Showing papers on "Van der Pauw method published in 1997"

Method for fabricating semiconductor interconnect having test structures for evaluating electrical characteristics of the interconnect

Abstract: An interconnect for a semiconductor die includes integrally formed test structures for evaluating various electrical characteristics of the interconnect. The test structures can include Kelvin structures, van der Pauw structures, resistors, capacitors, contact chains, via chains, serpentine test structures, and antenna test structures. Among the electrical characteristics that can be evaluated are the resistivity of contact member, conductor and substrate components of the interconnect, contact resistance between the contact members and conductors and capacitance of the contact members and conductors with respect to the substrate.

Nitrogen and aluminum implantation in high resistivity silicon carbide

Abstract: In this article, the results on N and Al implantations into undoped high-resistance and vanadium doped semi-insulating bulk 6H-SiC are reported for the first time. The N implants were performed at 700 °C and the Al implants at 800 °C to create n- and p-type layers, respectively. For comparison, implants were performed into epitaxial layers at the above temperatures and, for N, also at room temperature. The implanted/annealed material was characterized by van der Pauw Hall, secondary ion mass spectrometry, and Rutherford backscattering (RBS) measurements. After annealing, the room temperature N implantation gave similar electrical and RBS results as the 700 °C implantation for a total implant dose of 8×1014 cm−2 which corresponds to a volume concentration of 2×1019 cm−3. The Al implant redistributed in the bulk crystals during annealing, resulting in a shoulder formation at the tail of the implant profile. Lower implant activation was obtained in V-doped material compared to the undoped bulk and epitaxial layers, but the results were promising enough to use implantation technology for making planar high frequency devices in the bulk V-doped substrates, especially as the quality of the substrates continue to improve.

Growth and characterizations of GaN on SiC substrates with buffer layers

Abstract: High quality GaN epitaxial layers were grown on 6H–SiC substrates by using low-pressure metalorganic chemical vapor deposition method. Samples employing a three-period GaN/Al0.08Ga0.92N (100 A/100 A) as a buffer layer produce a good quality GaN epitaxial layer, with mobility and carrier concentration of 612 cm2/V⋅s and 1.3×1017 cm−3 (at 300 K), respectively. The enhanced electron mobility in the Al0.08Ga0.92N/GaN heterostructures is also observed. By using the van der Pauw method of Hall measurement, the sheet carrier density and mobility at 4.2 K for the Al0.08Ga0.92N/GaN heterostructure are 5.8×1012 cm−2 and 5300 cm2/V⋅s, respectively. Strong SdH (Shubnikov–de Haas) oscillations were observed to confirm the two-dimensional electron gas (2DEG) phenomenon at the AlGaN/GaN top heterointerface. In addition, an extra SdH oscillation also resulted from the high-quality 2DEG channel of the GaN/AlGaN bottom heterointerface.

Space-charge controlled conduction in low-temperature-grown molecular-beam epitaxial GaAs

Abstract: Current transport in low-temperature (LT) molecular-beam epitaxial GaAs grown at 200-300 °C on an n+ GaAs substrate is studied by means of current–voltage–temperature characteristics. The resistivity of LT GaAs at low electric fields is ρ⩾108 Ω cm, much higher than resulting from van der Pauw measurements. It is found that the measured resistivity decreases with increasing the LT GaAs thickness. This is explained by space-charge effect in the vicinity of n+/LT GaAs junction and subsequent suppression of hopping conduction in the high-field junction region.

Test structure for monitoring overetching of silicide during contact opening

Abstract: For the contact opening in advanced IC processing, it becomes critical to monitor the degree of overetching of the thin silicide layer and also to obtain the etching rate of the silicide layer. A method is disclosed which will allow the electrical measurements of the sheet resistance of the exposed (by the contact etch) silicide layer, thus allowing electrical measurements to the integrity as well as the thickness of the remaining silicide layer. A main feature of the disclosed test method is a modification of the conventional van der Pauw test structure, or of the cross-bridge structure (which will allow electrical measurement of the line width, in addition to the sheet resistance information). Contrary to the conventional van der Pauw structure or cross-bridge structure where the contact opening pattern is designed to expose only the specific areas needed for allowing electrical connection to the four measurement pads, the contact opening mask is designed to expose some or all of the van der Pauw or cross-bridge structure, thus allowing the electrical measurement of the degree of silicide overetching during contact opening. The disclosed test method and corresponding structure can be applied as an on-wafer process monitor tool following the complete normal process flow, thus serving as a convenient on-wafer monitor.

