Low resistance ohmic contacts (ρc = 7 x 10-5 Ω-cm2) have been fabricated to Zn-doped p-type InP using an annealed Pd/Zn/Pd/Au metallization. Palladium reacts with InP at low
temperatures to form a Pd2InP ternary phase, which is initially amorphous but crystallizes and grows epitaxially on InP. Zinc reacts with some of the
overlying Pd to form PdZn (≅250° C), which decomposes at 400-425° C to form PdP2, freeing up Zn to diffuse into Au as well as InP. The contact resistance reaches a minimum as the decomposition reaction
takes place. The resultant ohmic contact is laterally uniform and consists of epitaxial Pd2InP adjacent to InP, followed by a thin layer of PdP2 and then the outer Au layer. Further annealing leads to a breakdown of the contact structure,i.e. decomposition of Pd2InP, and an increase in contact resistance. 相似文献
The properties of TiN/TiSi2 bilayer formed by rapid thermal annealing (RTA) in an NH3 ambient after the titanium film is deposited on the silicon substrate is investigated. It is found that the formation of
TiN/TiSi2 bilayer depends on the RTA temperature and a competitive reaction for the TiN/TiSi2 bilayer occurs at 600°C. Both the TiN and TiSi2 layers represent titanium-rich films at 600°C anneal. The TiN layer has a stable structure at 700°C anneal while the TiSi2 layer has C49 and C54 phase. Both the TiN and TiSi2 layers have stable structures and stoichiometries at 800°C anneal. When the TiN/TiSi2 bilayer is formed, the redistribution of boron atoms within the TiSi2 layer gets active as the anneal temperature is increased. According to secondary ion mass spectroscopy analysis, boron atoms
pile up within the TiN layer and at the TiSi2−Si interface. The electrical properties for n+ and p+ contacts are investigated. The n+ contact resistance increases slightly with increasing annealing temperature but the p+ contact resistance decreases. The leakage current indicates degradation of the contact at high annealing temperature for
both n+ and p+ junctions. 相似文献
Resistivity and Hall mobility measurements were performed on Pd2Si films grown on <100〉 and <111〉 oriented silicon substrates as a function of temperature and thickness of the films. The results show that Pd2Si has metallic character. The Debye temperature of Pd2Si was found to be 120±20°K and the concentration of the charge carriers, which are electrons, is 4 × 1021 cm?3. The bulk value of the resistivity at room temperature is 25–30 ωΩcm and the Hall mobility is 50–60 cm2 V?1 sec?1, both depending on the structure of Pd2Si which is known to be epitaxial on <111〉 substrate but not on <100〉 substrate. This structural difference is clearly reflected by the electrical characteristics. 相似文献
Based on a theoretical analysis of the temperature dependence of the contact resistance Rc for an Au-Ti-Pd2Si-n+-Si ohmic contact, a current-transfer mechanism explaining the experimentally observed increase in Rc in the temperature range 100–380 K is proposed. It is shown that microwave treatment of such contacts results in a decrease
in the spread of Rc over the wafer and a decrease in the value of Rc whilst retaining an increase in Rc in the temperatures range 100–380 K. 相似文献
The specific contact resistance ρc of Al and Pd2Si contacts has been measured on p- and n-Si substrates of uniform resistivity. The variation of ρc with substrate resistivity is described by the following equations: The specific contact resistance of Al contacts was found to be lower than the values of Pd2Si contacts on p-Si. Pd2Si contacts on both n- and p-Si, (111) orientation, become non-ohmic in the resistivity range .The data in this study are not sufficient to distinguish a variation in ρc with substrate orientation. Specific contact resistance values of Pd2Si contacts on and were not significantly different from values expected for the (111) substrates. 相似文献
Backscattering spectrometry with 2.3 and 2.0 MeV 4He+ have been used to study the role of Cr as a barrier in the interaction of Pd2Si with Al. Samples of palladium silicide (Pd2Si) grown on Si 〈100〉 single crystal and Al evaporated on top, in that order, showed a substantial intermixture of Pd2Si and Al, and a non-uniform erosion of the Pd2SiSi interface when heated between 300 and 450°C. With a thin layer of Cr(300–1500 Å) interposed between Pd and Al intermixing of Pd2Si and Al was suppressed for temperatures up to 500°C and times up to 2 hr. In these samples distinct sublayers of Pd2Si, CrSi2 and CrAlx (where the values of x depends on the relative thicknesses of Al and Cr) are formed. We have noted that whenever there is a thin unreached Cr layer the spectra of the distinct sublayers show sharp boundaries. 相似文献
Auger electron spectroscopy (AES) combined with in situ sputter etching is used to quantitatively evaluate the growth kinetics of thin films of Pd2Si on 〈111〉 Si substrates. The growth of Pd2Si is found to be diffusion limited and to be characterized by an activation energy of 1·4±0·2 eV in close agreement with previous results obtained on thicker Pd2Si films. AES is also used to uniquely identify the silicide phase Pd2Si. Measurement of the expansion occurring during Pd2Si film formation indicates the Pd2Si film is about 20% thicker than expected. Correlation of the AES results with careful electrical measurements of the Pd2Si/Si interface reveals that the contact barrier energy φBn decreases slightly with increasing thickness of the Pd2Si film. A 3% decrease in φBn was observed for complete conversion of 500 Å of Pd to Pd2Si. 相似文献
The effect of rapid thermally nitrided titanium films contacting silicided (titanium disilicided) and nonsilicided junctions
has been studied in the temperature range of 800 to 900°C. The rapid thermal nitridation of titanium films used as diffusion
barriers between aluminum and silicon, has a major impact on shallow junction complementary metal oxide semiconductor technologies.
