Solgel derived tantalum pentoxide films as ultraviolet antireflective coatings for silicon

Abstract

A solgel process is described to produce Ta(2)O(5) films as short wavelength antireflective (AR) coatings for silicon. The AR coatings were optimized for 370 nm by controlling the acid catalyzed hydrolysis of Ta(OC(2)H(5))(5), the spin coating parameters, and the heat treatment process (rapid thermal processing (RTP) and muffle furnace). Film thickness uniformity across the wafer was better than 1%, and all the coatings tested passed the standard scotch tape test before and after heat treatment and exhibited no change in optical properties after submersion in liquid N(2). Several heat treatment protocols for densifying the films were studied. Spin coated films heat treated in a muffle furnace at 275 degrees C yielded Ta(2)O(5) AR coatings that reduced the reflectance losses from silicon at 370 nm by 86%, the reduction being within 1% of the theoretical value. Films subjected to RTP at temperatures ranging from 300 to 1000 degrees C reduced the reflectance loss in some cases by as much as 95%. The results demonstrate that spin coated solgel derived Ta(2)O(5) films subjected to a low temperature (<300 degrees C) heat treatment can form durable films suitable for near UV AR coatings for high index silicon devices, such as charge couple imagers and photovoltaic cells.

Spin coating of colloidal suspensions

“…24 regardless of the value of b (see, for example, Rehg et al, 1989). We show that the acceleration rate of the spin coater can be a factor, since it does modify the inverse power law dependence on angular velocity.…”

Prediction of new ground-state crystal structure of Ta2O5

“…The intrinsic excellent dielectric properties make Ta 2 O 5 a good candidate material to replace SiO 2 as the insulating layer for advanced electronic devices such as non-volatile memories [1][2][3][4][5] and organic transistors [6,7]. Owing to its high refractive index, Ta 2 O 5 has applications in the coating material of optical devices [8,9] and the instruments for ultraprecise measurement such as the Laser Interferometer Gravitational-wave Observatory (LIGO) [10][11][12]. In the detection and observation of gravitational waves made by LIGO [13], alternating thin layers of SiO 2 and Ta 2 O 5 (doped with TiO 2 ) serve as mirror coatings for the test masses of the detectors [10][11][12].…”

Layer-by-Layer Assembly of TaO3 Nanosheet/Polycation Composite Nanostructures: Multilayer Film, Hollow Sphere, and Its Photocatalytic Activity for Hydrogen Evolution

“…Apart from the photocatalytic activities, because of high dielectric constant, large refractive index value, as well as high chemical and thermal stability, Ta 2 O 5 films involve various applications, 9 such as for antireflective layers in optical devices, 10 dielectric layers for storage *Corresponding author. E-mail: sasaki.takayoshi@nims.go.jp.…”