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In recent times, the requirements have become extremely stringent for employing silicon nitride (SiNx) films in various types of applications. For instance, high etch resistance coating is required...

Trisilylamine (TSA), an exemplary chlorine and carbon-free commercial silylamine precursor, is well-known to induce improvements in the process and properties of silicon nitride (SiNx) thin films grown using atomic layer deposition (ALD). Herein, we report a TSA homolog, tris(disilanyl)amine (TDSA), as a novel chlorine and carbon-free precursor for the deposition of highly etch resistant SiNx thin films having a high growth rate at a low temperature (

In this work, effects of NH3/N2 and N2-H2/Ar plasma gases for the growth of PEALD SiNx films using pentachlorodisilane (PCDS, HSi2Cl5) were studied using a hollow cathode PEALD system. At identical process conditions, the combination of PCDS and N2−H2/Ar plasma showed a relatively lower (approximately 1.6 nm/min, 500:1 HF). Using XPS and FTIR analysis, it was identified that N2−H2/Ar gas mixture results in a Si-rich SiNx film with less N−Hx bonds when compared to NH3/N2 mixture, thereby resulting in a decreased wet etch rate.

Correlations between physical properties linking film quality with wet etch rate (WER), one of the leading figures of merit, in plasma-enhanced atomic layer deposition (PEALD) grown silicon nitride (SiNx) films remain largely unresearched. Achieving a low WER of a SiNx film is especially significant in its use as an etch stopper for technology beyond 7 nm node semiconductor processing. Herein, we explore the correlation between the hydrogen concentration, hydrogen bonding states, bulk film density, residual impurity concentration, and the WERs of PEALD SiNx using Fourier transform infrared spectrometry, X-ray reflectivity, and spectroscopic ellipsometry, etc. PEALD SiNx films for this study were deposited using hexachlorodisilane and hollow cathode plasma source under a range of process temperatures (270–360 °C) and plasma gas compositions (N2/NH3 or Ar/NH3) to understand the influence of hydrogen concentration, hydrogen bonding states, bulk film density, and residual impurity concentration on the WER. Va...

In this work, a novel chlorodisilane precursor, pentachlorodisilane (PCDS, HSi2Cl5), was investigated for the growth of silicon nitride (SiNx) via hollow cathode plasma-enhanced atomic layer deposition (PEALD). A well-defined self-limiting growth behavior was successfully demonstrated over the growth temperature range of 270–360 °C. At identical process conditions, PCDS not only demonstrated approximately >20% higher growth per cycle than that of a commercially available chlorodisilane precursor, hexachlorodisilane (Si2Cl6), but also delivered a better or at least comparable film quality determined by characterizing the refractive index, wet etch rate, and density of the films. The composition of the SiNx films grown at 360 °C using PCDS, as determined by X-ray photoelectron spectroscopy, showed low O content (∼2 at. %) and Cl content (

In this paper, atomic layer deposition of SiO2 thin films was investigated with Si2Cl6 and O3/O2 (400 g m−3). O3/O2 is not preferred for high-temperature (>400 °C) processes due to its lower decomposition temperature, especially in a furnace-type chamber. However, with Si oxidation test using a cold-wall chamber, we have demonstrated the reactivity of O3/O2 up to 800 °C in comparison with O2 and H2O. The ALD of SiO2 films was examined at deposition temperatures from 500 °C to 700 °C. The growth rate at 600 °C was saturated to 0.03 nm/cycle with Si2Cl6 exposure over 1.2 × 105 L. O3/O2 also showed ALD-like saturation behaviors for exposures over 2.4 × 106 L. The ALD films deposited at 600 °C exhibited relatively smooth surface roughness (

Results of a previous study on the hydrolysis of O -(α-acylamino-cinnamoyl)-L-β-phenyllactates E1 and E2 catalyzed by carboxypeptidase A (CPA) supported the anhydride mechanism for the action of CPA. Since these esters are hydrolyzed very slowly by CPA, it is desirable to demonstrate that the same mechanism is operative with specific substrates in order to establish the anhydride mechanism firmly. In this study, a search is made for ester substrates that are hydrolyzed very fast by CPA, involve accumulation of anhydride intermediates, and possess good chromophoric properties. O -(α-Acylamino-2-styrylacryloyl)-L-β-phenyllactates H and I , which have been prepared for this purpose, manifested kinetic features such as very small K app m and pH-independent k cat , which are consistent with the accumulation of anhydride intermediates. When judged with the magnitude of both k cat and k cat / K app m , H and I can be regarded as the link connecting nonspecific esters E1 and E2 and specific ester G1 . The k cat for esters H and I as well as nonspecific esters E1 and E2 and specific ester G1 are independent of pH, and this kinetic common feature may be taken to reflect the rate-determining breakdown of the anhydride intermediate. Results of the present study, therefore, suggest that the anhydride mechanism is also operative in the action of CPA on specific ester substrates.

Trimethylsilane-based carbon-doped silica films prepared with varying chemical-vapor-deposition process conditions were characterized using x-ray reflectivity and porosimetry to measure the film thickness, average film density, density depth profile, wall density, and porosity. Samples deposited under single or dual frequency conditions with either N2O or O2 as an oxidant were compared. The structural parameters were correlated with the chemical bond structure measured by Fourier transform infrared spectroscopy. The density profiles of the porous films were uniform with a slight densification at the film surface. The distribution of pores was also uniform through the film. Films prepared under a single frequency and/or N2O atmosphere had the lowest film density, wall density, and dielectric constant. The porosities of the films were similar and the pore sizes were less than 10 A.

