St. Georgiev

Glow discharge deposition of chlorinated and hydrogenated amorphous silicon films from SiCl4SiH4

Abstract a-Si:H:Cl films were prepared by glow discharge of the SiCl 4 SiH 4 mixtures in a planar plasma reactor. IR spectroscopy, optical absorption and electrical and photoelectrical measurements (at room temperature) were used for characterization of the deposited films. The configuration Si 3 HCl was determined as a dominant chlorine containing group in the silicon matrix. The increase of chlorine concentration in the amorphous silicon led to a decrease in optical absorption and to a weak increase in photoconductivity. The optical band gap increased when amorphous silicon was increasingly chlorinated. Dark conductivity as well as photoconductivity of a-Si:H:Cl was low as compared to a-Si:H.

Homogeneous CVD α-Si:H thin film based position sensitive photodetector

Abstract The design, fabrication and characterization of hydrogenated amorphous silicon (α-Si:H) position sensitive photodetectors (PSP) are described. Thin undoped α-Si:H films were deposited by homogeneous chemical vapour deposition using thermal decomposition of silane at low gas pressure. The thin films were characterized by their dark and photoconductivity, optical and CPM measurements. The optical band gap, defect density and photosensitivity were controlled. The PSP had a Schottky-type structure, ITO/α-Si:H/Pd on a glass substrate and their position characteristics at different light probe intensities were measured.

Structural order in a-Si:H:Cl films

Raman measurements of a-Si:H:Cl films have been carried out. The results show that there is an influence of chlorine concentration on the short range order of the amorphous silicon network.

The characteristics of a modified planar-magnetron sputtering source

A modified dc planar-magnetron system for cathode sputtering with an extended central magnetic pole is described. In comparison with the ordinary planar version this system possesses considerable advantages at least for laboratory scale dimensions (diameter less than 100 mm). In the gas pressure range from 10−2 to 10−3 torr the discharge ignition is facilitated and the discharge current is increased by one order of magnitude.

Electrical conductivity in a-Si:H:Cl films

Abstract The temperature dependence of the electrical conductivity was investigated in chlorinated and hydrogenated amorphous silicon films (a-Si:H:Cl) deposited by glow discharge in the SiCl 4 SiH 4 mixtures. The influence of chlorine on the different transport processes is determined according to the investigated temperature range. On the base of the experimental results and the speculative considerations regarding the film structure the inference is drawn that chlorination of hydrogenated amorphous silicon causes a decrease in the gap state density and an increase in the structural disorder. It is supposed that a more definite improvement of the electronical properties of glow discharge amorphous silicon could be expected for the relatively low chlorine concentration of about (1.0–2.0)×10 21 at/cm 3 .

THIN CNX FILMS PREPARED BY VACUUM RAPID THERMAL ANNEALING

Abstract The properties of thin CNx layers prepared by rapid thermal annealing (RTA) are compared with CNxlayers obtained from N2 plasma treatment. Carbon films of 6000 A thickness were deposited by magnetron sputtering system on p-type silicon substrates. The samples were treated in an RTA system in N2 atmosphere at a temperature above 800C. Some of the samples were treated in an N2 plasma. The resulting CNx layers were analyzed by XPS (X-ray photoelectron spectroscopy) technique. The concentration of the incorporated nitrogen and carbon in the layer depths were analyzed by consecutive etching and measurement of the XPS spectra. This showed that maximum depth of incorporated nitrogen atoms in the carbon layer after 800C, 1 min RTA in N2 was about 100 A , while in the N2 plasma treated samples a nitrogen concentration of 6% was observed at 150 A . The electrical resistance of the layers rose with increase of the nitrogen concentration in the layers.

Breakdown voltage of silicon chlorine oxides

Abstract The breakdown voltage of Si-SiO 2 structures obtained by thermal oxidation of silicon in a dry oxygen atmosphere with the addition of HCl has been investigated after hydrogen plasma treatment. The measurements are carried out by the specially developed corona discharge technique, which gives the possibility of determining the breakdown voltage of Si-SiO 2 structures without a gate electrode. The results show that the breakdown voltage decreases after plasma treatment. The process of decrease is explained by the creation of oxide traps in the SiO 2 after plasma treatment. It is found that the breakdown voltage depends on plasma power.