Rapid thermal annealing of ion implanted 6H-SiC by microwave processing

Abstract: Rapid thermal processing utilizing microwave energy has been used to anneal N, P, and Al ion-implanted 6H-SiC. The microwaves raise the temperature of the sample at a rate of 200°C/min vs 10°C/min for conventional ceramic furnace annealing. Samples were annealed in the temperature range of 1400-1700°C for 2-10 min. The implanted/annealed samples were characterized using van der Pauw Hall, Rutherford backscattering, and secondary ion mass spectrometry. For a given annealing temperature, the characteristics of the microwave-annealed material are similar to those of conventional furnace anneals despite the difference in cycle time.

Transport properties of silicon implanted with bismuth

Abstract: in Van der Pauw structures delineated in Si chips. The measured resistivities were compared with the ones calculated by a generalized Drude approach at similar temperatures and doping concentration, presenting fairly good agreement. The critical impurity concentration Nc of the metal-nonmetal transition was measured to be around 2310 19 cm 23 . The critical concentration Nc was calculated by comparing the ionization energy of the insulating phase with the total energy of the metallic phase. This value of Nc agreed very well with the one obtained experimentally and the values estimated from other theoretical approaches. @S0163-1829~97!01612-3#

Mobility enhancements in AlGaN/GaN/SiC with stair-step and graded heterostructures

Abstract: In this letter, we report the observation of the enhanced electron mobility in three different Al0.08Ga0.92N/GaN heterostructures. These structures were deposited on (0001) 6H-SiC substrates by using the low-pressure metalorganic chemical vapor deposition method. The structure was composed of 500 A AlGaN compositional stair-step layer deposited onto 1.3 μm GaN epitaxial layer. There is a 100 A GaN Cap layer on top of the AlGaN layer to prevent the oxidation of the AlGaN layer. By using the van der Pauw method of Hall measurement, the sheet carrier density and mobility for Al0.08Ga0.92N/GaN heterostructure are 6.6×1012 cm-2 and 5413 cm2/Vs at 77 K, respectively. This high value of mobility is, to the best of our knowledge, the first observed two-dimensional electron gas (2DEG) at the AlGaN/GaN stair-step type of heterostructure. Other interface structures such as graded composition and bulk composition structures were also prepared and 2DEG properties were observed.

Cv and hall effect analysis on neutron irradiated silicon detectors

Abstract: Four contact bulk samples and p + n junction diodes produced from high resistivity n-type silicon wafers of the same ingot have been irradiated with 1 MeV-neutron fluences between 10 12 and 3 × 10 13 cm −2 . The effective impurity concentration N eff has been calculated from CV measurements in irradiated diodes, and bulk resistivity has been measured with the Van der Pauw method on four contact samples. The experimental resistivity and N eff dependence on the irradiation fluence, self-annealing time and storage temperature have been modeled considering the exponential shallow donor decay and the creation of acceptor traps in the irradiated silicon. A numerical fit to the experimental data, based on the solution of the neutrality and Poisson equations, has been carried out considering an equivalent deep acceptor defect created during and after irradiation in the silicon lattice. The energy level and the introduction rate of this defect, evaluated as best-fit parameters in the numerical procedure, are E t = 0.60–0.65eV above the valence band edge defect, evaluated as best-fit parameters in the numerical procedure, are E t = 0.60–0.65eV above the valence band edge and b ∼ 0.06 cm −1 .

Correlations between initial via resistance and reliability performance

Abstract: Accelerated stressing and electromigration (EM) testing were conducted on W-plug via chains and Van der Pauw structures respectively. These populations were chosen to include a wide distribution of initial resistances R/sub 0/. The high-end of the R/sub 0/ distribution exhibited a higher early failure rate and a higher spread in EM time-to-fail distribution. Processes which produce tightly controlled time-zero via resistance distributions are more desirable for via reliability.

Hall effect measurements on proton-irradiated ROSE samples

Abstract: Bulk samples obtained from two wafers of a silicon monocrystal material produced by Float-Zone refinement have been analyzed using the four-point probe method. One of the wafers comes from an oxygenated ingot; two sets of pure and oxygenated samples have been irradiated with 24 GeV/c protons in the fluence range from 10{sup 13} p/cm{sup 2} to 2x10{sup 14} p/cm{sup 2}. Van der Pauw resistivity and Hall coefficient have been measured before and after irradiation as a function of the temperature. A thermal treatment (30 minutes at 100C) has been performed to accelerate the reverse annealing effect in the irradiated silicon. The irradiated samples show the same exponential dependence of the resistivity and of the Hall coefficient on the temperature from 370K to 100K, corresponding to the presence of radiation-induced deep energy levels around 0.6-0.7eV in the silicon gap. The free carrier concentrations (n, p) have been evaluated in the investigated fluence range. The inversion of the conductivity type from n to p occurred respectively at 7x10{sup 13} p/cm{sup 2} and at 4x10{sup 13} p/cm{sup 2} before and after the annealing treatment, for both the two sets. Only slight differences have been detected between the pure and oxygenated samples.

