Thin film Al2O3:TiO2 composite dielectric

Some Properties of RF Sputtered Al2 O 3 ‐ Ta2 O 5 Composite Thin Films

“…Ono and Sato (2, 3) inferred the presence of defects in various porous films, formed on high purity aluminum, from the nonuniform dissolution behavior of the barrier layers. The results obtained include the following: after the dissolution of one-third to two-thirds of the thickness of the barrier layer, the defects become detectable as fine pores or voids which penetrate to the metal substrate; the defects are not detected in films formed in oxalic acid or sulfuric acid; the volume of the voids increases with increasing forming voltage and decreases in the order of films formed in chromic acid, phosphoric acid, and in Ematal baths (4); films having a high volume of defects are easily colored by a relatively low ac voltage during electrolytic coloring (5). Although fine holes in the cell walls of porous layers are often observed, neither the shape nor the accurate location of the defects in the barrier layers of various films could be clearly defined by TEM and SEM observation.…”

“…High dielectric constant insulators are in strong demand for thin films devices such as a storage capacitor of a dynamic random access memory (DRAM) (1), a thin film electroluminescent panel (2), and a gate insulator for a thin film transistor (3). There has recently been interest in a composite insulator because of the improved dielectric properties compared with a single-constituent insulator (4,5). We previously reported that A1203-Ta205 thin films prepared by RF reactive sputtering in Ar-O2 mixed gas using A1-Ta composite metal target exhibited relatively good dielectric properties (6).…”

Electrical Properties of Al2 O 3 ‐ Ta2 O 5 Composite Dielectric Thin Films Prepared by RF Reactive Sputtering

“…The latter could short adjacent gate and source/drain regions and results from direct reaction between titanium and SiO2 or, more probably, from lateral diffusion of silicon from the polysilicon gate and single-crystal substrate into the titanium deposited on oxide. An N2 ambient has been found essential for the initial anneal in order to avoid such bridging (8,9). The outer part of the titanium film deposited on oxide becomes nitrided, and nitrogen diffuses into the remainder (10), both of which serve to prevent the lateral diffusion of silicon atoms into the tita-…”

“…Lately, there has been interest in the composite oxides because of their improved dielectric properties as compared with the single-constituent oxide (8,9).…”