Antimony-doped Films Research Articles

(Invited) Activation and Deactivation in Ultra-Highly Doped n-Type Epitaxy for nMOS Applications

In last 15 years, n-type doped selective epitaxy in source and drain (S/D) for nMOS have been heavily investigated. Initial interests for nMOS S/D epitaxy were focused on carbon and phosphorus doped Si:CP film for channel strain engineering and was adapted in production. In 2012, another type of ultrahigh phosphorus doped Si:P was proposed as a replacement for Si:CP for tensile engineering. With as high as 4.5E21 doping level, such Si:P film showed comparable strain as Si:CP with 2% substitutional carbon, but with much simpler process design and quickly accepted by the industry. These ultra-high doped Si:P film also promoted interests in the mechanism for such high doping level and high strain level. In last couple years, phosphorus vacancy complexes, particularly P4V, or pseudo-cubic Si3P4, is widely accepted as the key mechanism. Although still under debate, formation of high concentration, phosphorus stabilized vacancy, up to 1E21 or 2%, is also believed to be responsible for the observed high strain. Along the same line, it was quickly discovered that ultrahigh arsenic or antimony doped films are also possible (Fig 1). And high strain Si:As is also observed with a similar strain level as Si:P, with even higher doping level, likely due to the formation of As4V complex. A group V and vacancy complex, V4V complex, is electrically neutral therefore would not contribute to carrier activation. V4V interaction with carrier would be essential to understand activation and deactivation in ultrahigh n-type doped epitaxy film.P-V interaction have been observed in early studies of bipolar device or solar device. It is also extensively studied in late 1990s to understand the USJ formation and activation. To compare with these typically implanted and annealed or diffused data, high doped Si:P and Si:As epitaxy films were deposited at different temperature and annealed with different thermal budget. Our data showed that selective Si:P as grown resistivity v.s. deposition temperature closely follow the equilibrium model based on literatures, indicating selective Si:P film as grown being near thermal equilibrium from active carrier point of view, despite one order magnitude higher P concentration (Fig.2). Selective Si:As, however, showed a different trend, with lower deposition temperature having lower resistivity. To understand the mechanism, non-selective Si:P with fast deposition rate was deposited and then annealed at deposition temperature for different time. it reveals that with fast deposition rate, initial film is activated well beyond thermal equilibrium. But it quickly deactivated within 90sec to near thermal solubility (Fig 3.). Si:As is deactivated at a much slower rate and lead to a different as grown resistivity trend. The energy favored V4V structure requires a minimum temperature to dissolve and activate the carrier. 800C is found not sufficient for Si:P and Si:As requires even higher temperature and thermal budget.To investigate the activation and deactivation, HRXRD and 4-point probe were used to study the strain and carrier concentration evolution during activation and deactivation. Unlike Si:As that always observed higher strain during deactivation from HRXRD, Si:P seems to have multiple paths for deactivation. It is found that depending on active carrier history; for example, low temperature deactivation of active carrier from random capture during epitaxy growth could involve more P4V formation therefore associated with a strain gain (Fig. 3); while for carriers gained from millisecond laser high temperature anneal, post spike annealing sometime involves strain loss during deactivation, possibly via significant interstitial P, on top formation of P4V. P4V formation during deactivation provides a model for transient diffusion enhancement in Si:P with some anneal conditions. As shown in Fig 4, only over-activated sample showed enhanced tail diffusion during 900C spike anneal, probably due to P4V silicon interstitial kick-out effect.To further investigate Si:P activation and deactivation, differential Hall effect measurement (DHEM) was used to obtain the carrier depth profile of different samples. As shown in Fig 5, 1.5E21 to 3E21 total doping level, there is minimum effect of on carrier concentration. One distinct feature on the data is the carrier degradation toward surface. It is possible during the film cool down post deposition, the surface deactivated faster, assisted from the surface flux of interstitial or vacancy. Understand the surface effect on Si:P and Si:As activation deactivation is essential to improve the contact resistance for future nodes. Figure 1

Influence of Thermal Annealing on Structural and Optical Properties of Sb Doped ZnTe Thin Film

Paper presents the influence of thermal treatment on structural and optical characteristics of Sb0.5ZnTe thin film. Alloy of Sb0.5ZnTe has been prepared through traditional and economical melt quenching technique and thin films of prepared alloy was deposited onto glass substrate by thermal evaporation method at pressure of 10–6 Torr. The antimony doped films were annealed for 2 h at three different temperatures ranges (373 K, 393 K and 413 K). Structural characterization of as prepared and annealed film was done by XRD technique and it was found that annealing improves the film crystal structure. UV-Vis spectrophotometer facilitates optical analysis of Sb0.5ZnTe film in wavelength range of 400–1000 nm. It was observed that band gap Eg of the Sb doped film increased while absorption coefficient (α) decrease with increase in heating temperature. These changes in optical properties were explained in terms of defect states.

EFFECT OF ANTIMONY AND FLUORINE DOPING ON ELECTRICAL, OPTICAL AND STRUCTURAL PROPERTIES OF TIN OXIDE FILMS PREPARED BY SPRAY PYROLYSIS METHOD

Undoped, antimony doped and fluorine doped tin oxide films have been prepared by spray pyrolysis technique. The films were deposited on glass substrates at temperatures ranging between 300°C and 370°C by spraying an alcoholic solution of tin tetra chloride ( SnCl 4). Dopants used were antimony tri chloride ( SbCl 3) for antimony doped tin oxide (ATO) films, and ammonium fluoride ( NH 4 F ) for fluorine doped tin oxide (FTO) films. Among undoped tin oxide films, the least resistivity was found to be 3.1 × 10-3 Ω-cm for a molar concentration of 0.75 M. In case of antimony doped films minimum resistivity value was found to be 7.7 × 10-4 Ω-cm for a film with ( Sb / Sn ) = 0.065, deposited at 370°C and in case of fluorine doped films it was found to be 1.67 × 10-3 Ω-cm for a doping percentage of 3 at% of fluorine in 0.1 M solution. The corresponding values of the carrier concentrations were found to be 1.8 × 1020/cm3 and 9.98 × 1020/cm3, respectively. The electrical and optical properties of these films were studied as a function of both doping concentration and substrate temperature. Doping percentage of antimony and fluorine in the spray solution has been optimized for achieving a minimum electrical resistivity. The dependence of electrical properties such as resistivity, carrier concentration and mobility of doped films were analyzed. Influence of antimony dopant on the optical band gap of the films has been reported on the basis of electron conduction mechanism. Air and argon annealing effects on the electrical properties of antimony doped tin oxide films were also studied.

Growth and characterization of antimony doped tin oxide thin films

Pure and antimony doped tin oxide thin films were deposited on glass and quartz plates by spray pyrolysis method. Structural, electrical and optical properties of these films were studied by varying the substrate temperature and antimony concentration. The best electro-optic properties obtained were, resistivity as low as 9×10 −4 Ω cm and average transmission of 80% in the visible region, at the substrate temperature of 400°C with the antimony concentration of 9 at%. While doping, change in preferred orientation was observed from [1 1 0] to [2 0 0]. The optical investigation showed that, depending upon the doping concentration, the antimony doped films had direct allowed transitions in the range 4.13–4.22 eV and indirect allowed transitions in the range 2.54–2.65 eV.