Konstantin V. Rudenko

Dependence of the Resistance of the Negative e-Beam Resist HSQ Versus the Dose in the RIE and Wet Etching Processes

This article studied the resistance of the negative electron resist based on hydrogen-silsesquioxane (HSQ) depending on the dose of exposure in the process of Reactive Ion Etching (RIE). These studies showed the strong dependence of resistance on irradiation dose (in case of full development of the e-beam resist) even after annealing the resist 30 minutes 400°C in air. Selectivity up to 14 was obtained in the process of reactive ion etching of silicon in a mixture of gases SF6: C4F8. These results can be used to manufacturing of silicon nanoscale structures. It was shown that the resistance to wet etching in a 5% solution of hydrofluoric acid (HF) is also determined by irradiation dose. Additionally, taking into account the obtained results, silicon nanowires of width 10 nm with an aspect ratio of 1: 10 was manufactured.

Boron Profile Sharpening in Ultra‐Shallow p+‐n Junction Produced by Plasma Immersion Ion Implantation from BF3 Plasma

We have investigated plasma immersion ion implantation (PI3) of boron with energies of 500 eV (doses up to 2×1015u2009cm−2) from BF3 plasma with He pre‐amorphizing implantation (PAI) (energy 3 keV, dose 5×1016u2009cm−2). Implanted samples were subjected to RTA (Tu2009=u2009900 to 1050u2009°C, tu2009=u20092 to 24 sec and spike anneal). SIMS analysis of boron profiles revealed its anomalous behavior. For short RTA times the profile tail (below 5×1019u2009cm−3) moves toward the surface and then, as in the usual diffusion, toward the bulk at longer annealing times.

Technology for fabrication of sub-20 nm silicon planar nanowires array

The results presented on Silicon one-dimensional structures fabrication which are promising for application in nanoelectronics, sensors, THz-applications. We employ two-stage technology of precise anizotropic plasma etching of silicon over e-beam resist and isotropic removal of thermally oxidised defected surface layer of silicon by wet etch. As first the process for nano-fins fabrication on SOI substrate was developed. HSQ resist was used as a negative-tone electron beam resist with good etch-resistance, high resolution and high mechanical stability. The etching was performed by RIE in mix of SF6 + C4F8. plasma. By changing the ratio SF6:C4F8, the sidewall profile angle can be controlled thoroughly. Next step to minimize lateral size of structures and reduce impact of surface defects on electron mobility in core of nanowires was the application of surface thermal oxidation to defected layer. It was used for selective removal of damaged silicon layer and polymer residues. Oxidation was performed with controlled flow of dry oxygen and water vapour. Oxidation rate was precisely controlled by ex-situ spectral ellipsometry on unpatterned chips As a result the arrays of planar sub-20 nm Silicon nanowires with length in the range 200 nm – 500 um were made.

Monte Carlo simulation of boron doping profile of fin and trench structures by plasma immersion ion implantation

Plasma immersion ion implantation into fins and trenches at elevated pressures is simulated. In the present work we calculate boron concentration distribution in the sample accounting for ion scattering in plasma sheath and geometric shadowing effects (ions at certain angle of incidence couldn’t achieve shadowed part of trench wall and bottom). First, energy and angle distribution of ions passed through the plasma sheath to the sample surface is obtained. These data are used to calculate boron concentration distribution in the sample. Pressure range is 30-300 mTorr, plasma electron temperature 5 eV, plasma density 1010-1012 cm-3. The degree of conformity increases with the pressure raises and decreases with the density of plasma.

Application of Langmuir probe technique in depositing plasmas for monitoring of etch process robustness and for end-point detection

The objective of the paper is to examine recently proposed Dynamic Langmuir probe (DLP) method as a simple and cost-effective tool for in situ monitoring of end-point detection in plasma etch process and to discuss the Langmuir probe application to indicate chamber walls conditions. Experiment was carried out in mixture CF4 and O2 during anisotropic plasma etching of blank structures Si3N4/SiO2/Si. To account for possible practical obstacles of end point detection in commercial process experimental conditions were intentionally chosen to be quite severe. Reduced etching area was about 35% of total area; wafer temperature was not controlled; process was not optimized for selectivity; detected interfaces include Si3N4/SiO2. DLP-data was compared with optical emission spectroscopy (OES) measurements. An approach to process drift prevention was shown by performing measurements in reference Ar plasma between etch processes causing wall contamination. Particularly correlation between plasma potential and cumulative time of processing in strongly depositing C4F8 plasma was studied.