Titration curves were obtained for poly(ethylenimine) (PEI), lauryl-containing PEI, and poly(allylamine) (PAA). Since each polymer contains more than 1000 amino groups, the p K a values of individual amino groups are needed for rigorous analysis of the titration curves. Instead, the titration curves are empirically analyzed by defining the deprotonation quotient Q as the ratio of the fraction of unprotonated amino groups and the fraction of protonated ones and by assuming that log Q is linearly related to pH. Very low basicity of the amines at acidic pH′s is attributed to the electrostatic suppression of the protonation of amines in cationic microenvironments. Introduction of lauryl groups to PEI lowers basicity of the amines further, which agrees with unfavorable protonation of amines in hydrophobic domains. PAA, a linear polyamine, manifests basicity comparable to or smaller than those of PEI. This is taken to suggest that the hydrophilic portions and the hydrophobic portions of PAA form separate clusters. Implications of the results to various biomimetic functional molecules built on PEI or PAA derivatives are discussed.

Papain, a thiol protease was shown to utilize 5(4H)-oxazolinones of peptides as acyl donors in peptide segment condensations. The effectiveness of this methodology is illustrated by the successful coupling of oxidized insulin B chain (30 residues) to angiotensin III (7 residues) in 59% yield.

α-Chymotrypsin (ChT) is covalently linked to various derivatives of poly(allylamine) (PAA) by using a carbodiimide as a coupling reagent. The PAA derivatives contain cationic, anionic, or hydrophobic microdomains. The ChTs linked to the PAA derivatives exhibit considerable stability against denaturing agents such as 0.5 m sodium dodecylsulfate or 4 m guanidinium chloride. This suggests multiple intramolecular cross-linking of ChT by the linear PAA derivatives. Stabilization of ChT by cross-linking with PAA derivatives is also reflected in much greater resistance of the PAA-bound ChTs to thermoinactivation. The multiple attachment of ChT to PAA derivatives does not significantly damage the active site as indicated by the reactivity of the modified ChTs at optimum pHs.

The kinetics of the Cu(II)- or Ni(II)-catalyzed deacylation of the methyl ester (3) and the N,N-dimethyl amide (4) of 2-carboxy-6-[[2-(4-carboxymethyl)imidazolyl]azo]benzoate was measured in dimethyl sulfoxide containing 5% (v/v) water. Efficient catalysis was observed as the result of the cooperation between the metal ion and the benzoyl carboxyl group. In addition, the rate for the metal-catalyzed deacylation of amide was greater or comparable to that of ester 3. The metal-ion-catalyzed deacylation of 3 and 4 involves the nucleophilic attack of the carboxylate anion as evidenced by the accumulation and the trapping of the anhydride intermediate. Moreover, the general acid catalysis by the metal-bound water in the expulsion of the amine leaving group is discovered as a novel catalytic role for the Lewis acid catalysis by metal ions in organic reactions

Kinetics of the hydrolysis of methyl 2-carboxy-6-(2-imidazoleazo)benzoate ( 1 ) and N,N -dimethyl-2-carboxy-6-(2-imidazoleazo)benzamide ( 2 ) were investigated in the presence or absence of the Cu(II) or Ni(II) ion in water or in dimethyl sulfoxide (DMSO) containing 5% (v/v) water. In 95% (v/v) DMSO, potassium chloroacetate and chloroacetic acid were used as the buffer species. Potentiometric and spectral titration of chloroacetic acid, 1 , M(II) 1 (metal-complexed 1 ), 2 , and M(II) 2 in 95% (v/v) DMSO indicated that the carboxyl groups of M(II) 1 and M(II) 2 ionize almost fully over the pH range examined and that the imidazolyl NH groups of M(II) 1 and M(II) 2 are nearly as acidic as chloroacetic acid. The kinetic data obtained for the hydrolysis of Ni(II) 1 and Cu(II) 2 in 95% (v/v) DMSO revealed that the ester and the amide bonds are readily hydrolyzed through the catalytic action of the bivalent metal ion and the anionic form, instead of the acid form, of the carboxyl group. The cooperative catalytic action of the carboxylate anion and the metal ion in the hydrolysis of alkyl ester and alkyl amide bonds, which is characteristic of carboxypeptidase A action, is achieved with 1 and 2 by using 95% (v/v) DMSO as the reaction medium. Mechanisms of the model reactions are analyzed, and implications of the present results on the mechanism of carboxypeptidase A are discussed.

In the carboxypeptidase A-catalyzed hydrolysis of O-[trans-alpha-(benzoylamino)-cinnamoyl]-L-beta-phenyllactate (BACPL) or O-[trans-alpha-(benzoylamino)-p-(phenylazo)cinnamoyl]-L-beta-phenyllacta te (BAPACPL), biphasic kinetic behavior was observed due to the accumulation of an intermediate. At -12 degrees C, conversion of the intermediate into the product was much slower than the formation of the intermediate, which accumulated in quantitative amounts. From the absorbance changes observed during the formation process of the intermediate, the concentration of active site of the enzyme was determined.

Fluorine-doped silicon oxide (SiOF) as intermetal dielectric (IMD) layer was deposited by conventional plasma-enhanced chemical vapor deposition (CVD). The main issues in the application of SiOF as IMD are as follows: (1) instability of film properties such as stress and refractive index during HTS test, (2) desorption of H2O and HF gases from SiOF film, (3) increase of line resistance, (4) wedgelike defects of metal lines, and (5) via resistance degradation during HTS test at 350°C. The above problems in use of SiOF as IMD can be eliminated by the passivation of IMD with PE-SiN and the application of Ti underlayer before the second metal deposition.