Jiun-Tsuen Lai

EFFECTS OF COMPOSITION ON THE FORMATION TEMPERATURES AND ELECTRICAL RESISTIVITIES OF C54 TITANIUM GERMANOSILICIDE IN TI-SI1-XGEX SYSTEMS

The effects of alloy composition on the formation temperature and electrical resistivities of C54 titanium germanosilicide formed during the Ti/Si1−xGex (x=0, 0.3, 0.4, 0.7, 1) solid state reaction have been investigated. Ti5(Si1−yGey)3, C49– and C54–Ti(Si1−zGez)2 were observed to form in the Ti/Si1−xGex (x⩾0.4) systems. On the other hand, Ti6(Si1−yGey)5 and C54–Ti(Si1−zGez)2 were found in the Ti/Si1−xGex (x≧0.7) systems. For both cases, the relationship of x>y>z was found. The appearance and agglomeration temperature of low-resistivity C54–Ti(Si1−zGez)2 were both found to decrease with the Ge concentration. The resistivities of C54–Ti(Si1−zGez)2 were measured to be 15–20 μΩ/cm. The segregation of Si1−wGew (w>x) was found in all samples annealed above 800 °C. The effects of thermodynamic driving force, kinetic factor, and composition of the micro-area are discussed.

Pd/Ge ohmic contacts to n‐type GaAs formed by rapid thermal annealing

Pd/Ge ohmic contact to n‐type GaAs is obtained by using the rapid thermal annealing (RTA) method. The best specific contact resistivity of ohmic contacts annealed at 400–500 °C is on the order of 10−6 Ω cm2. Secondary ion mass spectrometry (SIMS) measurement shows that these ohmic contacts are very shallow. Gallium dissociation from GaAs is observed. It is found that there is a correlation between a gallium SIMS signal bump and good ohmic contact behavior. A model is proposed for this phenomenon. This RTA ohmic contact method has been successfully applied to the fabrication of charge injection transistor/negative resistance field‐effect transistor devices.

ALGAAS/GAAS CHARGE INJECTION TRANSISTOR/NEGATIVE RESISTANCE FIELD-EFFECT TRANSISTOR FABRICATED WITH SHALLOW PD/GE OHMIC CONTACTS

AlGaAs/GaAs charge injection transistor (CHINT)/negative resistance field‐effect transistor (NERFET) devices are fabricated with Pd/Ge ohmic contacts. Pd and Ge are deposited by e‐beam evaporation. The contact metal layers are annealed by rapid thermal annealing at 450–500 °C for 1 min. This gives a shallow ohmic contact and low specific contact resistivity. The better ρc are on the order of 10−6 Ω cm2. Using Pd/Ge contacts and rapid thermal annealing method, the metallization of CHINT/NERFET becomes much less critical. Good device performance under NERFET mode and CHINT mode is achieved. The largest peak‐to‐valley ratio of NERFET is about 15 at room temperature. The process developed in this work considerably simplifies the fabrication of CHINT/NERFET devices.

POLARITY EFFECT ON FAILURE OF NI AND NI2SI CONTACTS ON SI

Stability of contacts in shallow junction devices against high current density is a reliability issue for very large scale integration technology. We have observed a strong polarity effect on failure at nickel and nickel silicide contacts on both n- and p-type Si under high stress conditions. In a pair of cathode and anode contacts the Ni/n+-Si contact pair fails at the anode, while the Ni/p+-Si pair fails at the cathode. The Ni/Ni2Si/n+-Si and Ni/Ni2Si/p+-Si were found to fail preferentially at the cathode. Microbeam Rutherford backscattering spectrometry and Auger electron spectroscopy depth profiles show that a silicide reaction occurs between Ni and Si during current stressing, especially at the failed contacts. In situ resistance data indicate that the resistance of the failed contact increases with time while that of the other contact in the pair remains constant. Transmission electron microscopy shows that the silicide formation is not uniform at the damaged contacts. A mixture of dominant epitaxia...