Hole mobility in aluminium implanted silicon

Abstract: The dependence of the hole mobility on the dopant concentration ranging from to was determined at room temperature in Al-implanted Si samples The trend was obtained by the use of Hall effect and resistivity measurements on the van der Pauw pattern in combination with secondary-ion mass spectrometry and spreading resistance analysis The mobility data are in a quite good agreement with the Wagner curve for boron in the high Al concentration region while they approach the Thurber boron curves at low concentrations This result indicates that the neutral and ionized impurity scattering mechanisms are not critically different for Al- and B-doped samples The mobility - dopant concentration curve can be employed to convert the resistivity profiles obtained by spreading resistance measurements into hole concentration distributions for Al-doped samples

Metal-nonmetal transition and resistivity of silicon implanted with bismuth

Abstract: Bismuth was implanted at room temperature in (100)-Si wafers with controlled energy and doses to result in a plateau-like implantation profile. The van der Pauw Si : Bi samples were characterized by the Hall effect and resistivity measurements from room temperature down to 13 K. The electron concentration of the prepared samples at 290 K varied from 3.0 × 1017 to 1.4 × 1020 cm−3. The resistivity of the Si : Bi samples presents a larger enhancement, compared to other dopants, when decreasing the Bi concentration. The metal-nonmetal transition was determined to be around 2 × 1019 cm−3. The calculated values obtained from the Generalized Drude Approach and an equation derived from Kubo formalism agree very well with the experimental data. The results confirm also the behavior ρc (Bi) ρc(P) > ρc(Sb) at 290 K.

Strain-conserving doping of a pseudomorphic metastable Ge0.06Si0.94 layer on Si(100) by low-dose BF2+ implantation

Abstract: A thick (260 nm) pseudomorphic metastable n-type Ge0.06Si0.94 layer grown by molecular beam epitaxy on an n-type Si(100) substrate was implanted at room temperature with 70 keV BF2+ ions to a dose of 3×1013 cm−2, so that a p−n junction was formed in the GeSi layers. The samples were subsequently annealed for 10–40 s in a lamp furnace with a nitrogen ambient, or for 30 min in a vacuum-tube furnace. The samples were characterized by 2 MeV 4He backscattering/channeling spectrometry, double-crystal x-ray diffractometry, transmission electron microscopy, and by Hall effect measurements using the van der Pauw sample geometry. Samples annealed for either 40 s or 30 min at 800 °C exhibit full electrical activation of the boron in the GeSi epilayer without losing their strain. The Hall mobility of the holes is lower than that of p-type Si doped under the same experimental conditions. These results can be attributed to the Hall factor of heavily doped p-type GeSi films which is less than unity while the Hall factor...

Initial Stages of MOCVD Growth of Gallium Nitride Using a Multi-Step Growth Approach

Abstract: A multilayer buffer layer approach to GaN growth has been developed in which the thermal desorption and mass transport of low temperature buffer layer are minimized by deposition of successive layers at increased temperatures. High quality GaN with featureless surface morphology has been grown on (0001) sapphire substrate by metalorganic chemical vapor deposition using this multilayer buffer layer approach. The lateral growth and coalescence of truncated 3D islands (TTIs) nucleated on low temperature buffer layers at the initial stage of overlayer growth is affected by the thickness of the final buffer layer on which nucleation of TTIs takes place. The effect of the thickness of this buffer layer on the quality of GaN is studied by using scanning electron microscopy, van der Pauw geometry Hall measurements and cathodoluminescence and an optimum value of 400A is obtained.

