摘要:

The thermal stability of thin cobalt silicide layers grown on preamorphized chemical vapor deposited silicon layers has been studied in the temperature range between 950 and 1100 °C. The morphology of the starting layers and their evolution during the thermal processes was analyzed by transmission electron microscopy, atomic force microscopy and Rutherford backscattering spectroscopy. The observed increase in sheet resistance with the annealing time has been correlated to the agglomeration process taking into account the dependence of the resistivity on film thickness and carrier mean free path. Sheet resistance measurements have been used to study the agglomeration process ofCoSi2by varying temperature and substrate doping (As,BF2,and Si implants). The process is thermally activated with an activation energy of 4.3 eV for the Si implanted samples. TheBF2implanted substrate show a higher activation energy(∼5.4 eV),while the arsenic implanted a lower one(∼3.6 eV).This difference is attributed to the weakening of the Co–Si bonds by arsenic atoms and to the presence of some fluorine precipitates at theCoSi2/Siinterface that increase the energy needed for the reaction at the silicide/silicon interface.

ISSN:1071-1023    

DOI:10.1116/1.590021

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

The Pt/Ta diffusion barrier using hybrid conductive oxide(RuO2)for dynamic random access memory and ferroelectric random access memory capacitor bottom electrodes is proposed. The thermal stability ofPt+RuO2(50 nm)/Ta+RuO2(50 nm)/TiSi2/poly-Si/SiO2/Sicontact system is investigated and compared to that of thePt(50 nm)/Ta(50 nm)/TiSi2/poly-Si/SiO2/Sicontact system. ThePt+RuO2/Ta+RuO2/TiSi2/poly-Si/SiO2/Sicontact system sustained its structure up to 650 °C, whereasPt/Ta/TiSi2/poly-Si/SiO2/Sicontact system was completely degraded after annealing at 650 °C. In the former case, the addition of ruthenium dioxide(RuO2)into the Pt bottom electrode layer led to retardation of the oxygen indiffusion, preventing the indiffusion of oxygen up to 650 °C. In addition, theTa+RuO2diffusion barrier showed an amorphous structure andRuO2is bound to the Ta matrix, inhibiting the interdiffusion of O, Pt, and Si through grain boundaries which can act as fast diffusion paths up to high temperatures. Therefore, it appeared that the barrier properties of Pt/Ta diffusion barrier are improved by using hybrid conductive oxide(RuO2).

ISSN:1071-1023    

DOI:10.1116/1.590022

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

Quantum dots ofSi1−x−yGexCyalloys with high Ge contents were grown on Si(311) and Si(001) substrates by solid source molecular beam epitaxy and were measured by atomic force microscopy. The quantum dot layers had a nominal thickness (equivalent two-dimensional) of 4 nm. The smallest quantum dots occurred for the compositionSi0.09Ge0.9C0.01on Si (311), and had a 40 nm mean diameter, an 8 nm mean height, and a density of3.3×1010 cm−2. Quantum dots on Si(001) were larger and had less regular spacing than quantum dots on Si(311) with the same composition. Carbon decreased both the mean size and spacing of SiGe quantum dots and the ratio of size deviation to mean diameter. The presence of small uniform quantum dots for particular compositions is attributed to a reduction in the surface migration of adatoms due to decreased atomic surface diffusivity. These results suggest that quantum dot organization is controlled by composition, substrate orientation, strain, and surface diffusion.

ISSN:1071-1023    

DOI:10.1116/1.590023

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

Nanostructures in Al were generated by printing with hard SiC molds. This nano-printing technology replaces the lithography and the etching or deposition processes to produce patterns directly in metal. Dots, short lines, and long lines were formed in the SiC molds by electron beam lithography and reactive ion etching. High aspect ratio features as small as 40 nm with depth up to 840 nm were patterned in the SiC molds. By pressing the SiC mold onto the Al substrate at room temperature, nanostructures in the SiC mold were reproduced accurately and uniformly in Al. Large arrays of nanostructures down to 40 nm were printed in Al with similar results for dots, short lines, and long lines. Using atomic force microscopy to analyze the cross sections of the SiC molds and printed Al nanostructures, depth dependence on feature size was observed. This nano-printing technology simplifies the processes for generating nanostructures with high throughput and high uniformity.

ISSN:1071-1023    

DOI:10.1116/1.590024

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

We report on the modification of a conventional scanning transmission electron microscope (CM12, Philips) for electron-beam lithography. The hardware as well as the entirely home designed lithography software are described in detail. Special attention is paid to the reduction of the proximity effect by means of our lithography software using a fairly simple exposure model. Various lithography results are shown including nonmagnetic as well as ferromagnetic nanostructures with linewidths as small as 20 nm. Problems occurring when fabricating magnetic nanostructures and their solutions are presented and discussed.

ISSN:1071-1023    

DOI:10.1116/1.590025

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

A thin carbonaceous resist was grown by exposing a substrate to a beam of neutral metastable argon atoms in the presence of siloxane vapor. X-ray photoelectron spectroscopy and Auger electron spectroscopy data show that the resist was composed primarily of carbon. Near edge x-ray absorption fine structure spectra of samples exposed to metastable atoms show that carbon double bonds were formed during exposure. The deposited material was used as a resist for reactive ion etching intoSiO2andSi3N4.Lines inSiO2were fabricated with widths as small as 20 nm, aspect ratios>2:1,and sidewalls as steep as 7:1.

