摘要:

Cu lines 0.25 μm wide are successfully patterned by high-temperature dry etching without sidewall protection of the deposited films. Use of Cl2gas as a single reactant rather than a mixture of gaseous chlorine compounds is the key to this anisotropic etching. This reactant suppresses the side etching of Cu patterns without creating a residue when the wafer temperature is precisely controlled between 230 and 270 °C. In our fundamental examination by simulation, we found that the thermal reaction rate reaches a minimum at about 200 °C, and this minimum is much lower than the ion-assisted reaction rate in the actual patterning. This peculiar result is due to the transition of the rate-limiting steps which is caused by the depletion of theCuClxlayer on the Cu surface. That is, the formation of Cu3Cl3appears to be a rate-limiting step at temperatures above 200 °C, while the dissociative adsorption of Cl2is a rate-limiting step at lower temperatures. The anisotropy in the actual patterning is attributed to the intrinsic suppression of Cu3Cl3formation at temperatures ranging from 230 to 270 °C.

ISSN:1071-1023    

DOI:10.1116/1.589271

出版商:American Vacuum Society    

年代:1997

数据来源: AIP

摘要:

Schottky barrier junctions of PtSi/Si1−xGexwere produced; the silicide was deposited by co-sputtering on defect-free well-calibrated strained-Si1−xGex(0⩽x⩽0.242)layers. This work is motivated by the fact that it is very difficult to control the formation of well-defined and well-controlled PtSi/Si1−xGexjunctions by reactingPt/Si1−xGexor by using a silicon cap layer. The Schottky barrier heights of these junctions were substantially lower than those ofPtSi/Sijunctions. Different characterization tools were employed for structural characterization. High-resolution multicrystal x-ray diffraction (HR-MCXRD) was used to investigate the sample quality and strain state of the molecular beam epitaxy (MBE) grownSi1−xGexlayers and to accurately determine the Ge fraction in the fabricated junctions. Cross-sectional transmission electron microscopy (XTEM) was applied to investigate the interface roughness. The possible interlayer diffusion was investigated by secondary ion mass spectrometry (SIMS). The variation of the barrier height of the junctions with the Ge fractionxwas studied, and it was found to follow the same change as the band gap of strained-Si1−xGex.Also, and for comparison,Pt/p-Si1−xGexjunctions were produced, and the effect of annealing on electrical characteristics was investigated.

ISSN:1071-1023    

DOI:10.1116/1.589272

出版商:American Vacuum Society    

年代:1997

数据来源: AIP

摘要:

Transmission electron microscopy and x-ray diffraction have been used to study the evolution of the structure during thermal annealing of thin Ni films deposited on ZnSe. 30-nm-thick Ni layers were deposited, and then annealed at temperatures ranging between 300 and 475 °C for 0.5 or 1 h in aN2atmosphere. The as-deposited Ni layer was found to be polycrystalline. Annealing results in Ni diffusion into the ZnSe and outdiffusion of the Zn and Se toward the sample surface. The Se reacts with Ni to formNixSephases at the Ni–ZnSe interface and in the Ni layer. Formation of a metastable tetragonalNixSephase detected after annealing at 425 °C was found to be suppressed at higher annealing temperatures. The cubicNixSephase(x∼1)witha=4.23Å dominates in the samples after annealing at temperatures above 425 °C. Both phases are crystallographically oriented with respect to the matrix so as to provide the best lattice match with the ZnSe.

ISSN:1071-1023    

DOI:10.1116/1.589273

出版商:American Vacuum Society    

年代:1997

数据来源: AIP

摘要:

We report on a novel GaAs metal–insulator–semiconductor (MIS) structure exhibiting the interface state densities in the 9.2×1010eV−1 cm−2with a Si (10 Å)/GaP (12 Å) layer on GaAs. The structure was grown by a combination of molecular beam epitaxy and chemical vapor deposition. The hysteresis and frequency dispersion of the MIS capacitor were lower than 100 mV, some of them as low as 70 mV under a field swing of about ±1.4 MV/cm.Ex situsolid phase annealing around 500–550 °C in N2using rapid thermal annealing was high enough to recrystallize the as-deposited Si interlayer at low temperature (∼300 °C). The 100 kHz frequency response at 77 K suggests that the interface pinning levels are close to the conduction band edge of GaAs. This article reports the first application of a pseudomorphic Si/GaP interlayer to ideal GaAs MIS diodes and exhibits a favorable interface stability with high temperature annealing.

ISSN:1071-1023    

DOI:10.1116/1.589274

出版商:American Vacuum Society    

年代:1997

数据来源: AIP

摘要:

A series of fluoromethylene cyanate ester resins have been synthesized and studied as potential low dielectric resins for microelectronics. Physical properties were observed to change with the fluoromethylene segment length in the monomer. The polymer can be formed from a stable oligomer that is thermally converted in a single step to a crosslinked thermoset. The complex permittivity decreases with the number of fluoromethylenes in the monomer. The dielectric constant changes significantly with then=6 monomer and appears to show very little change for then=8, 10 compounds. The loss tangent appears to have a downward trend with increasing fluoromethylene chain length. Complex permittivities of select systems were studied up to frequencies as high as 40 GHz. Differential scanning calorimetry was used to determine melting points of the monomer series and show them increasing with the fluoromethylene chain length. With a broad exothermic curing reaction between 200 and 300 °C, the process window is sequentially shortened as the number of fluoromethylenes increases. This makes the processing of the larger monomers (i.e.,n=8, 10) very difficult. A comparison of physical properties and ease of processing shows then=6 compound to be an optimum compromise. A prepolymer of then=6system (F6Cy) was made for spin coat processing with a conversion of 30%–40% determined by19FNMR. A 2 h cure at 175 °C was found to crosslink the material sufficiently for potential microelectronic applications. Excellent gap fill was observed via SEM of spin coated test wafers. Contact angle measurements and ASTM tape tests indicate good surface wetting and adhesion.