During the process of rapid thermal nitridation, the dopants in the junctions undergo a redistribution and affect the electrical
properties of shallow junction structures. This work focuses on using novel contact resistance structures to measure the variation
in electrical parameters for rapid thermally nitrided titanium films annealed at different temperatures. The self-aligned
silicide (salicide) junctions in this study were formed using rapid thermally annealed titanium films. Electrical contact
resistance testers were used to measure the interface contact resistance between the salicide and silicon, as well as between
the metal and the salicide. The results show that the interface contact resistance to the p− diffused salicided junctions increases with rapid thermal nitridation of the additional titanium film, whereas the interface
contact resistance to the n− diffused salicided junction shows a decrease. Further, as a function of the rapid thermal annealing temperature (for fixed
titanium thickness), the nonsalicided diffusions show an increase in the interface contact resistance. The boron profiles
at the TiSi2/Si interface obtained using secondary ion mass spectroscopy show an excellent qualitative agreement with the electrical results
for each of the conditions discussed. The films were also characterized using Rutherford back-scattering spectrometry and
transmission electron microscopy and the results show good agreement with the measured variation in electrical parameters.
These results also show that as the anneal temperature is increased, the TiN thickness increases, further the change in the
silicide/silicon interface position with the nitridation of the additional titanium layer was verified.
This work was carried out when the author was working at AT&T Bell Labs 相似文献
A 0.3-μm-thick electrolytic Pd layer was plated on 1 μm of electroless Ni on 1 mm-thick polished and roughened Cu substrates with roughness values (Ra) of 0.08 μm and 0.5 μm, respectively. The rough substrates were produced with sand-blasting. Au wire bonding on the Ni/Pd surface was optimized,
and the electrical reliability was investigated under a high temperature storage test (HTST) during 800 h at 250°C by measuring
the ball bond contact resistance, Rc. The average value of Rc of optimized ball bonds on the rough substrate was 1.96 mΩ which was about 40.0% higher than that on the smooth substrate.
The initial bondability increased for the rougher surface, so that only half of the original ultrasonic level was required,
but the reliability was not affected by surface roughness. For both substrate types, HTST caused bond healing, reducing the
average Rc by about 21% and 27%, respectively. Au diffusion into the Pd layer was observed in scanning transmission electron microscopy/ energy
dispersive spectroscopy (STEM–EDS) line-scan analysis after HTST. It is considered that diffusion of Au or interdiffusion
between Au and Pd can provide chemically strong bonding during HTST. This is supported by the Rc decrease measured as the aging time increased. Cu migration was indicated in the STEM–EDS analysis, but its effect on reliability
can be ignored. Au and Pd tend to form a complete solid solution at the interface and can provide reliable interconnection
for high temperature (250°C) applications. 相似文献
Continuing developments in semiconductor process and materials technology have enabled significant reductions to be achieved in the contact resistance Rc of devices. This reduction is commonly assessed in terms of the specific contact resistance (SCR) parameter ρc (Ω cm2) of the metal–semiconductor interface. Such a reduction in SCR is essential, for as device dimensions decrease, then so also must ρc and the corresponding contact resistance in order not to compromise the down-scaled ULSI device performance. Thus the ability to accurately model contacts and measure ρc is essential to ohmic contact development. The cross kelvin resistor (CKR) test structure is commonly used to experimentally measure the Kelvin resistance of an ohmic contact and obtain the specific contact resistance ρc. The error correction curves generated from computer modelling of the CKR test structure are used to compensate for the semiconductor parasitic resistance, thus giving the SCR value. In this paper the increased difficulty in measuring lower ρc values, due to trends in technology, is discussed. The challenges presented by the presence of two interfaces in silicided contacts (metal-silicide–silicon) is also discussed. Experimental values of the SCR of an aluminium–titanium silicide interface is determined using multiple CKR test structures. 相似文献
An investigation is made into the possibility of providing low resistance contacts to shallow junction InP devices which do
not require sintering and which do not cause device degradation even when subjected to extended annealing at elevated temperatures.
