Using the separate pulses of water and ozone in the same deposition provided the best results from the four studied deposition processes. After annealing the films deposited with the La(iPrCp)2(iPrAMD)/H2O/O3 process showed pure hexagonal phase in all the films regardless of the deposition temperature, whereas mixtures of cubic and hexagonal La2O3 were seen with the other processes.Peer reviewe

Consumption of differently processed milk products in infancy and early childhood and the risk of islet autoimmunity

Several prospective studies have shown an association between cows’ milk consumption and the risk of islet autoimmunity and/or type 1 diabetes. We wanted to study whether processing of milk plays a role. A population-based birth cohort of 6081 children with HLA-DQB1-conferred risk to type 1 diabetes was followed until the age of 15 years. We included 5545 children in the analyses. Food records were completed at the ages of 3 and 6 months and 1, 2, 3, 4 and 6 years, and diabetes-associated autoantibodies were measured at 3–12-month intervals. For milk products in the food composition database, we used conventional and processing-based classifications. We analysed the data using a joint model for longitudinal and time-to-event data. By the age of 6 years, islet autoimmunity developed in 246 children. Consumption of all cows’ milk products together (energy-adjusted hazard ratio 1·06; 95 % CI 1·02, 1·11; P = 0·003), non-fermented milk products (1·06; 95 % CI 1·01, 1·10; P = 0·011) and fermented milk products (1·35; 95 % CI 1·10, 1·67; P = 0·005) was associated with an increased risk of islet autoimmunity. The early milk consumption was not associated with the risk beyond 6 years. We observed no clear differences based on milk homogenisation and heat treatment. Our results are consistent with the previous studies, which indicate that high milk consumption may cause islet autoimmunity in children at increased genetic risk. The study did not identify any specific type of milk processing that would clearly stand out as a sole risk factor apart from other milk products.Peer reviewe

Maternal dietary fatty acid intake during pregnancy and the risk of preclinical and clinical type 1 diabetes in the offspring.

The aim of the present study was to examine the associations between the maternal intake of fatty acids during pregnancy and the risk of preclinical and clinical type 1 diabetes in the offspring. The study included 4887 children with human leucocyte antigen (HLA)-conferred type 1 diabetes susceptibility born during the years 1997-2004 from the Finnish Type 1 Diabetes Prediction and Prevention Study. Maternal diet was assessed with a validated FFQ. The offspring were observed at 3- to 12-month intervals for the appearance of type 1 diabetes-associated autoantibodies and development of clinical type 1 diabetes (average follow-up period: 4·6 years (range 0·5-11·5 years)). Altogether, 240 children developed preclinical type 1 diabetes and 112 children developed clinical type 1 diabetes. Piecewise linear log-hazard survival model and Cox proportional-hazards regression were used for statistical analyses. The maternal intake of palmitic acid (hazard ratio (HR) 0·82, 95 % CI 0·67, 0·99) and high consumption of cheese during pregnancy (highest quarter v. intermediate half HR 0·52, 95 % CI 0·31, 0·87) were associated with a decreased risk of clinical type 1 diabetes. The consumption of sour milk products (HR 1·14, 95 % CI 1·02, 1·28), intake of protein from sour milk (HR 1·15, 95 % CI 1·02, 1·29) and intake of fat from fresh milk (HR 1·43, 95 % CI 1·04, 1·96) were associated with an increased risk of preclinical type 1 diabetes, and the intake of low-fat margarines (HR 0·67, 95 % CI 0·49, 0·92) was associated with a decreased risk. No conclusive associations between maternal fatty acid intake or food consumption during pregnancy and the development of type 1 diabetes in the offspring were detected

Dietary fatty acid intake in childhood and the risk of islet autoimmunity and type 1 diabetes : the DIPP birth cohort study