ISSN:1071-1023    

DOI:10.1116/1.589275

出版商:American Vacuum Society    

年代:1997

数据来源: AIP

摘要:

This article discusses etching and boron diffusion in Si for the purpose of fabricating micromachined devices with high aspect ratio features. The etch rate of Si under various doping conditions in aCl2plasma generated by an electron cyclotron resonance (ECR) source was measured. It was found that lightly boron and phosphorus doped Si were etched at rates of 0.17 μm/min, whereas heavily boron doped Si had a similar etch rate of 0.16 μm/min. Si doped with high phosphorus concentrations had a faster etch rate of 0.31 μm/min. These etch rates were measured for Si etched at 100 W microwave power, 100 W rf power, 3 mTorr, with 20 sccm ofCl2flow, and an ECR source to sample distance of 8 cm. The difference between thep++andn++Sietch rates was more significant when etched at higher microwave power, higher rf power, or higher temperature. The depth of a heavily doped boron diffusion layer was measured for different feature sizes, trench openings, and aspect ratios. The diffusion layer thickness was found to decrease from 2.9 μm at the bottom of 50-μm-wide trenches, to 1.5 μm at the bottom of 2-μm-wide trenches. Diffusion thickness at the bottom of trenches near narrow features was found to increase to 3 μm compared to 2.5 μm for trenches near large features. The diffusion layer on the sides of the trenches for a 30 min boron diffusion at 1175 °C was 3.25 μm thick and was found to be independent of the trench opening and the trench aspect ratio. A deep etch-shallow diffusion process was used to fabricate thick released resonators with a short boron diffusion time. The second dry etch in the deep etch-shallow diffusion process, which is used to etch thep++layer at the bottom of adjacent features, was studied. It was found that this etch successfully removed thep++layer at the bottom of Si trenches in addition to widening the slightly tapered profile near the bottom of the trenches. This process has been applied to the fabrication of micromachined comb drive resonators and micromirrors successfully.

ISSN:1071-1023    

DOI:10.1116/1.589276

出版商:American Vacuum Society    

年代:1997

数据来源: AIP

摘要:

The range profiles of 1.0 MeV P+implanted into silicon with a dose of 1×1015 cm−2at angles of 7°,45°, and 60°were measured by time-of-flight secondary ion mass spectrometry. The longitudinal and lateral range spreads at normal incidence were deduced from the measured profiles at oblique incidence. The measured profiles were systematically shallower and narrower than the TRIM’95(TRansport of Ions in Matter, 1995) predictions, but good agreement can be obtained if the electronic stopping power formula is slightly increased in the higher energy region during the calculations.

ISSN:1071-1023    

DOI:10.1116/1.589277

出版商:American Vacuum Society    

年代:1997

数据来源: AIP

摘要:

Ultraviolet (UV)/ozone cleaning is a promising way of decontaminating silicon wafers for industrial very large scale integrated processing. We have investigated the cleaning process in high-vacuum conditions utilizing a pulsed supersonic valve and an excimer lamp. With this setup, we are able to supply atomic oxygen onto Si surfaces with and without the simultaneous UV light exposure. We have discovered that thermal desorption spectroscopy analysis of the surface adsorbed species shows marked differences in the wafers processed under different conditions in high vacuum. We have confirmed that UV irradiation is a very essential factor in the UV/ozone cleaning process. In addition, we have carried out time-resolved studies of species coming off the wafer surfaces during UV/ozone cleaning, and found that the main by-products are CO,CO2,andH2O.The hydrocarbon removal reaction is not oxygen-supply limited.

ISSN:1071-1023    

DOI:10.1116/1.589278

出版商:American Vacuum Society    

年代:1997

数据来源: AIP

摘要:

Experimental methods are described which enhance performance in spark-gap atomic emission microscopy (SGAEM) experiments. SGAEM is a recent innovation that permits elemental analysis of scanning tunneling microscopy substrates with high spatial resolution while maintaining tip–surface registry. Detectable sparks have been generated with bias pulses as small as 5 V, and intense atomic emission has been observed in such sparks. Small (∼1 nF), high-voltage capacitors and tungsten tips prepared by thermal etching (a new technique described) have been used in these experiments to yield a SGAEM spatial resolution better than 1 μm2, and an absolute detection limit for Cu of less than 25 fmol.

ISSN:1071-1023    

DOI:10.1116/1.589279

出版商:American Vacuum Society    

年代:1997

数据来源: AIP

摘要:

A new concept based on a Fabry–Pérot interferometer for the generation of nondiffracting Bessel beams is described and proposed for potential applications in microlithography such as the fabrication of small isolated patterns. It was experimentally demonstrated that the depth of focus can be increased by a factor of about 2, and simultaneously the transverse resolution improved by a factor of 1.6, when using this technique to image contact holes. The properties of simultaneous imaging of two contact holes were also investigated. It was shown experimentally that, even in the most critical case (when the first diffraction rings overlap), undesirable interference effects between the adjacent contact holes can be eliminated by means of a phase shifting technique.

ISSN:1071-1023    

DOI:10.1116/1.589280

出版商:American Vacuum Society    

年代:1997

数据来源: AIP