Fabrication of p-β-Fe1−x Mnx Si2/n-Si Heterostructure Diode and their Electrical and Optical Properties

Abstract: We report on the fabrication of p-type β-FeSi2 layers on n-type Si(100) substrates and the investigation of their p-n diode characteristics. Since our undoped β-FeSi2 layers have typically shown n-type conductivity, the p-type layers were formed by the introduction of Mn impurity into β-FeSi2 layers using two types of doping methods; one is an Electron-Beam-Deposition (EBD) procedure of Fe1-xMnxSi2 (X<≈0.1) at room temperature and subsequent annealing at 900°C for 1-120 min, where FeSi2 ingots added with Mn (≈10 %) were used as starting materials. The other is a 55Mn+-implantation into β-FeSi2 layers formed by EBD and subsequent annealing at 850°C for 1-120 min. From van der Pauw measurements, p-type β-Fel-XMnxSi2 layers with the resistivity of 0.0036-0.031 Ω⋅cm and hole mobility of 11.9-89.0cm2/V⋅sec were found to be successfully formed on n-Si substrates by both doping methods. The p-n diode characteristics of these heterostructure diodes were investigated by I-V and C-V measurements. The results indicate that the carrier distribution does not agree with either ideal one-side step or one-side slop junctions, although optical transmittance and reflectance measurements indicate that the silicide/Si interface is of good quality.

Realization of AlGaAs antidot arrays by pulsed laser interference gratings

Abstract: AlGaAs antidot arrays with about 107 antidots are produced by single-shot interference processing with a pulsed high-power Nd:YAG laser system. We apply magnetotransport experiments and atomic force microscopy (AFM) to explore the electronic and geometric properties of the arrays. The size of the antidot arrays are 3 mm×3 mm and the period varies from 400 to 1000 nm. The dots are elliptic or circular and have diameters ranging from 255 to 690 nm. The magnetotransport experiments are performed at 1.5 K in van der Pauw contact configuration. The laser structuring leaves the two dimensional electron density nearly unchanged but decreases the mobility by a factor of about 30. Several maxima are detected in the low magnetic field magnetoresistivity which are discussed based on the geometric data determined by AFM.

Nature of E c −0.37 eV centers and the formation of high-resistivity layers in n-type silicon

Abstract: The DLTS and Van der Pauw methods are used to investigate the production of E c −0.37 eV centers responsible for the formation of high-resistivity layers in n-type Si irradiated with electrons and annealed in the temperature range 80–320 °C. An analysis of the experimental data leads to a conclusion as to the composition of the E c −0.37 eV centers ([V-O-C]) and to the conclusion that their formation is stimulated by a flux of interstitial atoms away from the interface into the interior of the semiconductor during annealing accompanied by the reactions: 1) I+Cs→Ci,Ci+[V-O]→[V-O-C] (dominant reaction); 2) I+V2→V,V+[C-O]→[V-O-C].

EFFECTS OF BALLISTIC TRANSPORT IN WIRES OF n-PbTe

Abstract: We present results of magnetotransport studies on quantum wires of submicron PbTe epilayers, fabricated by means of electron beam lithography and dry etching. When the wire width is reduced down to 1 μm, the transition from diffusive to ballistic regime is observed. Effects associated with collimation and boundary scattering are found in the Ball, longitudinal, and van der Pauw magnetoresistance for wires and junctions in the shape of a cross. PACS numbers: 73.23.Αd, 73.61.—r, 73.50.Dn

Real-time Hall effect measurements of high critical currents epitaxial YBa2Cu3O7−x thin films

Abstract: The Hall effect of thin superconducting YBa 2 Cu 3 O 7−x films was measured in the mixed state (near T c ) and at wide regions of magnetic fields. The method based on the of van der Pauw method was chosen using the measurements geometry of an unsymmetrical cross. It is shown the high quality thin YBCO films with high critical currents ( J c >2 10 6 A/cm 2 ) have a negligible Hall change sign effect in the mixed state.

Process using TiSi/sub 2/ as a shallow contact metallization

Abstract: Because of its low resistivity and excellent thermal stability, TiSi/sub 2/ is finding widespread application as interconnect material in BiCMOS and power devices. The Ti-Si reaction is complex and has been studied in certain regimes. For diminishing the stress a new method for deposition is tried. The thermal conditions were established and the morphology of TiSi/sub 2/ is explored with a X-ray powder diffractometer. TiSi/sub 2/ is formed on Si(100) and Si(111) substrates. The electric performances were determinate by a Van der Pauw structure.

The effect of substrate temperatures on the Hall coefficient of α-Mn thin films

Abstract: Hall coefficient measurements in evaporated α -Mn thin films have been carried out in magnetic fields up to 63 kG in the temperature range between 1.5 and 100 K using the van der Pauw four probe technique. The results show a range of temperature variation of the Hall coefficient ( R H ) depending upon the substrate temperatures used. At high substrate temperatures ( T s > 100 °C) and in high vacuum the sign of R H changes from negative to positive as the temperature is lowered from 100 to 1.5 K, whilst at low substrate temperatures ( T s 30 °C) and in a similar vacuum the sign of R H remains negative. The results of the Hall coefficient in the films are analysed using the two band model of conduction with temperature independent carrier concentrations.