Ultrasensitive Detection of 2,4-Dinitrophenol Using Nanowire Biosensor

The method for the detection of 2,4-dinitrophenol (DNP) in solution is proposed. This method employs the sensors based on silicon nanowire field-effect transistors with protective layers of high-k dielectrics, whose surface is functionalized with an amino silane. Direct highly sensitive detection of DNP has been demonstrated, and the lowest detectable concentration of DNP was determined to be 10−14u2009M. Silicon-on-insulator nanowire (SOI-NW) sensors can well be employed for the rapid detection of a wide range of toxic and explosive compounds by selection of sensor surface modification techniques.

Micro-Raman Spectroscopy for Monitoring of Deposition Quality of High-k Stack Protective Layer onto Nanowire FET Chips for Highly Sensitive miRNA Detection

Application of micro-Raman spectroscopy for the monitoring of quality of high-k (h-k) dielectric protective layer deposition onto the surface of a nanowire (NW) chip has been demonstrated. A NW chip based on silicon-on-insulator (SOI) structures, protected with a layer of high-k dielectric ((h-k)-SOI-NW chip), has been employed for highly sensitive detection of microRNA (miRNA) associated with oncological diseases. The protective dielectric included a 2-nm-thick Al2O3 surface layer and a 8-nm-thick HfO2 layer, deposited onto a silicon SOI-NW chip. Such a chip had increased time stability upon operation in solution, as compared with an unprotected SOI-NW chip with native oxide. The (h-k)-SOI-NW biosensor has been employed for the detection of DNA oligonucleotide (oDNA), which is a synthetic analogue of miRNA-21 associated with oncological diseases. To provide biospecificity of the detection, the surface of (h-k)-SOI-NW chip was modified with oligonucleotide probe molecules (oDVA probes) complementary to the sequence of the target biomolecule. Concentration sensitivity of the (h-k)-SOI-NW biosensor at the level of DL~10−16 M has been demonstrated.

Elements for hard X-ray optics produced by cryogenic plasma etching of silicon

A number of different hard X-ray optics elements such as refractive lenses, refractive bi-lenses and multilens interferometers, mirror interferometers can be made of Silicon. The optical performance of these elements depends on the quality of refracting and reflecting surfaces. Cryogenic deep anisotropic etching was proposed for fabrication of parabolic planar lenses and mirror interferometers. The investigation of sidewall roughness was done by AFM and by optical interferometry. Geometrical parameters of structures were measured by SEM. It was observed that roughness of inner sidewalls of etched structures does not exceed 3 nm/um (RMS) and deviation from vertical profile was within 30 nm along 20 um depth.

Carbon and fluorine co-implantation for boron diffusion suppression in extremely ultra shallow junctions

Formation of ultra shallow p+-junctions in silicon by plasma immersion ion implantation were investigated. The effect of carbon and fluorine coimplantation were studied experimentally. Dependence of this effect from carbon concentration was studied, as well as positive role of multistep annealing for pure boron implanted samples.

Langmuir probe applications in monitoring of plasma etching

The purpose of the paper is to investigate the measurable variations in chemistry of SF6/O2/Ar plasma due to etching through layers interface of structure poly-Si/SiO2/Si. The noticeable magnitude and sufficient stability in some single parameters deference make it possible to develop application of Langmuir probe as implementation of a simple end-point-detection technique. The proposed method is based on the established idea that the surface reactions involved to the process of etching lead to dramatic changes in some parameters of the charged plasma species during the process. Particularly it was found that the densities of electrons and ions and the electron temperature are affected. It was shown that effective electron temperature and electron energy distribution function of the reactive gaseous mixture differ greatly from those of Ar plasma under the same excitation conditions. An approach to wafer-surface charging minimization by varying excitation settings and EEDF was proposed.