摘要:

A structural model for the Al/SiO2interface system after an oxidation–reduction reaction is proposed. Thermal dependence of the initial stages of the Al/SiO2interface formation process is investigated byinsitux‐ray photoemission spectroscopy analysis and secondary ion mass spectrometry measurements of depth profiles. An abrupt interface without any reaction is confirmed when the interface is formed at room temperature. During Al deposition on SiO2at substrate temperatures beyond 300 °C, oxidation–reduction reaction occurs that produces Al2O3and reduces metallic Si at the interface. The reduced Si spreads throughout the entire Al layer uniformly and the thin Al2O3layer acts as a diffusion barrier that limits the reaction in the very vicinity of the interface. This suggests a distinct layer ordering of the reacted system, Al(Si)/Al2O3/SiO2.  

ISSN:0734-2101    

DOI:10.1116/1.578883

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

For the first time, SiO2layers, prepared by direct photochemical‐vapor deposition, were passivated onto HgCdTe substrates using a deuterium (D2) lamp as the ultraviolet and vacuum‐ultraviolet light source. It was found that the refractive index of the SiO2films, grown at 60 °C and 0.5 Torr for a mixture of SiH4and O2, is close to 1.462 (the refractive index of thermal silicon dioxide) when the gas ratio (SiH4/O2) is adjusted to 0.2. Various characterization techniques, such as x‐ray photoemission, Auger‐electron, and Fourier‐transform spectroscopies were used to give a detailed study of the physical and chemical properties of the SiO2thin films. The electrical properties of these SiO2layers were investigated by performing high frequency (1 MHz) capacitance–voltage (C–V) and current–voltage (I–V) measurements, at 77 K. TheC–Vmeasurement shows that the minimum interface state density is 5×1010cm−2 eV−1with a hysteresis smaller than 0.2 V. The maximum dielectric strength observed fromI–Vmeasurement is around 580 kV/cm.

ISSN:0734-2101    

DOI:10.1116/1.578862

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

Fabrication of electrical contacts in semiconductor device technology can be hampered by the presence of thin oxide layers that may form at the bottom of the contact or via holes as a consequence of the reactive ion etching process. In order to achieve low contact resistances after metallization this oxide thickness must be below some critical value. This article describes a method based upon Auger electron spectroscopy for the thickness determination of such thin oxide films at the bottom of micron‐sized contact holes prior to metallization. In this technique, the different SiKLLline shapes of elemental and oxidized silicon are utilized for fitting the measured spectrum with a superposition of Si and SiO2spectra; the oxide thickness follows from the fitting coefficients. The method is applicable to oxide thicknesses up to ∼10 nm and to contact holes with aspect ratios below ∼1. Systematic errors due to scattering and shadowing effects, and to electron‐beam induced damaging are discussed. The method has proven to be extremely important in optimizing reactive ion etching processes.

ISSN:0734-2101    

DOI:10.1116/1.578907

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

A technique for precisely aligning structures before a Au–Si eutectic bond has been developed. A (100) silicon wafer is anisotropically etched to create v grooves around the periphery of the structure to be bonded. Gold is then deposited onto one of the wafers prior to dicing into individual die. Optical fibers are used as precision locating keys and align the structure when it is assembled. The entire structure is then placed onto a hot chuck at 400 °C. An ultrasonic transducer is used to aid the Au–Si bond. The fibers may be removed after bonding. Current results have shown a maximum misalignment of 5 μm for a 1 cm×1 cm die. This accuracy is achieved with the entire assembly being done by hand without the aid of a microscope or micropositioners. This technique allows a sensor die to be precisely bonded to an electronics die.

ISSN:0734-2101    

DOI:10.1116/1.578882

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

On a clean Si(111)‐7×7 surface, Ge grows in the Stranski–Krastanov mode. At 300–450 °C, relaxed islands begin to form when the Ge growth is 6 monolayers (ML) thick. When Ge is grown on a Pb/Si(111)‐√3×√3 surface, Pb segregates on the surface and agglomerates into two‐dimensional islands. And the critical thickness for the formation of relaxed island becomes 4 ML. This change in critical thickness is explained by Pb reducing the surface energy or by an improved crystallinity of Ge layers (due to a simplified substrate surface reconstruction), or by both.

ISSN:0734-2101    

DOI:10.1116/1.578890

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

Cr and Al were evaporated onto Teflon PFA (polytetrafluoroethylene−co‐perfluoroalkoxy vinyl ether) substrates by electron beam evaporation.Insitux‐ray photoelectron spectroscopy revealed that Cr deposition leads to defluorination and the formation of fluoride and carbide species. The concentrations of fluoride and carbide increased with deposited Cr thickness, slowly at the initial stages of deposition but more rapidly afterwards. Al deposition was qualitatively similar to that of Cr, although the concentrations of fluoride and carbide formed were much lower. The sticking coefficients of both metals, low at the outset of metal deposition, were enhanced after initial deposition, with simultaneous increases in interfacial reactions. Oxygen contaminants in the form of metal oxides were observed, particularly in the case of Al.