ISSN:1071-1023    

DOI:10.1116/1.590026

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

Focused-ion-beam (FIB) lithographic characteristics of low-pressure chemical-vapor-depositedSi3N4resist have been studied using low-energyGa+-FIB exposure andCF4reactive ion-etching (RIE) development. The resist thickness,Zmin,to minimize a substrate damage is determined by Monte Carlo (MC) simulation. TheZminis approximately 190, 355, and 560 Å for incident ion energies of 10, 30, and 40 keV, respectively. Ga+FIB-exposed Si3N4for CF4RIE development demonstrates a negative-type resist which is dependent on resist thickness and dose. In the case of 30 keVZminSi3N4,a pattern is formed initially at dose of about 5.70×1015ions/cm2(D1), and a linewidth corresponding to a beam diameter of 0.36 μm is obtained at dose of 4.73×1016ions/ cm2(D2). Above a critical dose of about 7.56×1016ions/cm2(D3), which reaches a surface concentration of about 1.5×1021ions/cm3according to MC simulation, a dent begins to form from the center of pattern. The reason for the formation of dent is not clear at present but may be due to the decrease of resistance against CF4-reactive gas with the increase of the surface ion concentration up to a critical value. The values(D1,D2,D3)decrease with decreasing resist thickness. As the incident energy increases, the threshold dose increases. The imaging contrast appear to be about 3.3–3.5. A 190-Å-thick Si3N4resist exposed by 10 keV FIB with a dose of 8.0×1015ions/cm2increases both the refractive indexn, and the optical energy gap,Eopto aboutΔn=0.007 andΔEop=0.07 eV. A clear pattern with a linewidth of 0.14 μm is formed onZminSi3N4resist by 40 keV FIB exposure.

ISSN:1071-1023    

DOI:10.1116/1.590086

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

In order to improve the properties, such as stress and crystallinity, of diamond films for use as x-ray masks, we have studied the effectiveness of the addition ofO2to aCH4/H2gaseous mixture in magnetically enhanced microwave plasma chemical vapor deposition. As theO2concentration was increased, diamond grain growth became more dominant over the nondiamond component and grain growth continued. As a result, stress shifted toward the tensile regime. We explain the mechanism of this diamond stress shift by using the stress generation model proposed by Chaudhari. Under the optimum deposition conditions, i.e.,CH4/O2/H2=2.0/0.5/97.5 vol %at 920 °C, we obtained (111)-textured polycrystalline diamond, which had high crystallinity and improved stress properties. The average stress was 147 MPa (tensile) and the uniformity was less than or equal to+21.1%;−12.2%was achieved within a 50-mm-diam area for a 2.3-μm-thick film. The biaxial Young’s modulus was evaluated by the bulge test, and was found to be1000±51 GPa.This diamond membrane caused little in-plane distortion-induced backetching, i.e., max(x,y)=(27,31) nm,due to its high biaxial Young’s modulus.

ISSN:1071-1023    

DOI:10.1116/1.590027

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

The dc prebreakdown and breakdown characteristics of micrometric gaps varying from 25 to 1000 μm, between highly polished 2 cm diam spherical electrodes, were extensively investigated at∼10−6Torr. The current–voltage characteristics of the above gaps obey Fowler–Nordheim behavior, confirming that the prebreakdown conduction was dominated by high field electron tunneling. The breakdown voltage derived from the prebreakdown data took the form of a power relation of gap distance asVb=Kdα. Experimental results showed that highly polished metal electrodes can withstand very high fields in relatively poor vacuum: 220 V/μm for a 50 μm gap, 130 V/μm for a 300 μm gap. The breakdown of a narrow (⩽ 200 μm) gap resulted in rapid degradation, causing damage to both anode and cathode, while wider gaps (400–1000 μm) were found to exhibit spark conditioning, with the dc breakdown voltage increasing after each successive breakdown, causing damage only to the anode. A dc-glow-discharge treatment improved the gap insulation capability significantly and could recover the degraded gap insulation capability caused by spark discharge breakdown in small gaps. The experimental results also showed that the electrode surface roughness per se does not play a key role in influencing the breakdown characteristics after the dc glow-discharge pretreatment.

ISSN:1071-1023    

DOI:10.1116/1.590028

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

It was obtained experimentally that the fluctuation of the field emission current was increased as the anode was approached to the emitter, under a low level of the vacuum condition. It is numerically solved that the number of generated gas molecules and ions by electron stimulated desorption on the anode surface come to the emitter surface. Under ultrahigh vacuum, the number was not so different for the distance. On the other hand, under low level vacuum condition, the number was increased largely as the anode approached the emitter. So the fluctuation can be increased when the anode approaches the emitter under low level vacuum condition.

ISSN:1071-1023    

DOI:10.1116/1.590226

出版商:American Vacuum Society    

年代:1998

数据来源: AIP