We show that the addition of In to Au contacts in amounts that exceed the solid solubility limit lowers the as-fabricated
(unsintered) contact resistivityRc to the 10-5 ohm-cm2 range. If the In content is made to correspond exactly to that required to form the intermediate compound Au9ln4, then the contacts so formed are stable, both electrically and metallurgically, even after extended annealing (12 hr) at
400° C. We next consider the contact system Au/Au2P3 which has been shown to exhibit as-fabricatedRc values in the 10-6 ohm-cm2 range, but which fails quickly when heated. We show that the substitution of a refractory metal (W, Ta) for Au preserves
the lowRc values while preventing the destructive reactions that would normally take place in this system at high temperatures. We
show, finally, thatRc values in the 10 ohm-cm2 range can be achievedwithout sintering by combining the effects of In or Ga additions to Au contacts with the effects of introducing a thin Au2P3 layer at the metal-InP interface. 相似文献
Thermally stable, low contact resistance InAs/Ni/W contacts were previously prepared by sputter depositing InAs, Ni, and W
targets in our laboratory. However, the optimum annealing temperature to provide low contact resistance (Rc) was high, resulting in rough contact surface. In the present experiment, the effects of the In concentrations of InxGa1-x As targets on the optimum annealing temperature to prepare low Rcand the surface morphology of thexGa1-x/ W contacts were studied. In addition, the electrical properties and the interfacial microstructure were correlated to search
the optimum In concentration to provide the minimum Rc, where the interfacial microstructure was analyzed by x-ray diffraction and transmission electron microscopy and the contact
resistances (Rcc) were measured by the transmission line method. The optimum annealing temperature to provide minimum Rc was reduced by 150°C by using the In0.7Ga0.3As targets instead of the previous targets. The contact resistance of 0.4 Ω-mm was obtained for the In0.7Ga0.3As/Ni/W contacts after annealing at temperatures of around 600°C. The Rc values did not deteriorate after annealing at 400°C for 2 h. Also, the surface of this contact was smooth and no evidence
of In outdiffusion on the contact surface was seen. Finally, the effect of the In concentrations at the metal/GaAs interfaces
on the electrical properties will be discussed. 相似文献
We have investigated the electrical properties and interfacial reactions of the Si/Ti-based ohmic contacts to Si-doped n-GaN grown by metal organic chemical vapor deposition and the electrical properties were related to the material reactions. Si/Ti contact system was selected because Ti silicides have a low work function comparable to Al and also Si was used widely as an n-type dopant. As the annealing temperature increased, the specific contact resistance of Si/Ti-based ohmic contacts decreased and showed minimum contact decreased and showed minimum contact resistance as low as 3.86 10?6 cm2 after annealing at 900°C for 3 min under N2 ambient. Our experimental results show that the ohmic behavior of Si/Ti-based contact, were attributed to the low barrier height of Ti-silicide/GaN interface, which was formed through the interfacial reaction between Si and Ti layers. In order to clarify the current conduction mechanism of Si/Ti-based contact, temperature dependent contact resistance measurement was carried out for Au(1000 Å)/Ti(400 Å)/Si(1500 Å)/Ti(150 Å) contact system after annealing at 700°C for 3 min. The contact resistance of Si/Ti-based ohmic contact decreased exponentially with the measuring temperature and so it can be concluded that current flows over the low barrier height by thermionic emission. 相似文献
Pd-Ge based ohmic contact to n-GaAs with a TiW diffusion barrier was investigated. Electrical analysis as well as Auger electron
spectroscopy and the scanning electron microscopy were used to study the contact after it was subjected to different furnace
and rapid thermal annealing and different aging steps. All analyses show that TiW can act as a good barrier metal for the
Au/Ge/Pd/n-GaAs contact system. A value of 1.45 × 10−6 Ω-cm2 for the specific contact resistance was obtained for the Au/TiW/Ge/Pd/n-GaAs contact after it was rapid thermally annealed
at 425°C for 90 s. It can withstand a thermal aging at 350°C for 40 h with its ρc increasing to 2.94 × 10−6Ω-cm2 and for an aging at 410°C for 40 h with its ρc increasing to 1.38 × 10−5 Ω-cm2. 相似文献
Anomalous temperature dependences of the specific contact resistance ρc(T) of Pd2Si-Ti-Au ohmic contacts to lapped n-Si with dopant concentrations of 5 × 1016, 3 × 1017, and 8 × 1017 cm?3 have been obtained. The anomalous dependences of ρc(T) have been accounted for under the assumption that the current flows along nanodimensional metallic shunts, which are combined with dislocations with a diffusionrelated limit in the supply of charge carriers taken into account. The densities of conducting and scattering dislocations in the surface region of the semiconductor are determined. 相似文献