Phase formation and electrical resistivity of ultrahigh vacuum deposited Cu thin films on epitaxial Si–Ge layers on Si and Ge

The phase formation and the morphological stability of e1-Cu3Ge and e1-Cu3(Si1−xGex) in Cu/epitaxial-Ge(e-Ge)/(111)Ge, Cu/(001)Ge, Cu/e-Ge/(111)Si, and Cu/(001)Si–Ge alloys have been investigated by transmission electron microscopy in conjunction with the energy dispersive spectrometry as well as by sheet resistance measurement. Epitaxial Cu and epitaxial ζ-Cu5Ge were found to form in as-deposited Cu/e-Ge/(111)Ge and Cu/e-Ge/(111)Si. On the other hand, textured Cu was found to form in the other systems. Polycrystalline e1-Cu3Ge and e1-Cu3(Si1−xGex) were the only phases formed in 150–500 °C annealed Cu/Ge and (Cu/e–Ge/Si and Cu/Si–Ge alloys) systems, respectively. They were found to agglomerate at 550 °C. The room-temperature oxidation of substrate in the presence of Cu3(Si1−xGex) was found only in the Cu/Si0.7Ge0.3 system. From the sheet resistance measurement, e1-Cu3Ge has the lowest resistivity of 7 μΩ cm after 400 °C annealing. The electrical resistivity was found to decrease with the Ge content.

FORMATION OF AMORPHOUS INTERLAYERS BY SOLID-STATE DIFFUSION IN TI THIN FILMS ON EPITAXIAL SI-GE LAYERS ON SILICON AND GERMANIUM

The formation of amorphous interlayers (a‐interlayers) by solid‐state diffusion in ultrahigh‐vacuum‐deposited polycrystalline Ti thin film on germanium and epitaxial Si1−xGex (x=0.3, 0.4, and 0.7) alloys grown on (001)Si has been investigated by transmission electron microscopy and Auger electron spectroscopy. Amorphous interlayers, less than 2 nm in thickness, were observed to form in all as‐deposited samples. The growth of the a‐interlayers was found to vary nonmonotonically with the composition of Si–Ge alloys in annealed samples. On the other hand, the formation temperature of crystalline phase was found to decrease with the Ge content. The results are compared with those of the Ti/Si system.

Ion beam induced formation of metastable fcc-Ti phase in the epitaxial Ti/Cu/(111)Si structures

Abstract Epitaxial Ti/Cu/(111)Si structures have been grown in ultrahigh vacuum. Mutual epitaxial growths of Ti on Cu on Ti were found even though the mismatch is as large as 15.3%. Ar + bombardment was found to induce the transformation of epitaxial hcp-Ti into epitaxial metastable fcc-Ti as well as the formation of rod-like TiO. Mechanisms for the ion beam induced phase transition are discussed.

Ultrahigh and controllable drain current peak-to-valley ratio in negative resistance field-effect transistors with a strained InGaAs channel

Negative resistance field-effect transistor (NERFET) devices using either strained InGaAs or unstrained GaAs channel layers have been fabricated. The strained InGaAs channel NERFETs show strong negative differential resistance and large drain current peak-to-valley ratio. The peak-to-valley ratio of the InGaAs channel NERFET is more than 3000 at room temperature and larger than one million (10/sup 6/) at 77 K. The peak-to-valley ratio is controllable by adjusting the collector voltage.<<ETX>>

Low contact-resistance and shallow Pd/Ge ohmic contacts to n-In0.53Ga0.47As on InP substrate formed by rapid thermal annealing

Shallow Pd/Ge ohmic contacts to n-type In0.53Ga0.47As with low specific contact resistivity are obtained by the rapid thermal annealing method. For samples annealed at 425°C for 30 s, the lowest resistivity value is 6.66×10-8 Ωcm2 and the average value is 1.4×10-6 Ωcm2. For samples annealed at 425°C for 60 s, the lowest resistivity value is 2.13×10-7 Ωcm2 and the average value is 8.6×10-7 Ωcm2. Secondary ion mass spectrometry (SIMS) analysis shows that the ohmic contact is very shallow. It is found that there is a correlation between gallium and indium SIMS signal bumps and good ohmic contact behavior.

High-resolution transmission electron microscopy of phase formation and growth in metal–Si–Ge systems

High-resolution transmission electron microscopy (HRTEM) in conjunction with nano-beam (NB) analysis as well as energy dispersive spectrometry analysis have been fruitfully utilized to study the interfacial reactions in the metal-Si-Ge systems. In this paper we report the results of TEM study of the phase formation and growth in Ti-Si-Ge, Cu-Si-Ge and Ni-Si-Ge systems.