ISSN:0734-2101    

DOI:10.1116/1.578900

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

The composition of photochemical native oxides grown on Hg1−xCdxTe (x=0.3) has been studied using x‐ray photoelectron spectroscopy (XPS) and Rutherford backscattering spectroscopy (RBS). By analyzing and comparing the results of the XPS and RBS depth profiles, a simple method of multiplying the XPS raw counts has enabled a realistic XPS depth profile to be obtained without having to directly account for sensitivity factors or preferential sputtering of elements. Photochemical oxides grown in O2ambients were found to have a Hg rich surface layer in addition to a higher Hg concentration throughout the oxide film when compared to layers grown in an N2O ambient. For both growth processes, the bulk oxide regions had Cd/Te ratios in excess of that for the underlying mercury cadmium telluride (MCT) substrate and concomitantly lower Hg/Te ratios. Comparisons with other work indicate that the photochemically grown oxides are quite similar to anodically grown oxides in terms of oxide /MCT interface widths and oxide compositions.

ISSN:0734-2101    

DOI:10.1116/1.578901

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

Interaction of Cr, Ti, Al, Ag, Au, and Cu with Teflon PFA (polytetrafluoroethylene‐ co‐perfluoroalkoxy vinyl ether) and FEP (fluoroethylene propylene), and the effect of x‐ray irradiation on the metal/polymer interfaces, were studied usinginsitux‐ray photoelectron spectroscopy (XPS) and mass spectrometry. Cr, Ti, and Al were found to react with both PFA and FEP, leading to polymer surface graphitization and formation of carbide and fluoride species, which are enhanced at higher metal thicknesses. On the other hand, evaporation of Au, Ag and Cu causes only a slight loss of fluorine, but no chemical interaction occurs. Post‐deposition x‐ray irradiation does not promote metal–polymer interactions, but it leads, in the case of reactive metals, to a pronounced increase of the C–CFnpeak intensity, which rises with the metal thickness. A mechanism based on radical recombination reaction and accumulation of the small fragments, inside the metal film and/or near the metal/polymer interface, is proposed to explain this behavior. The metal XPS signal decreases upon x‐ray exposure, which is interpreted by diffusion of metals into the polymer matrix. The relative change in XPS signal is enhanced at longer x‐ray irradiations, but decreases at a higher metal thickness. This effect is most pronounced for Cu, Cr, and FEP.

ISSN:0734-2101    

DOI:10.1116/1.578902

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

The surfaces of evaporated CuInS2films were investigated by photoelectron spectroscopy (XPS) with respect to stoichiometry dependent features. The surface composition of In‐rich CuInS2films drastically exceeds the respective bulk value determined by energy dispersive x‐ray fluorescence and displays the formation of an In‐rich surface layer with a cation ratio of In/(In+Cu)=0.75(2). Sputter profiles obtained by Auger electron spectroscopy confirm the effect of In enrichment and Cu depletion on the surface. The altered surface region is estimated to extend approximately 0.1μm into the film. Films with a Cu‐rich bulk composition also exhibited In‐rich surfaces, but in addition the segregation of a CuS phase is concluded from XPS investigations. The interrelation of these observations is discussed using simple model considerations.

ISSN:0734-2101    

DOI:10.1116/1.578857

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

The electronic surface structure of evaporated CuInS2films with different stoichiometries was investigated by photoelectron spectroscopy [x‐ray and ultraviolet (XPS and UPS, respectively)]. The Fermi level position is observed to vary fromEF−EV=1.3 eV for the In‐rich toEF−EV=0.0 eV for the Cu‐rich films. Valence band spectra of In‐rich films can be interpreted according to theoretical band structure calculations in the literature. The electronic surface structure of Cu‐rich films is determined by a CuS phase segregation which is displayed by an additional valence band emission structure. This phase is responsible for the semimetallic character of the Cu‐rich films. A comparison of the energy level positions of Cu‐rich and In‐rich films is given according to a simple model. The removal of CuS by a KCN treatment is indicated by the complete recovery of the CuInS2valence band structure. As a consequence highly efficient solar‐to‐energy conversion can be obtained from CuInS2films of a wide as‐deposited Cu‐rich composition range.

ISSN:0734-2101    

DOI:10.1116/1.578858

出版商:American Vacuum Society    

年代:1994

数据来源: AIP