In this paper two types of Al/Ti-based Ohmic contacts to Gallium Nitride (GaN) based devices are presented; ImplantedN+GaN (like the ones found in the Source/Drain of GaN Metal Oxide Semiconductor Field Effect Transistors-MOSFET) and heterojunction (HJ) AlGaN/GaN contacts (Source/Drain of High Electron Mobility Transistors-HEMT). Sheet resistance (Rsh) and contact resistance (Rc) have been investigated in the temperature (T) range of 25-250 °C. It was found that the Rsh (850/700 Ω□) (25/250 °C) and Rc (2.2/0.7 Ωmm) decrease with T for ImplantedN+GaN contact and Rsh (400/850 Ω□) and Rc (0.2/0.4 Ωmm) (weakly for Rc) increase with T for HJAlGaN/GaN contact. Numerical computation based models are used to determine the theoretical Rsh and Rc behavior with T and to fit the experimental values. 相似文献
The ohmic contact formation mechanism and the role of Pt layer of Au(500Å) Pt(500Å)/Pd(100Å) ohmic contact to p-ZnTe were investigated. The specific contact resistance of Au/Pt/Pd contact depended strongly on the annealing temperature. As the annealing temperature increased, the specific contact resistance decreased and reached a minimum value of 6×10?6 Θcm2 at 200°C. From the Hall measurement, the hole concentration increased with the annealing temperature and reached a maximum value of 2.3×1019 cm?3 at 300°C. The Schottky barrier height decreased with the increase of annealing temperature and reached a minimum value of 0.34 eV at 200°C and it was due to the interfacial reaction of Pd and ZnTe. Therefore, the decrease of contact resistance was due to the increase of doping concentration as well as the decrease of Schottky barrier height by the interfacial reaction of Pd ZnTe. The specific contact resistances of Au Pd, Au/Pt/Pd and Au/Mo/Pd as a function of annealing time was investigated to clarify the role of Pt layer. 相似文献
Refractory NiGe ohmic contacts which have excellent thermal stability and smooth surface have been developed. To apply these
contacts to the future very large scale integration GaAs devices, reduction of the contact resistance (Rc) of the NiGe contacts is mandatory. In the present paper, in order to obtain a guideline for the Rc reduction, the formation mechanism of the NiGe contacts was investigated. The NiGe contacts were found to have two different
ohmic contact formation mechanisms. These mechanisms suggested that facilitation of heavy doping at the GaAs surface and/or
in the Ge layer was very effective to reduce the Rc values of the NiGe contacts. Experimentally, the Rc reduction was demonstrated by adding a small amount of third elements. Direct doping elements (Sn, Sb, and Te) and indirect
doping elements (Pd, Pt, Au, Ag, and Cu) were chosen as the third elements. In additon, the effect of addition of In, which
forms alow barrier layer between metal and GaAs, was investigated. The contact resistance of these NiGe-based contacts were
close to 0.3 Ω mm, and they provided smooth surface and shallow reaction depth. Finally, the NiGe-based contacts were compared
with the conventional AuGeNi contact. 相似文献
Recently, in order to improve the energy conversion efficiency of direct polyol fuel cells, the engineering of effective Pd‐ and/or Pt‐based electrocatalysts to rupture C? C bonds has received increasing attention. Here, an example is shown to synthesize highly uniform sub‐10 nm Pd‐Cu‐Pt twin icosahedrons by controlling the nucleation phase. Because of the synergies of the electronic effect, synergistic effect, geometric effect, and abundant surface active sites originating from the formation of near surface alloy and special icosahedral shape, the Pd‐Cu‐Pt twin icosahedrons exhibit excellent electrocatalytic performance in glycerol electrocatalysis at the operating temperature of direct alcohol fuel cells (70 °C) in KOH electrolyte. The Pd50.2Cu38.4Pt11.4 icosahedrons show mass activities of 9.7 A mg?1Pd+Pt and 13.7 A mg?1Pd. Furthermore, the Pd50.2Cu38.4Pt11.4 icosahedrons demonstrate long‐term durability in current–time test for 36 000 s and high in situ anti‐CO poisoning performance. In addition, the introduction of CO can enhance electro‐oxidation endurance on Pd50.2Cu38.4Pt11.4 icosahedrons, and the peak mass activity can reach to 14.4 A mg?1Pd+Pt. The in situ Fourier transform infrared spectroscopy spectra indicate that the Pd50.2Cu38.4Pt11.4 icosahedrons possess a high capacity to break C? C bonds and may efficiently convert glycerol into CO2, thus improving the utilization efficiency of energy‐containing molecule glycerol. 相似文献