Publisher Copyright: © 2022, The Author(s).Purpose The aim was to study the associations between dietary intake of fatty acids in childhood and the risk of islet autoimmunity and type 1 diabetes (T1D). Methods The prospective Finnish Type 1 Diabetes Prediction and Prevention (DIPP) Study included children with genetic susceptibility to T1D born between 1996 and 2004. Participants were followed up every 3 to 12 months up to 6 years for diet, islet autoantibodies, and T1D. Dietary intake of several fatty acids at the age of 3 months to 6 years was assessed 1-8 times per participant with a 3-day food record. Joint models adjusted for energy intake, sex, HLA genotype and familial diabetes were used to investigate the associations of longitudinal intake of fatty acids and the development of islet autoimmunity and T1D. Results During the 6-year follow-up, 247 (4.4%) children of 5626 developed islet autoimmunity and 94 (1.7%) children of 5674 developed T1D. Higher intake of monounsaturated fatty acids (HR 0.63; 95% CI 0.47, 0.82), arachidonic acid (0.69; 0.50, 0.94), total n-3 fatty acids (0.64; 0.48, 0.84), and long-chain n-3 fatty acids (0.14; 0.04, 0.43), was associated with a decreased risk of islet autoimmunity with and without energy adjustment. Higher intake of total fat (0.73; 0.53, 0.98), and saturated fatty acids (0.55; 0.33, 0.90) was associated with a decreased risk of T1D only when energy adjusted. Conclusion Intake of several fatty acids was associated with a decreased risk of islet autoimmunity or T1D among high-risk children. Our findings support the idea that dietary factors, including n-3 fatty acids, may play a role in the disease process of T1D.Peer reviewe

Uusien Y- ja La-lähdeaineiden soveltuus ALE-kasvatuksiin

Kirjallisuusosassa selvitetään Y_(2)O_(3)- ja La_(2)O_(3)-ohutkalvojen valmistusta eri menetelmillä sekä esitellään lyhyesti menetelmien periaatteet. Fysikaalisista kaasufaasimenetelmistä on käsitelty elektronisuihkuhöyrystystä, pulssitettua laserkasvatusta, molekyylisuihkuepitaksiaa, sputterointia, ioniavustettua kasvatusta sekä ionisoitua klusterisuihkukasvatusta. Kemiallisista nestefaasimenetelmistä on selostettu tarkemmin vain Langmuir-Blodgett-menetelmää. Kemiallisista kaasufaasikasvatusmenetelmistä on käsitelty pyrolyysiä, kemiallista kaasufaasikasvatusta (CVD), organometallista CVD:a, plasma- ja katalyyttiavusteista CVD:a sekä atomikerrosepitaksiaa (ALE). Jokaisesta menetelmästä onkäsitelty sovelluksia Y_(2)O_(3)- ja La_(2)O_(3)-ohutkalvojen kasvatuksista erityisesti piisubstraateille. Kokeellisessa osassa valmistettiin Y_(2)O_(3)- ja La_(2)O_(3)-ohutkalvoja atomikerrosepitaksialla käyttämällä lähdeaineina organometallisia tris(syklopentadienyyli)yttriumia (Cp_(3)Y) ja -lantaania (Cp_(3)La) sekä tris(metyylisyklopentadienyyli)yttriumia (CpMe_(3)Y) ja -lantaania (CpMe_(3)La). Hapettimena käytettiin vettä. Vertailun suorittamiseksi valmistettiin myös oksidikalvoja yttrium- ja lantaani 2,2,6,6-tetrametyyli-3,5-heptaanidionilla (Y(thd)_(3) ja La(thd)_(3)) ja otsonilla. Y_(2)O_(3)-kalvojen kasvunopeuden lämpötilariippuvuutta CpMe_(3)Y:lla tutkittiin lämpötiloissa 175-450°C. ALE-ikkunassa (200-400°C) kasvunopeus Si(100)-substraatille oli 1,25- 1,35 Å/jakso. ALE-kasvu varmistettiin ja valmistusparametrit optimoitiin 300°C:n lämpötilassa. Kasvatetut kalvot olivat monikiteisiä ja stoikiometrisia. Morfologialtaan tasaisimmat kalvot kasvatettiin alle 250°C:ssa. Kasvunopeus piisubstraatille Cp_(3)Y-lähdeainetta käytettäessä oli 1,65-1,85 Å/jakso 250-400°C:n kasvatuslämpötilavälillä. Kummallakin lähdeaineella saavutettavat kalvojen kasvunopeudet olivat huomattavasti korkeammat kuin Y(thd)_(3):lla ja otsonilla kasvatettujen Y_(2)O_(3)-ohutkalvojen kasvunopeus. Lantaanioksidikalvoja pystyttiin valmistamaan CpMe_(3)La-lähdeaineella 165-175°C:n kasvatuslämpötiloissa, jolloin kasvunopeus oli 1,97 Å/jakso Kasvatetut lantaanioksidikalvot olivat monikiteisiä ja reagoivat ilman kanssa. Siitä huolimatta kalvojen havaittiin olevan morfologialtaan tasaisia. Toisaalta Cp_(3)La-lähdeaine hajoaa puolestaan jo hyvin lähellä höyrystymislämpötilaa, eikä lantaanioksidikalvojen kasvatus tällä lähdeaineella ollut mahdollista