Etching mechanism of barium strontium titanate (BST) thin films in CHF3/Ar plasma

Abstract

Reactive ion etching was used to etch barium strontium titanate thin films in a CHF 3 /Ar plasma. BST surfaces before and after etching were analyzed by X-ray photoelectron spectroscopy to investigate the reaction ion etching mechanism, and chemical reactions had occurred between the F plasma and the Ba, Sr and Ti metal species. Fluorides of these metals were formed and remained on the surface during the etching process. Ti was almost completely removed because the TiF 4 by-product is volatile. Minor quantities of TiF could still be detected by narrow scan X-ray photoelectron spectra, and TiF was thought to be present in the form of a metal-oxy-fluoride. These species were investigated from O1s spectra, and a fluoride-rich surface was formed during etching. BaF 2 and SrF 2 residues were difficult to remove because of their high boiling point. The etching rate was limited to 12.86 nm/min. CF polymers were not found on the surface, indicating that the removal of BaF 2 and SrF 2 was important for further etching. A 1-min Ar/15 plasma physical sputtering was carried out for every 4 min of surface etching, which effectively removed remaining surface residue. Sequential chemical reaction and sputtered etching is an effective etching method for barium strontium titanate films. barium strontium titanate, reaction ion etching, X-ray photoelectron spectroscopy, plasma Citation:Dai L P, Wang S Y, Shu P, et al. Etching mechanism of barium strontium titanate (BST) thin films in CHF 3 /Ar plasma.With the rapid development of electronics and information technology, there is a great demand for high K dielectric materials. An example is ferroelectric high-K materials [1-4] required for many microwave applications [5]. Ferroelectric thin films possessing high permittivity are of great interest for application to high-K dynamic random access memory (DRAM) cells. Barium strontium titanate (BST) thin film ferroelectric materials are promising as capacitor dielectric components in future high density DRAM devices, because of their high dielectric constant, low leakage current, low temperature coefficient in electrical processes, small dielectric loss and lack of fatigue/aging [6][7][8]. BST can potentially provide significant improvements in device performance; however, several problems need resolving to realize highly integrated DRAMs involving BST thin films. To efficiently integrate BST thin films into Si-based circuitry, an etching process for micro-patterning technology must be developed. The etching mechanism includes two major processes: ion-assisted etching reaction; and sputtering process to remove the reaction by-products. Thus, identifying by-product compositions is important for optimizing etching processes. There are several reported studies on the etching of BST thin films using chlorine and fluorine-based plasma chemistry [9][10][11][12][13][14][15][16][17]. There are also several reports investigating the properties of CF 4 /Ar plasmas both experimentally and theoretically. Unfortunately, the etching mechanism of BS...

Pressure-Dependent Etching Mechanism and Induced Dielectric Properties Variation of BZN Thin Films in SF6/Ar Plasma

“…Dry-etching processes as a micro-patterning technology are very important in integrating the BZN thin films into a Si-based circuitry. Many studies on dry-etching processes for various kinds of specimens have been reported [9][10][11][12][13][14][15][16], where various of etching parameters having effects on the surface and structure of films were involved. However, only a few studies on BZN thin films have been published [17,18].…”

Area-Selective Atomic Layer Deposition of Crystalline BaTiO3

“…BTO patterns have been defined using sacrificial SiO 2 lift-off procedures or Cl etching . However, the build-up of Ti-containing etch products on the surface , and decreasing nanofeature dimensions make monolithic integration of patterned perovskites difficult using existing techniques. A potential solution to the challenges in defining crystalline BTO patterns is bottom–up area-selective (AS) patterning.…”