Isotherms of equivalent conductivity, activation energy of ionic migration and molar volume show only slight deviations from linearity for the systems NaN02 + NaN03 CdI2 + CdC12 and KI + NaCl in which the phase diagrams indicate that no intermediate phases occur in the solid state. Similar effects are observed for the system KN03 + KBr for which the phase diagram indicates the formation of incongruently melting KNO3 . KBr.Hence, in all four systems, the molten mixtures do not exhibit any appreciable increase of covalent character compared with the individual molten constituents.

In previously reported work, a conductivity enhancement effect in polycrystalline tin oxide thin films, which are widely used for the front electrodes in flat panel displays, has been achieved by electroplating copper onto the 300 nm high sidewalls of the electrode. Recent experiments show that if an electrolytic reduction is introduced as a surface modification process just before electroplating then excellent adhesion between copper and tin oxide can be achieved. In this paper, the chemical, physical and surface morphological changes of tin oxide electrodes have been characterized by using atomic force microscopy, x‐ray diffraction, x‐ray photoelectron spectroscopy, and surface sheet resistance measurements by a four‐point probe method. The electrolytic reduction was found to result in an increase in the intensity of the x‐ray reflection from the (110) planes of tin oxide, and compositional nonuniformity of the tin oxide surface layers, where metallic tin is trapped at the surface, and oxygen is enriched in the subsurface region. These results, taken together, suggest that the observed adhesion improvement may be due to a combination of tin oxide surface roughening due to preferential etching and the increased (110) orientation, in situ cleaning, and chemical bonding introduced by surface chemical changes.

Large area flat panel displays require high resolution patterning of transparent and high conductivity metal oxides, but the reliability of standard chemical etch techniques at high resolution is inadequate. Tin oxide (SnO2) is a viable alternative to standard In203:Sn (ITO) over large areas but has been ignored due to the lack of a suitable etch process. We have developed an Ar/CI~ reactive ion etch process capable of etching 4 ~m feature sizes and resolutions of 300 lines per inch with rates of up to 90 nm min -1. Emission spectroscopy showed that atomic chlorine is a strong candidate for the active species and that volatile tin chlorides were generated as etch products. Furthermore, the presence of impurity species, particularly hydrogen, was found to be beneficial to the etch rate. Near etch completion, a dramatic decrease in atomic tin emission was observed along with an increase in C1 emission intensity. The etch rate for tin oxide using Ar/C12 was higher than those obtained for ITO using alcohol-based plasmas without the polymer deposition normally associated with organic gas plasmas. Thus the use Ar/C12 etching of SnO2 can provide high resolution transparent conductive electrodes that are uniform over a large area.

An electroplating process has been employed to grow high-quality thin films of copper on tin oxide transparent semiconductor with excellent adhesion. It is shown that electrolysis reduction as a surface modification process prior to the electrodeposition is essential for good adhesion of the resulting copper coating. Experimental results obtained for electrolysis, argon plasma cleaning, and surface roughness measurements indicate that the formation of a monolayer of low valence tin oxide may be significant to the improvements in plating process and deposit adhesion. A mechanism whereby SnOx formation may facilitate improved adhesion is proposed.Tin oxide (TO) and indium tin oxide (ITO) are the most widely used materials for the front electrodes in flat panel displays including liquid crystal (LC), dc or ac-electroluminescent (EL), and plasma (PDP) displays. 1 Response time, brightness uniformity, and power consumption depends critically on electrode line resistance, especially for large-area displays. At present, the best available ITO has 5 s at 90% transmittance with a thickness of 200 nm. 2 Compared to low resistivity metals such as copper (p = 2.1 #~q-cm) and aluminum (p = 2.8 #s its resistivity (p = 100 p.D.-cm) is two orders of magnitude higher. Conduction mechanisms in TO and ITO limits their intrinsic conductivities to about 2.5 • 106 s m-1.3 To achieve higher conductivity of the transparent electrodes, a combined electrode scheme using a thin high conductivity metal stripe in contact with the ITO or TO forming a hybrid electrode was proposed by Hope et aL 4 Since then, there have been several reports s'6 based on this idea. In spite of their difference in structures, aluminum, which is vacuum evaporated, was always used as the metallic material due to its very low specific resistivity, ease of deposition, ready etching, and especially strong adhesion to Si, SiO2, and many other oxide substrate materials. However, it is reported that the combination suffers severe corrosion when the combined conductor is cleaned in weak alkaline solutions, which causes disconnection and device failures. 7 Furthermore, the contact resistance between aluminum and TO or ITO is quite high typically 80 ~for a contact area of 1.6 x 103 ~m 2. e At high temperatures, above 200~ which may be encountered in the fabrication process of subsequent layers such as ZnS:Mn 8 or during the device 9 operation, the TO or ITO is readily reduced by aluminum via the 6 formation of the more stable oxide, AI203. Copper (Cu) is an attractive alternative and has been investigated for applications in interconnection formation. 1~ Cu has lower resistivity than AI and is expected to be highly resistant to electromigration. ~1 In addition, Cu is less active than tin and therefore reduction of TO or ITO in contact with Cu at high temperature is less likely to occur. Usually a transition layer of Cr or Ti, which are oxygen active metals, is needed in order to use copper on such substrates. However, in this case the introduction of such interface layers w...

We have developed an etch process suitable for high resolution transparent conductive oxide patterning with high etch rates, up to 70 nm/min, and applicability to large area flat panel display substrates. It was found that the addition of small amounts of Cl2 significantly enhanced the etch rate compared to addition of pure argon but that beyond 25% Cl2 the rate tended to fall. There is a significant loading effect where the etch rate approximately doubled for exposed tin oxide areas between 80% and 10% of the substrate area. This loading sensitivity was found to increase with increasing power and decreasing Cl2 concentration. It was also observed that local changes in pattern dimensions affected the uniformity of the etch rate. A large photoresist etch rate was observed between one and three times that of the tin oxide and it decreased as the area of photoresist coverage increased. Linewidth loss, up to 4 μm at high powers, was overcome using improved ultraviolet exposure, leading to feature resolution capabilities of <5 μm. Etch rate inhomogeneity was also observed on a local scale, possibly due to redeposition of sputtered photoresist. Overetching, however, ensures rapid clearing of tin oxide islands without damage to the underlying SiO2 buffer layer.